1mod anchor;
   2
   3pub use anchor::{Anchor, AnchorRangeExt};
   4use anyhow::{anyhow, Result};
   5use clock::ReplicaId;
   6use collections::{BTreeMap, Bound, HashMap, HashSet};
   7use futures::{channel::mpsc, SinkExt};
   8use git::diff::DiffHunk;
   9use gpui::{AppContext, Entity, ModelContext, ModelHandle, Task};
  10pub use language::Completion;
  11use language::{
  12    char_kind,
  13    language_settings::{language_settings, LanguageSettings},
  14    AutoindentMode, Buffer, BufferChunks, BufferSnapshot, CharKind, Chunk, CursorShape,
  15    DiagnosticEntry, File, IndentSize, Language, LanguageScope, OffsetRangeExt, OffsetUtf16,
  16    Outline, OutlineItem, Point, PointUtf16, Selection, TextDimension, ToOffset as _,
  17    ToOffsetUtf16 as _, ToPoint as _, ToPointUtf16 as _, TransactionId, Unclipped,
  18};
  19use std::{
  20    borrow::Cow,
  21    cell::{Ref, RefCell},
  22    cmp, fmt,
  23    future::Future,
  24    io,
  25    iter::{self, FromIterator},
  26    mem,
  27    ops::{Range, RangeBounds, Sub},
  28    str,
  29    sync::Arc,
  30    time::{Duration, Instant},
  31};
  32use sum_tree::{Bias, Cursor, SumTree};
  33use text::{
  34    locator::Locator,
  35    subscription::{Subscription, Topic},
  36    Edit, TextSummary,
  37};
  38use theme::SyntaxTheme;
  39use util::post_inc;
  40
  41const NEWLINES: &[u8] = &[b'\n'; u8::MAX as usize];
  42
  43#[derive(Debug, Default, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
  44pub struct ExcerptId(usize);
  45
  46pub struct MultiBuffer {
  47    snapshot: RefCell<MultiBufferSnapshot>,
  48    buffers: RefCell<HashMap<u64, BufferState>>,
  49    next_excerpt_id: usize,
  50    subscriptions: Topic,
  51    singleton: bool,
  52    replica_id: ReplicaId,
  53    history: History,
  54    title: Option<String>,
  55}
  56
  57#[derive(Clone, Debug, PartialEq, Eq)]
  58pub enum Event {
  59    ExcerptsAdded {
  60        buffer: ModelHandle<Buffer>,
  61        predecessor: ExcerptId,
  62        excerpts: Vec<(ExcerptId, ExcerptRange<language::Anchor>)>,
  63    },
  64    ExcerptsRemoved {
  65        ids: Vec<ExcerptId>,
  66    },
  67    Edited,
  68    Reloaded,
  69    LanguageChanged,
  70    Reparsed,
  71    Saved,
  72    FileHandleChanged,
  73    Closed,
  74    DirtyChanged,
  75    DiagnosticsUpdated,
  76}
  77
  78#[derive(Clone)]
  79struct History {
  80    next_transaction_id: TransactionId,
  81    undo_stack: Vec<Transaction>,
  82    redo_stack: Vec<Transaction>,
  83    transaction_depth: usize,
  84    group_interval: Duration,
  85}
  86
  87#[derive(Clone)]
  88struct Transaction {
  89    id: TransactionId,
  90    buffer_transactions: HashMap<u64, text::TransactionId>,
  91    first_edit_at: Instant,
  92    last_edit_at: Instant,
  93    suppress_grouping: bool,
  94}
  95
  96pub trait ToOffset: 'static + fmt::Debug {
  97    fn to_offset(&self, snapshot: &MultiBufferSnapshot) -> usize;
  98}
  99
 100pub trait ToOffsetUtf16: 'static + fmt::Debug {
 101    fn to_offset_utf16(&self, snapshot: &MultiBufferSnapshot) -> OffsetUtf16;
 102}
 103
 104pub trait ToPoint: 'static + fmt::Debug {
 105    fn to_point(&self, snapshot: &MultiBufferSnapshot) -> Point;
 106}
 107
 108pub trait ToPointUtf16: 'static + fmt::Debug {
 109    fn to_point_utf16(&self, snapshot: &MultiBufferSnapshot) -> PointUtf16;
 110}
 111
 112struct BufferState {
 113    buffer: ModelHandle<Buffer>,
 114    last_version: clock::Global,
 115    last_parse_count: usize,
 116    last_selections_update_count: usize,
 117    last_diagnostics_update_count: usize,
 118    last_file_update_count: usize,
 119    last_git_diff_update_count: usize,
 120    excerpts: Vec<Locator>,
 121    _subscriptions: [gpui::Subscription; 2],
 122}
 123
 124#[derive(Clone, Default)]
 125pub struct MultiBufferSnapshot {
 126    singleton: bool,
 127    excerpts: SumTree<Excerpt>,
 128    excerpt_ids: SumTree<ExcerptIdMapping>,
 129    parse_count: usize,
 130    diagnostics_update_count: usize,
 131    trailing_excerpt_update_count: usize,
 132    git_diff_update_count: usize,
 133    edit_count: usize,
 134    is_dirty: bool,
 135    has_conflict: bool,
 136}
 137
 138pub struct ExcerptBoundary {
 139    pub id: ExcerptId,
 140    pub row: u32,
 141    pub buffer: BufferSnapshot,
 142    pub range: ExcerptRange<text::Anchor>,
 143    pub starts_new_buffer: bool,
 144}
 145
 146#[derive(Clone)]
 147struct Excerpt {
 148    id: ExcerptId,
 149    locator: Locator,
 150    buffer_id: u64,
 151    buffer: BufferSnapshot,
 152    range: ExcerptRange<text::Anchor>,
 153    max_buffer_row: u32,
 154    text_summary: TextSummary,
 155    has_trailing_newline: bool,
 156}
 157
 158#[derive(Clone, Debug)]
 159struct ExcerptIdMapping {
 160    id: ExcerptId,
 161    locator: Locator,
 162}
 163
 164#[derive(Clone, Debug, Eq, PartialEq)]
 165pub struct ExcerptRange<T> {
 166    pub context: Range<T>,
 167    pub primary: Option<Range<T>>,
 168}
 169
 170#[derive(Clone, Debug, Default)]
 171struct ExcerptSummary {
 172    excerpt_id: ExcerptId,
 173    excerpt_locator: Locator,
 174    max_buffer_row: u32,
 175    text: TextSummary,
 176}
 177
 178#[derive(Clone)]
 179pub struct MultiBufferRows<'a> {
 180    buffer_row_range: Range<u32>,
 181    excerpts: Cursor<'a, Excerpt, Point>,
 182}
 183
 184pub struct MultiBufferChunks<'a> {
 185    range: Range<usize>,
 186    excerpts: Cursor<'a, Excerpt, usize>,
 187    excerpt_chunks: Option<ExcerptChunks<'a>>,
 188    language_aware: bool,
 189}
 190
 191pub struct MultiBufferBytes<'a> {
 192    range: Range<usize>,
 193    excerpts: Cursor<'a, Excerpt, usize>,
 194    excerpt_bytes: Option<ExcerptBytes<'a>>,
 195    chunk: &'a [u8],
 196}
 197
 198struct ExcerptChunks<'a> {
 199    content_chunks: BufferChunks<'a>,
 200    footer_height: usize,
 201}
 202
 203struct ExcerptBytes<'a> {
 204    content_bytes: text::Bytes<'a>,
 205    footer_height: usize,
 206}
 207
 208impl MultiBuffer {
 209    pub fn new(replica_id: ReplicaId) -> Self {
 210        Self {
 211            snapshot: Default::default(),
 212            buffers: Default::default(),
 213            next_excerpt_id: 1,
 214            subscriptions: Default::default(),
 215            singleton: false,
 216            replica_id,
 217            history: History {
 218                next_transaction_id: Default::default(),
 219                undo_stack: Default::default(),
 220                redo_stack: Default::default(),
 221                transaction_depth: 0,
 222                group_interval: Duration::from_millis(300),
 223            },
 224            title: Default::default(),
 225        }
 226    }
 227
 228    pub fn clone(&self, new_cx: &mut ModelContext<Self>) -> Self {
 229        let mut buffers = HashMap::default();
 230        for (buffer_id, buffer_state) in self.buffers.borrow().iter() {
 231            buffers.insert(
 232                *buffer_id,
 233                BufferState {
 234                    buffer: buffer_state.buffer.clone(),
 235                    last_version: buffer_state.last_version.clone(),
 236                    last_parse_count: buffer_state.last_parse_count,
 237                    last_selections_update_count: buffer_state.last_selections_update_count,
 238                    last_diagnostics_update_count: buffer_state.last_diagnostics_update_count,
 239                    last_file_update_count: buffer_state.last_file_update_count,
 240                    last_git_diff_update_count: buffer_state.last_git_diff_update_count,
 241                    excerpts: buffer_state.excerpts.clone(),
 242                    _subscriptions: [
 243                        new_cx.observe(&buffer_state.buffer, |_, _, cx| cx.notify()),
 244                        new_cx.subscribe(&buffer_state.buffer, Self::on_buffer_event),
 245                    ],
 246                },
 247            );
 248        }
 249        Self {
 250            snapshot: RefCell::new(self.snapshot.borrow().clone()),
 251            buffers: RefCell::new(buffers),
 252            next_excerpt_id: 1,
 253            subscriptions: Default::default(),
 254            singleton: self.singleton,
 255            replica_id: self.replica_id,
 256            history: self.history.clone(),
 257            title: self.title.clone(),
 258        }
 259    }
 260
 261    pub fn with_title(mut self, title: String) -> Self {
 262        self.title = Some(title);
 263        self
 264    }
 265
 266    pub fn singleton(buffer: ModelHandle<Buffer>, cx: &mut ModelContext<Self>) -> Self {
 267        let mut this = Self::new(buffer.read(cx).replica_id());
 268        this.singleton = true;
 269        this.push_excerpts(
 270            buffer,
 271            [ExcerptRange {
 272                context: text::Anchor::MIN..text::Anchor::MAX,
 273                primary: None,
 274            }],
 275            cx,
 276        );
 277        this.snapshot.borrow_mut().singleton = true;
 278        this
 279    }
 280
 281    pub fn replica_id(&self) -> ReplicaId {
 282        self.replica_id
 283    }
 284
 285    pub fn snapshot(&self, cx: &AppContext) -> MultiBufferSnapshot {
 286        self.sync(cx);
 287        self.snapshot.borrow().clone()
 288    }
 289
 290    pub(crate) fn read(&self, cx: &AppContext) -> Ref<MultiBufferSnapshot> {
 291        self.sync(cx);
 292        self.snapshot.borrow()
 293    }
 294
 295    pub fn as_singleton(&self) -> Option<ModelHandle<Buffer>> {
 296        if self.singleton {
 297            return Some(
 298                self.buffers
 299                    .borrow()
 300                    .values()
 301                    .next()
 302                    .unwrap()
 303                    .buffer
 304                    .clone(),
 305            );
 306        } else {
 307            None
 308        }
 309    }
 310
 311    pub fn is_singleton(&self) -> bool {
 312        self.singleton
 313    }
 314
 315    pub fn subscribe(&mut self) -> Subscription {
 316        self.subscriptions.subscribe()
 317    }
 318
 319    pub fn is_dirty(&self, cx: &AppContext) -> bool {
 320        self.read(cx).is_dirty()
 321    }
 322
 323    pub fn has_conflict(&self, cx: &AppContext) -> bool {
 324        self.read(cx).has_conflict()
 325    }
 326
 327    // The `is_empty` signature doesn't match what clippy expects
 328    #[allow(clippy::len_without_is_empty)]
 329    pub fn len(&self, cx: &AppContext) -> usize {
 330        self.read(cx).len()
 331    }
 332
 333    pub fn is_empty(&self, cx: &AppContext) -> bool {
 334        self.len(cx) != 0
 335    }
 336
 337    pub fn symbols_containing<T: ToOffset>(
 338        &self,
 339        offset: T,
 340        theme: Option<&SyntaxTheme>,
 341        cx: &AppContext,
 342    ) -> Option<(u64, Vec<OutlineItem<Anchor>>)> {
 343        self.read(cx).symbols_containing(offset, theme)
 344    }
 345
 346    pub fn git_diff_recalc(&mut self, cx: &mut ModelContext<Self>) {
 347        let buffers = self.buffers.borrow();
 348        for buffer_state in buffers.values() {
 349            if buffer_state.buffer.read(cx).needs_git_diff_recalc() {
 350                buffer_state
 351                    .buffer
 352                    .update(cx, |buffer, cx| buffer.git_diff_recalc(cx))
 353            }
 354        }
 355    }
 356
 357    pub fn edit<I, S, T>(
 358        &mut self,
 359        edits: I,
 360        mut autoindent_mode: Option<AutoindentMode>,
 361        cx: &mut ModelContext<Self>,
 362    ) where
 363        I: IntoIterator<Item = (Range<S>, T)>,
 364        S: ToOffset,
 365        T: Into<Arc<str>>,
 366    {
 367        if self.buffers.borrow().is_empty() {
 368            return;
 369        }
 370
 371        let snapshot = self.read(cx);
 372        let edits = edits.into_iter().map(|(range, new_text)| {
 373            let mut range = range.start.to_offset(&snapshot)..range.end.to_offset(&snapshot);
 374            if range.start > range.end {
 375                mem::swap(&mut range.start, &mut range.end);
 376            }
 377            (range, new_text)
 378        });
 379
 380        if let Some(buffer) = self.as_singleton() {
 381            return buffer.update(cx, |buffer, cx| {
 382                buffer.edit(edits, autoindent_mode, cx);
 383            });
 384        }
 385
 386        let original_indent_columns = match &mut autoindent_mode {
 387            Some(AutoindentMode::Block {
 388                original_indent_columns,
 389            }) => mem::take(original_indent_columns),
 390            _ => Default::default(),
 391        };
 392
 393        struct BufferEdit {
 394            range: Range<usize>,
 395            new_text: Arc<str>,
 396            is_insertion: bool,
 397            original_indent_column: u32,
 398        }
 399        let mut buffer_edits: HashMap<u64, Vec<BufferEdit>> = Default::default();
 400        let mut cursor = snapshot.excerpts.cursor::<usize>();
 401        for (ix, (range, new_text)) in edits.enumerate() {
 402            let new_text: Arc<str> = new_text.into();
 403            let original_indent_column = original_indent_columns.get(ix).copied().unwrap_or(0);
 404            cursor.seek(&range.start, Bias::Right, &());
 405            if cursor.item().is_none() && range.start == *cursor.start() {
 406                cursor.prev(&());
 407            }
 408            let start_excerpt = cursor.item().expect("start offset out of bounds");
 409            let start_overshoot = range.start - cursor.start();
 410            let buffer_start = start_excerpt
 411                .range
 412                .context
 413                .start
 414                .to_offset(&start_excerpt.buffer)
 415                + start_overshoot;
 416
 417            cursor.seek(&range.end, Bias::Right, &());
 418            if cursor.item().is_none() && range.end == *cursor.start() {
 419                cursor.prev(&());
 420            }
 421            let end_excerpt = cursor.item().expect("end offset out of bounds");
 422            let end_overshoot = range.end - cursor.start();
 423            let buffer_end = end_excerpt
 424                .range
 425                .context
 426                .start
 427                .to_offset(&end_excerpt.buffer)
 428                + end_overshoot;
 429
 430            if start_excerpt.id == end_excerpt.id {
 431                buffer_edits
 432                    .entry(start_excerpt.buffer_id)
 433                    .or_insert(Vec::new())
 434                    .push(BufferEdit {
 435                        range: buffer_start..buffer_end,
 436                        new_text,
 437                        is_insertion: true,
 438                        original_indent_column,
 439                    });
 440            } else {
 441                let start_excerpt_range = buffer_start
 442                    ..start_excerpt
 443                        .range
 444                        .context
 445                        .end
 446                        .to_offset(&start_excerpt.buffer);
 447                let end_excerpt_range = end_excerpt
 448                    .range
 449                    .context
 450                    .start
 451                    .to_offset(&end_excerpt.buffer)
 452                    ..buffer_end;
 453                buffer_edits
 454                    .entry(start_excerpt.buffer_id)
 455                    .or_insert(Vec::new())
 456                    .push(BufferEdit {
 457                        range: start_excerpt_range,
 458                        new_text: new_text.clone(),
 459                        is_insertion: true,
 460                        original_indent_column,
 461                    });
 462                buffer_edits
 463                    .entry(end_excerpt.buffer_id)
 464                    .or_insert(Vec::new())
 465                    .push(BufferEdit {
 466                        range: end_excerpt_range,
 467                        new_text: new_text.clone(),
 468                        is_insertion: false,
 469                        original_indent_column,
 470                    });
 471
 472                cursor.seek(&range.start, Bias::Right, &());
 473                cursor.next(&());
 474                while let Some(excerpt) = cursor.item() {
 475                    if excerpt.id == end_excerpt.id {
 476                        break;
 477                    }
 478                    buffer_edits
 479                        .entry(excerpt.buffer_id)
 480                        .or_insert(Vec::new())
 481                        .push(BufferEdit {
 482                            range: excerpt.range.context.to_offset(&excerpt.buffer),
 483                            new_text: new_text.clone(),
 484                            is_insertion: false,
 485                            original_indent_column,
 486                        });
 487                    cursor.next(&());
 488                }
 489            }
 490        }
 491
 492        for (buffer_id, mut edits) in buffer_edits {
 493            edits.sort_unstable_by_key(|edit| edit.range.start);
 494            self.buffers.borrow()[&buffer_id]
 495                .buffer
 496                .update(cx, |buffer, cx| {
 497                    let mut edits = edits.into_iter().peekable();
 498                    let mut insertions = Vec::new();
 499                    let mut original_indent_columns = Vec::new();
 500                    let mut deletions = Vec::new();
 501                    let empty_str: Arc<str> = "".into();
 502                    while let Some(BufferEdit {
 503                        mut range,
 504                        new_text,
 505                        mut is_insertion,
 506                        original_indent_column,
 507                    }) = edits.next()
 508                    {
 509                        while let Some(BufferEdit {
 510                            range: next_range,
 511                            is_insertion: next_is_insertion,
 512                            ..
 513                        }) = edits.peek()
 514                        {
 515                            if range.end >= next_range.start {
 516                                range.end = cmp::max(next_range.end, range.end);
 517                                is_insertion |= *next_is_insertion;
 518                                edits.next();
 519                            } else {
 520                                break;
 521                            }
 522                        }
 523
 524                        if is_insertion {
 525                            original_indent_columns.push(original_indent_column);
 526                            insertions.push((
 527                                buffer.anchor_before(range.start)..buffer.anchor_before(range.end),
 528                                new_text.clone(),
 529                            ));
 530                        } else if !range.is_empty() {
 531                            deletions.push((
 532                                buffer.anchor_before(range.start)..buffer.anchor_before(range.end),
 533                                empty_str.clone(),
 534                            ));
 535                        }
 536                    }
 537
 538                    let deletion_autoindent_mode =
 539                        if let Some(AutoindentMode::Block { .. }) = autoindent_mode {
 540                            Some(AutoindentMode::Block {
 541                                original_indent_columns: Default::default(),
 542                            })
 543                        } else {
 544                            None
 545                        };
 546                    let insertion_autoindent_mode =
 547                        if let Some(AutoindentMode::Block { .. }) = autoindent_mode {
 548                            Some(AutoindentMode::Block {
 549                                original_indent_columns,
 550                            })
 551                        } else {
 552                            None
 553                        };
 554
 555                    buffer.edit(deletions, deletion_autoindent_mode, cx);
 556                    buffer.edit(insertions, insertion_autoindent_mode, cx);
 557                })
 558        }
 559    }
 560
 561    pub fn start_transaction(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 562        self.start_transaction_at(Instant::now(), cx)
 563    }
 564
 565    pub(crate) fn start_transaction_at(
 566        &mut self,
 567        now: Instant,
 568        cx: &mut ModelContext<Self>,
 569    ) -> Option<TransactionId> {
 570        if let Some(buffer) = self.as_singleton() {
 571            return buffer.update(cx, |buffer, _| buffer.start_transaction_at(now));
 572        }
 573
 574        for BufferState { buffer, .. } in self.buffers.borrow().values() {
 575            buffer.update(cx, |buffer, _| buffer.start_transaction_at(now));
 576        }
 577        self.history.start_transaction(now)
 578    }
 579
 580    pub fn end_transaction(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 581        self.end_transaction_at(Instant::now(), cx)
 582    }
 583
 584    pub(crate) fn end_transaction_at(
 585        &mut self,
 586        now: Instant,
 587        cx: &mut ModelContext<Self>,
 588    ) -> Option<TransactionId> {
 589        if let Some(buffer) = self.as_singleton() {
 590            return buffer.update(cx, |buffer, cx| buffer.end_transaction_at(now, cx));
 591        }
 592
 593        let mut buffer_transactions = HashMap::default();
 594        for BufferState { buffer, .. } in self.buffers.borrow().values() {
 595            if let Some(transaction_id) =
 596                buffer.update(cx, |buffer, cx| buffer.end_transaction_at(now, cx))
 597            {
 598                buffer_transactions.insert(buffer.read(cx).remote_id(), transaction_id);
 599            }
 600        }
 601
 602        if self.history.end_transaction(now, buffer_transactions) {
 603            let transaction_id = self.history.group().unwrap();
 604            Some(transaction_id)
 605        } else {
 606            None
 607        }
 608    }
 609
 610    pub fn finalize_last_transaction(&mut self, cx: &mut ModelContext<Self>) {
 611        self.history.finalize_last_transaction();
 612        for BufferState { buffer, .. } in self.buffers.borrow().values() {
 613            buffer.update(cx, |buffer, _| {
 614                buffer.finalize_last_transaction();
 615            });
 616        }
 617    }
 618
 619    pub fn push_transaction<'a, T>(&mut self, buffer_transactions: T, cx: &mut ModelContext<Self>)
 620    where
 621        T: IntoIterator<Item = (&'a ModelHandle<Buffer>, &'a language::Transaction)>,
 622    {
 623        self.history
 624            .push_transaction(buffer_transactions, Instant::now(), cx);
 625        self.history.finalize_last_transaction();
 626    }
 627
 628    pub fn group_until_transaction(
 629        &mut self,
 630        transaction_id: TransactionId,
 631        cx: &mut ModelContext<Self>,
 632    ) {
 633        if let Some(buffer) = self.as_singleton() {
 634            buffer.update(cx, |buffer, _| {
 635                buffer.group_until_transaction(transaction_id)
 636            });
 637        } else {
 638            self.history.group_until(transaction_id);
 639        }
 640    }
 641
 642    pub fn set_active_selections(
 643        &mut self,
 644        selections: &[Selection<Anchor>],
 645        line_mode: bool,
 646        cursor_shape: CursorShape,
 647        cx: &mut ModelContext<Self>,
 648    ) {
 649        let mut selections_by_buffer: HashMap<u64, Vec<Selection<text::Anchor>>> =
 650            Default::default();
 651        let snapshot = self.read(cx);
 652        let mut cursor = snapshot.excerpts.cursor::<Option<&Locator>>();
 653        for selection in selections {
 654            let start_locator = snapshot.excerpt_locator_for_id(selection.start.excerpt_id);
 655            let end_locator = snapshot.excerpt_locator_for_id(selection.end.excerpt_id);
 656
 657            cursor.seek(&Some(start_locator), Bias::Left, &());
 658            while let Some(excerpt) = cursor.item() {
 659                if excerpt.locator > *end_locator {
 660                    break;
 661                }
 662
 663                let mut start = excerpt.range.context.start;
 664                let mut end = excerpt.range.context.end;
 665                if excerpt.id == selection.start.excerpt_id {
 666                    start = selection.start.text_anchor;
 667                }
 668                if excerpt.id == selection.end.excerpt_id {
 669                    end = selection.end.text_anchor;
 670                }
 671                selections_by_buffer
 672                    .entry(excerpt.buffer_id)
 673                    .or_default()
 674                    .push(Selection {
 675                        id: selection.id,
 676                        start,
 677                        end,
 678                        reversed: selection.reversed,
 679                        goal: selection.goal,
 680                    });
 681
 682                cursor.next(&());
 683            }
 684        }
 685
 686        for (buffer_id, buffer_state) in self.buffers.borrow().iter() {
 687            if !selections_by_buffer.contains_key(buffer_id) {
 688                buffer_state
 689                    .buffer
 690                    .update(cx, |buffer, cx| buffer.remove_active_selections(cx));
 691            }
 692        }
 693
 694        for (buffer_id, mut selections) in selections_by_buffer {
 695            self.buffers.borrow()[&buffer_id]
 696                .buffer
 697                .update(cx, |buffer, cx| {
 698                    selections.sort_unstable_by(|a, b| a.start.cmp(&b.start, buffer));
 699                    let mut selections = selections.into_iter().peekable();
 700                    let merged_selections = Arc::from_iter(iter::from_fn(|| {
 701                        let mut selection = selections.next()?;
 702                        while let Some(next_selection) = selections.peek() {
 703                            if selection.end.cmp(&next_selection.start, buffer).is_ge() {
 704                                let next_selection = selections.next().unwrap();
 705                                if next_selection.end.cmp(&selection.end, buffer).is_ge() {
 706                                    selection.end = next_selection.end;
 707                                }
 708                            } else {
 709                                break;
 710                            }
 711                        }
 712                        Some(selection)
 713                    }));
 714                    buffer.set_active_selections(merged_selections, line_mode, cursor_shape, cx);
 715                });
 716        }
 717    }
 718
 719    pub fn remove_active_selections(&mut self, cx: &mut ModelContext<Self>) {
 720        for buffer in self.buffers.borrow().values() {
 721            buffer
 722                .buffer
 723                .update(cx, |buffer, cx| buffer.remove_active_selections(cx));
 724        }
 725    }
 726
 727    pub fn undo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 728        if let Some(buffer) = self.as_singleton() {
 729            return buffer.update(cx, |buffer, cx| buffer.undo(cx));
 730        }
 731
 732        while let Some(transaction) = self.history.pop_undo() {
 733            let mut undone = false;
 734            for (buffer_id, buffer_transaction_id) in &mut transaction.buffer_transactions {
 735                if let Some(BufferState { buffer, .. }) = self.buffers.borrow().get(buffer_id) {
 736                    undone |= buffer.update(cx, |buffer, cx| {
 737                        let undo_to = *buffer_transaction_id;
 738                        if let Some(entry) = buffer.peek_undo_stack() {
 739                            *buffer_transaction_id = entry.transaction_id();
 740                        }
 741                        buffer.undo_to_transaction(undo_to, cx)
 742                    });
 743                }
 744            }
 745
 746            if undone {
 747                return Some(transaction.id);
 748            }
 749        }
 750
 751        None
 752    }
 753
 754    pub fn redo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 755        if let Some(buffer) = self.as_singleton() {
 756            return buffer.update(cx, |buffer, cx| buffer.redo(cx));
 757        }
 758
 759        while let Some(transaction) = self.history.pop_redo() {
 760            let mut redone = false;
 761            for (buffer_id, buffer_transaction_id) in &mut transaction.buffer_transactions {
 762                if let Some(BufferState { buffer, .. }) = self.buffers.borrow().get(buffer_id) {
 763                    redone |= buffer.update(cx, |buffer, cx| {
 764                        let redo_to = *buffer_transaction_id;
 765                        if let Some(entry) = buffer.peek_redo_stack() {
 766                            *buffer_transaction_id = entry.transaction_id();
 767                        }
 768                        buffer.redo_to_transaction(redo_to, cx)
 769                    });
 770                }
 771            }
 772
 773            if redone {
 774                return Some(transaction.id);
 775            }
 776        }
 777
 778        None
 779    }
 780
 781    pub fn stream_excerpts_with_context_lines(
 782        &mut self,
 783        excerpts: Vec<(ModelHandle<Buffer>, Vec<Range<text::Anchor>>)>,
 784        context_line_count: u32,
 785        cx: &mut ModelContext<Self>,
 786    ) -> (Task<()>, mpsc::Receiver<Range<Anchor>>) {
 787        let (mut tx, rx) = mpsc::channel(256);
 788        let task = cx.spawn(|this, mut cx| async move {
 789            for (buffer, ranges) in excerpts {
 790                let (buffer_id, buffer_snapshot) =
 791                    buffer.read_with(&cx, |buffer, _| (buffer.remote_id(), buffer.snapshot()));
 792
 793                let mut excerpt_ranges = Vec::new();
 794                let mut range_counts = Vec::new();
 795                cx.background()
 796                    .scoped(|scope| {
 797                        scope.spawn(async {
 798                            let (ranges, counts) =
 799                                build_excerpt_ranges(&buffer_snapshot, &ranges, context_line_count);
 800                            excerpt_ranges = ranges;
 801                            range_counts = counts;
 802                        });
 803                    })
 804                    .await;
 805
 806                let mut ranges = ranges.into_iter();
 807                let mut range_counts = range_counts.into_iter();
 808                for excerpt_ranges in excerpt_ranges.chunks(100) {
 809                    let excerpt_ids = this.update(&mut cx, |this, cx| {
 810                        this.push_excerpts(buffer.clone(), excerpt_ranges.iter().cloned(), cx)
 811                    });
 812
 813                    for (excerpt_id, range_count) in
 814                        excerpt_ids.into_iter().zip(range_counts.by_ref())
 815                    {
 816                        for range in ranges.by_ref().take(range_count) {
 817                            let start = Anchor {
 818                                buffer_id: Some(buffer_id),
 819                                excerpt_id: excerpt_id.clone(),
 820                                text_anchor: range.start,
 821                            };
 822                            let end = Anchor {
 823                                buffer_id: Some(buffer_id),
 824                                excerpt_id: excerpt_id.clone(),
 825                                text_anchor: range.end,
 826                            };
 827                            if tx.send(start..end).await.is_err() {
 828                                break;
 829                            }
 830                        }
 831                    }
 832                }
 833            }
 834        });
 835        (task, rx)
 836    }
 837
 838    pub fn push_excerpts<O>(
 839        &mut self,
 840        buffer: ModelHandle<Buffer>,
 841        ranges: impl IntoIterator<Item = ExcerptRange<O>>,
 842        cx: &mut ModelContext<Self>,
 843    ) -> Vec<ExcerptId>
 844    where
 845        O: text::ToOffset,
 846    {
 847        self.insert_excerpts_after(ExcerptId::max(), buffer, ranges, cx)
 848    }
 849
 850    pub fn push_excerpts_with_context_lines<O>(
 851        &mut self,
 852        buffer: ModelHandle<Buffer>,
 853        ranges: Vec<Range<O>>,
 854        context_line_count: u32,
 855        cx: &mut ModelContext<Self>,
 856    ) -> Vec<Range<Anchor>>
 857    where
 858        O: text::ToPoint + text::ToOffset,
 859    {
 860        let buffer_id = buffer.read(cx).remote_id();
 861        let buffer_snapshot = buffer.read(cx).snapshot();
 862        let (excerpt_ranges, range_counts) =
 863            build_excerpt_ranges(&buffer_snapshot, &ranges, context_line_count);
 864
 865        let excerpt_ids = self.push_excerpts(buffer, excerpt_ranges, cx);
 866
 867        let mut anchor_ranges = Vec::new();
 868        let mut ranges = ranges.into_iter();
 869        for (excerpt_id, range_count) in excerpt_ids.into_iter().zip(range_counts.into_iter()) {
 870            anchor_ranges.extend(ranges.by_ref().take(range_count).map(|range| {
 871                let start = Anchor {
 872                    buffer_id: Some(buffer_id),
 873                    excerpt_id: excerpt_id.clone(),
 874                    text_anchor: buffer_snapshot.anchor_after(range.start),
 875                };
 876                let end = Anchor {
 877                    buffer_id: Some(buffer_id),
 878                    excerpt_id: excerpt_id.clone(),
 879                    text_anchor: buffer_snapshot.anchor_after(range.end),
 880                };
 881                start..end
 882            }))
 883        }
 884        anchor_ranges
 885    }
 886
 887    pub fn insert_excerpts_after<O>(
 888        &mut self,
 889        prev_excerpt_id: ExcerptId,
 890        buffer: ModelHandle<Buffer>,
 891        ranges: impl IntoIterator<Item = ExcerptRange<O>>,
 892        cx: &mut ModelContext<Self>,
 893    ) -> Vec<ExcerptId>
 894    where
 895        O: text::ToOffset,
 896    {
 897        let mut ids = Vec::new();
 898        let mut next_excerpt_id = self.next_excerpt_id;
 899        self.insert_excerpts_with_ids_after(
 900            prev_excerpt_id,
 901            buffer,
 902            ranges.into_iter().map(|range| {
 903                let id = ExcerptId(post_inc(&mut next_excerpt_id));
 904                ids.push(id);
 905                (id, range)
 906            }),
 907            cx,
 908        );
 909        ids
 910    }
 911
 912    pub fn insert_excerpts_with_ids_after<O>(
 913        &mut self,
 914        prev_excerpt_id: ExcerptId,
 915        buffer: ModelHandle<Buffer>,
 916        ranges: impl IntoIterator<Item = (ExcerptId, ExcerptRange<O>)>,
 917        cx: &mut ModelContext<Self>,
 918    ) where
 919        O: text::ToOffset,
 920    {
 921        assert_eq!(self.history.transaction_depth, 0);
 922        let mut ranges = ranges.into_iter().peekable();
 923        if ranges.peek().is_none() {
 924            return Default::default();
 925        }
 926
 927        self.sync(cx);
 928
 929        let buffer_id = buffer.read(cx).remote_id();
 930        let buffer_snapshot = buffer.read(cx).snapshot();
 931
 932        let mut buffers = self.buffers.borrow_mut();
 933        let buffer_state = buffers.entry(buffer_id).or_insert_with(|| BufferState {
 934            last_version: buffer_snapshot.version().clone(),
 935            last_parse_count: buffer_snapshot.parse_count(),
 936            last_selections_update_count: buffer_snapshot.selections_update_count(),
 937            last_diagnostics_update_count: buffer_snapshot.diagnostics_update_count(),
 938            last_file_update_count: buffer_snapshot.file_update_count(),
 939            last_git_diff_update_count: buffer_snapshot.git_diff_update_count(),
 940            excerpts: Default::default(),
 941            _subscriptions: [
 942                cx.observe(&buffer, |_, _, cx| cx.notify()),
 943                cx.subscribe(&buffer, Self::on_buffer_event),
 944            ],
 945            buffer: buffer.clone(),
 946        });
 947
 948        let mut snapshot = self.snapshot.borrow_mut();
 949
 950        let mut prev_locator = snapshot.excerpt_locator_for_id(prev_excerpt_id).clone();
 951        let mut new_excerpt_ids = mem::take(&mut snapshot.excerpt_ids);
 952        let mut cursor = snapshot.excerpts.cursor::<Option<&Locator>>();
 953        let mut new_excerpts = cursor.slice(&prev_locator, Bias::Right, &());
 954        prev_locator = cursor.start().unwrap_or(Locator::min_ref()).clone();
 955
 956        let edit_start = new_excerpts.summary().text.len;
 957        new_excerpts.update_last(
 958            |excerpt| {
 959                excerpt.has_trailing_newline = true;
 960            },
 961            &(),
 962        );
 963
 964        let next_locator = if let Some(excerpt) = cursor.item() {
 965            excerpt.locator.clone()
 966        } else {
 967            Locator::max()
 968        };
 969
 970        let mut excerpts = Vec::new();
 971        while let Some((id, range)) = ranges.next() {
 972            let locator = Locator::between(&prev_locator, &next_locator);
 973            if let Err(ix) = buffer_state.excerpts.binary_search(&locator) {
 974                buffer_state.excerpts.insert(ix, locator.clone());
 975            }
 976            let range = ExcerptRange {
 977                context: buffer_snapshot.anchor_before(&range.context.start)
 978                    ..buffer_snapshot.anchor_after(&range.context.end),
 979                primary: range.primary.map(|primary| {
 980                    buffer_snapshot.anchor_before(&primary.start)
 981                        ..buffer_snapshot.anchor_after(&primary.end)
 982                }),
 983            };
 984            if id.0 >= self.next_excerpt_id {
 985                self.next_excerpt_id = id.0 + 1;
 986            }
 987            excerpts.push((id, range.clone()));
 988            let excerpt = Excerpt::new(
 989                id,
 990                locator.clone(),
 991                buffer_id,
 992                buffer_snapshot.clone(),
 993                range,
 994                ranges.peek().is_some() || cursor.item().is_some(),
 995            );
 996            new_excerpts.push(excerpt, &());
 997            prev_locator = locator.clone();
 998            new_excerpt_ids.push(ExcerptIdMapping { id, locator }, &());
 999        }
1000
1001        let edit_end = new_excerpts.summary().text.len;
1002
1003        let suffix = cursor.suffix(&());
1004        let changed_trailing_excerpt = suffix.is_empty();
1005        new_excerpts.push_tree(suffix, &());
1006        drop(cursor);
1007        snapshot.excerpts = new_excerpts;
1008        snapshot.excerpt_ids = new_excerpt_ids;
1009        if changed_trailing_excerpt {
1010            snapshot.trailing_excerpt_update_count += 1;
1011        }
1012
1013        self.subscriptions.publish_mut([Edit {
1014            old: edit_start..edit_start,
1015            new: edit_start..edit_end,
1016        }]);
1017        cx.emit(Event::Edited);
1018        cx.emit(Event::ExcerptsAdded {
1019            buffer,
1020            predecessor: prev_excerpt_id,
1021            excerpts,
1022        });
1023        cx.notify();
1024    }
1025
1026    pub fn clear(&mut self, cx: &mut ModelContext<Self>) {
1027        self.sync(cx);
1028        let ids = self.excerpt_ids();
1029        self.buffers.borrow_mut().clear();
1030        let mut snapshot = self.snapshot.borrow_mut();
1031        let prev_len = snapshot.len();
1032        snapshot.excerpts = Default::default();
1033        snapshot.trailing_excerpt_update_count += 1;
1034        snapshot.is_dirty = false;
1035        snapshot.has_conflict = false;
1036
1037        self.subscriptions.publish_mut([Edit {
1038            old: 0..prev_len,
1039            new: 0..0,
1040        }]);
1041        cx.emit(Event::Edited);
1042        cx.emit(Event::ExcerptsRemoved { ids });
1043        cx.notify();
1044    }
1045
1046    pub fn excerpts_for_buffer(
1047        &self,
1048        buffer: &ModelHandle<Buffer>,
1049        cx: &AppContext,
1050    ) -> Vec<(ExcerptId, ExcerptRange<text::Anchor>)> {
1051        let mut excerpts = Vec::new();
1052        let snapshot = self.read(cx);
1053        let buffers = self.buffers.borrow();
1054        let mut cursor = snapshot.excerpts.cursor::<Option<&Locator>>();
1055        for locator in buffers
1056            .get(&buffer.read(cx).remote_id())
1057            .map(|state| &state.excerpts)
1058            .into_iter()
1059            .flatten()
1060        {
1061            cursor.seek_forward(&Some(locator), Bias::Left, &());
1062            if let Some(excerpt) = cursor.item() {
1063                if excerpt.locator == *locator {
1064                    excerpts.push((excerpt.id.clone(), excerpt.range.clone()));
1065                }
1066            }
1067        }
1068
1069        excerpts
1070    }
1071
1072    pub fn excerpt_ids(&self) -> Vec<ExcerptId> {
1073        self.snapshot
1074            .borrow()
1075            .excerpts
1076            .iter()
1077            .map(|entry| entry.id)
1078            .collect()
1079    }
1080
1081    pub fn excerpt_containing(
1082        &self,
1083        position: impl ToOffset,
1084        cx: &AppContext,
1085    ) -> Option<(ExcerptId, ModelHandle<Buffer>, Range<text::Anchor>)> {
1086        let snapshot = self.read(cx);
1087        let position = position.to_offset(&snapshot);
1088
1089        let mut cursor = snapshot.excerpts.cursor::<usize>();
1090        cursor.seek(&position, Bias::Right, &());
1091        cursor
1092            .item()
1093            .or_else(|| snapshot.excerpts.last())
1094            .map(|excerpt| {
1095                (
1096                    excerpt.id.clone(),
1097                    self.buffers
1098                        .borrow()
1099                        .get(&excerpt.buffer_id)
1100                        .unwrap()
1101                        .buffer
1102                        .clone(),
1103                    excerpt.range.context.clone(),
1104                )
1105            })
1106    }
1107
1108    // If point is at the end of the buffer, the last excerpt is returned
1109    pub fn point_to_buffer_offset<T: ToOffset>(
1110        &self,
1111        point: T,
1112        cx: &AppContext,
1113    ) -> Option<(ModelHandle<Buffer>, usize)> {
1114        let snapshot = self.read(cx);
1115        let offset = point.to_offset(&snapshot);
1116        let mut cursor = snapshot.excerpts.cursor::<usize>();
1117        cursor.seek(&offset, Bias::Right, &());
1118        if cursor.item().is_none() {
1119            cursor.prev(&());
1120        }
1121
1122        cursor.item().map(|excerpt| {
1123            let excerpt_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
1124            let buffer_point = excerpt_start + offset - *cursor.start();
1125            let buffer = self.buffers.borrow()[&excerpt.buffer_id].buffer.clone();
1126
1127            (buffer, buffer_point)
1128        })
1129    }
1130
1131    pub fn range_to_buffer_ranges<T: ToOffset>(
1132        &self,
1133        range: Range<T>,
1134        cx: &AppContext,
1135    ) -> Vec<(ModelHandle<Buffer>, Range<usize>)> {
1136        let snapshot = self.read(cx);
1137        let start = range.start.to_offset(&snapshot);
1138        let end = range.end.to_offset(&snapshot);
1139
1140        let mut result = Vec::new();
1141        let mut cursor = snapshot.excerpts.cursor::<usize>();
1142        cursor.seek(&start, Bias::Right, &());
1143        while let Some(excerpt) = cursor.item() {
1144            if *cursor.start() > end {
1145                break;
1146            }
1147
1148            let mut end_before_newline = cursor.end(&());
1149            if excerpt.has_trailing_newline {
1150                end_before_newline -= 1;
1151            }
1152            let excerpt_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
1153            let start = excerpt_start + (cmp::max(start, *cursor.start()) - *cursor.start());
1154            let end = excerpt_start + (cmp::min(end, end_before_newline) - *cursor.start());
1155            let buffer = self.buffers.borrow()[&excerpt.buffer_id].buffer.clone();
1156            result.push((buffer, start..end));
1157            cursor.next(&());
1158        }
1159
1160        result
1161    }
1162
1163    pub fn remove_excerpts(
1164        &mut self,
1165        excerpt_ids: impl IntoIterator<Item = ExcerptId>,
1166        cx: &mut ModelContext<Self>,
1167    ) {
1168        self.sync(cx);
1169        let ids = excerpt_ids.into_iter().collect::<Vec<_>>();
1170
1171        let mut buffers = self.buffers.borrow_mut();
1172        let mut snapshot = self.snapshot.borrow_mut();
1173        let mut new_excerpts = SumTree::new();
1174        let mut cursor = snapshot.excerpts.cursor::<(Option<&Locator>, usize)>();
1175        let mut edits = Vec::new();
1176        let mut excerpt_ids = ids.iter().copied().peekable();
1177
1178        while let Some(excerpt_id) = excerpt_ids.next() {
1179            // Seek to the next excerpt to remove, preserving any preceding excerpts.
1180            let locator = snapshot.excerpt_locator_for_id(excerpt_id);
1181            new_excerpts.push_tree(cursor.slice(&Some(locator), Bias::Left, &()), &());
1182
1183            if let Some(mut excerpt) = cursor.item() {
1184                if excerpt.id != excerpt_id {
1185                    continue;
1186                }
1187                let mut old_start = cursor.start().1;
1188
1189                // Skip over the removed excerpt.
1190                'remove_excerpts: loop {
1191                    if let Some(buffer_state) = buffers.get_mut(&excerpt.buffer_id) {
1192                        buffer_state.excerpts.retain(|l| l != &excerpt.locator);
1193                        if buffer_state.excerpts.is_empty() {
1194                            buffers.remove(&excerpt.buffer_id);
1195                        }
1196                    }
1197                    cursor.next(&());
1198
1199                    // Skip over any subsequent excerpts that are also removed.
1200                    while let Some(&next_excerpt_id) = excerpt_ids.peek() {
1201                        let next_locator = snapshot.excerpt_locator_for_id(next_excerpt_id);
1202                        if let Some(next_excerpt) = cursor.item() {
1203                            if next_excerpt.locator == *next_locator {
1204                                excerpt_ids.next();
1205                                excerpt = next_excerpt;
1206                                continue 'remove_excerpts;
1207                            }
1208                        }
1209                        break;
1210                    }
1211
1212                    break;
1213                }
1214
1215                // When removing the last excerpt, remove the trailing newline from
1216                // the previous excerpt.
1217                if cursor.item().is_none() && old_start > 0 {
1218                    old_start -= 1;
1219                    new_excerpts.update_last(|e| e.has_trailing_newline = false, &());
1220                }
1221
1222                // Push an edit for the removal of this run of excerpts.
1223                let old_end = cursor.start().1;
1224                let new_start = new_excerpts.summary().text.len;
1225                edits.push(Edit {
1226                    old: old_start..old_end,
1227                    new: new_start..new_start,
1228                });
1229            }
1230        }
1231        let suffix = cursor.suffix(&());
1232        let changed_trailing_excerpt = suffix.is_empty();
1233        new_excerpts.push_tree(suffix, &());
1234        drop(cursor);
1235        snapshot.excerpts = new_excerpts;
1236
1237        if changed_trailing_excerpt {
1238            snapshot.trailing_excerpt_update_count += 1;
1239        }
1240
1241        self.subscriptions.publish_mut(edits);
1242        cx.emit(Event::Edited);
1243        cx.emit(Event::ExcerptsRemoved { ids });
1244        cx.notify();
1245    }
1246
1247    pub fn wait_for_anchors<'a>(
1248        &self,
1249        anchors: impl 'a + Iterator<Item = Anchor>,
1250        cx: &mut ModelContext<Self>,
1251    ) -> impl 'static + Future<Output = Result<()>> {
1252        let borrow = self.buffers.borrow();
1253        let mut error = None;
1254        let mut futures = Vec::new();
1255        for anchor in anchors {
1256            if let Some(buffer_id) = anchor.buffer_id {
1257                if let Some(buffer) = borrow.get(&buffer_id) {
1258                    buffer.buffer.update(cx, |buffer, _| {
1259                        futures.push(buffer.wait_for_anchors([anchor.text_anchor]))
1260                    });
1261                } else {
1262                    error = Some(anyhow!(
1263                        "buffer {buffer_id} is not part of this multi-buffer"
1264                    ));
1265                    break;
1266                }
1267            }
1268        }
1269        async move {
1270            if let Some(error) = error {
1271                Err(error)?;
1272            }
1273            for future in futures {
1274                future.await?;
1275            }
1276            Ok(())
1277        }
1278    }
1279
1280    pub fn text_anchor_for_position<T: ToOffset>(
1281        &self,
1282        position: T,
1283        cx: &AppContext,
1284    ) -> Option<(ModelHandle<Buffer>, language::Anchor)> {
1285        let snapshot = self.read(cx);
1286        let anchor = snapshot.anchor_before(position);
1287        let buffer = self
1288            .buffers
1289            .borrow()
1290            .get(&anchor.buffer_id?)?
1291            .buffer
1292            .clone();
1293        Some((buffer, anchor.text_anchor))
1294    }
1295
1296    fn on_buffer_event(
1297        &mut self,
1298        _: ModelHandle<Buffer>,
1299        event: &language::Event,
1300        cx: &mut ModelContext<Self>,
1301    ) {
1302        cx.emit(match event {
1303            language::Event::Edited => Event::Edited,
1304            language::Event::DirtyChanged => Event::DirtyChanged,
1305            language::Event::Saved => Event::Saved,
1306            language::Event::FileHandleChanged => Event::FileHandleChanged,
1307            language::Event::Reloaded => Event::Reloaded,
1308            language::Event::LanguageChanged => Event::LanguageChanged,
1309            language::Event::Reparsed => Event::Reparsed,
1310            language::Event::DiagnosticsUpdated => Event::DiagnosticsUpdated,
1311            language::Event::Closed => Event::Closed,
1312
1313            //
1314            language::Event::Operation(_) => return,
1315        });
1316    }
1317
1318    pub fn all_buffers(&self) -> HashSet<ModelHandle<Buffer>> {
1319        self.buffers
1320            .borrow()
1321            .values()
1322            .map(|state| state.buffer.clone())
1323            .collect()
1324    }
1325
1326    pub fn buffer(&self, buffer_id: u64) -> Option<ModelHandle<Buffer>> {
1327        self.buffers
1328            .borrow()
1329            .get(&buffer_id)
1330            .map(|state| state.buffer.clone())
1331    }
1332
1333    pub fn is_completion_trigger<T>(&self, position: T, text: &str, cx: &AppContext) -> bool
1334    where
1335        T: ToOffset,
1336    {
1337        let mut chars = text.chars();
1338        let char = if let Some(char) = chars.next() {
1339            char
1340        } else {
1341            return false;
1342        };
1343        if chars.next().is_some() {
1344            return false;
1345        }
1346
1347        if char.is_alphanumeric() || char == '_' {
1348            return true;
1349        }
1350
1351        let snapshot = self.snapshot(cx);
1352        let anchor = snapshot.anchor_before(position);
1353        anchor
1354            .buffer_id
1355            .and_then(|buffer_id| {
1356                let buffer = self.buffers.borrow().get(&buffer_id)?.buffer.clone();
1357                Some(
1358                    buffer
1359                        .read(cx)
1360                        .completion_triggers()
1361                        .iter()
1362                        .any(|string| string == text),
1363                )
1364            })
1365            .unwrap_or(false)
1366    }
1367
1368    pub fn language_at<'a, T: ToOffset>(
1369        &self,
1370        point: T,
1371        cx: &'a AppContext,
1372    ) -> Option<Arc<Language>> {
1373        self.point_to_buffer_offset(point, cx)
1374            .and_then(|(buffer, offset)| buffer.read(cx).language_at(offset))
1375    }
1376
1377    pub fn settings_at<'a, T: ToOffset>(
1378        &self,
1379        point: T,
1380        cx: &'a AppContext,
1381    ) -> &'a LanguageSettings {
1382        let language = self.language_at(point, cx);
1383        language_settings(None, language.map(|l| l.name()).as_deref(), cx)
1384    }
1385
1386    pub fn for_each_buffer(&self, mut f: impl FnMut(&ModelHandle<Buffer>)) {
1387        self.buffers
1388            .borrow()
1389            .values()
1390            .for_each(|state| f(&state.buffer))
1391    }
1392
1393    pub fn title<'a>(&'a self, cx: &'a AppContext) -> Cow<'a, str> {
1394        if let Some(title) = self.title.as_ref() {
1395            return title.into();
1396        }
1397
1398        if let Some(buffer) = self.as_singleton() {
1399            if let Some(file) = buffer.read(cx).file() {
1400                return file.file_name(cx).to_string_lossy();
1401            }
1402        }
1403
1404        "untitled".into()
1405    }
1406
1407    #[cfg(test)]
1408    pub fn is_parsing(&self, cx: &AppContext) -> bool {
1409        self.as_singleton().unwrap().read(cx).is_parsing()
1410    }
1411
1412    fn sync(&self, cx: &AppContext) {
1413        let mut snapshot = self.snapshot.borrow_mut();
1414        let mut excerpts_to_edit = Vec::new();
1415        let mut reparsed = false;
1416        let mut diagnostics_updated = false;
1417        let mut git_diff_updated = false;
1418        let mut is_dirty = false;
1419        let mut has_conflict = false;
1420        let mut edited = false;
1421        let mut buffers = self.buffers.borrow_mut();
1422        for buffer_state in buffers.values_mut() {
1423            let buffer = buffer_state.buffer.read(cx);
1424            let version = buffer.version();
1425            let parse_count = buffer.parse_count();
1426            let selections_update_count = buffer.selections_update_count();
1427            let diagnostics_update_count = buffer.diagnostics_update_count();
1428            let file_update_count = buffer.file_update_count();
1429            let git_diff_update_count = buffer.git_diff_update_count();
1430
1431            let buffer_edited = version.changed_since(&buffer_state.last_version);
1432            let buffer_reparsed = parse_count > buffer_state.last_parse_count;
1433            let buffer_selections_updated =
1434                selections_update_count > buffer_state.last_selections_update_count;
1435            let buffer_diagnostics_updated =
1436                diagnostics_update_count > buffer_state.last_diagnostics_update_count;
1437            let buffer_file_updated = file_update_count > buffer_state.last_file_update_count;
1438            let buffer_git_diff_updated =
1439                git_diff_update_count > buffer_state.last_git_diff_update_count;
1440            if buffer_edited
1441                || buffer_reparsed
1442                || buffer_selections_updated
1443                || buffer_diagnostics_updated
1444                || buffer_file_updated
1445                || buffer_git_diff_updated
1446            {
1447                buffer_state.last_version = version;
1448                buffer_state.last_parse_count = parse_count;
1449                buffer_state.last_selections_update_count = selections_update_count;
1450                buffer_state.last_diagnostics_update_count = diagnostics_update_count;
1451                buffer_state.last_file_update_count = file_update_count;
1452                buffer_state.last_git_diff_update_count = git_diff_update_count;
1453                excerpts_to_edit.extend(
1454                    buffer_state
1455                        .excerpts
1456                        .iter()
1457                        .map(|locator| (locator, buffer_state.buffer.clone(), buffer_edited)),
1458                );
1459            }
1460
1461            edited |= buffer_edited;
1462            reparsed |= buffer_reparsed;
1463            diagnostics_updated |= buffer_diagnostics_updated;
1464            git_diff_updated |= buffer_git_diff_updated;
1465            is_dirty |= buffer.is_dirty();
1466            has_conflict |= buffer.has_conflict();
1467        }
1468        if edited {
1469            snapshot.edit_count += 1;
1470        }
1471        if reparsed {
1472            snapshot.parse_count += 1;
1473        }
1474        if diagnostics_updated {
1475            snapshot.diagnostics_update_count += 1;
1476        }
1477        if git_diff_updated {
1478            snapshot.git_diff_update_count += 1;
1479        }
1480        snapshot.is_dirty = is_dirty;
1481        snapshot.has_conflict = has_conflict;
1482
1483        excerpts_to_edit.sort_unstable_by_key(|(locator, _, _)| *locator);
1484
1485        let mut edits = Vec::new();
1486        let mut new_excerpts = SumTree::new();
1487        let mut cursor = snapshot.excerpts.cursor::<(Option<&Locator>, usize)>();
1488
1489        for (locator, buffer, buffer_edited) in excerpts_to_edit {
1490            new_excerpts.push_tree(cursor.slice(&Some(locator), Bias::Left, &()), &());
1491            let old_excerpt = cursor.item().unwrap();
1492            let buffer = buffer.read(cx);
1493            let buffer_id = buffer.remote_id();
1494
1495            let mut new_excerpt;
1496            if buffer_edited {
1497                edits.extend(
1498                    buffer
1499                        .edits_since_in_range::<usize>(
1500                            old_excerpt.buffer.version(),
1501                            old_excerpt.range.context.clone(),
1502                        )
1503                        .map(|mut edit| {
1504                            let excerpt_old_start = cursor.start().1;
1505                            let excerpt_new_start = new_excerpts.summary().text.len;
1506                            edit.old.start += excerpt_old_start;
1507                            edit.old.end += excerpt_old_start;
1508                            edit.new.start += excerpt_new_start;
1509                            edit.new.end += excerpt_new_start;
1510                            edit
1511                        }),
1512                );
1513
1514                new_excerpt = Excerpt::new(
1515                    old_excerpt.id,
1516                    locator.clone(),
1517                    buffer_id,
1518                    buffer.snapshot(),
1519                    old_excerpt.range.clone(),
1520                    old_excerpt.has_trailing_newline,
1521                );
1522            } else {
1523                new_excerpt = old_excerpt.clone();
1524                new_excerpt.buffer = buffer.snapshot();
1525            }
1526
1527            new_excerpts.push(new_excerpt, &());
1528            cursor.next(&());
1529        }
1530        new_excerpts.push_tree(cursor.suffix(&()), &());
1531
1532        drop(cursor);
1533        snapshot.excerpts = new_excerpts;
1534
1535        self.subscriptions.publish(edits);
1536    }
1537}
1538
1539#[cfg(any(test, feature = "test-support"))]
1540impl MultiBuffer {
1541    pub fn build_simple(text: &str, cx: &mut gpui::AppContext) -> ModelHandle<Self> {
1542        let buffer = cx.add_model(|cx| Buffer::new(0, text, cx));
1543        cx.add_model(|cx| Self::singleton(buffer, cx))
1544    }
1545
1546    pub fn build_random(rng: &mut impl rand::Rng, cx: &mut gpui::AppContext) -> ModelHandle<Self> {
1547        cx.add_model(|cx| {
1548            let mut multibuffer = MultiBuffer::new(0);
1549            let mutation_count = rng.gen_range(1..=5);
1550            multibuffer.randomly_edit_excerpts(rng, mutation_count, cx);
1551            multibuffer
1552        })
1553    }
1554
1555    pub fn randomly_edit(
1556        &mut self,
1557        rng: &mut impl rand::Rng,
1558        edit_count: usize,
1559        cx: &mut ModelContext<Self>,
1560    ) {
1561        use util::RandomCharIter;
1562
1563        let snapshot = self.read(cx);
1564        let mut edits: Vec<(Range<usize>, Arc<str>)> = Vec::new();
1565        let mut last_end = None;
1566        for _ in 0..edit_count {
1567            if last_end.map_or(false, |last_end| last_end >= snapshot.len()) {
1568                break;
1569            }
1570
1571            let new_start = last_end.map_or(0, |last_end| last_end + 1);
1572            let end = snapshot.clip_offset(rng.gen_range(new_start..=snapshot.len()), Bias::Right);
1573            let start = snapshot.clip_offset(rng.gen_range(new_start..=end), Bias::Right);
1574            last_end = Some(end);
1575
1576            let mut range = start..end;
1577            if rng.gen_bool(0.2) {
1578                mem::swap(&mut range.start, &mut range.end);
1579            }
1580
1581            let new_text_len = rng.gen_range(0..10);
1582            let new_text: String = RandomCharIter::new(&mut *rng).take(new_text_len).collect();
1583
1584            edits.push((range, new_text.into()));
1585        }
1586        log::info!("mutating multi-buffer with {:?}", edits);
1587        drop(snapshot);
1588
1589        self.edit(edits, None, cx);
1590    }
1591
1592    pub fn randomly_edit_excerpts(
1593        &mut self,
1594        rng: &mut impl rand::Rng,
1595        mutation_count: usize,
1596        cx: &mut ModelContext<Self>,
1597    ) {
1598        use rand::prelude::*;
1599        use std::env;
1600        use util::RandomCharIter;
1601
1602        let max_excerpts = env::var("MAX_EXCERPTS")
1603            .map(|i| i.parse().expect("invalid `MAX_EXCERPTS` variable"))
1604            .unwrap_or(5);
1605
1606        let mut buffers = Vec::new();
1607        for _ in 0..mutation_count {
1608            if rng.gen_bool(0.05) {
1609                log::info!("Clearing multi-buffer");
1610                self.clear(cx);
1611                continue;
1612            }
1613
1614            let excerpt_ids = self.excerpt_ids();
1615            if excerpt_ids.is_empty() || (rng.gen() && excerpt_ids.len() < max_excerpts) {
1616                let buffer_handle = if rng.gen() || self.buffers.borrow().is_empty() {
1617                    let text = RandomCharIter::new(&mut *rng).take(10).collect::<String>();
1618                    buffers.push(cx.add_model(|cx| Buffer::new(0, text, cx)));
1619                    let buffer = buffers.last().unwrap().read(cx);
1620                    log::info!(
1621                        "Creating new buffer {} with text: {:?}",
1622                        buffer.remote_id(),
1623                        buffer.text()
1624                    );
1625                    buffers.last().unwrap().clone()
1626                } else {
1627                    self.buffers
1628                        .borrow()
1629                        .values()
1630                        .choose(rng)
1631                        .unwrap()
1632                        .buffer
1633                        .clone()
1634                };
1635
1636                let buffer = buffer_handle.read(cx);
1637                let buffer_text = buffer.text();
1638                let ranges = (0..rng.gen_range(0..5))
1639                    .map(|_| {
1640                        let end_ix =
1641                            buffer.clip_offset(rng.gen_range(0..=buffer.len()), Bias::Right);
1642                        let start_ix = buffer.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
1643                        ExcerptRange {
1644                            context: start_ix..end_ix,
1645                            primary: None,
1646                        }
1647                    })
1648                    .collect::<Vec<_>>();
1649                log::info!(
1650                    "Inserting excerpts from buffer {} and ranges {:?}: {:?}",
1651                    buffer_handle.read(cx).remote_id(),
1652                    ranges.iter().map(|r| &r.context).collect::<Vec<_>>(),
1653                    ranges
1654                        .iter()
1655                        .map(|r| &buffer_text[r.context.clone()])
1656                        .collect::<Vec<_>>()
1657                );
1658
1659                let excerpt_id = self.push_excerpts(buffer_handle.clone(), ranges, cx);
1660                log::info!("Inserted with ids: {:?}", excerpt_id);
1661            } else {
1662                let remove_count = rng.gen_range(1..=excerpt_ids.len());
1663                let mut excerpts_to_remove = excerpt_ids
1664                    .choose_multiple(rng, remove_count)
1665                    .cloned()
1666                    .collect::<Vec<_>>();
1667                let snapshot = self.snapshot.borrow();
1668                excerpts_to_remove.sort_unstable_by(|a, b| a.cmp(b, &*snapshot));
1669                drop(snapshot);
1670                log::info!("Removing excerpts {:?}", excerpts_to_remove);
1671                self.remove_excerpts(excerpts_to_remove, cx);
1672            }
1673        }
1674    }
1675
1676    pub fn randomly_mutate(
1677        &mut self,
1678        rng: &mut impl rand::Rng,
1679        mutation_count: usize,
1680        cx: &mut ModelContext<Self>,
1681    ) {
1682        use rand::prelude::*;
1683
1684        if rng.gen_bool(0.7) || self.singleton {
1685            let buffer = self
1686                .buffers
1687                .borrow()
1688                .values()
1689                .choose(rng)
1690                .map(|state| state.buffer.clone());
1691
1692            if let Some(buffer) = buffer {
1693                buffer.update(cx, |buffer, cx| {
1694                    if rng.gen() {
1695                        buffer.randomly_edit(rng, mutation_count, cx);
1696                    } else {
1697                        buffer.randomly_undo_redo(rng, cx);
1698                    }
1699                });
1700            } else {
1701                self.randomly_edit(rng, mutation_count, cx);
1702            }
1703        } else {
1704            self.randomly_edit_excerpts(rng, mutation_count, cx);
1705        }
1706
1707        self.check_invariants(cx);
1708    }
1709
1710    fn check_invariants(&self, cx: &mut ModelContext<Self>) {
1711        let snapshot = self.read(cx);
1712        let excerpts = snapshot.excerpts.items(&());
1713        let excerpt_ids = snapshot.excerpt_ids.items(&());
1714
1715        for (ix, excerpt) in excerpts.iter().enumerate() {
1716            if ix == 0 {
1717                if excerpt.locator <= Locator::min() {
1718                    panic!("invalid first excerpt locator {:?}", excerpt.locator);
1719                }
1720            } else {
1721                if excerpt.locator <= excerpts[ix - 1].locator {
1722                    panic!("excerpts are out-of-order: {:?}", excerpts);
1723                }
1724            }
1725        }
1726
1727        for (ix, entry) in excerpt_ids.iter().enumerate() {
1728            if ix == 0 {
1729                if entry.id.cmp(&ExcerptId::min(), &*snapshot).is_le() {
1730                    panic!("invalid first excerpt id {:?}", entry.id);
1731                }
1732            } else {
1733                if entry.id <= excerpt_ids[ix - 1].id {
1734                    panic!("excerpt ids are out-of-order: {:?}", excerpt_ids);
1735                }
1736            }
1737        }
1738    }
1739}
1740
1741impl Entity for MultiBuffer {
1742    type Event = Event;
1743}
1744
1745impl MultiBufferSnapshot {
1746    pub fn text(&self) -> String {
1747        self.chunks(0..self.len(), false)
1748            .map(|chunk| chunk.text)
1749            .collect()
1750    }
1751
1752    pub fn reversed_chars_at<T: ToOffset>(&self, position: T) -> impl Iterator<Item = char> + '_ {
1753        let mut offset = position.to_offset(self);
1754        let mut cursor = self.excerpts.cursor::<usize>();
1755        cursor.seek(&offset, Bias::Left, &());
1756        let mut excerpt_chunks = cursor.item().map(|excerpt| {
1757            let end_before_footer = cursor.start() + excerpt.text_summary.len;
1758            let start = excerpt.range.context.start.to_offset(&excerpt.buffer);
1759            let end = start + (cmp::min(offset, end_before_footer) - cursor.start());
1760            excerpt.buffer.reversed_chunks_in_range(start..end)
1761        });
1762        iter::from_fn(move || {
1763            if offset == *cursor.start() {
1764                cursor.prev(&());
1765                let excerpt = cursor.item()?;
1766                excerpt_chunks = Some(
1767                    excerpt
1768                        .buffer
1769                        .reversed_chunks_in_range(excerpt.range.context.clone()),
1770                );
1771            }
1772
1773            let excerpt = cursor.item().unwrap();
1774            if offset == cursor.end(&()) && excerpt.has_trailing_newline {
1775                offset -= 1;
1776                Some("\n")
1777            } else {
1778                let chunk = excerpt_chunks.as_mut().unwrap().next().unwrap();
1779                offset -= chunk.len();
1780                Some(chunk)
1781            }
1782        })
1783        .flat_map(|c| c.chars().rev())
1784    }
1785
1786    pub fn chars_at<T: ToOffset>(&self, position: T) -> impl Iterator<Item = char> + '_ {
1787        let offset = position.to_offset(self);
1788        self.text_for_range(offset..self.len())
1789            .flat_map(|chunk| chunk.chars())
1790    }
1791
1792    pub fn text_for_range<T: ToOffset>(&self, range: Range<T>) -> impl Iterator<Item = &str> + '_ {
1793        self.chunks(range, false).map(|chunk| chunk.text)
1794    }
1795
1796    pub fn is_line_blank(&self, row: u32) -> bool {
1797        self.text_for_range(Point::new(row, 0)..Point::new(row, self.line_len(row)))
1798            .all(|chunk| chunk.matches(|c: char| !c.is_whitespace()).next().is_none())
1799    }
1800
1801    pub fn contains_str_at<T>(&self, position: T, needle: &str) -> bool
1802    where
1803        T: ToOffset,
1804    {
1805        let position = position.to_offset(self);
1806        position == self.clip_offset(position, Bias::Left)
1807            && self
1808                .bytes_in_range(position..self.len())
1809                .flatten()
1810                .copied()
1811                .take(needle.len())
1812                .eq(needle.bytes())
1813    }
1814
1815    pub fn surrounding_word<T: ToOffset>(&self, start: T) -> (Range<usize>, Option<CharKind>) {
1816        let mut start = start.to_offset(self);
1817        let mut end = start;
1818        let mut next_chars = self.chars_at(start).peekable();
1819        let mut prev_chars = self.reversed_chars_at(start).peekable();
1820        let word_kind = cmp::max(
1821            prev_chars.peek().copied().map(char_kind),
1822            next_chars.peek().copied().map(char_kind),
1823        );
1824
1825        for ch in prev_chars {
1826            if Some(char_kind(ch)) == word_kind && ch != '\n' {
1827                start -= ch.len_utf8();
1828            } else {
1829                break;
1830            }
1831        }
1832
1833        for ch in next_chars {
1834            if Some(char_kind(ch)) == word_kind && ch != '\n' {
1835                end += ch.len_utf8();
1836            } else {
1837                break;
1838            }
1839        }
1840
1841        (start..end, word_kind)
1842    }
1843
1844    pub fn as_singleton(&self) -> Option<(&ExcerptId, u64, &BufferSnapshot)> {
1845        if self.singleton {
1846            self.excerpts
1847                .iter()
1848                .next()
1849                .map(|e| (&e.id, e.buffer_id, &e.buffer))
1850        } else {
1851            None
1852        }
1853    }
1854
1855    pub fn len(&self) -> usize {
1856        self.excerpts.summary().text.len
1857    }
1858
1859    pub fn is_empty(&self) -> bool {
1860        self.excerpts.summary().text.len == 0
1861    }
1862
1863    pub fn max_buffer_row(&self) -> u32 {
1864        self.excerpts.summary().max_buffer_row
1865    }
1866
1867    pub fn clip_offset(&self, offset: usize, bias: Bias) -> usize {
1868        if let Some((_, _, buffer)) = self.as_singleton() {
1869            return buffer.clip_offset(offset, bias);
1870        }
1871
1872        let mut cursor = self.excerpts.cursor::<usize>();
1873        cursor.seek(&offset, Bias::Right, &());
1874        let overshoot = if let Some(excerpt) = cursor.item() {
1875            let excerpt_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
1876            let buffer_offset = excerpt
1877                .buffer
1878                .clip_offset(excerpt_start + (offset - cursor.start()), bias);
1879            buffer_offset.saturating_sub(excerpt_start)
1880        } else {
1881            0
1882        };
1883        cursor.start() + overshoot
1884    }
1885
1886    pub fn clip_point(&self, point: Point, bias: Bias) -> Point {
1887        if let Some((_, _, buffer)) = self.as_singleton() {
1888            return buffer.clip_point(point, bias);
1889        }
1890
1891        let mut cursor = self.excerpts.cursor::<Point>();
1892        cursor.seek(&point, Bias::Right, &());
1893        let overshoot = if let Some(excerpt) = cursor.item() {
1894            let excerpt_start = excerpt.range.context.start.to_point(&excerpt.buffer);
1895            let buffer_point = excerpt
1896                .buffer
1897                .clip_point(excerpt_start + (point - cursor.start()), bias);
1898            buffer_point.saturating_sub(excerpt_start)
1899        } else {
1900            Point::zero()
1901        };
1902        *cursor.start() + overshoot
1903    }
1904
1905    pub fn clip_offset_utf16(&self, offset: OffsetUtf16, bias: Bias) -> OffsetUtf16 {
1906        if let Some((_, _, buffer)) = self.as_singleton() {
1907            return buffer.clip_offset_utf16(offset, bias);
1908        }
1909
1910        let mut cursor = self.excerpts.cursor::<OffsetUtf16>();
1911        cursor.seek(&offset, Bias::Right, &());
1912        let overshoot = if let Some(excerpt) = cursor.item() {
1913            let excerpt_start = excerpt.range.context.start.to_offset_utf16(&excerpt.buffer);
1914            let buffer_offset = excerpt
1915                .buffer
1916                .clip_offset_utf16(excerpt_start + (offset - cursor.start()), bias);
1917            OffsetUtf16(buffer_offset.0.saturating_sub(excerpt_start.0))
1918        } else {
1919            OffsetUtf16(0)
1920        };
1921        *cursor.start() + overshoot
1922    }
1923
1924    pub fn clip_point_utf16(&self, point: Unclipped<PointUtf16>, bias: Bias) -> PointUtf16 {
1925        if let Some((_, _, buffer)) = self.as_singleton() {
1926            return buffer.clip_point_utf16(point, bias);
1927        }
1928
1929        let mut cursor = self.excerpts.cursor::<PointUtf16>();
1930        cursor.seek(&point.0, Bias::Right, &());
1931        let overshoot = if let Some(excerpt) = cursor.item() {
1932            let excerpt_start = excerpt
1933                .buffer
1934                .offset_to_point_utf16(excerpt.range.context.start.to_offset(&excerpt.buffer));
1935            let buffer_point = excerpt
1936                .buffer
1937                .clip_point_utf16(Unclipped(excerpt_start + (point.0 - cursor.start())), bias);
1938            buffer_point.saturating_sub(excerpt_start)
1939        } else {
1940            PointUtf16::zero()
1941        };
1942        *cursor.start() + overshoot
1943    }
1944
1945    pub fn bytes_in_range<T: ToOffset>(&self, range: Range<T>) -> MultiBufferBytes {
1946        let range = range.start.to_offset(self)..range.end.to_offset(self);
1947        let mut excerpts = self.excerpts.cursor::<usize>();
1948        excerpts.seek(&range.start, Bias::Right, &());
1949
1950        let mut chunk = &[][..];
1951        let excerpt_bytes = if let Some(excerpt) = excerpts.item() {
1952            let mut excerpt_bytes = excerpt
1953                .bytes_in_range(range.start - excerpts.start()..range.end - excerpts.start());
1954            chunk = excerpt_bytes.next().unwrap_or(&[][..]);
1955            Some(excerpt_bytes)
1956        } else {
1957            None
1958        };
1959
1960        MultiBufferBytes {
1961            range,
1962            excerpts,
1963            excerpt_bytes,
1964            chunk,
1965        }
1966    }
1967
1968    pub fn buffer_rows(&self, start_row: u32) -> MultiBufferRows {
1969        let mut result = MultiBufferRows {
1970            buffer_row_range: 0..0,
1971            excerpts: self.excerpts.cursor(),
1972        };
1973        result.seek(start_row);
1974        result
1975    }
1976
1977    pub fn chunks<T: ToOffset>(&self, range: Range<T>, language_aware: bool) -> MultiBufferChunks {
1978        let range = range.start.to_offset(self)..range.end.to_offset(self);
1979        let mut chunks = MultiBufferChunks {
1980            range: range.clone(),
1981            excerpts: self.excerpts.cursor(),
1982            excerpt_chunks: None,
1983            language_aware,
1984        };
1985        chunks.seek(range.start);
1986        chunks
1987    }
1988
1989    pub fn offset_to_point(&self, offset: usize) -> Point {
1990        if let Some((_, _, buffer)) = self.as_singleton() {
1991            return buffer.offset_to_point(offset);
1992        }
1993
1994        let mut cursor = self.excerpts.cursor::<(usize, Point)>();
1995        cursor.seek(&offset, Bias::Right, &());
1996        if let Some(excerpt) = cursor.item() {
1997            let (start_offset, start_point) = cursor.start();
1998            let overshoot = offset - start_offset;
1999            let excerpt_start_offset = excerpt.range.context.start.to_offset(&excerpt.buffer);
2000            let excerpt_start_point = excerpt.range.context.start.to_point(&excerpt.buffer);
2001            let buffer_point = excerpt
2002                .buffer
2003                .offset_to_point(excerpt_start_offset + overshoot);
2004            *start_point + (buffer_point - excerpt_start_point)
2005        } else {
2006            self.excerpts.summary().text.lines
2007        }
2008    }
2009
2010    pub fn offset_to_point_utf16(&self, offset: usize) -> PointUtf16 {
2011        if let Some((_, _, buffer)) = self.as_singleton() {
2012            return buffer.offset_to_point_utf16(offset);
2013        }
2014
2015        let mut cursor = self.excerpts.cursor::<(usize, PointUtf16)>();
2016        cursor.seek(&offset, Bias::Right, &());
2017        if let Some(excerpt) = cursor.item() {
2018            let (start_offset, start_point) = cursor.start();
2019            let overshoot = offset - start_offset;
2020            let excerpt_start_offset = excerpt.range.context.start.to_offset(&excerpt.buffer);
2021            let excerpt_start_point = excerpt.range.context.start.to_point_utf16(&excerpt.buffer);
2022            let buffer_point = excerpt
2023                .buffer
2024                .offset_to_point_utf16(excerpt_start_offset + overshoot);
2025            *start_point + (buffer_point - excerpt_start_point)
2026        } else {
2027            self.excerpts.summary().text.lines_utf16()
2028        }
2029    }
2030
2031    pub fn point_to_point_utf16(&self, point: Point) -> PointUtf16 {
2032        if let Some((_, _, buffer)) = self.as_singleton() {
2033            return buffer.point_to_point_utf16(point);
2034        }
2035
2036        let mut cursor = self.excerpts.cursor::<(Point, PointUtf16)>();
2037        cursor.seek(&point, Bias::Right, &());
2038        if let Some(excerpt) = cursor.item() {
2039            let (start_offset, start_point) = cursor.start();
2040            let overshoot = point - start_offset;
2041            let excerpt_start_point = excerpt.range.context.start.to_point(&excerpt.buffer);
2042            let excerpt_start_point_utf16 =
2043                excerpt.range.context.start.to_point_utf16(&excerpt.buffer);
2044            let buffer_point = excerpt
2045                .buffer
2046                .point_to_point_utf16(excerpt_start_point + overshoot);
2047            *start_point + (buffer_point - excerpt_start_point_utf16)
2048        } else {
2049            self.excerpts.summary().text.lines_utf16()
2050        }
2051    }
2052
2053    pub fn point_to_offset(&self, point: Point) -> usize {
2054        if let Some((_, _, buffer)) = self.as_singleton() {
2055            return buffer.point_to_offset(point);
2056        }
2057
2058        let mut cursor = self.excerpts.cursor::<(Point, usize)>();
2059        cursor.seek(&point, Bias::Right, &());
2060        if let Some(excerpt) = cursor.item() {
2061            let (start_point, start_offset) = cursor.start();
2062            let overshoot = point - start_point;
2063            let excerpt_start_offset = excerpt.range.context.start.to_offset(&excerpt.buffer);
2064            let excerpt_start_point = excerpt.range.context.start.to_point(&excerpt.buffer);
2065            let buffer_offset = excerpt
2066                .buffer
2067                .point_to_offset(excerpt_start_point + overshoot);
2068            *start_offset + buffer_offset - excerpt_start_offset
2069        } else {
2070            self.excerpts.summary().text.len
2071        }
2072    }
2073
2074    pub fn offset_utf16_to_offset(&self, offset_utf16: OffsetUtf16) -> usize {
2075        if let Some((_, _, buffer)) = self.as_singleton() {
2076            return buffer.offset_utf16_to_offset(offset_utf16);
2077        }
2078
2079        let mut cursor = self.excerpts.cursor::<(OffsetUtf16, usize)>();
2080        cursor.seek(&offset_utf16, Bias::Right, &());
2081        if let Some(excerpt) = cursor.item() {
2082            let (start_offset_utf16, start_offset) = cursor.start();
2083            let overshoot = offset_utf16 - start_offset_utf16;
2084            let excerpt_start_offset = excerpt.range.context.start.to_offset(&excerpt.buffer);
2085            let excerpt_start_offset_utf16 =
2086                excerpt.buffer.offset_to_offset_utf16(excerpt_start_offset);
2087            let buffer_offset = excerpt
2088                .buffer
2089                .offset_utf16_to_offset(excerpt_start_offset_utf16 + overshoot);
2090            *start_offset + (buffer_offset - excerpt_start_offset)
2091        } else {
2092            self.excerpts.summary().text.len
2093        }
2094    }
2095
2096    pub fn offset_to_offset_utf16(&self, offset: usize) -> OffsetUtf16 {
2097        if let Some((_, _, buffer)) = self.as_singleton() {
2098            return buffer.offset_to_offset_utf16(offset);
2099        }
2100
2101        let mut cursor = self.excerpts.cursor::<(usize, OffsetUtf16)>();
2102        cursor.seek(&offset, Bias::Right, &());
2103        if let Some(excerpt) = cursor.item() {
2104            let (start_offset, start_offset_utf16) = cursor.start();
2105            let overshoot = offset - start_offset;
2106            let excerpt_start_offset_utf16 =
2107                excerpt.range.context.start.to_offset_utf16(&excerpt.buffer);
2108            let excerpt_start_offset = excerpt
2109                .buffer
2110                .offset_utf16_to_offset(excerpt_start_offset_utf16);
2111            let buffer_offset_utf16 = excerpt
2112                .buffer
2113                .offset_to_offset_utf16(excerpt_start_offset + overshoot);
2114            *start_offset_utf16 + (buffer_offset_utf16 - excerpt_start_offset_utf16)
2115        } else {
2116            self.excerpts.summary().text.len_utf16
2117        }
2118    }
2119
2120    pub fn point_utf16_to_offset(&self, point: PointUtf16) -> usize {
2121        if let Some((_, _, buffer)) = self.as_singleton() {
2122            return buffer.point_utf16_to_offset(point);
2123        }
2124
2125        let mut cursor = self.excerpts.cursor::<(PointUtf16, usize)>();
2126        cursor.seek(&point, Bias::Right, &());
2127        if let Some(excerpt) = cursor.item() {
2128            let (start_point, start_offset) = cursor.start();
2129            let overshoot = point - start_point;
2130            let excerpt_start_offset = excerpt.range.context.start.to_offset(&excerpt.buffer);
2131            let excerpt_start_point = excerpt
2132                .buffer
2133                .offset_to_point_utf16(excerpt.range.context.start.to_offset(&excerpt.buffer));
2134            let buffer_offset = excerpt
2135                .buffer
2136                .point_utf16_to_offset(excerpt_start_point + overshoot);
2137            *start_offset + (buffer_offset - excerpt_start_offset)
2138        } else {
2139            self.excerpts.summary().text.len
2140        }
2141    }
2142
2143    pub fn point_to_buffer_offset<T: ToOffset>(
2144        &self,
2145        point: T,
2146    ) -> Option<(&BufferSnapshot, usize)> {
2147        let offset = point.to_offset(&self);
2148        let mut cursor = self.excerpts.cursor::<usize>();
2149        cursor.seek(&offset, Bias::Right, &());
2150        if cursor.item().is_none() {
2151            cursor.prev(&());
2152        }
2153
2154        cursor.item().map(|excerpt| {
2155            let excerpt_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
2156            let buffer_point = excerpt_start + offset - *cursor.start();
2157            (&excerpt.buffer, buffer_point)
2158        })
2159    }
2160
2161    pub fn suggested_indents(
2162        &self,
2163        rows: impl IntoIterator<Item = u32>,
2164        cx: &AppContext,
2165    ) -> BTreeMap<u32, IndentSize> {
2166        let mut result = BTreeMap::new();
2167
2168        let mut rows_for_excerpt = Vec::new();
2169        let mut cursor = self.excerpts.cursor::<Point>();
2170        let mut rows = rows.into_iter().peekable();
2171        let mut prev_row = u32::MAX;
2172        let mut prev_language_indent_size = IndentSize::default();
2173
2174        while let Some(row) = rows.next() {
2175            cursor.seek(&Point::new(row, 0), Bias::Right, &());
2176            let excerpt = match cursor.item() {
2177                Some(excerpt) => excerpt,
2178                _ => continue,
2179            };
2180
2181            // Retrieve the language and indent size once for each disjoint region being indented.
2182            let single_indent_size = if row.saturating_sub(1) == prev_row {
2183                prev_language_indent_size
2184            } else {
2185                excerpt
2186                    .buffer
2187                    .language_indent_size_at(Point::new(row, 0), cx)
2188            };
2189            prev_language_indent_size = single_indent_size;
2190            prev_row = row;
2191
2192            let start_buffer_row = excerpt.range.context.start.to_point(&excerpt.buffer).row;
2193            let start_multibuffer_row = cursor.start().row;
2194
2195            rows_for_excerpt.push(row);
2196            while let Some(next_row) = rows.peek().copied() {
2197                if cursor.end(&()).row > next_row {
2198                    rows_for_excerpt.push(next_row);
2199                    rows.next();
2200                } else {
2201                    break;
2202                }
2203            }
2204
2205            let buffer_rows = rows_for_excerpt
2206                .drain(..)
2207                .map(|row| start_buffer_row + row - start_multibuffer_row);
2208            let buffer_indents = excerpt
2209                .buffer
2210                .suggested_indents(buffer_rows, single_indent_size);
2211            let multibuffer_indents = buffer_indents
2212                .into_iter()
2213                .map(|(row, indent)| (start_multibuffer_row + row - start_buffer_row, indent));
2214            result.extend(multibuffer_indents);
2215        }
2216
2217        result
2218    }
2219
2220    pub fn indent_size_for_line(&self, row: u32) -> IndentSize {
2221        if let Some((buffer, range)) = self.buffer_line_for_row(row) {
2222            let mut size = buffer.indent_size_for_line(range.start.row);
2223            size.len = size
2224                .len
2225                .min(range.end.column)
2226                .saturating_sub(range.start.column);
2227            size
2228        } else {
2229            IndentSize::spaces(0)
2230        }
2231    }
2232
2233    pub fn line_len(&self, row: u32) -> u32 {
2234        if let Some((_, range)) = self.buffer_line_for_row(row) {
2235            range.end.column - range.start.column
2236        } else {
2237            0
2238        }
2239    }
2240
2241    pub fn buffer_line_for_row(&self, row: u32) -> Option<(&BufferSnapshot, Range<Point>)> {
2242        let mut cursor = self.excerpts.cursor::<Point>();
2243        let point = Point::new(row, 0);
2244        cursor.seek(&point, Bias::Right, &());
2245        if cursor.item().is_none() && *cursor.start() == point {
2246            cursor.prev(&());
2247        }
2248        if let Some(excerpt) = cursor.item() {
2249            let overshoot = row - cursor.start().row;
2250            let excerpt_start = excerpt.range.context.start.to_point(&excerpt.buffer);
2251            let excerpt_end = excerpt.range.context.end.to_point(&excerpt.buffer);
2252            let buffer_row = excerpt_start.row + overshoot;
2253            let line_start = Point::new(buffer_row, 0);
2254            let line_end = Point::new(buffer_row, excerpt.buffer.line_len(buffer_row));
2255            return Some((
2256                &excerpt.buffer,
2257                line_start.max(excerpt_start)..line_end.min(excerpt_end),
2258            ));
2259        }
2260        None
2261    }
2262
2263    pub fn max_point(&self) -> Point {
2264        self.text_summary().lines
2265    }
2266
2267    pub fn text_summary(&self) -> TextSummary {
2268        self.excerpts.summary().text.clone()
2269    }
2270
2271    pub fn text_summary_for_range<D, O>(&self, range: Range<O>) -> D
2272    where
2273        D: TextDimension,
2274        O: ToOffset,
2275    {
2276        let mut summary = D::default();
2277        let mut range = range.start.to_offset(self)..range.end.to_offset(self);
2278        let mut cursor = self.excerpts.cursor::<usize>();
2279        cursor.seek(&range.start, Bias::Right, &());
2280        if let Some(excerpt) = cursor.item() {
2281            let mut end_before_newline = cursor.end(&());
2282            if excerpt.has_trailing_newline {
2283                end_before_newline -= 1;
2284            }
2285
2286            let excerpt_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
2287            let start_in_excerpt = excerpt_start + (range.start - cursor.start());
2288            let end_in_excerpt =
2289                excerpt_start + (cmp::min(end_before_newline, range.end) - cursor.start());
2290            summary.add_assign(
2291                &excerpt
2292                    .buffer
2293                    .text_summary_for_range(start_in_excerpt..end_in_excerpt),
2294            );
2295
2296            if range.end > end_before_newline {
2297                summary.add_assign(&D::from_text_summary(&TextSummary::from("\n")));
2298            }
2299
2300            cursor.next(&());
2301        }
2302
2303        if range.end > *cursor.start() {
2304            summary.add_assign(&D::from_text_summary(&cursor.summary::<_, TextSummary>(
2305                &range.end,
2306                Bias::Right,
2307                &(),
2308            )));
2309            if let Some(excerpt) = cursor.item() {
2310                range.end = cmp::max(*cursor.start(), range.end);
2311
2312                let excerpt_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
2313                let end_in_excerpt = excerpt_start + (range.end - cursor.start());
2314                summary.add_assign(
2315                    &excerpt
2316                        .buffer
2317                        .text_summary_for_range(excerpt_start..end_in_excerpt),
2318                );
2319            }
2320        }
2321
2322        summary
2323    }
2324
2325    pub fn summary_for_anchor<D>(&self, anchor: &Anchor) -> D
2326    where
2327        D: TextDimension + Ord + Sub<D, Output = D>,
2328    {
2329        let mut cursor = self.excerpts.cursor::<ExcerptSummary>();
2330        let locator = self.excerpt_locator_for_id(anchor.excerpt_id);
2331
2332        cursor.seek(locator, Bias::Left, &());
2333        if cursor.item().is_none() {
2334            cursor.next(&());
2335        }
2336
2337        let mut position = D::from_text_summary(&cursor.start().text);
2338        if let Some(excerpt) = cursor.item() {
2339            if excerpt.id == anchor.excerpt_id {
2340                let excerpt_buffer_start =
2341                    excerpt.range.context.start.summary::<D>(&excerpt.buffer);
2342                let excerpt_buffer_end = excerpt.range.context.end.summary::<D>(&excerpt.buffer);
2343                let buffer_position = cmp::min(
2344                    excerpt_buffer_end,
2345                    anchor.text_anchor.summary::<D>(&excerpt.buffer),
2346                );
2347                if buffer_position > excerpt_buffer_start {
2348                    position.add_assign(&(buffer_position - excerpt_buffer_start));
2349                }
2350            }
2351        }
2352        position
2353    }
2354
2355    pub fn summaries_for_anchors<'a, D, I>(&'a self, anchors: I) -> Vec<D>
2356    where
2357        D: TextDimension + Ord + Sub<D, Output = D>,
2358        I: 'a + IntoIterator<Item = &'a Anchor>,
2359    {
2360        if let Some((_, _, buffer)) = self.as_singleton() {
2361            return buffer
2362                .summaries_for_anchors(anchors.into_iter().map(|a| &a.text_anchor))
2363                .collect();
2364        }
2365
2366        let mut anchors = anchors.into_iter().peekable();
2367        let mut cursor = self.excerpts.cursor::<ExcerptSummary>();
2368        let mut summaries = Vec::new();
2369        while let Some(anchor) = anchors.peek() {
2370            let excerpt_id = anchor.excerpt_id;
2371            let excerpt_anchors = iter::from_fn(|| {
2372                let anchor = anchors.peek()?;
2373                if anchor.excerpt_id == excerpt_id {
2374                    Some(&anchors.next().unwrap().text_anchor)
2375                } else {
2376                    None
2377                }
2378            });
2379
2380            let locator = self.excerpt_locator_for_id(excerpt_id);
2381            cursor.seek_forward(locator, Bias::Left, &());
2382            if cursor.item().is_none() {
2383                cursor.next(&());
2384            }
2385
2386            let position = D::from_text_summary(&cursor.start().text);
2387            if let Some(excerpt) = cursor.item() {
2388                if excerpt.id == excerpt_id {
2389                    let excerpt_buffer_start =
2390                        excerpt.range.context.start.summary::<D>(&excerpt.buffer);
2391                    let excerpt_buffer_end =
2392                        excerpt.range.context.end.summary::<D>(&excerpt.buffer);
2393                    summaries.extend(
2394                        excerpt
2395                            .buffer
2396                            .summaries_for_anchors::<D, _>(excerpt_anchors)
2397                            .map(move |summary| {
2398                                let summary = cmp::min(excerpt_buffer_end.clone(), summary);
2399                                let mut position = position.clone();
2400                                let excerpt_buffer_start = excerpt_buffer_start.clone();
2401                                if summary > excerpt_buffer_start {
2402                                    position.add_assign(&(summary - excerpt_buffer_start));
2403                                }
2404                                position
2405                            }),
2406                    );
2407                    continue;
2408                }
2409            }
2410
2411            summaries.extend(excerpt_anchors.map(|_| position.clone()));
2412        }
2413
2414        summaries
2415    }
2416
2417    pub fn refresh_anchors<'a, I>(&'a self, anchors: I) -> Vec<(usize, Anchor, bool)>
2418    where
2419        I: 'a + IntoIterator<Item = &'a Anchor>,
2420    {
2421        let mut anchors = anchors.into_iter().enumerate().peekable();
2422        let mut cursor = self.excerpts.cursor::<Option<&Locator>>();
2423        cursor.next(&());
2424
2425        let mut result = Vec::new();
2426
2427        while let Some((_, anchor)) = anchors.peek() {
2428            let old_excerpt_id = anchor.excerpt_id;
2429
2430            // Find the location where this anchor's excerpt should be.
2431            let old_locator = self.excerpt_locator_for_id(old_excerpt_id);
2432            cursor.seek_forward(&Some(old_locator), Bias::Left, &());
2433
2434            if cursor.item().is_none() {
2435                cursor.next(&());
2436            }
2437
2438            let next_excerpt = cursor.item();
2439            let prev_excerpt = cursor.prev_item();
2440
2441            // Process all of the anchors for this excerpt.
2442            while let Some((_, anchor)) = anchors.peek() {
2443                if anchor.excerpt_id != old_excerpt_id {
2444                    break;
2445                }
2446                let (anchor_ix, anchor) = anchors.next().unwrap();
2447                let mut anchor = *anchor;
2448
2449                // Leave min and max anchors unchanged if invalid or
2450                // if the old excerpt still exists at this location
2451                let mut kept_position = next_excerpt
2452                    .map_or(false, |e| e.id == old_excerpt_id && e.contains(&anchor))
2453                    || old_excerpt_id == ExcerptId::max()
2454                    || old_excerpt_id == ExcerptId::min();
2455
2456                // If the old excerpt no longer exists at this location, then attempt to
2457                // find an equivalent position for this anchor in an adjacent excerpt.
2458                if !kept_position {
2459                    for excerpt in [next_excerpt, prev_excerpt].iter().filter_map(|e| *e) {
2460                        if excerpt.contains(&anchor) {
2461                            anchor.excerpt_id = excerpt.id.clone();
2462                            kept_position = true;
2463                            break;
2464                        }
2465                    }
2466                }
2467
2468                // If there's no adjacent excerpt that contains the anchor's position,
2469                // then report that the anchor has lost its position.
2470                if !kept_position {
2471                    anchor = if let Some(excerpt) = next_excerpt {
2472                        let mut text_anchor = excerpt
2473                            .range
2474                            .context
2475                            .start
2476                            .bias(anchor.text_anchor.bias, &excerpt.buffer);
2477                        if text_anchor
2478                            .cmp(&excerpt.range.context.end, &excerpt.buffer)
2479                            .is_gt()
2480                        {
2481                            text_anchor = excerpt.range.context.end;
2482                        }
2483                        Anchor {
2484                            buffer_id: Some(excerpt.buffer_id),
2485                            excerpt_id: excerpt.id.clone(),
2486                            text_anchor,
2487                        }
2488                    } else if let Some(excerpt) = prev_excerpt {
2489                        let mut text_anchor = excerpt
2490                            .range
2491                            .context
2492                            .end
2493                            .bias(anchor.text_anchor.bias, &excerpt.buffer);
2494                        if text_anchor
2495                            .cmp(&excerpt.range.context.start, &excerpt.buffer)
2496                            .is_lt()
2497                        {
2498                            text_anchor = excerpt.range.context.start;
2499                        }
2500                        Anchor {
2501                            buffer_id: Some(excerpt.buffer_id),
2502                            excerpt_id: excerpt.id.clone(),
2503                            text_anchor,
2504                        }
2505                    } else if anchor.text_anchor.bias == Bias::Left {
2506                        Anchor::min()
2507                    } else {
2508                        Anchor::max()
2509                    };
2510                }
2511
2512                result.push((anchor_ix, anchor, kept_position));
2513            }
2514        }
2515        result.sort_unstable_by(|a, b| a.1.cmp(&b.1, self));
2516        result
2517    }
2518
2519    pub fn anchor_before<T: ToOffset>(&self, position: T) -> Anchor {
2520        self.anchor_at(position, Bias::Left)
2521    }
2522
2523    pub fn anchor_after<T: ToOffset>(&self, position: T) -> Anchor {
2524        self.anchor_at(position, Bias::Right)
2525    }
2526
2527    pub fn anchor_at<T: ToOffset>(&self, position: T, mut bias: Bias) -> Anchor {
2528        let offset = position.to_offset(self);
2529        if let Some((excerpt_id, buffer_id, buffer)) = self.as_singleton() {
2530            return Anchor {
2531                buffer_id: Some(buffer_id),
2532                excerpt_id: excerpt_id.clone(),
2533                text_anchor: buffer.anchor_at(offset, bias),
2534            };
2535        }
2536
2537        let mut cursor = self.excerpts.cursor::<(usize, Option<ExcerptId>)>();
2538        cursor.seek(&offset, Bias::Right, &());
2539        if cursor.item().is_none() && offset == cursor.start().0 && bias == Bias::Left {
2540            cursor.prev(&());
2541        }
2542        if let Some(excerpt) = cursor.item() {
2543            let mut overshoot = offset.saturating_sub(cursor.start().0);
2544            if excerpt.has_trailing_newline && offset == cursor.end(&()).0 {
2545                overshoot -= 1;
2546                bias = Bias::Right;
2547            }
2548
2549            let buffer_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
2550            let text_anchor =
2551                excerpt.clip_anchor(excerpt.buffer.anchor_at(buffer_start + overshoot, bias));
2552            Anchor {
2553                buffer_id: Some(excerpt.buffer_id),
2554                excerpt_id: excerpt.id.clone(),
2555                text_anchor,
2556            }
2557        } else if offset == 0 && bias == Bias::Left {
2558            Anchor::min()
2559        } else {
2560            Anchor::max()
2561        }
2562    }
2563
2564    pub fn anchor_in_excerpt(&self, excerpt_id: ExcerptId, text_anchor: text::Anchor) -> Anchor {
2565        let locator = self.excerpt_locator_for_id(excerpt_id);
2566        let mut cursor = self.excerpts.cursor::<Option<&Locator>>();
2567        cursor.seek(locator, Bias::Left, &());
2568        if let Some(excerpt) = cursor.item() {
2569            if excerpt.id == excerpt_id {
2570                let text_anchor = excerpt.clip_anchor(text_anchor);
2571                drop(cursor);
2572                return Anchor {
2573                    buffer_id: Some(excerpt.buffer_id),
2574                    excerpt_id,
2575                    text_anchor,
2576                };
2577            }
2578        }
2579        panic!("excerpt not found");
2580    }
2581
2582    pub fn can_resolve(&self, anchor: &Anchor) -> bool {
2583        if anchor.excerpt_id == ExcerptId::min() || anchor.excerpt_id == ExcerptId::max() {
2584            true
2585        } else if let Some(excerpt) = self.excerpt(anchor.excerpt_id) {
2586            excerpt.buffer.can_resolve(&anchor.text_anchor)
2587        } else {
2588            false
2589        }
2590    }
2591
2592    pub fn excerpts(
2593        &self,
2594    ) -> impl Iterator<Item = (ExcerptId, &BufferSnapshot, ExcerptRange<text::Anchor>)> {
2595        self.excerpts
2596            .iter()
2597            .map(|excerpt| (excerpt.id, &excerpt.buffer, excerpt.range.clone()))
2598    }
2599
2600    pub fn excerpt_boundaries_in_range<R, T>(
2601        &self,
2602        range: R,
2603    ) -> impl Iterator<Item = ExcerptBoundary> + '_
2604    where
2605        R: RangeBounds<T>,
2606        T: ToOffset,
2607    {
2608        let start_offset;
2609        let start = match range.start_bound() {
2610            Bound::Included(start) => {
2611                start_offset = start.to_offset(self);
2612                Bound::Included(start_offset)
2613            }
2614            Bound::Excluded(start) => {
2615                start_offset = start.to_offset(self);
2616                Bound::Excluded(start_offset)
2617            }
2618            Bound::Unbounded => {
2619                start_offset = 0;
2620                Bound::Unbounded
2621            }
2622        };
2623        let end = match range.end_bound() {
2624            Bound::Included(end) => Bound::Included(end.to_offset(self)),
2625            Bound::Excluded(end) => Bound::Excluded(end.to_offset(self)),
2626            Bound::Unbounded => Bound::Unbounded,
2627        };
2628        let bounds = (start, end);
2629
2630        let mut cursor = self.excerpts.cursor::<(usize, Point)>();
2631        cursor.seek(&start_offset, Bias::Right, &());
2632        if cursor.item().is_none() {
2633            cursor.prev(&());
2634        }
2635        if !bounds.contains(&cursor.start().0) {
2636            cursor.next(&());
2637        }
2638
2639        let mut prev_buffer_id = cursor.prev_item().map(|excerpt| excerpt.buffer_id);
2640        std::iter::from_fn(move || {
2641            if self.singleton {
2642                None
2643            } else if bounds.contains(&cursor.start().0) {
2644                let excerpt = cursor.item()?;
2645                let starts_new_buffer = Some(excerpt.buffer_id) != prev_buffer_id;
2646                let boundary = ExcerptBoundary {
2647                    id: excerpt.id.clone(),
2648                    row: cursor.start().1.row,
2649                    buffer: excerpt.buffer.clone(),
2650                    range: excerpt.range.clone(),
2651                    starts_new_buffer,
2652                };
2653
2654                prev_buffer_id = Some(excerpt.buffer_id);
2655                cursor.next(&());
2656                Some(boundary)
2657            } else {
2658                None
2659            }
2660        })
2661    }
2662
2663    pub fn edit_count(&self) -> usize {
2664        self.edit_count
2665    }
2666
2667    pub fn parse_count(&self) -> usize {
2668        self.parse_count
2669    }
2670
2671    /// Returns the smallest enclosing bracket ranges containing the given range or
2672    /// None if no brackets contain range or the range is not contained in a single
2673    /// excerpt
2674    pub fn innermost_enclosing_bracket_ranges<T: ToOffset>(
2675        &self,
2676        range: Range<T>,
2677    ) -> Option<(Range<usize>, Range<usize>)> {
2678        let range = range.start.to_offset(self)..range.end.to_offset(self);
2679
2680        // Get the ranges of the innermost pair of brackets.
2681        let mut result: Option<(Range<usize>, Range<usize>)> = None;
2682
2683        let Some(enclosing_bracket_ranges) = self.enclosing_bracket_ranges(range.clone()) else { return None; };
2684
2685        for (open, close) in enclosing_bracket_ranges {
2686            let len = close.end - open.start;
2687
2688            if let Some((existing_open, existing_close)) = &result {
2689                let existing_len = existing_close.end - existing_open.start;
2690                if len > existing_len {
2691                    continue;
2692                }
2693            }
2694
2695            result = Some((open, close));
2696        }
2697
2698        result
2699    }
2700
2701    /// Returns enclosing bracket ranges containing the given range or returns None if the range is
2702    /// not contained in a single excerpt
2703    pub fn enclosing_bracket_ranges<'a, T: ToOffset>(
2704        &'a self,
2705        range: Range<T>,
2706    ) -> Option<impl Iterator<Item = (Range<usize>, Range<usize>)> + 'a> {
2707        let range = range.start.to_offset(self)..range.end.to_offset(self);
2708
2709        self.bracket_ranges(range.clone()).map(|range_pairs| {
2710            range_pairs
2711                .filter(move |(open, close)| open.start <= range.start && close.end >= range.end)
2712        })
2713    }
2714
2715    /// Returns bracket range pairs overlapping the given `range` or returns None if the `range` is
2716    /// not contained in a single excerpt
2717    pub fn bracket_ranges<'a, T: ToOffset>(
2718        &'a self,
2719        range: Range<T>,
2720    ) -> Option<impl Iterator<Item = (Range<usize>, Range<usize>)> + 'a> {
2721        let range = range.start.to_offset(self)..range.end.to_offset(self);
2722        let excerpt = self.excerpt_containing(range.clone());
2723        excerpt.map(|(excerpt, excerpt_offset)| {
2724            let excerpt_buffer_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
2725            let excerpt_buffer_end = excerpt_buffer_start + excerpt.text_summary.len;
2726
2727            let start_in_buffer = excerpt_buffer_start + range.start.saturating_sub(excerpt_offset);
2728            let end_in_buffer = excerpt_buffer_start + range.end.saturating_sub(excerpt_offset);
2729
2730            excerpt
2731                .buffer
2732                .bracket_ranges(start_in_buffer..end_in_buffer)
2733                .filter_map(move |(start_bracket_range, end_bracket_range)| {
2734                    if start_bracket_range.start < excerpt_buffer_start
2735                        || end_bracket_range.end > excerpt_buffer_end
2736                    {
2737                        return None;
2738                    }
2739
2740                    let mut start_bracket_range = start_bracket_range.clone();
2741                    start_bracket_range.start =
2742                        excerpt_offset + (start_bracket_range.start - excerpt_buffer_start);
2743                    start_bracket_range.end =
2744                        excerpt_offset + (start_bracket_range.end - excerpt_buffer_start);
2745
2746                    let mut end_bracket_range = end_bracket_range.clone();
2747                    end_bracket_range.start =
2748                        excerpt_offset + (end_bracket_range.start - excerpt_buffer_start);
2749                    end_bracket_range.end =
2750                        excerpt_offset + (end_bracket_range.end - excerpt_buffer_start);
2751                    Some((start_bracket_range, end_bracket_range))
2752                })
2753        })
2754    }
2755
2756    pub fn diagnostics_update_count(&self) -> usize {
2757        self.diagnostics_update_count
2758    }
2759
2760    pub fn git_diff_update_count(&self) -> usize {
2761        self.git_diff_update_count
2762    }
2763
2764    pub fn trailing_excerpt_update_count(&self) -> usize {
2765        self.trailing_excerpt_update_count
2766    }
2767
2768    pub fn file_at<'a, T: ToOffset>(&'a self, point: T) -> Option<&'a Arc<dyn File>> {
2769        self.point_to_buffer_offset(point)
2770            .and_then(|(buffer, _)| buffer.file())
2771    }
2772
2773    pub fn language_at<'a, T: ToOffset>(&'a self, point: T) -> Option<&'a Arc<Language>> {
2774        self.point_to_buffer_offset(point)
2775            .and_then(|(buffer, offset)| buffer.language_at(offset))
2776    }
2777
2778    pub fn settings_at<'a, T: ToOffset>(
2779        &'a self,
2780        point: T,
2781        cx: &'a AppContext,
2782    ) -> &'a LanguageSettings {
2783        self.point_to_buffer_offset(point)
2784            .map(|(buffer, offset)| buffer.settings_at(offset, cx))
2785            .unwrap_or_else(|| language_settings(None, None, cx))
2786    }
2787
2788    pub fn language_scope_at<'a, T: ToOffset>(&'a self, point: T) -> Option<LanguageScope> {
2789        self.point_to_buffer_offset(point)
2790            .and_then(|(buffer, offset)| buffer.language_scope_at(offset))
2791    }
2792
2793    pub fn language_indent_size_at<T: ToOffset>(
2794        &self,
2795        position: T,
2796        cx: &AppContext,
2797    ) -> Option<IndentSize> {
2798        let (buffer_snapshot, offset) = self.point_to_buffer_offset(position)?;
2799        Some(buffer_snapshot.language_indent_size_at(offset, cx))
2800    }
2801
2802    pub fn is_dirty(&self) -> bool {
2803        self.is_dirty
2804    }
2805
2806    pub fn has_conflict(&self) -> bool {
2807        self.has_conflict
2808    }
2809
2810    pub fn diagnostic_group<'a, O>(
2811        &'a self,
2812        group_id: usize,
2813    ) -> impl Iterator<Item = DiagnosticEntry<O>> + 'a
2814    where
2815        O: text::FromAnchor + 'a,
2816    {
2817        self.as_singleton()
2818            .into_iter()
2819            .flat_map(move |(_, _, buffer)| buffer.diagnostic_group(group_id))
2820    }
2821
2822    pub fn diagnostics_in_range<'a, T, O>(
2823        &'a self,
2824        range: Range<T>,
2825        reversed: bool,
2826    ) -> impl Iterator<Item = DiagnosticEntry<O>> + 'a
2827    where
2828        T: 'a + ToOffset,
2829        O: 'a + text::FromAnchor + Ord,
2830    {
2831        self.as_singleton()
2832            .into_iter()
2833            .flat_map(move |(_, _, buffer)| {
2834                buffer.diagnostics_in_range(
2835                    range.start.to_offset(self)..range.end.to_offset(self),
2836                    reversed,
2837                )
2838            })
2839    }
2840
2841    pub fn git_diff_hunks_in_range<'a>(
2842        &'a self,
2843        row_range: Range<u32>,
2844        reversed: bool,
2845    ) -> impl 'a + Iterator<Item = DiffHunk<u32>> {
2846        let mut cursor = self.excerpts.cursor::<Point>();
2847
2848        if reversed {
2849            cursor.seek(&Point::new(row_range.end, 0), Bias::Left, &());
2850            if cursor.item().is_none() {
2851                cursor.prev(&());
2852            }
2853        } else {
2854            cursor.seek(&Point::new(row_range.start, 0), Bias::Right, &());
2855        }
2856
2857        std::iter::from_fn(move || {
2858            let excerpt = cursor.item()?;
2859            let multibuffer_start = *cursor.start();
2860            let multibuffer_end = multibuffer_start + excerpt.text_summary.lines;
2861            if multibuffer_start.row >= row_range.end {
2862                return None;
2863            }
2864
2865            let mut buffer_start = excerpt.range.context.start;
2866            let mut buffer_end = excerpt.range.context.end;
2867            let excerpt_start_point = buffer_start.to_point(&excerpt.buffer);
2868            let excerpt_end_point = excerpt_start_point + excerpt.text_summary.lines;
2869
2870            if row_range.start > multibuffer_start.row {
2871                let buffer_start_point =
2872                    excerpt_start_point + Point::new(row_range.start - multibuffer_start.row, 0);
2873                buffer_start = excerpt.buffer.anchor_before(buffer_start_point);
2874            }
2875
2876            if row_range.end < multibuffer_end.row {
2877                let buffer_end_point =
2878                    excerpt_start_point + Point::new(row_range.end - multibuffer_start.row, 0);
2879                buffer_end = excerpt.buffer.anchor_before(buffer_end_point);
2880            }
2881
2882            let buffer_hunks = excerpt
2883                .buffer
2884                .git_diff_hunks_intersecting_range(buffer_start..buffer_end, reversed)
2885                .filter_map(move |hunk| {
2886                    let start = multibuffer_start.row
2887                        + hunk
2888                            .buffer_range
2889                            .start
2890                            .saturating_sub(excerpt_start_point.row);
2891                    let end = multibuffer_start.row
2892                        + hunk
2893                            .buffer_range
2894                            .end
2895                            .min(excerpt_end_point.row + 1)
2896                            .saturating_sub(excerpt_start_point.row);
2897
2898                    Some(DiffHunk {
2899                        buffer_range: start..end,
2900                        diff_base_byte_range: hunk.diff_base_byte_range.clone(),
2901                    })
2902                });
2903
2904            if reversed {
2905                cursor.prev(&());
2906            } else {
2907                cursor.next(&());
2908            }
2909
2910            Some(buffer_hunks)
2911        })
2912        .flatten()
2913    }
2914
2915    pub fn range_for_syntax_ancestor<T: ToOffset>(&self, range: Range<T>) -> Option<Range<usize>> {
2916        let range = range.start.to_offset(self)..range.end.to_offset(self);
2917
2918        self.excerpt_containing(range.clone())
2919            .and_then(|(excerpt, excerpt_offset)| {
2920                let excerpt_buffer_start = excerpt.range.context.start.to_offset(&excerpt.buffer);
2921                let excerpt_buffer_end = excerpt_buffer_start + excerpt.text_summary.len;
2922
2923                let start_in_buffer =
2924                    excerpt_buffer_start + range.start.saturating_sub(excerpt_offset);
2925                let end_in_buffer = excerpt_buffer_start + range.end.saturating_sub(excerpt_offset);
2926                let mut ancestor_buffer_range = excerpt
2927                    .buffer
2928                    .range_for_syntax_ancestor(start_in_buffer..end_in_buffer)?;
2929                ancestor_buffer_range.start =
2930                    cmp::max(ancestor_buffer_range.start, excerpt_buffer_start);
2931                ancestor_buffer_range.end = cmp::min(ancestor_buffer_range.end, excerpt_buffer_end);
2932
2933                let start = excerpt_offset + (ancestor_buffer_range.start - excerpt_buffer_start);
2934                let end = excerpt_offset + (ancestor_buffer_range.end - excerpt_buffer_start);
2935                Some(start..end)
2936            })
2937    }
2938
2939    pub fn outline(&self, theme: Option<&SyntaxTheme>) -> Option<Outline<Anchor>> {
2940        let (excerpt_id, _, buffer) = self.as_singleton()?;
2941        let outline = buffer.outline(theme)?;
2942        Some(Outline::new(
2943            outline
2944                .items
2945                .into_iter()
2946                .map(|item| OutlineItem {
2947                    depth: item.depth,
2948                    range: self.anchor_in_excerpt(excerpt_id.clone(), item.range.start)
2949                        ..self.anchor_in_excerpt(excerpt_id.clone(), item.range.end),
2950                    text: item.text,
2951                    highlight_ranges: item.highlight_ranges,
2952                    name_ranges: item.name_ranges,
2953                })
2954                .collect(),
2955        ))
2956    }
2957
2958    pub fn symbols_containing<T: ToOffset>(
2959        &self,
2960        offset: T,
2961        theme: Option<&SyntaxTheme>,
2962    ) -> Option<(u64, Vec<OutlineItem<Anchor>>)> {
2963        let anchor = self.anchor_before(offset);
2964        let excerpt_id = anchor.excerpt_id();
2965        let excerpt = self.excerpt(excerpt_id)?;
2966        Some((
2967            excerpt.buffer_id,
2968            excerpt
2969                .buffer
2970                .symbols_containing(anchor.text_anchor, theme)
2971                .into_iter()
2972                .flatten()
2973                .map(|item| OutlineItem {
2974                    depth: item.depth,
2975                    range: self.anchor_in_excerpt(excerpt_id, item.range.start)
2976                        ..self.anchor_in_excerpt(excerpt_id, item.range.end),
2977                    text: item.text,
2978                    highlight_ranges: item.highlight_ranges,
2979                    name_ranges: item.name_ranges,
2980                })
2981                .collect(),
2982        ))
2983    }
2984
2985    fn excerpt_locator_for_id<'a>(&'a self, id: ExcerptId) -> &'a Locator {
2986        if id == ExcerptId::min() {
2987            Locator::min_ref()
2988        } else if id == ExcerptId::max() {
2989            Locator::max_ref()
2990        } else {
2991            let mut cursor = self.excerpt_ids.cursor::<ExcerptId>();
2992            cursor.seek(&id, Bias::Left, &());
2993            if let Some(entry) = cursor.item() {
2994                if entry.id == id {
2995                    return &entry.locator;
2996                }
2997            }
2998            panic!("invalid excerpt id {:?}", id)
2999        }
3000    }
3001
3002    pub fn buffer_id_for_excerpt(&self, excerpt_id: ExcerptId) -> Option<u64> {
3003        Some(self.excerpt(excerpt_id)?.buffer_id)
3004    }
3005
3006    pub fn buffer_for_excerpt(&self, excerpt_id: ExcerptId) -> Option<&BufferSnapshot> {
3007        Some(&self.excerpt(excerpt_id)?.buffer)
3008    }
3009
3010    fn excerpt<'a>(&'a self, excerpt_id: ExcerptId) -> Option<&'a Excerpt> {
3011        let mut cursor = self.excerpts.cursor::<Option<&Locator>>();
3012        let locator = self.excerpt_locator_for_id(excerpt_id);
3013        cursor.seek(&Some(locator), Bias::Left, &());
3014        if let Some(excerpt) = cursor.item() {
3015            if excerpt.id == excerpt_id {
3016                return Some(excerpt);
3017            }
3018        }
3019        None
3020    }
3021
3022    /// Returns the excerpt containing range and its offset start within the multibuffer or none if `range` spans multiple excerpts
3023    fn excerpt_containing<'a, T: ToOffset>(
3024        &'a self,
3025        range: Range<T>,
3026    ) -> Option<(&'a Excerpt, usize)> {
3027        let range = range.start.to_offset(self)..range.end.to_offset(self);
3028
3029        let mut cursor = self.excerpts.cursor::<usize>();
3030        cursor.seek(&range.start, Bias::Right, &());
3031        let start_excerpt = cursor.item();
3032
3033        if range.start == range.end {
3034            return start_excerpt.map(|excerpt| (excerpt, *cursor.start()));
3035        }
3036
3037        cursor.seek(&range.end, Bias::Right, &());
3038        let end_excerpt = cursor.item();
3039
3040        start_excerpt
3041            .zip(end_excerpt)
3042            .and_then(|(start_excerpt, end_excerpt)| {
3043                if start_excerpt.id != end_excerpt.id {
3044                    return None;
3045                }
3046
3047                Some((start_excerpt, *cursor.start()))
3048            })
3049    }
3050
3051    pub fn remote_selections_in_range<'a>(
3052        &'a self,
3053        range: &'a Range<Anchor>,
3054    ) -> impl 'a + Iterator<Item = (ReplicaId, bool, CursorShape, Selection<Anchor>)> {
3055        let mut cursor = self.excerpts.cursor::<ExcerptSummary>();
3056        let start_locator = self.excerpt_locator_for_id(range.start.excerpt_id);
3057        let end_locator = self.excerpt_locator_for_id(range.end.excerpt_id);
3058        cursor.seek(start_locator, Bias::Left, &());
3059        cursor
3060            .take_while(move |excerpt| excerpt.locator <= *end_locator)
3061            .flat_map(move |excerpt| {
3062                let mut query_range = excerpt.range.context.start..excerpt.range.context.end;
3063                if excerpt.id == range.start.excerpt_id {
3064                    query_range.start = range.start.text_anchor;
3065                }
3066                if excerpt.id == range.end.excerpt_id {
3067                    query_range.end = range.end.text_anchor;
3068                }
3069
3070                excerpt
3071                    .buffer
3072                    .remote_selections_in_range(query_range)
3073                    .flat_map(move |(replica_id, line_mode, cursor_shape, selections)| {
3074                        selections.map(move |selection| {
3075                            let mut start = Anchor {
3076                                buffer_id: Some(excerpt.buffer_id),
3077                                excerpt_id: excerpt.id.clone(),
3078                                text_anchor: selection.start,
3079                            };
3080                            let mut end = Anchor {
3081                                buffer_id: Some(excerpt.buffer_id),
3082                                excerpt_id: excerpt.id.clone(),
3083                                text_anchor: selection.end,
3084                            };
3085                            if range.start.cmp(&start, self).is_gt() {
3086                                start = range.start.clone();
3087                            }
3088                            if range.end.cmp(&end, self).is_lt() {
3089                                end = range.end.clone();
3090                            }
3091
3092                            (
3093                                replica_id,
3094                                line_mode,
3095                                cursor_shape,
3096                                Selection {
3097                                    id: selection.id,
3098                                    start,
3099                                    end,
3100                                    reversed: selection.reversed,
3101                                    goal: selection.goal,
3102                                },
3103                            )
3104                        })
3105                    })
3106            })
3107    }
3108}
3109
3110#[cfg(any(test, feature = "test-support"))]
3111impl MultiBufferSnapshot {
3112    pub fn random_byte_range(&self, start_offset: usize, rng: &mut impl rand::Rng) -> Range<usize> {
3113        let end = self.clip_offset(rng.gen_range(start_offset..=self.len()), Bias::Right);
3114        let start = self.clip_offset(rng.gen_range(start_offset..=end), Bias::Right);
3115        start..end
3116    }
3117}
3118
3119impl History {
3120    fn start_transaction(&mut self, now: Instant) -> Option<TransactionId> {
3121        self.transaction_depth += 1;
3122        if self.transaction_depth == 1 {
3123            let id = self.next_transaction_id.tick();
3124            self.undo_stack.push(Transaction {
3125                id,
3126                buffer_transactions: Default::default(),
3127                first_edit_at: now,
3128                last_edit_at: now,
3129                suppress_grouping: false,
3130            });
3131            Some(id)
3132        } else {
3133            None
3134        }
3135    }
3136
3137    fn end_transaction(
3138        &mut self,
3139        now: Instant,
3140        buffer_transactions: HashMap<u64, TransactionId>,
3141    ) -> bool {
3142        assert_ne!(self.transaction_depth, 0);
3143        self.transaction_depth -= 1;
3144        if self.transaction_depth == 0 {
3145            if buffer_transactions.is_empty() {
3146                self.undo_stack.pop();
3147                false
3148            } else {
3149                self.redo_stack.clear();
3150                let transaction = self.undo_stack.last_mut().unwrap();
3151                transaction.last_edit_at = now;
3152                for (buffer_id, transaction_id) in buffer_transactions {
3153                    transaction
3154                        .buffer_transactions
3155                        .entry(buffer_id)
3156                        .or_insert(transaction_id);
3157                }
3158                true
3159            }
3160        } else {
3161            false
3162        }
3163    }
3164
3165    fn push_transaction<'a, T>(
3166        &mut self,
3167        buffer_transactions: T,
3168        now: Instant,
3169        cx: &mut ModelContext<MultiBuffer>,
3170    ) where
3171        T: IntoIterator<Item = (&'a ModelHandle<Buffer>, &'a language::Transaction)>,
3172    {
3173        assert_eq!(self.transaction_depth, 0);
3174        let transaction = Transaction {
3175            id: self.next_transaction_id.tick(),
3176            buffer_transactions: buffer_transactions
3177                .into_iter()
3178                .map(|(buffer, transaction)| (buffer.read(cx).remote_id(), transaction.id))
3179                .collect(),
3180            first_edit_at: now,
3181            last_edit_at: now,
3182            suppress_grouping: false,
3183        };
3184        if !transaction.buffer_transactions.is_empty() {
3185            self.undo_stack.push(transaction);
3186            self.redo_stack.clear();
3187        }
3188    }
3189
3190    fn finalize_last_transaction(&mut self) {
3191        if let Some(transaction) = self.undo_stack.last_mut() {
3192            transaction.suppress_grouping = true;
3193        }
3194    }
3195
3196    fn pop_undo(&mut self) -> Option<&mut Transaction> {
3197        assert_eq!(self.transaction_depth, 0);
3198        if let Some(transaction) = self.undo_stack.pop() {
3199            self.redo_stack.push(transaction);
3200            self.redo_stack.last_mut()
3201        } else {
3202            None
3203        }
3204    }
3205
3206    fn pop_redo(&mut self) -> Option<&mut Transaction> {
3207        assert_eq!(self.transaction_depth, 0);
3208        if let Some(transaction) = self.redo_stack.pop() {
3209            self.undo_stack.push(transaction);
3210            self.undo_stack.last_mut()
3211        } else {
3212            None
3213        }
3214    }
3215
3216    fn group(&mut self) -> Option<TransactionId> {
3217        let mut count = 0;
3218        let mut transactions = self.undo_stack.iter();
3219        if let Some(mut transaction) = transactions.next_back() {
3220            while let Some(prev_transaction) = transactions.next_back() {
3221                if !prev_transaction.suppress_grouping
3222                    && transaction.first_edit_at - prev_transaction.last_edit_at
3223                        <= self.group_interval
3224                {
3225                    transaction = prev_transaction;
3226                    count += 1;
3227                } else {
3228                    break;
3229                }
3230            }
3231        }
3232        self.group_trailing(count)
3233    }
3234
3235    fn group_until(&mut self, transaction_id: TransactionId) {
3236        let mut count = 0;
3237        for transaction in self.undo_stack.iter().rev() {
3238            if transaction.id == transaction_id {
3239                self.group_trailing(count);
3240                break;
3241            } else if transaction.suppress_grouping {
3242                break;
3243            } else {
3244                count += 1;
3245            }
3246        }
3247    }
3248
3249    fn group_trailing(&mut self, n: usize) -> Option<TransactionId> {
3250        let new_len = self.undo_stack.len() - n;
3251        let (transactions_to_keep, transactions_to_merge) = self.undo_stack.split_at_mut(new_len);
3252        if let Some(last_transaction) = transactions_to_keep.last_mut() {
3253            if let Some(transaction) = transactions_to_merge.last() {
3254                last_transaction.last_edit_at = transaction.last_edit_at;
3255            }
3256            for to_merge in transactions_to_merge {
3257                for (buffer_id, transaction_id) in &to_merge.buffer_transactions {
3258                    last_transaction
3259                        .buffer_transactions
3260                        .entry(*buffer_id)
3261                        .or_insert(*transaction_id);
3262                }
3263            }
3264        }
3265
3266        self.undo_stack.truncate(new_len);
3267        self.undo_stack.last().map(|t| t.id)
3268    }
3269}
3270
3271impl Excerpt {
3272    fn new(
3273        id: ExcerptId,
3274        locator: Locator,
3275        buffer_id: u64,
3276        buffer: BufferSnapshot,
3277        range: ExcerptRange<text::Anchor>,
3278        has_trailing_newline: bool,
3279    ) -> Self {
3280        Excerpt {
3281            id,
3282            locator,
3283            max_buffer_row: range.context.end.to_point(&buffer).row,
3284            text_summary: buffer
3285                .text_summary_for_range::<TextSummary, _>(range.context.to_offset(&buffer)),
3286            buffer_id,
3287            buffer,
3288            range,
3289            has_trailing_newline,
3290        }
3291    }
3292
3293    fn chunks_in_range(&self, range: Range<usize>, language_aware: bool) -> ExcerptChunks {
3294        let content_start = self.range.context.start.to_offset(&self.buffer);
3295        let chunks_start = content_start + range.start;
3296        let chunks_end = content_start + cmp::min(range.end, self.text_summary.len);
3297
3298        let footer_height = if self.has_trailing_newline
3299            && range.start <= self.text_summary.len
3300            && range.end > self.text_summary.len
3301        {
3302            1
3303        } else {
3304            0
3305        };
3306
3307        let content_chunks = self.buffer.chunks(chunks_start..chunks_end, language_aware);
3308
3309        ExcerptChunks {
3310            content_chunks,
3311            footer_height,
3312        }
3313    }
3314
3315    fn bytes_in_range(&self, range: Range<usize>) -> ExcerptBytes {
3316        let content_start = self.range.context.start.to_offset(&self.buffer);
3317        let bytes_start = content_start + range.start;
3318        let bytes_end = content_start + cmp::min(range.end, self.text_summary.len);
3319        let footer_height = if self.has_trailing_newline
3320            && range.start <= self.text_summary.len
3321            && range.end > self.text_summary.len
3322        {
3323            1
3324        } else {
3325            0
3326        };
3327        let content_bytes = self.buffer.bytes_in_range(bytes_start..bytes_end);
3328
3329        ExcerptBytes {
3330            content_bytes,
3331            footer_height,
3332        }
3333    }
3334
3335    fn clip_anchor(&self, text_anchor: text::Anchor) -> text::Anchor {
3336        if text_anchor
3337            .cmp(&self.range.context.start, &self.buffer)
3338            .is_lt()
3339        {
3340            self.range.context.start
3341        } else if text_anchor
3342            .cmp(&self.range.context.end, &self.buffer)
3343            .is_gt()
3344        {
3345            self.range.context.end
3346        } else {
3347            text_anchor
3348        }
3349    }
3350
3351    fn contains(&self, anchor: &Anchor) -> bool {
3352        Some(self.buffer_id) == anchor.buffer_id
3353            && self
3354                .range
3355                .context
3356                .start
3357                .cmp(&anchor.text_anchor, &self.buffer)
3358                .is_le()
3359            && self
3360                .range
3361                .context
3362                .end
3363                .cmp(&anchor.text_anchor, &self.buffer)
3364                .is_ge()
3365    }
3366}
3367
3368impl ExcerptId {
3369    pub fn min() -> Self {
3370        Self(0)
3371    }
3372
3373    pub fn max() -> Self {
3374        Self(usize::MAX)
3375    }
3376
3377    pub fn to_proto(&self) -> u64 {
3378        self.0 as _
3379    }
3380
3381    pub fn from_proto(proto: u64) -> Self {
3382        Self(proto as _)
3383    }
3384
3385    pub fn cmp(&self, other: &Self, snapshot: &MultiBufferSnapshot) -> cmp::Ordering {
3386        let a = snapshot.excerpt_locator_for_id(*self);
3387        let b = snapshot.excerpt_locator_for_id(*other);
3388        a.cmp(&b).then_with(|| self.0.cmp(&other.0))
3389    }
3390}
3391
3392impl Into<usize> for ExcerptId {
3393    fn into(self) -> usize {
3394        self.0
3395    }
3396}
3397
3398impl fmt::Debug for Excerpt {
3399    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3400        f.debug_struct("Excerpt")
3401            .field("id", &self.id)
3402            .field("locator", &self.locator)
3403            .field("buffer_id", &self.buffer_id)
3404            .field("range", &self.range)
3405            .field("text_summary", &self.text_summary)
3406            .field("has_trailing_newline", &self.has_trailing_newline)
3407            .finish()
3408    }
3409}
3410
3411impl sum_tree::Item for Excerpt {
3412    type Summary = ExcerptSummary;
3413
3414    fn summary(&self) -> Self::Summary {
3415        let mut text = self.text_summary.clone();
3416        if self.has_trailing_newline {
3417            text += TextSummary::from("\n");
3418        }
3419        ExcerptSummary {
3420            excerpt_id: self.id,
3421            excerpt_locator: self.locator.clone(),
3422            max_buffer_row: self.max_buffer_row,
3423            text,
3424        }
3425    }
3426}
3427
3428impl sum_tree::Item for ExcerptIdMapping {
3429    type Summary = ExcerptId;
3430
3431    fn summary(&self) -> Self::Summary {
3432        self.id
3433    }
3434}
3435
3436impl sum_tree::KeyedItem for ExcerptIdMapping {
3437    type Key = ExcerptId;
3438
3439    fn key(&self) -> Self::Key {
3440        self.id
3441    }
3442}
3443
3444impl sum_tree::Summary for ExcerptId {
3445    type Context = ();
3446
3447    fn add_summary(&mut self, other: &Self, _: &()) {
3448        *self = *other;
3449    }
3450}
3451
3452impl sum_tree::Summary for ExcerptSummary {
3453    type Context = ();
3454
3455    fn add_summary(&mut self, summary: &Self, _: &()) {
3456        debug_assert!(summary.excerpt_locator > self.excerpt_locator);
3457        self.excerpt_locator = summary.excerpt_locator.clone();
3458        self.text.add_summary(&summary.text, &());
3459        self.max_buffer_row = cmp::max(self.max_buffer_row, summary.max_buffer_row);
3460    }
3461}
3462
3463impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for TextSummary {
3464    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
3465        *self += &summary.text;
3466    }
3467}
3468
3469impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for usize {
3470    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
3471        *self += summary.text.len;
3472    }
3473}
3474
3475impl<'a> sum_tree::SeekTarget<'a, ExcerptSummary, ExcerptSummary> for usize {
3476    fn cmp(&self, cursor_location: &ExcerptSummary, _: &()) -> cmp::Ordering {
3477        Ord::cmp(self, &cursor_location.text.len)
3478    }
3479}
3480
3481impl<'a> sum_tree::SeekTarget<'a, ExcerptSummary, Option<&'a Locator>> for Locator {
3482    fn cmp(&self, cursor_location: &Option<&'a Locator>, _: &()) -> cmp::Ordering {
3483        Ord::cmp(&Some(self), cursor_location)
3484    }
3485}
3486
3487impl<'a> sum_tree::SeekTarget<'a, ExcerptSummary, ExcerptSummary> for Locator {
3488    fn cmp(&self, cursor_location: &ExcerptSummary, _: &()) -> cmp::Ordering {
3489        Ord::cmp(self, &cursor_location.excerpt_locator)
3490    }
3491}
3492
3493impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for OffsetUtf16 {
3494    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
3495        *self += summary.text.len_utf16;
3496    }
3497}
3498
3499impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for Point {
3500    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
3501        *self += summary.text.lines;
3502    }
3503}
3504
3505impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for PointUtf16 {
3506    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
3507        *self += summary.text.lines_utf16()
3508    }
3509}
3510
3511impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for Option<&'a Locator> {
3512    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
3513        *self = Some(&summary.excerpt_locator);
3514    }
3515}
3516
3517impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for Option<ExcerptId> {
3518    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
3519        *self = Some(summary.excerpt_id);
3520    }
3521}
3522
3523impl<'a> MultiBufferRows<'a> {
3524    pub fn seek(&mut self, row: u32) {
3525        self.buffer_row_range = 0..0;
3526
3527        self.excerpts
3528            .seek_forward(&Point::new(row, 0), Bias::Right, &());
3529        if self.excerpts.item().is_none() {
3530            self.excerpts.prev(&());
3531
3532            if self.excerpts.item().is_none() && row == 0 {
3533                self.buffer_row_range = 0..1;
3534                return;
3535            }
3536        }
3537
3538        if let Some(excerpt) = self.excerpts.item() {
3539            let overshoot = row - self.excerpts.start().row;
3540            let excerpt_start = excerpt.range.context.start.to_point(&excerpt.buffer).row;
3541            self.buffer_row_range.start = excerpt_start + overshoot;
3542            self.buffer_row_range.end = excerpt_start + excerpt.text_summary.lines.row + 1;
3543        }
3544    }
3545}
3546
3547impl<'a> Iterator for MultiBufferRows<'a> {
3548    type Item = Option<u32>;
3549
3550    fn next(&mut self) -> Option<Self::Item> {
3551        loop {
3552            if !self.buffer_row_range.is_empty() {
3553                let row = Some(self.buffer_row_range.start);
3554                self.buffer_row_range.start += 1;
3555                return Some(row);
3556            }
3557            self.excerpts.item()?;
3558            self.excerpts.next(&());
3559            let excerpt = self.excerpts.item()?;
3560            self.buffer_row_range.start = excerpt.range.context.start.to_point(&excerpt.buffer).row;
3561            self.buffer_row_range.end =
3562                self.buffer_row_range.start + excerpt.text_summary.lines.row + 1;
3563        }
3564    }
3565}
3566
3567impl<'a> MultiBufferChunks<'a> {
3568    pub fn offset(&self) -> usize {
3569        self.range.start
3570    }
3571
3572    pub fn seek(&mut self, offset: usize) {
3573        self.range.start = offset;
3574        self.excerpts.seek(&offset, Bias::Right, &());
3575        if let Some(excerpt) = self.excerpts.item() {
3576            self.excerpt_chunks = Some(excerpt.chunks_in_range(
3577                self.range.start - self.excerpts.start()..self.range.end - self.excerpts.start(),
3578                self.language_aware,
3579            ));
3580        } else {
3581            self.excerpt_chunks = None;
3582        }
3583    }
3584}
3585
3586impl<'a> Iterator for MultiBufferChunks<'a> {
3587    type Item = Chunk<'a>;
3588
3589    fn next(&mut self) -> Option<Self::Item> {
3590        if self.range.is_empty() {
3591            None
3592        } else if let Some(chunk) = self.excerpt_chunks.as_mut()?.next() {
3593            self.range.start += chunk.text.len();
3594            Some(chunk)
3595        } else {
3596            self.excerpts.next(&());
3597            let excerpt = self.excerpts.item()?;
3598            self.excerpt_chunks = Some(excerpt.chunks_in_range(
3599                0..self.range.end - self.excerpts.start(),
3600                self.language_aware,
3601            ));
3602            self.next()
3603        }
3604    }
3605}
3606
3607impl<'a> MultiBufferBytes<'a> {
3608    fn consume(&mut self, len: usize) {
3609        self.range.start += len;
3610        self.chunk = &self.chunk[len..];
3611
3612        if !self.range.is_empty() && self.chunk.is_empty() {
3613            if let Some(chunk) = self.excerpt_bytes.as_mut().and_then(|bytes| bytes.next()) {
3614                self.chunk = chunk;
3615            } else {
3616                self.excerpts.next(&());
3617                if let Some(excerpt) = self.excerpts.item() {
3618                    let mut excerpt_bytes =
3619                        excerpt.bytes_in_range(0..self.range.end - self.excerpts.start());
3620                    self.chunk = excerpt_bytes.next().unwrap();
3621                    self.excerpt_bytes = Some(excerpt_bytes);
3622                }
3623            }
3624        }
3625    }
3626}
3627
3628impl<'a> Iterator for MultiBufferBytes<'a> {
3629    type Item = &'a [u8];
3630
3631    fn next(&mut self) -> Option<Self::Item> {
3632        let chunk = self.chunk;
3633        if chunk.is_empty() {
3634            None
3635        } else {
3636            self.consume(chunk.len());
3637            Some(chunk)
3638        }
3639    }
3640}
3641
3642impl<'a> io::Read for MultiBufferBytes<'a> {
3643    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
3644        let len = cmp::min(buf.len(), self.chunk.len());
3645        buf[..len].copy_from_slice(&self.chunk[..len]);
3646        if len > 0 {
3647            self.consume(len);
3648        }
3649        Ok(len)
3650    }
3651}
3652
3653impl<'a> Iterator for ExcerptBytes<'a> {
3654    type Item = &'a [u8];
3655
3656    fn next(&mut self) -> Option<Self::Item> {
3657        if let Some(chunk) = self.content_bytes.next() {
3658            if !chunk.is_empty() {
3659                return Some(chunk);
3660            }
3661        }
3662
3663        if self.footer_height > 0 {
3664            let result = &NEWLINES[..self.footer_height];
3665            self.footer_height = 0;
3666            return Some(result);
3667        }
3668
3669        None
3670    }
3671}
3672
3673impl<'a> Iterator for ExcerptChunks<'a> {
3674    type Item = Chunk<'a>;
3675
3676    fn next(&mut self) -> Option<Self::Item> {
3677        if let Some(chunk) = self.content_chunks.next() {
3678            return Some(chunk);
3679        }
3680
3681        if self.footer_height > 0 {
3682            let text = unsafe { str::from_utf8_unchecked(&NEWLINES[..self.footer_height]) };
3683            self.footer_height = 0;
3684            return Some(Chunk {
3685                text,
3686                ..Default::default()
3687            });
3688        }
3689
3690        None
3691    }
3692}
3693
3694impl ToOffset for Point {
3695    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
3696        snapshot.point_to_offset(*self)
3697    }
3698}
3699
3700impl ToOffset for usize {
3701    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
3702        assert!(*self <= snapshot.len(), "offset is out of range");
3703        *self
3704    }
3705}
3706
3707impl ToOffset for OffsetUtf16 {
3708    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
3709        snapshot.offset_utf16_to_offset(*self)
3710    }
3711}
3712
3713impl ToOffset for PointUtf16 {
3714    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
3715        snapshot.point_utf16_to_offset(*self)
3716    }
3717}
3718
3719impl ToOffsetUtf16 for OffsetUtf16 {
3720    fn to_offset_utf16(&self, _snapshot: &MultiBufferSnapshot) -> OffsetUtf16 {
3721        *self
3722    }
3723}
3724
3725impl ToOffsetUtf16 for usize {
3726    fn to_offset_utf16(&self, snapshot: &MultiBufferSnapshot) -> OffsetUtf16 {
3727        snapshot.offset_to_offset_utf16(*self)
3728    }
3729}
3730
3731impl ToPoint for usize {
3732    fn to_point<'a>(&self, snapshot: &MultiBufferSnapshot) -> Point {
3733        snapshot.offset_to_point(*self)
3734    }
3735}
3736
3737impl ToPoint for Point {
3738    fn to_point<'a>(&self, _: &MultiBufferSnapshot) -> Point {
3739        *self
3740    }
3741}
3742
3743impl ToPointUtf16 for usize {
3744    fn to_point_utf16<'a>(&self, snapshot: &MultiBufferSnapshot) -> PointUtf16 {
3745        snapshot.offset_to_point_utf16(*self)
3746    }
3747}
3748
3749impl ToPointUtf16 for Point {
3750    fn to_point_utf16<'a>(&self, snapshot: &MultiBufferSnapshot) -> PointUtf16 {
3751        snapshot.point_to_point_utf16(*self)
3752    }
3753}
3754
3755impl ToPointUtf16 for PointUtf16 {
3756    fn to_point_utf16<'a>(&self, _: &MultiBufferSnapshot) -> PointUtf16 {
3757        *self
3758    }
3759}
3760
3761fn build_excerpt_ranges<T>(
3762    buffer: &BufferSnapshot,
3763    ranges: &[Range<T>],
3764    context_line_count: u32,
3765) -> (Vec<ExcerptRange<Point>>, Vec<usize>)
3766where
3767    T: text::ToPoint,
3768{
3769    let max_point = buffer.max_point();
3770    let mut range_counts = Vec::new();
3771    let mut excerpt_ranges = Vec::new();
3772    let mut range_iter = ranges
3773        .iter()
3774        .map(|range| range.start.to_point(buffer)..range.end.to_point(buffer))
3775        .peekable();
3776    while let Some(range) = range_iter.next() {
3777        let excerpt_start = Point::new(range.start.row.saturating_sub(context_line_count), 0);
3778        let mut excerpt_end = Point::new(range.end.row + 1 + context_line_count, 0).min(max_point);
3779        let mut ranges_in_excerpt = 1;
3780
3781        while let Some(next_range) = range_iter.peek() {
3782            if next_range.start.row <= excerpt_end.row + context_line_count {
3783                excerpt_end =
3784                    Point::new(next_range.end.row + 1 + context_line_count, 0).min(max_point);
3785                ranges_in_excerpt += 1;
3786                range_iter.next();
3787            } else {
3788                break;
3789            }
3790        }
3791
3792        excerpt_ranges.push(ExcerptRange {
3793            context: excerpt_start..excerpt_end,
3794            primary: Some(range),
3795        });
3796        range_counts.push(ranges_in_excerpt);
3797    }
3798
3799    (excerpt_ranges, range_counts)
3800}
3801
3802#[cfg(test)]
3803mod tests {
3804    use super::*;
3805    use futures::StreamExt;
3806    use gpui::{AppContext, TestAppContext};
3807    use language::{Buffer, Rope};
3808    use rand::prelude::*;
3809    use settings::Settings;
3810    use std::{env, rc::Rc};
3811    use unindent::Unindent;
3812
3813    use util::test::sample_text;
3814
3815    #[gpui::test]
3816    fn test_singleton(cx: &mut AppContext) {
3817        let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'a'), cx));
3818        let multibuffer = cx.add_model(|cx| MultiBuffer::singleton(buffer.clone(), cx));
3819
3820        let snapshot = multibuffer.read(cx).snapshot(cx);
3821        assert_eq!(snapshot.text(), buffer.read(cx).text());
3822
3823        assert_eq!(
3824            snapshot.buffer_rows(0).collect::<Vec<_>>(),
3825            (0..buffer.read(cx).row_count())
3826                .map(Some)
3827                .collect::<Vec<_>>()
3828        );
3829
3830        buffer.update(cx, |buffer, cx| buffer.edit([(1..3, "XXX\n")], None, cx));
3831        let snapshot = multibuffer.read(cx).snapshot(cx);
3832
3833        assert_eq!(snapshot.text(), buffer.read(cx).text());
3834        assert_eq!(
3835            snapshot.buffer_rows(0).collect::<Vec<_>>(),
3836            (0..buffer.read(cx).row_count())
3837                .map(Some)
3838                .collect::<Vec<_>>()
3839        );
3840    }
3841
3842    #[gpui::test]
3843    fn test_remote(cx: &mut AppContext) {
3844        let host_buffer = cx.add_model(|cx| Buffer::new(0, "a", cx));
3845        let guest_buffer = cx.add_model(|cx| {
3846            let state = host_buffer.read(cx).to_proto();
3847            let ops = cx
3848                .background()
3849                .block(host_buffer.read(cx).serialize_ops(None, cx));
3850            let mut buffer = Buffer::from_proto(1, state, None).unwrap();
3851            buffer
3852                .apply_ops(
3853                    ops.into_iter()
3854                        .map(|op| language::proto::deserialize_operation(op).unwrap()),
3855                    cx,
3856                )
3857                .unwrap();
3858            buffer
3859        });
3860        let multibuffer = cx.add_model(|cx| MultiBuffer::singleton(guest_buffer.clone(), cx));
3861        let snapshot = multibuffer.read(cx).snapshot(cx);
3862        assert_eq!(snapshot.text(), "a");
3863
3864        guest_buffer.update(cx, |buffer, cx| buffer.edit([(1..1, "b")], None, cx));
3865        let snapshot = multibuffer.read(cx).snapshot(cx);
3866        assert_eq!(snapshot.text(), "ab");
3867
3868        guest_buffer.update(cx, |buffer, cx| buffer.edit([(2..2, "c")], None, cx));
3869        let snapshot = multibuffer.read(cx).snapshot(cx);
3870        assert_eq!(snapshot.text(), "abc");
3871    }
3872
3873    #[gpui::test]
3874    fn test_excerpt_boundaries_and_clipping(cx: &mut AppContext) {
3875        let buffer_1 = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'a'), cx));
3876        let buffer_2 = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'g'), cx));
3877        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
3878
3879        let events = Rc::new(RefCell::new(Vec::<Event>::new()));
3880        multibuffer.update(cx, |_, cx| {
3881            let events = events.clone();
3882            cx.subscribe(&multibuffer, move |_, _, event, _| {
3883                if let Event::Edited = event {
3884                    events.borrow_mut().push(event.clone())
3885                }
3886            })
3887            .detach();
3888        });
3889
3890        let subscription = multibuffer.update(cx, |multibuffer, cx| {
3891            let subscription = multibuffer.subscribe();
3892            multibuffer.push_excerpts(
3893                buffer_1.clone(),
3894                [ExcerptRange {
3895                    context: Point::new(1, 2)..Point::new(2, 5),
3896                    primary: None,
3897                }],
3898                cx,
3899            );
3900            assert_eq!(
3901                subscription.consume().into_inner(),
3902                [Edit {
3903                    old: 0..0,
3904                    new: 0..10
3905                }]
3906            );
3907
3908            multibuffer.push_excerpts(
3909                buffer_1.clone(),
3910                [ExcerptRange {
3911                    context: Point::new(3, 3)..Point::new(4, 4),
3912                    primary: None,
3913                }],
3914                cx,
3915            );
3916            multibuffer.push_excerpts(
3917                buffer_2.clone(),
3918                [ExcerptRange {
3919                    context: Point::new(3, 1)..Point::new(3, 3),
3920                    primary: None,
3921                }],
3922                cx,
3923            );
3924            assert_eq!(
3925                subscription.consume().into_inner(),
3926                [Edit {
3927                    old: 10..10,
3928                    new: 10..22
3929                }]
3930            );
3931
3932            subscription
3933        });
3934
3935        // Adding excerpts emits an edited event.
3936        assert_eq!(
3937            events.borrow().as_slice(),
3938            &[Event::Edited, Event::Edited, Event::Edited]
3939        );
3940
3941        let snapshot = multibuffer.read(cx).snapshot(cx);
3942        assert_eq!(
3943            snapshot.text(),
3944            concat!(
3945                "bbbb\n",  // Preserve newlines
3946                "ccccc\n", //
3947                "ddd\n",   //
3948                "eeee\n",  //
3949                "jj"       //
3950            )
3951        );
3952        assert_eq!(
3953            snapshot.buffer_rows(0).collect::<Vec<_>>(),
3954            [Some(1), Some(2), Some(3), Some(4), Some(3)]
3955        );
3956        assert_eq!(
3957            snapshot.buffer_rows(2).collect::<Vec<_>>(),
3958            [Some(3), Some(4), Some(3)]
3959        );
3960        assert_eq!(snapshot.buffer_rows(4).collect::<Vec<_>>(), [Some(3)]);
3961        assert_eq!(snapshot.buffer_rows(5).collect::<Vec<_>>(), []);
3962
3963        assert_eq!(
3964            boundaries_in_range(Point::new(0, 0)..Point::new(4, 2), &snapshot),
3965            &[
3966                (0, "bbbb\nccccc".to_string(), true),
3967                (2, "ddd\neeee".to_string(), false),
3968                (4, "jj".to_string(), true),
3969            ]
3970        );
3971        assert_eq!(
3972            boundaries_in_range(Point::new(0, 0)..Point::new(2, 0), &snapshot),
3973            &[(0, "bbbb\nccccc".to_string(), true)]
3974        );
3975        assert_eq!(
3976            boundaries_in_range(Point::new(1, 0)..Point::new(1, 5), &snapshot),
3977            &[]
3978        );
3979        assert_eq!(
3980            boundaries_in_range(Point::new(1, 0)..Point::new(2, 0), &snapshot),
3981            &[]
3982        );
3983        assert_eq!(
3984            boundaries_in_range(Point::new(1, 0)..Point::new(4, 0), &snapshot),
3985            &[(2, "ddd\neeee".to_string(), false)]
3986        );
3987        assert_eq!(
3988            boundaries_in_range(Point::new(1, 0)..Point::new(4, 0), &snapshot),
3989            &[(2, "ddd\neeee".to_string(), false)]
3990        );
3991        assert_eq!(
3992            boundaries_in_range(Point::new(2, 0)..Point::new(3, 0), &snapshot),
3993            &[(2, "ddd\neeee".to_string(), false)]
3994        );
3995        assert_eq!(
3996            boundaries_in_range(Point::new(4, 0)..Point::new(4, 2), &snapshot),
3997            &[(4, "jj".to_string(), true)]
3998        );
3999        assert_eq!(
4000            boundaries_in_range(Point::new(4, 2)..Point::new(4, 2), &snapshot),
4001            &[]
4002        );
4003
4004        buffer_1.update(cx, |buffer, cx| {
4005            let text = "\n";
4006            buffer.edit(
4007                [
4008                    (Point::new(0, 0)..Point::new(0, 0), text),
4009                    (Point::new(2, 1)..Point::new(2, 3), text),
4010                ],
4011                None,
4012                cx,
4013            );
4014        });
4015
4016        let snapshot = multibuffer.read(cx).snapshot(cx);
4017        assert_eq!(
4018            snapshot.text(),
4019            concat!(
4020                "bbbb\n", // Preserve newlines
4021                "c\n",    //
4022                "cc\n",   //
4023                "ddd\n",  //
4024                "eeee\n", //
4025                "jj"      //
4026            )
4027        );
4028
4029        assert_eq!(
4030            subscription.consume().into_inner(),
4031            [Edit {
4032                old: 6..8,
4033                new: 6..7
4034            }]
4035        );
4036
4037        let snapshot = multibuffer.read(cx).snapshot(cx);
4038        assert_eq!(
4039            snapshot.clip_point(Point::new(0, 5), Bias::Left),
4040            Point::new(0, 4)
4041        );
4042        assert_eq!(
4043            snapshot.clip_point(Point::new(0, 5), Bias::Right),
4044            Point::new(0, 4)
4045        );
4046        assert_eq!(
4047            snapshot.clip_point(Point::new(5, 1), Bias::Right),
4048            Point::new(5, 1)
4049        );
4050        assert_eq!(
4051            snapshot.clip_point(Point::new(5, 2), Bias::Right),
4052            Point::new(5, 2)
4053        );
4054        assert_eq!(
4055            snapshot.clip_point(Point::new(5, 3), Bias::Right),
4056            Point::new(5, 2)
4057        );
4058
4059        let snapshot = multibuffer.update(cx, |multibuffer, cx| {
4060            let (buffer_2_excerpt_id, _) =
4061                multibuffer.excerpts_for_buffer(&buffer_2, cx)[0].clone();
4062            multibuffer.remove_excerpts([buffer_2_excerpt_id], cx);
4063            multibuffer.snapshot(cx)
4064        });
4065
4066        assert_eq!(
4067            snapshot.text(),
4068            concat!(
4069                "bbbb\n", // Preserve newlines
4070                "c\n",    //
4071                "cc\n",   //
4072                "ddd\n",  //
4073                "eeee",   //
4074            )
4075        );
4076
4077        fn boundaries_in_range(
4078            range: Range<Point>,
4079            snapshot: &MultiBufferSnapshot,
4080        ) -> Vec<(u32, String, bool)> {
4081            snapshot
4082                .excerpt_boundaries_in_range(range)
4083                .map(|boundary| {
4084                    (
4085                        boundary.row,
4086                        boundary
4087                            .buffer
4088                            .text_for_range(boundary.range.context)
4089                            .collect::<String>(),
4090                        boundary.starts_new_buffer,
4091                    )
4092                })
4093                .collect::<Vec<_>>()
4094        }
4095    }
4096
4097    #[gpui::test]
4098    fn test_excerpt_events(cx: &mut AppContext) {
4099        let buffer_1 = cx.add_model(|cx| Buffer::new(0, sample_text(10, 3, 'a'), cx));
4100        let buffer_2 = cx.add_model(|cx| Buffer::new(0, sample_text(10, 3, 'm'), cx));
4101
4102        let leader_multibuffer = cx.add_model(|_| MultiBuffer::new(0));
4103        let follower_multibuffer = cx.add_model(|_| MultiBuffer::new(0));
4104
4105        follower_multibuffer.update(cx, |_, cx| {
4106            cx.subscribe(&leader_multibuffer, |follower, _, event, cx| {
4107                match event.clone() {
4108                    Event::ExcerptsAdded {
4109                        buffer,
4110                        predecessor,
4111                        excerpts,
4112                    } => follower.insert_excerpts_with_ids_after(predecessor, buffer, excerpts, cx),
4113                    Event::ExcerptsRemoved { ids } => follower.remove_excerpts(ids, cx),
4114                    _ => {}
4115                }
4116            })
4117            .detach();
4118        });
4119
4120        leader_multibuffer.update(cx, |leader, cx| {
4121            leader.push_excerpts(
4122                buffer_1.clone(),
4123                [
4124                    ExcerptRange {
4125                        context: 0..8,
4126                        primary: None,
4127                    },
4128                    ExcerptRange {
4129                        context: 12..16,
4130                        primary: None,
4131                    },
4132                ],
4133                cx,
4134            );
4135            leader.insert_excerpts_after(
4136                leader.excerpt_ids()[0],
4137                buffer_2.clone(),
4138                [
4139                    ExcerptRange {
4140                        context: 0..5,
4141                        primary: None,
4142                    },
4143                    ExcerptRange {
4144                        context: 10..15,
4145                        primary: None,
4146                    },
4147                ],
4148                cx,
4149            )
4150        });
4151        assert_eq!(
4152            leader_multibuffer.read(cx).snapshot(cx).text(),
4153            follower_multibuffer.read(cx).snapshot(cx).text(),
4154        );
4155
4156        leader_multibuffer.update(cx, |leader, cx| {
4157            let excerpt_ids = leader.excerpt_ids();
4158            leader.remove_excerpts([excerpt_ids[1], excerpt_ids[3]], cx);
4159        });
4160        assert_eq!(
4161            leader_multibuffer.read(cx).snapshot(cx).text(),
4162            follower_multibuffer.read(cx).snapshot(cx).text(),
4163        );
4164
4165        leader_multibuffer.update(cx, |leader, cx| {
4166            leader.clear(cx);
4167        });
4168        assert_eq!(
4169            leader_multibuffer.read(cx).snapshot(cx).text(),
4170            follower_multibuffer.read(cx).snapshot(cx).text(),
4171        );
4172    }
4173
4174    #[gpui::test]
4175    fn test_push_excerpts_with_context_lines(cx: &mut AppContext) {
4176        let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(20, 3, 'a'), cx));
4177        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
4178        let anchor_ranges = multibuffer.update(cx, |multibuffer, cx| {
4179            multibuffer.push_excerpts_with_context_lines(
4180                buffer.clone(),
4181                vec![
4182                    Point::new(3, 2)..Point::new(4, 2),
4183                    Point::new(7, 1)..Point::new(7, 3),
4184                    Point::new(15, 0)..Point::new(15, 0),
4185                ],
4186                2,
4187                cx,
4188            )
4189        });
4190
4191        let snapshot = multibuffer.read(cx).snapshot(cx);
4192        assert_eq!(
4193            snapshot.text(),
4194            "bbb\nccc\nddd\neee\nfff\nggg\nhhh\niii\njjj\n\nnnn\nooo\nppp\nqqq\nrrr\n"
4195        );
4196
4197        assert_eq!(
4198            anchor_ranges
4199                .iter()
4200                .map(|range| range.to_point(&snapshot))
4201                .collect::<Vec<_>>(),
4202            vec![
4203                Point::new(2, 2)..Point::new(3, 2),
4204                Point::new(6, 1)..Point::new(6, 3),
4205                Point::new(12, 0)..Point::new(12, 0)
4206            ]
4207        );
4208    }
4209
4210    #[gpui::test]
4211    async fn test_stream_excerpts_with_context_lines(cx: &mut TestAppContext) {
4212        let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(20, 3, 'a'), cx));
4213        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
4214        let (task, anchor_ranges) = multibuffer.update(cx, |multibuffer, cx| {
4215            let snapshot = buffer.read(cx);
4216            let ranges = vec![
4217                snapshot.anchor_before(Point::new(3, 2))..snapshot.anchor_before(Point::new(4, 2)),
4218                snapshot.anchor_before(Point::new(7, 1))..snapshot.anchor_before(Point::new(7, 3)),
4219                snapshot.anchor_before(Point::new(15, 0))
4220                    ..snapshot.anchor_before(Point::new(15, 0)),
4221            ];
4222            multibuffer.stream_excerpts_with_context_lines(vec![(buffer.clone(), ranges)], 2, cx)
4223        });
4224
4225        let anchor_ranges = anchor_ranges.collect::<Vec<_>>().await;
4226        // Ensure task is finished when stream completes.
4227        task.await;
4228
4229        let snapshot = multibuffer.read_with(cx, |multibuffer, cx| multibuffer.snapshot(cx));
4230        assert_eq!(
4231            snapshot.text(),
4232            "bbb\nccc\nddd\neee\nfff\nggg\nhhh\niii\njjj\n\nnnn\nooo\nppp\nqqq\nrrr\n"
4233        );
4234
4235        assert_eq!(
4236            anchor_ranges
4237                .iter()
4238                .map(|range| range.to_point(&snapshot))
4239                .collect::<Vec<_>>(),
4240            vec![
4241                Point::new(2, 2)..Point::new(3, 2),
4242                Point::new(6, 1)..Point::new(6, 3),
4243                Point::new(12, 0)..Point::new(12, 0)
4244            ]
4245        );
4246    }
4247
4248    #[gpui::test]
4249    fn test_empty_multibuffer(cx: &mut AppContext) {
4250        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
4251
4252        let snapshot = multibuffer.read(cx).snapshot(cx);
4253        assert_eq!(snapshot.text(), "");
4254        assert_eq!(snapshot.buffer_rows(0).collect::<Vec<_>>(), &[Some(0)]);
4255        assert_eq!(snapshot.buffer_rows(1).collect::<Vec<_>>(), &[]);
4256    }
4257
4258    #[gpui::test]
4259    fn test_singleton_multibuffer_anchors(cx: &mut AppContext) {
4260        let buffer = cx.add_model(|cx| Buffer::new(0, "abcd", cx));
4261        let multibuffer = cx.add_model(|cx| MultiBuffer::singleton(buffer.clone(), cx));
4262        let old_snapshot = multibuffer.read(cx).snapshot(cx);
4263        buffer.update(cx, |buffer, cx| {
4264            buffer.edit([(0..0, "X")], None, cx);
4265            buffer.edit([(5..5, "Y")], None, cx);
4266        });
4267        let new_snapshot = multibuffer.read(cx).snapshot(cx);
4268
4269        assert_eq!(old_snapshot.text(), "abcd");
4270        assert_eq!(new_snapshot.text(), "XabcdY");
4271
4272        assert_eq!(old_snapshot.anchor_before(0).to_offset(&new_snapshot), 0);
4273        assert_eq!(old_snapshot.anchor_after(0).to_offset(&new_snapshot), 1);
4274        assert_eq!(old_snapshot.anchor_before(4).to_offset(&new_snapshot), 5);
4275        assert_eq!(old_snapshot.anchor_after(4).to_offset(&new_snapshot), 6);
4276    }
4277
4278    #[gpui::test]
4279    fn test_multibuffer_anchors(cx: &mut AppContext) {
4280        let buffer_1 = cx.add_model(|cx| Buffer::new(0, "abcd", cx));
4281        let buffer_2 = cx.add_model(|cx| Buffer::new(0, "efghi", cx));
4282        let multibuffer = cx.add_model(|cx| {
4283            let mut multibuffer = MultiBuffer::new(0);
4284            multibuffer.push_excerpts(
4285                buffer_1.clone(),
4286                [ExcerptRange {
4287                    context: 0..4,
4288                    primary: None,
4289                }],
4290                cx,
4291            );
4292            multibuffer.push_excerpts(
4293                buffer_2.clone(),
4294                [ExcerptRange {
4295                    context: 0..5,
4296                    primary: None,
4297                }],
4298                cx,
4299            );
4300            multibuffer
4301        });
4302        let old_snapshot = multibuffer.read(cx).snapshot(cx);
4303
4304        assert_eq!(old_snapshot.anchor_before(0).to_offset(&old_snapshot), 0);
4305        assert_eq!(old_snapshot.anchor_after(0).to_offset(&old_snapshot), 0);
4306        assert_eq!(Anchor::min().to_offset(&old_snapshot), 0);
4307        assert_eq!(Anchor::min().to_offset(&old_snapshot), 0);
4308        assert_eq!(Anchor::max().to_offset(&old_snapshot), 10);
4309        assert_eq!(Anchor::max().to_offset(&old_snapshot), 10);
4310
4311        buffer_1.update(cx, |buffer, cx| {
4312            buffer.edit([(0..0, "W")], None, cx);
4313            buffer.edit([(5..5, "X")], None, cx);
4314        });
4315        buffer_2.update(cx, |buffer, cx| {
4316            buffer.edit([(0..0, "Y")], None, cx);
4317            buffer.edit([(6..6, "Z")], None, cx);
4318        });
4319        let new_snapshot = multibuffer.read(cx).snapshot(cx);
4320
4321        assert_eq!(old_snapshot.text(), "abcd\nefghi");
4322        assert_eq!(new_snapshot.text(), "WabcdX\nYefghiZ");
4323
4324        assert_eq!(old_snapshot.anchor_before(0).to_offset(&new_snapshot), 0);
4325        assert_eq!(old_snapshot.anchor_after(0).to_offset(&new_snapshot), 1);
4326        assert_eq!(old_snapshot.anchor_before(1).to_offset(&new_snapshot), 2);
4327        assert_eq!(old_snapshot.anchor_after(1).to_offset(&new_snapshot), 2);
4328        assert_eq!(old_snapshot.anchor_before(2).to_offset(&new_snapshot), 3);
4329        assert_eq!(old_snapshot.anchor_after(2).to_offset(&new_snapshot), 3);
4330        assert_eq!(old_snapshot.anchor_before(5).to_offset(&new_snapshot), 7);
4331        assert_eq!(old_snapshot.anchor_after(5).to_offset(&new_snapshot), 8);
4332        assert_eq!(old_snapshot.anchor_before(10).to_offset(&new_snapshot), 13);
4333        assert_eq!(old_snapshot.anchor_after(10).to_offset(&new_snapshot), 14);
4334    }
4335
4336    #[gpui::test]
4337    fn test_resolving_anchors_after_replacing_their_excerpts(cx: &mut AppContext) {
4338        let buffer_1 = cx.add_model(|cx| Buffer::new(0, "abcd", cx));
4339        let buffer_2 = cx.add_model(|cx| Buffer::new(0, "ABCDEFGHIJKLMNOP", cx));
4340        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
4341
4342        // Create an insertion id in buffer 1 that doesn't exist in buffer 2.
4343        // Add an excerpt from buffer 1 that spans this new insertion.
4344        buffer_1.update(cx, |buffer, cx| buffer.edit([(4..4, "123")], None, cx));
4345        let excerpt_id_1 = multibuffer.update(cx, |multibuffer, cx| {
4346            multibuffer
4347                .push_excerpts(
4348                    buffer_1.clone(),
4349                    [ExcerptRange {
4350                        context: 0..7,
4351                        primary: None,
4352                    }],
4353                    cx,
4354                )
4355                .pop()
4356                .unwrap()
4357        });
4358
4359        let snapshot_1 = multibuffer.read(cx).snapshot(cx);
4360        assert_eq!(snapshot_1.text(), "abcd123");
4361
4362        // Replace the buffer 1 excerpt with new excerpts from buffer 2.
4363        let (excerpt_id_2, excerpt_id_3) = multibuffer.update(cx, |multibuffer, cx| {
4364            multibuffer.remove_excerpts([excerpt_id_1], cx);
4365            let mut ids = multibuffer
4366                .push_excerpts(
4367                    buffer_2.clone(),
4368                    [
4369                        ExcerptRange {
4370                            context: 0..4,
4371                            primary: None,
4372                        },
4373                        ExcerptRange {
4374                            context: 6..10,
4375                            primary: None,
4376                        },
4377                        ExcerptRange {
4378                            context: 12..16,
4379                            primary: None,
4380                        },
4381                    ],
4382                    cx,
4383                )
4384                .into_iter();
4385            (ids.next().unwrap(), ids.next().unwrap())
4386        });
4387        let snapshot_2 = multibuffer.read(cx).snapshot(cx);
4388        assert_eq!(snapshot_2.text(), "ABCD\nGHIJ\nMNOP");
4389
4390        // The old excerpt id doesn't get reused.
4391        assert_ne!(excerpt_id_2, excerpt_id_1);
4392
4393        // Resolve some anchors from the previous snapshot in the new snapshot.
4394        // The current excerpts are from a different buffer, so we don't attempt to
4395        // resolve the old text anchor in the new buffer.
4396        assert_eq!(
4397            snapshot_2.summary_for_anchor::<usize>(&snapshot_1.anchor_before(2)),
4398            0
4399        );
4400        assert_eq!(
4401            snapshot_2.summaries_for_anchors::<usize, _>(&[
4402                snapshot_1.anchor_before(2),
4403                snapshot_1.anchor_after(3)
4404            ]),
4405            vec![0, 0]
4406        );
4407
4408        // Refresh anchors from the old snapshot. The return value indicates that both
4409        // anchors lost their original excerpt.
4410        let refresh =
4411            snapshot_2.refresh_anchors(&[snapshot_1.anchor_before(2), snapshot_1.anchor_after(3)]);
4412        assert_eq!(
4413            refresh,
4414            &[
4415                (0, snapshot_2.anchor_before(0), false),
4416                (1, snapshot_2.anchor_after(0), false),
4417            ]
4418        );
4419
4420        // Replace the middle excerpt with a smaller excerpt in buffer 2,
4421        // that intersects the old excerpt.
4422        let excerpt_id_5 = multibuffer.update(cx, |multibuffer, cx| {
4423            multibuffer.remove_excerpts([excerpt_id_3], cx);
4424            multibuffer
4425                .insert_excerpts_after(
4426                    excerpt_id_2,
4427                    buffer_2.clone(),
4428                    [ExcerptRange {
4429                        context: 5..8,
4430                        primary: None,
4431                    }],
4432                    cx,
4433                )
4434                .pop()
4435                .unwrap()
4436        });
4437
4438        let snapshot_3 = multibuffer.read(cx).snapshot(cx);
4439        assert_eq!(snapshot_3.text(), "ABCD\nFGH\nMNOP");
4440        assert_ne!(excerpt_id_5, excerpt_id_3);
4441
4442        // Resolve some anchors from the previous snapshot in the new snapshot.
4443        // The third anchor can't be resolved, since its excerpt has been removed,
4444        // so it resolves to the same position as its predecessor.
4445        let anchors = [
4446            snapshot_2.anchor_before(0),
4447            snapshot_2.anchor_after(2),
4448            snapshot_2.anchor_after(6),
4449            snapshot_2.anchor_after(14),
4450        ];
4451        assert_eq!(
4452            snapshot_3.summaries_for_anchors::<usize, _>(&anchors),
4453            &[0, 2, 9, 13]
4454        );
4455
4456        let new_anchors = snapshot_3.refresh_anchors(&anchors);
4457        assert_eq!(
4458            new_anchors.iter().map(|a| (a.0, a.2)).collect::<Vec<_>>(),
4459            &[(0, true), (1, true), (2, true), (3, true)]
4460        );
4461        assert_eq!(
4462            snapshot_3.summaries_for_anchors::<usize, _>(new_anchors.iter().map(|a| &a.1)),
4463            &[0, 2, 7, 13]
4464        );
4465    }
4466
4467    #[gpui::test]
4468    async fn test_diff_hunks_in_range(cx: &mut TestAppContext) {
4469        use git::diff::DiffHunkStatus;
4470
4471        // buffer has two modified hunks with two rows each
4472        let buffer_1 = cx.add_model(|cx| {
4473            let mut buffer = Buffer::new(
4474                0,
4475                "
4476                1.zero
4477                1.ONE
4478                1.TWO
4479                1.three
4480                1.FOUR
4481                1.FIVE
4482                1.six
4483            "
4484                .unindent(),
4485                cx,
4486            );
4487            buffer.set_diff_base(
4488                Some(
4489                    "
4490                1.zero
4491                1.one
4492                1.two
4493                1.three
4494                1.four
4495                1.five
4496                1.six
4497            "
4498                    .unindent(),
4499                ),
4500                cx,
4501            );
4502            buffer
4503        });
4504
4505        // buffer has a deletion hunk and an insertion hunk
4506        let buffer_2 = cx.add_model(|cx| {
4507            let mut buffer = Buffer::new(
4508                0,
4509                "
4510                2.zero
4511                2.one
4512                2.two
4513                2.three
4514                2.four
4515                2.five
4516                2.six
4517            "
4518                .unindent(),
4519                cx,
4520            );
4521            buffer.set_diff_base(
4522                Some(
4523                    "
4524                2.zero
4525                2.one
4526                2.one-and-a-half
4527                2.two
4528                2.three
4529                2.four
4530                2.six
4531            "
4532                    .unindent(),
4533                ),
4534                cx,
4535            );
4536            buffer
4537        });
4538
4539        cx.foreground().run_until_parked();
4540
4541        let multibuffer = cx.add_model(|cx| {
4542            let mut multibuffer = MultiBuffer::new(0);
4543            multibuffer.push_excerpts(
4544                buffer_1.clone(),
4545                [
4546                    // excerpt ends in the middle of a modified hunk
4547                    ExcerptRange {
4548                        context: Point::new(0, 0)..Point::new(1, 5),
4549                        primary: Default::default(),
4550                    },
4551                    // excerpt begins in the middle of a modified hunk
4552                    ExcerptRange {
4553                        context: Point::new(5, 0)..Point::new(6, 5),
4554                        primary: Default::default(),
4555                    },
4556                ],
4557                cx,
4558            );
4559            multibuffer.push_excerpts(
4560                buffer_2.clone(),
4561                [
4562                    // excerpt ends at a deletion
4563                    ExcerptRange {
4564                        context: Point::new(0, 0)..Point::new(1, 5),
4565                        primary: Default::default(),
4566                    },
4567                    // excerpt starts at a deletion
4568                    ExcerptRange {
4569                        context: Point::new(2, 0)..Point::new(2, 5),
4570                        primary: Default::default(),
4571                    },
4572                    // excerpt fully contains a deletion hunk
4573                    ExcerptRange {
4574                        context: Point::new(1, 0)..Point::new(2, 5),
4575                        primary: Default::default(),
4576                    },
4577                    // excerpt fully contains an insertion hunk
4578                    ExcerptRange {
4579                        context: Point::new(4, 0)..Point::new(6, 5),
4580                        primary: Default::default(),
4581                    },
4582                ],
4583                cx,
4584            );
4585            multibuffer
4586        });
4587
4588        let snapshot = multibuffer.read_with(cx, |b, cx| b.snapshot(cx));
4589
4590        assert_eq!(
4591            snapshot.text(),
4592            "
4593                1.zero
4594                1.ONE
4595                1.FIVE
4596                1.six
4597                2.zero
4598                2.one
4599                2.two
4600                2.one
4601                2.two
4602                2.four
4603                2.five
4604                2.six"
4605                .unindent()
4606        );
4607
4608        let expected = [
4609            (DiffHunkStatus::Modified, 1..2),
4610            (DiffHunkStatus::Modified, 2..3),
4611            //TODO: Define better when and where removed hunks show up at range extremities
4612            (DiffHunkStatus::Removed, 6..6),
4613            (DiffHunkStatus::Removed, 8..8),
4614            (DiffHunkStatus::Added, 10..11),
4615        ];
4616
4617        assert_eq!(
4618            snapshot
4619                .git_diff_hunks_in_range(0..12, false)
4620                .map(|hunk| (hunk.status(), hunk.buffer_range))
4621                .collect::<Vec<_>>(),
4622            &expected,
4623        );
4624
4625        assert_eq!(
4626            snapshot
4627                .git_diff_hunks_in_range(0..12, true)
4628                .map(|hunk| (hunk.status(), hunk.buffer_range))
4629                .collect::<Vec<_>>(),
4630            expected
4631                .iter()
4632                .rev()
4633                .cloned()
4634                .collect::<Vec<_>>()
4635                .as_slice(),
4636        );
4637    }
4638
4639    #[gpui::test(iterations = 100)]
4640    fn test_random_multibuffer(cx: &mut AppContext, mut rng: StdRng) {
4641        let operations = env::var("OPERATIONS")
4642            .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
4643            .unwrap_or(10);
4644
4645        let mut buffers: Vec<ModelHandle<Buffer>> = Vec::new();
4646        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
4647        let mut excerpt_ids = Vec::<ExcerptId>::new();
4648        let mut expected_excerpts = Vec::<(ModelHandle<Buffer>, Range<text::Anchor>)>::new();
4649        let mut anchors = Vec::new();
4650        let mut old_versions = Vec::new();
4651
4652        for _ in 0..operations {
4653            match rng.gen_range(0..100) {
4654                0..=19 if !buffers.is_empty() => {
4655                    let buffer = buffers.choose(&mut rng).unwrap();
4656                    buffer.update(cx, |buf, cx| buf.randomly_edit(&mut rng, 5, cx));
4657                }
4658                20..=29 if !expected_excerpts.is_empty() => {
4659                    let mut ids_to_remove = vec![];
4660                    for _ in 0..rng.gen_range(1..=3) {
4661                        if expected_excerpts.is_empty() {
4662                            break;
4663                        }
4664
4665                        let ix = rng.gen_range(0..expected_excerpts.len());
4666                        ids_to_remove.push(excerpt_ids.remove(ix));
4667                        let (buffer, range) = expected_excerpts.remove(ix);
4668                        let buffer = buffer.read(cx);
4669                        log::info!(
4670                            "Removing excerpt {}: {:?}",
4671                            ix,
4672                            buffer
4673                                .text_for_range(range.to_offset(buffer))
4674                                .collect::<String>(),
4675                        );
4676                    }
4677                    let snapshot = multibuffer.read(cx).read(cx);
4678                    ids_to_remove.sort_unstable_by(|a, b| a.cmp(&b, &snapshot));
4679                    drop(snapshot);
4680                    multibuffer.update(cx, |multibuffer, cx| {
4681                        multibuffer.remove_excerpts(ids_to_remove, cx)
4682                    });
4683                }
4684                30..=39 if !expected_excerpts.is_empty() => {
4685                    let multibuffer = multibuffer.read(cx).read(cx);
4686                    let offset =
4687                        multibuffer.clip_offset(rng.gen_range(0..=multibuffer.len()), Bias::Left);
4688                    let bias = if rng.gen() { Bias::Left } else { Bias::Right };
4689                    log::info!("Creating anchor at {} with bias {:?}", offset, bias);
4690                    anchors.push(multibuffer.anchor_at(offset, bias));
4691                    anchors.sort_by(|a, b| a.cmp(b, &multibuffer));
4692                }
4693                40..=44 if !anchors.is_empty() => {
4694                    let multibuffer = multibuffer.read(cx).read(cx);
4695                    let prev_len = anchors.len();
4696                    anchors = multibuffer
4697                        .refresh_anchors(&anchors)
4698                        .into_iter()
4699                        .map(|a| a.1)
4700                        .collect();
4701
4702                    // Ensure the newly-refreshed anchors point to a valid excerpt and don't
4703                    // overshoot its boundaries.
4704                    assert_eq!(anchors.len(), prev_len);
4705                    for anchor in &anchors {
4706                        if anchor.excerpt_id == ExcerptId::min()
4707                            || anchor.excerpt_id == ExcerptId::max()
4708                        {
4709                            continue;
4710                        }
4711
4712                        let excerpt = multibuffer.excerpt(anchor.excerpt_id).unwrap();
4713                        assert_eq!(excerpt.id, anchor.excerpt_id);
4714                        assert!(excerpt.contains(anchor));
4715                    }
4716                }
4717                _ => {
4718                    let buffer_handle = if buffers.is_empty() || rng.gen_bool(0.4) {
4719                        let base_text = util::RandomCharIter::new(&mut rng)
4720                            .take(10)
4721                            .collect::<String>();
4722                        buffers.push(cx.add_model(|cx| Buffer::new(0, base_text, cx)));
4723                        buffers.last().unwrap()
4724                    } else {
4725                        buffers.choose(&mut rng).unwrap()
4726                    };
4727
4728                    let buffer = buffer_handle.read(cx);
4729                    let end_ix = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Bias::Right);
4730                    let start_ix = buffer.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
4731                    let anchor_range = buffer.anchor_before(start_ix)..buffer.anchor_after(end_ix);
4732                    let prev_excerpt_ix = rng.gen_range(0..=expected_excerpts.len());
4733                    let prev_excerpt_id = excerpt_ids
4734                        .get(prev_excerpt_ix)
4735                        .cloned()
4736                        .unwrap_or_else(ExcerptId::max);
4737                    let excerpt_ix = (prev_excerpt_ix + 1).min(expected_excerpts.len());
4738
4739                    log::info!(
4740                        "Inserting excerpt at {} of {} for buffer {}: {:?}[{:?}] = {:?}",
4741                        excerpt_ix,
4742                        expected_excerpts.len(),
4743                        buffer_handle.read(cx).remote_id(),
4744                        buffer.text(),
4745                        start_ix..end_ix,
4746                        &buffer.text()[start_ix..end_ix]
4747                    );
4748
4749                    let excerpt_id = multibuffer.update(cx, |multibuffer, cx| {
4750                        multibuffer
4751                            .insert_excerpts_after(
4752                                prev_excerpt_id,
4753                                buffer_handle.clone(),
4754                                [ExcerptRange {
4755                                    context: start_ix..end_ix,
4756                                    primary: None,
4757                                }],
4758                                cx,
4759                            )
4760                            .pop()
4761                            .unwrap()
4762                    });
4763
4764                    excerpt_ids.insert(excerpt_ix, excerpt_id);
4765                    expected_excerpts.insert(excerpt_ix, (buffer_handle.clone(), anchor_range));
4766                }
4767            }
4768
4769            if rng.gen_bool(0.3) {
4770                multibuffer.update(cx, |multibuffer, cx| {
4771                    old_versions.push((multibuffer.snapshot(cx), multibuffer.subscribe()));
4772                })
4773            }
4774
4775            let snapshot = multibuffer.read(cx).snapshot(cx);
4776
4777            let mut excerpt_starts = Vec::new();
4778            let mut expected_text = String::new();
4779            let mut expected_buffer_rows = Vec::new();
4780            for (buffer, range) in &expected_excerpts {
4781                let buffer = buffer.read(cx);
4782                let buffer_range = range.to_offset(buffer);
4783
4784                excerpt_starts.push(TextSummary::from(expected_text.as_str()));
4785                expected_text.extend(buffer.text_for_range(buffer_range.clone()));
4786                expected_text.push('\n');
4787
4788                let buffer_row_range = buffer.offset_to_point(buffer_range.start).row
4789                    ..=buffer.offset_to_point(buffer_range.end).row;
4790                for row in buffer_row_range {
4791                    expected_buffer_rows.push(Some(row));
4792                }
4793            }
4794            // Remove final trailing newline.
4795            if !expected_excerpts.is_empty() {
4796                expected_text.pop();
4797            }
4798
4799            // Always report one buffer row
4800            if expected_buffer_rows.is_empty() {
4801                expected_buffer_rows.push(Some(0));
4802            }
4803
4804            assert_eq!(snapshot.text(), expected_text);
4805            log::info!("MultiBuffer text: {:?}", expected_text);
4806
4807            assert_eq!(
4808                snapshot.buffer_rows(0).collect::<Vec<_>>(),
4809                expected_buffer_rows,
4810            );
4811
4812            for _ in 0..5 {
4813                let start_row = rng.gen_range(0..=expected_buffer_rows.len());
4814                assert_eq!(
4815                    snapshot.buffer_rows(start_row as u32).collect::<Vec<_>>(),
4816                    &expected_buffer_rows[start_row..],
4817                    "buffer_rows({})",
4818                    start_row
4819                );
4820            }
4821
4822            assert_eq!(
4823                snapshot.max_buffer_row(),
4824                expected_buffer_rows.into_iter().flatten().max().unwrap()
4825            );
4826
4827            let mut excerpt_starts = excerpt_starts.into_iter();
4828            for (buffer, range) in &expected_excerpts {
4829                let buffer = buffer.read(cx);
4830                let buffer_id = buffer.remote_id();
4831                let buffer_range = range.to_offset(buffer);
4832                let buffer_start_point = buffer.offset_to_point(buffer_range.start);
4833                let buffer_start_point_utf16 =
4834                    buffer.text_summary_for_range::<PointUtf16, _>(0..buffer_range.start);
4835
4836                let excerpt_start = excerpt_starts.next().unwrap();
4837                let mut offset = excerpt_start.len;
4838                let mut buffer_offset = buffer_range.start;
4839                let mut point = excerpt_start.lines;
4840                let mut buffer_point = buffer_start_point;
4841                let mut point_utf16 = excerpt_start.lines_utf16();
4842                let mut buffer_point_utf16 = buffer_start_point_utf16;
4843                for ch in buffer
4844                    .snapshot()
4845                    .chunks(buffer_range.clone(), false)
4846                    .flat_map(|c| c.text.chars())
4847                {
4848                    for _ in 0..ch.len_utf8() {
4849                        let left_offset = snapshot.clip_offset(offset, Bias::Left);
4850                        let right_offset = snapshot.clip_offset(offset, Bias::Right);
4851                        let buffer_left_offset = buffer.clip_offset(buffer_offset, Bias::Left);
4852                        let buffer_right_offset = buffer.clip_offset(buffer_offset, Bias::Right);
4853                        assert_eq!(
4854                            left_offset,
4855                            excerpt_start.len + (buffer_left_offset - buffer_range.start),
4856                            "clip_offset({:?}, Left). buffer: {:?}, buffer offset: {:?}",
4857                            offset,
4858                            buffer_id,
4859                            buffer_offset,
4860                        );
4861                        assert_eq!(
4862                            right_offset,
4863                            excerpt_start.len + (buffer_right_offset - buffer_range.start),
4864                            "clip_offset({:?}, Right). buffer: {:?}, buffer offset: {:?}",
4865                            offset,
4866                            buffer_id,
4867                            buffer_offset,
4868                        );
4869
4870                        let left_point = snapshot.clip_point(point, Bias::Left);
4871                        let right_point = snapshot.clip_point(point, Bias::Right);
4872                        let buffer_left_point = buffer.clip_point(buffer_point, Bias::Left);
4873                        let buffer_right_point = buffer.clip_point(buffer_point, Bias::Right);
4874                        assert_eq!(
4875                            left_point,
4876                            excerpt_start.lines + (buffer_left_point - buffer_start_point),
4877                            "clip_point({:?}, Left). buffer: {:?}, buffer point: {:?}",
4878                            point,
4879                            buffer_id,
4880                            buffer_point,
4881                        );
4882                        assert_eq!(
4883                            right_point,
4884                            excerpt_start.lines + (buffer_right_point - buffer_start_point),
4885                            "clip_point({:?}, Right). buffer: {:?}, buffer point: {:?}",
4886                            point,
4887                            buffer_id,
4888                            buffer_point,
4889                        );
4890
4891                        assert_eq!(
4892                            snapshot.point_to_offset(left_point),
4893                            left_offset,
4894                            "point_to_offset({:?})",
4895                            left_point,
4896                        );
4897                        assert_eq!(
4898                            snapshot.offset_to_point(left_offset),
4899                            left_point,
4900                            "offset_to_point({:?})",
4901                            left_offset,
4902                        );
4903
4904                        offset += 1;
4905                        buffer_offset += 1;
4906                        if ch == '\n' {
4907                            point += Point::new(1, 0);
4908                            buffer_point += Point::new(1, 0);
4909                        } else {
4910                            point += Point::new(0, 1);
4911                            buffer_point += Point::new(0, 1);
4912                        }
4913                    }
4914
4915                    for _ in 0..ch.len_utf16() {
4916                        let left_point_utf16 =
4917                            snapshot.clip_point_utf16(Unclipped(point_utf16), Bias::Left);
4918                        let right_point_utf16 =
4919                            snapshot.clip_point_utf16(Unclipped(point_utf16), Bias::Right);
4920                        let buffer_left_point_utf16 =
4921                            buffer.clip_point_utf16(Unclipped(buffer_point_utf16), Bias::Left);
4922                        let buffer_right_point_utf16 =
4923                            buffer.clip_point_utf16(Unclipped(buffer_point_utf16), Bias::Right);
4924                        assert_eq!(
4925                            left_point_utf16,
4926                            excerpt_start.lines_utf16()
4927                                + (buffer_left_point_utf16 - buffer_start_point_utf16),
4928                            "clip_point_utf16({:?}, Left). buffer: {:?}, buffer point_utf16: {:?}",
4929                            point_utf16,
4930                            buffer_id,
4931                            buffer_point_utf16,
4932                        );
4933                        assert_eq!(
4934                            right_point_utf16,
4935                            excerpt_start.lines_utf16()
4936                                + (buffer_right_point_utf16 - buffer_start_point_utf16),
4937                            "clip_point_utf16({:?}, Right). buffer: {:?}, buffer point_utf16: {:?}",
4938                            point_utf16,
4939                            buffer_id,
4940                            buffer_point_utf16,
4941                        );
4942
4943                        if ch == '\n' {
4944                            point_utf16 += PointUtf16::new(1, 0);
4945                            buffer_point_utf16 += PointUtf16::new(1, 0);
4946                        } else {
4947                            point_utf16 += PointUtf16::new(0, 1);
4948                            buffer_point_utf16 += PointUtf16::new(0, 1);
4949                        }
4950                    }
4951                }
4952            }
4953
4954            for (row, line) in expected_text.split('\n').enumerate() {
4955                assert_eq!(
4956                    snapshot.line_len(row as u32),
4957                    line.len() as u32,
4958                    "line_len({}).",
4959                    row
4960                );
4961            }
4962
4963            let text_rope = Rope::from(expected_text.as_str());
4964            for _ in 0..10 {
4965                let end_ix = text_rope.clip_offset(rng.gen_range(0..=text_rope.len()), Bias::Right);
4966                let start_ix = text_rope.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
4967
4968                let text_for_range = snapshot
4969                    .text_for_range(start_ix..end_ix)
4970                    .collect::<String>();
4971                assert_eq!(
4972                    text_for_range,
4973                    &expected_text[start_ix..end_ix],
4974                    "incorrect text for range {:?}",
4975                    start_ix..end_ix
4976                );
4977
4978                let excerpted_buffer_ranges = multibuffer
4979                    .read(cx)
4980                    .range_to_buffer_ranges(start_ix..end_ix, cx);
4981                let excerpted_buffers_text = excerpted_buffer_ranges
4982                    .into_iter()
4983                    .map(|(buffer, buffer_range)| {
4984                        buffer
4985                            .read(cx)
4986                            .text_for_range(buffer_range)
4987                            .collect::<String>()
4988                    })
4989                    .collect::<Vec<_>>()
4990                    .join("\n");
4991                assert_eq!(excerpted_buffers_text, text_for_range);
4992
4993                let expected_summary = TextSummary::from(&expected_text[start_ix..end_ix]);
4994                assert_eq!(
4995                    snapshot.text_summary_for_range::<TextSummary, _>(start_ix..end_ix),
4996                    expected_summary,
4997                    "incorrect summary for range {:?}",
4998                    start_ix..end_ix
4999                );
5000            }
5001
5002            // Anchor resolution
5003            let summaries = snapshot.summaries_for_anchors::<usize, _>(&anchors);
5004            assert_eq!(anchors.len(), summaries.len());
5005            for (anchor, resolved_offset) in anchors.iter().zip(summaries) {
5006                assert!(resolved_offset <= snapshot.len());
5007                assert_eq!(
5008                    snapshot.summary_for_anchor::<usize>(anchor),
5009                    resolved_offset
5010                );
5011            }
5012
5013            for _ in 0..10 {
5014                let end_ix = text_rope.clip_offset(rng.gen_range(0..=text_rope.len()), Bias::Right);
5015                assert_eq!(
5016                    snapshot.reversed_chars_at(end_ix).collect::<String>(),
5017                    expected_text[..end_ix].chars().rev().collect::<String>(),
5018                );
5019            }
5020
5021            for _ in 0..10 {
5022                let end_ix = rng.gen_range(0..=text_rope.len());
5023                let start_ix = rng.gen_range(0..=end_ix);
5024                assert_eq!(
5025                    snapshot
5026                        .bytes_in_range(start_ix..end_ix)
5027                        .flatten()
5028                        .copied()
5029                        .collect::<Vec<_>>(),
5030                    expected_text.as_bytes()[start_ix..end_ix].to_vec(),
5031                    "bytes_in_range({:?})",
5032                    start_ix..end_ix,
5033                );
5034            }
5035        }
5036
5037        let snapshot = multibuffer.read(cx).snapshot(cx);
5038        for (old_snapshot, subscription) in old_versions {
5039            let edits = subscription.consume().into_inner();
5040
5041            log::info!(
5042                "applying subscription edits to old text: {:?}: {:?}",
5043                old_snapshot.text(),
5044                edits,
5045            );
5046
5047            let mut text = old_snapshot.text();
5048            for edit in edits {
5049                let new_text: String = snapshot.text_for_range(edit.new.clone()).collect();
5050                text.replace_range(edit.new.start..edit.new.start + edit.old.len(), &new_text);
5051            }
5052            assert_eq!(text.to_string(), snapshot.text());
5053        }
5054    }
5055
5056    #[gpui::test]
5057    fn test_history(cx: &mut AppContext) {
5058        cx.set_global(Settings::test(cx));
5059        let buffer_1 = cx.add_model(|cx| Buffer::new(0, "1234", cx));
5060        let buffer_2 = cx.add_model(|cx| Buffer::new(0, "5678", cx));
5061        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
5062        let group_interval = multibuffer.read(cx).history.group_interval;
5063        multibuffer.update(cx, |multibuffer, cx| {
5064            multibuffer.push_excerpts(
5065                buffer_1.clone(),
5066                [ExcerptRange {
5067                    context: 0..buffer_1.read(cx).len(),
5068                    primary: None,
5069                }],
5070                cx,
5071            );
5072            multibuffer.push_excerpts(
5073                buffer_2.clone(),
5074                [ExcerptRange {
5075                    context: 0..buffer_2.read(cx).len(),
5076                    primary: None,
5077                }],
5078                cx,
5079            );
5080        });
5081
5082        let mut now = Instant::now();
5083
5084        multibuffer.update(cx, |multibuffer, cx| {
5085            let transaction_1 = multibuffer.start_transaction_at(now, cx).unwrap();
5086            multibuffer.edit(
5087                [
5088                    (Point::new(0, 0)..Point::new(0, 0), "A"),
5089                    (Point::new(1, 0)..Point::new(1, 0), "A"),
5090                ],
5091                None,
5092                cx,
5093            );
5094            multibuffer.edit(
5095                [
5096                    (Point::new(0, 1)..Point::new(0, 1), "B"),
5097                    (Point::new(1, 1)..Point::new(1, 1), "B"),
5098                ],
5099                None,
5100                cx,
5101            );
5102            multibuffer.end_transaction_at(now, cx);
5103            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
5104
5105            // Edit buffer 1 through the multibuffer
5106            now += 2 * group_interval;
5107            multibuffer.start_transaction_at(now, cx);
5108            multibuffer.edit([(2..2, "C")], None, cx);
5109            multibuffer.end_transaction_at(now, cx);
5110            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678");
5111
5112            // Edit buffer 1 independently
5113            buffer_1.update(cx, |buffer_1, cx| {
5114                buffer_1.start_transaction_at(now);
5115                buffer_1.edit([(3..3, "D")], None, cx);
5116                buffer_1.end_transaction_at(now, cx);
5117
5118                now += 2 * group_interval;
5119                buffer_1.start_transaction_at(now);
5120                buffer_1.edit([(4..4, "E")], None, cx);
5121                buffer_1.end_transaction_at(now, cx);
5122            });
5123            assert_eq!(multibuffer.read(cx).text(), "ABCDE1234\nAB5678");
5124
5125            // An undo in the multibuffer undoes the multibuffer transaction
5126            // and also any individual buffer edits that have occured since
5127            // that transaction.
5128            multibuffer.undo(cx);
5129            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
5130
5131            multibuffer.undo(cx);
5132            assert_eq!(multibuffer.read(cx).text(), "1234\n5678");
5133
5134            multibuffer.redo(cx);
5135            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
5136
5137            multibuffer.redo(cx);
5138            assert_eq!(multibuffer.read(cx).text(), "ABCDE1234\nAB5678");
5139
5140            // Undo buffer 2 independently.
5141            buffer_2.update(cx, |buffer_2, cx| buffer_2.undo(cx));
5142            assert_eq!(multibuffer.read(cx).text(), "ABCDE1234\n5678");
5143
5144            // An undo in the multibuffer undoes the components of the
5145            // the last multibuffer transaction that are not already undone.
5146            multibuffer.undo(cx);
5147            assert_eq!(multibuffer.read(cx).text(), "AB1234\n5678");
5148
5149            multibuffer.undo(cx);
5150            assert_eq!(multibuffer.read(cx).text(), "1234\n5678");
5151
5152            multibuffer.redo(cx);
5153            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
5154
5155            buffer_1.update(cx, |buffer_1, cx| buffer_1.redo(cx));
5156            assert_eq!(multibuffer.read(cx).text(), "ABCD1234\nAB5678");
5157
5158            // Redo stack gets cleared after an edit.
5159            now += 2 * group_interval;
5160            multibuffer.start_transaction_at(now, cx);
5161            multibuffer.edit([(0..0, "X")], None, cx);
5162            multibuffer.end_transaction_at(now, cx);
5163            assert_eq!(multibuffer.read(cx).text(), "XABCD1234\nAB5678");
5164            multibuffer.redo(cx);
5165            assert_eq!(multibuffer.read(cx).text(), "XABCD1234\nAB5678");
5166            multibuffer.undo(cx);
5167            assert_eq!(multibuffer.read(cx).text(), "ABCD1234\nAB5678");
5168            multibuffer.undo(cx);
5169            assert_eq!(multibuffer.read(cx).text(), "1234\n5678");
5170
5171            // Transactions can be grouped manually.
5172            multibuffer.redo(cx);
5173            multibuffer.redo(cx);
5174            assert_eq!(multibuffer.read(cx).text(), "XABCD1234\nAB5678");
5175            multibuffer.group_until_transaction(transaction_1, cx);
5176            multibuffer.undo(cx);
5177            assert_eq!(multibuffer.read(cx).text(), "1234\n5678");
5178            multibuffer.redo(cx);
5179            assert_eq!(multibuffer.read(cx).text(), "XABCD1234\nAB5678");
5180        });
5181    }
5182}