multi_buffer.rs

   1mod anchor;
   2
   3pub use anchor::{Anchor, AnchorRangeExt};
   4use anyhow::Result;
   5use clock::ReplicaId;
   6use collections::{HashMap, HashSet};
   7use gpui::{AppContext, Entity, ModelContext, ModelHandle, Task};
   8pub use language::Completion;
   9use language::{
  10    Buffer, BufferChunks, BufferSnapshot, Chunk, DiagnosticEntry, Event, File, Language, Outline,
  11    OutlineItem, Selection, ToOffset as _, ToPoint as _, TransactionId,
  12};
  13use std::{
  14    cell::{Ref, RefCell},
  15    cmp, fmt, io,
  16    iter::{self, FromIterator},
  17    ops::{Range, Sub},
  18    str,
  19    sync::Arc,
  20    time::{Duration, Instant},
  21};
  22use sum_tree::{Bias, Cursor, SumTree};
  23use text::{
  24    locator::Locator,
  25    rope::TextDimension,
  26    subscription::{Subscription, Topic},
  27    AnchorRangeExt as _, Edit, Point, PointUtf16, TextSummary,
  28};
  29use theme::SyntaxTheme;
  30use util::post_inc;
  31
  32const NEWLINES: &'static [u8] = &[b'\n'; u8::MAX as usize];
  33
  34pub type ExcerptId = Locator;
  35
  36pub struct MultiBuffer {
  37    snapshot: RefCell<MultiBufferSnapshot>,
  38    buffers: RefCell<HashMap<usize, BufferState>>,
  39    subscriptions: Topic,
  40    singleton: bool,
  41    replica_id: ReplicaId,
  42    history: History,
  43}
  44
  45struct History {
  46    next_transaction_id: usize,
  47    undo_stack: Vec<Transaction>,
  48    redo_stack: Vec<Transaction>,
  49    transaction_depth: usize,
  50    group_interval: Duration,
  51}
  52
  53struct Transaction {
  54    id: usize,
  55    buffer_transactions: HashSet<(usize, text::TransactionId)>,
  56    first_edit_at: Instant,
  57    last_edit_at: Instant,
  58}
  59
  60pub trait ToOffset: 'static + fmt::Debug {
  61    fn to_offset(&self, snapshot: &MultiBufferSnapshot) -> usize;
  62}
  63
  64pub trait ToPoint: 'static + fmt::Debug {
  65    fn to_point(&self, snapshot: &MultiBufferSnapshot) -> Point;
  66}
  67
  68struct BufferState {
  69    buffer: ModelHandle<Buffer>,
  70    last_version: clock::Global,
  71    last_parse_count: usize,
  72    last_selections_update_count: usize,
  73    last_diagnostics_update_count: usize,
  74    excerpts: Vec<ExcerptId>,
  75    _subscriptions: [gpui::Subscription; 2],
  76}
  77
  78#[derive(Clone, Default)]
  79pub struct MultiBufferSnapshot {
  80    singleton: bool,
  81    excerpts: SumTree<Excerpt>,
  82    parse_count: usize,
  83    diagnostics_update_count: usize,
  84    is_dirty: bool,
  85    has_conflict: bool,
  86}
  87
  88pub struct ExcerptProperties<'a, T> {
  89    pub buffer: &'a ModelHandle<Buffer>,
  90    pub range: Range<T>,
  91}
  92
  93#[derive(Clone)]
  94struct Excerpt {
  95    id: ExcerptId,
  96    buffer_id: usize,
  97    buffer: BufferSnapshot,
  98    range: Range<text::Anchor>,
  99    max_buffer_row: u32,
 100    text_summary: TextSummary,
 101    has_trailing_newline: bool,
 102}
 103
 104#[derive(Clone, Debug, Default)]
 105struct ExcerptSummary {
 106    excerpt_id: ExcerptId,
 107    max_buffer_row: u32,
 108    text: TextSummary,
 109}
 110
 111pub struct MultiBufferRows<'a> {
 112    buffer_row_range: Range<u32>,
 113    excerpts: Cursor<'a, Excerpt, Point>,
 114}
 115
 116pub struct MultiBufferChunks<'a> {
 117    range: Range<usize>,
 118    excerpts: Cursor<'a, Excerpt, usize>,
 119    excerpt_chunks: Option<ExcerptChunks<'a>>,
 120    theme: Option<&'a SyntaxTheme>,
 121}
 122
 123pub struct MultiBufferBytes<'a> {
 124    range: Range<usize>,
 125    excerpts: Cursor<'a, Excerpt, usize>,
 126    excerpt_bytes: Option<ExcerptBytes<'a>>,
 127    chunk: &'a [u8],
 128}
 129
 130struct ExcerptChunks<'a> {
 131    content_chunks: BufferChunks<'a>,
 132    footer_height: usize,
 133}
 134
 135struct ExcerptBytes<'a> {
 136    content_bytes: language::rope::Bytes<'a>,
 137    footer_height: usize,
 138}
 139
 140impl MultiBuffer {
 141    pub fn new(replica_id: ReplicaId) -> Self {
 142        Self {
 143            snapshot: Default::default(),
 144            buffers: Default::default(),
 145            subscriptions: Default::default(),
 146            singleton: false,
 147            replica_id,
 148            history: History {
 149                next_transaction_id: Default::default(),
 150                undo_stack: Default::default(),
 151                redo_stack: Default::default(),
 152                transaction_depth: 0,
 153                group_interval: Duration::from_millis(300),
 154            },
 155        }
 156    }
 157
 158    pub fn singleton(buffer: ModelHandle<Buffer>, cx: &mut ModelContext<Self>) -> Self {
 159        let mut this = Self::new(buffer.read(cx).replica_id());
 160        this.singleton = true;
 161        this.push_excerpt(
 162            ExcerptProperties {
 163                buffer: &buffer,
 164                range: text::Anchor::min()..text::Anchor::max(),
 165            },
 166            cx,
 167        );
 168        this.snapshot.borrow_mut().singleton = true;
 169        this
 170    }
 171
 172    #[cfg(any(test, feature = "test-support"))]
 173    pub fn build_simple(text: &str, cx: &mut gpui::MutableAppContext) -> ModelHandle<Self> {
 174        let buffer = cx.add_model(|cx| Buffer::new(0, text, cx));
 175        cx.add_model(|cx| Self::singleton(buffer, cx))
 176    }
 177
 178    #[cfg(any(test, feature = "test-support"))]
 179    pub fn build_random(
 180        mut rng: &mut impl rand::Rng,
 181        cx: &mut gpui::MutableAppContext,
 182    ) -> ModelHandle<Self> {
 183        use rand::prelude::*;
 184        use std::env;
 185        use text::RandomCharIter;
 186
 187        let max_excerpts = env::var("MAX_EXCERPTS")
 188            .map(|i| i.parse().expect("invalid `MAX_EXCERPTS` variable"))
 189            .unwrap_or(5);
 190        let excerpts = rng.gen_range(1..=max_excerpts);
 191
 192        cx.add_model(|cx| {
 193            let mut multibuffer = MultiBuffer::new(0);
 194            let mut buffers = Vec::new();
 195            for _ in 0..excerpts {
 196                let buffer_handle = if rng.gen() || buffers.is_empty() {
 197                    let text = RandomCharIter::new(&mut rng).take(10).collect::<String>();
 198                    buffers.push(cx.add_model(|cx| Buffer::new(0, text, cx)));
 199                    let buffer = buffers.last().unwrap();
 200                    log::info!(
 201                        "Creating new buffer {} with text: {:?}",
 202                        buffer.id(),
 203                        buffer.read(cx).text()
 204                    );
 205                    buffers.last().unwrap()
 206                } else {
 207                    buffers.choose(rng).unwrap()
 208                };
 209
 210                let buffer = buffer_handle.read(cx);
 211                let end_ix = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Bias::Right);
 212                let start_ix = buffer.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
 213                let header_height = rng.gen_range(0..=5);
 214                log::info!(
 215                    "Inserting excerpt from buffer {} with header height {} and range {:?}: {:?}",
 216                    buffer_handle.id(),
 217                    header_height,
 218                    start_ix..end_ix,
 219                    &buffer.text()[start_ix..end_ix]
 220                );
 221
 222                multibuffer.push_excerpt(
 223                    ExcerptProperties {
 224                        buffer: buffer_handle,
 225                        range: start_ix..end_ix,
 226                    },
 227                    cx,
 228                );
 229            }
 230            multibuffer
 231        })
 232    }
 233
 234    pub fn replica_id(&self) -> ReplicaId {
 235        self.replica_id
 236    }
 237
 238    pub fn snapshot(&self, cx: &AppContext) -> MultiBufferSnapshot {
 239        self.sync(cx);
 240        self.snapshot.borrow().clone()
 241    }
 242
 243    pub fn read(&self, cx: &AppContext) -> Ref<MultiBufferSnapshot> {
 244        self.sync(cx);
 245        self.snapshot.borrow()
 246    }
 247
 248    pub fn as_singleton(&self) -> Option<ModelHandle<Buffer>> {
 249        if self.singleton {
 250            return Some(
 251                self.buffers
 252                    .borrow()
 253                    .values()
 254                    .next()
 255                    .unwrap()
 256                    .buffer
 257                    .clone(),
 258            );
 259        } else {
 260            None
 261        }
 262    }
 263
 264    pub fn subscribe(&mut self) -> Subscription {
 265        self.subscriptions.subscribe()
 266    }
 267
 268    pub fn edit<I, S, T>(&mut self, ranges: I, new_text: T, cx: &mut ModelContext<Self>)
 269    where
 270        I: IntoIterator<Item = Range<S>>,
 271        S: ToOffset,
 272        T: Into<String>,
 273    {
 274        self.edit_internal(ranges, new_text, false, cx)
 275    }
 276
 277    pub fn edit_with_autoindent<I, S, T>(
 278        &mut self,
 279        ranges: I,
 280        new_text: T,
 281        cx: &mut ModelContext<Self>,
 282    ) where
 283        I: IntoIterator<Item = Range<S>>,
 284        S: ToOffset,
 285        T: Into<String>,
 286    {
 287        self.edit_internal(ranges, new_text, true, cx)
 288    }
 289
 290    pub fn edit_internal<I, S, T>(
 291        &mut self,
 292        ranges_iter: I,
 293        new_text: T,
 294        autoindent: bool,
 295        cx: &mut ModelContext<Self>,
 296    ) where
 297        I: IntoIterator<Item = Range<S>>,
 298        S: ToOffset,
 299        T: Into<String>,
 300    {
 301        if let Some(buffer) = self.as_singleton() {
 302            let snapshot = self.read(cx);
 303            let ranges = ranges_iter
 304                .into_iter()
 305                .map(|range| range.start.to_offset(&snapshot)..range.end.to_offset(&snapshot));
 306            return buffer.update(cx, |buffer, cx| {
 307                if autoindent {
 308                    buffer.edit_with_autoindent(ranges, new_text, cx)
 309                } else {
 310                    buffer.edit(ranges, new_text, cx)
 311                }
 312            });
 313        }
 314
 315        let snapshot = self.read(cx);
 316        let mut buffer_edits: HashMap<usize, Vec<(Range<usize>, bool)>> = Default::default();
 317        let mut cursor = snapshot.excerpts.cursor::<usize>();
 318        for range in ranges_iter {
 319            let start = range.start.to_offset(&snapshot);
 320            let end = range.end.to_offset(&snapshot);
 321            cursor.seek(&start, Bias::Right, &());
 322            if cursor.item().is_none() && start == *cursor.start() {
 323                cursor.prev(&());
 324            }
 325            let start_excerpt = cursor.item().expect("start offset out of bounds");
 326            let start_overshoot = start - cursor.start();
 327            let buffer_start =
 328                start_excerpt.range.start.to_offset(&start_excerpt.buffer) + start_overshoot;
 329
 330            cursor.seek(&end, Bias::Right, &());
 331            if cursor.item().is_none() && end == *cursor.start() {
 332                cursor.prev(&());
 333            }
 334            let end_excerpt = cursor.item().expect("end offset out of bounds");
 335            let end_overshoot = end - cursor.start();
 336            let buffer_end = end_excerpt.range.start.to_offset(&end_excerpt.buffer) + end_overshoot;
 337
 338            if start_excerpt.id == end_excerpt.id {
 339                buffer_edits
 340                    .entry(start_excerpt.buffer_id)
 341                    .or_insert(Vec::new())
 342                    .push((buffer_start..buffer_end, true));
 343            } else {
 344                let start_excerpt_range =
 345                    buffer_start..start_excerpt.range.end.to_offset(&start_excerpt.buffer);
 346                let end_excerpt_range =
 347                    end_excerpt.range.start.to_offset(&end_excerpt.buffer)..buffer_end;
 348                buffer_edits
 349                    .entry(start_excerpt.buffer_id)
 350                    .or_insert(Vec::new())
 351                    .push((start_excerpt_range, true));
 352                buffer_edits
 353                    .entry(end_excerpt.buffer_id)
 354                    .or_insert(Vec::new())
 355                    .push((end_excerpt_range, false));
 356
 357                cursor.seek(&start, Bias::Right, &());
 358                cursor.next(&());
 359                while let Some(excerpt) = cursor.item() {
 360                    if excerpt.id == end_excerpt.id {
 361                        break;
 362                    }
 363                    buffer_edits
 364                        .entry(excerpt.buffer_id)
 365                        .or_insert(Vec::new())
 366                        .push((excerpt.range.to_offset(&excerpt.buffer), false));
 367                    cursor.next(&());
 368                }
 369            }
 370        }
 371
 372        let new_text = new_text.into();
 373        for (buffer_id, mut edits) in buffer_edits {
 374            edits.sort_unstable_by_key(|(range, _)| range.start);
 375            self.buffers.borrow()[&buffer_id]
 376                .buffer
 377                .update(cx, |buffer, cx| {
 378                    let mut edits = edits.into_iter().peekable();
 379                    let mut insertions = Vec::new();
 380                    let mut deletions = Vec::new();
 381                    while let Some((mut range, mut is_insertion)) = edits.next() {
 382                        while let Some((next_range, next_is_insertion)) = edits.peek() {
 383                            if range.end >= next_range.start {
 384                                range.end = cmp::max(next_range.end, range.end);
 385                                is_insertion |= *next_is_insertion;
 386                                edits.next();
 387                            } else {
 388                                break;
 389                            }
 390                        }
 391
 392                        if is_insertion {
 393                            insertions.push(
 394                                buffer.anchor_before(range.start)..buffer.anchor_before(range.end),
 395                            );
 396                        } else if !range.is_empty() {
 397                            deletions.push(
 398                                buffer.anchor_before(range.start)..buffer.anchor_before(range.end),
 399                            );
 400                        }
 401                    }
 402
 403                    if autoindent {
 404                        buffer.edit_with_autoindent(deletions, "", cx);
 405                        buffer.edit_with_autoindent(insertions, new_text.clone(), cx);
 406                    } else {
 407                        buffer.edit(deletions, "", cx);
 408                        buffer.edit(insertions, new_text.clone(), cx);
 409                    }
 410                })
 411        }
 412    }
 413
 414    pub fn start_transaction(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 415        self.start_transaction_at(Instant::now(), cx)
 416    }
 417
 418    pub(crate) fn start_transaction_at(
 419        &mut self,
 420        now: Instant,
 421        cx: &mut ModelContext<Self>,
 422    ) -> Option<TransactionId> {
 423        if let Some(buffer) = self.as_singleton() {
 424            return buffer.update(cx, |buffer, _| buffer.start_transaction_at(now));
 425        }
 426
 427        for BufferState { buffer, .. } in self.buffers.borrow().values() {
 428            buffer.update(cx, |buffer, _| buffer.start_transaction_at(now));
 429        }
 430        self.history.start_transaction(now)
 431    }
 432
 433    pub fn end_transaction(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 434        self.end_transaction_at(Instant::now(), cx)
 435    }
 436
 437    pub(crate) fn end_transaction_at(
 438        &mut self,
 439        now: Instant,
 440        cx: &mut ModelContext<Self>,
 441    ) -> Option<TransactionId> {
 442        if let Some(buffer) = self.as_singleton() {
 443            return buffer.update(cx, |buffer, cx| buffer.end_transaction_at(now, cx));
 444        }
 445
 446        let mut buffer_transactions = HashSet::default();
 447        for BufferState { buffer, .. } in self.buffers.borrow().values() {
 448            if let Some(transaction_id) =
 449                buffer.update(cx, |buffer, cx| buffer.end_transaction_at(now, cx))
 450            {
 451                buffer_transactions.insert((buffer.id(), transaction_id));
 452            }
 453        }
 454
 455        if self.history.end_transaction(now, buffer_transactions) {
 456            let transaction_id = self.history.group().unwrap();
 457            Some(transaction_id)
 458        } else {
 459            None
 460        }
 461    }
 462
 463    pub fn avoid_grouping_next_transaction(&mut self, cx: &mut ModelContext<Self>) {
 464        for BufferState { buffer, .. } in self.buffers.borrow().values() {
 465            buffer.update(cx, |buffer, _| buffer.avoid_grouping_next_transaction());
 466        }
 467    }
 468
 469    pub fn set_active_selections(
 470        &mut self,
 471        selections: &[Selection<Anchor>],
 472        cx: &mut ModelContext<Self>,
 473    ) {
 474        let mut selections_by_buffer: HashMap<usize, Vec<Selection<text::Anchor>>> =
 475            Default::default();
 476        let snapshot = self.read(cx);
 477        let mut cursor = snapshot.excerpts.cursor::<Option<&ExcerptId>>();
 478        for selection in selections {
 479            cursor.seek(&Some(&selection.start.excerpt_id), Bias::Left, &());
 480            while let Some(excerpt) = cursor.item() {
 481                if excerpt.id > selection.end.excerpt_id {
 482                    break;
 483                }
 484
 485                let mut start = excerpt.range.start.clone();
 486                let mut end = excerpt.range.end.clone();
 487                if excerpt.id == selection.start.excerpt_id {
 488                    start = selection.start.text_anchor.clone();
 489                }
 490                if excerpt.id == selection.end.excerpt_id {
 491                    end = selection.end.text_anchor.clone();
 492                }
 493                selections_by_buffer
 494                    .entry(excerpt.buffer_id)
 495                    .or_default()
 496                    .push(Selection {
 497                        id: selection.id,
 498                        start,
 499                        end,
 500                        reversed: selection.reversed,
 501                        goal: selection.goal,
 502                    });
 503
 504                cursor.next(&());
 505            }
 506        }
 507
 508        for (buffer_id, buffer_state) in self.buffers.borrow().iter() {
 509            if !selections_by_buffer.contains_key(buffer_id) {
 510                buffer_state
 511                    .buffer
 512                    .update(cx, |buffer, cx| buffer.remove_active_selections(cx));
 513            }
 514        }
 515
 516        for (buffer_id, mut selections) in selections_by_buffer {
 517            self.buffers.borrow()[&buffer_id]
 518                .buffer
 519                .update(cx, |buffer, cx| {
 520                    selections.sort_unstable_by(|a, b| a.start.cmp(&b.start, buffer).unwrap());
 521                    let mut selections = selections.into_iter().peekable();
 522                    let merged_selections = Arc::from_iter(iter::from_fn(|| {
 523                        let mut selection = selections.next()?;
 524                        while let Some(next_selection) = selections.peek() {
 525                            if selection
 526                                .end
 527                                .cmp(&next_selection.start, buffer)
 528                                .unwrap()
 529                                .is_ge()
 530                            {
 531                                let next_selection = selections.next().unwrap();
 532                                if next_selection
 533                                    .end
 534                                    .cmp(&selection.end, buffer)
 535                                    .unwrap()
 536                                    .is_ge()
 537                                {
 538                                    selection.end = next_selection.end;
 539                                }
 540                            } else {
 541                                break;
 542                            }
 543                        }
 544                        Some(selection)
 545                    }));
 546                    buffer.set_active_selections(merged_selections, cx);
 547                });
 548        }
 549    }
 550
 551    pub fn remove_active_selections(&mut self, cx: &mut ModelContext<Self>) {
 552        for buffer in self.buffers.borrow().values() {
 553            buffer
 554                .buffer
 555                .update(cx, |buffer, cx| buffer.remove_active_selections(cx));
 556        }
 557    }
 558
 559    pub fn undo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 560        if let Some(buffer) = self.as_singleton() {
 561            return buffer.update(cx, |buffer, cx| buffer.undo(cx));
 562        }
 563
 564        while let Some(transaction) = self.history.pop_undo() {
 565            let mut undone = false;
 566            for (buffer_id, buffer_transaction_id) in &transaction.buffer_transactions {
 567                if let Some(BufferState { buffer, .. }) = self.buffers.borrow().get(&buffer_id) {
 568                    undone |= buffer.update(cx, |buf, cx| {
 569                        buf.undo_transaction(*buffer_transaction_id, cx)
 570                    });
 571                }
 572            }
 573
 574            if undone {
 575                return Some(transaction.id);
 576            }
 577        }
 578
 579        None
 580    }
 581
 582    pub fn redo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 583        if let Some(buffer) = self.as_singleton() {
 584            return buffer.update(cx, |buffer, cx| buffer.redo(cx));
 585        }
 586
 587        while let Some(transaction) = self.history.pop_redo() {
 588            let mut redone = false;
 589            for (buffer_id, buffer_transaction_id) in &transaction.buffer_transactions {
 590                if let Some(BufferState { buffer, .. }) = self.buffers.borrow().get(&buffer_id) {
 591                    redone |= buffer.update(cx, |buf, cx| {
 592                        buf.redo_transaction(*buffer_transaction_id, cx)
 593                    });
 594                }
 595            }
 596
 597            if redone {
 598                return Some(transaction.id);
 599            }
 600        }
 601
 602        None
 603    }
 604
 605    pub fn push_excerpt<O>(
 606        &mut self,
 607        props: ExcerptProperties<O>,
 608        cx: &mut ModelContext<Self>,
 609    ) -> ExcerptId
 610    where
 611        O: text::ToOffset,
 612    {
 613        self.insert_excerpt_after(&ExcerptId::max(), props, cx)
 614    }
 615
 616    pub fn insert_excerpt_after<O>(
 617        &mut self,
 618        prev_excerpt_id: &ExcerptId,
 619        props: ExcerptProperties<O>,
 620        cx: &mut ModelContext<Self>,
 621    ) -> ExcerptId
 622    where
 623        O: text::ToOffset,
 624    {
 625        assert_eq!(self.history.transaction_depth, 0);
 626        self.sync(cx);
 627
 628        let buffer_snapshot = props.buffer.read(cx).snapshot();
 629        let range = buffer_snapshot.anchor_before(&props.range.start)
 630            ..buffer_snapshot.anchor_after(&props.range.end);
 631        let mut snapshot = self.snapshot.borrow_mut();
 632        let mut cursor = snapshot.excerpts.cursor::<Option<&ExcerptId>>();
 633        let mut new_excerpts = cursor.slice(&Some(prev_excerpt_id), Bias::Right, &());
 634
 635        let mut prev_id = ExcerptId::min();
 636        let edit_start = new_excerpts.summary().text.bytes;
 637        new_excerpts.update_last(
 638            |excerpt| {
 639                excerpt.has_trailing_newline = true;
 640                prev_id = excerpt.id.clone();
 641            },
 642            &(),
 643        );
 644
 645        let mut next_id = ExcerptId::max();
 646        if let Some(next_excerpt) = cursor.item() {
 647            next_id = next_excerpt.id.clone();
 648        }
 649
 650        let id = ExcerptId::between(&prev_id, &next_id);
 651
 652        let mut buffers = self.buffers.borrow_mut();
 653        let buffer_state = buffers
 654            .entry(props.buffer.id())
 655            .or_insert_with(|| BufferState {
 656                last_version: buffer_snapshot.version().clone(),
 657                last_parse_count: buffer_snapshot.parse_count(),
 658                last_selections_update_count: buffer_snapshot.selections_update_count(),
 659                last_diagnostics_update_count: buffer_snapshot.diagnostics_update_count(),
 660                excerpts: Default::default(),
 661                _subscriptions: [
 662                    cx.observe(&props.buffer, |_, _, cx| cx.notify()),
 663                    cx.subscribe(&props.buffer, Self::on_buffer_event),
 664                ],
 665                buffer: props.buffer.clone(),
 666            });
 667        if let Err(ix) = buffer_state.excerpts.binary_search(&id) {
 668            buffer_state.excerpts.insert(ix, id.clone());
 669        }
 670
 671        let excerpt = Excerpt::new(
 672            id.clone(),
 673            props.buffer.id(),
 674            buffer_snapshot,
 675            range,
 676            cursor.item().is_some(),
 677        );
 678        new_excerpts.push(excerpt, &());
 679        let edit_end = new_excerpts.summary().text.bytes;
 680
 681        new_excerpts.push_tree(cursor.suffix(&()), &());
 682        drop(cursor);
 683        snapshot.excerpts = new_excerpts;
 684
 685        self.subscriptions.publish_mut([Edit {
 686            old: edit_start..edit_start,
 687            new: edit_start..edit_end,
 688        }]);
 689
 690        cx.notify();
 691        id
 692    }
 693
 694    pub fn excerpt_ids_for_buffer(&self, buffer: &ModelHandle<Buffer>) -> Vec<ExcerptId> {
 695        self.buffers
 696            .borrow()
 697            .get(&buffer.id())
 698            .map_or(Vec::new(), |state| state.excerpts.clone())
 699    }
 700
 701    pub fn excerpted_buffers<'a, T: ToOffset>(
 702        &'a self,
 703        range: Range<T>,
 704        cx: &AppContext,
 705    ) -> Vec<(ModelHandle<Buffer>, Range<usize>)> {
 706        let snapshot = self.snapshot(cx);
 707        let start = range.start.to_offset(&snapshot);
 708        let end = range.end.to_offset(&snapshot);
 709
 710        let mut result = Vec::new();
 711        let mut cursor = snapshot.excerpts.cursor::<usize>();
 712        cursor.seek(&start, Bias::Right, &());
 713        while let Some(excerpt) = cursor.item() {
 714            if *cursor.start() > end {
 715                break;
 716            }
 717
 718            let mut end_before_newline = cursor.end(&());
 719            if excerpt.has_trailing_newline {
 720                end_before_newline -= 1;
 721            }
 722            let excerpt_start = excerpt.range.start.to_offset(&excerpt.buffer);
 723            let start = excerpt_start + (cmp::max(start, *cursor.start()) - *cursor.start());
 724            let end = excerpt_start + (cmp::min(end, end_before_newline) - *cursor.start());
 725            let buffer = self.buffers.borrow()[&excerpt.buffer_id].buffer.clone();
 726            result.push((buffer, start..end));
 727            cursor.next(&());
 728        }
 729
 730        result
 731    }
 732
 733    pub fn remove_excerpts<'a>(
 734        &mut self,
 735        excerpt_ids: impl IntoIterator<Item = &'a ExcerptId>,
 736        cx: &mut ModelContext<Self>,
 737    ) {
 738        let mut buffers = self.buffers.borrow_mut();
 739        let mut snapshot = self.snapshot.borrow_mut();
 740        let mut new_excerpts = SumTree::new();
 741        let mut cursor = snapshot.excerpts.cursor::<(Option<&ExcerptId>, usize)>();
 742        let mut edits = Vec::new();
 743        let mut excerpt_ids = excerpt_ids.into_iter().peekable();
 744
 745        while let Some(mut excerpt_id) = excerpt_ids.next() {
 746            // Seek to the next excerpt to remove, preserving any preceding excerpts.
 747            new_excerpts.push_tree(cursor.slice(&Some(excerpt_id), Bias::Left, &()), &());
 748            if let Some(mut excerpt) = cursor.item() {
 749                if excerpt.id != *excerpt_id {
 750                    continue;
 751                }
 752                let mut old_start = cursor.start().1;
 753
 754                // Skip over the removed excerpt.
 755                loop {
 756                    if let Some(buffer_state) = buffers.get_mut(&excerpt.buffer_id) {
 757                        buffer_state.excerpts.retain(|id| id != excerpt_id);
 758                        if buffer_state.excerpts.is_empty() {
 759                            buffers.remove(&excerpt.buffer_id);
 760                        }
 761                    }
 762                    cursor.next(&());
 763
 764                    // Skip over any subsequent excerpts that are also removed.
 765                    if let Some(&next_excerpt_id) = excerpt_ids.peek() {
 766                        if let Some(next_excerpt) = cursor.item() {
 767                            if next_excerpt.id == *next_excerpt_id {
 768                                excerpt = next_excerpt;
 769                                excerpt_id = excerpt_ids.next().unwrap();
 770                                continue;
 771                            }
 772                        }
 773                    }
 774
 775                    break;
 776                }
 777
 778                // When removing the last excerpt, remove the trailing newline from
 779                // the previous excerpt.
 780                if cursor.item().is_none() && old_start > 0 {
 781                    old_start -= 1;
 782                    new_excerpts.update_last(|e| e.has_trailing_newline = false, &());
 783                }
 784
 785                // Push an edit for the removal of this run of excerpts.
 786                let old_end = cursor.start().1;
 787                let new_start = new_excerpts.summary().text.bytes;
 788                edits.push(Edit {
 789                    old: old_start..old_end,
 790                    new: new_start..new_start,
 791                });
 792            }
 793        }
 794        new_excerpts.push_tree(cursor.suffix(&()), &());
 795        drop(cursor);
 796        snapshot.excerpts = new_excerpts;
 797        self.subscriptions.publish_mut(edits);
 798        cx.notify();
 799    }
 800
 801    pub fn text_anchor_for_position<'a, T: ToOffset>(
 802        &'a self,
 803        position: T,
 804        cx: &AppContext,
 805    ) -> (ModelHandle<Buffer>, language::Anchor) {
 806        let snapshot = self.read(cx);
 807        let anchor = snapshot.anchor_before(position);
 808        (
 809            self.buffers.borrow()[&anchor.buffer_id].buffer.clone(),
 810            anchor.text_anchor,
 811        )
 812    }
 813
 814    fn on_buffer_event(
 815        &mut self,
 816        _: ModelHandle<Buffer>,
 817        event: &Event,
 818        cx: &mut ModelContext<Self>,
 819    ) {
 820        cx.emit(event.clone());
 821    }
 822
 823    pub fn format(&mut self, cx: &mut ModelContext<Self>) -> Task<Result<()>> {
 824        let mut format_tasks = Vec::new();
 825        for BufferState { buffer, .. } in self.buffers.borrow().values() {
 826            format_tasks.push(buffer.update(cx, |buffer, cx| buffer.format(cx)));
 827        }
 828
 829        cx.spawn(|_, _| async move {
 830            for format in format_tasks {
 831                format.await?;
 832            }
 833            Ok(())
 834        })
 835    }
 836
 837    pub fn save(&mut self, cx: &mut ModelContext<Self>) -> Task<Result<()>> {
 838        let mut save_tasks = Vec::new();
 839        for BufferState { buffer, .. } in self.buffers.borrow().values() {
 840            save_tasks.push(buffer.update(cx, |buffer, cx| buffer.save(cx)));
 841        }
 842
 843        cx.spawn(|_, _| async move {
 844            for save in save_tasks {
 845                save.await?;
 846            }
 847            Ok(())
 848        })
 849    }
 850
 851    pub fn completions<T>(
 852        &self,
 853        position: T,
 854        cx: &mut ModelContext<Self>,
 855    ) -> Task<Result<Vec<Completion<Anchor>>>>
 856    where
 857        T: ToOffset,
 858    {
 859        let snapshot = self.snapshot(cx);
 860        let anchor = snapshot.anchor_before(position);
 861        let buffer = self.buffers.borrow()[&anchor.buffer_id].buffer.clone();
 862        let completions =
 863            buffer.update(cx, |buffer, cx| buffer.completions(anchor.text_anchor, cx));
 864        cx.foreground().spawn(async move {
 865            completions.await.map(|completions| {
 866                completions
 867                    .into_iter()
 868                    .map(|completion| Completion {
 869                        old_range: snapshot.anchor_in_excerpt(
 870                            anchor.excerpt_id.clone(),
 871                            completion.old_range.start,
 872                        )
 873                            ..snapshot.anchor_in_excerpt(
 874                                anchor.excerpt_id.clone(),
 875                                completion.old_range.end,
 876                            ),
 877                        new_text: completion.new_text,
 878                        lsp_completion: completion.lsp_completion,
 879                    })
 880                    .collect()
 881            })
 882        })
 883    }
 884
 885    pub fn language<'a>(&self, cx: &'a AppContext) -> Option<&'a Arc<Language>> {
 886        self.buffers
 887            .borrow()
 888            .values()
 889            .next()
 890            .and_then(|state| state.buffer.read(cx).language())
 891    }
 892
 893    pub fn file<'a>(&self, cx: &'a AppContext) -> Option<&'a dyn File> {
 894        self.as_singleton()?.read(cx).file()
 895    }
 896
 897    #[cfg(test)]
 898    pub fn is_parsing(&self, cx: &AppContext) -> bool {
 899        self.as_singleton().unwrap().read(cx).is_parsing()
 900    }
 901
 902    fn sync(&self, cx: &AppContext) {
 903        let mut snapshot = self.snapshot.borrow_mut();
 904        let mut excerpts_to_edit = Vec::new();
 905        let mut reparsed = false;
 906        let mut diagnostics_updated = false;
 907        let mut is_dirty = false;
 908        let mut has_conflict = false;
 909        let mut buffers = self.buffers.borrow_mut();
 910        for buffer_state in buffers.values_mut() {
 911            let buffer = buffer_state.buffer.read(cx);
 912            let version = buffer.version();
 913            let parse_count = buffer.parse_count();
 914            let selections_update_count = buffer.selections_update_count();
 915            let diagnostics_update_count = buffer.diagnostics_update_count();
 916
 917            let buffer_edited = version.changed_since(&buffer_state.last_version);
 918            let buffer_reparsed = parse_count > buffer_state.last_parse_count;
 919            let buffer_selections_updated =
 920                selections_update_count > buffer_state.last_selections_update_count;
 921            let buffer_diagnostics_updated =
 922                diagnostics_update_count > buffer_state.last_diagnostics_update_count;
 923            if buffer_edited
 924                || buffer_reparsed
 925                || buffer_selections_updated
 926                || buffer_diagnostics_updated
 927            {
 928                buffer_state.last_version = version;
 929                buffer_state.last_parse_count = parse_count;
 930                buffer_state.last_selections_update_count = selections_update_count;
 931                buffer_state.last_diagnostics_update_count = diagnostics_update_count;
 932                excerpts_to_edit.extend(
 933                    buffer_state
 934                        .excerpts
 935                        .iter()
 936                        .map(|excerpt_id| (excerpt_id, buffer_state.buffer.clone(), buffer_edited)),
 937                );
 938            }
 939
 940            reparsed |= buffer_reparsed;
 941            diagnostics_updated |= buffer_diagnostics_updated;
 942            is_dirty |= buffer.is_dirty();
 943            has_conflict |= buffer.has_conflict();
 944        }
 945        if reparsed {
 946            snapshot.parse_count += 1;
 947        }
 948        if diagnostics_updated {
 949            snapshot.diagnostics_update_count += 1;
 950        }
 951        snapshot.is_dirty = is_dirty;
 952        snapshot.has_conflict = has_conflict;
 953
 954        excerpts_to_edit.sort_unstable_by_key(|(excerpt_id, _, _)| *excerpt_id);
 955
 956        let mut edits = Vec::new();
 957        let mut new_excerpts = SumTree::new();
 958        let mut cursor = snapshot.excerpts.cursor::<(Option<&ExcerptId>, usize)>();
 959
 960        for (id, buffer, buffer_edited) in excerpts_to_edit {
 961            new_excerpts.push_tree(cursor.slice(&Some(id), Bias::Left, &()), &());
 962            let old_excerpt = cursor.item().unwrap();
 963            let buffer_id = buffer.id();
 964            let buffer = buffer.read(cx);
 965
 966            let mut new_excerpt;
 967            if buffer_edited {
 968                edits.extend(
 969                    buffer
 970                        .edits_since_in_range::<usize>(
 971                            old_excerpt.buffer.version(),
 972                            old_excerpt.range.clone(),
 973                        )
 974                        .map(|mut edit| {
 975                            let excerpt_old_start = cursor.start().1;
 976                            let excerpt_new_start = new_excerpts.summary().text.bytes;
 977                            edit.old.start += excerpt_old_start;
 978                            edit.old.end += excerpt_old_start;
 979                            edit.new.start += excerpt_new_start;
 980                            edit.new.end += excerpt_new_start;
 981                            edit
 982                        }),
 983                );
 984
 985                new_excerpt = Excerpt::new(
 986                    id.clone(),
 987                    buffer_id,
 988                    buffer.snapshot(),
 989                    old_excerpt.range.clone(),
 990                    old_excerpt.has_trailing_newline,
 991                );
 992            } else {
 993                new_excerpt = old_excerpt.clone();
 994                new_excerpt.buffer = buffer.snapshot();
 995            }
 996
 997            new_excerpts.push(new_excerpt, &());
 998            cursor.next(&());
 999        }
1000        new_excerpts.push_tree(cursor.suffix(&()), &());
1001
1002        drop(cursor);
1003        snapshot.excerpts = new_excerpts;
1004
1005        self.subscriptions.publish(edits);
1006    }
1007}
1008
1009#[cfg(any(test, feature = "test-support"))]
1010impl MultiBuffer {
1011    pub fn randomly_edit(
1012        &mut self,
1013        rng: &mut impl rand::Rng,
1014        count: usize,
1015        cx: &mut ModelContext<Self>,
1016    ) {
1017        use text::RandomCharIter;
1018
1019        let snapshot = self.read(cx);
1020        let mut old_ranges: Vec<Range<usize>> = Vec::new();
1021        for _ in 0..count {
1022            let last_end = old_ranges.last().map_or(0, |last_range| last_range.end + 1);
1023            if last_end > snapshot.len() {
1024                break;
1025            }
1026            let end_ix = snapshot.clip_offset(rng.gen_range(0..=last_end), Bias::Right);
1027            let start_ix = snapshot.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
1028            old_ranges.push(start_ix..end_ix);
1029        }
1030        let new_text_len = rng.gen_range(0..10);
1031        let new_text: String = RandomCharIter::new(&mut *rng).take(new_text_len).collect();
1032        log::info!("mutating multi-buffer at {:?}: {:?}", old_ranges, new_text);
1033        drop(snapshot);
1034
1035        self.edit(old_ranges.iter().cloned(), new_text.as_str(), cx);
1036    }
1037}
1038
1039impl Entity for MultiBuffer {
1040    type Event = language::Event;
1041}
1042
1043impl MultiBufferSnapshot {
1044    pub fn text(&self) -> String {
1045        self.chunks(0..self.len(), None)
1046            .map(|chunk| chunk.text)
1047            .collect()
1048    }
1049
1050    pub fn reversed_chars_at<'a, T: ToOffset>(
1051        &'a self,
1052        position: T,
1053    ) -> impl Iterator<Item = char> + 'a {
1054        let mut offset = position.to_offset(self);
1055        let mut cursor = self.excerpts.cursor::<usize>();
1056        cursor.seek(&offset, Bias::Left, &());
1057        let mut excerpt_chunks = cursor.item().map(|excerpt| {
1058            let end_before_footer = cursor.start() + excerpt.text_summary.bytes;
1059            let start = excerpt.range.start.to_offset(&excerpt.buffer);
1060            let end = start + (cmp::min(offset, end_before_footer) - cursor.start());
1061            excerpt.buffer.reversed_chunks_in_range(start..end)
1062        });
1063        iter::from_fn(move || {
1064            if offset == *cursor.start() {
1065                cursor.prev(&());
1066                let excerpt = cursor.item()?;
1067                excerpt_chunks = Some(
1068                    excerpt
1069                        .buffer
1070                        .reversed_chunks_in_range(excerpt.range.clone()),
1071                );
1072            }
1073
1074            let excerpt = cursor.item().unwrap();
1075            if offset == cursor.end(&()) && excerpt.has_trailing_newline {
1076                offset -= 1;
1077                Some("\n")
1078            } else {
1079                let chunk = excerpt_chunks.as_mut().unwrap().next().unwrap();
1080                offset -= chunk.len();
1081                Some(chunk)
1082            }
1083        })
1084        .flat_map(|c| c.chars().rev())
1085    }
1086
1087    pub fn chars_at<'a, T: ToOffset>(&'a self, position: T) -> impl Iterator<Item = char> + 'a {
1088        let offset = position.to_offset(self);
1089        self.text_for_range(offset..self.len())
1090            .flat_map(|chunk| chunk.chars())
1091    }
1092
1093    pub fn text_for_range<'a, T: ToOffset>(
1094        &'a self,
1095        range: Range<T>,
1096    ) -> impl Iterator<Item = &'a str> {
1097        self.chunks(range, None).map(|chunk| chunk.text)
1098    }
1099
1100    pub fn is_line_blank(&self, row: u32) -> bool {
1101        self.text_for_range(Point::new(row, 0)..Point::new(row, self.line_len(row)))
1102            .all(|chunk| chunk.matches(|c: char| !c.is_whitespace()).next().is_none())
1103    }
1104
1105    pub fn contains_str_at<T>(&self, position: T, needle: &str) -> bool
1106    where
1107        T: ToOffset,
1108    {
1109        let position = position.to_offset(self);
1110        position == self.clip_offset(position, Bias::Left)
1111            && self
1112                .bytes_in_range(position..self.len())
1113                .flatten()
1114                .copied()
1115                .take(needle.len())
1116                .eq(needle.bytes())
1117    }
1118
1119    fn as_singleton(&self) -> Option<&Excerpt> {
1120        if self.singleton {
1121            self.excerpts.iter().next()
1122        } else {
1123            None
1124        }
1125    }
1126
1127    pub fn len(&self) -> usize {
1128        self.excerpts.summary().text.bytes
1129    }
1130
1131    pub fn max_buffer_row(&self) -> u32 {
1132        self.excerpts.summary().max_buffer_row
1133    }
1134
1135    pub fn clip_offset(&self, offset: usize, bias: Bias) -> usize {
1136        if let Some(excerpt) = self.as_singleton() {
1137            return excerpt.buffer.clip_offset(offset, bias);
1138        }
1139
1140        let mut cursor = self.excerpts.cursor::<usize>();
1141        cursor.seek(&offset, Bias::Right, &());
1142        let overshoot = if let Some(excerpt) = cursor.item() {
1143            let excerpt_start = excerpt.range.start.to_offset(&excerpt.buffer);
1144            let buffer_offset = excerpt
1145                .buffer
1146                .clip_offset(excerpt_start + (offset - cursor.start()), bias);
1147            buffer_offset.saturating_sub(excerpt_start)
1148        } else {
1149            0
1150        };
1151        cursor.start() + overshoot
1152    }
1153
1154    pub fn clip_point(&self, point: Point, bias: Bias) -> Point {
1155        if let Some(excerpt) = self.as_singleton() {
1156            return excerpt.buffer.clip_point(point, bias);
1157        }
1158
1159        let mut cursor = self.excerpts.cursor::<Point>();
1160        cursor.seek(&point, Bias::Right, &());
1161        let overshoot = if let Some(excerpt) = cursor.item() {
1162            let excerpt_start = excerpt.range.start.to_point(&excerpt.buffer);
1163            let buffer_point = excerpt
1164                .buffer
1165                .clip_point(excerpt_start + (point - cursor.start()), bias);
1166            buffer_point.saturating_sub(excerpt_start)
1167        } else {
1168            Point::zero()
1169        };
1170        *cursor.start() + overshoot
1171    }
1172
1173    pub fn clip_point_utf16(&self, point: PointUtf16, bias: Bias) -> PointUtf16 {
1174        if let Some(excerpt) = self.as_singleton() {
1175            return excerpt.buffer.clip_point_utf16(point, bias);
1176        }
1177
1178        let mut cursor = self.excerpts.cursor::<PointUtf16>();
1179        cursor.seek(&point, Bias::Right, &());
1180        let overshoot = if let Some(excerpt) = cursor.item() {
1181            let excerpt_start = excerpt
1182                .buffer
1183                .offset_to_point_utf16(excerpt.range.start.to_offset(&excerpt.buffer));
1184            let buffer_point = excerpt
1185                .buffer
1186                .clip_point_utf16(excerpt_start + (point - cursor.start()), bias);
1187            buffer_point.saturating_sub(excerpt_start)
1188        } else {
1189            PointUtf16::zero()
1190        };
1191        *cursor.start() + overshoot
1192    }
1193
1194    pub fn bytes_in_range<'a, T: ToOffset>(&'a self, range: Range<T>) -> MultiBufferBytes<'a> {
1195        let range = range.start.to_offset(self)..range.end.to_offset(self);
1196        let mut excerpts = self.excerpts.cursor::<usize>();
1197        excerpts.seek(&range.start, Bias::Right, &());
1198
1199        let mut chunk = &[][..];
1200        let excerpt_bytes = if let Some(excerpt) = excerpts.item() {
1201            let mut excerpt_bytes = excerpt
1202                .bytes_in_range(range.start - excerpts.start()..range.end - excerpts.start());
1203            chunk = excerpt_bytes.next().unwrap_or(&[][..]);
1204            Some(excerpt_bytes)
1205        } else {
1206            None
1207        };
1208
1209        MultiBufferBytes {
1210            range,
1211            excerpts,
1212            excerpt_bytes,
1213            chunk,
1214        }
1215    }
1216
1217    pub fn buffer_rows<'a>(&'a self, start_row: u32) -> MultiBufferRows<'a> {
1218        let mut result = MultiBufferRows {
1219            buffer_row_range: 0..0,
1220            excerpts: self.excerpts.cursor(),
1221        };
1222        result.seek(start_row);
1223        result
1224    }
1225
1226    pub fn chunks<'a, T: ToOffset>(
1227        &'a self,
1228        range: Range<T>,
1229        theme: Option<&'a SyntaxTheme>,
1230    ) -> MultiBufferChunks<'a> {
1231        let range = range.start.to_offset(self)..range.end.to_offset(self);
1232        let mut chunks = MultiBufferChunks {
1233            range: range.clone(),
1234            excerpts: self.excerpts.cursor(),
1235            excerpt_chunks: None,
1236            theme,
1237        };
1238        chunks.seek(range.start);
1239        chunks
1240    }
1241
1242    pub fn offset_to_point(&self, offset: usize) -> Point {
1243        if let Some(excerpt) = self.as_singleton() {
1244            return excerpt.buffer.offset_to_point(offset);
1245        }
1246
1247        let mut cursor = self.excerpts.cursor::<(usize, Point)>();
1248        cursor.seek(&offset, Bias::Right, &());
1249        if let Some(excerpt) = cursor.item() {
1250            let (start_offset, start_point) = cursor.start();
1251            let overshoot = offset - start_offset;
1252            let excerpt_start_offset = excerpt.range.start.to_offset(&excerpt.buffer);
1253            let excerpt_start_point = excerpt.range.start.to_point(&excerpt.buffer);
1254            let buffer_point = excerpt
1255                .buffer
1256                .offset_to_point(excerpt_start_offset + overshoot);
1257            *start_point + (buffer_point - excerpt_start_point)
1258        } else {
1259            self.excerpts.summary().text.lines
1260        }
1261    }
1262
1263    pub fn point_to_offset(&self, point: Point) -> usize {
1264        if let Some(excerpt) = self.as_singleton() {
1265            return excerpt.buffer.point_to_offset(point);
1266        }
1267
1268        let mut cursor = self.excerpts.cursor::<(Point, usize)>();
1269        cursor.seek(&point, Bias::Right, &());
1270        if let Some(excerpt) = cursor.item() {
1271            let (start_point, start_offset) = cursor.start();
1272            let overshoot = point - start_point;
1273            let excerpt_start_offset = excerpt.range.start.to_offset(&excerpt.buffer);
1274            let excerpt_start_point = excerpt.range.start.to_point(&excerpt.buffer);
1275            let buffer_offset = excerpt
1276                .buffer
1277                .point_to_offset(excerpt_start_point + overshoot);
1278            *start_offset + buffer_offset - excerpt_start_offset
1279        } else {
1280            self.excerpts.summary().text.bytes
1281        }
1282    }
1283
1284    pub fn point_utf16_to_offset(&self, point: PointUtf16) -> usize {
1285        if let Some(excerpt) = self.as_singleton() {
1286            return excerpt.buffer.point_utf16_to_offset(point);
1287        }
1288
1289        let mut cursor = self.excerpts.cursor::<(PointUtf16, usize)>();
1290        cursor.seek(&point, Bias::Right, &());
1291        if let Some(excerpt) = cursor.item() {
1292            let (start_point, start_offset) = cursor.start();
1293            let overshoot = point - start_point;
1294            let excerpt_start_offset = excerpt.range.start.to_offset(&excerpt.buffer);
1295            let excerpt_start_point = excerpt
1296                .buffer
1297                .offset_to_point_utf16(excerpt.range.start.to_offset(&excerpt.buffer));
1298            let buffer_offset = excerpt
1299                .buffer
1300                .point_utf16_to_offset(excerpt_start_point + overshoot);
1301            *start_offset + (buffer_offset - excerpt_start_offset)
1302        } else {
1303            self.excerpts.summary().text.bytes
1304        }
1305    }
1306
1307    pub fn indent_column_for_line(&self, row: u32) -> u32 {
1308        if let Some((buffer, range)) = self.buffer_line_for_row(row) {
1309            buffer
1310                .indent_column_for_line(range.start.row)
1311                .min(range.end.column)
1312                .saturating_sub(range.start.column)
1313        } else {
1314            0
1315        }
1316    }
1317
1318    pub fn line_len(&self, row: u32) -> u32 {
1319        if let Some((_, range)) = self.buffer_line_for_row(row) {
1320            range.end.column - range.start.column
1321        } else {
1322            0
1323        }
1324    }
1325
1326    fn buffer_line_for_row(&self, row: u32) -> Option<(&BufferSnapshot, Range<Point>)> {
1327        let mut cursor = self.excerpts.cursor::<Point>();
1328        cursor.seek(&Point::new(row, 0), Bias::Right, &());
1329        if let Some(excerpt) = cursor.item() {
1330            let overshoot = row - cursor.start().row;
1331            let excerpt_start = excerpt.range.start.to_point(&excerpt.buffer);
1332            let excerpt_end = excerpt.range.end.to_point(&excerpt.buffer);
1333            let buffer_row = excerpt_start.row + overshoot;
1334            let line_start = Point::new(buffer_row, 0);
1335            let line_end = Point::new(buffer_row, excerpt.buffer.line_len(buffer_row));
1336            return Some((
1337                &excerpt.buffer,
1338                line_start.max(excerpt_start)..line_end.min(excerpt_end),
1339            ));
1340        }
1341        None
1342    }
1343
1344    pub fn max_point(&self) -> Point {
1345        self.text_summary().lines
1346    }
1347
1348    pub fn text_summary(&self) -> TextSummary {
1349        self.excerpts.summary().text
1350    }
1351
1352    pub fn text_summary_for_range<'a, D, O>(&'a self, range: Range<O>) -> D
1353    where
1354        D: TextDimension,
1355        O: ToOffset,
1356    {
1357        let mut summary = D::default();
1358        let mut range = range.start.to_offset(self)..range.end.to_offset(self);
1359        let mut cursor = self.excerpts.cursor::<usize>();
1360        cursor.seek(&range.start, Bias::Right, &());
1361        if let Some(excerpt) = cursor.item() {
1362            let mut end_before_newline = cursor.end(&());
1363            if excerpt.has_trailing_newline {
1364                end_before_newline -= 1;
1365            }
1366
1367            let excerpt_start = excerpt.range.start.to_offset(&excerpt.buffer);
1368            let start_in_excerpt = excerpt_start + (range.start - cursor.start());
1369            let end_in_excerpt =
1370                excerpt_start + (cmp::min(end_before_newline, range.end) - cursor.start());
1371            summary.add_assign(
1372                &excerpt
1373                    .buffer
1374                    .text_summary_for_range(start_in_excerpt..end_in_excerpt),
1375            );
1376
1377            if range.end > end_before_newline {
1378                summary.add_assign(&D::from_text_summary(&TextSummary {
1379                    bytes: 1,
1380                    lines: Point::new(1 as u32, 0),
1381                    lines_utf16: PointUtf16::new(1 as u32, 0),
1382                    first_line_chars: 0,
1383                    last_line_chars: 0,
1384                    longest_row: 0,
1385                    longest_row_chars: 0,
1386                }));
1387            }
1388
1389            cursor.next(&());
1390        }
1391
1392        if range.end > *cursor.start() {
1393            summary.add_assign(&D::from_text_summary(&cursor.summary::<_, TextSummary>(
1394                &range.end,
1395                Bias::Right,
1396                &(),
1397            )));
1398            if let Some(excerpt) = cursor.item() {
1399                range.end = cmp::max(*cursor.start(), range.end);
1400
1401                let excerpt_start = excerpt.range.start.to_offset(&excerpt.buffer);
1402                let end_in_excerpt = excerpt_start + (range.end - cursor.start());
1403                summary.add_assign(
1404                    &excerpt
1405                        .buffer
1406                        .text_summary_for_range(excerpt_start..end_in_excerpt),
1407                );
1408            }
1409        }
1410
1411        summary
1412    }
1413
1414    pub fn summary_for_anchor<D>(&self, anchor: &Anchor) -> D
1415    where
1416        D: TextDimension + Ord + Sub<D, Output = D>,
1417    {
1418        let mut cursor = self.excerpts.cursor::<ExcerptSummary>();
1419        cursor.seek(&Some(&anchor.excerpt_id), Bias::Left, &());
1420        if cursor.item().is_none() {
1421            cursor.next(&());
1422        }
1423
1424        let mut position = D::from_text_summary(&cursor.start().text);
1425        if let Some(excerpt) = cursor.item() {
1426            if excerpt.id == anchor.excerpt_id && excerpt.buffer_id == anchor.buffer_id {
1427                let excerpt_buffer_start = excerpt.range.start.summary::<D>(&excerpt.buffer);
1428                let excerpt_buffer_end = excerpt.range.end.summary::<D>(&excerpt.buffer);
1429                let buffer_position = cmp::min(
1430                    excerpt_buffer_end,
1431                    anchor.text_anchor.summary::<D>(&excerpt.buffer),
1432                );
1433                if buffer_position > excerpt_buffer_start {
1434                    position.add_assign(&(buffer_position - excerpt_buffer_start));
1435                }
1436            }
1437        }
1438        position
1439    }
1440
1441    pub fn summaries_for_anchors<'a, D, I>(&'a self, anchors: I) -> Vec<D>
1442    where
1443        D: TextDimension + Ord + Sub<D, Output = D>,
1444        I: 'a + IntoIterator<Item = &'a Anchor>,
1445    {
1446        let mut anchors = anchors.into_iter().peekable();
1447        let mut cursor = self.excerpts.cursor::<ExcerptSummary>();
1448        let mut summaries = Vec::new();
1449        while let Some(anchor) = anchors.peek() {
1450            let excerpt_id = &anchor.excerpt_id;
1451            let buffer_id = anchor.buffer_id;
1452            let excerpt_anchors = iter::from_fn(|| {
1453                let anchor = anchors.peek()?;
1454                if anchor.excerpt_id == *excerpt_id && anchor.buffer_id == buffer_id {
1455                    Some(&anchors.next().unwrap().text_anchor)
1456                } else {
1457                    None
1458                }
1459            });
1460
1461            cursor.seek_forward(&Some(excerpt_id), Bias::Left, &());
1462            if cursor.item().is_none() {
1463                cursor.next(&());
1464            }
1465
1466            let position = D::from_text_summary(&cursor.start().text);
1467            if let Some(excerpt) = cursor.item() {
1468                if excerpt.id == *excerpt_id && excerpt.buffer_id == buffer_id {
1469                    let excerpt_buffer_start = excerpt.range.start.summary::<D>(&excerpt.buffer);
1470                    let excerpt_buffer_end = excerpt.range.end.summary::<D>(&excerpt.buffer);
1471                    summaries.extend(
1472                        excerpt
1473                            .buffer
1474                            .summaries_for_anchors::<D, _>(excerpt_anchors)
1475                            .map(move |summary| {
1476                                let summary = cmp::min(excerpt_buffer_end.clone(), summary);
1477                                let mut position = position.clone();
1478                                let excerpt_buffer_start = excerpt_buffer_start.clone();
1479                                if summary > excerpt_buffer_start {
1480                                    position.add_assign(&(summary - excerpt_buffer_start));
1481                                }
1482                                position
1483                            }),
1484                    );
1485                    continue;
1486                }
1487            }
1488
1489            summaries.extend(excerpt_anchors.map(|_| position.clone()));
1490        }
1491
1492        summaries
1493    }
1494
1495    pub fn refresh_anchors<'a, I>(&'a self, anchors: I) -> Vec<(usize, Anchor, bool)>
1496    where
1497        I: 'a + IntoIterator<Item = &'a Anchor>,
1498    {
1499        let mut anchors = anchors.into_iter().enumerate().peekable();
1500        let mut cursor = self.excerpts.cursor::<Option<&ExcerptId>>();
1501        let mut result = Vec::new();
1502        while let Some((_, anchor)) = anchors.peek() {
1503            let old_excerpt_id = &anchor.excerpt_id;
1504
1505            // Find the location where this anchor's excerpt should be.
1506            cursor.seek_forward(&Some(old_excerpt_id), Bias::Left, &());
1507            if cursor.item().is_none() {
1508                cursor.next(&());
1509            }
1510
1511            let next_excerpt = cursor.item();
1512            let prev_excerpt = cursor.prev_item();
1513
1514            // Process all of the anchors for this excerpt.
1515            while let Some((_, anchor)) = anchors.peek() {
1516                if anchor.excerpt_id != *old_excerpt_id {
1517                    break;
1518                }
1519                let mut kept_position = false;
1520                let (anchor_ix, anchor) = anchors.next().unwrap();
1521                let mut anchor = anchor.clone();
1522
1523                // Leave min and max anchors unchanged.
1524                if *old_excerpt_id == ExcerptId::max() || *old_excerpt_id == ExcerptId::min() {
1525                    kept_position = true;
1526                }
1527                // If the old excerpt still exists at this location, then leave
1528                // the anchor unchanged.
1529                else if next_excerpt.map_or(false, |excerpt| {
1530                    excerpt.id == *old_excerpt_id && excerpt.contains(&anchor)
1531                }) {
1532                    kept_position = true;
1533                }
1534                // If the old excerpt no longer exists at this location, then attempt to
1535                // find an equivalent position for this anchor in an adjacent excerpt.
1536                else {
1537                    for excerpt in [next_excerpt, prev_excerpt].iter().filter_map(|e| *e) {
1538                        if excerpt.contains(&anchor) {
1539                            anchor.excerpt_id = excerpt.id.clone();
1540                            kept_position = true;
1541                            break;
1542                        }
1543                    }
1544                }
1545                // If there's no adjacent excerpt that contains the anchor's position,
1546                // then report that the anchor has lost its position.
1547                if !kept_position {
1548                    anchor = if let Some(excerpt) = next_excerpt {
1549                        let mut text_anchor = excerpt
1550                            .range
1551                            .start
1552                            .bias(anchor.text_anchor.bias, &excerpt.buffer);
1553                        if text_anchor
1554                            .cmp(&excerpt.range.end, &excerpt.buffer)
1555                            .unwrap()
1556                            .is_gt()
1557                        {
1558                            text_anchor = excerpt.range.end.clone();
1559                        }
1560                        Anchor {
1561                            buffer_id: excerpt.buffer_id,
1562                            excerpt_id: excerpt.id.clone(),
1563                            text_anchor,
1564                        }
1565                    } else if let Some(excerpt) = prev_excerpt {
1566                        let mut text_anchor = excerpt
1567                            .range
1568                            .end
1569                            .bias(anchor.text_anchor.bias, &excerpt.buffer);
1570                        if text_anchor
1571                            .cmp(&excerpt.range.start, &excerpt.buffer)
1572                            .unwrap()
1573                            .is_lt()
1574                        {
1575                            text_anchor = excerpt.range.start.clone();
1576                        }
1577                        Anchor {
1578                            buffer_id: excerpt.buffer_id,
1579                            excerpt_id: excerpt.id.clone(),
1580                            text_anchor,
1581                        }
1582                    } else if anchor.text_anchor.bias == Bias::Left {
1583                        Anchor::min()
1584                    } else {
1585                        Anchor::max()
1586                    };
1587                }
1588
1589                result.push((anchor_ix, anchor, kept_position));
1590            }
1591        }
1592        result.sort_unstable_by(|a, b| a.1.cmp(&b.1, self).unwrap());
1593        result
1594    }
1595
1596    pub fn anchor_before<T: ToOffset>(&self, position: T) -> Anchor {
1597        self.anchor_at(position, Bias::Left)
1598    }
1599
1600    pub fn anchor_after<T: ToOffset>(&self, position: T) -> Anchor {
1601        self.anchor_at(position, Bias::Right)
1602    }
1603
1604    pub fn anchor_at<T: ToOffset>(&self, position: T, mut bias: Bias) -> Anchor {
1605        let offset = position.to_offset(self);
1606        if let Some(excerpt) = self.as_singleton() {
1607            return Anchor {
1608                buffer_id: excerpt.buffer_id,
1609                excerpt_id: excerpt.id.clone(),
1610                text_anchor: excerpt.buffer.anchor_at(offset, bias),
1611            };
1612        }
1613
1614        let mut cursor = self.excerpts.cursor::<(usize, Option<&ExcerptId>)>();
1615        cursor.seek(&offset, Bias::Right, &());
1616        if cursor.item().is_none() && offset == cursor.start().0 && bias == Bias::Left {
1617            cursor.prev(&());
1618        }
1619        if let Some(excerpt) = cursor.item() {
1620            let mut overshoot = offset.saturating_sub(cursor.start().0);
1621            if excerpt.has_trailing_newline && offset == cursor.end(&()).0 {
1622                overshoot -= 1;
1623                bias = Bias::Right;
1624            }
1625
1626            let buffer_start = excerpt.range.start.to_offset(&excerpt.buffer);
1627            let text_anchor =
1628                excerpt.clip_anchor(excerpt.buffer.anchor_at(buffer_start + overshoot, bias));
1629            Anchor {
1630                buffer_id: excerpt.buffer_id,
1631                excerpt_id: excerpt.id.clone(),
1632                text_anchor,
1633            }
1634        } else if offset == 0 && bias == Bias::Left {
1635            Anchor::min()
1636        } else {
1637            Anchor::max()
1638        }
1639    }
1640
1641    pub fn anchor_in_excerpt(&self, excerpt_id: ExcerptId, text_anchor: text::Anchor) -> Anchor {
1642        let mut cursor = self.excerpts.cursor::<Option<&ExcerptId>>();
1643        cursor.seek(&Some(&excerpt_id), Bias::Left, &());
1644        if let Some(excerpt) = cursor.item() {
1645            if excerpt.id == excerpt_id {
1646                let text_anchor = excerpt.clip_anchor(text_anchor);
1647                drop(cursor);
1648                return Anchor {
1649                    buffer_id: excerpt.buffer_id,
1650                    excerpt_id,
1651                    text_anchor,
1652                };
1653            }
1654        }
1655        panic!("excerpt not found");
1656    }
1657
1658    pub fn can_resolve(&self, anchor: &Anchor) -> bool {
1659        if anchor.excerpt_id == ExcerptId::min() || anchor.excerpt_id == ExcerptId::max() {
1660            true
1661        } else if let Some((buffer_id, buffer_snapshot)) =
1662            self.buffer_snapshot_for_excerpt(&anchor.excerpt_id)
1663        {
1664            anchor.buffer_id == buffer_id && buffer_snapshot.can_resolve(&anchor.text_anchor)
1665        } else {
1666            false
1667        }
1668    }
1669
1670    pub fn range_contains_excerpt_boundary<T: ToOffset>(&self, range: Range<T>) -> bool {
1671        let start = range.start.to_offset(self);
1672        let end = range.end.to_offset(self);
1673        let mut cursor = self.excerpts.cursor::<(usize, Option<&ExcerptId>)>();
1674        cursor.seek(&start, Bias::Right, &());
1675        let start_id = cursor
1676            .item()
1677            .or_else(|| cursor.prev_item())
1678            .map(|excerpt| &excerpt.id);
1679        cursor.seek_forward(&end, Bias::Right, &());
1680        let end_id = cursor
1681            .item()
1682            .or_else(|| cursor.prev_item())
1683            .map(|excerpt| &excerpt.id);
1684        start_id != end_id
1685    }
1686
1687    pub fn parse_count(&self) -> usize {
1688        self.parse_count
1689    }
1690
1691    pub fn enclosing_bracket_ranges<T: ToOffset>(
1692        &self,
1693        range: Range<T>,
1694    ) -> Option<(Range<usize>, Range<usize>)> {
1695        let range = range.start.to_offset(self)..range.end.to_offset(self);
1696
1697        let mut cursor = self.excerpts.cursor::<usize>();
1698        cursor.seek(&range.start, Bias::Right, &());
1699        let start_excerpt = cursor.item();
1700
1701        cursor.seek(&range.end, Bias::Right, &());
1702        let end_excerpt = cursor.item();
1703
1704        start_excerpt
1705            .zip(end_excerpt)
1706            .and_then(|(start_excerpt, end_excerpt)| {
1707                if start_excerpt.id != end_excerpt.id {
1708                    return None;
1709                }
1710
1711                let excerpt_buffer_start =
1712                    start_excerpt.range.start.to_offset(&start_excerpt.buffer);
1713                let excerpt_buffer_end = excerpt_buffer_start + start_excerpt.text_summary.bytes;
1714
1715                let start_in_buffer =
1716                    excerpt_buffer_start + range.start.saturating_sub(*cursor.start());
1717                let end_in_buffer =
1718                    excerpt_buffer_start + range.end.saturating_sub(*cursor.start());
1719                let (mut start_bracket_range, mut end_bracket_range) = start_excerpt
1720                    .buffer
1721                    .enclosing_bracket_ranges(start_in_buffer..end_in_buffer)?;
1722
1723                if start_bracket_range.start >= excerpt_buffer_start
1724                    && end_bracket_range.end < excerpt_buffer_end
1725                {
1726                    start_bracket_range.start =
1727                        cursor.start() + (start_bracket_range.start - excerpt_buffer_start);
1728                    start_bracket_range.end =
1729                        cursor.start() + (start_bracket_range.end - excerpt_buffer_start);
1730                    end_bracket_range.start =
1731                        cursor.start() + (end_bracket_range.start - excerpt_buffer_start);
1732                    end_bracket_range.end =
1733                        cursor.start() + (end_bracket_range.end - excerpt_buffer_start);
1734                    Some((start_bracket_range, end_bracket_range))
1735                } else {
1736                    None
1737                }
1738            })
1739    }
1740
1741    pub fn diagnostics_update_count(&self) -> usize {
1742        self.diagnostics_update_count
1743    }
1744
1745    pub fn language(&self) -> Option<&Arc<Language>> {
1746        self.excerpts
1747            .iter()
1748            .next()
1749            .and_then(|excerpt| excerpt.buffer.language())
1750    }
1751
1752    pub fn is_dirty(&self) -> bool {
1753        self.is_dirty
1754    }
1755
1756    pub fn has_conflict(&self) -> bool {
1757        self.has_conflict
1758    }
1759
1760    pub fn diagnostic_group<'a, O>(
1761        &'a self,
1762        group_id: usize,
1763    ) -> impl Iterator<Item = DiagnosticEntry<O>> + 'a
1764    where
1765        O: text::FromAnchor + 'a,
1766    {
1767        self.as_singleton()
1768            .into_iter()
1769            .flat_map(move |excerpt| excerpt.buffer.diagnostic_group(group_id))
1770    }
1771
1772    pub fn diagnostics_in_range<'a, T, O>(
1773        &'a self,
1774        range: Range<T>,
1775    ) -> impl Iterator<Item = DiagnosticEntry<O>> + 'a
1776    where
1777        T: 'a + ToOffset,
1778        O: 'a + text::FromAnchor,
1779    {
1780        self.as_singleton().into_iter().flat_map(move |excerpt| {
1781            excerpt
1782                .buffer
1783                .diagnostics_in_range(range.start.to_offset(self)..range.end.to_offset(self))
1784        })
1785    }
1786
1787    pub fn range_for_syntax_ancestor<T: ToOffset>(&self, range: Range<T>) -> Option<Range<usize>> {
1788        let range = range.start.to_offset(self)..range.end.to_offset(self);
1789
1790        let mut cursor = self.excerpts.cursor::<usize>();
1791        cursor.seek(&range.start, Bias::Right, &());
1792        let start_excerpt = cursor.item();
1793
1794        cursor.seek(&range.end, Bias::Right, &());
1795        let end_excerpt = cursor.item();
1796
1797        start_excerpt
1798            .zip(end_excerpt)
1799            .and_then(|(start_excerpt, end_excerpt)| {
1800                if start_excerpt.id != end_excerpt.id {
1801                    return None;
1802                }
1803
1804                let excerpt_buffer_start =
1805                    start_excerpt.range.start.to_offset(&start_excerpt.buffer);
1806                let excerpt_buffer_end = excerpt_buffer_start + start_excerpt.text_summary.bytes;
1807
1808                let start_in_buffer =
1809                    excerpt_buffer_start + range.start.saturating_sub(*cursor.start());
1810                let end_in_buffer =
1811                    excerpt_buffer_start + range.end.saturating_sub(*cursor.start());
1812                let mut ancestor_buffer_range = start_excerpt
1813                    .buffer
1814                    .range_for_syntax_ancestor(start_in_buffer..end_in_buffer)?;
1815                ancestor_buffer_range.start =
1816                    cmp::max(ancestor_buffer_range.start, excerpt_buffer_start);
1817                ancestor_buffer_range.end = cmp::min(ancestor_buffer_range.end, excerpt_buffer_end);
1818
1819                let start = cursor.start() + (ancestor_buffer_range.start - excerpt_buffer_start);
1820                let end = cursor.start() + (ancestor_buffer_range.end - excerpt_buffer_start);
1821                Some(start..end)
1822            })
1823    }
1824
1825    pub fn outline(&self, theme: Option<&SyntaxTheme>) -> Option<Outline<Anchor>> {
1826        let excerpt = self.as_singleton()?;
1827        let outline = excerpt.buffer.outline(theme)?;
1828        Some(Outline::new(
1829            outline
1830                .items
1831                .into_iter()
1832                .map(|item| OutlineItem {
1833                    depth: item.depth,
1834                    range: self.anchor_in_excerpt(excerpt.id.clone(), item.range.start)
1835                        ..self.anchor_in_excerpt(excerpt.id.clone(), item.range.end),
1836                    text: item.text,
1837                    highlight_ranges: item.highlight_ranges,
1838                    name_ranges: item.name_ranges,
1839                })
1840                .collect(),
1841        ))
1842    }
1843
1844    fn buffer_snapshot_for_excerpt<'a>(
1845        &'a self,
1846        excerpt_id: &'a ExcerptId,
1847    ) -> Option<(usize, &'a BufferSnapshot)> {
1848        let mut cursor = self.excerpts.cursor::<Option<&ExcerptId>>();
1849        cursor.seek(&Some(excerpt_id), Bias::Left, &());
1850        if let Some(excerpt) = cursor.item() {
1851            if excerpt.id == *excerpt_id {
1852                return Some((excerpt.buffer_id, &excerpt.buffer));
1853            }
1854        }
1855        None
1856    }
1857
1858    pub fn remote_selections_in_range<'a>(
1859        &'a self,
1860        range: &'a Range<Anchor>,
1861    ) -> impl 'a + Iterator<Item = (ReplicaId, Selection<Anchor>)> {
1862        let mut cursor = self.excerpts.cursor::<Option<&ExcerptId>>();
1863        cursor.seek(&Some(&range.start.excerpt_id), Bias::Left, &());
1864        cursor
1865            .take_while(move |excerpt| excerpt.id <= range.end.excerpt_id)
1866            .flat_map(move |excerpt| {
1867                let mut query_range = excerpt.range.start.clone()..excerpt.range.end.clone();
1868                if excerpt.id == range.start.excerpt_id {
1869                    query_range.start = range.start.text_anchor.clone();
1870                }
1871                if excerpt.id == range.end.excerpt_id {
1872                    query_range.end = range.end.text_anchor.clone();
1873                }
1874
1875                excerpt
1876                    .buffer
1877                    .remote_selections_in_range(query_range)
1878                    .flat_map(move |(replica_id, selections)| {
1879                        selections.map(move |selection| {
1880                            let mut start = Anchor {
1881                                buffer_id: excerpt.buffer_id,
1882                                excerpt_id: excerpt.id.clone(),
1883                                text_anchor: selection.start.clone(),
1884                            };
1885                            let mut end = Anchor {
1886                                buffer_id: excerpt.buffer_id,
1887                                excerpt_id: excerpt.id.clone(),
1888                                text_anchor: selection.end.clone(),
1889                            };
1890                            if range.start.cmp(&start, self).unwrap().is_gt() {
1891                                start = range.start.clone();
1892                            }
1893                            if range.end.cmp(&end, self).unwrap().is_lt() {
1894                                end = range.end.clone();
1895                            }
1896
1897                            (
1898                                replica_id,
1899                                Selection {
1900                                    id: selection.id,
1901                                    start,
1902                                    end,
1903                                    reversed: selection.reversed,
1904                                    goal: selection.goal,
1905                                },
1906                            )
1907                        })
1908                    })
1909            })
1910    }
1911}
1912
1913impl History {
1914    fn start_transaction(&mut self, now: Instant) -> Option<TransactionId> {
1915        self.transaction_depth += 1;
1916        if self.transaction_depth == 1 {
1917            let id = post_inc(&mut self.next_transaction_id);
1918            self.undo_stack.push(Transaction {
1919                id,
1920                buffer_transactions: Default::default(),
1921                first_edit_at: now,
1922                last_edit_at: now,
1923            });
1924            Some(id)
1925        } else {
1926            None
1927        }
1928    }
1929
1930    fn end_transaction(
1931        &mut self,
1932        now: Instant,
1933        buffer_transactions: HashSet<(usize, TransactionId)>,
1934    ) -> bool {
1935        assert_ne!(self.transaction_depth, 0);
1936        self.transaction_depth -= 1;
1937        if self.transaction_depth == 0 {
1938            if buffer_transactions.is_empty() {
1939                self.undo_stack.pop();
1940                false
1941            } else {
1942                let transaction = self.undo_stack.last_mut().unwrap();
1943                transaction.last_edit_at = now;
1944                transaction.buffer_transactions.extend(buffer_transactions);
1945                true
1946            }
1947        } else {
1948            false
1949        }
1950    }
1951
1952    fn pop_undo(&mut self) -> Option<&Transaction> {
1953        assert_eq!(self.transaction_depth, 0);
1954        if let Some(transaction) = self.undo_stack.pop() {
1955            self.redo_stack.push(transaction);
1956            self.redo_stack.last()
1957        } else {
1958            None
1959        }
1960    }
1961
1962    fn pop_redo(&mut self) -> Option<&Transaction> {
1963        assert_eq!(self.transaction_depth, 0);
1964        if let Some(transaction) = self.redo_stack.pop() {
1965            self.undo_stack.push(transaction);
1966            self.undo_stack.last()
1967        } else {
1968            None
1969        }
1970    }
1971
1972    fn group(&mut self) -> Option<TransactionId> {
1973        let mut new_len = self.undo_stack.len();
1974        let mut transactions = self.undo_stack.iter_mut();
1975
1976        if let Some(mut transaction) = transactions.next_back() {
1977            while let Some(prev_transaction) = transactions.next_back() {
1978                if transaction.first_edit_at - prev_transaction.last_edit_at <= self.group_interval
1979                {
1980                    transaction = prev_transaction;
1981                    new_len -= 1;
1982                } else {
1983                    break;
1984                }
1985            }
1986        }
1987
1988        let (transactions_to_keep, transactions_to_merge) = self.undo_stack.split_at_mut(new_len);
1989        if let Some(last_transaction) = transactions_to_keep.last_mut() {
1990            if let Some(transaction) = transactions_to_merge.last() {
1991                last_transaction.last_edit_at = transaction.last_edit_at;
1992            }
1993        }
1994
1995        self.undo_stack.truncate(new_len);
1996        self.undo_stack.last().map(|t| t.id)
1997    }
1998}
1999
2000impl Excerpt {
2001    fn new(
2002        id: ExcerptId,
2003        buffer_id: usize,
2004        buffer: BufferSnapshot,
2005        range: Range<text::Anchor>,
2006        has_trailing_newline: bool,
2007    ) -> Self {
2008        Excerpt {
2009            id,
2010            max_buffer_row: range.end.to_point(&buffer).row,
2011            text_summary: buffer.text_summary_for_range::<TextSummary, _>(range.to_offset(&buffer)),
2012            buffer_id,
2013            buffer,
2014            range,
2015            has_trailing_newline,
2016        }
2017    }
2018
2019    fn chunks_in_range<'a>(
2020        &'a self,
2021        range: Range<usize>,
2022        theme: Option<&'a SyntaxTheme>,
2023    ) -> ExcerptChunks<'a> {
2024        let content_start = self.range.start.to_offset(&self.buffer);
2025        let chunks_start = content_start + range.start;
2026        let chunks_end = content_start + cmp::min(range.end, self.text_summary.bytes);
2027
2028        let footer_height = if self.has_trailing_newline
2029            && range.start <= self.text_summary.bytes
2030            && range.end > self.text_summary.bytes
2031        {
2032            1
2033        } else {
2034            0
2035        };
2036
2037        let content_chunks = self.buffer.chunks(chunks_start..chunks_end, theme);
2038
2039        ExcerptChunks {
2040            content_chunks,
2041            footer_height,
2042        }
2043    }
2044
2045    fn bytes_in_range(&self, range: Range<usize>) -> ExcerptBytes {
2046        let content_start = self.range.start.to_offset(&self.buffer);
2047        let bytes_start = content_start + range.start;
2048        let bytes_end = content_start + cmp::min(range.end, self.text_summary.bytes);
2049        let footer_height = if self.has_trailing_newline
2050            && range.start <= self.text_summary.bytes
2051            && range.end > self.text_summary.bytes
2052        {
2053            1
2054        } else {
2055            0
2056        };
2057        let content_bytes = self.buffer.bytes_in_range(bytes_start..bytes_end);
2058
2059        ExcerptBytes {
2060            content_bytes,
2061            footer_height,
2062        }
2063    }
2064
2065    fn clip_anchor(&self, text_anchor: text::Anchor) -> text::Anchor {
2066        if text_anchor
2067            .cmp(&self.range.start, &self.buffer)
2068            .unwrap()
2069            .is_lt()
2070        {
2071            self.range.start.clone()
2072        } else if text_anchor
2073            .cmp(&self.range.end, &self.buffer)
2074            .unwrap()
2075            .is_gt()
2076        {
2077            self.range.end.clone()
2078        } else {
2079            text_anchor
2080        }
2081    }
2082
2083    fn contains(&self, anchor: &Anchor) -> bool {
2084        self.buffer_id == anchor.buffer_id
2085            && self
2086                .range
2087                .start
2088                .cmp(&anchor.text_anchor, &self.buffer)
2089                .unwrap()
2090                .is_le()
2091            && self
2092                .range
2093                .end
2094                .cmp(&anchor.text_anchor, &self.buffer)
2095                .unwrap()
2096                .is_ge()
2097    }
2098}
2099
2100impl fmt::Debug for Excerpt {
2101    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2102        f.debug_struct("Excerpt")
2103            .field("id", &self.id)
2104            .field("buffer_id", &self.buffer_id)
2105            .field("range", &self.range)
2106            .field("text_summary", &self.text_summary)
2107            .field("has_trailing_newline", &self.has_trailing_newline)
2108            .finish()
2109    }
2110}
2111
2112impl sum_tree::Item for Excerpt {
2113    type Summary = ExcerptSummary;
2114
2115    fn summary(&self) -> Self::Summary {
2116        let mut text = self.text_summary.clone();
2117        if self.has_trailing_newline {
2118            text += TextSummary::from("\n");
2119        }
2120        ExcerptSummary {
2121            excerpt_id: self.id.clone(),
2122            max_buffer_row: self.max_buffer_row,
2123            text,
2124        }
2125    }
2126}
2127
2128impl sum_tree::Summary for ExcerptSummary {
2129    type Context = ();
2130
2131    fn add_summary(&mut self, summary: &Self, _: &()) {
2132        debug_assert!(summary.excerpt_id > self.excerpt_id);
2133        self.excerpt_id = summary.excerpt_id.clone();
2134        self.text.add_summary(&summary.text, &());
2135        self.max_buffer_row = cmp::max(self.max_buffer_row, summary.max_buffer_row);
2136    }
2137}
2138
2139impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for TextSummary {
2140    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
2141        *self += &summary.text;
2142    }
2143}
2144
2145impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for usize {
2146    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
2147        *self += summary.text.bytes;
2148    }
2149}
2150
2151impl<'a> sum_tree::SeekTarget<'a, ExcerptSummary, ExcerptSummary> for usize {
2152    fn cmp(&self, cursor_location: &ExcerptSummary, _: &()) -> cmp::Ordering {
2153        Ord::cmp(self, &cursor_location.text.bytes)
2154    }
2155}
2156
2157impl<'a> sum_tree::SeekTarget<'a, ExcerptSummary, ExcerptSummary> for Option<&'a ExcerptId> {
2158    fn cmp(&self, cursor_location: &ExcerptSummary, _: &()) -> cmp::Ordering {
2159        Ord::cmp(self, &Some(&cursor_location.excerpt_id))
2160    }
2161}
2162
2163impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for Point {
2164    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
2165        *self += summary.text.lines;
2166    }
2167}
2168
2169impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for PointUtf16 {
2170    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
2171        *self += summary.text.lines_utf16
2172    }
2173}
2174
2175impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for Option<&'a ExcerptId> {
2176    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
2177        *self = Some(&summary.excerpt_id);
2178    }
2179}
2180
2181impl<'a> MultiBufferRows<'a> {
2182    pub fn seek(&mut self, row: u32) {
2183        self.buffer_row_range = 0..0;
2184
2185        self.excerpts
2186            .seek_forward(&Point::new(row, 0), Bias::Right, &());
2187        if self.excerpts.item().is_none() {
2188            self.excerpts.prev(&());
2189
2190            if self.excerpts.item().is_none() && row == 0 {
2191                self.buffer_row_range = 0..1;
2192                return;
2193            }
2194        }
2195
2196        if let Some(excerpt) = self.excerpts.item() {
2197            let overshoot = row - self.excerpts.start().row;
2198            let excerpt_start = excerpt.range.start.to_point(&excerpt.buffer).row;
2199            self.buffer_row_range.start = excerpt_start + overshoot;
2200            self.buffer_row_range.end = excerpt_start + excerpt.text_summary.lines.row + 1;
2201        }
2202    }
2203}
2204
2205impl<'a> Iterator for MultiBufferRows<'a> {
2206    type Item = Option<u32>;
2207
2208    fn next(&mut self) -> Option<Self::Item> {
2209        loop {
2210            if !self.buffer_row_range.is_empty() {
2211                let row = Some(self.buffer_row_range.start);
2212                self.buffer_row_range.start += 1;
2213                return Some(row);
2214            }
2215            self.excerpts.item()?;
2216            self.excerpts.next(&());
2217            let excerpt = self.excerpts.item()?;
2218            self.buffer_row_range.start = excerpt.range.start.to_point(&excerpt.buffer).row;
2219            self.buffer_row_range.end =
2220                self.buffer_row_range.start + excerpt.text_summary.lines.row + 1;
2221        }
2222    }
2223}
2224
2225impl<'a> MultiBufferChunks<'a> {
2226    pub fn offset(&self) -> usize {
2227        self.range.start
2228    }
2229
2230    pub fn seek(&mut self, offset: usize) {
2231        self.range.start = offset;
2232        self.excerpts.seek(&offset, Bias::Right, &());
2233        if let Some(excerpt) = self.excerpts.item() {
2234            self.excerpt_chunks = Some(excerpt.chunks_in_range(
2235                self.range.start - self.excerpts.start()..self.range.end - self.excerpts.start(),
2236                self.theme,
2237            ));
2238        } else {
2239            self.excerpt_chunks = None;
2240        }
2241    }
2242}
2243
2244impl<'a> Iterator for MultiBufferChunks<'a> {
2245    type Item = Chunk<'a>;
2246
2247    fn next(&mut self) -> Option<Self::Item> {
2248        if self.range.is_empty() {
2249            None
2250        } else if let Some(chunk) = self.excerpt_chunks.as_mut()?.next() {
2251            self.range.start += chunk.text.len();
2252            Some(chunk)
2253        } else {
2254            self.excerpts.next(&());
2255            let excerpt = self.excerpts.item()?;
2256            self.excerpt_chunks = Some(
2257                excerpt.chunks_in_range(0..self.range.end - self.excerpts.start(), self.theme),
2258            );
2259            self.next()
2260        }
2261    }
2262}
2263
2264impl<'a> MultiBufferBytes<'a> {
2265    fn consume(&mut self, len: usize) {
2266        self.range.start += len;
2267        self.chunk = &self.chunk[len..];
2268
2269        if !self.range.is_empty() && self.chunk.is_empty() {
2270            if let Some(chunk) = self.excerpt_bytes.as_mut().and_then(|bytes| bytes.next()) {
2271                self.chunk = chunk;
2272            } else {
2273                self.excerpts.next(&());
2274                if let Some(excerpt) = self.excerpts.item() {
2275                    let mut excerpt_bytes =
2276                        excerpt.bytes_in_range(0..self.range.end - self.excerpts.start());
2277                    self.chunk = excerpt_bytes.next().unwrap();
2278                    self.excerpt_bytes = Some(excerpt_bytes);
2279                }
2280            }
2281        }
2282    }
2283}
2284
2285impl<'a> Iterator for MultiBufferBytes<'a> {
2286    type Item = &'a [u8];
2287
2288    fn next(&mut self) -> Option<Self::Item> {
2289        let chunk = self.chunk;
2290        if chunk.is_empty() {
2291            None
2292        } else {
2293            self.consume(chunk.len());
2294            Some(chunk)
2295        }
2296    }
2297}
2298
2299impl<'a> io::Read for MultiBufferBytes<'a> {
2300    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
2301        let len = cmp::min(buf.len(), self.chunk.len());
2302        buf[..len].copy_from_slice(&self.chunk[..len]);
2303        if len > 0 {
2304            self.consume(len);
2305        }
2306        Ok(len)
2307    }
2308}
2309
2310impl<'a> Iterator for ExcerptBytes<'a> {
2311    type Item = &'a [u8];
2312
2313    fn next(&mut self) -> Option<Self::Item> {
2314        if let Some(chunk) = self.content_bytes.next() {
2315            if !chunk.is_empty() {
2316                return Some(chunk);
2317            }
2318        }
2319
2320        if self.footer_height > 0 {
2321            let result = &NEWLINES[..self.footer_height];
2322            self.footer_height = 0;
2323            return Some(result);
2324        }
2325
2326        None
2327    }
2328}
2329
2330impl<'a> Iterator for ExcerptChunks<'a> {
2331    type Item = Chunk<'a>;
2332
2333    fn next(&mut self) -> Option<Self::Item> {
2334        if let Some(chunk) = self.content_chunks.next() {
2335            return Some(chunk);
2336        }
2337
2338        if self.footer_height > 0 {
2339            let text = unsafe { str::from_utf8_unchecked(&NEWLINES[..self.footer_height]) };
2340            self.footer_height = 0;
2341            return Some(Chunk {
2342                text,
2343                ..Default::default()
2344            });
2345        }
2346
2347        None
2348    }
2349}
2350
2351impl ToOffset for Point {
2352    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
2353        snapshot.point_to_offset(*self)
2354    }
2355}
2356
2357impl ToOffset for PointUtf16 {
2358    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
2359        snapshot.point_utf16_to_offset(*self)
2360    }
2361}
2362
2363impl ToOffset for usize {
2364    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
2365        assert!(*self <= snapshot.len(), "offset is out of range");
2366        *self
2367    }
2368}
2369
2370impl ToPoint for usize {
2371    fn to_point<'a>(&self, snapshot: &MultiBufferSnapshot) -> Point {
2372        snapshot.offset_to_point(*self)
2373    }
2374}
2375
2376impl ToPoint for Point {
2377    fn to_point<'a>(&self, _: &MultiBufferSnapshot) -> Point {
2378        *self
2379    }
2380}
2381
2382#[cfg(test)]
2383mod tests {
2384    use super::*;
2385    use gpui::MutableAppContext;
2386    use language::{Buffer, Rope};
2387    use rand::prelude::*;
2388    use std::env;
2389    use text::{Point, RandomCharIter};
2390    use util::test::sample_text;
2391
2392    #[gpui::test]
2393    fn test_singleton_multibuffer(cx: &mut MutableAppContext) {
2394        let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'a'), cx));
2395        let multibuffer = cx.add_model(|cx| MultiBuffer::singleton(buffer.clone(), cx));
2396
2397        let snapshot = multibuffer.read(cx).snapshot(cx);
2398        assert_eq!(snapshot.text(), buffer.read(cx).text());
2399
2400        assert_eq!(
2401            snapshot.buffer_rows(0).collect::<Vec<_>>(),
2402            (0..buffer.read(cx).row_count())
2403                .map(Some)
2404                .collect::<Vec<_>>()
2405        );
2406
2407        buffer.update(cx, |buffer, cx| buffer.edit([1..3], "XXX\n", cx));
2408        let snapshot = multibuffer.read(cx).snapshot(cx);
2409
2410        assert_eq!(snapshot.text(), buffer.read(cx).text());
2411        assert_eq!(
2412            snapshot.buffer_rows(0).collect::<Vec<_>>(),
2413            (0..buffer.read(cx).row_count())
2414                .map(Some)
2415                .collect::<Vec<_>>()
2416        );
2417    }
2418
2419    #[gpui::test]
2420    fn test_remote_multibuffer(cx: &mut MutableAppContext) {
2421        let host_buffer = cx.add_model(|cx| Buffer::new(0, "a", cx));
2422        let guest_buffer = cx.add_model(|cx| {
2423            let message = host_buffer.read(cx).to_proto();
2424            Buffer::from_proto(1, message, None, cx).unwrap()
2425        });
2426        let multibuffer = cx.add_model(|cx| MultiBuffer::singleton(guest_buffer.clone(), cx));
2427        let snapshot = multibuffer.read(cx).snapshot(cx);
2428        assert_eq!(snapshot.text(), "a");
2429
2430        guest_buffer.update(cx, |buffer, cx| buffer.edit([1..1], "b", cx));
2431        let snapshot = multibuffer.read(cx).snapshot(cx);
2432        assert_eq!(snapshot.text(), "ab");
2433
2434        guest_buffer.update(cx, |buffer, cx| buffer.edit([2..2], "c", cx));
2435        let snapshot = multibuffer.read(cx).snapshot(cx);
2436        assert_eq!(snapshot.text(), "abc");
2437    }
2438
2439    #[gpui::test]
2440    fn test_excerpt_buffer(cx: &mut MutableAppContext) {
2441        let buffer_1 = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'a'), cx));
2442        let buffer_2 = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'g'), cx));
2443        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
2444
2445        let subscription = multibuffer.update(cx, |multibuffer, cx| {
2446            let subscription = multibuffer.subscribe();
2447            multibuffer.push_excerpt(
2448                ExcerptProperties {
2449                    buffer: &buffer_1,
2450                    range: Point::new(1, 2)..Point::new(2, 5),
2451                },
2452                cx,
2453            );
2454            assert_eq!(
2455                subscription.consume().into_inner(),
2456                [Edit {
2457                    old: 0..0,
2458                    new: 0..10
2459                }]
2460            );
2461
2462            multibuffer.push_excerpt(
2463                ExcerptProperties {
2464                    buffer: &buffer_1,
2465                    range: Point::new(3, 3)..Point::new(4, 4),
2466                },
2467                cx,
2468            );
2469            multibuffer.push_excerpt(
2470                ExcerptProperties {
2471                    buffer: &buffer_2,
2472                    range: Point::new(3, 1)..Point::new(3, 3),
2473                },
2474                cx,
2475            );
2476            assert_eq!(
2477                subscription.consume().into_inner(),
2478                [Edit {
2479                    old: 10..10,
2480                    new: 10..22
2481                }]
2482            );
2483
2484            subscription
2485        });
2486
2487        let snapshot = multibuffer.read(cx).snapshot(cx);
2488        assert_eq!(
2489            snapshot.text(),
2490            concat!(
2491                "bbbb\n",  // Preserve newlines
2492                "ccccc\n", //
2493                "ddd\n",   //
2494                "eeee\n",  //
2495                "jj"       //
2496            )
2497        );
2498        assert_eq!(
2499            snapshot.buffer_rows(0).collect::<Vec<_>>(),
2500            [Some(1), Some(2), Some(3), Some(4), Some(3)]
2501        );
2502        assert_eq!(
2503            snapshot.buffer_rows(2).collect::<Vec<_>>(),
2504            [Some(3), Some(4), Some(3)]
2505        );
2506        assert_eq!(snapshot.buffer_rows(4).collect::<Vec<_>>(), [Some(3)]);
2507        assert_eq!(snapshot.buffer_rows(5).collect::<Vec<_>>(), []);
2508        assert!(!snapshot.range_contains_excerpt_boundary(Point::new(1, 0)..Point::new(1, 5)));
2509        assert!(snapshot.range_contains_excerpt_boundary(Point::new(1, 0)..Point::new(2, 0)));
2510        assert!(snapshot.range_contains_excerpt_boundary(Point::new(1, 0)..Point::new(4, 0)));
2511        assert!(!snapshot.range_contains_excerpt_boundary(Point::new(2, 0)..Point::new(3, 0)));
2512        assert!(!snapshot.range_contains_excerpt_boundary(Point::new(4, 0)..Point::new(4, 2)));
2513        assert!(!snapshot.range_contains_excerpt_boundary(Point::new(4, 2)..Point::new(4, 2)));
2514
2515        buffer_1.update(cx, |buffer, cx| {
2516            buffer.edit(
2517                [
2518                    Point::new(0, 0)..Point::new(0, 0),
2519                    Point::new(2, 1)..Point::new(2, 3),
2520                ],
2521                "\n",
2522                cx,
2523            );
2524        });
2525
2526        let snapshot = multibuffer.read(cx).snapshot(cx);
2527        assert_eq!(
2528            snapshot.text(),
2529            concat!(
2530                "bbbb\n", // Preserve newlines
2531                "c\n",    //
2532                "cc\n",   //
2533                "ddd\n",  //
2534                "eeee\n", //
2535                "jj"      //
2536            )
2537        );
2538
2539        assert_eq!(
2540            subscription.consume().into_inner(),
2541            [Edit {
2542                old: 6..8,
2543                new: 6..7
2544            }]
2545        );
2546
2547        let snapshot = multibuffer.read(cx).snapshot(cx);
2548        assert_eq!(
2549            snapshot.clip_point(Point::new(0, 5), Bias::Left),
2550            Point::new(0, 4)
2551        );
2552        assert_eq!(
2553            snapshot.clip_point(Point::new(0, 5), Bias::Right),
2554            Point::new(0, 4)
2555        );
2556        assert_eq!(
2557            snapshot.clip_point(Point::new(5, 1), Bias::Right),
2558            Point::new(5, 1)
2559        );
2560        assert_eq!(
2561            snapshot.clip_point(Point::new(5, 2), Bias::Right),
2562            Point::new(5, 2)
2563        );
2564        assert_eq!(
2565            snapshot.clip_point(Point::new(5, 3), Bias::Right),
2566            Point::new(5, 2)
2567        );
2568
2569        let snapshot = multibuffer.update(cx, |multibuffer, cx| {
2570            let buffer_2_excerpt_id = multibuffer.excerpt_ids_for_buffer(&buffer_2)[0].clone();
2571            multibuffer.remove_excerpts(&[buffer_2_excerpt_id], cx);
2572            multibuffer.snapshot(cx)
2573        });
2574
2575        assert_eq!(
2576            snapshot.text(),
2577            concat!(
2578                "bbbb\n", // Preserve newlines
2579                "c\n",    //
2580                "cc\n",   //
2581                "ddd\n",  //
2582                "eeee",   //
2583            )
2584        );
2585    }
2586
2587    #[gpui::test]
2588    fn test_empty_excerpt_buffer(cx: &mut MutableAppContext) {
2589        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
2590
2591        let snapshot = multibuffer.read(cx).snapshot(cx);
2592        assert_eq!(snapshot.text(), "");
2593        assert_eq!(snapshot.buffer_rows(0).collect::<Vec<_>>(), &[Some(0)]);
2594        assert_eq!(snapshot.buffer_rows(1).collect::<Vec<_>>(), &[]);
2595    }
2596
2597    #[gpui::test]
2598    fn test_singleton_multibuffer_anchors(cx: &mut MutableAppContext) {
2599        let buffer = cx.add_model(|cx| Buffer::new(0, "abcd", cx));
2600        let multibuffer = cx.add_model(|cx| MultiBuffer::singleton(buffer.clone(), cx));
2601        let old_snapshot = multibuffer.read(cx).snapshot(cx);
2602        buffer.update(cx, |buffer, cx| {
2603            buffer.edit([0..0], "X", cx);
2604            buffer.edit([5..5], "Y", cx);
2605        });
2606        let new_snapshot = multibuffer.read(cx).snapshot(cx);
2607
2608        assert_eq!(old_snapshot.text(), "abcd");
2609        assert_eq!(new_snapshot.text(), "XabcdY");
2610
2611        assert_eq!(old_snapshot.anchor_before(0).to_offset(&new_snapshot), 0);
2612        assert_eq!(old_snapshot.anchor_after(0).to_offset(&new_snapshot), 1);
2613        assert_eq!(old_snapshot.anchor_before(4).to_offset(&new_snapshot), 5);
2614        assert_eq!(old_snapshot.anchor_after(4).to_offset(&new_snapshot), 6);
2615    }
2616
2617    #[gpui::test]
2618    fn test_multibuffer_anchors(cx: &mut MutableAppContext) {
2619        let buffer_1 = cx.add_model(|cx| Buffer::new(0, "abcd", cx));
2620        let buffer_2 = cx.add_model(|cx| Buffer::new(0, "efghi", cx));
2621        let multibuffer = cx.add_model(|cx| {
2622            let mut multibuffer = MultiBuffer::new(0);
2623            multibuffer.push_excerpt(
2624                ExcerptProperties {
2625                    buffer: &buffer_1,
2626                    range: 0..4,
2627                },
2628                cx,
2629            );
2630            multibuffer.push_excerpt(
2631                ExcerptProperties {
2632                    buffer: &buffer_2,
2633                    range: 0..5,
2634                },
2635                cx,
2636            );
2637            multibuffer
2638        });
2639        let old_snapshot = multibuffer.read(cx).snapshot(cx);
2640
2641        assert_eq!(old_snapshot.anchor_before(0).to_offset(&old_snapshot), 0);
2642        assert_eq!(old_snapshot.anchor_after(0).to_offset(&old_snapshot), 0);
2643        assert_eq!(Anchor::min().to_offset(&old_snapshot), 0);
2644        assert_eq!(Anchor::min().to_offset(&old_snapshot), 0);
2645        assert_eq!(Anchor::max().to_offset(&old_snapshot), 10);
2646        assert_eq!(Anchor::max().to_offset(&old_snapshot), 10);
2647
2648        buffer_1.update(cx, |buffer, cx| {
2649            buffer.edit([0..0], "W", cx);
2650            buffer.edit([5..5], "X", cx);
2651        });
2652        buffer_2.update(cx, |buffer, cx| {
2653            buffer.edit([0..0], "Y", cx);
2654            buffer.edit([6..0], "Z", cx);
2655        });
2656        let new_snapshot = multibuffer.read(cx).snapshot(cx);
2657
2658        assert_eq!(old_snapshot.text(), "abcd\nefghi");
2659        assert_eq!(new_snapshot.text(), "WabcdX\nYefghiZ");
2660
2661        assert_eq!(old_snapshot.anchor_before(0).to_offset(&new_snapshot), 0);
2662        assert_eq!(old_snapshot.anchor_after(0).to_offset(&new_snapshot), 1);
2663        assert_eq!(old_snapshot.anchor_before(1).to_offset(&new_snapshot), 2);
2664        assert_eq!(old_snapshot.anchor_after(1).to_offset(&new_snapshot), 2);
2665        assert_eq!(old_snapshot.anchor_before(2).to_offset(&new_snapshot), 3);
2666        assert_eq!(old_snapshot.anchor_after(2).to_offset(&new_snapshot), 3);
2667        assert_eq!(old_snapshot.anchor_before(5).to_offset(&new_snapshot), 7);
2668        assert_eq!(old_snapshot.anchor_after(5).to_offset(&new_snapshot), 8);
2669        assert_eq!(old_snapshot.anchor_before(10).to_offset(&new_snapshot), 13);
2670        assert_eq!(old_snapshot.anchor_after(10).to_offset(&new_snapshot), 14);
2671    }
2672
2673    #[gpui::test]
2674    fn test_multibuffer_resolving_anchors_after_replacing_their_excerpts(
2675        cx: &mut MutableAppContext,
2676    ) {
2677        let buffer_1 = cx.add_model(|cx| Buffer::new(0, "abcd", cx));
2678        let buffer_2 = cx.add_model(|cx| Buffer::new(0, "ABCDEFGHIJKLMNOP", cx));
2679        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
2680
2681        // Create an insertion id in buffer 1 that doesn't exist in buffer 2.
2682        // Add an excerpt from buffer 1 that spans this new insertion.
2683        buffer_1.update(cx, |buffer, cx| buffer.edit([4..4], "123", cx));
2684        let excerpt_id_1 = multibuffer.update(cx, |multibuffer, cx| {
2685            multibuffer.push_excerpt(
2686                ExcerptProperties {
2687                    buffer: &buffer_1,
2688                    range: 0..7,
2689                },
2690                cx,
2691            )
2692        });
2693
2694        let snapshot_1 = multibuffer.read(cx).snapshot(cx);
2695        assert_eq!(snapshot_1.text(), "abcd123");
2696
2697        // Replace the buffer 1 excerpt with new excerpts from buffer 2.
2698        let (excerpt_id_2, excerpt_id_3, _) = multibuffer.update(cx, |multibuffer, cx| {
2699            multibuffer.remove_excerpts([&excerpt_id_1], cx);
2700            (
2701                multibuffer.push_excerpt(
2702                    ExcerptProperties {
2703                        buffer: &buffer_2,
2704                        range: 0..4,
2705                    },
2706                    cx,
2707                ),
2708                multibuffer.push_excerpt(
2709                    ExcerptProperties {
2710                        buffer: &buffer_2,
2711                        range: 6..10,
2712                    },
2713                    cx,
2714                ),
2715                multibuffer.push_excerpt(
2716                    ExcerptProperties {
2717                        buffer: &buffer_2,
2718                        range: 12..16,
2719                    },
2720                    cx,
2721                ),
2722            )
2723        });
2724        let snapshot_2 = multibuffer.read(cx).snapshot(cx);
2725        assert_eq!(snapshot_2.text(), "ABCD\nGHIJ\nMNOP");
2726
2727        // The old excerpt id has been reused.
2728        assert_eq!(excerpt_id_2, excerpt_id_1);
2729
2730        // Resolve some anchors from the previous snapshot in the new snapshot.
2731        // Although there is still an excerpt with the same id, it is for
2732        // a different buffer, so we don't attempt to resolve the old text
2733        // anchor in the new buffer.
2734        assert_eq!(
2735            snapshot_2.summary_for_anchor::<usize>(&snapshot_1.anchor_before(2)),
2736            0
2737        );
2738        assert_eq!(
2739            snapshot_2.summaries_for_anchors::<usize, _>(&[
2740                snapshot_1.anchor_before(2),
2741                snapshot_1.anchor_after(3)
2742            ]),
2743            vec![0, 0]
2744        );
2745        let refresh =
2746            snapshot_2.refresh_anchors(&[snapshot_1.anchor_before(2), snapshot_1.anchor_after(3)]);
2747        assert_eq!(
2748            refresh,
2749            &[
2750                (0, snapshot_2.anchor_before(0), false),
2751                (1, snapshot_2.anchor_after(0), false),
2752            ]
2753        );
2754
2755        // Replace the middle excerpt with a smaller excerpt in buffer 2,
2756        // that intersects the old excerpt.
2757        let excerpt_id_5 = multibuffer.update(cx, |multibuffer, cx| {
2758            multibuffer.remove_excerpts([&excerpt_id_3], cx);
2759            multibuffer.insert_excerpt_after(
2760                &excerpt_id_3,
2761                ExcerptProperties {
2762                    buffer: &buffer_2,
2763                    range: 5..8,
2764                },
2765                cx,
2766            )
2767        });
2768
2769        let snapshot_3 = multibuffer.read(cx).snapshot(cx);
2770        assert_eq!(snapshot_3.text(), "ABCD\nFGH\nMNOP");
2771        assert_ne!(excerpt_id_5, excerpt_id_3);
2772
2773        // Resolve some anchors from the previous snapshot in the new snapshot.
2774        // The anchor in the middle excerpt snaps to the beginning of the
2775        // excerpt, since it is not
2776        let anchors = [
2777            snapshot_2.anchor_before(0),
2778            snapshot_2.anchor_after(2),
2779            snapshot_2.anchor_after(6),
2780            snapshot_2.anchor_after(14),
2781        ];
2782        assert_eq!(
2783            snapshot_3.summaries_for_anchors::<usize, _>(&anchors),
2784            &[0, 2, 9, 13]
2785        );
2786
2787        let new_anchors = snapshot_3.refresh_anchors(&anchors);
2788        assert_eq!(
2789            new_anchors.iter().map(|a| (a.0, a.2)).collect::<Vec<_>>(),
2790            &[(0, true), (1, true), (2, true), (3, true)]
2791        );
2792        assert_eq!(
2793            snapshot_3.summaries_for_anchors::<usize, _>(new_anchors.iter().map(|a| &a.1)),
2794            &[0, 2, 7, 13]
2795        );
2796    }
2797
2798    #[gpui::test(iterations = 100)]
2799    fn test_random_multibuffer(cx: &mut MutableAppContext, mut rng: StdRng) {
2800        let operations = env::var("OPERATIONS")
2801            .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
2802            .unwrap_or(10);
2803
2804        let mut buffers: Vec<ModelHandle<Buffer>> = Vec::new();
2805        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
2806        let mut excerpt_ids = Vec::new();
2807        let mut expected_excerpts = Vec::<(ModelHandle<Buffer>, Range<text::Anchor>)>::new();
2808        let mut anchors = Vec::new();
2809        let mut old_versions = Vec::new();
2810
2811        for _ in 0..operations {
2812            match rng.gen_range(0..100) {
2813                0..=19 if !buffers.is_empty() => {
2814                    let buffer = buffers.choose(&mut rng).unwrap();
2815                    buffer.update(cx, |buf, cx| buf.randomly_edit(&mut rng, 5, cx));
2816                }
2817                20..=29 if !expected_excerpts.is_empty() => {
2818                    let mut ids_to_remove = vec![];
2819                    for _ in 0..rng.gen_range(1..=3) {
2820                        if expected_excerpts.is_empty() {
2821                            break;
2822                        }
2823
2824                        let ix = rng.gen_range(0..expected_excerpts.len());
2825                        ids_to_remove.push(excerpt_ids.remove(ix));
2826                        let (buffer, range) = expected_excerpts.remove(ix);
2827                        let buffer = buffer.read(cx);
2828                        log::info!(
2829                            "Removing excerpt {}: {:?}",
2830                            ix,
2831                            buffer
2832                                .text_for_range(range.to_offset(&buffer))
2833                                .collect::<String>(),
2834                        );
2835                    }
2836                    ids_to_remove.sort_unstable();
2837                    multibuffer.update(cx, |multibuffer, cx| {
2838                        multibuffer.remove_excerpts(&ids_to_remove, cx)
2839                    });
2840                }
2841                30..=39 if !expected_excerpts.is_empty() => {
2842                    let multibuffer = multibuffer.read(cx).read(cx);
2843                    let offset =
2844                        multibuffer.clip_offset(rng.gen_range(0..=multibuffer.len()), Bias::Left);
2845                    let bias = if rng.gen() { Bias::Left } else { Bias::Right };
2846                    log::info!("Creating anchor at {} with bias {:?}", offset, bias);
2847                    anchors.push(multibuffer.anchor_at(offset, bias));
2848                    anchors.sort_by(|a, b| a.cmp(&b, &multibuffer).unwrap());
2849                }
2850                40..=44 if !anchors.is_empty() => {
2851                    let multibuffer = multibuffer.read(cx).read(cx);
2852
2853                    anchors = multibuffer
2854                        .refresh_anchors(&anchors)
2855                        .into_iter()
2856                        .map(|a| a.1)
2857                        .collect();
2858
2859                    // Ensure the newly-refreshed anchors point to a valid excerpt and don't
2860                    // overshoot its boundaries.
2861                    let mut cursor = multibuffer.excerpts.cursor::<Option<&ExcerptId>>();
2862                    for anchor in &anchors {
2863                        if anchor.excerpt_id == ExcerptId::min()
2864                            || anchor.excerpt_id == ExcerptId::max()
2865                        {
2866                            continue;
2867                        }
2868
2869                        cursor.seek_forward(&Some(&anchor.excerpt_id), Bias::Left, &());
2870                        let excerpt = cursor.item().unwrap();
2871                        assert_eq!(excerpt.id, anchor.excerpt_id);
2872                        assert!(excerpt.contains(anchor));
2873                    }
2874                }
2875                _ => {
2876                    let buffer_handle = if buffers.is_empty() || rng.gen_bool(0.4) {
2877                        let base_text = RandomCharIter::new(&mut rng).take(10).collect::<String>();
2878                        buffers.push(cx.add_model(|cx| Buffer::new(0, base_text, cx)));
2879                        buffers.last().unwrap()
2880                    } else {
2881                        buffers.choose(&mut rng).unwrap()
2882                    };
2883
2884                    let buffer = buffer_handle.read(cx);
2885                    let end_ix = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Bias::Right);
2886                    let start_ix = buffer.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
2887                    let anchor_range = buffer.anchor_before(start_ix)..buffer.anchor_after(end_ix);
2888                    let prev_excerpt_ix = rng.gen_range(0..=expected_excerpts.len());
2889                    let prev_excerpt_id = excerpt_ids
2890                        .get(prev_excerpt_ix)
2891                        .cloned()
2892                        .unwrap_or(ExcerptId::max());
2893                    let excerpt_ix = (prev_excerpt_ix + 1).min(expected_excerpts.len());
2894
2895                    log::info!(
2896                        "Inserting excerpt at {} of {} for buffer {}: {:?}[{:?}] = {:?}",
2897                        excerpt_ix,
2898                        expected_excerpts.len(),
2899                        buffer_handle.id(),
2900                        buffer.text(),
2901                        start_ix..end_ix,
2902                        &buffer.text()[start_ix..end_ix]
2903                    );
2904
2905                    let excerpt_id = multibuffer.update(cx, |multibuffer, cx| {
2906                        multibuffer.insert_excerpt_after(
2907                            &prev_excerpt_id,
2908                            ExcerptProperties {
2909                                buffer: &buffer_handle,
2910                                range: start_ix..end_ix,
2911                            },
2912                            cx,
2913                        )
2914                    });
2915
2916                    excerpt_ids.insert(excerpt_ix, excerpt_id);
2917                    expected_excerpts.insert(excerpt_ix, (buffer_handle.clone(), anchor_range));
2918                }
2919            }
2920
2921            if rng.gen_bool(0.3) {
2922                multibuffer.update(cx, |multibuffer, cx| {
2923                    old_versions.push((multibuffer.snapshot(cx), multibuffer.subscribe()));
2924                })
2925            }
2926
2927            let snapshot = multibuffer.read(cx).snapshot(cx);
2928
2929            let mut excerpt_starts = Vec::new();
2930            let mut expected_text = String::new();
2931            let mut expected_buffer_rows = Vec::new();
2932            for (buffer, range) in &expected_excerpts {
2933                let buffer = buffer.read(cx);
2934                let buffer_range = range.to_offset(buffer);
2935
2936                excerpt_starts.push(TextSummary::from(expected_text.as_str()));
2937                expected_text.extend(buffer.text_for_range(buffer_range.clone()));
2938                expected_text.push('\n');
2939
2940                let buffer_row_range = buffer.offset_to_point(buffer_range.start).row
2941                    ..=buffer.offset_to_point(buffer_range.end).row;
2942                for row in buffer_row_range {
2943                    expected_buffer_rows.push(Some(row));
2944                }
2945            }
2946            // Remove final trailing newline.
2947            if !expected_excerpts.is_empty() {
2948                expected_text.pop();
2949            }
2950
2951            // Always report one buffer row
2952            if expected_buffer_rows.is_empty() {
2953                expected_buffer_rows.push(Some(0));
2954            }
2955
2956            assert_eq!(snapshot.text(), expected_text);
2957            log::info!("MultiBuffer text: {:?}", expected_text);
2958
2959            assert_eq!(
2960                snapshot.buffer_rows(0).collect::<Vec<_>>(),
2961                expected_buffer_rows,
2962            );
2963
2964            for _ in 0..5 {
2965                let start_row = rng.gen_range(0..=expected_buffer_rows.len());
2966                assert_eq!(
2967                    snapshot.buffer_rows(start_row as u32).collect::<Vec<_>>(),
2968                    &expected_buffer_rows[start_row..],
2969                    "buffer_rows({})",
2970                    start_row
2971                );
2972            }
2973
2974            assert_eq!(
2975                snapshot.max_buffer_row(),
2976                expected_buffer_rows
2977                    .into_iter()
2978                    .filter_map(|r| r)
2979                    .max()
2980                    .unwrap()
2981            );
2982
2983            let mut excerpt_starts = excerpt_starts.into_iter();
2984            for (buffer, range) in &expected_excerpts {
2985                let buffer_id = buffer.id();
2986                let buffer = buffer.read(cx);
2987                let buffer_range = range.to_offset(buffer);
2988                let buffer_start_point = buffer.offset_to_point(buffer_range.start);
2989                let buffer_start_point_utf16 =
2990                    buffer.text_summary_for_range::<PointUtf16, _>(0..buffer_range.start);
2991
2992                let excerpt_start = excerpt_starts.next().unwrap();
2993                let mut offset = excerpt_start.bytes;
2994                let mut buffer_offset = buffer_range.start;
2995                let mut point = excerpt_start.lines;
2996                let mut buffer_point = buffer_start_point;
2997                let mut point_utf16 = excerpt_start.lines_utf16;
2998                let mut buffer_point_utf16 = buffer_start_point_utf16;
2999                for ch in buffer
3000                    .snapshot()
3001                    .chunks(buffer_range.clone(), None)
3002                    .flat_map(|c| c.text.chars())
3003                {
3004                    for _ in 0..ch.len_utf8() {
3005                        let left_offset = snapshot.clip_offset(offset, Bias::Left);
3006                        let right_offset = snapshot.clip_offset(offset, Bias::Right);
3007                        let buffer_left_offset = buffer.clip_offset(buffer_offset, Bias::Left);
3008                        let buffer_right_offset = buffer.clip_offset(buffer_offset, Bias::Right);
3009                        assert_eq!(
3010                            left_offset,
3011                            excerpt_start.bytes + (buffer_left_offset - buffer_range.start),
3012                            "clip_offset({:?}, Left). buffer: {:?}, buffer offset: {:?}",
3013                            offset,
3014                            buffer_id,
3015                            buffer_offset,
3016                        );
3017                        assert_eq!(
3018                            right_offset,
3019                            excerpt_start.bytes + (buffer_right_offset - buffer_range.start),
3020                            "clip_offset({:?}, Right). buffer: {:?}, buffer offset: {:?}",
3021                            offset,
3022                            buffer_id,
3023                            buffer_offset,
3024                        );
3025
3026                        let left_point = snapshot.clip_point(point, Bias::Left);
3027                        let right_point = snapshot.clip_point(point, Bias::Right);
3028                        let buffer_left_point = buffer.clip_point(buffer_point, Bias::Left);
3029                        let buffer_right_point = buffer.clip_point(buffer_point, Bias::Right);
3030                        assert_eq!(
3031                            left_point,
3032                            excerpt_start.lines + (buffer_left_point - buffer_start_point),
3033                            "clip_point({:?}, Left). buffer: {:?}, buffer point: {:?}",
3034                            point,
3035                            buffer_id,
3036                            buffer_point,
3037                        );
3038                        assert_eq!(
3039                            right_point,
3040                            excerpt_start.lines + (buffer_right_point - buffer_start_point),
3041                            "clip_point({:?}, Right). buffer: {:?}, buffer point: {:?}",
3042                            point,
3043                            buffer_id,
3044                            buffer_point,
3045                        );
3046
3047                        assert_eq!(
3048                            snapshot.point_to_offset(left_point),
3049                            left_offset,
3050                            "point_to_offset({:?})",
3051                            left_point,
3052                        );
3053                        assert_eq!(
3054                            snapshot.offset_to_point(left_offset),
3055                            left_point,
3056                            "offset_to_point({:?})",
3057                            left_offset,
3058                        );
3059
3060                        offset += 1;
3061                        buffer_offset += 1;
3062                        if ch == '\n' {
3063                            point += Point::new(1, 0);
3064                            buffer_point += Point::new(1, 0);
3065                        } else {
3066                            point += Point::new(0, 1);
3067                            buffer_point += Point::new(0, 1);
3068                        }
3069                    }
3070
3071                    for _ in 0..ch.len_utf16() {
3072                        let left_point_utf16 = snapshot.clip_point_utf16(point_utf16, Bias::Left);
3073                        let right_point_utf16 = snapshot.clip_point_utf16(point_utf16, Bias::Right);
3074                        let buffer_left_point_utf16 =
3075                            buffer.clip_point_utf16(buffer_point_utf16, Bias::Left);
3076                        let buffer_right_point_utf16 =
3077                            buffer.clip_point_utf16(buffer_point_utf16, Bias::Right);
3078                        assert_eq!(
3079                            left_point_utf16,
3080                            excerpt_start.lines_utf16
3081                                + (buffer_left_point_utf16 - buffer_start_point_utf16),
3082                            "clip_point_utf16({:?}, Left). buffer: {:?}, buffer point_utf16: {:?}",
3083                            point_utf16,
3084                            buffer_id,
3085                            buffer_point_utf16,
3086                        );
3087                        assert_eq!(
3088                            right_point_utf16,
3089                            excerpt_start.lines_utf16
3090                                + (buffer_right_point_utf16 - buffer_start_point_utf16),
3091                            "clip_point_utf16({:?}, Right). buffer: {:?}, buffer point_utf16: {:?}",
3092                            point_utf16,
3093                            buffer_id,
3094                            buffer_point_utf16,
3095                        );
3096
3097                        if ch == '\n' {
3098                            point_utf16 += PointUtf16::new(1, 0);
3099                            buffer_point_utf16 += PointUtf16::new(1, 0);
3100                        } else {
3101                            point_utf16 += PointUtf16::new(0, 1);
3102                            buffer_point_utf16 += PointUtf16::new(0, 1);
3103                        }
3104                    }
3105                }
3106            }
3107
3108            for (row, line) in expected_text.split('\n').enumerate() {
3109                assert_eq!(
3110                    snapshot.line_len(row as u32),
3111                    line.len() as u32,
3112                    "line_len({}).",
3113                    row
3114                );
3115            }
3116
3117            let text_rope = Rope::from(expected_text.as_str());
3118            for _ in 0..10 {
3119                let end_ix = text_rope.clip_offset(rng.gen_range(0..=text_rope.len()), Bias::Right);
3120                let start_ix = text_rope.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
3121
3122                let text_for_range = snapshot
3123                    .text_for_range(start_ix..end_ix)
3124                    .collect::<String>();
3125                assert_eq!(
3126                    text_for_range,
3127                    &expected_text[start_ix..end_ix],
3128                    "incorrect text for range {:?}",
3129                    start_ix..end_ix
3130                );
3131
3132                let excerpted_buffer_ranges =
3133                    multibuffer.read(cx).excerpted_buffers(start_ix..end_ix, cx);
3134                let excerpted_buffers_text = excerpted_buffer_ranges
3135                    .into_iter()
3136                    .map(|(buffer, buffer_range)| {
3137                        buffer
3138                            .read(cx)
3139                            .text_for_range(buffer_range)
3140                            .collect::<String>()
3141                    })
3142                    .collect::<Vec<_>>()
3143                    .join("\n");
3144                assert_eq!(excerpted_buffers_text, text_for_range);
3145
3146                let expected_summary = TextSummary::from(&expected_text[start_ix..end_ix]);
3147                assert_eq!(
3148                    snapshot.text_summary_for_range::<TextSummary, _>(start_ix..end_ix),
3149                    expected_summary,
3150                    "incorrect summary for range {:?}",
3151                    start_ix..end_ix
3152                );
3153            }
3154
3155            // Anchor resolution
3156            for (anchor, resolved_offset) in anchors
3157                .iter()
3158                .zip(snapshot.summaries_for_anchors::<usize, _>(&anchors))
3159            {
3160                assert!(resolved_offset <= snapshot.len());
3161                assert_eq!(
3162                    snapshot.summary_for_anchor::<usize>(anchor),
3163                    resolved_offset
3164                );
3165            }
3166
3167            for _ in 0..10 {
3168                let end_ix = text_rope.clip_offset(rng.gen_range(0..=text_rope.len()), Bias::Right);
3169                assert_eq!(
3170                    snapshot.reversed_chars_at(end_ix).collect::<String>(),
3171                    expected_text[..end_ix].chars().rev().collect::<String>(),
3172                );
3173            }
3174
3175            for _ in 0..10 {
3176                let end_ix = rng.gen_range(0..=text_rope.len());
3177                let start_ix = rng.gen_range(0..=end_ix);
3178                assert_eq!(
3179                    snapshot
3180                        .bytes_in_range(start_ix..end_ix)
3181                        .flatten()
3182                        .copied()
3183                        .collect::<Vec<_>>(),
3184                    expected_text.as_bytes()[start_ix..end_ix].to_vec(),
3185                    "bytes_in_range({:?})",
3186                    start_ix..end_ix,
3187                );
3188            }
3189        }
3190
3191        let snapshot = multibuffer.read(cx).snapshot(cx);
3192        for (old_snapshot, subscription) in old_versions {
3193            let edits = subscription.consume().into_inner();
3194
3195            log::info!(
3196                "applying subscription edits to old text: {:?}: {:?}",
3197                old_snapshot.text(),
3198                edits,
3199            );
3200
3201            let mut text = old_snapshot.text();
3202            for edit in edits {
3203                let new_text: String = snapshot.text_for_range(edit.new.clone()).collect();
3204                text.replace_range(edit.new.start..edit.new.start + edit.old.len(), &new_text);
3205            }
3206            assert_eq!(text.to_string(), snapshot.text());
3207        }
3208    }
3209
3210    #[gpui::test]
3211    fn test_history(cx: &mut MutableAppContext) {
3212        let buffer_1 = cx.add_model(|cx| Buffer::new(0, "1234", cx));
3213        let buffer_2 = cx.add_model(|cx| Buffer::new(0, "5678", cx));
3214        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
3215        let group_interval = multibuffer.read(cx).history.group_interval;
3216        multibuffer.update(cx, |multibuffer, cx| {
3217            multibuffer.push_excerpt(
3218                ExcerptProperties {
3219                    buffer: &buffer_1,
3220                    range: 0..buffer_1.read(cx).len(),
3221                },
3222                cx,
3223            );
3224            multibuffer.push_excerpt(
3225                ExcerptProperties {
3226                    buffer: &buffer_2,
3227                    range: 0..buffer_2.read(cx).len(),
3228                },
3229                cx,
3230            );
3231        });
3232
3233        let mut now = Instant::now();
3234
3235        multibuffer.update(cx, |multibuffer, cx| {
3236            multibuffer.start_transaction_at(now, cx);
3237            multibuffer.edit(
3238                [
3239                    Point::new(0, 0)..Point::new(0, 0),
3240                    Point::new(1, 0)..Point::new(1, 0),
3241                ],
3242                "A",
3243                cx,
3244            );
3245            multibuffer.edit(
3246                [
3247                    Point::new(0, 1)..Point::new(0, 1),
3248                    Point::new(1, 1)..Point::new(1, 1),
3249                ],
3250                "B",
3251                cx,
3252            );
3253            multibuffer.end_transaction_at(now, cx);
3254            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
3255
3256            now += 2 * group_interval;
3257            multibuffer.start_transaction_at(now, cx);
3258            multibuffer.edit([2..2], "C", cx);
3259            multibuffer.end_transaction_at(now, cx);
3260            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678");
3261
3262            multibuffer.undo(cx);
3263            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
3264
3265            multibuffer.undo(cx);
3266            assert_eq!(multibuffer.read(cx).text(), "1234\n5678");
3267
3268            multibuffer.redo(cx);
3269            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
3270
3271            multibuffer.redo(cx);
3272            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678");
3273
3274            buffer_1.update(cx, |buffer_1, cx| buffer_1.undo(cx));
3275            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
3276
3277            multibuffer.undo(cx);
3278            assert_eq!(multibuffer.read(cx).text(), "1234\n5678");
3279
3280            multibuffer.redo(cx);
3281            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
3282
3283            multibuffer.redo(cx);
3284            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678");
3285
3286            multibuffer.undo(cx);
3287            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678");
3288
3289            buffer_1.update(cx, |buffer_1, cx| buffer_1.redo(cx));
3290            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678");
3291
3292            multibuffer.undo(cx);
3293            assert_eq!(multibuffer.read(cx).text(), "C1234\n5678");
3294        });
3295    }
3296}