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