1mod anchor;
   2
   3pub use anchor::{Anchor, AnchorRangeExt};
   4use anyhow::Result;
   5use clock::ReplicaId;
   6use collections::{HashMap, HashSet};
   7use gpui::{AppContext, Entity, ModelContext, ModelHandle, MutableAppContext, Task};
   8use language::{
   9    Buffer, BufferChunks, BufferSnapshot, Chunk, DiagnosticEntry, Event, File, Language, Selection,
  10    ToOffset as _, ToPoint as _, TransactionId,
  11};
  12use std::{
  13    cell::{Ref, RefCell},
  14    cmp, io,
  15    iter::{self, FromIterator, Peekable},
  16    ops::{Range, Sub},
  17    sync::Arc,
  18    time::{Duration, Instant, SystemTime},
  19};
  20use sum_tree::{Bias, Cursor, SumTree};
  21use text::{
  22    locator::Locator,
  23    rope::TextDimension,
  24    subscription::{Subscription, Topic},
  25    AnchorRangeExt as _, Edit, Point, PointUtf16, TextSummary,
  26};
  27use theme::SyntaxTheme;
  28use util::post_inc;
  29
  30const NEWLINES: &'static [u8] = &[b'\n'; u8::MAX as usize];
  31
  32pub type ExcerptId = Locator;
  33
  34pub struct MultiBuffer {
  35    snapshot: RefCell<MultiBufferSnapshot>,
  36    buffers: HashMap<usize, BufferState>,
  37    subscriptions: Topic,
  38    singleton: bool,
  39    replica_id: ReplicaId,
  40    history: History,
  41}
  42
  43struct History {
  44    next_transaction_id: usize,
  45    undo_stack: Vec<Transaction>,
  46    redo_stack: Vec<Transaction>,
  47    transaction_depth: usize,
  48    group_interval: Duration,
  49}
  50
  51struct Transaction {
  52    id: usize,
  53    buffer_transactions: HashSet<(usize, text::TransactionId)>,
  54    first_edit_at: Instant,
  55    last_edit_at: Instant,
  56}
  57
  58pub trait ToOffset: 'static {
  59    fn to_offset(&self, snapshot: &MultiBufferSnapshot) -> usize;
  60}
  61
  62pub trait ToPoint: 'static {
  63    fn to_point(&self, snapshot: &MultiBufferSnapshot) -> Point;
  64}
  65
  66pub trait FromAnchor: 'static {
  67    fn from_anchor(anchor: &Anchor, snapshot: &MultiBufferSnapshot) -> Self;
  68}
  69
  70#[derive(Debug)]
  71struct BufferState {
  72    buffer: ModelHandle<Buffer>,
  73    last_version: clock::Global,
  74    last_parse_count: usize,
  75    last_diagnostics_update_count: usize,
  76    excerpts: Vec<ExcerptId>,
  77}
  78
  79#[derive(Clone, Default)]
  80pub struct MultiBufferSnapshot {
  81    excerpts: SumTree<Excerpt>,
  82    parse_count: usize,
  83    diagnostics_update_count: usize,
  84}
  85
  86pub struct ExcerptProperties<'a, T> {
  87    pub buffer: &'a ModelHandle<Buffer>,
  88    pub range: Range<T>,
  89    pub header_height: u8,
  90}
  91
  92#[derive(Clone)]
  93struct Excerpt {
  94    id: ExcerptId,
  95    buffer_id: usize,
  96    buffer: BufferSnapshot,
  97    range: Range<text::Anchor>,
  98    text_summary: TextSummary,
  99    header_height: u8,
 100    has_trailing_newline: bool,
 101}
 102
 103#[derive(Clone, Debug, Default)]
 104struct ExcerptSummary {
 105    excerpt_id: ExcerptId,
 106    text: TextSummary,
 107}
 108
 109pub struct MultiBufferChunks<'a> {
 110    range: Range<usize>,
 111    cursor: Cursor<'a, Excerpt, usize>,
 112    header_height: u8,
 113    has_trailing_newline: bool,
 114    excerpt_chunks: Option<BufferChunks<'a>>,
 115    theme: Option<&'a SyntaxTheme>,
 116}
 117
 118pub struct MultiBufferBytes<'a> {
 119    chunks: Peekable<MultiBufferChunks<'a>>,
 120}
 121
 122impl MultiBuffer {
 123    pub fn new(replica_id: ReplicaId) -> Self {
 124        Self {
 125            snapshot: Default::default(),
 126            buffers: Default::default(),
 127            subscriptions: Default::default(),
 128            singleton: false,
 129            replica_id,
 130            history: History {
 131                next_transaction_id: Default::default(),
 132                undo_stack: Default::default(),
 133                redo_stack: Default::default(),
 134                transaction_depth: 0,
 135                group_interval: Duration::from_millis(300),
 136            },
 137        }
 138    }
 139
 140    pub fn singleton(buffer: ModelHandle<Buffer>, cx: &mut ModelContext<Self>) -> Self {
 141        let mut this = Self::new(buffer.read(cx).replica_id());
 142        this.singleton = true;
 143        this.push_excerpt(
 144            ExcerptProperties {
 145                buffer: &buffer,
 146                range: text::Anchor::min()..text::Anchor::max(),
 147                header_height: 0,
 148            },
 149            cx,
 150        );
 151        this
 152    }
 153
 154    pub fn build_simple(text: &str, cx: &mut MutableAppContext) -> ModelHandle<Self> {
 155        let buffer = cx.add_model(|cx| Buffer::new(0, text, cx));
 156        cx.add_model(|cx| Self::singleton(buffer, cx))
 157    }
 158
 159    pub fn replica_id(&self) -> ReplicaId {
 160        self.replica_id
 161    }
 162
 163    pub fn snapshot(&self, cx: &AppContext) -> MultiBufferSnapshot {
 164        self.sync(cx);
 165        self.snapshot.borrow().clone()
 166    }
 167
 168    pub fn read(&self, cx: &AppContext) -> Ref<MultiBufferSnapshot> {
 169        self.sync(cx);
 170        self.snapshot.borrow()
 171    }
 172
 173    pub fn as_singleton(&self) -> Option<&ModelHandle<Buffer>> {
 174        if self.buffers.len() == 1 {
 175            return Some(&self.buffers.values().next().unwrap().buffer);
 176        } else {
 177            None
 178        }
 179    }
 180
 181    pub fn subscribe(&mut self) -> Subscription {
 182        self.subscriptions.subscribe()
 183    }
 184
 185    pub fn edit<I, S, T>(&mut self, ranges: I, new_text: T, cx: &mut ModelContext<Self>)
 186    where
 187        I: IntoIterator<Item = Range<S>>,
 188        S: ToOffset,
 189        T: Into<String>,
 190    {
 191        self.edit_internal(ranges, new_text, false, cx)
 192    }
 193
 194    pub fn edit_with_autoindent<I, S, T>(
 195        &mut self,
 196        ranges: I,
 197        new_text: T,
 198        cx: &mut ModelContext<Self>,
 199    ) where
 200        I: IntoIterator<Item = Range<S>>,
 201        S: ToOffset,
 202        T: Into<String>,
 203    {
 204        self.edit_internal(ranges, new_text, true, cx)
 205    }
 206
 207    pub fn edit_internal<I, S, T>(
 208        &mut self,
 209        ranges_iter: I,
 210        new_text: T,
 211        autoindent: bool,
 212        cx: &mut ModelContext<Self>,
 213    ) where
 214        I: IntoIterator<Item = Range<S>>,
 215        S: ToOffset,
 216        T: Into<String>,
 217    {
 218        if let Some(buffer) = self.as_singleton() {
 219            let snapshot = self.read(cx);
 220            let ranges = ranges_iter
 221                .into_iter()
 222                .map(|range| range.start.to_offset(&snapshot)..range.end.to_offset(&snapshot));
 223            return buffer.update(cx, |buffer, cx| {
 224                if autoindent {
 225                    buffer.edit_with_autoindent(ranges, new_text, cx)
 226                } else {
 227                    buffer.edit(ranges, new_text, cx)
 228                }
 229            });
 230        }
 231
 232        let snapshot = self.read(cx);
 233        let mut buffer_edits: HashMap<usize, Vec<(Range<usize>, bool)>> = Default::default();
 234        let mut cursor = snapshot.excerpts.cursor::<usize>();
 235        for range in ranges_iter {
 236            let start = range.start.to_offset(&snapshot);
 237            let end = range.end.to_offset(&snapshot);
 238            cursor.seek(&start, Bias::Right, &());
 239            let start_excerpt = cursor.item().expect("start offset out of bounds");
 240            let start_overshoot =
 241                (start - cursor.start()).saturating_sub(start_excerpt.header_height as usize);
 242            let buffer_start =
 243                start_excerpt.range.start.to_offset(&start_excerpt.buffer) + start_overshoot;
 244
 245            cursor.seek(&end, Bias::Right, &());
 246            let end_excerpt = cursor.item().expect("end offset out of bounds");
 247            let end_overshoot =
 248                (end - cursor.start()).saturating_sub(end_excerpt.header_height as usize);
 249            let buffer_end = end_excerpt.range.start.to_offset(&end_excerpt.buffer) + end_overshoot;
 250
 251            if start_excerpt.id == end_excerpt.id {
 252                buffer_edits
 253                    .entry(start_excerpt.buffer_id)
 254                    .or_insert(Vec::new())
 255                    .push((buffer_start..buffer_end, true));
 256            } else {
 257                let start_excerpt_range =
 258                    buffer_start..start_excerpt.range.end.to_offset(&start_excerpt.buffer);
 259                let end_excerpt_range =
 260                    end_excerpt.range.start.to_offset(&end_excerpt.buffer)..buffer_end;
 261                buffer_edits
 262                    .entry(start_excerpt.buffer_id)
 263                    .or_insert(Vec::new())
 264                    .push((start_excerpt_range, true));
 265                buffer_edits
 266                    .entry(end_excerpt.buffer_id)
 267                    .or_insert(Vec::new())
 268                    .push((end_excerpt_range, false));
 269
 270                cursor.seek(&start, Bias::Right, &());
 271                cursor.next(&());
 272                while let Some(excerpt) = cursor.item() {
 273                    if excerpt.id == end_excerpt.id {
 274                        break;
 275                    }
 276
 277                    let excerpt_range = start_excerpt.range.end.to_offset(&start_excerpt.buffer)
 278                        ..start_excerpt.range.end.to_offset(&start_excerpt.buffer);
 279                    buffer_edits
 280                        .entry(excerpt.buffer_id)
 281                        .or_insert(Vec::new())
 282                        .push((excerpt_range, false));
 283                    cursor.next(&());
 284                }
 285            }
 286        }
 287
 288        let new_text = new_text.into();
 289        for (buffer_id, mut edits) in buffer_edits {
 290            edits.sort_unstable_by_key(|(range, _)| range.start);
 291            self.buffers[&buffer_id].buffer.update(cx, |buffer, cx| {
 292                let mut edits = edits.into_iter().peekable();
 293                let mut insertions = Vec::new();
 294                let mut deletions = Vec::new();
 295                while let Some((mut range, mut is_insertion)) = edits.next() {
 296                    while let Some((next_range, next_is_insertion)) = edits.peek() {
 297                        if range.end >= next_range.start {
 298                            range.end = cmp::max(next_range.end, range.end);
 299                            is_insertion |= *next_is_insertion;
 300                            edits.next();
 301                        } else {
 302                            break;
 303                        }
 304                    }
 305
 306                    if is_insertion {
 307                        insertions.push(
 308                            buffer.anchor_before(range.start)..buffer.anchor_before(range.end),
 309                        );
 310                    } else {
 311                        deletions.push(
 312                            buffer.anchor_before(range.start)..buffer.anchor_before(range.end),
 313                        );
 314                    }
 315                }
 316
 317                if autoindent {
 318                    buffer.edit_with_autoindent(deletions, "", cx);
 319                    buffer.edit_with_autoindent(insertions, new_text.clone(), cx);
 320                } else {
 321                    buffer.edit(deletions, "", cx);
 322                    buffer.edit(insertions, new_text.clone(), cx);
 323                }
 324            })
 325        }
 326    }
 327
 328    pub fn start_transaction(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 329        self.start_transaction_at(Instant::now(), cx)
 330    }
 331
 332    pub(crate) fn start_transaction_at(
 333        &mut self,
 334        now: Instant,
 335        cx: &mut ModelContext<Self>,
 336    ) -> Option<TransactionId> {
 337        if let Some(buffer) = self.as_singleton() {
 338            return buffer.update(cx, |buffer, _| buffer.start_transaction_at(now));
 339        }
 340
 341        for BufferState { buffer, .. } in self.buffers.values() {
 342            buffer.update(cx, |buffer, _| buffer.start_transaction_at(now));
 343        }
 344        self.history.start_transaction(now)
 345    }
 346
 347    pub fn end_transaction(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 348        self.end_transaction_at(Instant::now(), cx)
 349    }
 350
 351    pub(crate) fn end_transaction_at(
 352        &mut self,
 353        now: Instant,
 354        cx: &mut ModelContext<Self>,
 355    ) -> Option<TransactionId> {
 356        if let Some(buffer) = self.as_singleton() {
 357            return buffer.update(cx, |buffer, cx| buffer.end_transaction_at(now, cx));
 358        }
 359
 360        let mut buffer_transactions = HashSet::default();
 361        for BufferState { buffer, .. } in self.buffers.values() {
 362            if let Some(transaction_id) =
 363                buffer.update(cx, |buffer, cx| buffer.end_transaction_at(now, cx))
 364            {
 365                buffer_transactions.insert((buffer.id(), transaction_id));
 366            }
 367        }
 368
 369        if self.history.end_transaction(now, buffer_transactions) {
 370            let transaction_id = self.history.group().unwrap();
 371            Some(transaction_id)
 372        } else {
 373            None
 374        }
 375    }
 376
 377    pub fn set_active_selections(
 378        &mut self,
 379        selections: &[Selection<Anchor>],
 380        cx: &mut ModelContext<Self>,
 381    ) {
 382        let mut selections_by_buffer: HashMap<usize, Vec<Selection<text::Anchor>>> =
 383            Default::default();
 384        let snapshot = self.read(cx);
 385        let mut cursor = snapshot.excerpts.cursor::<Option<&ExcerptId>>();
 386        for selection in selections {
 387            cursor.seek(&Some(&selection.start.excerpt_id), Bias::Left, &());
 388            while let Some(excerpt) = cursor.item() {
 389                if excerpt.id > selection.end.excerpt_id {
 390                    break;
 391                }
 392
 393                let mut start = excerpt.range.start.clone();
 394                let mut end = excerpt.range.end.clone();
 395                if excerpt.id == selection.start.excerpt_id {
 396                    start = selection.start.text_anchor.clone();
 397                }
 398                if excerpt.id == selection.end.excerpt_id {
 399                    end = selection.end.text_anchor.clone();
 400                }
 401                selections_by_buffer
 402                    .entry(excerpt.buffer_id)
 403                    .or_default()
 404                    .push(Selection {
 405                        id: selection.id,
 406                        start,
 407                        end,
 408                        reversed: selection.reversed,
 409                        goal: selection.goal,
 410                    });
 411
 412                cursor.next(&());
 413            }
 414        }
 415
 416        for (buffer_id, mut selections) in selections_by_buffer {
 417            self.buffers[&buffer_id].buffer.update(cx, |buffer, cx| {
 418                selections.sort_unstable_by(|a, b| a.start.cmp(&b.start, buffer).unwrap());
 419                let mut selections = selections.into_iter().peekable();
 420                let merged_selections = Arc::from_iter(iter::from_fn(|| {
 421                    let mut selection = selections.next()?;
 422                    while let Some(next_selection) = selections.peek() {
 423                        if selection
 424                            .end
 425                            .cmp(&next_selection.start, buffer)
 426                            .unwrap()
 427                            .is_ge()
 428                        {
 429                            let next_selection = selections.next().unwrap();
 430                            if next_selection
 431                                .end
 432                                .cmp(&selection.end, buffer)
 433                                .unwrap()
 434                                .is_ge()
 435                            {
 436                                selection.end = next_selection.end;
 437                            }
 438                        } else {
 439                            break;
 440                        }
 441                    }
 442                    Some(selection)
 443                }));
 444                buffer.set_active_selections(merged_selections, cx);
 445            });
 446        }
 447    }
 448
 449    pub fn remove_active_selections(&mut self, cx: &mut ModelContext<Self>) {
 450        for buffer in self.buffers.values() {
 451            buffer
 452                .buffer
 453                .update(cx, |buffer, cx| buffer.remove_active_selections(cx));
 454        }
 455    }
 456
 457    pub fn undo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 458        if let Some(buffer) = self.as_singleton() {
 459            return buffer.update(cx, |buffer, cx| buffer.undo(cx));
 460        }
 461
 462        while let Some(transaction) = self.history.pop_undo() {
 463            let mut undone = false;
 464            for (buffer_id, buffer_transaction_id) in &transaction.buffer_transactions {
 465                if let Some(BufferState { buffer, .. }) = self.buffers.get(&buffer_id) {
 466                    undone |= buffer.update(cx, |buf, cx| {
 467                        buf.undo_transaction(*buffer_transaction_id, cx)
 468                    });
 469                }
 470            }
 471
 472            if undone {
 473                return Some(transaction.id);
 474            }
 475        }
 476
 477        None
 478    }
 479
 480    pub fn redo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
 481        if let Some(buffer) = self.as_singleton() {
 482            return buffer.update(cx, |buffer, cx| buffer.redo(cx));
 483        }
 484
 485        while let Some(transaction) = self.history.pop_redo() {
 486            let mut redone = false;
 487            for (buffer_id, buffer_transaction_id) in &transaction.buffer_transactions {
 488                if let Some(BufferState { buffer, .. }) = self.buffers.get(&buffer_id) {
 489                    redone |= buffer.update(cx, |buf, cx| {
 490                        buf.redo_transaction(*buffer_transaction_id, cx)
 491                    });
 492                }
 493            }
 494
 495            if redone {
 496                return Some(transaction.id);
 497            }
 498        }
 499
 500        None
 501    }
 502
 503    pub fn push_excerpt<O>(
 504        &mut self,
 505        props: ExcerptProperties<O>,
 506        cx: &mut ModelContext<Self>,
 507    ) -> ExcerptId
 508    where
 509        O: text::ToOffset,
 510    {
 511        assert_eq!(self.history.transaction_depth, 0);
 512        self.sync(cx);
 513
 514        let buffer = &props.buffer;
 515        cx.subscribe(buffer, Self::on_buffer_event).detach();
 516
 517        let buffer = props.buffer.read(cx);
 518        let range = buffer.anchor_before(&props.range.start)..buffer.anchor_after(&props.range.end);
 519        let mut snapshot = self.snapshot.borrow_mut();
 520        let prev_id = snapshot.excerpts.last().map(|e| &e.id);
 521        let id = ExcerptId::between(prev_id.unwrap_or(&ExcerptId::min()), &ExcerptId::max());
 522
 523        let edit_start = snapshot.excerpts.summary().text.bytes;
 524        let excerpt = Excerpt::new(
 525            id.clone(),
 526            props.buffer.id(),
 527            buffer.snapshot(),
 528            range,
 529            props.header_height,
 530            !self.singleton,
 531        );
 532        let edit = Edit {
 533            old: edit_start..edit_start,
 534            new: edit_start..edit_start + excerpt.text_summary.bytes,
 535        };
 536        snapshot.excerpts.push(excerpt, &());
 537        self.buffers
 538            .entry(props.buffer.id())
 539            .or_insert_with(|| BufferState {
 540                buffer: props.buffer.clone(),
 541                last_version: buffer.version(),
 542                last_parse_count: buffer.parse_count(),
 543                last_diagnostics_update_count: buffer.diagnostics_update_count(),
 544                excerpts: Default::default(),
 545            })
 546            .excerpts
 547            .push(id.clone());
 548
 549        self.subscriptions.publish_mut([edit]);
 550
 551        id
 552    }
 553
 554    fn on_buffer_event(
 555        &mut self,
 556        _: ModelHandle<Buffer>,
 557        event: &Event,
 558        cx: &mut ModelContext<Self>,
 559    ) {
 560        cx.emit(event.clone());
 561    }
 562
 563    pub fn save(
 564        &mut self,
 565        cx: &mut ModelContext<Self>,
 566    ) -> Result<Task<Result<(clock::Global, SystemTime)>>> {
 567        self.as_singleton()
 568            .unwrap()
 569            .update(cx, |buffer, cx| buffer.save(cx))
 570    }
 571
 572    pub fn language<'a>(&self, cx: &'a AppContext) -> Option<&'a Arc<Language>> {
 573        self.buffers
 574            .values()
 575            .next()
 576            .and_then(|state| state.buffer.read(cx).language())
 577    }
 578
 579    pub fn file<'a>(&self, cx: &'a AppContext) -> Option<&'a dyn File> {
 580        self.as_singleton().unwrap().read(cx).file()
 581    }
 582
 583    pub fn is_dirty(&self, cx: &AppContext) -> bool {
 584        self.as_singleton().unwrap().read(cx).is_dirty()
 585    }
 586
 587    pub fn has_conflict(&self, cx: &AppContext) -> bool {
 588        self.as_singleton().unwrap().read(cx).has_conflict()
 589    }
 590
 591    pub fn is_parsing(&self, cx: &AppContext) -> bool {
 592        self.as_singleton().unwrap().read(cx).is_parsing()
 593    }
 594
 595    fn sync(&self, cx: &AppContext) {
 596        let mut snapshot = self.snapshot.borrow_mut();
 597        let mut excerpts_to_edit = Vec::new();
 598        let mut reparsed = false;
 599        let mut diagnostics_updated = false;
 600        for buffer_state in self.buffers.values() {
 601            let buffer = buffer_state.buffer.read(cx);
 602            let buffer_edited = buffer.version().gt(&buffer_state.last_version);
 603            let buffer_reparsed = buffer.parse_count() > buffer_state.last_parse_count;
 604            let buffer_diagnostics_updated =
 605                buffer.diagnostics_update_count() > buffer_state.last_diagnostics_update_count;
 606            if buffer_edited || buffer_reparsed || buffer_diagnostics_updated {
 607                excerpts_to_edit.extend(
 608                    buffer_state
 609                        .excerpts
 610                        .iter()
 611                        .map(|excerpt_id| (excerpt_id, buffer_state, buffer_edited)),
 612                );
 613            }
 614
 615            reparsed |= buffer_reparsed;
 616            diagnostics_updated |= buffer_diagnostics_updated;
 617        }
 618        if reparsed {
 619            snapshot.parse_count += 1;
 620        }
 621        if diagnostics_updated {
 622            snapshot.diagnostics_update_count += 1;
 623        }
 624        excerpts_to_edit.sort_unstable_by_key(|(excerpt_id, _, _)| *excerpt_id);
 625
 626        let mut edits = Vec::new();
 627        let mut new_excerpts = SumTree::new();
 628        let mut cursor = snapshot.excerpts.cursor::<(Option<&ExcerptId>, usize)>();
 629
 630        for (id, buffer_state, buffer_edited) in excerpts_to_edit {
 631            new_excerpts.push_tree(cursor.slice(&Some(id), Bias::Left, &()), &());
 632            let old_excerpt = cursor.item().unwrap();
 633            let buffer = buffer_state.buffer.read(cx);
 634
 635            let mut new_excerpt;
 636            if buffer_edited {
 637                edits.extend(
 638                    buffer
 639                        .edits_since_in_range::<usize>(
 640                            old_excerpt.buffer.version(),
 641                            old_excerpt.range.clone(),
 642                        )
 643                        .map(|mut edit| {
 644                            let excerpt_old_start =
 645                                cursor.start().1 + old_excerpt.header_height as usize;
 646                            let excerpt_new_start = new_excerpts.summary().text.bytes
 647                                + old_excerpt.header_height as usize;
 648                            edit.old.start += excerpt_old_start;
 649                            edit.old.end += excerpt_old_start;
 650                            edit.new.start += excerpt_new_start;
 651                            edit.new.end += excerpt_new_start;
 652                            edit
 653                        }),
 654                );
 655
 656                new_excerpt = Excerpt::new(
 657                    id.clone(),
 658                    buffer_state.buffer.id(),
 659                    buffer.snapshot(),
 660                    old_excerpt.range.clone(),
 661                    old_excerpt.header_height,
 662                    !self.singleton,
 663                );
 664            } else {
 665                new_excerpt = old_excerpt.clone();
 666                new_excerpt.buffer = buffer.snapshot();
 667            }
 668
 669            new_excerpts.push(new_excerpt, &());
 670            cursor.next(&());
 671        }
 672        new_excerpts.push_tree(cursor.suffix(&()), &());
 673
 674        drop(cursor);
 675        snapshot.excerpts = new_excerpts;
 676
 677        self.subscriptions.publish(edits);
 678    }
 679}
 680
 681#[cfg(any(test, feature = "test-support"))]
 682impl MultiBuffer {
 683    pub fn randomly_edit<R: rand::Rng>(
 684        &mut self,
 685        rng: &mut R,
 686        count: usize,
 687        cx: &mut ModelContext<Self>,
 688    ) {
 689        self.as_singleton()
 690            .unwrap()
 691            .update(cx, |buffer, cx| buffer.randomly_edit(rng, count, cx));
 692        self.sync(cx);
 693    }
 694}
 695
 696impl Entity for MultiBuffer {
 697    type Event = language::Event;
 698}
 699
 700impl MultiBufferSnapshot {
 701    pub fn text(&self) -> String {
 702        self.chunks(0..self.len(), None)
 703            .map(|chunk| chunk.text)
 704            .collect()
 705    }
 706
 707    pub fn reversed_chars_at<'a, T: ToOffset>(
 708        &'a self,
 709        position: T,
 710    ) -> impl Iterator<Item = char> + 'a {
 711        // TODO
 712        let offset = position.to_offset(self);
 713        self.as_singleton().unwrap().reversed_chars_at(offset)
 714    }
 715
 716    pub fn chars_at<'a, T: ToOffset>(&'a self, position: T) -> impl Iterator<Item = char> + 'a {
 717        let offset = position.to_offset(self);
 718        self.text_for_range(offset..self.len())
 719            .flat_map(|chunk| chunk.chars())
 720    }
 721
 722    pub fn text_for_range<'a, T: ToOffset>(
 723        &'a self,
 724        range: Range<T>,
 725    ) -> impl Iterator<Item = &'a str> {
 726        self.chunks(range, None).map(|chunk| chunk.text)
 727    }
 728
 729    pub fn is_line_blank(&self, row: u32) -> bool {
 730        self.text_for_range(Point::new(row, 0)..Point::new(row, self.line_len(row)))
 731            .all(|chunk| chunk.matches(|c: char| !c.is_whitespace()).next().is_none())
 732    }
 733
 734    pub fn contains_str_at<T>(&self, position: T, needle: &str) -> bool
 735    where
 736        T: ToOffset,
 737    {
 738        let position = position.to_offset(self);
 739        position == self.clip_offset(position, Bias::Left)
 740            && self
 741                .bytes_in_range(position..self.len())
 742                .flatten()
 743                .copied()
 744                .take(needle.len())
 745                .eq(needle.bytes())
 746    }
 747
 748    fn as_singleton(&self) -> Option<&BufferSnapshot> {
 749        let mut excerpts = self.excerpts.iter();
 750        let buffer = excerpts.next().map(|excerpt| &excerpt.buffer);
 751        if excerpts.next().is_none() {
 752            buffer
 753        } else {
 754            None
 755        }
 756    }
 757
 758    pub fn len(&self) -> usize {
 759        self.excerpts.summary().text.bytes
 760    }
 761
 762    pub fn clip_offset(&self, offset: usize, bias: Bias) -> usize {
 763        let mut cursor = self.excerpts.cursor::<usize>();
 764        cursor.seek(&offset, Bias::Right, &());
 765        if let Some(excerpt) = cursor.item() {
 766            let start_after_header = *cursor.start() + excerpt.header_height as usize;
 767            if offset < start_after_header {
 768                *cursor.start()
 769            } else {
 770                let excerpt_start = excerpt.range.start.to_offset(&excerpt.buffer);
 771                let buffer_offset = excerpt
 772                    .buffer
 773                    .clip_offset(excerpt_start + (offset - start_after_header), bias);
 774                let offset_in_excerpt = if buffer_offset > excerpt_start {
 775                    buffer_offset - excerpt_start
 776                } else {
 777                    0
 778                };
 779                start_after_header + offset_in_excerpt
 780            }
 781        } else {
 782            self.excerpts.summary().text.bytes
 783        }
 784    }
 785
 786    pub fn clip_point(&self, point: Point, bias: Bias) -> Point {
 787        let mut cursor = self.excerpts.cursor::<Point>();
 788        cursor.seek(&point, Bias::Right, &());
 789        if let Some(excerpt) = cursor.item() {
 790            let start_after_header = *cursor.start() + Point::new(excerpt.header_height as u32, 0);
 791            if point < start_after_header {
 792                *cursor.start()
 793            } else {
 794                let excerpt_start = excerpt.range.start.to_point(&excerpt.buffer);
 795                let buffer_point = excerpt
 796                    .buffer
 797                    .clip_point(excerpt_start + (point - start_after_header), bias);
 798                let point_in_excerpt = if buffer_point > excerpt_start {
 799                    buffer_point - excerpt_start
 800                } else {
 801                    Point::zero()
 802                };
 803                start_after_header + point_in_excerpt
 804            }
 805        } else {
 806            self.excerpts.summary().text.lines
 807        }
 808    }
 809
 810    pub fn clip_point_utf16(&self, point: PointUtf16, bias: Bias) -> PointUtf16 {
 811        let mut cursor = self.excerpts.cursor::<PointUtf16>();
 812        cursor.seek(&point, Bias::Right, &());
 813        if let Some(excerpt) = cursor.item() {
 814            let start_after_header =
 815                *cursor.start() + PointUtf16::new(excerpt.header_height as u32, 0);
 816            if point < start_after_header {
 817                *cursor.start()
 818            } else {
 819                let excerpt_start = excerpt
 820                    .buffer
 821                    .offset_to_point_utf16(excerpt.range.start.to_offset(&excerpt.buffer));
 822                let buffer_point = excerpt
 823                    .buffer
 824                    .clip_point_utf16(excerpt_start + (point - start_after_header), bias);
 825                let point_in_excerpt = if buffer_point > excerpt_start {
 826                    buffer_point - excerpt_start
 827                } else {
 828                    PointUtf16::new(0, 0)
 829                };
 830                start_after_header + point_in_excerpt
 831            }
 832        } else {
 833            self.excerpts.summary().text.lines_utf16
 834        }
 835    }
 836
 837    pub fn bytes_in_range<'a, T: ToOffset>(&'a self, range: Range<T>) -> MultiBufferBytes<'a> {
 838        MultiBufferBytes {
 839            chunks: self.chunks(range, None).peekable(),
 840        }
 841    }
 842
 843    pub fn chunks<'a, T: ToOffset>(
 844        &'a self,
 845        range: Range<T>,
 846        theme: Option<&'a SyntaxTheme>,
 847    ) -> MultiBufferChunks<'a> {
 848        let mut result = MultiBufferChunks {
 849            range: 0..range.end.to_offset(self),
 850            cursor: self.excerpts.cursor::<usize>(),
 851            header_height: 0,
 852            excerpt_chunks: None,
 853            has_trailing_newline: false,
 854            theme,
 855        };
 856        result.seek(range.start.to_offset(self));
 857        result
 858    }
 859
 860    pub fn offset_to_point(&self, offset: usize) -> Point {
 861        let mut cursor = self.excerpts.cursor::<(usize, Point)>();
 862        cursor.seek(&offset, Bias::Right, &());
 863        if let Some(excerpt) = cursor.item() {
 864            let (start_offset, start_point) = cursor.start();
 865            let overshoot = offset - start_offset;
 866            let header_height = excerpt.header_height as usize;
 867            if overshoot < header_height {
 868                *start_point
 869            } else {
 870                let excerpt_start_offset = excerpt.range.start.to_offset(&excerpt.buffer);
 871                let excerpt_start_point = excerpt.range.start.to_point(&excerpt.buffer);
 872                let buffer_point = excerpt
 873                    .buffer
 874                    .offset_to_point(excerpt_start_offset + (overshoot - header_height));
 875                *start_point
 876                    + Point::new(header_height as u32, 0)
 877                    + (buffer_point - excerpt_start_point)
 878            }
 879        } else {
 880            self.excerpts.summary().text.lines
 881        }
 882    }
 883
 884    pub fn point_to_offset(&self, point: Point) -> usize {
 885        let mut cursor = self.excerpts.cursor::<(Point, usize)>();
 886        cursor.seek(&point, Bias::Right, &());
 887        if let Some(excerpt) = cursor.item() {
 888            let (start_point, start_offset) = cursor.start();
 889            let overshoot = point - start_point;
 890            let header_height = Point::new(excerpt.header_height as u32, 0);
 891            if overshoot < header_height {
 892                *start_offset
 893            } else {
 894                let excerpt_start_offset = excerpt.range.start.to_offset(&excerpt.buffer);
 895                let excerpt_start_point = excerpt.range.start.to_point(&excerpt.buffer);
 896                let buffer_offset = excerpt
 897                    .buffer
 898                    .point_to_offset(excerpt_start_point + (overshoot - header_height));
 899                *start_offset + excerpt.header_height as usize + buffer_offset
 900                    - excerpt_start_offset
 901            }
 902        } else {
 903            self.excerpts.summary().text.bytes
 904        }
 905    }
 906
 907    pub fn point_utf16_to_offset(&self, point: PointUtf16) -> usize {
 908        let mut cursor = self.excerpts.cursor::<(PointUtf16, usize)>();
 909        cursor.seek(&point, Bias::Right, &());
 910        if let Some(excerpt) = cursor.item() {
 911            let (start_point, start_offset) = cursor.start();
 912            let overshoot = point - start_point;
 913            let header_height = PointUtf16::new(excerpt.header_height as u32, 0);
 914            if overshoot < header_height {
 915                *start_offset
 916            } else {
 917                let excerpt_start_offset = excerpt.range.start.to_offset(&excerpt.buffer);
 918                let excerpt_start_point = excerpt
 919                    .buffer
 920                    .offset_to_point_utf16(excerpt.range.start.to_offset(&excerpt.buffer));
 921                let buffer_offset = excerpt
 922                    .buffer
 923                    .point_utf16_to_offset(excerpt_start_point + (overshoot - header_height));
 924                *start_offset
 925                    + excerpt.header_height as usize
 926                    + (buffer_offset - excerpt_start_offset)
 927            }
 928        } else {
 929            self.excerpts.summary().text.bytes
 930        }
 931    }
 932
 933    pub fn indent_column_for_line(&self, row: u32) -> u32 {
 934        if let Some((buffer, range)) = self.buffer_line_for_row(row) {
 935            buffer
 936                .indent_column_for_line(range.start.row)
 937                .min(range.end.column)
 938                .saturating_sub(range.start.column)
 939        } else {
 940            0
 941        }
 942    }
 943
 944    pub fn line_len(&self, row: u32) -> u32 {
 945        if let Some((_, range)) = self.buffer_line_for_row(row) {
 946            range.end.column - range.start.column
 947        } else {
 948            0
 949        }
 950    }
 951
 952    fn buffer_line_for_row(&self, row: u32) -> Option<(&BufferSnapshot, Range<Point>)> {
 953        let mut cursor = self.excerpts.cursor::<Point>();
 954        cursor.seek(&Point::new(row, 0), Bias::Right, &());
 955        if let Some(excerpt) = cursor.item() {
 956            let overshoot = row - cursor.start().row;
 957            let header_height = excerpt.header_height as u32;
 958            if overshoot >= header_height {
 959                let excerpt_start = excerpt.range.start.to_point(&excerpt.buffer);
 960                let excerpt_end = excerpt.range.end.to_point(&excerpt.buffer);
 961                let buffer_row = excerpt_start.row + overshoot - header_height;
 962                let line_start = Point::new(buffer_row, 0);
 963                let line_end = Point::new(buffer_row, excerpt.buffer.line_len(buffer_row));
 964                return Some((
 965                    &excerpt.buffer,
 966                    line_start.max(excerpt_start)..line_end.min(excerpt_end),
 967                ));
 968            }
 969        }
 970        None
 971    }
 972
 973    pub fn max_point(&self) -> Point {
 974        self.text_summary().lines
 975    }
 976
 977    pub fn text_summary(&self) -> TextSummary {
 978        self.excerpts.summary().text
 979    }
 980
 981    pub fn text_summary_for_range<'a, D, O>(&'a self, range: Range<O>) -> D
 982    where
 983        D: TextDimension,
 984        O: ToOffset,
 985    {
 986        let mut summary = D::default();
 987        let mut range = range.start.to_offset(self)..range.end.to_offset(self);
 988        let mut cursor = self.excerpts.cursor::<usize>();
 989        cursor.seek(&range.start, Bias::Right, &());
 990        if let Some(excerpt) = cursor.item() {
 991            let start_after_header = cursor.start() + excerpt.header_height as usize;
 992            if range.start < start_after_header {
 993                let header_len = cmp::min(range.end, start_after_header) - range.start;
 994                summary.add_assign(&D::from_text_summary(&TextSummary {
 995                    bytes: header_len,
 996                    lines: Point::new(header_len as u32, 0),
 997                    lines_utf16: PointUtf16::new(header_len as u32, 0),
 998                    first_line_chars: 0,
 999                    last_line_chars: 0,
1000                    longest_row: 0,
1001                    longest_row_chars: 0,
1002                }));
1003                range.start = start_after_header;
1004                range.end = cmp::max(range.start, range.end);
1005            }
1006
1007            let mut end_before_newline = cursor.end(&());
1008            if excerpt.has_trailing_newline {
1009                end_before_newline -= 1;
1010            }
1011
1012            let excerpt_start = excerpt.range.start.to_offset(&excerpt.buffer);
1013            let start_in_excerpt = excerpt_start + (range.start - start_after_header);
1014            let end_in_excerpt =
1015                excerpt_start + (cmp::min(end_before_newline, range.end) - start_after_header);
1016            summary.add_assign(
1017                &excerpt
1018                    .buffer
1019                    .text_summary_for_range(start_in_excerpt..end_in_excerpt),
1020            );
1021
1022            if range.end > end_before_newline {
1023                summary.add_assign(&D::from_text_summary(&TextSummary {
1024                    bytes: 1,
1025                    lines: Point::new(1 as u32, 0),
1026                    lines_utf16: PointUtf16::new(1 as u32, 0),
1027                    first_line_chars: 0,
1028                    last_line_chars: 0,
1029                    longest_row: 0,
1030                    longest_row_chars: 0,
1031                }));
1032            }
1033
1034            cursor.next(&());
1035        }
1036
1037        if range.end > *cursor.start() {
1038            summary.add_assign(&D::from_text_summary(&cursor.summary::<_, TextSummary>(
1039                &range.end,
1040                Bias::Right,
1041                &(),
1042            )));
1043            if let Some(excerpt) = cursor.item() {
1044                let start_after_header = cursor.start() + excerpt.header_height as usize;
1045                let header_len =
1046                    cmp::min(range.end - cursor.start(), excerpt.header_height as usize);
1047                summary.add_assign(&D::from_text_summary(&TextSummary {
1048                    bytes: header_len,
1049                    lines: Point::new(header_len as u32, 0),
1050                    lines_utf16: PointUtf16::new(header_len as u32, 0),
1051                    first_line_chars: 0,
1052                    last_line_chars: 0,
1053                    longest_row: 0,
1054                    longest_row_chars: 0,
1055                }));
1056                range.end = cmp::max(start_after_header, range.end);
1057
1058                let excerpt_start = excerpt.range.start.to_offset(&excerpt.buffer);
1059                let end_in_excerpt = excerpt_start + (range.end - start_after_header);
1060                summary.add_assign(
1061                    &excerpt
1062                        .buffer
1063                        .text_summary_for_range(excerpt_start..end_in_excerpt),
1064                );
1065                cursor.next(&());
1066            }
1067        }
1068
1069        summary
1070    }
1071
1072    pub fn summary_for_anchor<D>(&self, anchor: &Anchor) -> D
1073    where
1074        D: TextDimension + Ord + Sub<D, Output = D>,
1075    {
1076        let mut cursor = self.excerpts.cursor::<ExcerptSummary>();
1077        cursor.seek(&Some(&anchor.excerpt_id), Bias::Left, &());
1078        if let Some(excerpt) = cursor.item() {
1079            if excerpt.id == anchor.excerpt_id {
1080                let mut excerpt_start = D::from_text_summary(&cursor.start().text);
1081                excerpt_start.add_summary(&excerpt.header_summary(), &());
1082                let excerpt_buffer_start = excerpt.range.start.summary::<D>(&excerpt.buffer);
1083                let buffer_point = anchor.text_anchor.summary::<D>(&excerpt.buffer);
1084                if buffer_point > excerpt_buffer_start {
1085                    excerpt_start.add_assign(&(buffer_point - excerpt_buffer_start));
1086                }
1087                return excerpt_start;
1088            }
1089        }
1090        D::from_text_summary(&cursor.start().text)
1091    }
1092
1093    pub fn summaries_for_anchors<'a, D, I>(&'a self, anchors: I) -> Vec<D>
1094    where
1095        D: TextDimension + Ord + Sub<D, Output = D>,
1096        I: 'a + IntoIterator<Item = &'a Anchor>,
1097    {
1098        let mut anchors = anchors.into_iter().peekable();
1099        let mut cursor = self.excerpts.cursor::<ExcerptSummary>();
1100        let mut summaries = Vec::new();
1101        while let Some(anchor) = anchors.peek() {
1102            let excerpt_id = &anchor.excerpt_id;
1103            let excerpt_anchors = iter::from_fn(|| {
1104                let anchor = anchors.peek()?;
1105                if anchor.excerpt_id == *excerpt_id {
1106                    Some(&anchors.next().unwrap().text_anchor)
1107                } else {
1108                    None
1109                }
1110            });
1111
1112            cursor.seek_forward(&Some(excerpt_id), Bias::Left, &());
1113            if let Some(excerpt) = cursor.item() {
1114                if excerpt.id == *excerpt_id {
1115                    let mut excerpt_start = D::from_text_summary(&cursor.start().text);
1116                    excerpt_start.add_summary(&excerpt.header_summary(), &());
1117                    let excerpt_buffer_start = excerpt.range.start.summary::<D>(&excerpt.buffer);
1118                    summaries.extend(
1119                        excerpt
1120                            .buffer
1121                            .summaries_for_anchors::<D, _>(excerpt_anchors)
1122                            .map(move |summary| {
1123                                let mut excerpt_start = excerpt_start.clone();
1124                                let excerpt_buffer_start = excerpt_buffer_start.clone();
1125                                if summary > excerpt_buffer_start {
1126                                    excerpt_start.add_assign(&(summary - excerpt_buffer_start));
1127                                }
1128                                excerpt_start
1129                            }),
1130                    );
1131                    continue;
1132                }
1133            }
1134
1135            let summary = D::from_text_summary(&cursor.start().text);
1136            summaries.extend(excerpt_anchors.map(|_| summary.clone()));
1137        }
1138
1139        summaries
1140    }
1141
1142    pub fn anchor_before<T: ToOffset>(&self, position: T) -> Anchor {
1143        self.anchor_at(position, Bias::Left)
1144    }
1145
1146    pub fn anchor_after<T: ToOffset>(&self, position: T) -> Anchor {
1147        self.anchor_at(position, Bias::Right)
1148    }
1149
1150    pub fn anchor_at<T: ToOffset>(&self, position: T, bias: Bias) -> Anchor {
1151        let offset = position.to_offset(self);
1152        let mut cursor = self.excerpts.cursor::<(usize, Option<&ExcerptId>)>();
1153        cursor.seek(&offset, bias, &());
1154        if let Some(excerpt) = cursor.item() {
1155            let start_after_header = cursor.start().0 + excerpt.header_height as usize;
1156            let mut end_before_newline = cursor.end(&()).0;
1157            if excerpt.has_trailing_newline {
1158                end_before_newline -= 1;
1159            }
1160
1161            let buffer_start = excerpt.range.start.to_offset(&excerpt.buffer);
1162            let overshoot = cmp::min(offset, end_before_newline).saturating_sub(start_after_header);
1163            Anchor {
1164                excerpt_id: excerpt.id.clone(),
1165                text_anchor: excerpt.buffer.anchor_at(buffer_start + overshoot, bias),
1166            }
1167        } else if offset == 0 && bias == Bias::Left {
1168            Anchor::min()
1169        } else {
1170            Anchor::max()
1171        }
1172    }
1173
1174    pub fn parse_count(&self) -> usize {
1175        self.parse_count
1176    }
1177
1178    pub fn enclosing_bracket_ranges<T: ToOffset>(
1179        &self,
1180        range: Range<T>,
1181    ) -> Option<(Range<usize>, Range<usize>)> {
1182        let range = range.start.to_offset(self)..range.end.to_offset(self);
1183        self.as_singleton().unwrap().enclosing_bracket_ranges(range)
1184    }
1185
1186    pub fn diagnostics_update_count(&self) -> usize {
1187        self.diagnostics_update_count
1188    }
1189
1190    pub fn language(&self) -> Option<&Arc<Language>> {
1191        self.excerpts
1192            .iter()
1193            .next()
1194            .and_then(|excerpt| excerpt.buffer.language())
1195    }
1196
1197    pub fn diagnostic_group<'a, O>(
1198        &'a self,
1199        group_id: usize,
1200    ) -> impl Iterator<Item = DiagnosticEntry<O>> + 'a
1201    where
1202        O: text::FromAnchor + 'a,
1203    {
1204        self.as_singleton().unwrap().diagnostic_group(group_id)
1205    }
1206
1207    pub fn diagnostics_in_range<'a, T, O>(
1208        &'a self,
1209        range: Range<T>,
1210    ) -> impl Iterator<Item = DiagnosticEntry<O>> + 'a
1211    where
1212        T: 'a + ToOffset,
1213        O: 'a + text::FromAnchor,
1214    {
1215        let range = range.start.to_offset(self)..range.end.to_offset(self);
1216        self.as_singleton().unwrap().diagnostics_in_range(range)
1217    }
1218
1219    pub fn range_for_syntax_ancestor<T: ToOffset>(&self, range: Range<T>) -> Option<Range<usize>> {
1220        let range = range.start.to_offset(self)..range.end.to_offset(self);
1221        self.as_singleton()
1222            .unwrap()
1223            .range_for_syntax_ancestor(range)
1224    }
1225
1226    fn buffer_snapshot_for_excerpt<'a>(
1227        &'a self,
1228        excerpt_id: &'a ExcerptId,
1229    ) -> Option<&'a BufferSnapshot> {
1230        let mut cursor = self.excerpts.cursor::<Option<&ExcerptId>>();
1231        cursor.seek(&Some(excerpt_id), Bias::Left, &());
1232        if let Some(excerpt) = cursor.item() {
1233            if excerpt.id == *excerpt_id {
1234                return Some(&excerpt.buffer);
1235            }
1236        }
1237        None
1238    }
1239
1240    pub fn remote_selections_in_range<'a>(
1241        &'a self,
1242        range: &'a Range<Anchor>,
1243    ) -> impl 'a + Iterator<Item = (ReplicaId, Selection<Anchor>)> {
1244        let mut cursor = self.excerpts.cursor::<Option<&ExcerptId>>();
1245        cursor.seek(&Some(&range.start.excerpt_id), Bias::Left, &());
1246        cursor
1247            .take_while(move |excerpt| excerpt.id <= range.end.excerpt_id)
1248            .flat_map(move |excerpt| {
1249                let mut query_range = excerpt.range.start.clone()..excerpt.range.end.clone();
1250                if excerpt.id == range.start.excerpt_id {
1251                    query_range.start = range.start.text_anchor.clone();
1252                }
1253                if excerpt.id == range.end.excerpt_id {
1254                    query_range.end = range.end.text_anchor.clone();
1255                }
1256
1257                excerpt
1258                    .buffer
1259                    .remote_selections_in_range(query_range)
1260                    .flat_map(move |(replica_id, selections)| {
1261                        selections.map(move |selection| {
1262                            let mut start = Anchor {
1263                                excerpt_id: excerpt.id.clone(),
1264                                text_anchor: selection.start.clone(),
1265                            };
1266                            let mut end = Anchor {
1267                                excerpt_id: excerpt.id.clone(),
1268                                text_anchor: selection.end.clone(),
1269                            };
1270                            if range.start.cmp(&start, self).unwrap().is_gt() {
1271                                start = range.start.clone();
1272                            }
1273                            if range.end.cmp(&end, self).unwrap().is_lt() {
1274                                end = range.end.clone();
1275                            }
1276
1277                            (
1278                                replica_id,
1279                                Selection {
1280                                    id: selection.id,
1281                                    start,
1282                                    end,
1283                                    reversed: selection.reversed,
1284                                    goal: selection.goal,
1285                                },
1286                            )
1287                        })
1288                    })
1289            })
1290    }
1291}
1292
1293impl History {
1294    fn start_transaction(&mut self, now: Instant) -> Option<TransactionId> {
1295        self.transaction_depth += 1;
1296        if self.transaction_depth == 1 {
1297            let id = post_inc(&mut self.next_transaction_id);
1298            self.undo_stack.push(Transaction {
1299                id,
1300                buffer_transactions: Default::default(),
1301                first_edit_at: now,
1302                last_edit_at: now,
1303            });
1304            Some(id)
1305        } else {
1306            None
1307        }
1308    }
1309
1310    fn end_transaction(
1311        &mut self,
1312        now: Instant,
1313        buffer_transactions: HashSet<(usize, TransactionId)>,
1314    ) -> bool {
1315        assert_ne!(self.transaction_depth, 0);
1316        self.transaction_depth -= 1;
1317        if self.transaction_depth == 0 {
1318            if buffer_transactions.is_empty() {
1319                self.undo_stack.pop();
1320                false
1321            } else {
1322                let transaction = self.undo_stack.last_mut().unwrap();
1323                transaction.last_edit_at = now;
1324                transaction.buffer_transactions.extend(buffer_transactions);
1325                true
1326            }
1327        } else {
1328            false
1329        }
1330    }
1331
1332    fn pop_undo(&mut self) -> Option<&Transaction> {
1333        assert_eq!(self.transaction_depth, 0);
1334        if let Some(transaction) = self.undo_stack.pop() {
1335            self.redo_stack.push(transaction);
1336            self.redo_stack.last()
1337        } else {
1338            None
1339        }
1340    }
1341
1342    fn pop_redo(&mut self) -> Option<&Transaction> {
1343        assert_eq!(self.transaction_depth, 0);
1344        if let Some(transaction) = self.redo_stack.pop() {
1345            self.undo_stack.push(transaction);
1346            self.undo_stack.last()
1347        } else {
1348            None
1349        }
1350    }
1351
1352    fn group(&mut self) -> Option<TransactionId> {
1353        let mut new_len = self.undo_stack.len();
1354        let mut transactions = self.undo_stack.iter_mut();
1355
1356        if let Some(mut transaction) = transactions.next_back() {
1357            while let Some(prev_transaction) = transactions.next_back() {
1358                if transaction.first_edit_at - prev_transaction.last_edit_at <= self.group_interval
1359                {
1360                    transaction = prev_transaction;
1361                    new_len -= 1;
1362                } else {
1363                    break;
1364                }
1365            }
1366        }
1367
1368        let (transactions_to_keep, transactions_to_merge) = self.undo_stack.split_at_mut(new_len);
1369        if let Some(last_transaction) = transactions_to_keep.last_mut() {
1370            if let Some(transaction) = transactions_to_merge.last() {
1371                last_transaction.last_edit_at = transaction.last_edit_at;
1372            }
1373        }
1374
1375        self.undo_stack.truncate(new_len);
1376        self.undo_stack.last().map(|t| t.id)
1377    }
1378}
1379
1380impl Excerpt {
1381    fn new(
1382        id: ExcerptId,
1383        buffer_id: usize,
1384        buffer: BufferSnapshot,
1385        range: Range<text::Anchor>,
1386        header_height: u8,
1387        has_trailing_newline: bool,
1388    ) -> Self {
1389        let mut text_summary =
1390            buffer.text_summary_for_range::<TextSummary, _>(range.to_offset(&buffer));
1391        if header_height > 0 {
1392            text_summary.first_line_chars = 0;
1393            text_summary.lines.row += header_height as u32;
1394            text_summary.lines_utf16.row += header_height as u32;
1395            text_summary.bytes += header_height as usize;
1396            text_summary.longest_row += header_height as u32;
1397        }
1398        if has_trailing_newline {
1399            text_summary.last_line_chars = 0;
1400            text_summary.lines.row += 1;
1401            text_summary.lines.column = 0;
1402            text_summary.lines_utf16.row += 1;
1403            text_summary.lines_utf16.column = 0;
1404            text_summary.bytes += 1;
1405        }
1406
1407        Excerpt {
1408            id,
1409            buffer_id,
1410            buffer,
1411            range,
1412            text_summary,
1413            header_height,
1414            has_trailing_newline,
1415        }
1416    }
1417
1418    fn header_summary(&self) -> TextSummary {
1419        TextSummary {
1420            bytes: self.header_height as usize,
1421            lines: Point::new(self.header_height as u32, 0),
1422            lines_utf16: PointUtf16::new(self.header_height as u32, 0),
1423            first_line_chars: 0,
1424            last_line_chars: 0,
1425            longest_row: 0,
1426            longest_row_chars: 0,
1427        }
1428    }
1429}
1430
1431impl sum_tree::Item for Excerpt {
1432    type Summary = ExcerptSummary;
1433
1434    fn summary(&self) -> Self::Summary {
1435        ExcerptSummary {
1436            excerpt_id: self.id.clone(),
1437            text: self.text_summary.clone(),
1438        }
1439    }
1440}
1441
1442impl sum_tree::Summary for ExcerptSummary {
1443    type Context = ();
1444
1445    fn add_summary(&mut self, summary: &Self, _: &()) {
1446        debug_assert!(summary.excerpt_id > self.excerpt_id);
1447        self.excerpt_id = summary.excerpt_id.clone();
1448        self.text.add_summary(&summary.text, &());
1449    }
1450}
1451
1452impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for TextSummary {
1453    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
1454        *self += &summary.text;
1455    }
1456}
1457
1458impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for usize {
1459    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
1460        *self += summary.text.bytes;
1461    }
1462}
1463
1464impl<'a> sum_tree::SeekTarget<'a, ExcerptSummary, ExcerptSummary> for usize {
1465    fn cmp(&self, cursor_location: &ExcerptSummary, _: &()) -> cmp::Ordering {
1466        Ord::cmp(self, &cursor_location.text.bytes)
1467    }
1468}
1469
1470impl<'a> sum_tree::SeekTarget<'a, ExcerptSummary, ExcerptSummary> for Option<&'a ExcerptId> {
1471    fn cmp(&self, cursor_location: &ExcerptSummary, _: &()) -> cmp::Ordering {
1472        Ord::cmp(self, &Some(&cursor_location.excerpt_id))
1473    }
1474}
1475
1476impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for Point {
1477    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
1478        *self += summary.text.lines;
1479    }
1480}
1481
1482impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for PointUtf16 {
1483    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
1484        *self += summary.text.lines_utf16
1485    }
1486}
1487
1488impl<'a> sum_tree::Dimension<'a, ExcerptSummary> for Option<&'a ExcerptId> {
1489    fn add_summary(&mut self, summary: &'a ExcerptSummary, _: &()) {
1490        *self = Some(&summary.excerpt_id);
1491    }
1492}
1493
1494impl<'a> MultiBufferChunks<'a> {
1495    pub fn offset(&self) -> usize {
1496        self.range.start
1497    }
1498
1499    pub fn seek(&mut self, offset: usize) {
1500        self.range.start = offset;
1501        self.cursor.seek_forward(&offset, Bias::Right, &());
1502        self.header_height = 0;
1503        self.excerpt_chunks = None;
1504        if let Some(excerpt) = self.cursor.item() {
1505            let buffer_range = excerpt.range.to_offset(&excerpt.buffer);
1506            self.header_height = excerpt.header_height;
1507            self.has_trailing_newline = excerpt.has_trailing_newline;
1508
1509            let buffer_start;
1510            let start_overshoot = self.range.start - self.cursor.start();
1511            if start_overshoot < excerpt.header_height as usize {
1512                self.header_height -= start_overshoot as u8;
1513                buffer_start = buffer_range.start;
1514            } else {
1515                buffer_start =
1516                    buffer_range.start + start_overshoot - excerpt.header_height as usize;
1517                self.header_height = 0;
1518            }
1519
1520            let buffer_end;
1521            let end_overshoot = self.range.end - self.cursor.start();
1522            if end_overshoot < excerpt.header_height as usize {
1523                self.header_height -= excerpt.header_height - end_overshoot as u8;
1524                buffer_end = buffer_start;
1525            } else {
1526                buffer_end = cmp::min(
1527                    buffer_range.end,
1528                    buffer_range.start + end_overshoot - excerpt.header_height as usize,
1529                );
1530            }
1531
1532            self.excerpt_chunks = Some(excerpt.buffer.chunks(buffer_start..buffer_end, self.theme));
1533        }
1534    }
1535}
1536
1537impl<'a> Iterator for MultiBufferChunks<'a> {
1538    type Item = Chunk<'a>;
1539
1540    fn next(&mut self) -> Option<Self::Item> {
1541        loop {
1542            if self.header_height > 0 {
1543                let chunk = Chunk {
1544                    text: unsafe {
1545                        std::str::from_utf8_unchecked(&NEWLINES[..self.header_height as usize])
1546                    },
1547                    ..Default::default()
1548                };
1549                self.range.start += self.header_height as usize;
1550                self.header_height = 0;
1551                return Some(chunk);
1552            }
1553
1554            if let Some(excerpt_chunks) = self.excerpt_chunks.as_mut() {
1555                if let Some(chunk) = excerpt_chunks.next() {
1556                    self.range.start += chunk.text.len();
1557                    return Some(chunk);
1558                }
1559                self.excerpt_chunks.take();
1560                if self.has_trailing_newline && self.cursor.end(&()) <= self.range.end {
1561                    self.range.start += 1;
1562                    return Some(Chunk {
1563                        text: "\n",
1564                        ..Default::default()
1565                    });
1566                }
1567            }
1568
1569            self.cursor.next(&());
1570            if *self.cursor.start() >= self.range.end {
1571                return None;
1572            }
1573
1574            let excerpt = self.cursor.item()?;
1575            let buffer_range = excerpt.range.to_offset(&excerpt.buffer);
1576
1577            let buffer_end = cmp::min(
1578                buffer_range.end,
1579                buffer_range.start + self.range.end
1580                    - excerpt.header_height as usize
1581                    - self.cursor.start(),
1582            );
1583
1584            self.header_height = excerpt.header_height;
1585            self.has_trailing_newline = excerpt.has_trailing_newline;
1586            self.excerpt_chunks = Some(
1587                excerpt
1588                    .buffer
1589                    .chunks(buffer_range.start..buffer_end, self.theme),
1590            );
1591        }
1592    }
1593}
1594
1595impl<'a> Iterator for MultiBufferBytes<'a> {
1596    type Item = &'a [u8];
1597
1598    fn next(&mut self) -> Option<Self::Item> {
1599        self.chunks.next().map(|chunk| chunk.text.as_bytes())
1600    }
1601}
1602
1603impl<'a> io::Read for MultiBufferBytes<'a> {
1604    fn read(&mut self, _: &mut [u8]) -> io::Result<usize> {
1605        todo!()
1606    }
1607}
1608
1609impl ToOffset for Point {
1610    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
1611        snapshot.point_to_offset(*self)
1612    }
1613}
1614
1615impl ToOffset for PointUtf16 {
1616    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
1617        snapshot.point_utf16_to_offset(*self)
1618    }
1619}
1620
1621impl ToOffset for usize {
1622    fn to_offset<'a>(&self, snapshot: &MultiBufferSnapshot) -> usize {
1623        assert!(*self <= snapshot.len(), "offset is out of range");
1624        *self
1625    }
1626}
1627
1628impl ToPoint for usize {
1629    fn to_point<'a>(&self, snapshot: &MultiBufferSnapshot) -> Point {
1630        snapshot.offset_to_point(*self)
1631    }
1632}
1633
1634impl ToPoint for Point {
1635    fn to_point<'a>(&self, _: &MultiBufferSnapshot) -> Point {
1636        *self
1637    }
1638}
1639
1640#[cfg(test)]
1641mod tests {
1642    use super::*;
1643    use gpui::MutableAppContext;
1644    use language::Buffer;
1645    use rand::prelude::*;
1646    use std::env;
1647    use text::{Point, RandomCharIter};
1648    use util::test::sample_text;
1649
1650    #[gpui::test]
1651    fn test_singleton_multibuffer(cx: &mut MutableAppContext) {
1652        let buffer = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'a'), cx));
1653        let multibuffer = cx.add_model(|cx| MultiBuffer::singleton(buffer.clone(), cx));
1654        assert_eq!(
1655            multibuffer.read(cx).snapshot(cx).text(),
1656            buffer.read(cx).text()
1657        );
1658
1659        buffer.update(cx, |buffer, cx| buffer.edit([1..3], "XXX", cx));
1660        assert_eq!(
1661            multibuffer.read(cx).snapshot(cx).text(),
1662            buffer.read(cx).text()
1663        );
1664    }
1665
1666    #[gpui::test]
1667    fn test_excerpt_buffer(cx: &mut MutableAppContext) {
1668        let buffer_1 = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'a'), cx));
1669        let buffer_2 = cx.add_model(|cx| Buffer::new(0, sample_text(6, 6, 'g'), cx));
1670
1671        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
1672
1673        let subscription = multibuffer.update(cx, |multibuffer, cx| {
1674            let subscription = multibuffer.subscribe();
1675            multibuffer.push_excerpt(
1676                ExcerptProperties {
1677                    buffer: &buffer_1,
1678                    range: Point::new(1, 2)..Point::new(2, 5),
1679                    header_height: 2,
1680                },
1681                cx,
1682            );
1683            assert_eq!(
1684                subscription.consume().into_inner(),
1685                [Edit {
1686                    old: 0..0,
1687                    new: 0..13
1688                }]
1689            );
1690
1691            multibuffer.push_excerpt(
1692                ExcerptProperties {
1693                    buffer: &buffer_1,
1694                    range: Point::new(3, 3)..Point::new(4, 4),
1695                    header_height: 1,
1696                },
1697                cx,
1698            );
1699            multibuffer.push_excerpt(
1700                ExcerptProperties {
1701                    buffer: &buffer_2,
1702                    range: Point::new(3, 1)..Point::new(3, 3),
1703                    header_height: 3,
1704                },
1705                cx,
1706            );
1707            assert_eq!(
1708                subscription.consume().into_inner(),
1709                [Edit {
1710                    old: 13..13,
1711                    new: 13..29
1712                }]
1713            );
1714
1715            subscription
1716        });
1717
1718        assert_eq!(
1719            multibuffer.read(cx).snapshot(cx).text(),
1720            concat!(
1721                "\n",      // Preserve newlines
1722                "\n",      //
1723                "bbbb\n",  //
1724                "ccccc\n", //
1725                "\n",      //
1726                "ddd\n",   //
1727                "eeee\n",  //
1728                "\n",      //
1729                "\n",      //
1730                "\n",      //
1731                "jj\n"     //
1732            )
1733        );
1734
1735        buffer_1.update(cx, |buffer, cx| {
1736            buffer.edit(
1737                [
1738                    Point::new(0, 0)..Point::new(0, 0),
1739                    Point::new(2, 1)..Point::new(2, 3),
1740                ],
1741                "\n",
1742                cx,
1743            );
1744        });
1745
1746        assert_eq!(
1747            multibuffer.read(cx).snapshot(cx).text(),
1748            concat!(
1749                "\n",     // Preserve newlines
1750                "\n",     //
1751                "bbbb\n", //
1752                "c\n",    //
1753                "cc\n",   //
1754                "\n",     //
1755                "ddd\n",  //
1756                "eeee\n", //
1757                "\n",     //
1758                "\n",     //
1759                "\n",     //
1760                "jj\n"    //
1761            )
1762        );
1763
1764        assert_eq!(
1765            subscription.consume().into_inner(),
1766            [Edit {
1767                old: 8..10,
1768                new: 8..9
1769            }]
1770        );
1771    }
1772
1773    #[gpui::test(iterations = 100)]
1774    fn test_random_excerpts(cx: &mut MutableAppContext, mut rng: StdRng) {
1775        let operations = env::var("OPERATIONS")
1776            .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
1777            .unwrap_or(10);
1778
1779        let mut buffers: Vec<ModelHandle<Buffer>> = Vec::new();
1780        let list = cx.add_model(|_| MultiBuffer::new(0));
1781        let mut excerpt_ids = Vec::new();
1782        let mut expected_excerpts = Vec::new();
1783        let mut old_versions = Vec::new();
1784
1785        for _ in 0..operations {
1786            match rng.gen_range(0..100) {
1787                0..=19 if !buffers.is_empty() => {
1788                    let buffer = buffers.choose(&mut rng).unwrap();
1789                    buffer.update(cx, |buf, cx| buf.randomly_edit(&mut rng, 1, cx));
1790                }
1791                _ => {
1792                    let buffer_handle = if buffers.is_empty() || rng.gen_bool(0.4) {
1793                        let base_text = RandomCharIter::new(&mut rng).take(10).collect::<String>();
1794                        buffers.push(cx.add_model(|cx| Buffer::new(0, base_text, cx)));
1795                        buffers.last().unwrap()
1796                    } else {
1797                        buffers.choose(&mut rng).unwrap()
1798                    };
1799
1800                    let buffer = buffer_handle.read(cx);
1801                    let end_ix = buffer.clip_offset(rng.gen_range(0..=buffer.len()), Bias::Right);
1802                    let start_ix = buffer.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
1803                    let header_height = rng.gen_range(0..=5);
1804                    let anchor_range = buffer.anchor_before(start_ix)..buffer.anchor_after(end_ix);
1805                    log::info!(
1806                        "Pushing excerpt wih header {}, buffer {}: {:?}[{:?}] = {:?}",
1807                        header_height,
1808                        buffer_handle.id(),
1809                        buffer.text(),
1810                        start_ix..end_ix,
1811                        &buffer.text()[start_ix..end_ix]
1812                    );
1813
1814                    let excerpt_id = list.update(cx, |list, cx| {
1815                        list.push_excerpt(
1816                            ExcerptProperties {
1817                                buffer: &buffer_handle,
1818                                range: start_ix..end_ix,
1819                                header_height,
1820                            },
1821                            cx,
1822                        )
1823                    });
1824                    excerpt_ids.push(excerpt_id);
1825                    expected_excerpts.push((buffer_handle.clone(), anchor_range, header_height));
1826                }
1827            }
1828
1829            if rng.gen_bool(0.3) {
1830                list.update(cx, |list, cx| {
1831                    old_versions.push((list.snapshot(cx), list.subscribe()));
1832                })
1833            }
1834
1835            let snapshot = list.read(cx).snapshot(cx);
1836
1837            let mut excerpt_starts = Vec::new();
1838            let mut expected_text = String::new();
1839            for (buffer, range, header_height) in &expected_excerpts {
1840                let buffer = buffer.read(cx);
1841                let buffer_range = range.to_offset(buffer);
1842
1843                for _ in 0..*header_height {
1844                    expected_text.push('\n');
1845                }
1846
1847                excerpt_starts.push(TextSummary::from(expected_text.as_str()));
1848                expected_text.extend(buffer.text_for_range(buffer_range.clone()));
1849                expected_text.push('\n');
1850            }
1851
1852            assert_eq!(snapshot.text(), expected_text);
1853
1854            let mut excerpt_starts = excerpt_starts.into_iter();
1855            for (buffer, range, _) in &expected_excerpts {
1856                let buffer_id = buffer.id();
1857                let buffer = buffer.read(cx);
1858                let buffer_range = range.to_offset(buffer);
1859                let buffer_start_point = buffer.offset_to_point(buffer_range.start);
1860                let buffer_start_point_utf16 =
1861                    buffer.text_summary_for_range::<PointUtf16, _>(0..buffer_range.start);
1862
1863                let excerpt_start = excerpt_starts.next().unwrap();
1864                let mut offset = excerpt_start.bytes;
1865                let mut buffer_offset = buffer_range.start;
1866                let mut point = excerpt_start.lines;
1867                let mut buffer_point = buffer_start_point;
1868                let mut point_utf16 = excerpt_start.lines_utf16;
1869                let mut buffer_point_utf16 = buffer_start_point_utf16;
1870                for byte in buffer.bytes_in_range(buffer_range.clone()).flatten() {
1871                    let left_offset = snapshot.clip_offset(offset, Bias::Left);
1872                    let right_offset = snapshot.clip_offset(offset, Bias::Right);
1873                    let buffer_left_offset = buffer.clip_offset(buffer_offset, Bias::Left);
1874                    let buffer_right_offset = buffer.clip_offset(buffer_offset, Bias::Right);
1875                    assert_eq!(
1876                        left_offset,
1877                        excerpt_start.bytes + (buffer_left_offset - buffer_range.start),
1878                        "clip_offset({:?}, Left). buffer: {:?}, buffer offset: {:?}",
1879                        offset,
1880                        buffer_id,
1881                        buffer_offset,
1882                    );
1883                    assert_eq!(
1884                        right_offset,
1885                        excerpt_start.bytes + (buffer_right_offset - buffer_range.start),
1886                        "clip_offset({:?}, Right). buffer: {:?}, buffer offset: {:?}",
1887                        offset,
1888                        buffer_id,
1889                        buffer_offset,
1890                    );
1891
1892                    let left_point = snapshot.clip_point(point, Bias::Left);
1893                    let right_point = snapshot.clip_point(point, Bias::Right);
1894                    let buffer_left_point = buffer.clip_point(buffer_point, Bias::Left);
1895                    let buffer_right_point = buffer.clip_point(buffer_point, Bias::Right);
1896                    assert_eq!(
1897                        left_point,
1898                        excerpt_start.lines + (buffer_left_point - buffer_start_point),
1899                        "clip_point({:?}, Left). buffer: {:?}, buffer point: {:?}",
1900                        point,
1901                        buffer_id,
1902                        buffer_point,
1903                    );
1904                    assert_eq!(
1905                        right_point,
1906                        excerpt_start.lines + (buffer_right_point - buffer_start_point),
1907                        "clip_point({:?}, Right). buffer: {:?}, buffer point: {:?}",
1908                        point,
1909                        buffer_id,
1910                        buffer_point,
1911                    );
1912
1913                    let left_point_utf16 = snapshot.clip_point_utf16(point_utf16, Bias::Left);
1914                    let right_point_utf16 = snapshot.clip_point_utf16(point_utf16, Bias::Right);
1915                    let buffer_left_point_utf16 =
1916                        buffer.clip_point_utf16(buffer_point_utf16, Bias::Left);
1917                    let buffer_right_point_utf16 =
1918                        buffer.clip_point_utf16(buffer_point_utf16, Bias::Right);
1919                    assert_eq!(
1920                        left_point_utf16,
1921                        excerpt_start.lines_utf16
1922                            + (buffer_left_point_utf16 - buffer_start_point_utf16),
1923                        "clip_point_utf16({:?}, Left). buffer: {:?}, buffer point_utf16: {:?}",
1924                        point_utf16,
1925                        buffer_id,
1926                        buffer_point_utf16,
1927                    );
1928                    assert_eq!(
1929                        right_point_utf16,
1930                        excerpt_start.lines_utf16
1931                            + (buffer_right_point_utf16 - buffer_start_point_utf16),
1932                        "clip_point_utf16({:?}, Right). buffer: {:?}, buffer point_utf16: {:?}",
1933                        point_utf16,
1934                        buffer_id,
1935                        buffer_point_utf16,
1936                    );
1937
1938                    assert_eq!(
1939                        snapshot.point_to_offset(left_point),
1940                        left_offset,
1941                        "point_to_offset({:?})",
1942                        left_point,
1943                    );
1944                    assert_eq!(
1945                        snapshot.offset_to_point(left_offset),
1946                        left_point,
1947                        "offset_to_point({:?})",
1948                        left_offset,
1949                    );
1950
1951                    offset += 1;
1952                    buffer_offset += 1;
1953                    if *byte == b'\n' {
1954                        point += Point::new(1, 0);
1955                        point_utf16 += PointUtf16::new(1, 0);
1956                        buffer_point += Point::new(1, 0);
1957                        buffer_point_utf16 += PointUtf16::new(1, 0);
1958                    } else {
1959                        point += Point::new(0, 1);
1960                        point_utf16 += PointUtf16::new(0, 1);
1961                        buffer_point += Point::new(0, 1);
1962                        buffer_point_utf16 += PointUtf16::new(0, 1);
1963                    }
1964                }
1965            }
1966
1967            for (row, line) in expected_text.split('\n').enumerate() {
1968                assert_eq!(
1969                    snapshot.line_len(row as u32),
1970                    line.len() as u32,
1971                    "line_len({}).",
1972                    row
1973                );
1974            }
1975
1976            for _ in 0..10 {
1977                let end_ix = snapshot.clip_offset(rng.gen_range(0..=snapshot.len()), Bias::Right);
1978                let start_ix = snapshot.clip_offset(rng.gen_range(0..=end_ix), Bias::Left);
1979
1980                assert_eq!(
1981                    snapshot
1982                        .text_for_range(start_ix..end_ix)
1983                        .collect::<String>(),
1984                    &expected_text[start_ix..end_ix],
1985                    "incorrect text for range {:?}",
1986                    start_ix..end_ix
1987                );
1988
1989                let expected_summary = TextSummary::from(&expected_text[start_ix..end_ix]);
1990                assert_eq!(
1991                    snapshot.text_summary_for_range::<TextSummary, _>(start_ix..end_ix),
1992                    expected_summary,
1993                    "incorrect summary for range {:?}",
1994                    start_ix..end_ix
1995                );
1996            }
1997        }
1998
1999        let snapshot = list.read(cx).snapshot(cx);
2000        for (old_snapshot, subscription) in old_versions {
2001            let edits = subscription.consume().into_inner();
2002
2003            log::info!(
2004                "applying edits since old text: {:?}: {:?}",
2005                old_snapshot.text(),
2006                edits,
2007            );
2008
2009            let mut text = old_snapshot.text();
2010            for edit in edits {
2011                let new_text: String = snapshot.text_for_range(edit.new.clone()).collect();
2012                text.replace_range(edit.new.start..edit.new.start + edit.old.len(), &new_text);
2013            }
2014            assert_eq!(text.to_string(), snapshot.text());
2015        }
2016    }
2017
2018    #[gpui::test]
2019    fn test_history(cx: &mut MutableAppContext) {
2020        let buffer_1 = cx.add_model(|cx| Buffer::new(0, "1234", cx));
2021        let buffer_2 = cx.add_model(|cx| Buffer::new(0, "5678", cx));
2022        let multibuffer = cx.add_model(|_| MultiBuffer::new(0));
2023        let group_interval = multibuffer.read(cx).history.group_interval;
2024        multibuffer.update(cx, |multibuffer, cx| {
2025            multibuffer.push_excerpt(
2026                ExcerptProperties {
2027                    buffer: &buffer_1,
2028                    range: 0..buffer_1.read(cx).len(),
2029                    header_height: 0,
2030                },
2031                cx,
2032            );
2033            multibuffer.push_excerpt(
2034                ExcerptProperties {
2035                    buffer: &buffer_2,
2036                    range: 0..buffer_2.read(cx).len(),
2037                    header_height: 0,
2038                },
2039                cx,
2040            );
2041        });
2042
2043        let mut now = Instant::now();
2044
2045        multibuffer.update(cx, |multibuffer, cx| {
2046            multibuffer.start_transaction_at(now, cx);
2047            multibuffer.edit(
2048                [
2049                    Point::new(0, 0)..Point::new(0, 0),
2050                    Point::new(1, 0)..Point::new(1, 0),
2051                ],
2052                "A",
2053                cx,
2054            );
2055            multibuffer.edit(
2056                [
2057                    Point::new(0, 1)..Point::new(0, 1),
2058                    Point::new(1, 1)..Point::new(1, 1),
2059                ],
2060                "B",
2061                cx,
2062            );
2063            multibuffer.end_transaction_at(now, cx);
2064            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678\n");
2065
2066            now += 2 * group_interval;
2067            multibuffer.start_transaction_at(now, cx);
2068            multibuffer.edit([2..2], "C", cx);
2069            multibuffer.end_transaction_at(now, cx);
2070            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678\n");
2071
2072            multibuffer.undo(cx);
2073            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678\n");
2074
2075            multibuffer.undo(cx);
2076            assert_eq!(multibuffer.read(cx).text(), "1234\n5678\n");
2077
2078            multibuffer.redo(cx);
2079            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678\n");
2080
2081            multibuffer.redo(cx);
2082            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678\n");
2083
2084            buffer_1.update(cx, |buffer_1, cx| buffer_1.undo(cx));
2085            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678\n");
2086
2087            multibuffer.undo(cx);
2088            assert_eq!(multibuffer.read(cx).text(), "1234\n5678\n");
2089
2090            multibuffer.redo(cx);
2091            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678\n");
2092
2093            multibuffer.redo(cx);
2094            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678\n");
2095
2096            multibuffer.undo(cx);
2097            assert_eq!(multibuffer.read(cx).text(), "AB1234\nAB5678\n");
2098
2099            buffer_1.update(cx, |buffer_1, cx| buffer_1.redo(cx));
2100            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678\n");
2101
2102            multibuffer.undo(cx);
2103            assert_eq!(multibuffer.read(cx).text(), "ABC1234\nAB5678\n");
2104        });
2105    }
2106}