multi_buffer.rs

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