Merge pull request #13820 from atom/mb-ns-long-lines

Avoid hangs when opening minified files

benchmarks/text-editor-large-file-construction.bench.js

@@ -26,7 +26,7 @@ export default async function ({test}) {
     console.log(text.length / 1024)
 
     let t0 = window.performance.now()
-    const buffer = new TextBuffer(text)
+    const buffer = new TextBuffer({text})
     const editor = new TextEditor({buffer, largeFileMode: true})
     atom.workspace.getActivePane().activateItem(editor)
     let t1 = window.performance.now()

benchmarks/text-editor-long-lines.bench.js

@@ -0,0 +1,97 @@
+/** @babel */
+
+import path from 'path'
+import fs from 'fs'
+import {TextEditor, TextBuffer} from 'atom'
+
+const SIZES_IN_KB = [
+  512,
+  1024,
+  2048
+]
+const REPEATED_TEXT = fs.readFileSync(path.join(__dirname, '..', 'spec', 'fixtures', 'sample.js'), 'utf8').replace(/\n/g, '')
+const TEXT = REPEATED_TEXT.repeat(Math.ceil(SIZES_IN_KB[SIZES_IN_KB.length - 1] * 1024 / REPEATED_TEXT.length))
+
+export default async function ({test}) {
+  const data = []
+
+  const workspaceElement = atom.views.getView(atom.workspace)
+  document.body.appendChild(workspaceElement)
+
+  atom.packages.loadPackages()
+  await atom.packages.activate()
+
+  console.log(atom.getLoadSettings().resourcePath);
+
+  for (let pane of atom.workspace.getPanes()) {
+    pane.destroy()
+  }
+
+  for (const sizeInKB of SIZES_IN_KB) {
+    const text = TEXT.slice(0, sizeInKB * 1024)
+    console.log(text.length / 1024)
+
+    let t0 = window.performance.now()
+    const buffer = new TextBuffer({text})
+    const editor = new TextEditor({buffer, largeFileMode: true})
+    editor.setGrammar(atom.grammars.grammarForScopeName('source.js'))
+    atom.workspace.getActivePane().activateItem(editor)
+    let t1 = window.performance.now()
+
+    data.push({
+      name: 'Opening a large single-line file',
+      x: sizeInKB,
+      duration: t1 - t0
+    })
+
+    const tickDurations = []
+    for (let i = 0; i < 20; i++) {
+      await timeout(50)
+      t0 = window.performance.now()
+      await timeout(0)
+      t1 = window.performance.now()
+      tickDurations[i] = t1 - t0
+    }
+
+    data.push({
+      name: 'Max time event loop was blocked after opening a large single-line file',
+      x: sizeInKB,
+      duration: Math.max(...tickDurations)
+    })
+
+    t0 = window.performance.now()
+    editor.setCursorScreenPosition(editor.element.screenPositionForPixelPosition({
+      top: 100,
+      left: 30
+    }))
+    t1 = window.performance.now()
+
+    data.push({
+      name: 'Clicking the editor after opening a large single-line file',
+      x: sizeInKB,
+      duration: t1 - t0
+    })
+
+    t0 = window.performance.now()
+    editor.element.setScrollTop(editor.element.getScrollTop() + 100)
+    t1 = window.performance.now()
+
+    data.push({
+      name: 'Scrolling down after opening a large single-line file',
+      x: sizeInKB,
+      duration: t1 - t0
+    })
+
+    editor.destroy()
+    buffer.destroy()
+    await timeout(10000)
+  }
+
+  workspaceElement.remove()
+
+  return data
+}
+
+function timeout (duration) {
+  return new Promise((resolve) => setTimeout(resolve, duration))
+}

src/text-editor.coffee

@@ -16,6 +16,7 @@ TextEditorElement = require './text-editor-element'
 {isDoubleWidthCharacter, isHalfWidthCharacter, isKoreanCharacter, isWrapBoundary} = require './text-utils'
 
 ZERO_WIDTH_NBSP = '\ufeff'
+MAX_SCREEN_LINE_LENGTH = 500
 
 # Essential: This class represents all essential editing state for a single
 # {TextBuffer}, including cursor and selection positions, folds, and soft wraps.
@@ -2964,7 +2965,7 @@ class TextEditor extends Model
       else
         @getEditorWidthInChars()
     else
-      Infinity
+      MAX_SCREEN_LINE_LENGTH
 
   ###
   Section: Indentation

src/tokenized-buffer.coffee

@@ -8,6 +8,8 @@ ScopeDescriptor = require './scope-descriptor'
 TokenizedBufferIterator = require './tokenized-buffer-iterator'
 NullGrammar = require './null-grammar'
 
+MAX_LINE_LENGTH_TO_TOKENIZE = 500
+
 module.exports =
 class TokenizedBuffer extends Model
   grammar: null
@@ -251,6 +253,8 @@ class TokenizedBuffer extends Model
 
   buildTokenizedLineForRowWithText: (row, text, ruleStack = @stackForRow(row - 1), openScopes = @openScopesForRow(row)) ->
     lineEnding = @buffer.lineEndingForRow(row)
+    if text.length > MAX_LINE_LENGTH_TO_TOKENIZE
+      text = text.slice(0, MAX_LINE_LENGTH_TO_TOKENIZE)
     {tags, ruleStack} = @grammar.tokenizeLine(text, ruleStack, row is 0, false)
     new TokenizedLine({openScopes, text, tags, ruleStack, lineEnding, @tokenIterator})