Add "Continuous Reflow" mode

spec/text-editor-component-spec.coffee

@@ -450,6 +450,31 @@ describe "TextEditorComponent", ->
         nextAnimationFrame()
         expect(component.lineNodeForScreenRow(10).innerHTML).toBe '<span class="indent-guide"><span class="invisible-character">C</span></span><span class="invisible-character">E</span>'
 
+      it "keeps rebuilding lines when continuous reflow is on", ->
+        atom.config.set("editor.continuousReflow", true)
+        nextAnimationFrame()
+
+        oldLineNodes = componentNode.querySelectorAll(".line")
+
+        advanceClock(10)
+        expect(nextAnimationFrame).toBe(noAnimationFrame)
+
+        advanceClock(component.presenter.minimumReflowInterval - 10)
+        nextAnimationFrame()
+
+        newLineNodes = componentNode.querySelectorAll(".line")
+        expect(oldLineNodes).not.toEqual(newLineNodes)
+        oldLineNodes = newLineNodes
+
+        atom.config.set("editor.continuousReflow", false)
+        nextAnimationFrame()
+
+        newLineNodes = componentNode.querySelectorAll(".line")
+        expect(oldLineNodes).toEqual(newLineNodes)
+
+        advanceClock(component.presenter.minimumReflowInterval)
+        expect(nextAnimationFrame).toBe(noAnimationFrame)
+
       describe "when soft wrapping is enabled", ->
         beforeEach ->
           editor.setText "a line that wraps \n"
@@ -827,6 +852,31 @@ describe "TextEditorComponent", ->
       expect(componentNode.querySelector('.gutter').style.display).toBe ''
       expect(component.lineNumberNodeForScreenRow(3)?).toBe true
 
+    it "keeps rebuilding line numbers when continuous reflow is on", ->
+      atom.config.set("editor.continuousReflow", true)
+      nextAnimationFrame()
+
+      oldLineNodes = componentNode.querySelectorAll(".line-number")
+
+      advanceClock(10)
+      expect(nextAnimationFrame).toBe(noAnimationFrame)
+
+      advanceClock(component.presenter.minimumReflowInterval - 10)
+      nextAnimationFrame()
+
+      newLineNodes = componentNode.querySelectorAll(".line-number")
+      expect(oldLineNodes).not.toEqual(newLineNodes)
+      oldLineNodes = newLineNodes
+
+      atom.config.set("editor.continuousReflow", false)
+      nextAnimationFrame()
+
+      newLineNodes = componentNode.querySelectorAll(".line-number")
+      expect(oldLineNodes).toEqual(newLineNodes)
+
+      advanceClock(component.presenter.minimumReflowInterval)
+      expect(nextAnimationFrame).toBe(noAnimationFrame)
+
     describe "fold decorations", ->
       describe "rendering fold decorations", ->
         it "adds the foldable class to line numbers when the line is foldable", ->

src/config-schema.coffee

@@ -217,6 +217,10 @@ module.exports =
         type: 'boolean'
         default: process.platform isnt 'darwin'
         description: 'Increase/decrease the editor font size when pressing the Ctrl key and scrolling the mouse up/down.'
+      continuousReflow:
+        type: 'boolean'
+        default: false
+        description: 'Track down expensive layouts or style recalculations by continously reflowing the editor. (Has performance overhead)'
 
 if process.platform in ['win32', 'linux']
   module.exports.core.properties.autoHideMenuBar =

src/line-number-gutter-component.coffee

@@ -62,6 +62,9 @@ class LineNumberGutterComponent extends TiledComponent
 
   buildComponentForTile: (id) -> new LineNumbersTileComponent({id})
 
+  shouldRecreateAllTilesOnUpdate: ->
+    @newState.continuousReflow
+
   ###
   Section: Private Methods
   ###

src/lines-component.coffee

@@ -32,7 +32,7 @@ class LinesComponent extends TiledComponent
     @domNode
 
   shouldRecreateAllTilesOnUpdate: ->
-    @oldState.indentGuidesVisible isnt @newState.indentGuidesVisible
+    @oldState.indentGuidesVisible isnt @newState.indentGuidesVisible or @newState.continuousReflow
 
   beforeUpdateSync: (state) ->
     if @newState.maxHeight isnt @oldState.maxHeight

src/text-editor-presenter.coffee

@@ -11,6 +11,7 @@ class TextEditorPresenter
   mouseWheelScreenRow: null
   scopedCharacterWidthsChangeCount: 0
   overlayDimensions: {}
+  minimumReflowInterval: 200
 
   constructor: (params) ->
     {@model, @autoHeight, @explicitHeight, @contentFrameWidth, @scrollTop, @scrollLeft, @boundingClientRect, @windowWidth, @windowHeight, @gutterWidth} = params
@@ -35,6 +36,7 @@ class TextEditorPresenter
     @observeConfig()
     @buildState()
     @startBlinkingCursors() if @focused
+    @startReflowing() if @continuousReflow
     @updating = false
 
   destroy: ->
@@ -72,6 +74,7 @@ class TextEditorPresenter
     @updateStartRow()
     @updateEndRow()
     @updateCommonGutterState()
+    @updateReflowState()
 
     @updateFocusedState() if @shouldUpdateFocusedState
     @updateHeightState() if @shouldUpdateHeightState
@@ -169,6 +172,7 @@ class TextEditorPresenter
   observeConfig: ->
     configParams = {scope: @model.getRootScopeDescriptor()}
 
+    @continuousReflow = atom.config.get('editor.continuousReflow', configParams)
     @scrollPastEnd = atom.config.get('editor.scrollPastEnd', configParams)
     @showLineNumbers = atom.config.get('editor.showLineNumbers', configParams)
     @showIndentGuide = atom.config.get('editor.showIndentGuide', configParams)
@@ -199,6 +203,16 @@ class TextEditorPresenter
 
       @emitDidUpdateState()
 
+    @configDisposables.add atom.config.onDidChange 'editor.continuousReflow', configParams, ({newValue}) =>
+      @continuousReflow = newValue
+
+      if @continuousReflow
+        @startReflowing()
+      else
+        @stopReflowing()
+
+      @emitDidUpdateState()
+
   didChangeGrammar: ->
     @observeConfig()
     @shouldUpdateContentState = true
@@ -254,6 +268,17 @@ class TextEditorPresenter
 
     @resetTrackedUpdates()
 
+  updateReflowState: ->
+    @state.content.continuousReflow = @continuousReflow
+    @lineNumberGutter.continuousReflow = @continuousReflow
+
+  startReflowing: ->
+    @reflowingInterval = setInterval(@emitDidUpdateState.bind(this), @minimumReflowInterval)
+
+  stopReflowing: ->
+    clearInterval(@reflowingInterval)
+    @reflowingInterval = null
+
   updateFocusedState: ->
     @state.focused = @focused