Allow scrollPastEnd to be set from the editor

spec/text-editor-presenter-spec.coffee

@@ -647,17 +647,6 @@ describe "TextEditorPresenter", ->
             expectStateUpdate presenter, -> atom.config.set("editor.scrollPastEnd", false)
             expect(getState(presenter).verticalScrollbar.scrollHeight).toBe presenter.contentHeight
 
-          it "doesn't add the computed clientHeight to the computed scrollHeight if editor.scrollPastEnd is true but the presenter is created with scrollPastEnd as false", ->
-            presenter = buildPresenter(scrollTop: 10, explicitHeight: 50, horizontalScrollbarHeight: 10, scrollPastEnd: false)
-            expectStateUpdate presenter, -> presenter.setScrollTop(300)
-            expect(getState(presenter).verticalScrollbar.scrollHeight).toBe presenter.contentHeight
-
-            expectStateUpdate presenter, -> atom.config.set("editor.scrollPastEnd", true)
-            expect(getState(presenter).verticalScrollbar.scrollHeight).toBe presenter.contentHeight
-
-            expectStateUpdate presenter, -> atom.config.set("editor.scrollPastEnd", false)
-            expect(getState(presenter).verticalScrollbar.scrollHeight).toBe presenter.contentHeight
-
       describe ".scrollTop", ->
         it "tracks the value of ::scrollTop", ->
           presenter = buildPresenter(scrollTop: 10, explicitHeight: 20, horizontalScrollbarHeight: 10)

spec/text-editor-spec.coffee

@@ -5689,6 +5689,40 @@ describe "TextEditor", ->
       editor.selectPageUp()
       expect(editor.getSelectedBufferRanges()).toEqual [[[0, 0], [12, 2]]]
 
+  describe "scroll past end", ->
+    it "returns the scrollPastEnd setting on the editor instance if set, or 'editor.scrollPastEnd' otherwise", ->
+      atom.config.set('editor.scrollPastEnd', true)
+      expect(editor.getScrollPastEnd()).toBe(true)
+
+      atom.config.set('editor.scrollPastEnd', false)
+      expect(editor.getScrollPastEnd()).toBe(false)
+
+      editor.setScrollPastEnd(true)
+      expect(editor.getScrollPastEnd()).toBe(true)
+
+      atom.config.set('editor.scrollPastEnd', true)
+      atom.config.set('editor.scrollPastEnd', false)
+      expect(editor.getScrollPastEnd()).toBe(true)
+
+    it "emits a onDidChangeScrollPastEnd event when it changes", ->
+      scrollPastEndSpy = jasmine.createSpy('onDidChangeScrollPastEnd')
+      editor.onDidChangeScrollPastEnd(scrollPastEndSpy)
+
+      atom.config.set('editor.scrollPastEnd', true)
+      expect(scrollPastEndSpy).toHaveBeenCalled()
+
+      scrollPastEndSpy.reset()
+      editor.setScrollPastEnd(false)
+      expect(scrollPastEndSpy).toHaveBeenCalled()
+
+      scrollPastEndSpy.reset()
+      editor.setScrollPastEnd(false)
+      expect(scrollPastEndSpy).not.toHaveBeenCalled()
+
+      atom.config.set('editor.scrollPastEnd', false)
+      atom.config.set('editor.scrollPastEnd', true)
+      expect(scrollPastEndSpy).not.toHaveBeenCalled()
+
   describe "::setFirstVisibleScreenRow() and ::getFirstVisibleScreenRow()", ->
     beforeEach ->
       line = Array(9).join('0123456789')

src/text-editor-component.coffee

@@ -43,7 +43,7 @@ class TextEditorComponent
       @assert domNode?, "TextEditorComponent::domNode was set to null."
       @domNodeValue = domNode
 
-  constructor: ({@editor, @hostElement, @rootElement, @stylesElement, @useShadowDOM, tileSize, @views, @themes, @config, @workspace, @assert, @grammars, scrollPastEnd}) ->
+  constructor: ({@editor, @hostElement, @rootElement, @stylesElement, @useShadowDOM, tileSize, @views, @themes, @config, @workspace, @assert, @grammars}) ->
     @tileSize = tileSize if tileSize?
     @disposables = new CompositeDisposable
 
@@ -61,7 +61,6 @@ class TextEditorComponent
       stoppedScrollingDelay: 200
       config: @config
       lineTopIndex: lineTopIndex
-      scrollPastEnd: scrollPastEnd
 
     @presenter.onDidUpdateState(@requestUpdate)
 

src/text-editor-element.coffee

@@ -17,7 +17,6 @@ class TextEditorElement extends HTMLElement
   focusOnAttach: false
   hasTiledRendering: true
   logicalDisplayBuffer: true
-  scrollPastEnd: true
   autoHeight: true
 
   createdCallback: ->
@@ -91,7 +90,7 @@ class TextEditorElement extends HTMLElement
     @subscriptions.add @component.onDidChangeScrollLeft =>
       @emitter.emit("did-change-scroll-left", arguments...)
 
-  initialize: (model, {@views, @config, @themes, @workspace, @assert, @styles, @grammars}, @autoHeight = true, @scrollPastEnd = true) ->
+  initialize: (model, {@views, @config, @themes, @workspace, @assert, @styles, @grammars}, @autoHeight = true) ->
     throw new Error("Must pass a views parameter when initializing TextEditorElements") unless @views?
     throw new Error("Must pass a config parameter when initializing TextEditorElements") unless @config?
     throw new Error("Must pass a themes parameter when initializing TextEditorElements") unless @themes?
@@ -148,7 +147,6 @@ class TextEditorElement extends HTMLElement
       workspace: @workspace
       assert: @assert
       grammars: @grammars
-      scrollPastEnd: @scrollPastEnd
     )
     @rootElement.appendChild(@component.getDomNode())
 

src/text-editor-presenter.coffee

@@ -13,7 +13,7 @@ class TextEditorPresenter
   minimumReflowInterval: 200
 
   constructor: (params) ->
-    {@model, @config, @lineTopIndex, scrollPastEnd} = params
+    {@model, @config, @lineTopIndex} = params
     {@cursorBlinkPeriod, @cursorBlinkResumeDelay, @stoppedScrollingDelay, @tileSize} = params
     {@contentFrameWidth} = params
     {@displayLayer} = @model
@@ -44,8 +44,6 @@ class TextEditorPresenter
     @startReflowing() if @continuousReflow
     @updating = false
 
-    @scrollPastEndOverride = scrollPastEnd ? true
-
   setLinesYardstick: (@linesYardstick) ->
 
   getLinesYardstick: -> @linesYardstick
@@ -160,6 +158,9 @@ class TextEditorPresenter
     @disposables.add @model.onDidChangeMini =>
       @shouldUpdateDecorations = true
       @emitDidUpdateState()
+    @disposables.add @model.onDidChangeScrollPastEnd =>
+      @updateScrollHeight()
+      @emitDidUpdateState()
 
     @disposables.add @model.onDidChangeLineNumberGutterVisible(@emitDidUpdateState.bind(this))
 
@@ -173,7 +174,6 @@ class TextEditorPresenter
   observeConfig: ->
     configParams = {scope: @model.getRootScopeDescriptor()}
 
-    @scrollPastEnd = @config.get('editor.scrollPastEnd', configParams)
     @showLineNumbers = @config.get('editor.showLineNumbers', configParams)
 
     if @configDisposables?
@@ -183,11 +183,6 @@ class TextEditorPresenter
     @configDisposables = new CompositeDisposable
     @disposables.add(@configDisposables)
 
-    @configDisposables.add @config.onDidChange 'editor.scrollPastEnd', configParams, ({newValue}) =>
-      @scrollPastEnd = newValue
-      @updateScrollHeight()
-
-      @emitDidUpdateState()
     @configDisposables.add @config.onDidChange 'editor.showLineNumbers', configParams, ({newValue}) =>
       @showLineNumbers = newValue
       @emitDidUpdateState()
@@ -651,7 +646,7 @@ class TextEditorPresenter
     return unless @contentHeight? and @clientHeight?
 
     contentHeight = @contentHeight
-    if @scrollPastEnd and @scrollPastEndOverride
+    if @model.getScrollPastEnd()
       extraScrollHeight = @clientHeight - (@lineHeight * 3)
       contentHeight += extraScrollHeight if extraScrollHeight > 0
     scrollHeight = Math.max(contentHeight, @height)

src/text-editor.coffee

@@ -142,7 +142,6 @@ class TextEditor extends Model
     @cursorsByMarkerId = new Map
     @selections = []
     @autoHeight ?= true
-    @scrollPastEnd ?= true
     @hasTerminatedPendingState = false
 
     @showInvisibles ?= true
@@ -283,6 +282,9 @@ class TextEditor extends Model
     subscriptions.add @config.onDidChange 'editor.softWrapHangingIndent', scope: scopeDescriptor, @resetDisplayLayer.bind(this)
     subscriptions.add @config.onDidChange 'editor.softWrapAtPreferredLineLength', scope: scopeDescriptor, @resetDisplayLayer.bind(this)
     subscriptions.add @config.onDidChange 'editor.preferredLineLength', scope: scopeDescriptor, @resetDisplayLayer.bind(this)
+    subscriptions.add @config.onDidChange 'editor.scrollPastEnd', scope: scopeDescriptor, =>
+      unless @scrollPastEnd?
+        @emitter.emit('did-change-scroll-past-end')
 
     @resetDisplayLayer()
 
@@ -3320,6 +3322,20 @@ class TextEditor extends Model
     scrollEvent = {screenRange, options}
     @emitter.emit "did-request-autoscroll", scrollEvent
 
+  getScrollPastEnd: ->
+    if @scrollPastEnd?
+      @scrollPastEnd
+    else
+      @config.get('editor.scrollPastEnd', scope: @getRootScopeDescriptor())
+
+  setScrollPastEnd: (scrollPastEnd) ->
+    if scrollPastEnd isnt @scrollPastEnd
+      @scrollPastEnd = scrollPastEnd
+      @emitter.emit('did-change-scroll-past-end')
+
+  onDidChangeScrollPastEnd: (callback) ->
+    @emitter.on('did-change-scroll-past-end', callback)
+
   getHorizontalScrollbarHeight: ->
     Grim.deprecate("This is now a view method. Call TextEditorElement::getHorizontalScrollbarHeight instead.")
 
@@ -3376,7 +3392,7 @@ class TextEditor extends Model
 
   # Get the Element for the editor.
   getElement: ->
-    @editorElement ?= new TextEditorElement().initialize(this, atom, @autoHeight, @scrollPastEnd)
+    @editorElement ?= new TextEditorElement().initialize(this, atom, @autoHeight)
 
   # Essential: Retrieves the greyed out placeholder of a mini editor.
   #
@@ -3470,7 +3486,7 @@ class TextEditor extends Model
   setFirstVisibleScreenRow: (screenRow, fromView) ->
     unless fromView
       maxScreenRow = @getScreenLineCount() - 1
-      unless @config.get('editor.scrollPastEnd') and @scrollPastEnd
+      unless @getScrollPastEnd()
         if @height? and @lineHeightInPixels?
           maxScreenRow -= Math.floor(@height / @lineHeightInPixels)
       screenRow = Math.max(Math.min(screenRow, maxScreenRow), 0)