Track horizontal/vertical scrollbar height/width in presenter

spec/text-editor-presenter-spec.coffee

@@ -77,6 +77,21 @@ describe "TextEditorPresenter", ->
         expectStateUpdate presenter, -> advanceClock(100)
         expect(presenter.state.scrollingVertically).toBe false
 
+    describe ".scrollbars", ->
+      describe ".horizontalHeight", ->
+        it "tracks the value of ::horizontalScrollbarHeight", ->
+          presenter = new TextEditorPresenter(model: editor, horizontalScrollbarHeight: 10)
+          expect(presenter.state.scrollbars.horizontalHeight).toBe 10
+          expectStateUpdate presenter, -> presenter.setHorizontalScrollbarHeight(20)
+          expect(presenter.state.scrollbars.horizontalHeight).toBe 20
+
+      describe ".verticalWidth", ->
+        it "is assigned based on ::verticalScrollbarWidth", ->
+          presenter = new TextEditorPresenter(model: editor, verticalScrollbarWidth: 10)
+          expect(presenter.state.scrollbars.verticalWidth).toBe 10
+          expectStateUpdate presenter, -> presenter.setVerticalScrollbarWidth(20)
+          expect(presenter.state.scrollbars.verticalWidth).toBe 20
+
     describe ".content", ->
       describe ".scrollWidth", ->
         it "is initialized as the max of the clientWidth and the width of the longest line", ->

src/text-editor-presenter.coffee

@@ -11,6 +11,7 @@ class TextEditorPresenter
 
   constructor: (params) ->
     {@model, @clientHeight, @clientWidth, @scrollTop, @scrollLeft} = params
+    {@horizontalScrollbarHeight, @verticalScrollbarWidth} = params
     {@lineHeight, @baseCharacterWidth, @lineOverdrawMargin, @backgroundColor, @gutterBackgroundColor} = params
     {@cursorBlinkPeriod, @cursorBlinkResumeDelay, @stoppedScrollingDelay} = params
 
@@ -51,6 +52,7 @@ class TextEditorPresenter
   buildState: ->
     @state =
       scrollingVertically: false
+      scrollbars: {}
       content:
         blinkCursorsOff: false
         lines: {}
@@ -62,6 +64,7 @@ class TextEditorPresenter
 
   updateState: ->
     @updateVerticalScrollState()
+    @updateScrollbarsState()
     @updateContentState()
     @updateLinesState()
     @updateCursorsState()
@@ -74,6 +77,11 @@ class TextEditorPresenter
     @state.scrollHeight = @computeScrollHeight()
     @state.scrollTop = @getScrollTop()
 
+  updateScrollbarsState: ->
+    @state.scrollbars.horizontalHeight = @getHorizontalScrollbarHeight()
+    @state.scrollbars.verticalWidth = @getVerticalScrollbarWidth()
+    @emitter.emit 'did-update-state'
+
   updateContentState: ->
     @state.content.scrollWidth = @computeScrollWidth()
     @state.content.scrollLeft = @getScrollLeft()
@@ -391,6 +399,16 @@ class TextEditorPresenter
 
   getScrollLeft: -> @scrollLeft
 
+  setHorizontalScrollbarHeight: (@horizontalScrollbarHeight) ->
+    @updateScrollbarsState()
+
+  getHorizontalScrollbarHeight: -> @horizontalScrollbarHeight
+
+  setVerticalScrollbarWidth: (@verticalScrollbarWidth) ->
+    @updateScrollbarsState()
+
+  getVerticalScrollbarWidth: -> @verticalScrollbarWidth
+
   setClientHeight: (@clientHeight) ->
     @updateVerticalScrollState()
     @updateLinesState()