Update scrollWidth when the max line length / default char width changes

spec/display-buffer-spec.coffee

@@ -1038,7 +1038,6 @@ describe "DisplayBuffer", ->
       displayBuffer.manageScrollPosition = true
       displayBuffer.setLineHeightInPixels(10)
       displayBuffer.setDefaultCharWidth(10)
-      displayBuffer.updateAllScreenLines()
 
     it "disallows negative values", ->
       displayBuffer.setWidth(displayBuffer.getScrollWidth() + 100)
@@ -1063,7 +1062,6 @@ describe "DisplayBuffer", ->
       displayBuffer.setHorizontalScrollbarHeight(0)
       displayBuffer.setHeight(50)
       displayBuffer.setWidth(50)
-      displayBuffer.updateAllScreenLines()
 
     it "sets the scroll top and scroll left so the given screen position is in view", ->
       displayBuffer.scrollToScreenPosition([8, 20])
@@ -1079,3 +1077,21 @@ describe "DisplayBuffer", ->
       it "does not scroll vertically if the position is already in view", ->
         displayBuffer.scrollToScreenPosition([4, 20], center: true)
         expect(displayBuffer.getScrollTop()).toBe 0
+
+  describe "scroll width", ->
+    cursorWidth = 1
+    beforeEach ->
+      displayBuffer.setDefaultCharWidth(10)
+
+    it "recomputes the scroll width when the default character width changes", ->
+      expect(displayBuffer.getScrollWidth()).toBe 10 * 65 + cursorWidth
+
+      displayBuffer.setDefaultCharWidth(12)
+      expect(displayBuffer.getScrollWidth()).toBe 12 * 65 + cursorWidth
+
+    it "recomputes the scroll width when the max line length changes", ->
+      buffer.insert([6, 12], ' ')
+      expect(displayBuffer.getScrollWidth()).toBe 10 * 66 + cursorWidth
+
+      buffer.delete([[6, 10], [6, 12]], ' ')
+      expect(displayBuffer.getScrollWidth()).toBe 10 * 64 + cursorWidth

spec/editor-component-spec.coffee

@@ -62,7 +62,6 @@ describe "EditorComponent", ->
 
       node.style.height = editor.getLineCount() * lineHeightInPixels + 'px'
       node.style.width = '1000px'
-      editor.displayBuffer.updateAllScreenLines()
       component.measureScrollView()
       nextTick()
 

spec/editor-spec.coffee

@@ -733,7 +733,6 @@ describe "Editor", ->
         editor.setHorizontalScrollbarHeight(0)
         editor.setHeight(5.5 * 10)
         editor.setWidth(5.5 * 10)
-        editor.displayBuffer.updateAllScreenLines()
 
       it "scrolls down when the last cursor gets closer than ::verticalScrollMargin to the bottom of the editor", ->
         expect(editor.getScrollTop()).toBe 0
@@ -1197,7 +1196,6 @@ describe "Editor", ->
           editor.setHeight(50)
           editor.setWidth(50)
           editor.setHorizontalScrollbarHeight(0)
-          editor.displayBuffer.updateAllScreenLines()
 
           expect(editor.getScrollTop()).toBe 0
 
@@ -1233,7 +1231,6 @@ describe "Editor", ->
         editor.setDefaultCharWidth(10)
         editor.setHeight(50)
         editor.setWidth(50)
-        editor.displayBuffer.updateAllScreenLines()
 
         editor.addSelectionForBufferRange([[8, 10], [8, 15]])
         expect(editor.getScrollTop()).toBe 75

src/display-buffer.coffee

@@ -208,7 +208,11 @@ class DisplayBuffer extends Model
   setLineHeightInPixels: (@lineHeightInPixels) -> @lineHeightInPixels
 
   getDefaultCharWidth: -> @defaultCharWidth
-  setDefaultCharWidth: (@defaultCharWidth) -> @defaultCharWidth
+  setDefaultCharWidth: (defaultCharWidth) ->
+    if defaultCharWidth isnt @defaultCharWidth
+      @defaultCharWidth = defaultCharWidth
+      @computeScrollWidth()
+    defaultCharWidth
 
   getCursorWidth: -> 1
 
@@ -981,9 +985,6 @@ class DisplayBuffer extends Model
     @rowMap.spliceRegions(startBufferRow, endBufferRow - startBufferRow, regions)
     @findMaxLineLength(startScreenRow, endScreenRow, screenLines)
 
-    if startBufferRow <= @longestScreenRow < endScreenRow
-      @computeScrollWidth()
-
     return if options.suppressChangeEvent
 
     changeEvent =
@@ -1045,6 +1046,8 @@ class DisplayBuffer extends Model
     {screenLines, regions}
 
   findMaxLineLength: (startScreenRow, endScreenRow, newScreenLines) ->
+    oldMaxLineLength = @maxLineLength
+
     if startScreenRow <= @longestScreenRow < endScreenRow
       @longestScreenRow = 0
       @maxLineLength = 0
@@ -1060,7 +1063,7 @@ class DisplayBuffer extends Model
         @longestScreenRow = maxLengthCandidatesStartRow + screenRow
         @maxLineLength = length
 
-    return
+    @computeScrollWidth() if oldMaxLineLength isnt @maxLineLength
 
   computeScrollWidth: ->
     @scrollWidth = @pixelPositionForScreenPosition([@longestScreenRow, @maxLineLength]).left + 1