Never redraw when the font size changes on a detached editor

When the font size changes and the editor is detached, it schedules
itself to be redrawn the next time we're reattached rather than
updating the display in a detached state.

Detached display updates worked in the past because we didn't need to
be on the DOM to determine horizontal and vertical positions once we
had calculated dimensions once. So it worked to temporarily attach
the editor when calculating new dimensions, and then continue updates
even when it was detached. That now breaks because we can't ask for
pixel positions if we aren't on the DOM.

spec/app/editor-spec.coffee

@@ -633,7 +633,7 @@ describe "Editor", ->
         expect(editor.renderedLines.find(".line").length).toBeGreaterThan originalLineCount
 
       describe "when the editor is detached", ->
-        it "updates the font-size correctly and recalculates the dimensions by placing the rendered lines on the DOM", ->
+        it "redraws the editor according to the new font size when it is reattached", ->
           rootView.attachToDom()
           rootView.height(200)
           rootView.width(200)

src/app/editor.coffee

@@ -55,6 +55,7 @@ class Editor extends View
   pendingChanges: null
   newCursors: null
   newSelections: null
+  redrawOnReattach: false
 
   @deserialize: (state, rootView) ->
     editor = new Editor(mini: state.mini, deserializing: true)
@@ -447,7 +448,9 @@ class Editor extends View
       @syncCursorAnimations()
 
   afterAttach: (onDom) ->
-    return if @attached or not onDom
+    return unless onDom
+    @redraw() if @redrawOnReattach
+    return if @attached
     @attached = true
     @calculateDimensions()
     @hiddenInput.width(@charWidth)
@@ -726,7 +729,12 @@ class Editor extends View
       headTag.append styleTag
 
     styleTag.text(".editor {font-size: #{fontSize}px}")
-    @redraw()
+
+    if @isOnDom()
+      @redraw()
+    else
+      @redrawOnReattach = true
+
 
   getFontSize: ->
     parseInt(@css("font-size"))
@@ -745,7 +753,9 @@ class Editor extends View
   getFontFamily: -> @css("font-family")
 
   redraw: ->
+    return unless @hasParent()
     return unless @attached
+    @redrawOnReattach = false
     @calculateDimensions()
     @updatePaddingOfRenderedLines()
     @updateLayerDimensions()
@@ -842,10 +852,6 @@ class Editor extends View
     @overlayer.append(view)
 
   calculateDimensions: ->
-    if not @isOnDom()
-      detachedEditorParent = _.last(@parents()) ? this
-      $(document.body).append(detachedEditorParent)
-
     fragment = $('<pre class="line" style="position: absolute; visibility: hidden;"><span>x</span></div>')
     @renderedLines.append(fragment)
 
@@ -857,8 +863,6 @@ class Editor extends View
     @height(@lineHeight) if @mini
     fragment.remove()
 
-    $(detachedEditorParent).detach()
-
   updateLayerDimensions: ->
     @gutter.calculateWidth()