Always calculate dimensions with editor on DOM

Closes #206

spec/app/editor-spec.coffee

@@ -552,6 +552,7 @@ describe "Editor", ->
   describe "font size", ->
     beforeEach ->
       expect(editor.css('font-size')).not.toBe "20px"
+      expect(editor.css('font-size')).not.toBe "10px"
 
     it "sets the initial font size based on the value from config", ->
       expect($("head style.font-size")).toExist()
@@ -614,6 +615,23 @@ describe "Editor", ->
         config.set("editor.fontSize", 10)
         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", ->
+          rootView.attachToDom()
+          rootView.height(200)
+          rootView.width(200)
+
+          newEditor = editor.splitRight()
+          newEditorParent = newEditor.parent()
+          newEditor.detach()
+          config.set("editor.fontSize", 10)
+          newEditorParent.append(newEditor)
+
+          expect(newEditor.lineHeight).toBe editor.lineHeight
+          expect(newEditor.charWidth).toBe editor.charWidth
+          expect(newEditor.getCursorView().position()).toEqual editor.getCursorView().position()
+          expect(newEditor.verticalScrollbarContent.height()).toBe editor.verticalScrollbarContent.height()
+
   describe "mouse events", ->
     beforeEach ->
       editor.attachToDom()

src/app/editor.coffee

@@ -804,6 +804,10 @@ 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)
 
@@ -815,6 +819,8 @@ class Editor extends View
     @height(@lineHeight) if @mini
     fragment.remove()
 
+    $(detachedEditorParent).detach()
+
   updateLayerDimensions: ->
     @gutter.calculateWidth()
 

src/stdlib/jquery-extensions.coffee

@@ -25,6 +25,9 @@ $.fn.pageUp = ->
 $.fn.pageDown = ->
   @scrollTop(@scrollTop() + @height())
 
+$.fn.isOnDom = ->
+  @closest(document.body).length is 1
+
 $.fn.containsElement = (element) ->
   (element[0].compareDocumentPosition(this[0]) & 8) == 8