Handle editor font config options with a global stylesheet

Previously, each editor observed font-related config values on its own
and applied inline styles to honor them. This made it difficult to style
the editor like a normal element with CSS.

Moving this to a global stylesheet that targets editors via the .editor
selector means that the font size setting can be overridden in specific
contexts, such as when using mini editors.

src/editor-component.coffee

@@ -513,9 +513,6 @@ EditorComponent = React.createClass
       parentView.command command, listener
 
   observeConfig: ->
-    @subscribe atom.config.observe 'editor.fontFamily', @setFontFamily
-    @subscribe atom.config.observe 'editor.fontSize', @setFontSize
-    @subscribe atom.config.observe 'editor.lineHeight', @setLineHeight
     @subscribe atom.config.observe 'editor.showIndentGuide', @setShowIndentGuide
     @subscribe atom.config.observe 'editor.invisibles', @setInvisibles
     @subscribe atom.config.observe 'editor.showInvisibles', @setShowInvisibles

src/workspace-view.coffee

@@ -96,6 +96,11 @@ class WorkspaceView extends View
         when 'overlay'
           @addClass("scrollbars-visible-when-scrolling")
 
+
+    @subscribe atom.config.observe 'editor.fontSize', @setEditorFontSize
+    @subscribe atom.config.observe 'editor.fontFamily', @setEditorFontFamily
+    @subscribe atom.config.observe 'editor.lineHeight', @setEditorLineHeight
+
     @updateTitle()
 
     @on 'focus', (e) => @handleFocus(e)
@@ -340,6 +345,24 @@ class WorkspaceView extends View
   beforeRemove: ->
     @model.destroy()
 
+  setEditorFontSize: (fontSize) =>
+    @setEditorStyle('font-size', fontSize + 'px')
+
+  setEditorFontFamily: (fontFamily) =>
+    @setEditorStyle('font-family', fontFamily)
+
+  setEditorLineHeight: (lineHeight) =>
+    @setEditorStyle('line-height', lineHeight)
+
+  setEditorStyle: (property, value) ->
+    unless styleNode = atom.themes.stylesheetElementForId('global-editor-styles')[0]
+      atom.themes.applyStylesheet('global-editor-styles', '.editor {}')
+      styleNode = atom.themes.stylesheetElementForId('global-editor-styles')[0]
+
+    editorRule = styleNode.sheet.cssRules[0]
+    editorRule.style[property] = value
+    atom.themes.emit 'stylesheets-changed'
+
   # Deprecated
   eachPane: (callback) ->
     deprecate("Use WorkspaceView::eachPaneView instead")