Make react cursor the width of a default character at the end of lines

When the cursor is positioned before a character, we always make it the
width of that character. But at the end of a line, there is no character
to use to set the width, so we just use the defaultCharWidth.

This makes the block cursor visible on empty lines in vim-mode.

spec/editor-component-spec.coffee

@@ -630,6 +630,11 @@ describe "EditorComponent", ->
       expect(cursorRect.left).toBe rangeRect.left
       expect(cursorRect.width).toBe rangeRect.width
 
+    it "sets the cursor to the default character width at the end of a line", ->
+      editor.setCursorScreenPosition([0, Infinity])
+      cursorNode = node.querySelector('.cursor')
+      expect(cursorNode.offsetWidth).toBe charWidth
+
     it "gives the cursor a non-zero width even if it's inside atomic tokens", ->
       editor.setCursorScreenPosition([1, 0])
       cursorNode = node.querySelector('.cursor')

src/cursor-component.coffee

@@ -6,10 +6,11 @@ CursorComponent = React.createClass
   displayName: 'CursorComponent'
 
   render: ->
-    {editor, screenRange, scrollTop, scrollLeft} = @props
+    {editor, screenRange, scrollTop, scrollLeft, defaultCharWidth} = @props
     {top, left, height, width} = editor.pixelRectForScreenRange(screenRange)
     top -= scrollTop
     left -= scrollLeft
+    width = defaultCharWidth if width is 0
     WebkitTransform = "translate3d(#{left}px, #{top}px, 0px)"
 
     div className: 'cursor', style: {height, width, WebkitTransform}

src/cursors-component.coffee

@@ -12,7 +12,7 @@ CursorsComponent = React.createClass
   cursorBlinkIntervalHandle: null
 
   render: ->
-    {editor, cursorScreenRanges, scrollTop, scrollLeft} = @props
+    {editor, cursorScreenRanges, scrollTop, scrollLeft, defaultCharWidth} = @props
     {blinkOff} = @state
 
     className = 'cursors'
@@ -21,7 +21,7 @@ CursorsComponent = React.createClass
     div {className},
       if @isMounted()
         for key, screenRange of cursorScreenRanges
-          CursorComponent({key, editor, screenRange, scrollTop, scrollLeft})
+          CursorComponent({key, editor, screenRange, scrollTop, scrollLeft, defaultCharWidth})
 
   getInitialState: ->
     blinkOff: false