Highlight the line number of the current cursor row

spec/app/editor-spec.coffee

@@ -1576,6 +1576,19 @@ describe "Editor", ->
         expect(miniEditor.gutter).toBeHidden()
         expect(miniEditor.scrollView.css('left')).toBe '0px'
 
+    it "highlights the line where the initial cursor position is", ->
+      { row, column } = editor.getCursorBufferPosition()
+      expect(row).toBe 0
+      expect(editor.find('.line-number.cursor-line-number').length).toBe 1
+      expect(editor.find('.line-number.cursor-line-number').text()).toBe "1"
+
+    it "updates the highlighted line when the cursor position changes", ->
+      editor.setCursorBufferPosition([1,0])
+      { row, column } = editor.getCursorBufferPosition()
+      expect(row).toBe 1
+      expect(editor.find('.line-number.cursor-line-number').length).toBe 1
+      expect(editor.find('.line-number.cursor-line-number').text()).toBe "2"
+
   describe "folding", ->
     beforeEach ->
       editSession = rootView.project.buildEditSessionForPath('two-hundred.txt')

src/app/gutter.coffee

@@ -9,10 +9,16 @@ class Gutter extends View
     @div class: 'gutter', =>
       @div outlet: 'lineNumbers', class: 'line-numbers'
 
+  cursorRow: -1
+
+  afterAttach: (onDom) ->
+    @editor()?.on 'cursor-move', => @highlightCursorLine()
+
   editor: ->
     @parentView
 
   renderLineNumbers: (startScreenRow, endScreenRow) ->
+    @firstScreenRow = startScreenRow
     lastScreenRow = -1
     rows = @editor().bufferRowsForScreenRows(startScreenRow, endScreenRow)
 
@@ -22,6 +28,7 @@ class Gutter extends View
         lastScreenRow = row
 
     @calculateWidth()
+    @highlightCursorLine()
 
   calculateWidth: ->
     width = @editor().getLineCount().toString().length * @editor().charWidth
@@ -29,3 +36,12 @@ class Gutter extends View
       @cachedWidth = width
       @lineNumbers.width(width)
       @widthChanged?(@outerWidth())
+
+  highlightCursorLine: ->
+    return if @firstScreenRow < 0
+
+    newCursorRow = @editor().getCursorBufferPosition().row - @firstScreenRow
+    if newCursorRow isnt cursorRow
+      cursorRow = newCursorRow
+      @find('.line-number.cursor-line-number').removeClass('cursor-line-number')
+      @find(".line-number:eq(#{cursorRow})").addClass('cursor-line-number')

static/editor.css

@@ -26,6 +26,10 @@
   position: relative;
 }
 
+.line-number.cursor-line-number {
+  color: rgba(255, 255, 255, .6);
+}
+
 .editor.mini .gutter {
   display: none;
 }