 
     @redrawHighlights()
 
+    # Return `key`, so that the caller can
+    # remove the line mark later with unmark(key)
     return key
 
   Editor::unmark = (key) ->

    if head.type is 'newline'
      return false

    key = @markedBlockKey++

    @markedBlocks[key] = {

        path = @getHighlightPath info.model, info.style
        path.draw @highlightCtx
      else
        delete @markedLines[id]

    for id, info of @extraMarks
      if @inTree info.model
