     @_$highlightsLayer = @_$textLayer.prev('.highlights-layer')
     @_highlightsCanvas = @_$highlightsLayer.prev('.highlights-canvas').get(0)
 
+    @_area = null
     @_hover = null
     @_$highlight = null
 
     @_createHighlight()
+
+  _computeArea: (segments) =>
+    @_area = 0
+
+    for segment in segments
+      @_area += segment.width * segment.height
+
+    return # Don't return the result of the for loop
 
   _precomputeHover: (segments) =>
     # For now compute simply a bounding box

    context = @_highlightsCanvas.getContext('2d')
    context.clearRect 0, 0, @_highlightsCanvas.width, @_highlightsCanvas.height

  _createHighlight: =>
    scrollLeft = $(window).scrollLeft()
    scrollTop = $(window).scrollTop()

      width: rect.width
      height: rect.height

    @_computeArea segments
    @_precomputeHover segments

    @_$highlight = $('<div/>').addClass('highlights-layer-highlight').append(
