     else if axis - @scrollOffsets.main.y > @mainCanvas.height
       @mainScroller.scrollTop = axis - @mainCanvas.height
 
+    @mainScroller.scrollLeft = 0
+
   # Pressing the up-arrow moves the cursor up.
   hook 'key.up', 0, ->
     @clearLassoSelection()

    @aceEditor.getSession().setTabSize 2

    @aceEditor.on 'change', =>
      unless @suppressChangeEvent
        @setFontSize_raw @aceEditor.getFontSize()
        @gutter.style.width = @aceEditor.renderer.$gutterLayer.gutterWidth + 'px'
        @resize()

    @currentlyUsingBlocks = true
    @currentlyAnimating = false

      # anything non-local, only redraw locally.
      if deepEquals newp, oldp
        rect = new draw.NoRectangle()

        rect.unite treeView.bounds[line - 1] if line > 0
        rect.unite treeView.bounds[line]
        rect.unite treeView.bounds[line + 1] if line + 1 < treeView.bounds.length

        rect.width = Math.max rect.width, @mainCanvas.width


        @redrawMain
          boundingRectangle: rect
