code: function clipRect(x, y, width, height) {
           var canvas = this.backBufferCanvas; // if requested box is different from the current canvas size;
  
           if (x !== 0 || y !== 0 || width !== canvas.width || height !== canvas.height) {
             var currentScissor = this.currentScissor; // if different from the current scissor box
  
             if (currentScissor[0] !== x || currentScissor[1] !== y || currentScissor[2] !== width || currentScissor[3] !== height) {
               var context = this.backBufferContext2D;
               context.beginPath();
               context.rect(x, y, width, height);
               context.clip(); // save the new currentScissor box
  
               currentScissor[0] = x;
               currentScissor[1] = y;
               currentScissor[2] = width;
               currentScissor[3] = height;
             }
           }
         }
docs: clip the given region from the original canvas. Once a region is clipped,
  all future drawing will be limited to the clipped region.
  You can however save the current region using the save(),
  and restore it (with the restore() method) any time in the future.
  (<u>this is an experimental feature !</u>)
  @name clipRect
  @memberOf me.CanvasRenderer.prototype
  @function
  @param {Number} x
  @param {Number} y
  @param {Number} width
  @param {Number} height