ctx.fillRect(0, 0, leftHandleCanvasPos, this.canvasRect_.h);
ctx.fillRect(rightHandleCanvasPos, 0, this.canvasRect_.w - rightHandleCanvasPos, this.canvasRect_.h);
ctx.fillRect(0, 0, leftHandleCanvasPos, this.canvasRect_.h);
ctx.fillRect(rightHandleCanvasPos, 0, this.canvasRect_.w - rightHandleCanvasPos, this.canvasRect_.h);