function makeBtn(position, iconPath, onclick, willRotate) {
	                if (!position) {
	                    return;
	                }
	                var opt = {
	                    position: position,
	                    origin: [controlSize / 2, 0],
	                    rotation: willRotate ? -rotation : 0,
	                    rectHover: true,
	                    style: itemStyle,
	                    onclick: onclick
	                };
	                var btn = makeIcon(timelineModel, iconPath, rect, opt);
	                group.add(btn);
	                graphic.setHoverStyle(btn, hoverStyle);
	            }
If label is ignored.
Automatically used when axis is category and label can not be all shown
@public
@param  {number} idx
@return {boolean}