[center, r, startRadian, endRadian, counterclockwise]
[center, r]
{ stop: 介于 0.0 与 1.0 之间的值,表示渐变中开始与结束之间的位置 color: 在结束位置显示的 CSS 颜色值 }
direction string.
[p1, p2]
[x, y, width, height]
[text, point, maxWidth]
[p1, p2, p3]
[center, r, startRadian, endRadian, counterclockwise]