Then use the lineTo API to draw a line from the start point to the end point passed in to the lineTo call.
然后使用lineTo API来从这个起始点到传递到这个lineTo调用中的端点之间绘制一条直线。
2
After drawing both axes, you draw the gridlines along with their labels by evenly spacing them and then drawing the lines using the same combination of moveTo, lineTo, and stroke.