Depending on the state of the program, a mouse down might start drawing a line, or it might select an object.

根据程序的状态，鼠标按下事件，应该开始绘制一条直线，或者选中一个对象。

youdao

Depending on the state of the program, a mouse down might start drawing a line, or it might select an object.

根据程序的状态，鼠标按下事件，应该开始绘制一条直线，或者选中一个对象。

youdao