Bounds 应该应用于此实例的边界（已对实例应用所有必要的修改）。
在控制手柄被拖到场景中时使用的回调。
This method ensures that the radius axes scale uniformly and that the height and radius parameters cannot fall outside their acceptable ranges relative to one another.
The height control handles cannot be made smaller than the diameter. Enlarging the diameter handles automatically increases the height if needed. The height value at the time the control was clicked is preferred until the user releases the control handle.