8.3 Clipping

Clipping is used in graphics system to restrict the area in which graphics operations have effect. For instance, when some part of a window is damaged, the application can clip to the damaged part and then draw the whole window. The result of the clipping is that the system ignores the drawing request outside the clipping area, and the speed of updating is increased significantly.

The canvas supports clipping in the situation where some of the graphical objects are totally or partly outside the visible shape of the canvas. The canvas always clips to the visible shape. In addition to this clipping area it is possible to set another clipping area, also defined by a shape - the clip shape. SetClip and GetClip can be used to set and get the clip shape. The clip shape is especially useful when damaged areas must be updated, see the next section.