Dynamic segments are graphics segments that can be moved from where they were drawn on the screen to a different coordinate position, or altered in some other way, without affecting the remaining part of the picture. The new position of a dynamic segment can be provided with an input device, such as a mouse, or it can be application-generated.
The dynamic attribute is set to OFF by default. The setting is always inherited by called segments from the setting of their callers. If a calling segment is nondynamic, any segments called by it are also nondynamic, regardless of how they have been defined. If the calling segment is dynamic, all segments called by it are also dynamic. Any segment explicitly defined as dynamic must have a unique name, and it cannot be created when the current drawing-mode parameter is DM_DRAW or DM_DRAWANDRETAIN. Although no error condition is raised if you define an unchained segment as dynamic, it is not treated as dynamic unless the segment is called from a dynamic root segment.
Graphics objects to be moved without disturbing the remaining contents of the display are drawn in exclusive-OR mode. Segments that you define as dynamic always are drawn in exclusive-OR mode, regardless of the current mix attribute settings and any GpiSetMix functions the segment itself might contain.
For performance reasons, dynamic segments are to be grouped at the start of the picture chain. There are GPI functions that handle dynamic segments as a group, so it is more efficient if the entire segment chain does not have to be scanned to locate them.
When the entire picture chain is drawn, however, dynamic segments are to be drawn after all other segments in the chain to ensure that the effects of drawing in exclusive-OR mode are not adversely affected by drawings in other mix modes. Also, you must ensure that no nondynamic drawing overlays the dynamic segments after they have been drawn. The PM ensures that dynamic segments are always drawn on top of other graphics.