jpx_composition::get_last_persistent_frame

Returns a reference to the most recent frame, preceding that referenced by the opaque frame_ref pointer, which is marked as persistent. By following last persistent frame links, it is possible to walk backwards through the list of frames which must notionally be composed onto the composition surface prior to the current frame. Invoking get_frame_info one each of these frames will cause the supplied is_persistent argument to be set to true.

This function enables dynamic renderers such as that embodied by kdu_region_compositor to efficiently scan through the compositing dependencies, stopping as soon as it encounters a complete opaque background.

frame_ref [jx_frame *]