"Of course they are retained! What's the point of doing anything else? If you need to ask application restore them then you can as well ask application start from save point. ... If application developer can not handle save/restore events correctly then why do you think s/he'll be able to handle "drop shadow buffers"/"restore shadow buffers" events correctly?"
The apps must have the ability to recompute those pixmaps whenever, or they wouldn't have been drawn in the first place. Plus the pixmap state is not sufficient for application restore anyway, and would be in addition to whatever other state is saved/restored. The question is whether apps or the OS treat those pixmaps at a save/restore as a disposable cache, thus saving memory.
Recall that we were originally discussing whether ordinary unix concepts like multitasking, expose events, are really so inapplicable here. Stopped application state could be swapped by the OS instead of by the app. If pixmaps form such a core element of this platform, then specially handling them (disposing them also in the compositor/OS) seems workable. If not, I'd like to understand why.