Undesirable caching of Mouse/Key events in internet browser(s)

Please correct me if I'm wrong, but I want to be sure that isn't possible to cache mouse/key events to thin client embeded in internet browser(s), that any mouse/key event isn't stored in some queue and isn't possible to simulating/execute a.m. event before sceen/page is fully repainted,

• lets start with model situation e.g. any active item from current screen will executes a new screen, an have to caclulating with some repaints delay, without old a new page on monitor, and during this processes I'm able/cabalable to execute plenty of mouse/key events.

• is there/are there some method, settings, signal that (which I am able to test) that a new page is fully repainted and only from this moment page to consume mouse/key event,

• or during repaint processes a mouse/key event is cached and will be executed after repainting to new page (sure so close to hijack, then I'm able to simulating mouse click to x-y coordinates)