Re: [gtk-list] Re: GraphicsExpose (was Re: About the About Box)

[Owen Taylor <owt1 cornell edu>]

Raph Levien <raph@acm.org> writes:
>
> On Sun, 14 Dec 1997, Owen Taylor wrote:
> 
> > After the XCopyArea call, X thinks that the entire window now contains
> > valid information (for the purpose of calculating GraphicsExpose
> > events). But actually, that isn't true until the GraphicsExpose events
> > filter through the queue. Before then, X has blanked out the improper
> > areas to the background color (*) If another motion event occurs
> > before then, X will copy the blanked out areas, but not produce
> > graphics expose events for them, thus leading to the observed gray
> > bars. 
> 
> I had another thought on this and wanted to throw it out there. Since 
> this is at heart a race condition caused by asynchronous GraphicsExpose 
> events following XCopyArea, wouldn't the problem be fixed by doing an 
> XSync right before the scroll? I can't imagine the performance 
> degradation would be that serious, and it sounds a whole lot simpler 
> than some of the other proposals.

I don't think this will help. XSync (or gdk_flush()) only affect
the output queue. Since the problem is GraphicsExpose events sitting
in the input queue, the only way to fix it is to process those events
before doing the XCopyArea.

Regards,
                                        Owen