Re: Cullng drawing depending on visibility events

[Keith Packard <keithp keithp com>]

Around 11 o'clock on Apr 4, Owen Taylor wrote:

> If a window can be reported as fully obscured but still 
> maintained in  backing store, that's sort of a mess ... you 
> really want to have  a way of keeping track of the "interest" 
> of the server in the contents of the window.

Visibility only reports whether portions of the window are not covered by 
other windows.  The server is free (and some do) to maintain contents of 
the window wherever it pleases.

> If VisibilityNotify doesn't indicate interest, then the
> algorithm has to be somewhat different; you have to keep
> maintaining the invalid region while the window is obscured,
> and when it becomes unobscured, generate repaints based
> on the invalid region.

Yes, that would likely work if the window wasn't changed while obscured.

-keith