Morten Eriksen (Morten.Eriksen++at++due.unit.no)
Tue, 19 Nov 1996 08:07:59 +0100 (MET)
I hope you can forgive me that I'm about to use the mailing list to
ask a OpenGL-specific question (the comp.graphics.api.opengl newsgroup
is all cluttered up with religious wars at the moment...).
I've been fiddling with glReadPixels() to make it read from a
GLwMDrawingArea widget and put the captured data into my allocated
memory area. My problem is that pixels which are obscured by other
windows overlapping the drawingarea widget becomes filled with
garbage. I thought this was due to some silly bug on my behalf; like
not setting the viewport correctly, forgetting to set the "saveUnder"
flag or the buffer needing a flush or XSync or something, but nothing
seemed to help. Then I checked with perfly - and the same behavior
appeared when saving snapshots of the simulation.
So.. is it impossible to extract all the areas of pixeldata from a
drawingarea widget when it's window is partly obscured? Do I need to
use an off-screen pixmap or something? Or is there some simpler
solution (or even a quick hack :) )?
Any help on the subject would be much appreciated.
Morten
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