[Vm-dev] Differences in OpenGL support on Linux vs. OS X?

Bert Freudenberg bert at freudenbergs.de
Sat Jun 9 16:04:38 UTC 2012

On 2012-06-09, at 16:59, Hans-Martin Mosner wrote:

> Am 06.06.2012 18:15, schrieb Phil (list):
>> I'm having some problems with code that was previously working that I've narrowed down to what I believe is a difference in platform behavior and could use some help.  The issue is that when I draw single frames in OpenGL, things work as expected on both platforms.  However, when I try to do some simple animation via Morphic stepping, it works as expected on the Mac (i.e. smooth animation at a decent framerate) but on Linux there seems to be an issue where the frame gets drawn by OpenGL then immediately drawn over with the background color so it's essentially doubling the redraw rate and looking terrible to boot.  I'm assuming (possibly incorrectly) that this is purely a VM/plugin issue as I'm using the same image file on both platforms.
>> The VM I'm running is from http://www.mirandabanda.org/files/Cog/VM/VM.r2550/  (i.e. the Mac and Linux versions)
>> Any ideas?
>> Thanks,
>> Phil
> This is caused by an (IMO incorrect) setting in the code that creates the X drawing context in sqUnixX11.c:
> gcValues.subwindow_mode= IncludeInferiors;
> This allows X to draw over subwindows of the main window, which is generally a bad idea.
> I have changed that to ClipChildren with the desired effect.
> I also notified Ian Piumarta of this, but as of now there has not been an official change to this file.
> On my system, I currently do not have a working VMMaker setup, so I just binary patched the vm-display-X11 plugin and
> have 3D as it is meant to be :-)

Ah. Sounds like a good idea to remind him :)

- Bert -

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