AllegroGL bug on OSX with ATI Radeon 9200

AllegroGL acts up on the mac mini's internal ATI Radeon 9200 w. 32 ram. Im not sure why exactly, It worked fine on the other mac with the ATI Rage 128.

ALL of the example programs, including my game experience tons of graphical artifacts from the desktop and there is LOTS of flickering. This isnt good.

Ive tested the following versions so far:
Allegro 4.2 beta 2 w/ AllegroGL latest CVS
Allegro 4.1.15 w/ AllegroGL CVS from a few months ago (sorry I cannot specify an exact version, but iirc the cvs isnt marked. Please correct me if I am wrong.)

Both work on the Rage 128 but not the 9200 (which experiences severe artifacts).

None of the artifacts appear in any other programs except for the allegrogl ones :( So im pretty sure its a problem with allegrogl


What graphics mode and color depth do the examples use? From my experience (non AGL) certain modes combined with certain color depths are impossible for my PowerBook to do. Allegro will return an error. Maybe AGL does not or it thinks it can but it really can't.

The only suggestion I can give is to play around with these combinations. I haven't played around much with AGL on OSX.


My ibook had the same problem. It wouldnt do certain depths and resolutions

But this is a different case, every mode/res/depth I try acts the same (lots of scrambled, flashing desktop artifacts) :(

Peter Hull

I found some bugs in the OS X code in Allegro GL, and I posted a fix as a patch on the SourceForge page.
I'm waiting for Bob to comment on these (Bob rules!) but in the meantime, maybe you could try it and see if it fixes any problems that you've been having.

OpenGL is pretty simple under Cocoa - you just need to make a Window's view (a subclass of) NSOpenGLView, and then make its context the active one. I noticed that single buffered OpenGL contexts seem to be updated immediately (no waiting for glFlush()) so, if you use single buffered, the image is very flickery. The example program 'test' does this, IIRC.

Hope this helps,



I just tried out your patch peter. No change :(

Peter Hull

Well, I found some problems with my patch (the infamous 'invalid drawable' :P, Thomas Harte has seen it too...) so I'll work on a new better one and let you know. In the meantime, can you confirm that non-AllegroGL programs work OK, e.g. the samples in the /Developer directory?



I forgot to note that the buggy crap only happens when you go into any of the fullscreen modes. Nothing bugs if you keep it in windowed.

About testing the developer examples. None of them have the option for a fullscreen mode, and the problem is in fullscreen. :( Although I have been able to test with the GLFW examples and a few opengl games. And those all work fine in fullscreen. Whatever the problem is, its something specific to allegrogl.

The desktop artifacts only show while allegrogl is totally in control of the blitting (ie they dont show while the os is fading the program black when quitting) The problem probably lies somewhere in the allegrogl mac fullscreen blitting routines.

Also I want to confirm that I am applying your patch correctly.
The command is patch < macosx.diff right?

Would it be worth waiting for a patch? It is a pretty simple fix isnt it? I really would like to help out but checking out the lib source files makes me think its a little out of the scope of my talents.

Peter Hull

Can you try this attached program?



IT WORKS!!! No artifacts! ;D;D;D

Thank you Peter! Could you please release the patch? :)

I gotta mow the lawn now. bbl

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