OSXPPC: OpenGL fullscreen glitches on old ATI Rage 128 cards

[dwatteau]

Creating this (self-assigned) here, so that I can keep track of it somewhere.

Back in March 2023, user '2Mourty' PM'd me about some "OpenGL garbled screen-problem" on OSXPPC (which I maintain).

Setup was:

• ScummVM 2.7.0 (most recent release back then)
• an ATI Rage Mobility 128 on an iBook G3 500 MHz, running OSX 10.4

Symptoms were:

• KO: "Multi-colored snow" would appear on their screen, when trying to play in fullscreen.
• OK: When switching from OpenGL (defaults) renderer to SDL renderer, there was no such problem.

I couldn't reproduce the issue on my 3 own PowerPC Macs, but I didn't have one with an ATI R128 card. And then I lost contact with this person.

But lately I've found a cheap iBook G3 with an ATI Rage Pro card. It's running OSX 10.3, so it's stuck with ScummVM v2.5.1 (no C++11 toolchain there). I'll see if I can upgrade it to OSX 10.4, later on.

But I see the same symptoms:

• ATI Rage 128 card
• KO: fullscreen OpenGL renderer is fully glitched (see screenshot), except for the cursor, which is still recognisable
• OK: fullscreen SDL 1.2 is fine, and OpenGL/SDL windowed mode is fine as well

It's a very old card. Maybe we could just revert to using SDL 1.2 as the default renderer when detecting OSX 10.4 at runtime (last OSX to support such old cards, it seems), but otherwise the default OpenGL renderer seems to have better FPS, at least on G3s.

[dwatteau]

OpenGL fullscreen output with v2.5.1 on ATI Rage Pro 128 card (with Monkey3 demo)

[dwatteau]

Self-assigning this. I'll probably need some time to bump this machine to OSX 10.4 so that I can do tests on current ScummVM (currently stuck on OSX 10.3 and thus C++98 v2.5.1).