SCUMM: Zak McKracken (FM-Towns) shows no graphics in windowed mode (OpenGL/RGB555)

[angstsmurf]

Unlike #9945 and #9946, this happens in the nighly builds using SDL 1.2.14 as well: when using OpenGL graphics windowed mode, Zak McKracken FM Towns version (the one available from GOG) will only show a black screen, though the sound is working. Fullscreen works fine.

ScummVM 1.10.0git3962-g850dcdbdf8 and MacOS Sierra 10.12.5, on a Retina MacBook
Pro, 15 inch, mid 2014.

[angstsmurf]

I just tested this again with the latest build and SDL2 2-0-6, and now the screen is black when starting in fullscreen as well. Still works fine with any non-OpenGL mode.

[csnover]

Does this happen with any other game, or is it only the FM Towns Zak McKracken?

[angstsmurf]

It happens in FM Towns Loom as well. I'll keep checking.

EDIT: And now it happens in full screen mode as well.

[angstsmurf]

… which means that the title should be changed, I suppose.

[csnover]

I’m not able to reproduce this issue on rMBP mid-2012, macOS 10.12.6, SDL 2.0.6, OpenGL mode, filtering on or off, using the discrete (Nvidia) GPU. Do any games render using OpenGL mode for you? Do they work if you switch between integrated/discrete GPU?

[angstsmurf]

I only have an integrated GPU (Intel Iris Pro) in this machine. Black screen on all Lucasarts FM Towns games in OpenGL mode, and only on those. Fine in all non-OpenGL modes.

[csnover]

Yes, but what about games that are not FM-Towns?

[angstsmurf]

All fine.

[angstsmurf]

Happens in official 1.9.0 build as well.

[csnover]

OK, so I guess what is probably happening here is that the GPU doesn’t support RGB555, which is the mode used by FM Towns. I’m unfamiliar with GPU programming so I’m not sure what options exist here yet to allow this to work (other than to convert in software, which is what SDL already does when you use the normal renderer). I’ll do some research when I have time, if someone else with the prerequisite knowledge doesn’t pipe in first with an answer.

[angstsmurf]

Thanks for looking into this! I'll just assume that I was mistaken all along about that "in windowed mode" part, it really makes no sense.

[ccawley2011]

Is this issue still present?

[angstsmurf]

I'm afraid I don't have access to that computer anymore, and my current one does support RGB555, but I suppose there are plenty of other computers out there using the same integrated GPU that could check this.

[angstsmurf]

And as mentioned above, this applies to all FM-Towns games, and not only in windowed mode, but in OpenGL, windowed or fullscreen, so the title is misleading. I don't know if other ScummVM games use RGB555, but if so, it applies to them too. The problem is with GPUs that don't support that mode.

[athrxx]

Is this still an issue or can we close it as outdated?