Steam Deck. Setting MAILBOX with SDL_GPU_SWAPCHAINCOMPOSITION_SDR returns composition not supported

[mshvern]

I set the present mode on Steam Deck approximately the following way.

        if (SDL_WindowSupportsGPUPresentMode(
            gpu.device,
            gpu.window,
            SDL_GPU_PRESENTMODE_MAILBOX)) {

            LOG_SDL_ERROR(SDL_SetGPUSwapchainParameters(
                gpu.device,
                gpu.window,
                SDL_GPU_SWAPCHAINCOMPOSITION_SDR,
                SDL_GPU_PRESENTMODE_MAILBOX), "setting mailbox");
        }

From documentation:

• SDL_GPU_PRESENTMODE_VSYNC and SDL_GPU_SWAPCHAINCOMPOSITION_SDR are always supported.

Which is why I only check present mode, which returns OK.

[mshvern]

OK this is 100% the issue.

Docstring is contradicted by behavior of the emulated DirectX backend on Steam Deck

My current "fix."

if (!SDL_WindowSupportsGPUSwapchainComposition(gpu.device, gpu.window, SDL_GPU_SWAPCHAINCOMPOSITION_SDR)) {
        append_to_log("Cannot do anything to vsync, probably running on steam deck?");
        return;
    }

Am I reading this wrong and does the docstring mean that setting both at the same time is always supported?

[thatcosmonaut]

Should probably say SDL_GPU_PRESENTMODE_VSYNC with SDL_GPU_SWAPCHAINCOMPOSITION_SDR is always supported.

[slouken]

The documentation is fixed in 695cad4, is that all that needs to be done here?