Missing check to handle `SetSwapchainParameters` failure when setting mailbox/immediate

[Demorome]

Context: libsdl-org/SDL#12837
If I'm reading this issue correctly, it's possible that a setup supports Mailbox present mode, but not necessarily with SDR swapchain composition, notably with the Steam Deck.

Therefore, I believe a check for SDR swapchain composition support (when we're switching away from VSYNC) is missing, to prevent runtime errors to better handle a failure to set the present mode.

MoonWorks/src/Game.cs

Line 211 in 0b28ffe

if (GraphicsDevice.SupportsPresentMode(MainWindow, PresentMode.Mailbox))

MoonWorks/src/Game.cs

Line 213 in 0b28ffe

GraphicsDevice.SetSwapchainParameters(MainWindow, SwapchainComposition.SDR, PresentMode.Mailbox);

[thatcosmonaut]

SDR is always supported, so checking it via the Supports query is pointless. Instead you would want to try setting mailbox/SDR and then fall back if it fails.

[Demorome]

Ah, this SDL_GPU docstring somewhat implied that only the combination of the SDR + VSYNC was always valid:

SDL_GPU_PRESENTMODE_VSYNC with SDL_GPU_SWAPCHAINCOMPOSITION_SDR is always supported.

I see now that it's referring specifically to VSYNC, as in VSYNC + SDR will always work but not VSYNC + HDR etc. ; I needed to have also read https://wiki.libsdl.org/SDL3/SDL_GPUSwapchainComposition describing that SDR is always supported (no matter the present mode). My bad.

[Demorome]

Made a PR for this: #38