You should be able to query GraphicsCapabilities.MaxMultiSampleCount in Game.Initialize() and apply graphics device parameters from there. Does that work?

DesktopGL comes with some limitation compared to WindowsDX in the fact that some graphics capabilities can be queried only after the Game constructor due to how SDL operates things under the hood. I'm a bit on the fence to create a fake window just to query that, I feel like it might introduce more issues in the long run that fixing this use case.

GraphicsCapabilities and GraphicsCapabilities.MaxMultiSampleCount are internal so it would require some code changes to expose this.

It also has to create a temporary window no matter what, because GL can't query the API without an active context, and the way MonoGame is consuming SDL and GL it requires creating an SDL window.

I think creating the full graphics device chain in managed memory is creating a lot more garbage and introducing more opportunities for bugs instead of just quickly creating and destroying an SDL window in a controlled manner and then creating the real window. This is also, to my understanding, standard practice when using SDL (and GL).

I also personally have a concern with the approach of exposing this to the end users and expecting them to deal with it because:

• MaxSamples value is not always reliable, it reports 32 on my desktop when in reality it only supports up to 16 -- my Steam Deck reports correctly. Ordinarily I would be against my own fix for this, but the PR is meant as a "best effort" to prevent a crash, and includes better messaging so the end-user doesn't have to dive into dependencies with a debugger to figure out the root cause. I think having a potentially incorrect value as the maximum acceptable for a best effort, but not acceptable for a public API.
• Seems weird to expect users to know to poll graphics capabilities and then set the value
• Correct me if I am wrong, but in DX this can be done in the constructor, so this is also a GL-specific issue. I think it goes against the spirit of MonoGame to expect users to understand the internals of MonoGame and its dependencies in order to properly fix this issue.

After reading the docs on this, I think we can handle this a different way (I could be wrong though).
We can leave the code to call SetAttribute as it is now since it is only a hint. If the OpenGL driver cannot handle it is will use the maximum value it can.
We should then use GetAttribute to query the actual value from the driver after the window has been created. Then update the presentationParameters.MultiSampleCount accordingly.

Something like

if (presentationParameters.MultiSampleCount > 0)
{
    Sdl.GL.SetAttribute(Sdl.GL.Attribute.MultiSampleBuffers, 1);
    Sdl.GL.SetAttribute(Sdl.GL.Attribute.MultiSampleSamples, presentationParameters.MultiSampleCount);
}
((SdlGameWindow)SdlGameWindow.Instance).CreateWindow();
Sdl.GL.GetAttribute (Sdl.GL.Attribute.MultiSampleSamples, out int samples);
presentationParameters.MultiSampleCount = samples;

See https://wiki.libsdl.org/SDL2/SDL_GL_GetAttribute

it will use the maximum value it can

We need to verify that it actually does that. But if it does without error, it seems relevant.

If the OpenGL driver cannot handle it is will use the maximum value it can.

Unfortunately the GL driver doesn't intelligently do this, and that causes the crash that this PR is meant to prevent.

We can leave the code to call SetAttribute as it is now since it is only a hint.

It may be called a hint, but it's not treated as something optional. The SetAttribute() call with an invalid GL_SAMPLES value will cause the context creation that happens after it to fail. GL_SAMPLES (abstracted as SDL_GL_MULTISAMPLESAMPLES) must be set to a value supported by the driver before context creation, and changing it requires re-creating the context.

Sdl.GL.GetAttribute() would call glGetIntegerv() which cannot be used without a current valid GL context, which will fail to be created if GL_MAX_SAMPLES is set too high. The hidden dummy window being created would have the default GL_MAX_SAMPLES value of 0 which would allow it to be safely created in order to poll the GL_MAX_SAMPLES value in order to limit it.

Note that SDL2 does not expose GL_MAX_SAMPLES via SDL_GL_GetAttribute(), GL must be queried directly.