port to SDL3

[notimaginative]

Basic port from SDL2 to SDL3. Also updates imgui to 1.92.5.

[notimaginative]

This is the basic port, and other SDL3-related feature PRs will come after this is merged.

One notable issue is that setting of gamma needs to be done by shaders as the gamma feature was removed from SDL3. Someone with a much better understanding of the current graphics code, and shaders in particular, should probably take care of that.

[wookieejedi]

@BMagnu is the Gamma shader aspect mentioned above something that you would be willing to comment on?

[wookieejedi]

If I start in windowed mode, then switch to fullscreen mode the screen flickers. It contines to flicker if in fullscreen mode upon game restart as well. This does not happen via windowed mode, so it is likely that the SDL 3 PR inadvertently reverted a bug fix we have in master for this screen flickering
Possibly to PR #6767 or related ones

[notimaginative]

If I start in windowed mode, then switch to fullscreen mode the screen flickers. It contines to flicker if in fullscreen mode upon game restart as well. This does not happen via windowed mode, so it is likely that the SDL 3 PR inadvertently reverted a bug fix we have in master for this screen flickering Possibly to PR #6767 or related ones

I don't remember seeing this, but I rarely use fullscreen mode. Or it simply might not happen on Mac. I'll check it out when I get the chance.

PR #6767 is still in there however, and wasn't altered for the port.

[wookieejedi]

Oh indeed, hmm yeah it's odd. At the very least it is always reproducible for me, so happy to do any local testing on Windows as we might need.

[notimaginative]

Squashed in fixes for the fullscreen bug as well as disabling the changing of display resolution at runtime. Both commits are available individually as part of #6735 for anyone that would like to see them without all the rest of the changes.