FPS limit not works in Windows

[1vanK]

In Windows when SDL_SetHint(SDL_HINT_MAIN_CALLBACK_RATE, "30") and user drag app window (or just hold LMB on title) fps is 60-65

[playmer]

This is pretty interesting. There's two ways your callback gets called during move/resize operations on Windows, as far I can tell.

• You're called by a WM_TIMER SDL sets up when you enter one of these situations. This is unconditionally set to USER_TIMER_MINIMUM, which seems to request being called once every 10ms. In the timer SDL calls SDL_IterateMainCallbacks which calls your function.
• You get a WM_PAINT event, which sends an SDL_EVENT_WINDOW_EXPOSED, which in turn calls SDL_IterateMainCallbacks.

So the easy first thing might be to change the USER_TIMER_MINIMUM to be the callback rate, unsure how changes should be handled, maybe a callback on hint change like in the generic/SDL_sysmain_callbacks.c?

But if we wanted to be pedantic, in addition to that it might be best to create a new internal function that can track if SDL_IterateMainCallbacks should be called based on the last time it was called.

Edit: Although thinking more on it, I don't know if SDL_EVENT_WINDOW_EXPOSED generated callbacks should be limited. Resize is still a little imperfect, but limiting our updates even more during that probably isn't the right call..

[1vanK]

Manual window movement is still actual to replace all workarounds

dviglo2d/dviglo2d@e16f683#diff-3c25d8de4f6d347a905731062e33d50c15948d07a3bcdcc9c2f785059b05b84a

[playmer]

Sorry, I didn't quite quite understand what you're saying there.

I took a first attempt at this: playmer@e126d54

But right now I'm not seeing WM_PAINT calling Iterate like I'd expect, which is needed for a callback rate of "waitevent" to work, so I need to investigate that. And another issue is that Windows doesn't seem particularly good about hitting all desired callback rates. When you request 10ms (the default), it's closer to the 16ms for 60 fps, but when you request 33ms, it's closer to 40ms or so for around 21-22 fps.

Obviously this could just be noted as something to know for the SDL_HINT_MAIN_CALLBACK_RATE documentation, as it's not always honored to begin with on platforms where it can't be. But it's something to point out.