Async mouse and keyboard input on windows

[Susko3]

• Closes: Investigate receiving input without using window event flow #6141
• Should fix: Input thread blocking causes mouse handling stutters on windows #6181

Depends on:

• Upgrade to SDL3 #6234

This PR simply handles relative mouse and keyboard events in the SDL_EventFilter i.e. HandleEventFromFilter.

This works because SDL queries raw mouse and keyboard inputs on a separate thread. Our SDL_EventFilter will intercept those events before they are pushed to the internal SDL queue, handle them, and then request SDL to drop them.

Testing

Apply the diff and toggle relative mouse mode in TestSceneInputManger.
This isn't a perfect simulation of SDL_PumpEvents() lag, but it shows the async input in action.

diff --git a/osu.Framework/Platform/SDL3Window.cs b/osu.Framework/Platform/SDL3Window.cs
index aac3baf44..737547203 100644
--- a/osu.Framework/Platform/SDL3Window.cs
+++ b/osu.Framework/Platform/SDL3Window.cs
@@ -460,6 +460,7 @@ private void setSDLIcon(Image<Rgba32> image)
         private void pollSDLEvents()
         {
             SDL3.SDL_PumpEvents();
+            Thread.Sleep(100);
 
             int eventsRead;

[peppy]

This seems to break input on my VM setup. Yes I have a weird setup but it did work, so something has potentially changed or broken. I haven't yet investigated why, but can if required (if the issue isn't obvious).

master:

2024-04-15.15.35.29.mp4

this PR:

2024-04-15.15.34.02.mp4

[peppy]

As commented

[Susko3]

Hmm, it's weird that the relative mouse movements align with the cursor in one scenario but not the other. But I wouldn't call it broken, the framework cursor is still moving proportionally to your mouse movements.

The weirder thing is that the mouse cursor isn't hidden when in relative mode.

I have no idea what could cause any of this. But if you'll be looking at this, don't forget to enable event logging with

SDL3.SDL_SetHint(SDL3.SDL_HINT_EVENT_LOGGING, "2"u8);

[peppy]

the framework cursor is still moving proportionally to your mouse movements

I tried to show this, but it's actually not proportionally correct either. I'll see what I can find.