SDL_GetRelativeMouseState(): Get relative mouse position also when relative mouse mode is disabled

[Sackzement]

Currently the relative mouse position is only set if relative mouse mode is enabled.
That makes SDL_GetRelativeMouseState() only work in relative mouse mode.

This commit removes the check for relative mouse mode and lets the variables be always set.

Fixes #12286

[slouken]

Merged, thanks!

[expikr]

This is completely wrong and should be reverted.

The author misunderstood the purpose of SDL_GetRelativeMouseState’s xy value which serves as a stateful accumulator for relative motion to emulate how legacy non-rawinput games use a constantly recentered cursor to calculate mouse motion once per frame instead of processing mouse motion in the event loop properly.

By definition, if you are not in relative mode then you are not generating relative motion.

Perhaps this is a documentation problem where the docs for the API function did not sufficiently clarify the purpose of this (legacy) functionality?

[slouken]

SDL_GetRelativeMouseState() has always served as an accumulator of mouse deltas regardless of whether relative motion is enabled. We especially need to continue that behavior so sdl2-compat works correctly. If you need to flush that, just call SDL_GetRelativeMouseState() when you change relative mode, to clear the accumulator.

[expikr]

That wasn’t the impression I got while digging for its provenance, but if that had always been the intent from its inception, I suggest the documentation should be updated to clarify the intent of this function’s usage.