Scroll is not smooth with VSYNC ON

[vanfanel]

Hi there,

Recently, the general VSYNC option was added to upstream Scummvm.
Activating VSYNC in Scummvm prevents tearing, and makes scrolling sections smooth. For example, on the Ween (PC-DOS) intro there's a scrolling sequence that's perfectly smooth on upstream Scummvm.

However, using this libretro backend, the same sequence is not smooth: engine updates don't seem to be synchronized with the host screen refresh rate.
Would it be possible to fix this, please?

Thanks!

[diablodiab]

Functionality like this is what I'm hoping might be addressed if this backend is adopted as an official libretro core. Making full use of the capabilities of libretro, such as proper 3D acceleration, vsync, etc. is where the main libretro team comes in.

I'm focusing mainly on keeping the libretro backend compatible with upstream ScumVM and not implementing improvements to the functionality of the backend itself.