enable SDL texture filter for better graphic

[sonilyan]

[sonilyan]

Linux compilation error, SDL_ SetTextureScaleMode is a newly added API in Sdl 2.0.12. Is the compilation environment library too old?

[Risu]

Looks blurry on the right, I don't like it.

[a-hurst]

I feel like a matter of personal preference such as this should be added as something that's toggled in f2_res.ini? When I made the PR that implemented SCALE_2X support I deliberately left the scaling method as nearest-neighbour since that's truest to the original game and to the Sfall implementation of SCALE_2X.

I certainly see why people might prefer smooth scaling, but like I said, I think it should be optional.