[Ohrrpgce] SVN: teeemcee/13398 gfx_sdl2: bilinear smoothing, which can be applied after using 'smooth'

[subversion at HamsterRepublic.com]

teeemcee
2023-12-15 02:02:27 -0800 (Fri, 15 Dec 2023)
501
gfx_sdl2: bilinear smoothing, which can be applied after using 'smooth' upscaler

(This commit provides no way to turn it on.)

smooth_zoom is replaced with upscaler_zoom. If smooth=0 bilinear=YES, this will
first do nearest-neighbour upscaling then bilinear scaling to actual window
size, which matches the advantages of bilinear that all pixels look equal-size
but with less blurriness.

Also track frac_zoom, the current actual fractional zoom level.
'zoom' is frac_zoom roudned to nearest integer.
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U   wip/gfx_sdl2.bas