Switch to 8bit buffers in some or all places

[hwhw]

Blitbuffers are currently 4bit based. That looked like a good idea since it saves memory (e.g. on the KDX: ~500kB vs. ~1MB for a fullscreen buffer) and resembled the framebuffer's layout.

However, blitting is very slow for a lot of cases (odd source or target X coordinates and rotated or modified buffers, namely). And we lose information that we could use e.g. for contrast/gamma setting, dithering or other occasions. Painting single pixels is awful for the memory cache as well.

My suggestion is to convert a lot of the buffers to 8bpp and to do the final step to 4bpp only when blitting to the framebuffer. I think we could make it interoperable with existing code in KPV.

All our rendering backends generate >=8bpp renderings anyway - the higher memory usage would just be for cached tiles.

[houqp]

Totally agree with you. I have been wanted to do this for a long time. It will make a code a lot cleaner and easier to maintain.

Sadly, I will be crazily busy for the coming 4 months so probably won't have time to do any serious hacking :(

[hwhw]

OK, as a first step, font rendering is now 8bpp. And a bit different - the 8bpp grayscale is taken as an alpha value for rendering an arbitrary color. Thus, we don't render a "background" for text, which was of no use anyway, since it was dependent on the "box" size of the glyph. Now we can properly render over any color, image or whatnot.

[houqp]

nice, the font rendering code seems a lot cleaner now :)