Gameboy Shaders Screen Offset Issues

[Awakened0]

I thought this was related to #70 , but this might be it's own thing. Comparing the GLSL version of the gameboy-pocket preset (or the DMG one) to the slang version, there is a small white line to the top and left which offsets the image: http://screenshotcomparison.com/comparison/132457

I tried messing with the x and y screen offset parameters and discovered another difference. When you use values with .5 in them, the grid gets uneven in the slang version, but stays even in the glsl one. So maybe there's some issue with half pixels in the slang conversion? Setting the x and y offsets to -1 in the slang version does center the image the same as the glsl version. But, for some reason there are lines on the bottom and right.

I noticed this line in gb-pass0 when comparing versions. I wondered if the half pixel part wasn't supposed to be commented out and I tried removing the ";//". It seemed to center the black pixels, but the grid overlaying them was no longer aligned and the top half of the horizontal grid lines disappeared.

[nfp0]

Are you using the gameboy-pocket preset at it's default parameters? I was testing and mine looks a bit different than yours. Looks smoother. This is on Vulkan.

[Awakened0]

I use blending mode 0, which is the default in glsl. Gives it a cleaner, darker look. But even with the default, loading the preset from a fresh download of slang-shaders-master, I get the offset. I didn't change the slang default blending mode in the second comparison, so you can see the difference there.

[Awakened0]

Talking to hunterk on Discord, it seems like this is probably a side effect of changes he made to the slang version to prevent rounding issues. The grid becomes uneven with some of the fixes he had me try.

I think setting the screen offset x and y to -1 looks better than the default 0 when I look closely. The lines on the bottom and right look the same size as the rest of the grid. The lines that show up with defaults are probably twice as thick.