Proper(ish) scanlines

[rutra80]

Currently it's not possible to have proper scanlines in all modes in WinUAE - they are either correct in non-laced or laced modes.

For example, at Double + 2x2 scaling, in non-laced modes 2:2 scanlines are ok, but in laced modes they should be 1:1. Also, there's a 1 pixel vertical shift in laced modes so scanlines offset doesn't match anymore.

A quick solution would be to have separate x:x and Offset settings for laced and non-laced modes on Filter tab (including 0:0 setting for laced modes when someone doesn't use any scaling, which would disable scanlines).

An ideal scanlines solution are shaders, but in laced modes they are wrecked by offset shift, and on shader level it doesn't seem possible to tell if the mode is laced or not. Once I asked Toni for separate laced & non-laced shaders, but there would be problems with switching them fast enough. Would it be possible to at least get rid of offset shift in laced modes?