Custom PPSSPP shaders

[galaxy.zanya]

After playing Liberty City Stories on PCSX2 emulator, I finally got to play Chinatown wars on PPSSPP emulator.
And what I'm missing here is scanlines filter variant that was presented there.
Its called: diagonal filter.
So my question will be: is it possible to modify current scanline shader to add an angle, or it will be easier to write down new one (port from PCSX2)?

On first sight it looks kinda simple, just same lines over entire screen, just with 45 degree angle.
https://i.imgur.com/Iz4GV3n.png