Hi, thank you for this project.

I'm wondering if this project could have something equivalent to picom's window-shader-fg-rule, which allows specifying a user-supplied GLSL file to use for windows matching user-defined rules.

Such a feature would allow achieving e.g. the following:

• Smart color inversion (for applications not supporting a "dark mode")
• Color-key based transparency (for applications without native transparency support)
• Ad-hoc hacks / accessibility improvements (adding guides/crosshairs, color correction for color blindness)

Upstream issue (closed WONTFIX): swaywm/sway#3652