frame opacity doesn't work with experimental xrender backend

[absolutelynothelix]

picom built from last commit
picom --experimental-backends --backend xrender --frame-opacity 0.5

frame changes it's color but there is no opacity
hmu if you can't reproduce this and need additional info on my setup

[yshui]

Cannot reproduce:

[absolutelynothelix]

ok, i'll post additional info and screenshots when i'll be at home. could it be a driver issue since it's xrender, not glx?

[yshui]

@mighty9245 my screenshot is from xrender.

[absolutelynothelix]

@yshui, hey, can you please test with opaque terminal? i mean you probably have terminal background opacity configured somewhere. what if you make terminal background opaque?

[yshui]

@mighty9245

what if you make terminal background opaque?

still works.

[absolutelynothelix]

weird... well, that's what i have

you can see how the picom was launched and the results: two instances of kitty have background_opacity set to 1.0 (which means opaque background) and the third one has background_opacity set to 0.95 (which means barely transparent) but in this case frame opacity applied correctly and i can see background through it. the same issue persists for all opaque windows (e. g. browser)

specs:
arch linux x86_64 5.5.9-arch1-2
bspwm 0.9.7-10-g2ffd9c1
picom built from 33a5cc6
modesetting driver
intel uhd graphics 620

also reproducible on amd r9 380 (amdgpu driver)

do you need anything else?

[yshui]

@mighty9245 and the glx background doesn't have this problem?

[absolutelynothelix]

@yshui, yeah, running the same command but setting backed to glx works just fine, every window got it's transparent frame.

[absolutelynothelix]

@yshui, hey, i think i know what the problem is. if window doesn't have any transparent parts it has 24bit depth, adding transparent parts to it (e. g. changing background opacity in terminal) changes it's depth to 32bit. as a workaround i changed xrender's copy method to set visual to 0x1b3 and depth to 32 for every image it creates and the issue is gone. however, i don't know how to fix this in a decent way.

also idk if problem is really in depth or in visual, because changing depth without changing visual causes picture creation failure. i think they are tied.

[yshui]

I think you are right.