Driver is 415.27.
$ xdpyinfo -ext RENDER
...
pict format:
format id: 0x180
type: Direct
depth: 32
alpha: 24 mask 0xff
red: 16 mask 0xff
green: 8 mask 0xff
blue: 0 mask 0xff
...
visual format:
visual id: 0x23
pict format id: 0x180
In other words, visual 0x23 has alpha channel.
But OTOH
$ glxinfo
...
132 GLX Visuals
visual x bf lv rg d st colorbuffer sr ax dp st accumbuffer ms cav
id dep cl sp sz l ci b ro r g b a F gb bf th cl r g b a ns b eat
...
0x023 32 tc 0 24 0 r y . 8 8 8 0 . s 4 24 8 16 16 16 16 0 0 None
It doesn’t have the alpha channel in GLX.
Why the mismatch?