Comment 11 for bug 1371928

Maybe a special case because of hardware, but I encountered a semi-transparent GUI today.

The main window is mostly transparent as well as each dock except for titles and menus, which are correctly dark grey. I state "mostly" transparent because everything visible through the transparent regions is a moderately brighter color. The brushes all have transparent backgrounds, cyan symbols, a magenta lower-right arrow to select other brushes, and a solid green hover background. The color picker colors are only visible if the window behind is dark, and parts of the color ranges go full magenta as I choose colors.

NUC11 with a transplanted Dell XPS hard drive (did not reformat, just apt upgrade and installed nvidia driver 495)
Nvidia RTX 2060 + Iris Xe; monitor plugged into dGPU
10-bit color (set in xorg.conf.d and confirmed in /var/log and via screen test)
Ubuntu 21.10, GNOME 40.4.0, X11 (was Wayland on the XPS), 5.13.0-28-generic
GIMP 2.10.24 via apt (not flatpak)

There's no compiz on my machine, but I installed the settings-manager to double check if the solutions above work. As expected, animations is not even an installed module, so I removed the settings-manager. I also disabled GNOME extensions in case those had side effects.

Because of the color artifacts (especially the magenta at the ends of each color channel) and how this affects the UI (not related to color intent or color space), I suspect the 10-bit color is the source of the unwanted behavior, but I don't have a good explanation. (Although, I suspect I am not the first person to use a 10-bit monitor and dGPU with GIMP.)

To exonerate the GPU, monitor, kernel, GTK, etc.: Darktable, VLC, RawTherapee, and Inkscape have no issues and can display 10-bit and 8-bit gradient comparisons successfully.