Garbled Firefox window display after switching between desktops

[mbrla0]

Platform

Gentoo systemd amd64

GPU, drivers, and screen setup

mbr@diamond ~ $ glxinfo -B
name of display: :0
display: :0  screen: 0
direct rendering: Yes
Memory info (GL_NVX_gpu_memory_info):
    Dedicated video memory: 8192 MB
    Total available memory: 8192 MB
    Currently available dedicated video memory: 7700 MB
OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: NVIDIA GeForce GTX 1070 Ti/PCIe/SSE2
OpenGL core profile version string: 4.6.0 NVIDIA 470.86
OpenGL core profile shading language version string: 4.60 NVIDIA
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile

OpenGL version string: 4.6.0 NVIDIA 470.86
OpenGL shading language version string: 4.60 NVIDIA
OpenGL context flags: (none)
OpenGL profile mask: (none)

OpenGL ES profile version string: OpenGL ES 3.2 NVIDIA 470.86
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20

mbr@diamond ~ $ xrandr
Screen 0: minimum 8 x 8, current 3280 x 1080, maximum 32767 x 32767
DVI-D-0 connected primary 1920x1080+1360+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080     60.00*+
   1680x1050     59.95
   1280x1024     75.02    60.02
   1152x864      75.00
   1024x768      75.03    60.00
   800x600       75.00    60.32
   640x480       75.00    59.94
HDMI-0 connected 1360x768+0+0 (normal left inverted right x axis y axis) 700mm x 390mm
   1360x768      60.02*+
   1920x1080     60.00    59.94    60.05    60.00
   1280x720      60.00    59.94
   1024x768      75.03    70.07    60.00
   800x600       75.00    72.19    60.32    56.25
   720x480       59.94
   640x480       75.00    72.81    59.94

Environment

i3-gaps 4.20.1-74-gc7ad7569

picom version

vgit-31e58

Diagnostics

**Version:** vgit-31e58

### Extensions:

* Shape: Yes
* XRandR: Yes
* Present: Present

### Misc:

* Use Overlay: No
  (Another compositor is already running)
* Config file used: /home/mbr/.config/picom.conf

### Drivers (inaccurate):

NVIDIA

### Backend: glx

* Driver vendors:
 * GLX: NVIDIA Corporation
 * GL: NVIDIA Corporation
* GL renderer: NVIDIA GeForce GTX 1070 Ti/PCIe/SSE2

Configuration:

Configuration file

backend = "glx"

shadow = true;

xrender-sync-fence = true;
glx-copy-from-front = false;
vsync = true;

fading = true;
fade-in-step = 0.09;
fade-out-step = 0.09;

shadow-exclude = [
        "class_g = 'i3-frame'",
        "class_g = 'firefox' && argb",
        "class_g = 'slop'",
        "_NET_WM_STATE@:32a *= '_NET_WM_STATE_HIDDEN'"
];

blur-background-exclude = [
        "class_g = 'i3-frame'",
        "class_g = 'firefox' && argb",
        "class_g = 'slop'",
        "_NET_WM_STATE@:32a *= '_NET_WM_STATE_HIDDEN'"
];

blur:
{
        method = "dual_kawase";
};

wintypes:
{
        dnd = { shadow = false; clip-shadow-above = true; }
        normal = { blur-background = true; }
};

Steps of reproduction

1. Leave Firefox open in a tab whose contents don't repaint the window (any static page should do).
2. Open a second window on the same desktop.
3. Have Firefox be the focused window.
4. Transfer focus to the window you've just opened, then enter and leave fullscreen mode in that window.

I can also easily trigger this bug by switching desktops instead of going into fullscreen mode, so long as the focus on kept on the window other than Firefox. It also seems to not happen at all if Firefox has the active focus before the switch.

Expected behavior

Upon leaving fullscreen mode, Firefox should look as it did before the second window went fullscreen.

Current Behavior

Upon leaving, the Firefox window shows, instead, a completely garbled output.

Other details

Before setting the terminal window fullscreen with the i3 command:

After returning from fullscreen mode: