popup_menu has clipping border when using --experimental-backends

[KnightWhoSaysNeeeowWumPing]

Platform

OS: Arch Linux
Kernel: 5.15.74-1-lts

GPU, drivers, and screen setup

$ glxinfo -B
name of display: :0
display: :0  screen: 0
direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: Intel (0x8086)
    Device: Mesa Intel(R) UHD Graphics (TGL GT1) (0x9a60)
    Version: 22.2.1
    Accelerated: yes
    Video memory: 31828MB
    Unified memory: yes
    Preferred profile: core (0x1)
    Max core profile version: 4.6
    Max compat profile version: 4.6
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.2
OpenGL vendor string: Intel
OpenGL renderer string: Mesa Intel(R) UHD Graphics (TGL GT1)
OpenGL core profile version string: 4.6 (Core Profile) Mesa 22.2.1
OpenGL core profile shading language version string: 4.60
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile

OpenGL version string: 4.6 (Compatibility Profile) Mesa 22.2.1
OpenGL shading language version string: 4.60
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile

OpenGL ES profile version string: OpenGL ES 3.2 Mesa 22.2.1
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20

Environment

i3wm

picom version

$ picom --version
vgit-7e568

$ sudo pacman -Ss picom | head -n 1
community/picom 9.1-3 [installed]

Diagnostics

**Version:** vgit-7e568

### Extensions:

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

### Misc:

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

### Drivers (inaccurate):

modesetting

### Backend: glx

* Driver vendors:
 * GLX: Mesa Project and SGI
 * GL: Intel
* GL renderer: Mesa Intel(R) UHD Graphics (TGL GT1)
* Accelerated: 1

Configuration:

Configuration file

shadow = false;
shadow-radius = 7;
shadow-offset-x = -7;
shadow-offset-y = -7;
shadow-exclude = [
  "name = 'Notification'",
  "class_g = 'Conky'",
  "class_g ?= 'Notify-osd'",
  "class_g = 'Cairo-clock'",
  "_GTK_FRAME_EXTENTS@:c",
  "(class_g = 'Firefox' || class_g = 'Thunderbird') && (window_type = 'utility' || window_type = 'popup_menu') && argb"
];
fading = true;
fade-in-step = 0.03;
fade-out-step = 0.03;
fade-delta = 5
fade-exclude = [
  "(class_g = 'Firefox' || class_g = 'Thunderbird') && (window_type = 'utility' || window_type = 'popup_menu') && argb"
]
inactive-opacity = 1.0;
inactive-opacity-override = false;
active-opacity = 1.0
focus-exclude = [ "class_g = 'Cairo-clock'" ];
opacity-rule = [
  "90:class_g = 'kitty' && focused",
  "75:class_g = 'kitty' && !focused"
]
corner-radius = 0
rounded-corners-exclude = [
  "window_type = 'dock'",
  "window_type = 'desktop'",
  "(class_g = 'Firefox' || class_g = 'Thunderbird') && (window_type = 'utility' || window_type = 'popup_menu') && argb"
];
blur-kern = "3x3box";
blur-background-exclude = [
  "window_type = 'dock'",
  "window_type = 'desktop'",
  "_GTK_FRAME_EXTENTS@:c",
  "(class_g = 'Firefox' || class_g = 'Thunderbird') && (window_type = 'utility' || window_type = 'popup_menu') && argb"
];
backend = "xrender";
vsync = true;
mark-wmwin-focused = true;
mark-ovredir-focused = true;
detect-rounded-corners = true;
detect-client-opacity = true;
detect-transient = true;
glx-no-stencil = true;
use-damage = true;
log-level = "warn";
wintypes:
{
  tooltip = { fade = true; shadow = true; opacity = 0.95; focus = true; full-shadow = false; };
  dock = { shadow = false; clip-shadow-above = true; }
  dnd = { shadow = false; }
  popup_menu = { opacity = 1.0; fade = false; shadow = false; focus = false; full-shadow = false; clip-shadow-above = false; }
  dropdown_menu = { opacity = 1.0; fade = false; }
};

Steps of reproduction

1. Starting picom as described below (using --experimental-backends --transparent-clipping)
2. Starting e.g. Firefox and right clicking to trigger a popup_menu

Expected behavior

I want only my terminal kitty to be transparent in the following manner:
The desktop wallpaper should be used as the actual background of the terminal - even if the terminal is in front of another application. To achieve this desired behavior, I followed the suggestion from #265 and start picom using the aforementioned configuration with the following line in my ~/.config/i3/config:

exec_always --no-startup-id picom --experimental-backends --transparent-clipping

This should render the wallpaper as terminal background within kitty (which works flawlessly) but should not affect other applications as they are not explicitly mentioned in the opacity-rule of the config above.

Current Behavior

popup_menus like those in Firefox, Thunderbird or Zoom are displayed with a border around them as seen in the following screenshot. Through this border, the actual desktop wallpaper is visible.

Stack trace

/

OpenGL trace

/

Other details

As can be seen from my config, I already tried the solution from #836.
I also tried disabling client side decorations as described in the archwiki and pointed out in #737.
Furthermore, I don't see how the solution of #901 applies here, as I have not mentioned Firefox at all in my set of opacity-rules.

[yshui]

This unfortunately is not easy to solve on our side. Many firefox menus windows are slightly bigger than what's visible, with a transparent margin around the visible part. firefox either needs to stop doing this, or setup the shape of the window properly.

Meanwhile, there is #738 which can be used to conditionally disable transparent-clipping, which can be used to workaround this.

[KnightWhoSaysNeeeowWumPing]

Thank you very much for this workaround!

I can confirm that the following config setting works on a fresh master build of picom:

transparent-clipping-exclude = [
  "class_g = 'firefox'",
];

The strange border is gone.

For reference:

$ picom --version
vgit-2dae0

I'm looking forward to the next release containing this 😄