Get Picom working in Void

[mbvgua]

hello there, Im new to Void linux (from fedora linux) and would really appreciate your help in getting my scripts working properly in Void. the main one being this script that toggles all colors on the screen to grayscale. Currently using qtile so this is in my autostart.sh file:

# compositor
picom --config ~/.config/picom/picom-grayscale.conf -b &

that is supposed to start the window manager in grayscale mode by default, but it doesnt. then I should be able to toggle between the two different modes by pressing Tux+G as it is a keybind in qtile:

keys = [
    # toggle grayscale mode!! shiny lights bad...
    Key(
        [mod],
        "g",
        lazy.spawn(os.path.expanduser("~/.local/scripts/toggle_grayscale")),
        desc="toggle [g]rayscale mode systemwide",
    ),
]

Currenlty, hitting the keybind only displays a notification from dunst, nothing occurs in terms of color changes, the default colors are preserved. the keybind is supposed to run this script for toggling colors:

#!/usr/bin/env bash
# strict mode

CONFIG_PATH="$HOME/.config/picom/picom.conf"
GRAY_CONFIG_PATH="$HOME/.config/picom/picom-grayscale.conf"

# Identify the active monitor
MONITOR=$(xrandr | grep " connected" | cut -d' ' -f1 | head -n 1)

# clean up stuck gamma/brightness
reset_colors() {
    xrandr --output "$MONITOR" --gamma 1:1:1 --brightness 1
}

if pgrep -a picom | grep -q "picom-grayscale.conf"; then
    # EXITING GRAYSCALE: Turn Redshift back on
    killall picom
    # Wait until the old picom process is completely dead
    while pgrep -x picom >/dev/null; do sleep 0.05; done
    reset_colors
    dunstify -a picom -t 3000 -u low "let there be colours :)"
    picom --config ${CONFIG_PATH} -b &
else
    # ENTERING GRAYSCALE: Kill Redshift to prevent color conflicts
    killall picom
    # Wait until the old picom process is completely dead
    while pgrep -x picom >/dev/null; do sleep 0.05; done
    reset_colors
    dunstify -a picom -t 3000 -u low "turning on grayscale"
    picom --config ${GRAY_CONFIG_PATH} -b &
fi

which inturn uses the following picom configuration to set the grayscale:

#################################
#             Shadows           #
#################################

# Default: false
shadow = true;
shadow-radius = 7;

# The opacity of shadows. (0.0 - 1.0, defaults to 0.75)
# shadow-opacity = .75

# The left offset for shadows, in pixels. (defaults to -15)
# shadow-offset-x = -15
shadow-offset-x = -7;

# The top offset for shadows, in pixels. (defaults to -15)
# shadow-offset-y = -15
shadow-offset-y = -7;

# Specify a list of conditions of windows that should have no shadow.
#
# examples:
#   shadow-exclude = "n:e:Notification";
#
# shadow-exclude = []
shadow-exclude = [
  "name = 'Notification'",
  "class_g ?= 'Notify-osd'",
];

#################################
#           Fading              #
#################################

# Fade windows in/out when opening/closing and when opacity changes,
# unless no-fading-openclose is used. Can be set per-window using rules.
#
# Default: false
fading = true;

# Opacity change between steps while fading in. (0.01 - 1.0, defaults to 0.028)
fade-in-step = 0.03;

# Opacity change between steps while fading out. (0.01 - 1.0, defaults to 0.03)
fade-out-step = 0.03;

# The time between steps in fade step, in milliseconds. (> 0, defaults to 10)
fade-delta = 3;


#################################
#   Transparency / Opacity      #
#################################

# Opacity of inactive windows. (0.1 - 1.0, defaults to 1.0)
inactive-opacity = 0.8;

# Opacity of window titlebars and borders. (0.1 - 1.0, disabled by default)
frame-opacity = 1.0;
# frame-opacity = 0.7;

# Let inactive opacity set by -i override the '_NET_WM_WINDOW_OPACITY' values of windows.
# inactive-opacity-override = true
inactive-opacity-override = false;

# Default opacity for active windows. (0.0 - 1.0, defaults to 1.0)
active-opacity = 1;

# Dim inactive windows. (0.0 - 1.0, defaults to 0.0)
# inactive-dim = 0.0

opacity-rule = [ 
    # NOTE: handle this in-app! works better with inbuilt progs
    # neovim, tmux e.t.c
    "100:class_g = 'helium' && focused",
    "100:class_g = 'helium' && !focused",
    "100:class_g = 'teams-for-linux' && focused",
    "100:class_g = 'teams-for-linux' && !focused",
    "100:class_g = 'thunar' && focused",
    "100:class_g = 'thunar' && !focused",
];

#################################
#           Corners             #
#################################

# Sets the radius of rounded window corners. When > 0, the compositor will
# round the corners of windows. Does not interact well with
# `transparent-clipping`.
corner-radius = 20;

# Exclude conditions for rounded corners.
rounded-corners-exclude = [
  "window_type = 'dock'",
  "window_type = 'desktop'",
  "! name~=''",  # excluding windows with no name such as Qtile bar
];


#################################
#     Background-Blurring       #
#################################

# Parameters for background blurring, see BLUR section in the man page for more information.
blur-method = "dual_kawase";
blur-strength = 4;
# blur-size = 12

# Specify the blur convolution kernel, with the following format:
# example:
#   blur-kern = "5,5,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1";
# Can also be a pre-defined kernel, see the man page.
#
# Default: ""
blur-kern = "3x3box";

# Exclude conditions for background blur.
# blur-background-exclude = []
blur-background-exclude = [
  "window_type = 'dock'",
  "window_type = 'desktop'",
];

#################################
#       General Settings        #
#################################

# Specify the backend to use: `xrender`, `glx`, or `egl`.
#
# Default: "xrender"
backend = "glx";

# Use higher precision during rendering, and apply dither when presenting the
# rendered screen. Reduces banding artifacts, but might cause performance
# degradation. Only works with OpenGL.
dithered-present = false;

# Enable/disable VSync.
# vsync = false
vsync = true;

# Try to detect WM windows (a non-override-redirect window with no
# child that has 'WM_STATE') and mark them as active.
#
# mark-wmwin-focused = false
mark-wmwin-focused = true;

# Mark override-redirect windows that doesn't have a child window with 'WM_STATE' focused.
# mark-ovredir-focused = false
mark-ovredir-focused = true;

# Try to detect windows with rounded corners and don't consider them
# shaped windows. The accuracy is not very high, unfortunately.
#
# detect-rounded-corners = false
detect-rounded-corners = true;

# Detect '_NET_WM_WINDOW_OPACITY' on client windows, useful for window managers
# not passing '_NET_WM_WINDOW_OPACITY' of client windows to frame windows.
#
# detect-client-opacity = false
detect-client-opacity = true;

# Use EWMH '_NET_ACTIVE_WINDOW' to determine currently focused window,
# rather than listening to 'FocusIn'/'FocusOut' event. Might have more accuracy,
# provided that the WM supports it.
#
# use-ewmh-active-win = false
#
# detect-transient = false
detect-transient = true;

# Disable the use of damage information.
# This cause the whole screen to be redrawn every time, instead of the part of the screen
# has actually changed. Potentially degrades the performance, but might fix some artifacts.
# The opposing option is use-damage
#
# no-use-damage = false
use-damage = true;

# Use X Sync fence to sync clients' draw calls, to make sure all draw
# calls are finished before picom starts drawing. Needed on nvidia-drivers
# with GLX backend for some users.
#
# xrender-sync-fence = false

# GLX backend: Use specified GLSL fragment shader for rendering window
# contents. Read the man page for a detailed explanation of the interface.
#
window-shader-fg = "/home/daagi/.config/picom/grayscale.glsl"

# Set the log level. Possible values are:
#  "trace", "debug", "info", "warn", "error"
# in increasing level of importance. Case doesn't matter.
# If using the "TRACE" log level, it's better to log into a file
# using *--log-file*, since it can generate a huge stream of logs.
#
# log-level = "debug"
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 = 0.95; }
  dropdown_menu = { opacity = 0.95; }
};

and the glsl shader settings are in the below file:

#version 330

in vec2 texcoord;
uniform sampler2D tex;
uniform float opacity;

vec4 default_post_processing(vec4 c);

vec4 window_shader() {
    vec2 texsize = textureSize(tex, 0);
    vec4 color = texture2D(tex, texcoord / texsize, 0);

    // 1. Standard Grayscale conversion
    float gray = (color.r * 0.299) + (color.g * 0.587) + (color.b * 0.114);

    vec3 grayscale = vec3(gray);

    return vec4(grayscale * opacity, color.a * opacity);
}

I realised that Void does not have the 'killall command by default, and so I have added that by installing the psmisc utility that contains killall. Apart from that I cannot see any other fault in the config that would make the script notwork. I can also see that picom is running as a process using the grayscale config, but the colors are not being changed:

<user>    3784  1.4  0.9 448576 78020 ?        Ssl  16:34   0:06 picom --config /home/<user>/.config/picom/picom-grayscale.conf -b
<user>    7805  0.0  0.0   6704  2484 pts/1    S+   16:42   0:00 grep --color=auto picom

Could Void linux have something that prevents the colors from switiching?

[classabbyamp]

cc @0x5c

[0x5c]

Your shader works perfectly well for me, when passing it to picom with the --window-shader-fg <path-to-shader-file> argument. I recommend trying to run picom directly from the terminal with that argument plus --log-level info. I'm curious what the log output is like if that doesn't apply the shader.

I diffed the config you provided vs the one I have, and the structure is very different. Are you using a Fedora version that ships a picom version lower than 12? That version moved all the rule systems into one more capable and less clunky rules system, along with other important configuration file changes; picom might be rejecting your config and reverting to defaults or crashing. Here's upstream's info about that change and about the new format (including the section on migrating old rules).

I'm about to tackle the v13 update, and I'll test the shader there too.

[0x5c]

Just done the update to picom 13, both your configuration and shader work (with edited shader path). I haven't tested your config on 12 but if it works on 13 it really should have worked fine.

[mbvgua]

Hey! your fix for running the shader command from the cli worked for me. Having killed the picom instance, I ran it with the --window-shader-fg <path-to/file.glsl> command and it worked perfectly. Running it with the --log-level info flag, I got the following error:

[mbugua@void scripts]$ [ 06/02/2026 13:48:34.649 c2_parse_target WARN ] Type specifier is deprecated. Type "c" specified on target "_GTK_FRAME_EXTENTS" will be ignored, you can remove it.
[ 06/02/2026 13:48:34.649 c2_parse_target WARN ] Type specifier is deprecated. Type "c" specified on target "_GTK_FRAME_EXTENTS" will be ignored, you can remove it.
[ 06/02/2026 13:48:34.650 load_shader_source INFO ] Loading shader source from /home/mbugua/.dotfiles/.config/picom/grayscale-shader.glsl

Im guessing this is because I am still using an older format of the config file as youve stated, but I will migrate it to the newer version soon enough. I am on version 12.5. Thanks alot.

For posterity, this is what I settled on, in my workflow to instantly toogle grayscale mode:
In my autostart.sh file in qtile, I start in grayscale mode automatically:

# prevent screen tearing and turn on grayscale mode
picom --config ~/.config/picom/picom.conf -b --window-shader-fg ~/.config/picom/grayscale-shader.glsl &

I have a keybind to toggle colours in qtile:

    # toggle grayscale mode!! shiny lights bad...
    keys = [
        Key(
            [mod],
            "g",
            lazy.spawn(os.path.expanduser("~/.local/scripts/toggle_grayscale")),
            desc="toggle [g]rayscale mode systemwide",
        ),
    ]

And finally the script has been updated as follows:

#!/usr/bin/env bash

# strict mode
# set -euo pipefail

CONFIG_PATH="$HOME/.config/picom/picom.conf"
SHADER_PATH="$HOME/.config/picom/grayscale-shader.glsl"

# Identify the active monitor
MONITOR=$(xrandr | grep " connected" | cut -d' ' -f1 | head -n 1)

# clean up stuck gamma/brightness
reset_colours() {
    xrandr --output "$MONITOR" --gamma 1:1:1 --brightness 1
}

if pgrep -a picom | grep "grayscale-shader.glsl"; then
	# if grayscale is on, tuen it off
    killall picom
    while pgrep -x picom >/dev/null; do sleep 0.05; done
    reset_colours
    dunstify -a picom -t 3000 -u low "let there be colours :("
    picom --config "${CONFIG_PATH}" -b &
else
	# turn off the colours
    killall picom
    while pgrep -x picom >/dev/null; do sleep 0.05; done
    reset_colours
    dunstify -a picom -t 3000 -u low "turning on grayscale :)"
    picom --config "${CONFIG_PATH}" --window-shader-fg "${SHADER_PATH}" -b &
fi