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PICOM

picom is a compositor for X11. It sits between Xorg and the window_manager, handling GPU-accelerated rendering via the GLX backend. Without it you get screen tearing on most hardware; with it you can also add shadows, transparency, and blur.

Why It's Needed​

X11 has no built-in compositing. Without a compositor:

  • Screen tearing on scrolling and video
  • No per-window transparency or blur
  • No window fade animations

Config​

Default location: ~/.config/picom/picom.conf

Backend​

backend = "glx";   # GPU-accelerated — preferred on most machines
# backend = "xrender";  # CPU fallback if GLX causes issues

Opacity​

inactive-opacity = 0.9;    # unfocused windows
active-opacity = 1.0;      # focused window
frame-opacity = 1.0;       # window decorations

Shadows​

shadow = true;
shadow-radius = 12;
shadow-offset-x = -12;
shadow-offset-y = -12;
shadow-opacity = 0.5;
shadow-exclude = ["class_g = 'i3-frame'"];

Blur (frosted glass)​

blur-method = "dual_kawase";
blur-strength = 5;
blur-background = true;
blur-background-exclude = ["window_type = 'dock'"];

Fading​

fading = true;
fade-in-step = 0.03;
fade-out-step = 0.03;
fade-delta = 5;

Current Setup (this machine)​

GLX backend only — all visual effects disabled. Picom is running purely to prevent screen tearing. Blur is commented out but ready to enable.

backend = "glx";
inactive-opacity = 1.0;
active-opacity = 1.0;
fading = false;
shadow = false;

i3 Integration​

In ~/.config/i3/config:

exec_always --no-startup-id pkill picom; picom --config ~/.config/picom/picom.conf

exec_always restarts picom on every i3 reload. pkill picom first ensures no duplicate instance runs.

References​