Picom Compositor

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Compton is a compositor for the Xorg X11 Window System.

1. Configuration

1.1. Refresh Script

We'd like to make sure that picom's configuration is refreshed when our window manager is also refreshed. We have our window mannager configured so that it will refresh xinit user-level scripts so let's create a simple one that performs the refresh. Make sure to sleep 1 otherwise the new picom instance might not start up because it believes that another one is still alive.

pkill -x picom
if [ -f "$HOME/.config/picom/picom.conf" ]; then
    sleep 1 && picom &

1.2. Backend

Backend to use: "xrender" or "glx". GLX backend is typically much faster but depends on a sane driver.

backend = "xrender";

1.3. GLX backend

??? Don't remember what this does…

glx-no-stencil = true;

GLX backend: Copy unmodified regions from front buffer instead of redrawing them all. My tests with nvidia-drivers show a 10% decrease in performance when the whole screen is modified, but a 20% increase when only 1/4 is. My tests on nouveau show terrible slowdown. Useful with –glx-swap-method, as well.

glx-copy-from-front = false;

GLX backend: Avoid rebinding pixmap on window damage. Probably could improve performance on rapid window content changes, but is known to break things on some drivers (LLVMpipe). Recommended if it works. (Its turned off here)

# glx-no-rebind-pixmap = true;

1.4. Shadows

Enabled client-side shadows on windows.

shadow = true;

The blur radius for shadows. (default 12) The x offset for shadows. (default -15) The y offset for shadows. (default -15)

shadow-radius = 5;
shadow-offset-x = -5;
shadow-offset-y = -5;

The translucency for shadows. (default .75)

shadow-opacity = 0.5;

Set if you want different colour shadows

# shadow-red = 0.0;
# shadow-green = 0.0;
# shadow-blue = 0.0;

The shadow exclude options are helpful if you have shadows enabled. Due to the way compton draws its shadows, certain applications will have visual glitches (most applications are fine, only apps that do weird things with xshapes or argb are affected). This list includes all the affected apps I found in my testing. The "! name~=''" part excludes shadows on any "Unknown" windows, this prevents a visual glitch with the XFWM alt tab switcher.

shadow-exclude = [
    "! name~=''",
    "name = 'Notification'",
    "name = 'Plank'",
    "name = 'Docky'",
    "name = 'Kupfer'",
    "name = 'xfce4-notifyd'",
    "name *= 'VLC'",
    "name *= 'compton'",
    "name *= 'Chromium'",
    "name *= 'Chrome'",
    "class_g = 'Conky'",
    "class_g = 'Kupfer'",
    "class_g = 'Synapse'",
    "class_g ?= 'Notify-osd'",
    "class_g ?= 'Cairo-dock'",
    "class_g ?= 'Xfce4-notifyd'",
    "class_g ?= 'Xfce4-power-manager'",
    "[email protected]:c"

Avoid drawing shadow on all shaped windows (see also: –detect-rounded-corners)

shadow-ignore-shaped = false;

1.5. Opacity

Define opacity

inactive-opacity = 1;
active-opacity = 1;
frame-opacity = 1;
inactive-opacity-override = false;

Dim inactive windows. (0.0 - 1.0)

# inactive-dim = 0.2;

Do not let dimness adjust based on window opacity.

# inactive-dim-fixed = true;

Blur background of transparent windows. Bad performance with X Render backend. GLX backend is preferred.

# blur-background = true;

Blur background of opaque windows with transparent frames as well.

# blur-background-frame = true;

Do not let blur radius adjust based on window opacity.

blur-background-fixed = false;
blur-background-exclude = [
    "window_type = 'dock'",
    "window_type = 'desktop'"

1.6. Fading

Fade windows during opacity changes.

fading = true;

The time between steps in a fade in milliseconds. (default 10).

fade-delta = 4;

Opacity change between steps while fading in. (default 0.028).

fade-in-step = 0.03;

Opacity change between steps while fading out. (default 0.03).

fade-out-step = 0.03;

Fade windows in/out when opening/closing

# no-fading-openclose = true;

Specify a list of conditions of windows that should not be faded.

fade-exclude = [ ];

1.7. Other

Try to detect WM windows and mark them as active.

mark-wmwin-focused = true;

Mark all non-WM but override-redirect windows active (e.g. menus).

mark-ovredir-focused = true;

Use EWMH _NET_WM_ACTIVE_WINDOW to determine which window is focused instead of using FocusIn/Out events. Usually more reliable but depends on a EWMH-compliant WM.

use-ewmh-active-win = true;

Detect rounded corners and treat them as rectangular when –shadow-ignore-shaped is on.

detect-rounded-corners = true;

Detect _NET_WM_OPACITY on client windows, useful for window managers not passing _NET_WM_OPACITY of client windows to frame windows. This prevents opacity being ignored for some apps. For example without this enabled my xfce4-notifyd is 100% opacity no matter what.

detect-client-opacity = true;

Specify refresh rate of the screen. If not specified or 0, compton will try detecting this with X RandR extension.

refresh-rate = 0;

Set VSync method. VSync methods currently available:

  • none: No VSync
  • drm: VSync with DRMIOCTLWAITVBLANK. May only work on some drivers.
  • opengl: Try to VSync with SGIvideosync OpenGL extension. Only work on some drivers.
  • opengl-oml: Try to VSync with OMLsynccontrol OpenGL extension. Only work on some drivers.
  • opengl-swc: Try to VSync with SGIswapcontrol OpenGL extension. Only work on some drivers. Works only with GLX backend. Known to be most effective on many drivers. Does not actually control paint timing, only buffer swap is affected, so it doesn’t have the effect of –sw-opti unlike other methods. Experimental.
  • opengl-mswc: Try to VSync with MESAswapcontrol OpenGL extension. Basically the same as opengl-swc above, except the extension we use.

(Note some VSync methods may not be enabled at compile time.)

vsync = true;

Enable DBE painting mode, intended to use with VSync to (hopefully) eliminate tearing. Reported to have no effect, though.

dbe = false;

Unredirect all windows if a full-screen opaque window is detected, to maximize performance for full-screen windows, like games. Known to cause flickering when redirecting/unredirecting windows. paint-on-overlay may make the flickering less obvious.

unredir-if-possible = true;

Specify a list of conditions of windows that should always be considered focused.

focus-exclude = [ ];

Use WM_TRANSIENT_FOR to group windows, and consider windows in the same group focused at the same time.

detect-transient = true;

Use WM_CLIENT_LEADER to group windows, and consider windows in the same group focused at the same time. WM_TRANSIENT_FOR has higher priority if –detect-transient is enabled, too.

detect-client-leader = true;

1.8. Window Type Settings

    tooltip =
        # fade: Fade the particular type of windows.
        fade = true;
        # shadow: Give those windows shadow
        shadow = false;
        # opacity: Default opacity for the type of windows.
        opacity = 0.85;
        # focus: Whether to always consider windows of this type focused.
        focus = true;

Created: 2021-11-13

Emacs 26.1 (Org mode 9.5)