fastcompmgr

fastcompmgr is a fast compositor for X, a fork of an early version of Compton which is a fork of xcompmgr-dana which is a fork of xcompmgr.

This repository is a fork. Its recent maintenance changes were made with assistance from OpenAI GPT-5.6 Terra.

I used to use good old xcompmgr for long, because compton always felt a bit laggy when moving/resizing windows or kinetic-scrolling a webpage. Having tested the latest picom-10.2, it seems, things got even worse (see benchmark below). However, xcompmgr does not draw shadows on argb windows (e.g. some terminals) and has several other glitches. That's why I traveled back into 2011, where this feature was just added, cherry picked some later compton commits to get rid of spurious segfaults and memleaks and made that version even faster, based on profiling. For example, window move- and resize events are coalesced and all repaint work is paced to the display refresh rate. Occluded windows are not painted and memory allocations/deallocations are largely avoided, allowing for faster repaints of the screen.

Benchmark

While on my Dell Latitude E5570 window moving, resizing and scrolling feels clearly faster, there are also some numbers to support this observation. Given a number of stacked chromium-windows, where no window is fully occluded, I performed the respective operations by hand, so please beware that the benchmark is not very sophisticated. The touchpad driver xserver-xorg-input-synaptics was used which enables for kinetic scrolling (Wayland anyone?). The following CPU usages were measured:

Compositor	move	resize	scroll
fastcompmgr	6.7%	4.4%	1.5%
xcompmgr	7.8%	4.9%	1.6%
compton	26.4%	6.8%	17.1%
picom	29.3%	8.1%	23.1%

Tools were used with the following flags:

(v0.1) fastcompmgr -o 0.4 -r 12 -c -C
(v1.1.8 from Debian 11) xcompmgr -o 0.4 -r 12 -c -C
(v1 from Debian 11) compton --config /dev/null --backend xrender -o 0.4 -r 12 -c -C
(v10.2) picom --config /dev/null --backend xrender -o 0.4 -r 12 -c

# Calc average using
$ fastcompmgr -o 0.4 -r 12 -c -C &  pid=$!; sleep 4; \
    top -b -n 20 -d 0.5 -p $pid | LC_ALL=C awk -v pid=$pid \
    '$1==PID {++PIDCOUNT} $1==pid && PIDCOUNT>1 {print $9}' |  \
    datamash mean 1; kill $pid

Installation

If you're lazy, just grab the binary from the release page.

Otherwise, install the development versions of the following libraries:

Dependencies:

• libx11
• libxcomposite
• libxdamage
• libxfixes
• libxrender
• libxrandr
• libxext
• pkg-config
• make
• a C compiler

To build:

$ make
$ make install

Usage

$ fastcompmgr -o 0.4 -r 12 -c -C

All options:

   -d display
    Which display should be managed.
   -r radius
    The blur radius for shadows. (default 12)
   -o opacity
    The translucency for shadows. (default .75)
   -l left-offset
    The left offset for shadows. (default -15)
   -t top-offset
    The top offset for shadows. (default -15)
   -m opacity
    The opacity for menu, dropdown-menu, popup-menu, and combo windows.
    (default 1.0)
   -c
    Enable client-side shadows on windows. Shadows are not drawn on menus,
    popup menus, dropdown menus, combo-box popups, or tooltips, because those
    window types use an oversized rect with no shape info and would render as
    a transparent box around the popup.
   -C
    Avoid drawing shadows on dock/panel windows.
   -f
    Fade windows in and out when opening, closing, hiding, or restoring.
   -F
    Also fade opacity changes.
   -I fade-in-step
    Opacity change per fade step. (default 0.028)
   -O fade-out-step
    Opacity change per fade step. (default 0.03)
   -D fade-delta-time
    Time between fade steps in milliseconds. (default 10)
   -i opacity
    Opacity of inactive windows. (0.0 - 1.0)
   -e opacity
    Opacity of window titlebars and borders. (0.0 - 1.0)
   -S
    Enable synchronous operation for debugging. Normal operation is asynchronous.
   -h, --help
    Show usage information.
    --shadow-red value
    Red color value of shadow (0.0 - 1.0, defaults to 0).
    --shadow-green value
    Green color value of shadow (0.0 - 1.0, defaults to 0).
    --shadow-blue value
    Blue color value of shadow (0.0 - 1.0, defaults to 0).
   --refresh-rate N
    Override display refresh rate in Hz (0 = autodetect via XRandR, default).
   --print-stats
    Print one-line rendering statistics once per second to stderr.

License

xcompmgr has gotten around. As far as I can tell, the lineage for this particular tree is something like:

• Keith Packard (original author)
• Matthew Hawn
• ...
• Dana Jansens
• Christopher Jeffrey
• Tycho Kirchner

Not counting the tens of people who forked it in between.

See LICENSE for more info.