xcompmgr

Start with default settings (shadows and fading)

$ xcompmgr

$ xcompmgr -c -l [left_offset] -t [top_offset] -o [opacity]

$ xcompmgr -cCfF -D [fade_time_ms]

$ xcompmgr -fF

$ xcompmgr -c -r [shadow_radius] -o [0.5]

$ xcompmgr -c -n

xcompmgr [-d display] [-r radius] [-o opacity] [-l left] [-t top] [-cCfFnsSdD]

xcompmgr is a compositing window manager for the X Window System that adds visual effects to windows including drop shadows, transparency, and fading transitions. It operates as a standalone compositor that works with any ICCCM/EWMH compliant window manager.
The compositor uses the X Composite extension to redirect window contents to off-screen pixmaps, then combines them with effects before displaying. This enables true transparency without the need for pseudo-transparency techniques. Windows can have per-window opacity set via tools like transset.
Common configurations combine shadow (-c) and fade (-f) options for a polished desktop appearance. The shadow appearance is controlled through radius, offset, and opacity parameters. For lighter systems, shadows can be disabled on docks and panels with -C to reduce visual clutter.

-d display

Specifies which display to manage.

Enable client-side shadows on windows.

Disable shadows on dock/panel windows with NETWMWINDOWTYPE_DOCK.

Fade windows in and out when opening/closing.

Fade windows during opacity changes.

Shadow radius in pixels (default: 12).

Shadow opacity (0.0 to 1.0, default: 0.75).

Left offset for shadows in pixels (default: -15).

Top offset for shadows in pixels (default: -15).

Normal client-side shadows (no fading).

Enable synchronous X operation for debugging.

Enable shadows on windows with shapes.

Fade time step in milliseconds (default: 10).

Disable fading on window open/close.

Opacity change per step while fading in (default: 0.028).

Opacity change per step while fading out (default: 0.03).

Requires the Composite, Damage, Fixes, and Render X extensions to be enabled. May conflict with window managers that have built-in compositing (disable their compositor first). Performance depends on graphics driver quality; software rendering can be slow. Does not support advanced effects like blur or animations found in modern compositors like picom.

xcompmgr was written by Keith Packard and released as a sample compositing manager following the introduction of the X Composite extension around 2004. It served as a proof-of-concept and reference implementation demonstrating compositing capabilities in X.Org. While functional, it was superseded by more feature-rich compositors like compton and later picom, which offer additional effects and better performance.

picom(1), compton(1), transset(1), xwininfo(1)