Stop Picom loading when Compiz is selected?

[aubade]

On Ubuntu-Mate 24.04 where picom is installed by default, if you select Compiz in mate-tweak, compiz doesn't start properly and mate-panel shows up invisible until you kill and restart it. Is it possible to have mate-tweak detect when this is the case and take picom out of the session start when compiz is selected?

[2387skju]

It's fixed for the most Users, with the new version of picom.

Problem situations / effect

What i observed with parallel running of Picom: ( at debian 12 and picom v12.5 ; when picom autostart is working )

• when change from marco-no-composite => to compiz:
  Steps to reproduce:
  • install picom-conf
  • start picom-conf and change some settings (=> this will create ~/.config/picom.conf and results in an actived autostart of picom)
  • in Mate-Tweak: change window-manager to marco-no-composite
  • Logout of MATE and Re-login
  • in Mate-Tweak: Change from marco-no-composite => to compiz
    compiz will not start properly. Picom is in broken state: Not windowmanager at all (= no window decoration,...)
    Possible fix: add pkill picom
• when relogin with selected windowmanager marco-no-composite:
  picom is running ; so the composite is unwanted activ.
  Possible fix:
  • remove (or rename) the config file
  • disable the autostart (e.g. by local overwrite with Hidden=true)
• when relogin with selected windowmanager compiz: All OK
  Seems that picom can't be started a second composite manager (anymore): "Another composite manager is already running" (when started by hand)

---

When Picom will autostart

Picom changed it way to autostart in newer versions.

When autostart will work now:

• a config file exists (~/.config/picom.conf) (could be also created by e.g. GUI-config-Tool picom-conf),
  or
• manual edit of the autostart file (= add a new required parameter to start)

Change in picom in detail:

• Picom version v10 introduced the autostart file to the position /etc/xdg/autostart. Ubuntu 24.04 has picom v10.
• Since picom v12 the autostart changed:
  You must have a config file (~/.config/picom.conf), to get the autostart working.
  Otherwise, the autostart-file will work:

  Error: "Backend not specified."
  backend is now a required option. picom will not start if one is not specified explicitly. picom v12 ; commit Thu May 23 05:53:43 2024
  Ubuntu (25.10) and Debian (13) has picom v12.5.

---

I've send a Pull-Request: #108

• Before change to compiz: pkill picom
• Before change to marco-no-composite:
  • If the autostart are maybe active (= if systemwide autostart exists and picom config file exists).
  • Then inform the user (info-dialog):

'No composite' may not work:
After you re-login in MATE: Maybe the composite system will start again.
Reason: You have this config file: ~/.config/picom.conf
This can result in an unwanted autostart of picom.
(depends on the concret system-wide autostart files of your distribution.)

If another of my pull-Request was merge, we can improve here:

• temporar disable (by local overwrite) the autostart. (You can see this already in one of my commit in my personal repository)

---

Alternative solution:
Ask all the Distributions (or Picom itself) to change (or remove) the autostart file.
OpenSuse did this: The Autostart is now only part of package picom-conf and will only autostart for desktop lxqt:

/etc/xdg/autostart/lxqt-picom.desktop:
[...]
Hidden=true
OnlyShowIn=LXQt;
X-LXQt-Module=true