Picom v12 (Compiled) shows "EGL WARN despite Xfwm4 disabled and --backend glx"

[marc-rm]

I'm experiencing a persistent issue with Picom v12, compiled from source, on my Linux Mint Xfce system. Despite ensuring that Xfce's native compositor (xfwm4) is disabled and explicitly trying to force the glx backend, Picom consistently reports "Another compositor is already running" and an EGL initialization warning, even when EGL support was intended to be disabled during compilation.

Steps to Reproduce:

1. System Setup:

   • OS: Linux Mint Xfce (based on Ubuntu 24.04)
   • Desktop Environment: Xfce
   • Window Manager: xfwm4 (compositor confirmed disabled via GUI and xfconf-query)
   • GPU: Intel HD Graphics 5500 (BDW GT2)

2. Compilation Process (Picom v12):

   • Cloned the latest Picom source from GitHub.
   • Disabled Xfwm4's compositor via "Window Manager Tweaks".
   • Ensured no other Picom instances were running (killall picom).
   • Used the following commands for compilation (cleaned build/ before meson setup):

     cd ~/picom
     rm -rf build/
     meson setup build/ -Dopengl=true
     ninja -C build/
     sudo ninja -C build/ install

   • Configured autostart (~/.config/autostart/picom.desktop) to launch Picom as:
     Exec=/usr/local/bin/picom --config /home/moreno/.config/picom/picom.conf --daemon
     (Note: I also tried adding --backend glx here in previous attempts, but the diagnostic output remained the same).

3. Observation:
   After logging in (or manually starting Picom with /usr/local/bin/picom --daemon --backend glx), running picom --diagnostics yields the following output:

Expected Behavior:

• Picom v12 should start successfully with Use Overlay: Yes.
• The egl_init WARN should not appear.
• Backend: glx should be the active/reported backend.

Actual Behavior:

• Use Overlay: No (Another compositor is already running).
• The egl_init WARN persists.
• Backend: egl is reported as the primary backend, even though opengl=true was set during compilation and egl was not explicitly enabled.

Relevant Logs and Information:

• picom --diagnostics output:

  **Version:** v12 ([https://github.com/yshui/picom.git](https://github.com/yshui/picom.git) revision b995372)
  
  ### X extensions:
  
  * GLX: present
  * Present: present
  * RandR: present
  * Shape: present
  * Sync: present
  
  ### Misc:
  
  * Use Overlay: No
    (Another compositor is already running)
  * Config file specified: None
  * Config file used: /home/moreno/.config/picom/picom.conf
  
  ### Drivers (inaccurate):
  
  modesetting
  [ 31/05/25 16:16:08.147 egl_init WARN ] The egl backend is still experimental, use with care.
  
  ### Backend: egl
  
  * Driver vendors:
    * EGL: Mesa Project
    * EGL driver: iris
    * GL: Intel
  * GL renderer: Mesa Intel(R) HD Graphics 5500 (BDW GT2)
  
  ### Backend: glx
  
  * Driver vendors:
    * GLX: Mesa Project and SGI
    * GL: Intel
  * GL renderer: Mesa Intel(R) HD Graphics 5500 (BDW GT2)
  * Accelerated: 1
  

• lsb_release -a output:

  Distributor ID: Linuxmint
  Description: Linux Mint 22.1
  Release: 22.1
  Codename: xia
  

• uname -r output:

  6.8.0-60-generic
  

• glxinfo | grep "OpenGL renderer" output:

  OpenGL renderer string: Mesa Intel(R) HD Graphics 5500 (BDW GT2)
  

• xfconf-query -c xfwm4 -p /general/use_compositing output:

  false
  

• ~/.config/picom/picom.conf content:

  # Backend (Motor de renderizado)
  backend = "glx";
  
  
  # Configuración de Picom (sin fading, sombras ni blur)
  
  # Fading (Desvanecimiento)
  fading = false;
  no-fading-openclose = true;
  
  # Opacity (Opacidad de las ventanas)
  inactive-opacity = 1.0;
  active-opacity = 1.0;
  frame-opacity = 1.0;
  inactive-opacity-override = false;
  inactive-dim = 0.0;
  
  # Shadows (Sombras)
  shadow = false;
  
  # Corner Radius (Esquinas redondeadas)
  corner-radius = 0;
  
  # VSync (Sincronización vertical)
  vsync = true;
  use-damage = true;
  # Blur (Desenfoque)
  blur-background = false;
  
  # Otros
  mark-wmwin-focused = true;
  mark-ovredir-focused = true;
  detect-rounded-corners = false;
  detect-client-opacity = true;
  use-ewmh-active-win = true;
  unredir-if-possible = true;
  detect-transient = true;
  detect-client-leader = true;
  
  # D-Bus (para controlar Picom externamente)
  dbus = false;
  
  # Logging (Registro de eventos)
  log-level = "warn";
  # log-file = "/tmp/picom.log";

• ~/.config/autostart/picom.desktop content:

  [Desktop Entry]
  Type=Application
  Exec=/usr/local/bin/picom --config /home/moreno/.config/picom/picom.conf --daemon
  Hidden=false
  NoDisplay=false
  X-GNOME-Autostart-enabled=true
  Name=Picom Compositor
  Comment=Starts Picom compositor for visual effects

Sorry for how I did it, I didn't know how to do it.