Mutter automatically checks environment variables during its initialization. These environment variables are meant as debug tools or overrides for default behaviours: MUTTER_VERBOSE Enable verbose mode, in which more information is printed to the console. Mutter needs to be built with the --enable-verbose-mode option (enabled by default). For more fine-grained control of the output, see meta_add_verbose_topic(). MUTTER_DEBUG Traps and prints X errors to the console. MUTTER_G_FATAL_WARNINGS Causes any logging from the domains Mutter, Gtk, Gdk, Pango or GLib to terminate the process (only when using the log functions in GLib). MUTTER_USE_LOGFILE Log all messages to a temporary file. MUTTER_DEBUG_XINERAMA Log extra information about support of the XINERAMA extension. MUTTER_DEBUG_SM Log extra information about session management. MUTTER_DEBUG_BUTTON_GRABS Log extra information about button grabs. MUTTER_SYNC Call XSync after each X call. MUTTER_DISPLAY Name of the X11 display to use. META_DISABLE_MIPMAPS Disable use of mipmaps for the textures that back window pixmaps. MUTTER_USE_STATIC_GRAVITY Enable support for clients with static bit-gravity. MUTTER_WM_CLASS_FILTER Comma-separated list of WM_CLASS names to which to restrict Mutter to. MUTTER_DISABLE_FALLBACK_COLOR Disable fallback for themed colors, for easier detection of typographical errors.