Freedesktop

https://en.wikipedia.org/wiki/Freedesktop.org

freedesktop.org formerly X Desktop Group (XDG)

Fedora package	Commands	Notes
desktop-file-utils^rpm	desktop-file-install(1), desktop-file-validate(1), update-desktop-database(1)	desktop-file-edit(1) only link on `desktop-file-install`
xdg-user-dirs^rpm	xdg-user-dir(1) (shell script), xdg-user-dirs-update(1)
xdg-utils^rpm	xdg-desktop-icon(1), xdg-desktop-menu(1), xdg-mime(1), xdg-open(1), xdg-settings(1) and others `xdg-*`	all `xdg-*` commands are shell script
xdg-desktop-portal^rpm	A portal frontend service for Flatpak and other desktop containment frameworks	portals.conf(5)

basedir

Desktop base directories (basedir)

Environment variable	Dir (by default if not set)	System analogous
User directories
`XDG_CONFIG_HOME`	$HOME/.config	/etc
`XDG_CACHE_HOME`	$HOME/.cache	/var/cache
`XDG_DATA_HOME`	$HOME/.local/share	/usr/share
`XDG_STATE_HOME`	$HOME/.local/state	/var/lib
`XDG_RUNTIME_DIR`	/run/user/$UID set by pam_systemd(8)	user runtime files (sockets, named pipes, etc.) must be owned by the user with an access mode of 0700

Environment variable	Dir (by default if not set)
System directories
`XDG_DATA_DIRS`	/usr/local/share:/usr/share
`XDG_CONFIG_DIRS`	/etc/xdg
List of directories separated by `:` (analogous to `PATH`)

User directories are more important than system. When the same information is defined in multiple places the information defined relative to the more important base directory takes precedent:

1st) $HOME/.local/share 2nd) /usr/local/share 3rd) /usr/share

1st) $HOME/.config 2nd) /etc/xdg

Each xdg-* command (bash script) from xdg-utils^rpm package uses the following lines:

search="${XDG_DATA_HOME:-$HOME/.local/share}:${XDG_DATA_DIRS:-/usr/local/share:/usr/share}"
echo "$search"
search="${XDG_CONFIG_HOME:-$HOME/.config}:${XDG_CONFIG_DIRS:-/etc/xdg}"
echo "$search"

Desktop Entry

Desktop Entry specification describes desktop entries (configuration files) that provide information about a program, such name, icon, etc.

CLI commands to launch an application: gtk-launch(1)^rpm, gtk4-launch(1)^rpm, gio(1)^rpm or dex-autostart(1)^rpm.

$ gtk-launch org.gnome.Calculator.desktop   # with or without '.desktop' extension
$ gio launch /usr/share/applications/org.gnome.Calculator.desktop      # full path
$ dex-autostart /usr/share/applications/org.gnome.Calculator.desktop   # full path

[Desktop Entry]
Name=MediaInfo CLI
Type=Application

# # option 1
# Exec=sh -c "printf \\"Hello1\n\\";mediainfo --version;read -p \\"Press enter to exit\\""
# Terminal=true

# # option 2
# Exec=sh -c "printf \\"Hello2\n\\";mediainfo --version;\\$SHELL;"
# Terminal=true

# option 3
# gnome-terminal option '-e' is deprecated, use '--'
Exec=gnome-terminal -- sh -c "printf \\"Hello3\n\\";mediainfo --version;\\$SHELL;"

desktop-file-utils contains a few command line utilities for working with desktop entries. Package desktop-file-utils^rpm provides: desktop-file-edit(1), desktop-file-install(1), desktop-file-validate(1) and update-desktop-database(1).

$ desktop-file-validate $HOME/.local/share/applications/root.desktop
$ desktop-file-validate /usr/local/share/applications/root.desktop

autostart

Desktop application autostart

By placing an application's .desktop file in one of the autostart directories the application will be automatically launched during startup of the user's desktop environment after the user has logged in. Autostart directories:

$XDG_CONFIG_HOME/autostart/ ($HOME/.config/autostart/ user dir by default)
$XDG_CONFIG_DIRS/autostart/ (/etc/xdg/autostart/ system dir by default)

$ dex-autostart --autostart --dry-run   # list of all autostart programs

To disable a system entry, create an overriding entry containing Hidden=true. When the .desktop file has the Hidden key set to true, the .desktop file MUST be ignored. System desktop entries can be overridden by user desktop entries with the same filename.

Ak potrebujeme zakazat desktop application autostart napr. pre system /etc/xdg/autostart/xdg-user-dirs.desktop, vytvorime user $HOME/.config/autostart/xdg-user-dirs.desktop subor s rovnakym nazvom do ktoreho pridame Hidden=true key.

[Desktop Entry]
Type=Application
Hidden=true

NOTE Jednoduche zmazanie (alebo editovanie) suboru (napr. /etc/xdg/autostart/xdg-user-dirs.desktop) je len docasne a nevhodne riesenie. Pri dalsom system upgrade (alebo nejakej inej zmene) bude tento subor znova obnoveny.

xdg-user-dirs

xdg-user-dirs is a tool to help manage well known user directories like the Desktop folder or the Music folder.

https://www.freedesktop.org/wiki/Software/xdg-user-dirs/
https://wiki.archlinux.org/title/XDG_user_directories
man pages: xdg-user-dir(1), xdg-user-dirs-update(1), user-dirs.conf(5), user-dirs.defaults(5) and user-dirs.dirs(5) (all from xdg-user-dirs^rpm package)

Autostart desktop entry /etc/xdg/autostart/xdg-user-dirs.desktop pri kazdom login user spusta xdg-user-dirs-update(1). Tento program je konfigurovany systemovymi /etc/xdg/user-dirs.conf (user-dirs.conf(5)) a /etc/xdg/user-dirs.defaults (user-dirs.defaults(5)), resp. uzivatelskym $HOME/.config/user-dirs.dirs (user-dirs.dirs(5)).

Program xdg-user-dirs-update (autostart on user login) v pripade ak neexistuje subor $HOME/.config/user-dirs.dirs (napr. prve spustenie po novej instalacii) vytvori vsetky default dirs (konfiguracia v /etc/xdg/user-dirs.defaults) a zaroven vytvori aj uzivatelsky subor $HOME/.config/user-dirs.dirs. Ak uzivatel neskor vymaze niektoru nepotrebnu user dir (napr. $HOME/Music/) tak pri dalsom user login (alebo manualnom spusteni xdg-user-dirs-update) sa tato dir "vymaze" (nastavi sa na $HOME/) aj v user config file $HOME/.config/user-dirs.dirs.

$ rmdir Desktop/ Documents/ Music/ Pictures/ Public/ Templates/ Videos/   # keep only Downloads/
$ xdg-user-dirs-update

Osobne mi to pride cele zbytocne a kontraproduktivne. Zmazanie celeho package kvoli zavislostiam vsak nie je mozne. Navyse xdg-user-dirs-gtk^rpm (doplnok k xdg-user-dirs^rpm) ho integruje do prostredia Gnome a Gtk+ aplikacii.

icons

Icon Theme

Icon Naming

icon-theme contains the standard also references the default icon theme called hicolor.

https://www.freedesktop.org/wiki/Software/icon-theme/

On Fedora/RHEL the default dummy theme /usr/share/icons/default/index.theme inherits from the "Adwaita" theme /usr/share/icons/Adwaita/index.theme (adwaita-icon-theme^rpm), which in turn inherits from the "hicolor" theme /usr/share/icons/hicolor/index.theme (hicolor-icon-theme^rpm). The "hicolor" theme should always exist.

$ gsettings get org.gnome.desktop.interface icon-theme
'Adwaita'

Supported image file formats: PNG is the recommended bitmap format and SVG is for vectorized icons (optional). XPM is supported due to backwards compability reasons (not recommended). The extension must be .png, .svg or .xpm (lower case).

${XDG_DATA_HOME}:${XDG_DATA_DIRS}/icons/<theme>/<format>/<type>/<icon-name>
/usr/local/share/icons/hicolor/scalable/apps/root.svg
$HOME/.local/share/icons/root.svg     # (don't use obsolete dir $HOME/.icons/)

xdg-utils

xdg-utils is a set of tools that allows applications to easily integrate with the desktop environment of the user, regardless of the specific desktop environment that the user runs.

https://www.freedesktop.org/wiki/Software/xdg-utils/
https://wiki.archlinux.org/title/Xdg-utils
man pages: xdg-desktop-icon(1), xdg-desktop-menu(1), xdg-email(1), xdg-icon-resource(1), xdg-mime(1), xdg-open(1), xdg-screensaver(1) and xdg-settings(1) (all xdg-* commands are shell scripts).

Fontconfig

Fontconfig is a library for configuring and customizing font access. FreeType is a TrueType font rendering library based on this configuration.

https://www.freedesktop.org/wiki/Software/fontconfig/
https://wiki.archlinux.org/title/Font_configuration
man page: fonts-conf(5)^rpm (or to same: https://fontconfig.pages.freedesktop.org/fontconfig/fontconfig-user.html)
man page: FcPatternFormat(3)^rpm (or to same: https://fontconfig.pages.freedesktop.org/fontconfig/fontconfig-devel/#FCPATTERNFORMAT)
https://www.freedesktop.org/software/fontconfig/fontconfig-devel/fcpatternformat.html (to same as previous ?)

Fedora package fontconfig^rpm provides many command line utilities to manage and query fonts and the font configuration of the system: fc-cache(1), fc-cat(1), fc-conflist(1), fc-list(1), fc-match(1), fc-pattern(1), fc-query(1), fc-scan(1) and fc-validate(1).

MIME

Media Types (formerly known as MIME types)

The MIME Applications specification builds upon the shared MIME database and desktop entries to provide default applications.

Fedora package shared-mime-info^rpm provides shared MIME info database. The database is built from the XML file /usr/share/mime/packages/freedesktop.org.xml. The files in /usr/share/mime/ should not be directly edited.

Default applications for each MIME type are stored in mimeapps.list files. The lookup order for this file is as follows:

`$XDG_CONFIG_HOME/mimeapps.list`	$HOME/.config/mimeapps.list
`$XDG_CONFIG_DIRS/mimeapps.list`	/etc/xdg/mimeapps.list
`$XDG_DATA_HOME/applications/mimeapps.list`	$HOME/.local/share/applications/mimeapps.list for compatibility, deprecated
`$XDG_DATA_DIRS/applications/mimeapps.list`	/usr/local/share/applications/mimeapps.list /usr/share/applications/mimeapps.list
and `$desktop-mimeapps.list` for each above locations with higher priority	desktop (gnome, kde, xfce, etc.) specific files /usr/share/applications/gnome-mimeapps.list

$ XDG_UTILS_DEBUG_LEVEL=2 xdg-mime query default non/exist   # discover all the files (locations) that are scanned

NOTE Files defaults.list in these locations is now obsolete, deprecated.

Fedora contains 2 mimeapps.list files:

/usr/share/applications/gnome-mimeapps.list
/usr/share/applications/mimeapps.list

The system-wide association between MIME types and applications is generated from the *.desktop files provided by the packages (stored in the /usr/share/applications/ directory and subdirectories) and the update-desktop-database(1)^rpm parses their information and generates the /usr/share/applications/mimeinfo.cache file, that specifies for each MIME type the valid *.desktop files, i.e. applications.

$ file --mime-type screenshot.png 
screenshot.png: image/png
$ xdg-mime query filetype screenshot.png 
image/png
$ xdg-mime query default image/png 
org.gnome.eog.
$ gio mime image/png
Default application for “image/png”: org.gnome.eog.desktop
Registered applications:
	org.gnome.eog.desktop
Recommended applications:
	org.gnome.eog.desktop

$ xdg-mime query default audio/mp3
audacious.desktop
$ gio mime audio/mp3
Default application for “audio/mp3”: audacious.desktop
Registered applications:
	audacious.desktop
	vlc.desktop
Recommended applications:
	audacious.desktop
	vlc.desktop

$ xdg-mime query default audio/m3u
$ gio mime audio/m3u
Default application for “audio/m3u”: audacious.desktop
Registered applications:
    audacious.desktop
    vlc.desktop
    emacs.desktop
    libreoffice-writer.desktop
Recommended applications:
    audacious.desktop
    vlc.desktop

NOTE Matroska audio (*.mka), resp. video (*mkv) je aktualne vo Fedora MIME info databaze ako MIME type /usr/share/mime/audio/x-matroska.xml, resp. /usr/share/mime/video/x-matroska.xml, t.j. s prefixom x-, co znamena, ze tento typ suborov nie je v registrovany v IANA databaze. Medzi tym vsak Matroska format bol zaregistrovany v ramci IANA databazy a preto je mozne predpokladat, ze v buducich verziach shared-mime-info uz budu tieto subory bez x- prefixu.

TIP Useful Perl script mimeopen(1)^rpm or mimetype(1)^rpm.