enlightenment/doc/FDO.txt

Enlightenment DR17 uses freedesktop.org .desktop files according to the
XDG Desktop Entry Specification version 0.9.4, icon themes according to
the XDG Icon Theme Specification version 0.11, and menus according to
the Desktop Menu Specification version 0.92.  Everything is searched for
in paths specified by XDG Base Directory Specification version 0.6.
There are some extensions and gotchas though.


Paths.

The spec wants us to run gnome-config and kde-config several times at
startup.  This is currently #if'ed out and replaced with guesses.  Lots
of guesses is a lot quicker than actually running those programs, and
often is good enough.  The plan is to have an idle process run those
programs and fix the guesses.

A lot of distro specific quirks can be solved by adding more directories
and directory snippets to the ecore_desktop_paths code.  The process of
eliminating non existing directories is quick, and only done once at
start up.


.desktop.

Some extension fields are defined as allowed by the specification. 

X-Enlightenment-IconPath is used to specify an absolute or relative path to
an icon file.  If it exists it overrides any other icon specifications.

X-Enlightenment-IconClass is used to specify a list of icon classes. 
This is the same information that was in .eaps as app/icon/class, and is
used the same way if it exists.  Obviously any .desktop file that comes
with packages outside of E is unlikely to have that field.  One further
twist is that if the icon classes are not found in edje, then icon class
becomes a list of icons to search in the standard FDO way.

The standard Icon field is also treated differently.  If it contains a /
it is considered to be an absolute path, or a path relative to the
location of the .desktop file.  Otherwise, if no icon class was
specified in the .desktop file, then the Icon, Exec, and Categories
fields are used in that order to build an icon class.  Everything but
the Icon field is lower cased.

This means that for standard .desktop files, with out the extension
fields, icons in the E theme are searched for first, then icons are
searched for in the usual FDO way, unless the Icon field specifies a
path, then it is simply used with no searching.  Converted .eaps should
just copy the app/icon/class data to the X-Enlightenment-IconClass
field.

X-Enlightenment-WindowName, X-Enlightenment-WindowTitle, 
X-Enlightenment-WindowRole, and X-Enlightenment-WaitExit are just the same
as their namesakes in .eaps.


Icon theme.

.edj files are searched for before the other types of icon file.  The
"icon" group is used to specify the graphics for the icon.  It is up to
the code using the result to allow full edje interactions and
animations, and people that write that code are encouraged to support it
all.


Menus.

The most complex, and thus the most problematic of the specifications. 
The general philosophy is to err on the side of caution, giving the user
more apps in their menus rather than less.  Even if that means some
duplicates and some things that aren't really apps.

There is often a .hidden menu, it contains various types of things. 
Some of those things are supposed to be moved into proper menus by the
menu moving part of the spec.  The menu moving code has not been
implemented yet. Following the above philosophy, it is shown to the
user.

Slackware and probably other distros use parent style menu merging. 
Initially I did not write code to support that for two reasons.  The
specification is confusing, and it takes some digging and cross
referencing other specs to sort out what it actually means.  The other
reason is that distros available to me at the time for testing did not
use parent style menu merging, so there was no way to test it properly. 
Now that I know of at least one distro that uses them, it's worthwhile
writing the code, and installing slackware under QEMU for testing.