Proposal for a MIME mapping spec

Waldo Bastian bastian at
Mon Jul 19 17:32:13 EEST 2004

Hash: SHA1

On Thursday 08 July 2004 19:50, Jonathan Blandford wrote:
> Thomas Leonard <tal00r at> writes:
> > > The defaults are first read in
> > > $XDG_DATA_DIRS/applications/defaults.list.  It is expected that these
> > > defaults are set solely by the distributor of the system.  Then, a
> > > $MIME_PREFS_LIST environment variable is checked for other preferred
> > > applications.  This is expected to be set by a sysadmin providing their
> > > own defaults.  Additionally, each desktop should prepend its own
> > > defaults to this variable.
> >
> > Why is this config information in $XDG_DATA_DIRS? Surely it should be in
> > $XDG_CONFIG_DIRS? MIME_PREFS_LIST seems unnecessary, since desktops can
> > already add to XDG_CONFIG_DIRS (ROX-Session adds
> > /uri/0install/ to the choices
> > search path, for example).
> I would expect there to be a one-to-one mapping between the desktop
> directories and the defaults.list, and thus it's XDG_DATA_DIRS.
> MIME_PREFS_LIST might be unnecessary -- I'm not fully sold on it yet.
> If we think that adding to XDG_DATA_DIRS is sufficient for this, then we
> can just use that.
> > > Then, $XDG_DATA_CONFIG/mime/defaults.list is checked for user-specific
> > > defaults.  Finally, it is expected that each desktop will have their
> > > own (optional) user-specific desktop file.
> >
> Grr.. XDG_CONFIG_DIRS.  I get these environment variables confused.

You write "Finally, it is expected that each desktop will have their own 
(optional) user-specific desktop file." isn't that what 
$XDG_CONFIG_HOME/mime/defaults.list is supposed to take care of? If you use 
an environment specific file you end up with GNOME and KDE applications 
having different views of the world.

Assuming that $XDG_CONFIG_HOME/mime/defaults.list should be used (at least 
primarily) to record the users preferences, I would like to add the following 
note wrt behavior in the face of no defined default:

"When activation of a file of a certain MIME Type is required and no default 
application has been specified for this MIME Type in any of the default.list 
files the following steps should be taken:
1. A list of all suitable applications that can handle this MIME Type is 
constructed. The information from the mimeinfo.cache files can be used for 
2. If the list contains only a single application this application will become 
the default handler for this MIME Type and is registered as such in 
3. If the list contains multiple applications the user should be prompted to 
select the application that should be used by default. This choice should 
then be registered in $XDG_CONFIG_HOME/mime/defaults.list
4. If no suitable application is found at all, the user may be prompted to 
provide an application.
[4a] Such application may be registered in $XDG_CONFIG_HOME/mime/defaults.list 
despite the fact that the application's .desktop file does not list the MIME 
[4b] Such application may be registered in $XDG_CONFIG_HOME/mime/defaults.list 
after it is ensured that the MIME Type is listed in the 
applications's .desktop file. In case the original .desktop file is not 
editable this may require that an editable copy of the .desktop file is 
created under $XDG_DATA_HOME/applications first."

With either variant [4a] or variant [4b].


There is also the scenario that an application is chosen that is restricted to 
a particular environment (e.g. due to OnlyShowIn=KDE) To prevent flip-flop 
behavior I think that if default.list specifies an application that is for 
some reason not suitable (e.g. wrong environment) a new default application 
should be selected as described above and the resulting default application 
should then be added after, and in addition to, the already listed default 

Assume the application gedit which as an application .desktop file known as 
gnome-gedit.desktop that contains OnlyShowIn=GNOME
Also assume the application KEdit which as an application .desktop file known 
as kde-KEdit.desktop that contains OnlyShowIn=KDE. 

In KDE the user is prompted for a default handler for text/plain and selects 
KEdit. This choice is registered in $XDG_CONFIG_HOME/mime/defaults.list:

Now the user runs GNOME and opens a text/file, KEdit is not used because of 
OnlyShowIn=KDE, the user is prompted for a default handler for text/plain and 
selects gedit. This choice is now registered in  
$XDG_CONFIG_HOME/mime/defaults.list as follows:

- -- 
bastian at  |   KDE Community World Summit 2004  |  bastian at
bastian at  | 21-29 August, Ludwigsburg, Germany |  bastian at
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