Re: Breaking programs because a not yet implemented solution exists in theory

[Russ Allbery <rra@debian.org>]

Andreas Tille <andreas@an3as.eu> writes:

> Well, from my perspective I was bored the first time when xpdf came up
> when I was expecting evince.  After purging xpdf I learned that see does
> not find any pdf viewer.  Sorry if I did not realised any discussion
> seven monthes ago noch any one-line helpers.

> So were can I read about which one-liner should be added to what package
> to fix the problem you decided to force upon others. 

So, I don't have a one-line script, but I generally agree with Josselin
that maintaining the same information in two places is a bad idea.  The
basic idea of what needs to be done is to convert the information in the
desktop files into the equivalent of a /usr/lib/mime/packages file.

For example, /usr/share/applications/xpdf.desktop has:

[Desktop Entry]
Name=xpdf
GenericName=PDF viewer
Comment=View PDF files
Exec=xpdf
Icon=xpdf
Terminal=false
Type=Application
MimeType=application/pdf;
Categories=Viewer;Graphics;

/usr/lib/mime/packages/xpdf has:

application/pdf; /usr/bin/xpdf %s; test=test "$DISPLAY" != ""; description=Portable Document Format; nametemplate=%s.pdf; priority=6
application/x-pdf; /usr/bin/xpdf %s; test=test "$DISPLAY" != ""; description=Portable Document Format; nametemplate=%s.pdf; priority=6

Obviously, the first field comes straight from MimeType (and, in general,
from the list of values in MimeType).  I think one has to make the
assumption that one can add %s after Exec in order to load a file, since
the desktop entry doesn't have an equivalent of the command.  The test is
the same for any application that says Terminal=false.

The description and nametemplate don't come from the same place.  Those
come from /usr/share/mime/application/pdf.xml, and are the same for all
application/pdf entries.

The priority is a more interesting problem.  I'm not sure how the desktop
specification assigns priorities when multiple applications can handle the
same MIME type.

This doesn't look like a trivial tool, but it looks possible to write.
What I'd do is teach update-mime how to handle desktop files as well and
then add a trigger for changes in /usr/share/applications.

-- 
Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>