KDE's MIME magic (KMimeMagic) database (format)

[David Faure]

On Sunday 18 February 2007, Daniel Leidert wrote:
> > So this will only work if both conflicting mimetypes don't have Patterns=,
> > or if they have X-KDE-PatternsAccuracy=50 (any number < 100).
> > Feel free to submit a patch for kdelibs/mimetypes which adds the latter to all
> > the mimetypes with "not so deterministic extensions".
> Ok. I will have this in mind. So both need to have this line or no
> pattern, if I understand you.
Yes.

> Yes. It searches from a given offset in the given offset-range length.
OK.

> > Interesting; especially since xdg mime doesn't support that, does it?
> 
> It supports. But it doesn't use the search type. Instead it allows to
> give an offset range "x:y" in the offset attribute of the match element.
> I used the search-type of file's magic.mime file syntax, because the
> file syntax does not contain something like offset_start:offset_end. The
> only thing, that fits this idea, is the search type.
Yes, same functionality, different syntax.

> But also byte|short|long|leshort|lelong|beshort|belong?
Yes. And date/bedate/ledate.

> > > I've attached the current database to this 
> > > mail, so that you can have a look at your own for the used syntax. To
> > > test, I simply copied it to ~/.kde/share/mimelnk.
> > You can put it under <prefix or kdehome>/share/config/magic/chemical.magic (filename doesn't matter, extension does), instead.
> > This is how to install kmimemagic snippets.
> 
> Ah. In Debian /etc/kde3/magic for system files. Many thanks. Didn't know
> that. I always thought, you cannot extend the database. I should add
> this information to the freedesktop.org Wiki, so it will not be lost :)
Good idea (although it's kde-specific, not fdo related)

> So, I should create .desktop files for the aliases too and simply add
> the X-KDE-IsAlso there, without any pattern?
Yes.

> > I know, this isn't really like aliases - if an application declares that it supports only the 
> > subclass/alias then it won't be launched for a file that has the canonical type.
> > This is why we use the chosen canonical type in all application desktop files,
> > and the alias is really only for the case where the 'wrong mimetype name' is being found,
> > e.g. as returned by apache.
> Ok. Understood. This is, how it should work.

Interesting ;) This makes me wonder if I should really implement the xdg-mime aliases 
as complete equivalent aliases in kde4, or just as subclasses like we do already ;)
But that might not be spec-compliant.

> BTW, is there somewhere an official documentation of the X-KDE keys
> in .desktop files? I mostly found discussion on this list, but no
> complete documentation.
Not really, unfortunately.
For Type=Application files, the best documentation (well, list) is <prefix>/share/servicetypes/application.desktop
For mimetype files, there are really just three: X-KDE-AutoEmbed, X-KDE-text, and X-KDE-PatternsAccuracy.
(I still need to find a replacement for the first one in kde4...)

-- 
David Faure, faure at kde.org, sponsored by Trolltech to work on KDE,
Konqueror (http://www.konqueror.org), and KOffice (http://www.koffice.org).