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List:       kde-core-devel
Subject:    Re: KDE's MIME magic (KMimeMagic) database (format)
From:       David Faure <faure () kde ! org>
Date:       2007-02-18 19:52:24
Message-ID: 200702182052.24846.faure () kde ! org
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On Saturday 17 February 2007, Daniel Leidert wrote:
> For KDE 3 (4 will hopefully support the shared-mime-info db) 
Yes, it will, I'm working on this as we speak ;)

> I already implemented to 
> output .desktop files for every (supported) MIME type. Now I wanted to
> extend the magic database (mimelnk/magic) to solve possible conflicts
> (e.g. chemical/x-daxlight-smiles and application/smil use the same file
> extension, ditto for e.g. chemical/x-pdb and application/vnd.palm). 
You know that in KDE 3, extensions are always considered first, right?
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".

> So I 
> wrote a stylesheet, that produces an output, usable as file(1)'s
> magic.mime database (works perfectly for `file -i'). From what I read I
> thought, that the KMimeMagic uses the same format. But that seems to be
> wrong. I can make konqueror crash with such a magic-database. I get the
> following errors on command line (just a few of them):
> 
> kio (KMimeMagic): ERROR: parse: type search/76  NOTE    chemical/x-cmtx invalid

Well, KMimeMagic is based upon an old version of file(1). That version didn't have \
support for "search/". I never saw that before; it's for searching from a given \
offset instead of expecting data at that offset? Interesting; especially since xdg \
mime doesn't support that, does it? (I haven't looked into the "magic" part of xdg \
mime yet).

> So what is supported in the KMimeMagic database format compared to
> file's magic(.mime) database? 
string, but not search.

> 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.

> And a second problem: What is 'X-KDE-IsAlso' compared to the
> shared-mime-info database format? From what I read, I think it's similar
> to <sub-class-of type="..."/>. 
Yes.

> But how do you handle aliases then?
The same way. Choose which one is the "canonical" type, and declare the other type
as a subclass (X-KDE-IsAlso) of it.
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.

> CCing the freedesktop.org xdg-list
CC removed since this discussion is mostly about the kde-specific stuff ;)

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


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