Bug#742532: Document media type declarations
Package: debian-policy
Version: 3.9.6.0
Dear developers,
To reduce clutter in the BTS log, I am opening a new bug for the second half of
the proposal "Document media type declarations" by Charles Plessy in #707851,
since I did not find specific objections registered about it.
I join the patch. There is one undefined reference to "desktop entries" due to
the cut that I will sort out before doing a release.
Please check and second it again.
Sorry for the delay and duplication, and thanks to Charles for having drafted it.
Cheers,
--
Bill. <ballombe@debian.org>
Imagine a large red swirl here.
diff --git a/policy.sgml b/policy.sgml
index f4e4281..3ab5912 100644
--- a/policy.sgml
+++ b/policy.sgml
@@ -8092,42 +8092,109 @@ Reloading <var>description</var> configuration...done.
<heading>Multimedia handlers</heading>
<p>
- MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
- is a mechanism for encoding files and data streams and
- providing meta-information about them, in particular their
- type (e.g. audio or video) and format (e.g. PNG, HTML,
- MP3).
+ Media types (formerly known as MIME types, Multipurpose Internet Mail
+ Extensions, RFCs 2045-2049) is a mechanism for encoding files and
+ data streams and providing meta-information about them, in particular
+ their type and format (e.g. <tt>image/png</tt>, <tt>text/html</tt>,
+ <tt>audio/ogg</tt>).
</p>
<p>
- Registration of MIME type handlers allows programs like mail
+ Registration of media type handlers allows programs like mail
user agents and web browsers to invoke these handlers to
- view, edit or display MIME types they don't support directly.
+ view, edit or display media types they don't support directly.
</p>
<p>
- Packages which provide programs to view/show/play, compose, edit or
- print MIME types should register them as such by placing a file in
- <manref name="mailcap" section="5"> format (RFC 1524) in the directory
- <file>/usr/lib/mime/packages/</file>. The file name should be the
- binary package's name.
+ There are two overlapping systems to associate media types to programs
+ which can handle them. The <em>mailcap</em> system is found on a
+ large number of Unix systems. The <em>FreeDesktop</em> system is
+ aimed at Desktop environments. In Debian, FreeDesktop entries are
+ automatically translated in mailcap entries, therefore packages
+ already using desktop entries should not use the mailcap system
+ directly.
</p>
- <p>
- The <package>mime-support</package> package provides the
- <prgn>update-mime</prgn> program, which integrates these
- registrations in the <file>/etc/mailcap</file> file, using dpkg
- triggers<footnote>
- Creating, modifying or removing a file in
- <file>/usr/lib/mime/packages/</file> using maintainer scripts will
- not activate the trigger. In that case, it can be done by calling
- <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
- the maintainer script after creating, modifying, or removing
- the file.
- </footnote>.
- Packages using this facility <em>should not</em> depend on,
- recommend, or suggest <prgn>mime-support</prgn>.
- </p>
+ <sect1 id="media-types-freedesktop">
+ <heading>Registration of media type handlers with desktop entries</heading>
+
+ <p>
+ Packages shipping an application able to view, edit or point to
+ files of a given media type, or open links with a given URI scheme,
+ should list it in the <tt>MimeType</tt> key of the application's
+ <qref id="menus">desktop entry</qref>. For URI schemes,
+ the relevant MIME types are <tt>x-scheme-handler/*</tt> (e.g.
+ <tt>x-scheme-handler/https</tt>).
+ </p>
+ </sect1>
+
+ <sect1 id="mailcap">
+ <heading>Registration of media type handlers with mailcap entries</heading>
+
+ <p>
+ Packages that are not using desktop entries for registration should
+ install a file in <manref name="mailcap" section="5"> format (RFC
+ 1524) in the directory <file>/usr/lib/mime/packages/</file>. The
+ file name should be the binary package's name.
+ </p>
+
+ <p>
+ The <package>mime-support</package> package provides the
+ <prgn>update-mime</prgn> program, which integrates these
+ registrations in the <file>/etc/mailcap</file> file, using dpkg
+ triggers<footnote>
+ Creating, modifying or removing a file in
+ <file>/usr/lib/mime/packages/</file> using maintainer scripts will
+ not activate the trigger. In that case, it can be done by calling
+ <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
+ the maintainer script after creating, modifying, or removing
+ the file.
+ </footnote>.
+
+ <p>
+ Packages installing desktop entries should not install mailcap
+ entries for the same program, because the
+ <package>mime-support</package> package already reads desktop
+ entries.
+ </p>
+
+ <p>
+ Packages using these facilities <em>should not</em> depend on,
+ recommend, or suggest <prgn>mime-support</prgn>.
+ </p>
+ </sect1>
+
+ <sect1 id="file-media-type">
+ <heading>Providing media types to files</heading>
+
+ <p>
+ The media type of a file is discovered by inspecting the file's
+ extension or its <manref name="magic" section="5"> pattern, and
+ interrogating a database associating them with media types.
+ </p>
+
+ <p>
+ To support new associations between media types and files, their
+ characteristic file extensions and magic patterns should be
+ registered to the IANA (Internet Assigned Numbers Authority). See
+ <url id="http://www.iana.org/assignments/media-types";> and RFC 6838
+ for details. This information will then propagate to the systems
+ discovering file media types in Debian, provided by the
+ <package>shared-mime-info</package>,
+ <package>mime-support</package> and <package>file</package>
+ packages. If registration and propagation can not be waited for,
+ support can be asked to the maintainers of the packages mentioned
+ above.
+ </p>
+
+ <p>
+ For files that are produced and read by a single application, it
+ is also possible to declare this association to the
+ <em>Shared MIME Info</em> system by installing in the directory
+ <file>/usr/share/mime/packages</file> a file in the XML format
+ specified at <url id="http://standards.freedesktop.org/shared-mime-info-spec/latest/";>.
+ </p>
+ </sect1>
</sect>
<sect>
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