- <div class="title"><a href="http://people.skolelinux.org/pere/blog/Using_appstream_in_Debian_to_locate_packages_with_firmware_and_mime_type_support.html">Using appstream in Debian to locate packages with firmware and mime type support</a></div>
- <div class="date"> 4th February 2016</div>
- <div class="body"><p>The <a href="https://wiki.debian.org/DEP-11">appstream system</a>
-is taking shape in Debian, and one provided feature is a very
-convenient way to tell you which package to install to make a given
-firmware file available when the kernel is looking for it. This can
-be done using apt-file too, but that is for someone else to blog
-about. :)</p>
-
-<p>Here is a small recipe to find the package with a given firmware
-file, in this example I am looking for ctfw-3.2.3.0.bin, randomly
-picked from the set of firmware announced using appstream in Debian
-unstable. In general you would be looking for the firmware requested
-by the kernel during kernel module loading. To find the package
-providing the example file, do like this:</p>
-
-<blockquote><pre>
-% apt install appstream
-[...]
-% apt update
-[...]
-% appstreamcli what-provides firmware:runtime ctfw-3.2.3.0.bin | \
- awk '/Package:/ {print $2}'
-firmware-qlogic
-%
-</pre></blockquote>
-
-<p>See <a href="https://wiki.debian.org/AppStream/Guidelines">the
-appstream wiki</a> page to learn how to embed the package metadata in
-a way appstream can use.</p>
-
-<p>This same approach can be used to find any package supporting a
-given MIME type. This is very useful when you get a file you do not
-know how to handle. First find the mime type using <tt>file
---mime-type</tt>, and next look up the package providing support for
-it. Lets say you got an SVG file. Its MIME type is image/svg+xml,
-and you can find all packages handling this type like this:</p>
-
-<blockquote><pre>
-% apt install appstream
-[...]
-% apt update
-[...]
-% appstreamcli what-provides mimetype image/svg+xml | \
- awk '/Package:/ {print $2}'
-bkchem
-phototonic
-inkscape
-shutter
-tetzle
-geeqie
-xia
-pinta
-gthumb
-karbon
-comix
-mirage
-viewnior
-postr
-ristretto
-kolourpaint4
-eog
-eom
-gimagereader
-midori
+ <div class="title"><a href="http://people.skolelinux.org/pere/blog/A_program_should_be_able_to_open_its_own_files_on_Linux.html">A program should be able to open its own files on Linux</a></div>
+ <div class="date"> 5th June 2016</div>
+ <div class="body"><p>Many years ago, when koffice was fresh and with few users, I
+decided to test its presentation tool when making the slides for a
+talk I was giving for NUUG on Japhar, a free Java virtual machine. I
+wrote the first draft of the slides, saved the result and went to bed
+the day before I would give the talk. The next day I took a plane to
+the location where the meeting should take place, and on the plane I
+started up koffice again to polish the talk a bit, only to discover
+that kpresenter refused to load its own data file. I cursed a bit and
+started making the slides again from memory, to have something to
+present when I arrived. I tested that the saved files could be
+loaded, and the day seemed to be rescued. I continued to polish the
+slides until I suddenly discovered that the saved file could no longer
+be loaded into kpresenter. In the end I had to rewrite the slides
+three times, condensing the content until the talk became shorter and
+shorter. After the talk I was able to pinpoint the problem –
+kpresenter wrote inline images in a way itself could not understand.
+Eventually that bug was fixed and kpresenter ended up being a great
+program to make slides. The point I'm trying to make is that we
+expect a program to be able to load its own data files, and it is
+embarrassing to its developers if it can't.</p>
+
+<p>Did you ever experience a program failing to load its own data
+files from the desktop file browser? It is not a uncommon problem. A
+while back I discovered that the screencast recorder
+gtk-recordmydesktop would save an Ogg Theora video file the KDE file
+browser would refuse to open. No video player claimed to understand
+such file. I tracked down the cause being <tt>file --mime-type</tt>
+returning the application/ogg MIME type, which no video player I had
+installed listed as a MIME type they would understand. I asked for
+<a href="http://bugs.gw.com/view.php?id=382">file to change its
+behavour</a> and use the MIME type video/ogg instead. I also asked
+several video players to add video/ogg to their desktop files, to give
+the file browser an idea what to do about Ogg Theora files. After a
+while, the desktop file browsers in Debian started to handle the
+output from gtk-recordmydesktop properly.</p>
+
+<p>But history repeats itself. A few days ago I tested the music
+system Rosegarden again, and I discovered that the KDE and xfce file
+browsers did not know what to do with the Rosegarden project files
+(*.rg). I've reported <a href="http://bugs.debian.org/825993">the
+rosegarden problem to BTS</a> and a fix is commited to git and will be
+included in the next upload. To increase the chance of me remembering
+how to fix the problem next time some program fail to load its files
+from the file browser, here are some notes on how to fix it.</p>
+
+<p>The file browsers in Debian in general operates on MIME types.
+There are two sources for the MIME type of a given file. The output from
+<tt>file --mime-type</tt> mentioned above, and the content of the
+shared MIME type registry (under /usr/share/mime/). The file MIME
+type is mapped to programs supporting the MIME type, and this
+information is collected from
+<a href="https://www.freedesktop.org/wiki/Specifications/desktop-entry-spec/">the
+desktop files</a> available in /usr/share/applications/. If there is
+one desktop file claiming support for the MIME type of the file, it is
+activated when asking to open a given file. If there are more, one
+can normally select which one to use by right-clicking on the file and
+selecting the wanted one using 'Open with' or similar. In general
+this work well. But it depend on each program picking a good MIME
+type (preferably
+<a href="http://www.iana.org/assignments/media-types/media-types.xhtml">a
+MIME type registered with IANA</a>), file and/or the shared MIME
+registry recognizing the file and the desktop file to list the MIME
+type in its list of supported MIME types.</p>
+
+<p>The <tt>/usr/share/mime/packages/rosegarden.xml</tt> entry for
+<a href="http://www.freedesktop.org/wiki/Specifications/shared-mime-info-spec">the
+Shared MIME database</a> look like this:</p>
+
+<p><blockquote><pre>
+<?xml version="1.0" encoding="UTF-8"?>
+<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
+ <mime-type type="audio/x-rosegarden">
+ <sub-class-of type="application/x-gzip"/>
+ <comment>Rosegarden project file</comment>
+ <glob pattern="*.rg"/>
+ </mime-type>
+</mime-info>
+</pre></blockquote></p>
+
+<p>This states that audio/x-rosegarden is a kind of application/x-gzip
+(it is a gzipped XML file). Note, it is much better to use an
+official MIME type registered with IANA than it is to make up ones own
+unofficial ones like the x-rosegarden type used by rosegarden.</p>
+
+<p>The desktop file of the rosegarden program failed to list
+audio/x-rosegarden in its list of supported MIME types, causing the
+file browsers to have no idea what to do with *.rg files:</p>
+
+<p><blockquote><pre>
+% grep Mime /usr/share/applications/rosegarden.desktop
+MimeType=audio/x-rosegarden-composition;audio/x-rosegarden-device;audio/x-rosegarden-project;audio/x-rosegarden-template;audio/midi;
+X-KDE-NativeMimeType=audio/x-rosegarden-composition
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