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.
+
+
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 file --mime-type
+returning the application/ogg MIME type, which no video player I had
+installed listed as a MIME type they would understand. I asked for
+file to change its
+behavour 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.
+
+
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 the
+rosegarden problem to BTS 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.
+
+
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
+file --mime-type 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
+the
+desktop files 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
+MIME type registered with IANA), 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.
+
+
The /usr/share/mime/packages/rosegarden.xml entry for
+the
+Shared MIME database look like this:
+
+
+<?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>
+
+
+
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.
+
+
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:
+
+
+% 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
+%
+
+
+
The fix was to add "audio/x-rosegarden;" at the end of the
+MimeType= line.
+
+
If you run into a file which fail to open the correct program when
+selected from the file browser, please check out the output from
+file --mime-type for the file, ensure the file ending and
+MIME type is registered somewhere under /usr/share/mime/ and check
+that some desktop file under /usr/share/applications/ is claiming
+support for this MIME type. If not, please report a bug to have it
+fixed. :)
+
