From 731782ec542bfdd9d29bd9a614e7aae8c5b9f6fc Mon Sep 17 00:00:00 2001 From: Petter Reinholdtsen Date: Sun, 5 Jun 2016 08:23:44 +0200 Subject: [PATCH] New post. --- blog/data/2016-06-05-open-your-files.txt | 109 +++++++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 blog/data/2016-06-05-open-your-files.txt diff --git a/blog/data/2016-06-05-open-your-files.txt b/blog/data/2016-06-05-open-your-files.txt new file mode 100644 index 0000000000..2a66039707 --- /dev/null +++ b/blog/data/2016-06-05-open-your-files.txt @@ -0,0 +1,109 @@ +Title: A program should be able to open its own files on Linux +Tags: english, debian +Date: 2016-06-05 08:30 + +

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 a given files MIME type. 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. :)

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