Differences

This shows you the differences between two versions of the page.

--- doc:appunti:linux:tux:mimetype [2020/09/13 19:42] – [Application associated to a MIME Type] niccolo
+++ doc:appunti:linux:tux:mimetype [2020/09/23 21:42] – [Application associated to a MIME Type] niccolo
@@ Line 153: / Line 153: @@
 ===== Application associated to a MIME Type =====
-To view if there is an application associated with our custom MIME Type, we can run the following command:
+To view if there is an application associated with our custom MIME Type, we can run the following command. No result is returned, as we can expect:
 <code>
@@ Line 159: / Line 159: @@
 </code>
-No result is returned, as we can expect.
+We check also the behaviour of the **Firefox** browser, we prepare an HTML file containing this (notice the **anchor** tag uses the **type** attribute to declare the proper MIME type):
+<code xml>
+<a href="playlist.m3u" type="application/x-image-playlist">Image Slideshow</a>
+</code>
+Once clicked the link, Firefox displays the //Open with...// dialog box suggesting to use **VLC** to open the **MPEG Audio URL**.  If you click over the //Other...// option, Firefox says **No applications found for "M3U Images Playlist" files**. The MIME Type is recognized, but the application to handle it is unknown.
+Now we prepare a file and save it as **/usr/local/share/applications/photo-reframe.desktop**:
+<file>
+[Desktop Entry]
+# The format of this file is specified at
+# http://standards.freedesktop.org/desktop-entry-spec/1.0/
+# The entries are in the order they are listed in version 1.0
+Type=Application
+# This is the version of the spec for this file, not the application version.
+Version=1.0
+Name=Photo-Reframe
+GenericName=Image Viewer
+Comment=Slideshow with on-the-fly image cropping
+Icon=image
+TryExec=photo-reframe
+Exec=photo-reframe --fullscreen --play %f
+Terminal=false
+MimeType=application/x-image-playlist;
+# Category entry according to:
+# http://standards.freedesktop.org/menu-spec/1.0/
+Categories=Graphics;2DGraphics;RasterGraphics;Qt;
+</file>
+then we run the **update-desktop-database** over that directory (it will update the **mimeinfo.cache** file in the same directory):
+<code>
+update-desktop-database /usr/local/share/applications/
+</code>
+Something good has happened; the system knows how to handle that MIME type:
+<code>
+xdg-mime query default application/x-image-playlist
+photo-reframe.desktop
+</code>
+After this step, Firefox suggests to use **Photo-Reframe (default)** to handle the link, you can check the box **Do this automatically for files like this from now on** and the associated application will be launched automatically whenever you will click over a link like this. Only after this association, you can open the Firefox **Preferences** => **Applications** and browse for the //M3U Images Playlist// and assign the preferred action.
+**NOTICE**: You may need to use **Shift-Click** to force the reloading of the link, otherwise Firefox may get the object from the cache, where the MIME type is cached too.
+===== Useless recipes =====
+There are many recipes to add a new MIME Type and an associated applications, many of them suggest to edit some system files. In our experience it is **absolutely useless to modify** the following files:
+  * /etc/mailcap
+  * /etc/mime.types
+  * $HOME/.mozilla/firefox/<profile>.default/mimeTypes.rdf
+  * $HOME/.mozilla/firefox/<profile>.default/handlers.json
+===== Opening local files from an HTTP page =====
+For security reasons a web browser does not allow to open a **%%file://%%** link from a page loaded via a network protocolo, like **%%http://%%**. This is obvious because you don't want to allow a remote sito to fiddle with objects stored on your local disk. But for our application we need this indeed: a page loaded from **%%http://localhost/gallery.php%%** must execute a local program passing a local file path to it, something like **/home/data/directory/playlist.m3u**.
+The link on the HTML page will look something like this:
+<code html>
+<a href="file:///home/data/directory/playlist.m3u">
+    <img src="directory/folder.jpg">
+</a>
+</code>
+To bypass the Firefox restriction, you have to create an **user.js** file in your profile directory, something like **$HOME/.mozilla/firefox/3e4ghyw2.default/user.js** (tested with Firefox 68.4):
+<code javascript>
+user_pref("capability.policy.policynames", "localfilelinks");
+user_pref("capability.policy.localfilelinks.sites", "http://localhost");
+user_pref("capability.policy.localfilelinks.checkloaduri.enabled", "allAccess");
+</code>
 ===== Web References =====
@@ Line 166: / Line 243: @@
   * **[[https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types|MIME types (IANA media types)]]**
   * **[[https://www.december.com/html/spec/mime.html|MIME Types]]**
+  * **[[http://kb.mozillazine.org/Links_to_local_pages_do_not_work|Links to local pages do not work]]**