Saturday, March 31, 2018¶

Defining Davlink as a custom URL protocal handler¶

The Linux instructions on the shotgunsoftware.com seem obsolete, here are newer ones. Thanks also to to the discussion on Where are file associations stored?

I did the following experiment.

I created an executable file /home/luc/bin/davlink.sh with this content:

echo "<body>Hello world </body>"
date >> /home/luc/bin/davlink.log

In /usr/share/applications I added a file davlink.desktop with this content:

[Desktop Entry]
Encoding=UTF-8
Version=1.0
Type=Application
Terminal=false
Exec=/home/luc/bin/davlink.sh %u
Name=DavLink
Comment=DavLink handler
Icon=
Categories=Application;Network;
MimeType=x-scheme-handler/davlink;

In my mimeapps.list file (the one in ~/.config, not the one in ~/.local/share/applications), I added:

x-scheme-handler/davlink=davlink.desktop;

I ran update-desktop-database to build the cache database of MIME types handled by desktop files.

I point FireFox to davlink://foo.txt and get this dialog:

Looks as if my previous configs were partly useless since FF still manages its own list of associations.

Anyway: the log file shows that the script is getting executed. But the browser does not get any feedback. It just launches the application and does not return any response. The process is similar to downloading a file, except that there is no file being downloaded before launching the application.

TIL:

Configuring a custom URL handler can be tricky, but with correct documentation it should be an acceptable requirement.
We can use custom url handlers for davlink immediately, but for eidreader we need a system where the local script can send back a response to the browser. That’s more complex. This thread indicates a possible solution: our eidreader.sh file would post its information to the Lino server where it gets stored in the file system or a temporary database table using the client’s IP address, timestamp and national_id. And the “Read eID” button would do a series of two things: (1) invoke eidreader.sh and (2) read from the file system or temporary database table. Not yet sure how to handle the waiting time.