How can I register a custom protocol with xdg?

Question

I've been struggling this morning trying to associate an application with a custom protocol, namely emacsclient and org-protocol.

I'm calling this protocol from a webbrowser bookmarklet, and I get the following behaviour :

In chromium,
the "Launch Application" dialog comes up, and calls xdg-open org-protocol://... which ends up firing a new chromium frame.

In firefox,
I've tried setting network.protocol-handler.app.org-protocol to an empty string or my emacsclient path, anyhow I get the following error message :
"Firefox doesn't know how to open this address, because the protocol (org-protocol) isn't associated with any program" without even showing any external application selection dialog.

I'm not using any desktop environment, so I need to make this work strictly with xdg, however, despite reading the shared mime info spec etc, I still can't fathom a working configuration.

Answer 1

The XDG method: Create an emacsclient.desktop file that handles the x-scheme-handler/org-protocol MIME type:

[Desktop Entry]
Name=Emacs Client
Exec=emacsclient %u
Icon=emacs-icon
Type=Application
Terminal=false
MimeType=x-scheme-handler/org-protocol;

(Note the MimeType= line above, which is for org-protocol: URIs.)

Put the file in ~/.local/share/applications or /usr/local/share/applications.

Answer 2

At least in Fedora 13 and various Debian-based distros xdg-open opens all URLs that don't have a file:// scheme in a browser if it doesn't run in a supported desktop environment. The way it tries to detect which browser to use depends on the distribution.

As xdg-open is just a shell script you can easily adapt it to your needs.