How to send a string to a gnome-shell extension? - dbus

Question

I think D-Bus should be used. Basically, I want something like that — https://wiki.gnome.org/Gjs/Examples/DBusClient — but the other way round.
In the extension, there would be a function:
function f(s) { doSomethingWithS; }
And this function would be called after running:
$ <something> "abc"
… in the terminal, with s == "abc".
After suggestions from #Jasper and #owen at #gnome-shell on irc.gnome.org, I adapted some code from https://github.com/GNOME/gnome-shell/blob/master/js/ui/magnifierDBus.js:
const St = imports.gi.St;
const Gio = imports.gi.Gio;
const Lang = imports.lang;
const Main = imports.ui.main;
let text;
function init() {
text = new St.Label({ text: "0:0", style_class: 'panel-text' });
}
function enable() {
Main.panel._rightBox.insert_child_at_index(text, 0);
}
function disable() {
Main.panel._rightBox.remove_child(text);
}
const TextInTaskBarIface = '<node> \
<interface name="com.michalrus.TextInTaskBar"> \
<method name="setText"> \
<arg type="s" direction="in" /> \
</method> \
</interface> \
</node>';
const TextInTaskBar = new Lang.Class({
Name: 'TextInTaskBar',
_init: function() {
this._dbusImpl = Gio.DBusExportedObject.wrapJSObject(TextInTaskBarIface, this);
this._dbusImpl.export(Gio.DBus.session, '/com/michalrus/TextInTaskBar');
},
setText: function(str) {
text.text = str;
}
});
Now, after issuing:
% dbus-send --dest=com.michalrus.TextInTaskBar /com/michalrus/TextInTaskBar \
com.michalrus.TextInTaskBar.setText string:"123"
… nothing happens.

Answer 1

Final, working version of a gnome-shell extension D-Bus server:
const St = imports.gi.St;
const Gio = imports.gi.Gio;
const Lang = imports.lang;
const Main = imports.ui.main;
let text = null;
let textDBusService = null;
function init() {
text = new St.Label({ text: "0:0", style_class: 'panel-text' });
textDBusService = new TextInTaskBar();
}
function enable() {
Main.panel._rightBox.insert_child_at_index(text, 0);
}
function disable() {
Main.panel._rightBox.remove_child(text);
}
const TextInTaskBarIface = '<node> \
<interface name="com.michalrus.TextInTaskBar"> \
<method name="setText"> \
<arg type="s" direction="in" /> \
</method> \
</interface> \
</node>';
const TextInTaskBar = new Lang.Class({
Name: 'TextInTaskBar',
_init: function() {
text.text = "abc";
this._dbusImpl = Gio.DBusExportedObject.wrapJSObject(TextInTaskBarIface, this);
this._dbusImpl.export(Gio.DBus.session, '/com/michalrus/TextInTaskBar');
},
setText: function(str) {
text.text = str;
}
});
Call with:
$ gdbus call --session --dest org.gnome.Shell --object-path /com/michalrus/TextInTaskBar --method com.michalrus.TextInTaskBar.setText 'some text'