Is it possible to get a return value from a KWin script?

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1

Is there any way to know if a KWin script executed properly? Here is a simple script to focus on the last active window of a given app:

windows = workspace.windowList();
target_name = 'emacs';
target_window = null;
for (var i = 0; i < windows.length; i++) {
  if (windows[i].resourceName == target_name
      && (target_window == null
       || windows[i].stackingOrder > target_window.stackingOrder)
      && windows[i].desktops[0] == workspace.currentDesktop) {
    target_window = windows[i];
  }
}
if (target_window != null) {
  workspace.activeWindow = target_window;
}

If the app is not found (it’s not running) I would like to start it instead. But I need that information somehow to make the decision. I guess I could print something like “NOT FOUND” and search for that string in journalctl but I wonder if there are better ways. I could also run ps aux | grep emacs but that works across desktops which is close but not quite what I want. I’m calling the script from C++ like this:

QDBusMessage response;
QDBusMessage m;
// LOAD
m = QDBusMessage::createMethodCall("org.kde.KWin",
                                   "/Scripting",
                                   "",
                                   "loadScript");
m << "main.js";
response = QDBusConnection::sessionBus().call(m);
// RUN
m = QDBusMessage::createMethodCall("org.kde.KWin",
                                   "/Scripting",
                                   "",
                                   "start");
response = QDBusConnection::sessionBus().call(m);
qDebug() << response.arguments();

but I haven’t found any way to populate response.arguments() with anything useful. Any comments would be appreciated!

I have no experience with KWin but since I can’t use wmctrl anymore (my OS just upgraded to Plasma 6) I’m trying to recreate some of the functionality with KWin scripts.

2

Yes you can use journal to catch the result, but a better alternative would be to send the result using callDBus to a service you register like this example I did in python Determine when monitor is turned on or off via python dbus - #7 by luisbocanegra

You may also find this project useful

3

Thanks, using my own dbus service seems to work. Next, how can I call the script from a shell script instead of C++? This seems to have no effect:

dbus-send --session --dest=org.kde.KWin /Scripting org.kde.kwin.Scripting.loadScript "string:main.js"
dbus-send --session --dest=org.kde.KWin /Scripting org.kde.kwin.Scripting.start

Is there any up to date KWin scripting documentation I could look at?

4

For dbus stuff I usually explore them with qdbus and sometimes I even look at the xml description files.
There’s KWin scripting tutorial | Developer but doesn’t include how to load scripts manually.

Here’s how a script can be loaded/unloaded using shell script:

SCRIPT="/home/luis/projects/plasma-panel-spacer-extended/moveTopWindow.js"
SCRIPT_NAME="moveTopWindow"
qdbus org.kde.KWin /Scripting org.kde.kwin.Scripting.unloadScript "$SCRIPT_NAME"
script_id=$(qdbus org.kde.KWin /Scripting org.kde.kwin.Scripting.loadScript "${SCRIPT}" "$SCRIPT_NAME")

# run
qdbus org.kde.KWin /Scripting/Script"$script_id" org.kde.kwin.Script.run
sleep 1
qdbus org.kde.KWin /Scripting/Script"$script_id" org.kde.kwin.Script.stop
1 Like
5

Thanks a lot! Here is my full solution. A script to focus or launch an app,

# Resource name as returned by print(windows[i].resourceName) below
APP_NAME=$1
# Path to the executable that launches the app
EXEC_PATH=$2

if [[ ! $(pgrep -f focus_or_launch_service.py) ]]; then
    python focus_or_launch_service.py &
    sleep 0.1
fi

SCRIPT='main.js'
cat > $SCRIPT <<EOF
resource_name = "${APP_NAME}";
exec_path = "${EXEC_PATH}";
windows = workspace.windowList();
target_window = null;
for (var i = 0; i < windows.length; i++) {
  // Output: journalctl -f QT_CATEGORY=js QT_CATEGORY=kwin_scripting
  // print(windows[i].resourceName);
  if (windows[i].resourceName == resource_name
      && (target_window == null
       || windows[i].stackingOrder > target_window.stackingOrder)
      && windows[i].desktops[0] == workspace.currentDesktop) {
    target_window = windows[i];
  }
}
if (target_window != null) {
  workspace.activeWindow = target_window;
} else {
  callDBus(
    'com.raul', '/com/raul/runcommand', 'com.raul', 'run_command', exec_path);
}
EOF

SCRIPT_NAME='focusOrLaunch'
qdbus org.kde.KWin /Scripting org.kde.kwin.Scripting.unloadScript "$SCRIPT_NAME"
script_id=$(qdbus org.kde.KWin /Scripting org.kde.kwin.Scripting.loadScript \
                  "${SCRIPT}" "$SCRIPT_NAME")
qdbus org.kde.KWin /Scripting/Script"$script_id" org.kde.kwin.Script.run

and the service I need for launching an app if not already running:

from gi.repository import GLib
import asyncio
import dbus
import dbus.mainloop.glib
import dbus.service


class Service(dbus.service.Object):
    def __init__(self):
        self._loop = GLib.MainLoop()

    def run(self):
        dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)
        bus_name = dbus.service.BusName("com.raul", dbus.SessionBus())
        dbus.service.Object.__init__(self, bus_name, "/com/raul/runcommand")
        self._loop.run()

    @dbus.service.method("com.raul", in_signature="s", out_signature="")
    def run_command(self, cmd):
        async def run(cmd):
            await asyncio.create_subprocess_shell(cmd)
        asyncio.run(run(cmd))

    @dbus.service.method("com.raul", in_signature="", out_signature="")
    def quit(self):
        self._loop.quit()


if __name__ == "__main__":
    Service().run()

I’m sure many things can be more elegant here but it does exactly what I need. I can bind the shell script with different arguments (e.g. focus_or_launch.sh emacs /usr/bin/emacs) to different keyboard shortcuts.

1 Like