KTailctl can be started multiple times in Flatpak

[Justinzobel]

I can open multiple instances of the application.

Not sure if it is Flatpak specific but a quick check to see if the app is already open would be nice to add.

[f-koehler]

I thought that it behaves like that already (last time I checked on KDE Plasma with the flatpak version). But definitely can be started multiple times on other desktops...

Need to figure out a solution to this. Other KDE apps (e.g. kasts) can only be started once even if installed as a flatpak. One solution would be using QSharedMemory but that would probably required additional flatpak permssions (such as --device=shm). I will have to investigate how other apps achieve this without this shared memory hack.

[Justinzobel]

I've asked the Kasts dev if they can pop in and provide any insight.

[code8buster]

At the end of main.cpp of the KDE plasma-welcome application, there is a snippet that makes the welcome center single-instance. Perhaps a similar technique can be used to register ktailctl with kdbus
https://github.com/KDE/plasma-welcome/blob/master/src/main.cpp#L115

    // Make it single-instance so it raises e.g. when middle-clicking on taskmanager
    // or accidentally launching it while it's already open
    KDBusService service(KDBusService::Unique);
    QObject::connect(&service, &KDBusService::activateRequested, &engine, [&engine](const QStringList & /*arguments*/, const QString & /*workingDirectory*/) {
        const auto rootObjects = engine.rootObjects();
        for (auto obj : rootObjects) {
            auto view = qobject_cast<QQuickWindow *>(obj);
            if (view) {
                KWindowSystem::updateStartupId(view);
                KWindowSystem::activateWindow(view);
                return;
            }
        }
    });

[f-koehler]

@code8buster, thank you for the hint. That could be a potential solution! (Even though not all KDE Apps seem to do it that way). I will test it out, looks like the behavior we want.

[f-koehler]

Maybe not fully fixed yet:

          This seems to have worked for not starting multiple instances, but in testing the master branch I've noticed that it doesn't open the window when KTail is in-tray or even simply minimized.

Originally posted by @code8buster in #331 (comment)