Qt service with gui

JonB

@franco-amato
Cannot imagine what your use case is. But a Windows Service cannot normally have a UI. Rather than my guessing whether any of them work, you might Google for windows service with ui and have a look through the various questions/answers. I am not sure any of them will work, at least nowadays.

artwaw

@franco-amato Usually design goes like this:
you have one process running as a service, with privileges. The other one is with GUI and what not, doing actual work.
While I am not sure how one can prevent gui process from being closed, the work of a service in this case would be to monitor/being notified about the closure and if that's the case, respawn the gui and possibly notify some API that the incident happened.

JonB

@artwaw said in Qt service with gui:

respawn the gui

I think that will be "tricky" from a service. For example, it doesn't have access to the desktop and it doesn't run as the desktop/logged on user.

franco.amato

@JonB T Don't you think that I already performed a google search before posting here?

JonB

@franco-amato
Not particularly, no. A lot of posters here don't, in fact probably most. And if they do they usually say so and what they came across. You asked if it is possible to show a GUI from a Windows service, and I suggested it is not, so far as I know.

artwaw

@JonB said in Qt service with gui:

it doesn't have access to the desktop and it doesn't run as the desktop/logged on user.

Yeah BUT :) I assumed gui runs as an identifiable process, at least that's what I think OP implied here. You can monitor that from the service, right?

The usual convenience (i.e. antivirus brought up previously) is that monitored gui runs for every user. And having a process running with privileges in the background I suppose you are able to discern which of your monitored processes runs under which user.

To be honest I don't think it is a nice way of implementing any solution but that's the only way that comes to mind right now.

JonB

@artwaw
You can "monitor" a process from a service, but I don't see how that relates to what the OP is wanting.

The example for anti-virus just seems to be: the non-UI part of the AV runs as a service (with privileges), the user chooses to fire up a user-process UI which happens to communicate with it. The UI process is fully user-level, nothing special about it, so far as I know. I don't think that is what the OP is asking for. But we shall see.

artwaw

@JonB That's essentially what I wanted to say about the design, yes. And that would be my advice on how to implement functionality - using two processes: a monitor and a user-space gui. Unless Windows allows service to span a privileged process that a user can't interfere with but that's not a knowledge I possess.

franco.amato

@JonB no is not what I asked. You should re read my first post.

SGaist

Hi,

One possible cheat is that you use a QProcess to start a new instance of your application if somebody stops it.
From a design point of view, you can forbid your user to close the application by handling the close event yourself. A starting point might be the QSystemTrayIcon example.
Note that this does not protect your application from getting killed but you can still handle the usual interruption signals.
The system service + client application combo is still worth exploring as you can have the service providing the core functionality and the application being merely a front-end.

JonB

@franco-amato said in Qt service with gui:

You should re read my first post.

I have read it many times, thanks. Best of luck showing a UI from a Windows service.

franco.amato

@JonB said in Qt service with gui:

@franco-amato said in Qt service with gui:

You should re read my first post.

I have read it many times, thanks. Best of luck showing a UI from a Windows service.

If you had read it you would have seen that I stated the following: "I know that a Windows service usually doesn't have a GUI and I'm not sure it can have one". What I asked is whether the path of service is the right path or if there are other solutions to achieve my need

JonB

@franco-amato said in Qt service with gui:

If you had read it

Thanks again. It's always nice to try to help people, just what we like to hear.

I read your post carefully, as I said. All I ever answered was that I think you will find it difficult to run a UI from a service. You asked if that was the "right path", I suggested it is not. Sorry if you didn't want to hear that. Why don't you leave me out now, thanks.

franco.amato

@SGaist Can you help with a small example regarding this "One possible cheat is that you use a QProcess to start a new instance of your application if somebody stops it." ?

SGaist

// rest of the code
int result = app.exec();
QProcess::startDetached("your_application");
return result;

franco.amato

@SGaist said in Qt service with gui:

// rest of the code
int result = app.exec();
QProcess::startDetached("your_application");
return result;

It worked but now I am not able to stop it anymore :)) and I am the admin

SGaist

You will have to implement some checks to determine who stopped the application.

Note that you also need to implement graceful shutdown for when you stop/restart your machine.

franco.amato

@SGaist said in Qt service with gui:

You will have to implement some checks to determine who stopped the application.

Note that you also need to implement graceful shutdown for when you stop/restart your machine.

It's not clear what you mean with graceful shutdown. Can you give an example please?

SGaist

Simply when you want to shutdown or reboot the machine for example when applying security fixes, kernel update, system updates, etc.

Sikander Rafiq

@franco.amato Will you be able to make QT service with GUI or launch QT app with GUI from Qt service?