What happened to QtSingleApplication?

Crag_Hack

I'd like to know how to pass command line arguments to an already open program. So the user runs "backup.exe -job awef" and backup.exe recognizes there is an already open process and passes the argument to the already open process so users can command the program to do what they wish from the command line or a shortcut in windows.

I did a lot of research and found QtSingleApplication is deprecated...
Anybody know anything about the alternatives below? Are they reliable? Any other information to know?

https://github.com/itay-grudev/SingleApplication
https://github.com/qtproject/qt-solutions/tree/master/qtsingleapplication

VRonin

You can do it using QLocalSocket and QLocalServer. when you start the application use a QLocalSocket and try to connect to an existing server if returns an error of type QLocalSocket::ServerNotFoundError then start the server.
If another instance of application will start it will try and succeed in the connection, you can then use the socket to transmit data between the two applications and, once done, make the second application quit

SGaist

Hi,

It's available here and has been updated to work with Qt 5.

Crag_Hack

Thanks for the help guys. @SGaist where can I find the header file for the class? Is there any documentation? Also just curious is qt-solutions officially part of The QT Company?

SGaist

Just clone the QtSolutions repository, you have everything there. The documentation will be same as the one you can find online but you can also build it when you build the module.

It's a module provided by The Qt Company.

ssokolow

@VRonin Not an ideal solution since it's on you to reinvent appropriate scoping.

For example, for a desktop Linux/BSD application, the proper solution would be to claim a static name on the session bus via QtDBus (Something like com.you.YourApplication), which has the added benefit of giving you a ready-made place to offer automation RPC to the rest of the desktop, such as raise(). (Not to mention the pre-defined namespaces, like MPRIS.)

At the very least, I'd incorporate the username or user ID into the server name when using QLocalSocket and QLocalServer.

kshegunov

@ssokolow said in What happened to QtSingleApplication?:

@VRonin Not an ideal solution since it's on you to reinvent appropriate scoping.

Perhaps, but rather simple and I'm pretty sure QtSingleApplication does it this way, too.

ssokolow

@kshegunov

Actually, I took at quick look at the source code and it looked like it was using a lockfile in the user profile, which means that it would be user-scoped rather than session-scoped.

(ie. Two separate sessions under the same account would interfere with each other.)

kshegunov

@ssokolow said in What happened to QtSingleApplication?:

Actually, I took at quick look at the source code and it looked like it was using a lockfile in the user profile, which means that it would be user-scoped rather than session-scoped.

I believe this is correct, yes.

Crag_Hack

A quick follow up question that's been nagging me... what's the reason for the Qt Company providing a separate QT Solutions module that's not part of the main api?

SGaist

Quote from the old days:
Trolltech provides platform- and industry-specific components and tools, as well as cutting-edge components too new to include directly in Qt.

That's what the Qt Solutions were originally.