> Am 16.03.2016 um 11:51 schrieb Nuno Santos <nunosan...@imaginando.pt>: > > Hi, > > My application is targeted to run as a software plugin inside another third > party application. When a instance of my plugin is instanciated I check if > qApp exists. If so, I will use that pointer, otherwise I will reuse the > pointer. I also increment a counter to know how many instances of my > plugin are active. When the plugin is deleted I check the counter. If it gets > to zero I will delete qApp.
I don't think you're supposed to delete qApp (btw which is just a convenience macro for QCoreApplication::instance, since Qt 5.x I think). The way to end a Qt application is to tell it to QCoreApplication::exit which will then leave the (existing) Qt event loop with the given return code. GUI applications usually QGuiApplicatiob::quitOnLastWindowClosed. Once the Qt event queue is left Qt does all cleanup (or doesn't: there's quite a bit of discussions every then and when about memory leaks when Qt apps quit: but since they quit anyway those "global left-overs" are considered "to be dealt with by the OS - there are arguments for and against this practise...). In any case, you shouldn't interfere with the Qt cleanup. Specifically the global Qt app instance "belongs to Qt". Why do you query the state of qApp anyway? Do you have multiple instances of your Qt plugin (in a possibly non-Qt host application) and want to prevent the launch of the Qt event queue multiple times? Oh, and somewhat related: just make double-sure on OS X that your Qt plugin - specifically all GUI and paint operations - happen in the /main/ thread of the host application (if that's possible at all, i.e. you control/own the host app, too). It won't work otherwise (unless you hack your own Cocoa event queue for the host application, and even then you're in a mine field whenever calling other Cocoa APIs... just google for "Qt event queue thread OS X" or the like...) Cheers, Oliver
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