Must construct QApplication before QPaintDevice

[sekatsim]

Ahh, yes, sorry. I did a file search for any occurrence of "static", nothing turned up.

Was it a poor choice to declare my other classes within MainWindowImpl.h? I've noticed that if I remove all of the other classes, I can execute, but I suppose that could mean many things.

[jacek]

Was it a poor choice to declare my other classes within MainWindowImpl.h?

No, it shouldn't be a problem.

I've noticed that if I remove all of the other classes, I can execute, but I suppose that could mean many things.

This means that the problem is in one of those removed classes. Do you use threads?

[sekatsim]

I've got two versions of the project now. I got stuck on this QApplication problem, so I backed it up and went back to an earlier version, from before I rearranged the functions. I've added threading to that one, as per my other post. But no. No threading in this version.

I've removed those classes one by one, in a few different orders, to figure out what might be causing the problem. But it doesnt really seem to be resolved until I remove all of them. Most of those classes do make adjustments to QWidgets.. i.e. setting and restoring slider values, etc, but I see no reason why those classes would be run before main.

Is there any way I can prohibit all "QApplication" type activities until the window has been drawn? I could try making a unique .h file for main.cpp, that only has the MainWindowImpl class.. but I fear it may screw me up down the road.

[jpn]

Is it all in a single project or do you have app + lib? If so, make sure both are compiled in same mode, release vs. debug.

[jacek]

Is it all in a single project or do you have app + lib? If so, make sure both are compiled in same mode, release vs. debug.

Good point. Other possibility is that the application is compiled in debug mode and linked with the release version of Qt.

[sekatsim]

It's all in one project, and unless I've been specifically trying to solve a problem, I've been compiling in release mode. I think I found the problem, but I'm not quite sure why it was the problem:

I moved many of my functions outside of the mainwindowimpl class, but when they were done functioning, I wanted them to call refreshDisplay within mainwindowimpl to update all of my sliders/buttons etc. So I had

MainWindowImpl mainwin;
mainwin.refreshDisplay();

As far as I can tell, this is whats causing the problem. Is there anyway I can get around this?

[jacek]

MainWindowImpl mainwin;
mainwin.refreshDisplay();

As far as I can tell, this is whats causing the problem. Is there anyway I can get around this?

Do I understand correctly that you invoke refreshDisplay() before QApplication::exec()?

Maybe the error message is a bit misleading and you should try:

MainWindowImpl mainwin;
QTimer::singleShot( 0, & mainwin, "refreshDisplay" );

MainWindowImpl mainwin;
QTimer::singleShot( 0, & mainwin, "refreshDisplay" );

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(provided that refreshDisplay() is a slot)?

[sekatsim]

No, thats the thing, I dont *execute it*, persay, before QApplication::exec(), but it occurs in classes that are defined before QApplication::exec(). It seems like just having an instance of that class causes it to evaluate it and return an error.

So I guess I would suggest to anyone else having this problem to remove any instance of MainWindowImpl (or whatever your main QWidget drawing class is) that occurs outside of itself.

[jacek]

No, thats the thing, I dont *execute it*, persay, before QApplication::exec(), but it occurs in classes that are defined before QApplication::exec(). It seems like just having an instance of that class causes it to evaluate it and return an error.

So if you put "MainWindowImpl mainwin;" in your main(), you get the error and if you comment it out the error disappears?

[sekatsim]

Exactly. I dont understand why. But at least I know to avoid it now

[jacek]

Exactly. I dont understand why. But at least I know to avoid it now

It shouldn't behave this way. Does the error appear when you comment out all of the code in MainWindowImpl constructor?