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I'm having a trouble with the QwtPolar library.

I'm using Qt 5.3 and I have Qwt 6.1 working properly.

I build the QwtPolar using:

qmake 
make
make install

When I try to run the QwtPolar examples, I get the following error:

QWidget: Must construct a QApplication before a QPaintDevice

I already read a lot of posts in the Qt Forum and stackoverflow, but I can't figure out what is happening and how to solve it.

Note: I read some things about mixing the debug and release mode, but I don't know what mode was used to build the Qwt and how to change it.

I will appreciate if someone can help me.

I'm using Windows 8.1.

Sorry for my english.

Thanks.

KelvinS
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2 Answers2

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I've met the same error long ago. I'll try to repeat your problem on my machine, and in the meantime try this (one of these should help):

  • Switch from Debug mode to Release mode (or vice-versa) and build;
  • Disable "Shadow build" in the Project config tab and build;
  • Rebuild the project.
viddik13
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  • Thanks for the answer. - In release mode I get the following error: `QWidget: Must construct a QApplication before a QPaintDevice` And in debug mode I get this: `error: cannot find -lqwtpolard` - I tried to disable "Shadow build", but I'm still getting the error. - I tried "clean all" and rebuild the project, but nothing changed. – KelvinS Mar 04 '16 at 18:15
  • viddik13 I solved the problem by recompiling the qwtpolar. I don't know what happened before, I think I did something wrong on the compilation step. Anyway, thanks for the help. – KelvinS Mar 18 '16 at 00:47
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The problem was solved by recompiling the qwtpolar library.

KelvinS
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