A dialog is also a widget Ok, does it have keyboard focus?

Furthermore your code is incorrect:
Qt Code: 
  1. if (event->key() == Qt::Key_Control && Qt::Key_Alt && Qt::Key_V)
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this can be translated to:
Qt Code: 
  1. if(event->key() == Qt::Key_Control && 0x01000023 && 0x56)
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which again translates to:
Qt Code: 
  1. if(event->key() == Qt::Key_Control && true && true)
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and then to:
Qt Code: 
  1. if(event->key() == Qt::Key_Control)
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which as you probably guess is not what you want. Read what QKeyEvent::key() is and use it with conjunction with QKeyEvent::modifiers(). Or just use QShortcut.

Learning a bit more C++ wouldn't hurt either.