Here is more info:
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dock->setVisible( false );
dock->setFloating( mCurrentDockWidget->isFloating() );
dock->resize( mCurrentDockWidget->size() );
dock->move( mCurrentDockWidget->pos() );
mCurrentMainWindow->removeDockWidget( mCurrentDockWidget );
mCurrentDockWidget = dock;
mCurrentMainWindow = win;
dock->setVisible( true );
QMouseEvent *event = new QMouseEvent( QEvent::MouseButtonPress, locPos, globPos, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier );
QCoreApplication::postEvent ( dock->titleBarWidget(), event ); //IS NOT WORKING
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I use special title bar for docks, so dock->titleBarWidget() doesn't return NULL.
Posting mouse down event to the title bar doesn't get me in the dragging mode again.