I get a graphical glitch with the top toolbar in a QMainWidow when going fullscreen with macOS. The issue appears when using QVTKWidget in the central widget.

Minimal program that reproduces the issue:

Qt Code: 
  1. #include <QApplication>
  2. #include <QMainWindow>
  3. #include <QWidget>
  4. #include <QToolBar>
  5. #include <QVTKWidget.h>
  6.  
  7. int main(int argc, char *argv[])
  8. {
  9.   QApplication app(argc, argv);
  10.  
  11.   QMainWindow * window = new QMainWindow();
  12.   QVTKWidget * widget = new QVTKWidget(window);
  13.   window->setCentralWidget(widget);
  14.   QToolBar * toolBar = new QToolBar(window);
  15.   window->addToolBar(Qt::TopToolBarArea, toolBar);
  16.  
  17.   window->show();
  18.   return app.exec();
  19. }
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Screen Shot 2017-07-31 at 20.49.45.jpg

If QWidget is used instead of a QVTKWidget the glitch does not occur:

Qt Code: 
  1. #include <QApplication>
  2. #include <QMainWindow>
  3. #include <QWidget>
  4. #include <QToolBar>
  5. #include <QVTKWidget.h>
  6.  
  7. int main(int argc, char *argv[])
  8. {
  9.   QApplication app(argc, argv);
  10.  
  11.   QMainWindow * window = new QMainWindow();
  12.   QWidget * widget = new QWidget(window);
  13.   window->setCentralWidget(widget);
  14.   QToolBar * toolBar = new QToolBar(window);
  15.   window->addToolBar(Qt::TopToolBarArea, toolBar);
  16.  
  17.   window->show();
  18.   return app.exec();
  19. }
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Screen Shot 2017-07-31 at 20.50.38.jpg

macOS Sierra, Qt 5.9.1, VTK 8.0.0 (I also observed this behavior with previous versions of VTK).