Question

I have a QMainWindow whose central widget has been set to a QGraphicsView viewing a black scene (for test purposes). Note that in the code below, I use my class derived from QGraphicsView, called CQtGlView, which reimplements only the resizeEvent function.

Regardless of whether I add the view directly,

CQtMainWindow::CQtMainWindow() {
  m_glView = new CQtGlView();
  setCentralWidget(m_glView);
}

or stick it in a layout with margins of 0 in a dummy widget,

CQtMainWindow::CQtMainWindow() {
  m_glView = new CQtGlView();

  QWidget* dummy = new QWidget();
  QHBoxLayout* l = new QHBoxLayout();
  l->setContentsMargins(0,0,0,0);
  l->addWidget(m_glView);
  dummy->setLayout(l);

  setCentralWidget(dummy);
}

I get an unwanted grey border around the widget.

The screenshot below illustrates the problem, visible between my scene and the windows aero border.

This would not be a problem if my application did not allow switching to full screen. The border is very obvious once the rest of the screen is black.

It’s possible this area represents the DockWidgetAreas around the outside of the central widget.

Is there anything I can do to solve this other than not use QMainWindow? (Undesirable due to my use of menuBar, tool bars, and statusBar.)

Answer 1

It turns out that QGraphicsView derives from QFrame, where I assumed it was only a QWidget.

The solution to this problem was to call setFrameStyle(QFrame::NoFrame); in the constructor of my QGraphicsView subclass. Or if it was not a subclass,

m_glView->setFrameStyle(QFrame::NoFrame);