I did as you've said but it didn't work I don't know why.
I can add vertical separators in the tool bar but not horizontal ones in the menu.
here is what I did in the function that creates he menus :


Qt Code: 
  1. void MainWindow::createMenus()
  2. {
  3.     fileMenu = menuBar()->addMenu(tr("&File"));
  4.     fileMenu->addAction(newAct);
  5.     fileMenu->addAction(openAct);
  6.     fileMenu->addAction(saveAct);
  7.     fileMenu->addAction(saveAsAct);
  8.     fileMenu->addAction(solveAct);
  9.     fileMenu->addSeparator();
  10.     fileMenu->addAction(quitAct);
  11.  
  12.     editMenu = menuBar()->addMenu(tr("&Edit"));
  13.     editMenu->addAction(undoAct);
  14.     editMenu->addAction(redoAct);
  15.     editMenu->addSeparator();
  16.     editMenu->addAction(cutAct);
  17.     editMenu->addAction(copyAct);
  18.     editMenu->addAction(pasteAct);
  19.     editMenu->addSeparator();
  20.     editMenu->addAction(selectAllAct);
  21.  
  22.     menuBar()->addSeparator();
  23.  
  24.     viewMenu = menuBar()->addMenu(tr("&View"));
  25.     viewMenu->addAction(displayEditorAct);
  26.     viewMenu->addAction(displayResultAct);
  27.  
  28.     helpMenu = menuBar()->addMenu(tr("&Help"));
  29.  
  30. }
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thanks in advance for your help.