Requires 2 right clicks to switch context menus among items? - c++

Question

Code below
#include <QtWidgets>
#include <QGLWidget>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QMainWindow w;
w.setCentralWidget(new QGLWidget(&w)); // w.setCentralWidget(new QWidget(&w));
QTreeWidget* tree = new QTreeWidget(&w);
QTreeWidgetItem* item0 = new QTreeWidgetItem(tree, QStringList("a"));
QTreeWidgetItem* item1 = new QTreeWidgetItem(tree, QStringList("b"));
tree->setContextMenuPolicy(Qt::CustomContextMenu);
QObject::connect(tree, &QTreeView::customContextMenuRequested, [](){
QMenu menu;
menu.addAction("a");
menu.exec(QCursor::pos());
});
QDockWidget* dock = new QDockWidget("Tree", &w);
dock->setWidget(tree);
w.addDockWidget(Qt::LeftDockWidgetArea, dock);
w.show();
return a.exec();
}
Compile and run it. It requires 2 right clicks to switch context menus among items. However, if I change QGLWidget to QWidget. It is fine. 1 right click can switch context menus among items. Any bugs??? Thanks a lot.
Some observations:
Switch the positions of the tree and the GL widget is ok, i.e. set the tree as the central widget and GL Widget as the one in the dock.
It seems the right click event goes to the central widget and then is blocked by the GL widget.