Clearing a QMenu while open toggles visibility

pino

I found a weird behavior with context menus. When I clear it, it toggles visibility.

Create a Qt desktop app and a window with a tree view. Insert the following:

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->treeView->setContextMenuPolicy(Qt::CustomContextMenu);
}

void MainWindow::on_treeView_customContextMenuRequested(const QPoint &pos)
{
    QMenu *m = new QMenu();
    m->addAction("foo");
    QTimer t;
    connect(&t, &QTimer::timeout, this, [=](){
        m->clear();
        m->addAction("bar");
    });
    t.start(2000);
    m->exec();
}

When I now right-click into the tree view, my context menu opens (top, left!), and with each execution of the timer, the context menu gets invisible, and visible again, and so on.

Note: Although it effectively triggers visibility, it doesn't in the data structures. In my real program, I can trigger the actions by clicking on the area nevertheless.

I'm not sure if I should report it too fast. I suspect it might depend on some part of my environment (Qt version, KDE, Ubuntu, GPU, whatever, ...). It looks so low-level... Can you reproduce it? Or, is it okay to report it directly without further checks (sorry for my stupid question ;) )?

SGaist

Hi and welcome to devnet,

Can you give more details about your environment ?

mrjj

Hi
Note:
It was easy to test so i did it on win 10/Qt.57 vs 2015
I did see some strange flashing so i tried the following

....
connect(&t, &QTimer::timeout, this, = {
m->setUpdatesEnabled(false) ;
m->clear();
m->addAction("bar");
m->setUpdatesEnabled(true) ;
});
....
Which seems to reduce it a lot.

pino

@SGaist Hi, thank you! It's a kubuntu 17.04 (with its Qt 5.7.1), amdgpu gpu driver.

pino

@mrjj Okay, then it's more specific. The setUpdatesEnabled calls haven't changed the behavior here.