Open the Qt Quick Controls 1 Gallery example, click on the "Attach" button. Notice that the menu with "Image" and "Document" opens. Click somewhere else in the application. Notice that the menu closes (as expected). Click on some other button in the application. Notice that the clicked button doesn't react, but the "Attach" menu is opened again. The last two steps can be repeated over and over.

The same thing happens with the "history" dropdown in the webengine nanobrowser example. I guess that is a Controls 1 Button + Menu?