Qt: huge scrollable sub-menu loses items

Question

Updated to add:

I have fixed this, after a fashion. First, I tried calling MySubmenu -> clear() and rebuilding the sub-menu whenever the parent menu was clicked. Surprisingly, this didn't work. So I brought in the big guns: delete MySubmenu followed by MySubmenu = new QMenu (MyMainWindow) and rebuilding the sub-menu. It works now, without much noticeable delay. So I'm happy, I suppose.

Original question:

I have a sub-menu with about 1000 items in it (it's a list of C functions in a debugger). By default, Qt displays the sub-menu in columns, but this sub-menu is too big to fit on the screen, and I have no way to access the items that don't fit.

So I made the sub-menu scrollable, using a style sheet:

MySubmenu -> setStyleSheet ("* { menu-scrollable: 1 }") ;

It looks like this:

Note the scroll buttons at the top and bottom. But now if I select an item (PopRecordLength in this example), then the next time I open the sub-menu, all items above PD_DecryptCommand have disappeared:

The scroll button at the top has disappeared (the little line you can see is an underscore from what used to be the previous item.) And if I scroll down to the bottom, there is a large empty space. The total size of the sub-menu hasn't changed, but the items above PD_DecryptCommand have disappeared off the top, and I can't access them with mouse or keyboard.

However...I have just discovered, in the process of preparing this post, that if I click on this large empty space, the sub-menu disappears, but the next time I open it, it has been restored to its original state. So there is a work-around. But it's not very friendly.

Is this a bug in Qt? Or am I not setting the style sheet correctly?

Answer 1

Probably, since you have so many items that the menu takes the whole screen height, when you select an item its height increases a bit and the scroll button on top gets out of view.

I would try to connect the triggered signal of the menu with the update slot in order to get the menu repainted every time an action has been triggered

connect(MySubmenu , SIGNAL(triggered(QAction*), MySubmenu , SLOT(update()));

You could also try changing the max-height of your menu (max-height stylesheet property).