Transient parent for QtWidgets popup menus

[Elvis Angelaccio]

Hi all,
as you may know in Wayland popup menus are wrongly positioned if they don't 
have
a transient parent set on their window.

For QtWidget applications the fix itself is rather easy (at least in the 
simplest case):

   someMenu->createWinId();  // someMenu is a QMenu
   
someMenu->windowHandle()->setTransientParent(someWidget->nativeParentWidget()->windowHandle());


But I see a number of problems:

1. Popup menus are literally everywhere in QtWidgets applications, so we 
need to apply the fix in a lot of places.
2. Popup menus are often hidden, so we may easily forget to fix some of 
them.
3. We don't control 3d-party Qt apps, so we can't fix them if they are 
broken.
4. The fix involves createWindId() which is marked as "internal", it feels 
wrong to use it everywhere imho.

Shouldn't we fix this issue in upstream QMenu instead?

Basically if we have existing code that does:

   menu = new QMenu(someParent);

then the QMenu constructor could do:

   createWinId();
   
windowHandle()->setTransientParent(parent()->nativeParentWidget()->windowHandle());

Does it makes sense? Would it work?
If it does, we would fix most of the existing popup menus for free...

Cheers,
Elvis