Inconcistent popup behavior between QMenuBar and QComboBox with Xinerama

When Xinerama is enabled, the popup behavior between QMenuBar and QComboBox is inconsistent.

For the QMenuBar, a menu item's popup menu will appear on the primary screen even if most of the menu item is on the secondary screen. For QComboBox, the popup view will appear on whichever screen contains most of the combobox.

Since both popup menus and the popup view are windows of Qt::Popup type, it seems reasonable that they behave in the same way in this context.