Unreal Engine 4.26, Windows 10, Visual Studio 2019

I would like to use FMenuBarBuilder inside my application, and tried using UNativeWidgetHost to use the menu as a component of UMG. It was not so difficult to use FMenuBarBuilder through UNativeWidgetHost. The problem is that the menu is not rendered correctly.

Whenever the mouse cursor is moved to submenu, the owner’s hovered status seems to be removed. For example, when the mouse cursor is on “MenuB_1”, the background of “MenuB” should be kept orange, and the font color of “TestMenu” should be white. Both should be kept as the hovered status.

And when I click “MenuB”, the submenu disappears and appears, while it should not be disappeared.

The editor’s menu is of course rendered correctly, so it might not be a bug, but the side effect of using UNativeWidgetHost.

I found that the status of the owner of the submenu is decided by SMenuEntryBlock::ShouldSubMenuAppearHovered of SMenuEntryBlock.cpp and the status of

!OwnerMultiBoxWidget.Pin()->IsHovered()

is inversed whenever using FMenuBarBuilder through UNativeWidgetHost. So maybe OwnerMultiBoxWidget is not set correctly when using FMenuBarBuilder inside UNativeWidgetHost. If I remove "!" and modified the function to

bool SMenuEntryBlock::ShouldSubMenuAppearHovered() const
{
	// The sub-menu entry should appear hovered if the sub-menu is open.  Except in the case that the user is actually interacting with this menu.  
	// In that case we need to show what the user is selecting
	return MenuAnchor.IsValid() && MenuAnchor.Pin()->IsOpen() && OwnerMultiBoxWidget.Pin()->IsHovered();
}

Then the menu is rendered correctly. (The problem of disappearance of the submenu by clicking the owner still remains.)

I've upload whole the project code to GitHub. https://github.com/HSeo/SimpleMenuBarBuilder

Any comment would be very welcome. Thank you.