LangBarButton::InitMenu() function is not called

[lihz]

I am developing an IME with LibIME2.
I'm reporting one symptom that I don't understand.

The LangBarButton::InitMenu() function is not called at all, which prevents me from creating a popup menu when right-clicking on the IME's MODE icon.

I have no idea if this is a bug, intended behavior, or if I'm using LibIME2 incorrectly.

PS:
I don't know if it has anything to do with this symptom, but MS's documentation changed the guid used for LangBarButton to use only GUID_LBI_INPUTMODE. The documentation states that other GUIDs are ignored internally. In practice, if you use a different GUID, it will not be visible on the screen.