Focus inheritance?

Suppose I have a bunch of controls of various types, some focusable and some not, all adjacent (no gaps). Underneath them all is an invisible button (which is obviously focusable).

If I move the mouse from a button onto an adjacent non-focusable thing (like an image or label) will the button underneath get the focus? Or will nothing?

I’m seeing inconsistent behaviour. Sometimes it works and sometimes it doesn’t (as tested by putting a different image for texturefocus on the underlying button). Also, if the thing moved into is a disabled button, it never seems to pass focus to the underlying button. Should it?