I don’t know what the problem is so it’s tough to say… but that would disable the default behavior, yes.
Edit: your link says “Lemur provides two-way navigation” but that’s not the whole story, by the way. You can control the navigation and will get left/right/up/down, etc… it just (by default) treats left/up and down/right the same. See DefaultFocusTraversalControl.
…if you provide your own then you can do whatever you want for up/down/left/right/whatever.
* START OF DIFF FROM FocusNavigationState
* If we are inside a Container, ignore the focus change
if (container instanceof Container)
next = null;
//END OF DIFF
Maybe not the best approach, but it works.
That was the reason for which I have a forked version of Lemur: it’s not possible to plug in an alternate version InputManager (under your suggestion btw). But that’s just half of the problem.
After a quick inspection InputManager looks like it’s built around LWJGL2 and then shoehorned into LWJGL3. If I want to add a GLFW version of it then I need to change JME interfaces and therefore a lot of stuff which is unlikely to be PR back into JME master.
Hence my suggestion to remove/deprecate LWJGL2.