I suspect it's a bug, haven't turned up any earlier reports. I will add it to the tracker if someone more experiecend confirms it.
Take TestSphere. Have it extend SimpleHeadlessApp rather than SimpleGame.
java.lang.IllegalStateException: Mouse must be created before you can read events
at com.jme.input.lwjgl.LWJGLMouseInput.update(Unknown Source)
at com.jme.input.InputSystem.update(Unknown Source)
at com.jme.app.BaseHeadlessApp.start(Unknown Source)
this is on the most recent cvs as of the time of this writing.
Well, that could be considered a bug, but it depends on how you want to use a headless application, I think.
When you do
MouseInput.setProvider( InputSystem.INPUT_SYSTEM_AWT );
KeyInput.setProvider( InputSystem.INPUT_SYSTEM_AWT );
before start() it works...
So maybe the 'bug' is that there are no dummy key and mouse input classes and they are thus not used by SimpleHeadlessApp?
Ah, I see. That works. I just found out that running SimpleGame headless can be a bad idea - it takes over the CPU. A fixed rate game will be the way to go.
Yeah, Simple*** anything is only there to make your life easy when putting together demos or quickly prototyping an idea.