Is it even possible?
Also how to get mouse dx dy after you do that?

I'm curious about this too

same here

Version 0.1.0f added mouselock(do_lock, event_sensitivity, move_sensitivity). The first argument is a boolean flag to lock or unlock the cursor; the second and third are sensitivity for the events you receive, and for cursor movement. If you want to hide the cursor, you can use window { cursor = 0 }, or for a UI widget self.cursor = 0.

Note that in 0.1.0f mouse-locking didn't work in the BBS. I'm not sure if that was fixed in 0.1.0g, since my carts refuse to run in the BBS with this version...