Function centered_rect 

pub fn centered_rect(screen: Rect, width: u16, height: u16) -> Rect

Compute a width×height Rect centered within screen.

width/height are clamped down to screen’s own dimensions if larger, so the result never extends past screen’s edges – a modal, dialog, or tooltip box built from this is always fully on-screen, even on a terminal too small to fit the box’s requested size. Pure layout math: no drawing, no Terminal. Pairs with panel/modal in retroglyph-widgets (the draw module) for a centered, bordered box.