Function clip_quad 

pub fn clip_quad(
    min: Vec2,
    size: UVec2,
    clip: Option<Rect>,
) -> Option<ClippedQuad>

Clamp a layer’s composite quad (min, size — the capture rect) to its quad clip. None clip = the full quad; an empty or degenerate intersection returns None (draw nothing). UVs shift proportionally on clamped sides only, so the visible part of the capture stays put on screen.