FixedAspect

A rectangle whose width over height always equals ratio.

ratio is a fraction of the frame on both axes, not of the frame's own aspect. Build one from a picture ratio with lockedTo, which is where that conversion lives.

A corner drag sets the rectangle's size from its horizontal movement alone, anchored at the opposite corner, so vertical movement on a corner does nothing. An edge drag holds the opposite edge on that same axis fixed and grows the other axis symmetrically around its own centre.