Feeds the surface's own position so travel can elongate it. Pass both the page-space
and viewport-space coordinates: travel is the smaller of the two motions per axis, so
a scroll — which moves an element in exactly one of those spaces — never reads as travel.
Feeds the surface's own position so travel can elongate it. Pass both the page-space and viewport-space coordinates: travel is the smaller of the two motions per axis, so a scroll — which moves an element in exactly one of those spaces — never reads as travel.