Align objects along an `absolute` (vertical or horizontal) line `l`.
At `p0`: (1) The line `l` starts. (2) An angle has its arrowhead here. Line and angle define direction and target position. (3) A selector rectangle defines the set of objects to align.
At `p1`, where `l` ends: (4) A filled rectangle indicates the align to be `absolute`.
Align a set of objects with their right edges along an given `absolute` line `l`.
==> :
Align a set of objects with their left edges along an given `absolute` line `l`.
==> :
Align a set of objects with their bottom edges along an given `absolute` line `l`.
==> :
Align a set of objects with their top edges along an given `absolute` line `l`.
==> :