Duplicate repeats the last duplicate's offset, but of the ways to move the copy
before the second Cmd+D only `node.set` and Alt-drag were covered. Dragging it
with the mouse is how almost everyone does it, and is what #567 describes; an
arrow-key nudge is how a small offset is usually made exact. Both work, because
the step is measured from where the copy ended up rather than recorded from the
gesture, but nothing held them there.
The drag test also asserts the drag moved the copy rather than making another
one, left it selected, and left the original in place: the ways the feature
could break without the step arithmetic breaking.
Both fail if the step lookup in `edit.duplicate` is stubbed out.
- A copy Alt-dragged off a layer snaps to that layer too: its edges,
centres and equal spacing (Targets::add_box with the originals' box).
Before, the originals were left out of the snap targets, so a copy
couldn't line up with or space evenly from the layer it came from.
- Duplicate (Cmd+D) repeats the last duplicate's page offset while its
copies are what it duplicates: Alt-drag a copy, or Duplicate and move
the copy, then each Cmd+D steps out the next one as far again. The
step is measured when Duplicate runs. It lasts as long as the
selection (undo reuses ids), copies placed by an auto layout set no
step, and explicit dx/dy win.
- measure_tests: an Alt-dragged copy between its original and another
layer now snaps to equal spacing (45/45 instead of 50/40).
Tests: duplicate_spacing_tests (snap to the original, equal spacing,
repeat after moving a copy and after an Alt-drag, only for the last
copies, undo then a new layer, rotated frame, auto layout).
Refs #256
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
