Undo answers "take back the last thing", which is the question asked about a
mistake just noticed. It is the wrong instrument for one noticed six
adjustments later: eight presses, each changing the picture, with no way to see
how far back the mistake is without passing through it. A step is a whole
state, so arriving from six away costs what arriving from one does — which is
what makes a row worth making clickable rather than decorative.
`Edit::Discrete` had to go for the list to be worth drawing. Seventeen call
sites recorded the same anonymous step, which is fine for deciding whether two
changes are one gesture and useless for a panel: seventeen rows reading
"Discrete" is not a history. Every variant now carries enough to name itself,
and the compiler enumerated the sites that had to start saying so. A step that
moved a parameter is still named out of the descriptor, so an operation added
as a YAML declaration appears in the history correctly named with nothing
written for it (FR-DEV-3c).
Choosing a film stock was not undoable at all. The pick went straight to
`choose_film`, which nothing on the history's path ever sees. `pick_film`
records it, and is separate because the same call is also how a *restored* edit
gets its tables back — recording that would push a step for the undo the
photographer had just asked for.
The list is rebuilt off a revision rather than off every redraw. A drag ends in
a redraw per frame while folding into one step, so the unconditional version
would tear down and recreate every row sixty times a second to arrive back at
the list already on screen. The counter is process-wide: a per-instance one
starts every photograph at the same number, so a frontend holding "the revision
I last drew" would keep the previous image's steps on screen — invisible while
every image opens with one identical row, and a wrong-photograph bug the moment
persisted history means it does not.
The step names that no descriptor can supply are constants with a roll, and a
test walks the roll rather than a second copy of it. `resolve` splits so that
"is this catalogued?" can be asked: `derive` turns `history.mask_toggled` into
"Mask Toggled", which names a field rather than an act and, being perfectly
readable, is a mistake nobody would look at twice.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The undo stack snapshotted a `Preset` — the parameter map — and a mask layer
is deliberately not a parameter. So drawing one changed nothing the history
could see: `record` returned `false`, no step opened, and the layer the
photographer had just painted had no way back. The interface went on calling
`record` in good faith, including from the mask controls, and nothing failed.
A film stock went missing the same way.
The snapshot is an `EditState` now, so the history is complete by
construction rather than by anyone keeping a list in their head.
`undo` and `redo` return a `Step` rather than a `bool`. Stepping is not the
only outcome a caller has to act on — a step across a change of film leaves
the graph without its tables, and only the caller can bake them — and a `bool`
would let that be dropped by writing nothing at all, which is the shape of
mistake this module had already made once. `DevelopSession` settles the debt
either way; a step that found nowhere to go is left alone, since clearing the
film because undo hit the floor would take the stock off the picture.
Five tests, all of which fail against the old snapshot: a drawn layer is
undoable and redoable, a layer's own settings are a step of their own, a
change of stock is a step and names what it needs baked back, clearing the
film is undoable, and an exposure move does not deep-copy the mask stack.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
A history state was a Preset — a map of scalars — which was right while
every edit in the graph was a parameter. A spot is not one, and undo is the
first thing anyone does with a repair: place it, dislike it, take it back.
Left as it was, that press would have stepped some unrelated slider and
left the spot on the photograph, which reads as undo being broken rather
than as undo being absent.
So a state is now the pair, params and spot set. The same door is the one
the mask stack will come through: mask edits are outside undo today for
exactly this reason, and FR-DEV-5 is not finished until they are not.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
A spot is a disc, a source offset and four numbers, and it lives beside
`ops` for the reason `masks` and `film` do: the operation trait is
ParamId -> f32, and a list of repairs is neither scalar nor fixed.
Two decisions here are not obvious. The id is derived from the position
rather than counted, because two devices editing offline would each mint
`spot3` for different marks and the sidecar merge would then treat two
repairs as one — from the position, two devices that removed the same
piece of dust agree, and two that removed different ones do not. And
every length is in the frame's isotropic units, not a mixture of those
and shorter-edge fractions: one unit for the radius, the feather and the
offset agrees on a landscape frame and on a portrait one, where a mixture
only agrees on the first.
`rounds` is the arithmetic that keeps a source from reading a
destination. Every spot in one pass reads the photograph as it stood
before that pass, so a spot sourcing from an earlier spot's destination
would copy the mark that spot was removing. Grouping is not a pass per
spot — that is sixty-four dispatches for a case that almost never arises
— it is a new round only when the sources actually collide.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
dtourolleandClaude Opus 5