Making a lane one row cost the thing a row was for. A clip stopped being a row,
so there was no longer any way to open a clip and see what was inside it, and
the inside of a drawing — the most ordinary thing in the document — became
reachable only by opening it as its own tab. This is that capability back,
from the root timeline, down as far as it goes.
An expanded lane opens exactly ONE clip: the selected one. Its own keys, then
the lanes and nodes of the symbol it places, then theirs, each mapped into this
ruler by the recursive walk that was already there. Twelve clips in a lane
still cost one row, and inspection costs one branch rather than twelve.
Two things that only showed up once it ran. The portal is chosen by the whole
LINEAGE of the selection and not by the selected id: selecting a shape inside
the clip — or the end of its span — is still working inside that clip, and
matching the id alone shut the portal the instant anything under it was
touched. And selecting now waits for the pointer to come UP, because selecting
on the way down re-drew the timeline before the gesture had said anything: it
shut the portal holding the lane being dragged INTO, out from under the
pointer.
A HELD clip opens too, which the old row walk never did either. `source-time`
is nil for a hold, so the walk stopped there and the contents of every drawing
were invisible from here. Its rows are shown across the hold — which is when
the node is on screen — and marked `:unmapped?`: no keys, and no draggable
edges, because a frozen clock gives no frame inside it a place on this ruler.
Refusing to place the keys is the honest half; refusing to show the rows was
not.
Double-clicking a clip opens the symbol it places as a tab, as double-clicking
the same symbol in the pool does. That was already written and had never once
run: the track captures the pointer for a slide, so the click and double-click
that follow are delivered to the track and never to the block. The track now
resolves them itself. Fixing the delivery exposed two more: `symbol/lineage`
reported a `parent cycle` for any id in a symbol with NO nodes, because a
one-element chain is longer than zero nodes — and opening a symbol left the
selection pointing into the symbol being left, which the breadcrumb and the
inspector then tried to resolve. The editor unmounted. Both are fixed where
they were wrong, and the browser test asserts the editor is still standing
afterwards.
Audio is a clip in a lane like everything else. A dropped sound lands in one
and is trimmed and moved by the same commands; a lane holds picture or sound
and not both, which is the explicit capability the model asked for rather than
a guess per frame. The refusal lives in the commands and not only in
validation, because placement claims time: `blank` would have deleted the
sound to make room for the picture and left a perfectly valid document behind.
What is in a lane of the open symbol is drawn as a lane; what is nested inside
a placed symbol is still flattened by `audio-tracks`, so no sound is on two
rows.
Everything that enters the timeline now enters a lane: a converted take, a
symbol brought in from another project, a sound. One rule answers where —
`lane-destination` — and every symbol is born with a lane for it to answer
with. An unaimed drop fills an EMPTY lane rather than taking an occupied one
nobody pointed at, because the alternative is trimming away what was there to
make room for what was dropped.
Shift during a clip-body drag means the other intention: put this node INSIDE
the symbol the clip under the pointer places, through `nest/move-node`, which
is what keeps the world transform and the root timing. Overlap cannot say
which of the two is meant — dropping on occupied time already means claiming
it — so the person says, and a label by the pointer says it back. The label
asks `nest/move-refusal`, the same check the command makes, so it cannot
promise what the drop would refuse. Today it refuses more than it allows:
both clips have to be on screen at one frame, which two clips in one lane
never are, and a held destination has no clock to move through at all.
`docs/lane-nesting-notes.md` argues that the second refusal is stronger than
the facts require and says what would settle it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A lane's drawings were going to be one instance whose source was a KEYED
channel: frame 0 says `:drawing-a`, frame 4 says `:drawing-b`, and the cels of
a row are that channel's keys. Two things followed from it, and both were
wrong.
The first is that playback meant whichever shape the channel happened to have.
A framed source played its symbol; a keyed source froze the selected frame.
So `node/placed-at` read animation out of storage, and adding an ordinary key
to a still turned it into an animation — the last-key bug, which was not a bug
in the code so much as the rule working as written. But WHICH drawing is used
and HOW time runs inside it are independent questions, and all four combinations
are ordinary: hold one drawing, play one animation, cut between held drawings,
cut between playing ones.
So an occurrence names one symbol in `:source {:symbol ...}` and says how its
source time advances in `:playback {:in :speed :end}` — `source = in + speed *
f`, a hold being speed 0, with `:stop`, `:hold` or `:loop` at the end named
rather than guessed. `node/placed-frame` samples it forwards, which works for
holds too, and `node/source-time` is the separate, invertible edit map, nil
where inversion is meaningless. The two were one function before, and a hold
had to lie about one of them.
The second is that a keyed source only looked necessary because an occurrence
was assumed to need a ROW. It does not. A lane is a group with `:layout
:sequence`, its occurrences are ordinary instances in the same flat node map,
and `timeline/rows` draws them as cel blocks on the lane's own row: twelve
exposures, one row, each cel still separately selectable and addressable. The
vertical growth that justified the keyed source is a presentation question, and
it is answered in the view.
`arthur.domain.sequence` holds the first commands over that shape — add lane,
append drawing, extend hold — each one history step, each refusing rather than
half-applying. Extending a hold leaves the lane's keys at their authored times,
because you are adjusting drawings underneath timed motion; a correction owned
by an occurrence travels with it. Ownership does that work, so no key needs a
flag saying what it follows. Ripple past the symbol's end is refused with the
frame count it would need, and `:extent :grow-symbol` is the caller saying yes.
`clip/blank` no longer carries `:subjects {} :features {} :groups {}`. Empty
maps write no leaf, so a blank document could not survive its own round trip —
`leaf/leaves` promises exactness and was the only honest side of that.
Documents are schema 3. A version 2 document is not read; nothing here converts
one. `docs/lane-model.md` is the design, and says which of its parts are built.
392 tests, 5,525 assertions, and `test/browser/sequence.mjs` drives the editor
through create, hold, explicit overflow and undo.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
domain/clip is the document and what only needs the document: its symbol
table, placing, the resolver, problems. domain/nest is how nested symbols
relate — one walk down a row path gives the frame, the matrix and the time
map, which merges inside and time-down — and moving and grouping between
them, and nested sound. domain/bring is copying symbols in from another
clip, a take from footage, and one placed that merges the store and places
the instance, which conversion and import both now call instead of each
doing it in their own words. Tests follow the same split.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
