The poster's two ugliest defects were engine policy, not model declarations:
- A column stretched by its siblings distributed the slack into gaps (and,
via grow, into boxes), producing huge panels with three lines floating in
the middle. Slack policy now differs by axis: a ROW still spreads and
centres (a flowchart layer reads as a pyramid), a COLUMN packs to the top
and leaves leftover space at the bottom — where a reader expects it.
- Multi-line body text rendered dead-centre (FALLBACK_BOX's
verticalAlign=middle). Typography's basic rule, applied by content: a
paragraph (explicit breaks or wrap-length text) sets align=left,
verticalAlign=top with padding; a short label stays centred. Rectangles
only — inside a rhombus or cloud the safe text area IS the middle.
- Prompts corrected: stretch is about width, content keeps natural height,
and columns are balanced by moving content — not by inflating boxes.
565 tests green; the same poster declaration re-rendered without the giant
hollow panels.
The expressiveness gap traced to vocabulary: draw.io has hundreds of shapes,
the declarative layer allowed six. Opening it, with the failure modes from
design review handled:
- shapes.ts: a ~20-entry curated catalog (full style fragment incl. the
matching perimeter — required or edges connect to the bounding box; a
text-scale factor verified in the real editor — the same sentence overflows
a 1.0x rhombus and fits a 1.5x one; labelOutside+glyph for umlActor-style
figures). Any other token passes through verbatim: draw.io degrades unknown
shapes to rectangles safely (verified). Injection-capable tokens (;/=) are
rejected outright.
- Pass-through emits a WARNING with a nearest-catalog hint (bounded edit
distance), so a typo'd 'cyclinder' is a one-turn fix instead of a silently
rectangular node forever. set_shape/set_role/set_group operations make the
fix possible without remove+re-add (which would drop links).
- mergeStyle(): style fragments merge per-key (later wins, bare shape classes
displace each other) instead of string concatenation. This is what makes
shape and theme composable by rule — shape owns geometry keys, theme owns
colour/type keys, and an overlap resolves by order instead of emitting
contradictory duplicates.
- dai_shape marker carries the declared token through the round trip:
appearance-based reverse mapping cannot distinguish aliases (diamond vs
decision) or a rotated queue from a cylinder.
- dai_auto marker separates engine-measured size from user-fixed size: parsed
boxes no longer freeze the first layout's numbers, so changing a label
re-measures. Pinned nodes keep everything, as before.
- draw_graph's closed shape enum opened to match (first instance of the
schema-drift problem the review predicted).
14 new tests: merge ownership, injection rejection, near-match hints,
alias-preserving round trip, re-measure on label change, mxgraph.* tokens
staying boxes with role/group intact. 556 unit tests green; acceptance
diagram (person/hexagon/cylinder/queue/cloud/decision/callout) verified in
the real editor.
The expressiveness gap between engine output and hand-written XML came down
to two missing capabilities, both generic:
- Block layout inside a box: nested containers already existed, but there was
no way to split space by weight, pin a child to an edge, or tighten padding.
Added grow (flex-grow over the parent's leftover flow-axis space, TeX's
glue), align (start/center/end/stretch on the cross axis) and pad
(per-group interior padding). All three round-trip via dai_grow/dai_align/
dai_pad markers.
- Inline rich text: labels already render HTML (html=1 on every style, esc()
entities decode back), but the measure pass counted markup as text. The
visibleText() strip makes autoBoxSize measure what draw.io draws: <br> is a
line, other inline tags are invisible.
Graphviz (HTML-like table labels), D2 (grid containers + markdown-in-shape)
and TeX (box+glue) converged on exactly this design: nested boxes for block
structure, proportional glue, a small inline set for text — never full HTML.
Prompts teach the composition with a comparison-card recipe; verified by
rebuilding the CoT poster end to end in the real editor.
Paper-summary posters previously required hand-written XML: every engine
box rendered identically (white, 11px), so anything whose meaning lives
in visual hierarchy came out flat. This makes presentation a first-class,
generalised part of the declaration - not a poster feature.
Structure/presentation separation, the same split HTML and CSS settled on:
- ROLE says what a node IS: banner, heading, body, callout, good, bad,
metric, muted. Maps to a type scale and an emphasis (filled / tinted /
outlined / ghost), never to a colour.
- GROUP says which semantic zone a node belongs to. Each distinct group
name gets one hue ramp (tint / base / dark), assigned in document
order. Promoted from a draw_graph-only field to BoxNode and GroupNode,
round-tripped via dai_group.
- themedStyle(role, hue, kind) composes the two by rule - there is no
per-combination table to extend, so a new diagram kind gets full
theming by tagging nodes. The model never sees a hex value.
A heading container plus a group yields the tinted section panel with a
dark title; a grouped body box takes its zone's tint; verdict roles stay
green/red regardless of zone; the banner is the page's one dark field.
Also fixed, found while building the acceptance poster:
- autoBoxSize only counted explicit newlines, so a long single-line label
wrapped to six lines in draw.io but got a one-line-tall box, and the
text overflowed the cell.
- Marker stamping appended without replacing, so every render of a
recovered style grew it by one duplicate dai_* token per key -
unnoticed because draw.io resolves duplicates last-wins. dai_* keys
are now replaced in place; mxGraph keys still append, because
last-wins is load-bearing for container=1 normalisation.
- Banner/heading/metric roles stretch across their container's cross
axis, the way a masthead spans its page.
- Prompt: a poster's banner IS its title (no set_title alongside), and
sections get their colour by naming groups.
537 unit tests, 250-flowchart corpus still zero crossing arrows, 5 e2e
tests in a real browser. Verified visually: the Transformer-paper poster
renders with a navy masthead, three hue-coded section panels, metric,
verdict and callout boxes - all engine-computed geometry.
Four reviewers went over the previous commit (three Claude, one Codex). Their
findings, verified independently before applying:
A REAL BUG. A vertical pool with milestone labels drew the label strip outside
the pool frame. The measure pass reserves width as padding + content + strip with
no gap between the last two; the renderer placed the strip one gap further out.
No test caught it because every vertical case omitted phases and every phases
case was horizontal — both regression cases added.
Duplicated logic, now single-sourced:
- messageCount existed byte-identically in layout.ts and render.ts. Two copies
that had to agree or the lifelines stop reaching the last message.
- sequenceMetrics was called twice per sequence container, once inside the
chrome builder and again for the message positions. Same drift hazard, in the
file whose own comment warns about it.
Dead code, each verified unreachable rather than assumed:
- Placed.extent: declared and documented, never written or read. Every .extent
access belongs to RadialTree.
- SequenceMetrics.top: computed, returned, no reader.
- spread()'s level parameter: threaded through the recursion, never used.
- radialReach's .slice(0, generations): widestPerLevel writes one entry per
generation, so its length IS the depth. Confirmed over 20,000 random trees;
removing it made RadialTree.depth dead too.
- Two of three cycle guards in radialHierarchy: self-links are already skipped
when the parent map is built, and that map holds one parent per node, so the
structure is a forest and the visited-set filter cannot fire. The rootOf
guard does fire and stays.
- GraphOptions.layerGap/nodeGap/idPrefix: no caller, not in the tool schema.
Simplifications:
- LayoutContext wrapped a single field; the link array now passes directly,
which also removes the NO_CONTEXT default no call site ever took.
- stretches() and the mirror-image check five lines below it expressed one rule
two ways; unified, with the rationale stated once.
- hasStencilFrame/isDirectional: one caller each, and isDirectional's name
contradicted its body, which the guarded branch then re-discriminated anyway.
- poolFrameStyle() took no arguments and had one caller.
- poolCellOf clamped a value already clamped at the model boundary and
unreachable-by-construction from the parser.
- A comment on stampPoolDecoration described container behaviour the function
does not implement.
Kept deliberately, with evidence:
- The best-arrangement tracking in the crossing reducer. Two reviewers
suspected it was dead weight. Measured: barycentre sweeping regressed below
its own running best in 180 of 500 random graphs, so without it a third of
flowcharts would keep a worse arrangement than one already found.
- Vertical pools. Two reviewers recommended deleting the feature as
undiscoverable. The bug was one line, and vertical swimlanes are a real
convention — documented to the model instead, which is what was actually
missing.
- styleValue duplicating readMarker, isLeaf, findPageIndex: all genuinely
redundant, all predating this branch. Left alone to keep the diff scoped.
525 unit tests and 11 diagram e2e tests pass.
Extends the declarative engine past cloud architecture. The tool routing was
divided by icon library — AWS through the engine, everything else hand-written
XML — which is the wrong axis. What matters is the LAYOUT SHAPE.
Measured first: a six-step approval flow declared in its natural order comes out
as one column, because the layout only arranges what nesting tells it to and
never looked at the arrows. That forces the arrow from the decision to its second
branch to jump over the first branch.
graph.ts computes what the layout should have looked at: layer assignment by
longest path, cycle breaking so a loop is drawn without setting the order, and
barycentre sweeping to cut edge crossings. It emits ordinary container
operations, so layout, routing and round-tripping are unchanged — reaching zero
arrows-through-boxes on a 14-node pipeline and zero crossings on a bipartite
graph whose declared order forces three.
Three new container kinds, each because one layout rule cannot serve them all:
pool — swimlanes. Lanes are real cells and each step is parented to its
band, so dragging a step to another role records the change.
sequence — participants across the top, one lifeline cell per participant so
head and line stay together on a drag. Messages bypass the router:
a message's height IS its order.
radial — mind maps and org charts. Children are a flat list and the
hierarchy comes from the links, because a branch is a box and a box
cannot hold children.
Flowchart box shapes (diamond, stadium, parallelogram, document) so a reader can
tell a branch from a step.
Two bugs the new tests caught: the duplicate-link guard blocked a sequence
diagram from having two messages between the same pair, and the fallback message
numbering was shared across containers, pushing a second diagram's messages off
its own lifelines.
523 unit tests and 17 diagram e2e tests pass. Every kind verified round-trip
stable to a fixed point, and rendered in a real browser — draw.io keeps the
lifeline shape and the lane markers.
Completes the tree → coordinates → XML direction, so the model can declare nesting
and never write a coordinate or an mxCell again.
layout.ts — measure bottom-up, place top-down, the same shape as flexbox. A
container sums its children along the flow axis and adds padding, so "child spills
out of its frame" and "siblings overlap" cannot happen by construction rather than
being caught afterwards. Slack from sibling equalisation is shared between children
instead of left as dead margin, capped at one gap so a stretched frame reads as
spaced rather than sparse.
render.ts — writes the mxCells, stamping container=1 and the dai_* markers so
parse.ts can read the structure back. Edges carry no waypoints: draw.io's own router
recomputes the route on every edit, so a user who moves a node never has to re-link
an arrow. Cells the parser could not interpret are re-emitted verbatim, so a
re-layout never deletes a user's annotations.
Phantoms are gone (task #5). The reference project's layout-only wrapper emits no
cell, which makes the round-trip lossy by construction — measured on its own
build_vpc.mjs, a phantom erased a container's "col" direction for good. An
unlabelled frame here emits a real cell with fillColor/strokeColor=none instead:
invisible, but present in the XML and therefore recoverable.
Two bugs the round-trip test caught, both real:
- An icon's cell was being emitted at its measured slot size, which includes room
for the label underneath. Parsing read that width back as the glyph size, so the
icon grew on every round-trip. The cell is now the glyph square and the label
renders outside it via verticalLabelPosition, as the reference does.
- An Azure or GCP icon is an embedded base64 image whose style contains no name
anywhere, so the catalog name was unrecoverable. Added a dai_name marker.
Verified in a real browser (3 Playwright tests, not mocks): engine output renders in
draw.io; dragging a shape into a frame makes draw.io rewrite its parent and the
engine reads the new structure back; re-laying out from that structure PRESERVES the
user's move instead of undoing it, and leaves untouched nodes alone; and the
re-laid-out XML still renders.
That last point is the whole design: there is no second copy of the state, so a
manual edit is an input to the next layout rather than a conflict to reconcile.
304 unit tests + 3 e2e.
