Four more Tailwind classes, all four verified against draw.io's own source in
public/drawio rather than against a prose reference — which is how three earlier
exclusions turned out to be wrong:
rounded-* mxShape.js:1172-1189 — absoluteArcSize=1 switches arcSize to
absolute pixels and halves it, so the same class is the same
corner on every box. Previously excluded as 'percentage only'
shadow-sm..xl mxShape.js:505-535 — getShadowStyle reads five independent
params, not one flag, so Tailwind's offset+blur rungs map one
to one. Previously excluded as 'six sizes collapse to one'
line-through mxConstants.js:2054 FONT_STRIKETHROUGH: 8, read at both
mxText.js:723 and :1040. The bitmask has four bits, not three
border-none the only one of the four that adds something previously
inexpressible: a fill with no outline
Also fixes an edge style growing 76 characters per re-layout, without bound. The
router recomputes ports on every pass, and appending them to a style recovered
from the canvas — which already carried the previous pass's eight port keys —
grew the string forever. draw.io resolves duplicates last-wins so the arrow
always looked right; a byte-identity check is what caught it.
Two traps found while wiring the readback, both the same shape: a value the
THEME emits being recorded as one the model asked for. strokeColor=none from a
filled or ghost role, and rounded=0 from the fallback style. Either one would
outlive a set_role, since that clears style but keeps text.
Deliberately not included, with reasons in tw.ts: per-side borders and per-corner
radius (both would take the shape slot, and what a node IS matters more than
which of its edges show), per-side padding (draw.io's keys pad the label, not the
room left for children), text-shadow (a bare flag with no offset or blur),
opacity (Tailwind's is any integer, not a scale), tracking/uppercase/leading
(absent from draw.io — zero grep hits, not merely coarse).
615 tests, 90 new. Browser-verified: four shadow rungs visibly differ, radius is
real pixels, terminator + rounded-lg becomes a small-cornered rounded rect while
an untouched terminator stays a stadium.
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.
Groundwork for a declarative diagram engine where the model declares nesting and
the engine computes every coordinate, instead of the model emitting raw mxCell XML.
The design keeps the canvas as the SINGLE source of truth: the node tree is never
persisted, it is re-derived from the current canvas XML whenever needed. A user's
manual edits are therefore an input to the next re-layout, not a second copy of
the state that has to be reconciled.
Two behaviours this relies on, both verified against the real embedded editor with
a Playwright mouse drag (reading the editor's own autosave payload):
1. An AWS group stencil WITHOUT container=1 does not get a dragged shape
reparented — parent stays "1" and geometry stays absolute. WITH container=1
it does: parent becomes the frame, geometry becomes parent-relative. So the
engine must stamp container=1 on every container it emits.
2. draw.io preserves style keys it does not understand, and resolves a duplicate
key last-wins. So dai_* markers survive a user edit, and container=1 can be
appended to a catalog style without first parsing out an existing value —
which matters because the AWS catalog is inconsistent about it (group_vpc,
group_region, group_subnet ship without it; group_account ships with it).
markers.ts — dai_kind / dai_dir / dai_gap / dai_cols / dai_pin, and the container
token normalisation.
types.ts — the node tree contract, plus a `foreign` bucket so cells the engine
does not understand (user annotations, imported shapes) round-trip
verbatim rather than being destroyed by a re-layout.
parse.ts — XML → tree. Handles all four icon encodings (resIcon=, bare shape=,
shape=image data URI, grIcon=), resolves nesting from parent with a
geometry fallback for frames that lack container=1, recovers layout
direction from the marker or infers it from child positions, and
survives cycles, compressed files and multi-page decks.
75 unit tests, including a round-trip against real output from the reference
project's build_vpc.mjs.
One finding worth recording: the reference project's "phantom" node (a wrapper that
participates in layout but emits no cell) makes the round-trip lossy by
construction. In build_vpc.mjs a phantom erased a container's col direction — its
children were reparented onto the grandparent, leaving a 2-D arrangement the parser
can only read as a grid. 26 of the reference project's 31 examples use phantoms, so
our engine needs an invisible-but-real container instead. Tracked separately.
