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.
