User ruling 2026-09-20: minimise the amount of new code a new UI framework
needs. Centralise logic in a redux-like store so a second or third front end
is a function from state to pixels plus a wire for events, not a second
implementation of how the application behaves.
Names the pieces that already exist as what they are -- Command is the
action, reduce_view and WidgetCache::apply are the reducer, ViewState plus
the caches are the store, Sessions::apply is dispatch -- and gives the
question to ask of any front-end code: would a third front end have to write
this again?
Three things make it concrete: the measure is lines of framework-specific
code and should trend to 'paint and wire'; a derivation done twice is the
defect even when both copies are correct today (improvise-edp is the worked
example, gotcha 44 is the same defect still open); and sharing a table beats
testing two copies of it, which is why the keymap is shared rather than
mirrored. Also says what legitimately stays local: painting, event wiring,
and a semantic-value-to-framework-type lookup like AxisColor -> axis_fg.
Sections 5-7 renumbered; the §6 testing references in repo-map.md and the
code-review skill updated with them.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EoW5BB87ZZdm96SvBTWawH
Edward Langley
d175b9934f