The (a)/(b)/(c) scenarios built their own Span+Scroll pair, so they
never exercised the virtualised widget the transcript screen actually
needs. Rewritten on top of iris::widget::List, plus two new scenarios
from RUST.md's I3: (d) insert-above-anchor (paging older history onto
an already-scrolled list) and (e) expand-a-row-holding-its-edge
(list.rs's note_tap mechanism). Both come out flat across N =
100/1,000/10,000, as required.
Also fixes a real inefficiency this rewrite surfaced: List::place's
"generous" measurement bound was derived from viewport_len, so a
sibling resizing the list itself (the (c) scenario) changed that
bound every tick and defeated draw_inner's same-size fast path,
forcing a full redraw of every visible row instead of a move. It is
now a fixed module constant (GENEROUS_PADDING), independent of the
list's own size -- draws for (c) dropped from 3059 to 684 over 40
ticks.
cargo test -p iris (5 List tests still pass), cargo clippy
--all-targets and --benches --release, cargo fmt --all -- --check all
clean. Numbers recorded in RUST.md's I3 box.
Co-Authored-By: Claude Sonnet <noreply@anthropic.com>
irisandClaude Sonnet
03da47e550