Building the I3 example (800 rows, some with images, styled with
.background(rect(tint))) surfaced a real bug: place()'s Bottom-known
branch measured a row at an oversized, fixed-size region and moved it
into its final box with reposition -- a pure translation. That is
correct for wrapped text, whose reported height doesn't depend on the
height it was offered, but Rect (used for every row's background) is
is_size_independent because it fills *whatever region it is given*,
so it painted at the oversized size and reposition never shrank it
back down. The screenshot showed one oversized tinted rectangle
covering the whole visible window instead of per-row backgrounds.
Fixed by caching each row's height once measured and placing an
already-measured row directly at its exact box (one widget_within/
reposition pass, same as any known-size placement) instead of
re-measuring every frame. A first-ever appearance still pays a
two-draw measurement (draw_twice), and a row whose real height
changed since it was cached is corrected the same frame it redraws
(not a one-frame lag) via an explicit reposition when the two
disagree. Steady-state scroll cost is unaffected: an unchanged row's
single placement call still hits draw_inner's existing skip-or-move
fast path.
Also fixes repair_anchor unconditionally re-snapping a bottom-anchored
list's offset to the viewport's edge on every frame snap_end was true
-- which discarded a live scroll() call the moment it ran, since
snap_end is only recomputed at the end of a layout pass and so still
read true from before the scroll. Now only re-snaps when the viewport
itself actually resized (tracked via last_viewport_len).
Added a_fill_shaped_background_is_not_left_oversized, a direct
regression test for the background bug (checks the background rect's
own painted pixel size, not just the row's reported extent, which was
already correct). cargo test -p iris (26 passed), clippy --all-targets
and --benches --release, fmt --all -- --check all clean. Rebenched:
all five scenarios still flat across N = 100/1,000/10,000 (numbers in
RUST.md's I3 box). Visually verified via
run-headless.sh message_list --shot, cropped with a throwaway PNG
decoder since no image tooling is installed here.
Co-Authored-By: Claude Sonnet <noreply@anthropic.com>
irisandClaude Sonnet
e898370bf4