Wrapping the composer's field in .scrollable().masked() needed three
layout defects fixed first, each with a headless regression test that was
confirmed to fail without its fix:
- MaxSize/Sized reported a caller's declared dp length unresolved, and
Span places a child from the abs/rel of what it reported, so dp(168)
was worth zero: the bar got a slot of nothing the moment its content
passed six lines and the Scroll inside measured its container at -63px
(container=-63 content=415.8 amt=478.8 on the emulator). Len::fold_dp,
used on the way out, plus a debug_assert in draw_inner that a reported
Size carries no dp -- the rule is about every widget, not those two.
- Masked allocated a fresh mask slot per draw, and draw_inner's
unchanged-region fast path does not revisit descendants, so they kept
clipping against a box the bar had moved away from: four live mask
entries, none of them current, and the field drew nothing.
ActiveData::own_mask, allocated once and rewritten in place.
- mov updates active.region and accumulates the same delta on the move
slot, and resolved_region added both, so a panned widget's own hit box
sat at twice the pan -- the composer's field was untappable after a
drag. ActiveData::move_applied.
Scroll itself measured the right number by a misleading route; it is
written against painter.px_size() now and still reports its content's
size, since reporting the container makes the answer a function of
itself.
Verified on this checkout's emulator: swipe 540 1200 -> 540 1460 moved
the field's Message box 31,1041..1048,1509 -> 31,1131..1048,1651 with its
height unchanged at 468px.
run-bench.sh polled logcat for a prefix copy_report also logs at startup,
so it printed a report that had never been run.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>