irisandClaude Opus 5
02b277e7ad
Iris, 2026-09-08: "Flinging doesn't work in horizontal scroll areas.
Flinging should be enabled by default in all scroll areas on android to
match composes behavior." Compose's `scrollable` attaches
`ScrollableDefaults.flingBehavior()` on every axis it is given and it is
not something a caller opts into, so neither is this.
`iris::sense::Flinger` is the fling `List` already had, taken out of it:
the `FlingCalculator` curve, the clock (started at the first tick, not
the release, so a caller on an explicit clock is not handed a fling that
has already expired), the incremental delta, Compose's two release
thresholds and the trace line. What it deliberately does *not* know is
which way a positive delta moves the content or whether there is content
left to move into -- a `List` scrolls its anchor one way and a `Scroll`
moves its `amt` the other, so the caller applies `tick`'s delta in its
own convention and calls `stop` at its own wall. `List` keeps
`fling`/`tick_fling`/`is_scrolling`/`cancel_fling` unchanged as a
surface, now three lines each over the shared type.
`Scroll` gains it, plus the two things a coasting widget needs and it
had no reason to have before: the display density (read from the painter
in `draw`, since the deceleration is physical -- a hardcoded 1.0 made a
one-second coast run for 45 on a list), and `PressState::scrolling`, so
a finger put down on a coasting fence stops it there from the first
sample rather than after `DRAG_SLOP`. `Scroll::drag` now answers whether
it started a fling, which is what `WidgetLike::scroll_area` needs to
call `UiData::animate` -- the same split `List::fling`'s doc describes,
and for the same reason: only the caller can reach the frame loop.
`Scroll::axis()` is public for a caller that found the widget rather
than built it.
Tests: `scroll.rs`'s three (a released pan coasts and decelerates on both
axes; both walls stop it; a press on coasting content catches it with no
slop), and `transcript-fixture/tests/fence_fling.rs`, which flicks a real
markdown fence in the real transcript screen and reads the fence's own
`Scroll` back out of what was drawn. Confirmed to fail with the release
arm removed ("the fence stopped dead at the release: 272 -> 272").
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>