Adds VelocityTracker and a port of AOSP SplineOverScroller's fling curve
(FlingCalculator, cited at the definition) to iris::sense, and wires
List::fling/is_scrolling/cancel_fling/tick_fling through
Selection::drag's release path -- a pan's release now decelerates instead
of stopping dead on the finger lifting, matching IRIS_TODO.md's "swiping
has no momentum" ask. Clamped at the loaded content's start/end and
cancelled by the next touch-down.
Also fixes the scroll jitter DragArbiter's slop release caused: crossing
DRAG_SLOP applied the whole pre-threshold drag (measured from press_start)
in one step, since nothing pans while a gesture might still resolve to a
selection. Now only the excess past DRAG_SLOP is applied on that frame,
the same way Android's own touch handling consumes touch slop rather than
replaying it.
Root-caused by reading DragArbiter's state machine and covered by new
unit tests (fling distance against the closed-form spline result within
1%, cancel-on-touch, start/end clamp, the slop-crossing regression); no
emulator was used this pass, so an on-device trace/feel-check is still
open, and Benchmark v2's four-phase bench_client.rs spec was not
attempted. docs/IRIS.md, docs/IRIS_TODO.md and docs/RUST.md's P0 box
record what's done and what's left.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
irisandClaude Fable 5.1
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