From f089ef9db4e42ba35d745e449febc57f31b5e0a8 Mon Sep 17 00:00:00 2001 From: Claude Date: Fri, 19 Jun 2026 22:38:20 +0000 Subject: [PATCH] fix: stop DisappearingScaffold bars overshooting their resting edge MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The settle/reset animation drove a critically-damped spring with the fling's leftover velocity. A critically-damped spring does not oscillate from rest, but when handed an initial velocity in the target's direction its response still crosses the target once before decaying back. On a fast reveal fling the top bar's offset shot well past 0 (measured ~+190px in a test) — rendering the bar sliding below its resting position and springing back, the "goes beyond its final position and then comes back" wobble that only appeared on fast flings. Clamp the settle Animatable to the visible travel range [-limit, 0] via updateBounds, so hitting an edge ends the animation crisply with no rebound. Add a regression test that steps the settle under a manual frame clock and asserts the offset never crosses the resting edge. Co-Authored-By: Claude Opus 4.8 (1M context) Claude-Session: https://claude.ai/code/session_01EEGCrB5uRBAZES1PSp4Ctz --- .../ui/layouts/DisappearingBarState.kt | 16 +++- .../ui/layouts/DisappearingBarStateTest.kt | 96 +++++++++++++++++++ 2 files changed, 108 insertions(+), 4 deletions(-) create mode 100644 amethyst/src/test/java/com/vitorpamplona/amethyst/ui/layouts/DisappearingBarStateTest.kt diff --git a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/layouts/DisappearingBarState.kt b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/layouts/DisappearingBarState.kt index d426b09e7d..8d743246db 100644 --- a/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/layouts/DisappearingBarState.kt +++ b/amethyst/src/main/java/com/vitorpamplona/amethyst/ui/layouts/DisappearingBarState.kt @@ -86,8 +86,8 @@ class DisappearingBarState( */ suspend fun resetToVisible() { coroutineScope { - launch { animateOne({ topHeightOffset }, 0f, 0f) { topHeightOffset = it } } - launch { animateOne({ bottomHeightOffset }, 0f, 0f) { bottomHeightOffset = it } } + launch { animateOne({ topHeightOffset }, 0f, 0f, topHeightLimit) { topHeightOffset = it } } + launch { animateOne({ bottomHeightOffset }, 0f, 0f, bottomHeightLimit) { bottomHeightOffset = it } } } } @@ -110,19 +110,27 @@ class DisappearingBarState( positionBiasToHide -> -limit else -> 0f } - animateOne(get, target, initialVelocityY, set) + animateOne(get, target, initialVelocityY, limit, set) } private suspend fun animateOne( get: () -> Float, target: Float, initialVelocity: Float, + limit: Float, set: (Float) -> Unit, ) { val start = get() if (start == target && initialVelocity == 0f) return Animatable(start) - .animateTo( + .apply { + // Clamp to the visible travel range. A critically-damped spring still crosses its + // target once when given an initial velocity in the target's direction, so without + // these bounds a fast reveal fling would push the offset past 0 (or past -limit on + // a hide) and render the bar overshooting its resting edge before springing back. + // Hitting a bound ends the animation at the edge — a crisp settle with no rebound. + if (limit > 0f) updateBounds(lowerBound = -limit, upperBound = 0f) + }.animateTo( targetValue = target, animationSpec = SETTLE_SPRING, initialVelocity = initialVelocity, diff --git a/amethyst/src/test/java/com/vitorpamplona/amethyst/ui/layouts/DisappearingBarStateTest.kt b/amethyst/src/test/java/com/vitorpamplona/amethyst/ui/layouts/DisappearingBarStateTest.kt new file mode 100644 index 0000000000..bae001b849 --- /dev/null +++ b/amethyst/src/test/java/com/vitorpamplona/amethyst/ui/layouts/DisappearingBarStateTest.kt @@ -0,0 +1,96 @@ +/* + * Copyright (c) 2025 Vitor Pamplona + * + * Permission is hereby granted, free of charge, to any person obtaining a copy of + * this software and associated documentation files (the "Software"), to deal in + * the Software without restriction, including without limitation the rights to use, + * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the + * Software, and to permit persons to whom the Software is furnished to do so, + * subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in all + * copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS + * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR + * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN + * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION + * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. + */ +package com.vitorpamplona.amethyst.ui.layouts + +import androidx.compose.runtime.BroadcastFrameClock +import kotlinx.coroutines.ExperimentalCoroutinesApi +import kotlinx.coroutines.launch +import kotlinx.coroutines.test.TestScope +import kotlinx.coroutines.test.runCurrent +import kotlinx.coroutines.test.runTest +import org.junit.Assert.assertEquals +import org.junit.Assert.assertTrue +import org.junit.Test + +class DisappearingBarStateTest { + private fun state( + topLimit: Float = 100f, + bottomLimit: Float = 50f, + ) = DisappearingBarState().apply { + topHeightLimit = topLimit + bottomHeightLimit = bottomLimit + } + + /** + * Runs [block] (a settle/reset animation) under a manually-stepped frame clock, sampling both + * offsets after every frame. Returns the highest (closest-to-or-past zero) value each offset + * reached — a bar overshooting its fully-visible resting edge briefly pushes its offset above 0. + */ + @OptIn(ExperimentalCoroutinesApi::class) + private fun TestScope.peakOffsetsDuring( + state: DisappearingBarState, + block: suspend () -> Unit, + ): Pair { + val clock = BroadcastFrameClock() + var maxTop = state.topHeightOffset + var maxBottom = state.bottomHeightOffset + + val job = launch(clock) { block() } + runCurrent() + + var frameNanos = 0L + val frameStep = 16_000_000L + // Hard cap so a regression that never settles fails the test instead of hanging it. + repeat(2_000) { + if (!job.isActive) return@repeat + frameNanos += frameStep + clock.sendFrame(frameNanos) + runCurrent() + maxTop = maxOf(maxTop, state.topHeightOffset) + maxBottom = maxOf(maxBottom, state.bottomHeightOffset) + } + assertTrue("animation did not settle within the frame budget", !job.isActive) + return maxTop to maxBottom + } + + @Test + fun `a fast reveal fling settles at the visible edge without overshooting`() = + runTest { + val state = state(topLimit = 100f, bottomLimit = 50f) + // Mid-collapse, as a reveal fling leaves the bars when the list hits the top edge. + // Settling toward the visible edge (0) with a strong reveal velocity is what made the + // critically-damped spring shoot past 0 before the fix clamped it. + state.topHeightOffset = -40f + state.bottomHeightOffset = -20f + + val (peakTop, peakBottom) = + peakOffsetsDuring(state) { + state.settleToNearestEdge(initialVelocityY = 12000f) + } + + // Lands exactly on the visible edge... + assertEquals(0f, state.topHeightOffset, 0.01f) + assertEquals(0f, state.bottomHeightOffset, 0.01f) + // ...and never travels past it on the way there (no slide-down-then-back wobble). + assertTrue("top bar overshot to $peakTop", peakTop <= 0.5f) + assertTrue("bottom bar overshot to $peakBottom", peakBottom <= 0.5f) + } +}