Merge changes from topic "stl-swipe-source" into main

* changes:
  Extract compute(Swipes,SwipesResults) in SceneGestureHandler
  Enforce that onDragStarted.overSlop is != 0f
  Migrate Modifier.swipeToScene to the Modifier.Node API
  Replace swipe Edge (detector) by SwipeSource (detector) (1/2)
  Make STL swipe distances configurable
diff --git a/packages/SystemUI/compose/features/src/com/android/systemui/communal/ui/compose/CommunalContainer.kt b/packages/SystemUI/compose/features/src/com/android/systemui/communal/ui/compose/CommunalContainer.kt
index a22fecf..4fdcf75 100644
--- a/packages/SystemUI/compose/features/src/com/android/systemui/communal/ui/compose/CommunalContainer.kt
+++ b/packages/SystemUI/compose/features/src/com/android/systemui/communal/ui/compose/CommunalContainer.kt
@@ -84,13 +84,14 @@
     SceneTransitionLayout(
         state = sceneTransitionLayoutState,
         modifier = modifier.fillMaxSize(),
-        edgeDetector = FixedSizeEdgeDetector(ContainerDimensions.EdgeSwipeSize),
+        swipeSourceDetector = FixedSizeEdgeDetector(ContainerDimensions.EdgeSwipeSize),
     ) {
         scene(
             TransitionSceneKey.Blank,
             userActions =
                 mapOf(
-                    Swipe(SwipeDirection.Left, fromEdge = Edge.Right) to TransitionSceneKey.Communal
+                    Swipe(SwipeDirection.Left, fromSource = Edge.Right) to
+                        TransitionSceneKey.Communal
                 )
         ) {
             // This scene shows nothing only allowing for transitions to the communal scene.
@@ -101,7 +102,7 @@
             TransitionSceneKey.Communal,
             userActions =
                 mapOf(
-                    Swipe(SwipeDirection.Right, fromEdge = Edge.Left) to TransitionSceneKey.Blank
+                    Swipe(SwipeDirection.Right, fromSource = Edge.Left) to TransitionSceneKey.Blank
                 ),
         ) {
             CommunalScene(viewModel, modifier = modifier)
diff --git a/packages/SystemUI/compose/features/src/com/android/systemui/scene/ui/composable/SceneContainer.kt b/packages/SystemUI/compose/features/src/com/android/systemui/scene/ui/composable/SceneContainer.kt
index c35202c..9f9e1f5 100644
--- a/packages/SystemUI/compose/features/src/com/android/systemui/scene/ui/composable/SceneContainer.kt
+++ b/packages/SystemUI/compose/features/src/com/android/systemui/scene/ui/composable/SceneContainer.kt
@@ -183,7 +183,7 @@
         is UserAction.Swipe ->
             Swipe(
                 pointerCount = pointerCount,
-                fromEdge =
+                fromSource =
                     when (this.fromEdge) {
                         null -> null
                         Edge.LEFT -> SceneTransitionEdge.Left
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/EdgeDetector.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/EdgeDetector.kt
index 82d4239..b0dc3a1 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/EdgeDetector.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/EdgeDetector.kt
@@ -23,24 +23,19 @@
 import androidx.compose.ui.unit.IntSize
 import androidx.compose.ui.unit.dp
 
-interface EdgeDetector {
-    /**
-     * Return the [Edge] associated to [position] inside a layout of size [layoutSize], given
-     * [density] and [orientation].
-     */
-    fun edge(
-        layoutSize: IntSize,
-        position: IntOffset,
-        density: Density,
-        orientation: Orientation,
-    ): Edge?
+/** The edge of a [SceneTransitionLayout]. */
+enum class Edge : SwipeSource {
+    Left,
+    Right,
+    Top,
+    Bottom,
 }
 
 val DefaultEdgeDetector = FixedSizeEdgeDetector(40.dp)
 
-/** An [EdgeDetector] that detects edges assuming a fixed edge size of [size]. */
-class FixedSizeEdgeDetector(val size: Dp) : EdgeDetector {
-    override fun edge(
+/** An [SwipeSourceDetector] that detects edges assuming a fixed edge size of [size]. */
+class FixedSizeEdgeDetector(val size: Dp) : SwipeSourceDetector {
+    override fun source(
         layoutSize: IntSize,
         position: IntOffset,
         density: Density,
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Key.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Key.kt
index 90f46bd..9d4b69c 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Key.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Key.kt
@@ -44,7 +44,7 @@
 class SceneKey(
     name: String,
     identity: Any = Object(),
-) : Key(name, identity) {
+) : Key(name, identity), UserActionResult {
     @VisibleForTesting
     // TODO(b/240432457): Make internal once PlatformComposeSceneTransitionLayoutTestsUtils can
     // access internal members.
@@ -53,6 +53,10 @@
     /** The unique [ElementKey] identifying this scene's root element. */
     val rootElementKey = ElementKey(name, identity)
 
+    // Implementation of [UserActionResult].
+    override val toScene: SceneKey = this
+    override val distance: UserActionDistance? = null
+
     override fun toString(): String {
         return "SceneKey(debugName=$debugName)"
     }
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/MultiPointerDraggable.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/MultiPointerDraggable.kt
index 3873878..8552aaf 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/MultiPointerDraggable.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/MultiPointerDraggable.kt
@@ -64,8 +64,8 @@
 @Stable
 internal fun Modifier.multiPointerDraggable(
     orientation: Orientation,
-    enabled: Boolean,
-    startDragImmediately: Boolean,
+    enabled: () -> Boolean,
+    startDragImmediately: () -> Boolean,
     onDragStarted: (startedPosition: Offset, overSlop: Float, pointersDown: Int) -> Unit,
     onDragDelta: (delta: Float) -> Unit,
     onDragStopped: (velocity: Float) -> Unit,
@@ -83,8 +83,8 @@
 
 private data class MultiPointerDraggableElement(
     private val orientation: Orientation,
-    private val enabled: Boolean,
-    private val startDragImmediately: Boolean,
+    private val enabled: () -> Boolean,
+    private val startDragImmediately: () -> Boolean,
     private val onDragStarted:
         (startedPosition: Offset, overSlop: Float, pointersDown: Int) -> Unit,
     private val onDragDelta: (Float) -> Unit,
@@ -110,10 +110,10 @@
     }
 }
 
-private class MultiPointerDraggableNode(
+internal class MultiPointerDraggableNode(
     orientation: Orientation,
-    enabled: Boolean,
-    var startDragImmediately: Boolean,
+    enabled: () -> Boolean,
+    var startDragImmediately: () -> Boolean,
     var onDragStarted: (startedPosition: Offset, overSlop: Float, pointersDown: Int) -> Unit,
     var onDragDelta: (Float) -> Unit,
     var onDragStopped: (velocity: Float) -> Unit,
@@ -122,7 +122,7 @@
     private val delegate = delegate(SuspendingPointerInputModifierNode(pointerInputHandler))
     private val velocityTracker = VelocityTracker()
 
-    var enabled: Boolean = enabled
+    var enabled: () -> Boolean = enabled
         set(value) {
             // Reset the pointer input whenever enabled changed.
             if (value != field) {
@@ -133,7 +133,7 @@
 
     var orientation: Orientation = orientation
         set(value) {
-            // Reset the pointer input whenever enabled orientation.
+            // Reset the pointer input whenever orientation changed.
             if (value != field) {
                 field = value
                 delegate.resetPointerInputHandler()
@@ -149,7 +149,7 @@
     ) = delegate.onPointerEvent(pointerEvent, pass, bounds)
 
     private suspend fun PointerInputScope.pointerInput() {
-        if (!enabled) {
+        if (!enabled()) {
             return
         }
 
@@ -163,8 +163,7 @@
         val onDragEnd: () -> Unit = {
             val maxFlingVelocity =
                 currentValueOf(LocalViewConfiguration).maximumFlingVelocity.let { max ->
-                    val maxF = max.toFloat()
-                    Velocity(maxF, maxF)
+                    Velocity(max, max)
                 }
 
             val velocity = velocityTracker.calculateVelocity(maxFlingVelocity)
@@ -183,7 +182,7 @@
 
         detectDragGestures(
             orientation = orientation,
-            startDragImmediately = { startDragImmediately },
+            startDragImmediately = startDragImmediately,
             onDragStart = onDragStart,
             onDragEnd = onDragEnd,
             onDragCancel = onDragCancel,
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Scene.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Scene.kt
index f67df54..af51cee 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Scene.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Scene.kt
@@ -38,7 +38,7 @@
     val key: SceneKey,
     layoutImpl: SceneTransitionLayoutImpl,
     content: @Composable SceneScope.() -> Unit,
-    actions: Map<UserAction, SceneKey>,
+    actions: Map<UserAction, UserActionResult>,
     zIndex: Float,
 ) {
     internal val scope = SceneScopeImpl(layoutImpl, this)
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneGestureHandler.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneGestureHandler.kt
index ff05478..aed04f6 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneGestureHandler.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneGestureHandler.kt
@@ -28,6 +28,8 @@
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.unit.Density
+import androidx.compose.ui.unit.IntSize
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.round
 import com.android.compose.nestedscroll.PriorityNestedScrollConnection
@@ -75,23 +77,25 @@
 
     internal var currentSource: Any? = null
 
-    /** The [UserAction]s associated to the current swipe. */
-    private var actionUpOrLeft: UserAction? = null
-    private var actionDownOrRight: UserAction? = null
-    private var actionUpOrLeftNoEdge: UserAction? = null
-    private var actionDownOrRightNoEdge: UserAction? = null
-    private var upOrLeftScene: SceneKey? = null
-    private var downOrRightScene: SceneKey? = null
+    /** The [Swipes] associated to the current gesture. */
+    private var swipes: Swipes? = null
+
+    /** The [UserActionResult] associated to up and down swipes. */
+    private var upOrLeftResult: UserActionResult? = null
+    private var downOrRightResult: UserActionResult? = null
 
     internal fun onDragStarted(pointersDown: Int, startedPosition: Offset?, overSlop: Float) {
         if (isDrivingTransition) {
             // This [transition] was already driving the animation: simply take over it.
             // Stop animating and start from where the current offset.
             swipeTransition.cancelOffsetAnimation()
-            updateTargetScenes(swipeTransition._fromScene)
+            updateSwipesResults(swipeTransition._fromScene)
             return
         }
 
+        check(overSlop != 0f) {
+            "onDragStarted() called while isDrivingTransition=false overSlop=0f"
+        }
         val transitionState = layoutState.transitionState
         if (transitionState is TransitionState.Transition) {
             // TODO(b/290184746): Better handle interruptions here if state != idle.
@@ -104,18 +108,25 @@
         }
 
         val fromScene = layoutImpl.scene(transitionState.currentScene)
-        setCurrentActions(fromScene, startedPosition, pointersDown)
+        updateSwipes(fromScene, startedPosition, pointersDown)
 
         val (targetScene, distance) =
-            findTargetSceneAndDistance(fromScene, overSlop, updateScenes = true) ?: return
-
+            findTargetSceneAndDistance(fromScene, overSlop, updateSwipesResults = true) ?: return
         updateTransition(SwipeTransition(fromScene, targetScene, distance), force = true)
     }
 
-    private fun setCurrentActions(fromScene: Scene, startedPosition: Offset?, pointersDown: Int) {
-        val fromEdge =
+    private fun updateSwipes(fromScene: Scene, startedPosition: Offset?, pointersDown: Int) {
+        this.swipes = computeSwipes(fromScene, startedPosition, pointersDown)
+    }
+
+    private fun computeSwipes(
+        fromScene: Scene,
+        startedPosition: Offset?,
+        pointersDown: Int
+    ): Swipes {
+        val fromSource =
             startedPosition?.let { position ->
-                layoutImpl.edgeDetector.edge(
+                layoutImpl.swipeSourceDetector.source(
                     fromScene.targetSize,
                     position.round(),
                     layoutImpl.density,
@@ -131,7 +142,7 @@
                         Orientation.Vertical -> SwipeDirection.Up
                     },
                 pointerCount = pointersDown,
-                fromEdge = fromEdge,
+                fromSource = fromSource,
             )
 
         val downOrRight =
@@ -142,33 +153,31 @@
                         Orientation.Vertical -> SwipeDirection.Down
                     },
                 pointerCount = pointersDown,
-                fromEdge = fromEdge,
+                fromSource = fromSource,
             )
 
-        if (fromEdge == null) {
-            actionUpOrLeft = null
-            actionDownOrRight = null
-            actionUpOrLeftNoEdge = upOrLeft
-            actionDownOrRightNoEdge = downOrRight
+        return if (fromSource == null) {
+            Swipes(
+                upOrLeft = null,
+                downOrRight = null,
+                upOrLeftNoSource = upOrLeft,
+                downOrRightNoSource = downOrRight,
+            )
         } else {
-            actionUpOrLeft = upOrLeft
-            actionDownOrRight = downOrRight
-            actionUpOrLeftNoEdge = upOrLeft.copy(fromEdge = null)
-            actionDownOrRightNoEdge = downOrRight.copy(fromEdge = null)
+            Swipes(
+                upOrLeft = upOrLeft,
+                downOrRight = downOrRight,
+                upOrLeftNoSource = upOrLeft.copy(fromSource = null),
+                downOrRightNoSource = downOrRight.copy(fromSource = null),
+            )
         }
     }
 
-    /**
-     * Use the layout size in the swipe orientation for swipe distance.
-     *
-     * TODO(b/290184746): Also handle custom distances for transitions. With smaller distances, we
-     *   will also have to make sure that we correctly handle overscroll.
-     */
-    private fun Scene.getAbsoluteDistance(): Float {
-        return when (orientation) {
-            Orientation.Horizontal -> targetSize.width
-            Orientation.Vertical -> targetSize.height
-        }.toFloat()
+    private fun Scene.getAbsoluteDistance(distance: UserActionDistance?): Float {
+        val targetSize = this.targetSize
+        return with(distance ?: DefaultSwipeDistance) {
+            layoutImpl.density.absoluteDistance(targetSize, orientation)
+        }
     }
 
     internal fun onDrag(delta: Float) {
@@ -183,7 +192,7 @@
             findTargetSceneAndDistance(
                 fromScene,
                 swipeTransition.dragOffset,
-                updateScenes = isNewFromScene,
+                updateSwipesResults = isNewFromScene,
             )
                 ?: run {
                     onDragStopped(delta, true)
@@ -200,9 +209,31 @@
         }
     }
 
-    private fun updateTargetScenes(fromScene: Scene) {
-        upOrLeftScene = fromScene.upOrLeft()
-        downOrRightScene = fromScene.downOrRight()
+    private fun updateSwipesResults(fromScene: Scene) {
+        val (upOrLeftResult, downOrRightResult) =
+            swipesResults(
+                fromScene,
+                this.swipes ?: error("updateSwipes() should be called before updateSwipesResults()")
+            )
+
+        this.upOrLeftResult = upOrLeftResult
+        this.downOrRightResult = downOrRightResult
+    }
+
+    private fun swipesResults(
+        fromScene: Scene,
+        swipes: Swipes
+    ): Pair<UserActionResult?, UserActionResult?> {
+        val userActions = fromScene.userActions
+        fun sceneToSwipePair(swipe: Swipe?): UserActionResult? {
+            return userActions[swipe ?: return null]
+        }
+
+        val upOrLeftResult =
+            sceneToSwipePair(swipes.upOrLeft) ?: sceneToSwipePair(swipes.upOrLeftNoSource)
+        val downOrRightResult =
+            sceneToSwipePair(swipes.downOrRight) ?: sceneToSwipePair(swipes.downOrRightNoSource)
+        return Pair(upOrLeftResult, downOrRightResult)
     }
 
     /**
@@ -229,9 +260,9 @@
         // If the offset is past the distance then let's change fromScene so that the user can swipe
         // to the next screen or go back to the previous one.
         val offset = swipeTransition.dragOffset
-        return if (offset <= -absoluteDistance && upOrLeftScene == toScene.key) {
+        return if (offset <= -absoluteDistance && upOrLeftResult?.toScene == toScene.key) {
             Pair(toScene, absoluteDistance)
-        } else if (offset >= absoluteDistance && downOrRightScene == toScene.key) {
+        } else if (offset >= absoluteDistance && downOrRightResult?.toScene == toScene.key) {
             Pair(toScene, -absoluteDistance)
         } else {
             Pair(fromScene, 0f)
@@ -244,31 +275,41 @@
      * @param fromScene the scene from which we look for the target
      * @param directionOffset signed float that indicates the direction. Positive is down or right
      *   negative is up or left.
-     * @param updateScenes whether the target scenes should be updated to the current values held in
-     *   the Scenes map. Usually we don't want to update them while doing a drag, because this could
-     *   change the target scene (jump cutting) to a different scene, when some system state changed
-     *   the targets the background. However, an update is needed any time we calculate the targets
-     *   for a new fromScene.
+     * @param updateSwipesResults whether the target scenes should be updated to the current values
+     *   held in the Scenes map. Usually we don't want to update them while doing a drag, because
+     *   this could change the target scene (jump cutting) to a different scene, when some system
+     *   state changed the targets the background. However, an update is needed any time we
+     *   calculate the targets for a new fromScene.
      * @return null when there are no targets in either direction. If one direction is null and you
      *   drag into the null direction this function will return the opposite direction, assuming
      *   that the users intention is to start the drag into the other direction eventually. If
      *   [directionOffset] is 0f and both direction are available, it will default to
-     *   [upOrLeftScene].
+     *   [upOrLeftResult].
      */
     private inline fun findTargetSceneAndDistance(
         fromScene: Scene,
         directionOffset: Float,
-        updateScenes: Boolean,
+        updateSwipesResults: Boolean,
     ): Pair<Scene, Float>? {
-        if (updateScenes) updateTargetScenes(fromScene)
-        val absoluteDistance = fromScene.getAbsoluteDistance()
+        if (updateSwipesResults) updateSwipesResults(fromScene)
 
         // Compute the target scene depending on the current offset.
         return when {
-            upOrLeftScene == null && downOrRightScene == null -> null
-            (directionOffset < 0f && upOrLeftScene != null) || downOrRightScene == null ->
-                Pair(layoutImpl.scene(upOrLeftScene!!), -absoluteDistance)
-            else -> Pair(layoutImpl.scene(downOrRightScene!!), absoluteDistance)
+            upOrLeftResult == null && downOrRightResult == null -> null
+            (directionOffset < 0f && upOrLeftResult != null) || downOrRightResult == null ->
+                upOrLeftResult?.let { result ->
+                    Pair(
+                        layoutImpl.scene(result.toScene),
+                        -fromScene.getAbsoluteDistance(result.distance)
+                    )
+                }
+            else ->
+                downOrRightResult?.let { result ->
+                    Pair(
+                        layoutImpl.scene(result.toScene),
+                        fromScene.getAbsoluteDistance(result.distance)
+                    )
+                }
         }
     }
 
@@ -280,24 +321,25 @@
         fromScene: Scene,
         directionOffset: Float,
     ): Pair<Scene, Float>? {
-        val absoluteDistance = fromScene.getAbsoluteDistance()
         return when {
             directionOffset > 0f ->
-                upOrLeftScene?.let { Pair(layoutImpl.scene(it), -absoluteDistance) }
+                upOrLeftResult?.let { result ->
+                    Pair(
+                        layoutImpl.scene(result.toScene),
+                        -fromScene.getAbsoluteDistance(result.distance),
+                    )
+                }
             directionOffset < 0f ->
-                downOrRightScene?.let { Pair(layoutImpl.scene(it), absoluteDistance) }
+                downOrRightResult?.let { result ->
+                    Pair(
+                        layoutImpl.scene(result.toScene),
+                        fromScene.getAbsoluteDistance(result.distance),
+                    )
+                }
             else -> null
         }
     }
 
-    private fun Scene.upOrLeft(): SceneKey? {
-        return userActions[actionUpOrLeft] ?: userActions[actionUpOrLeftNoEdge]
-    }
-
-    private fun Scene.downOrRight(): SceneKey? {
-        return userActions[actionDownOrRight] ?: userActions[actionDownOrRightNoEdge]
-    }
-
     internal fun onDragStopped(velocity: Float, canChangeScene: Boolean) {
         // The state was changed since the drag started; don't do anything.
         if (!isDrivingTransition) {
@@ -515,6 +557,26 @@
     companion object {
         private const val TAG = "SceneGestureHandler"
     }
+
+    private object DefaultSwipeDistance : UserActionDistance {
+        override fun Density.absoluteDistance(
+            fromSceneSize: IntSize,
+            orientation: Orientation,
+        ): Float {
+            return when (orientation) {
+                Orientation.Horizontal -> fromSceneSize.width
+                Orientation.Vertical -> fromSceneSize.height
+            }.toFloat()
+        }
+    }
+
+    /** The [Swipe] associated to a given fromScene, startedPosition and pointersDown. */
+    private class Swipes(
+        val upOrLeft: Swipe?,
+        val downOrRight: Swipe?,
+        val upOrLeftNoSource: Swipe?,
+        val downOrRightNoSource: Swipe?,
+    )
 }
 
 private class SceneDraggableHandler(
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt
index 80f8c1c..7e0aa9c3 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt
@@ -27,6 +27,10 @@
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
 import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.unit.Density
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.IntOffset
+import androidx.compose.ui.unit.IntSize
 
 /**
  * [SceneTransitionLayout] is a container that automatically animates its content whenever its state
@@ -38,7 +42,8 @@
  * UI code.
  *
  * @param state the state of this layout.
- * @param edgeDetector the edge detector used to detect which edge a swipe is started from, if any.
+ * @param swipeSourceDetector the edge detector used to detect which edge a swipe is started from,
+ *   if any.
  * @param transitionInterceptionThreshold used during a scene transition. For the scene to be
  *   intercepted, the progress value must be above the threshold, and below (1 - threshold).
  * @param scenes the configuration of the different scenes of this layout.
@@ -48,14 +53,14 @@
 fun SceneTransitionLayout(
     state: SceneTransitionLayoutState,
     modifier: Modifier = Modifier,
-    edgeDetector: EdgeDetector = DefaultEdgeDetector,
+    swipeSourceDetector: SwipeSourceDetector = DefaultEdgeDetector,
     @FloatRange(from = 0.0, to = 0.5) transitionInterceptionThreshold: Float = 0f,
     scenes: SceneTransitionLayoutScope.() -> Unit,
 ) {
     SceneTransitionLayoutForTesting(
         state,
         modifier,
-        edgeDetector,
+        swipeSourceDetector,
         transitionInterceptionThreshold,
         onLayoutImpl = null,
         scenes,
@@ -76,7 +81,8 @@
  *   This is called when the user commits a transition to a new scene because of a [UserAction], for
  *   instance by triggering back navigation or by swiping to a new scene.
  * @param transitions the definition of the transitions used to animate a change of scene.
- * @param edgeDetector the edge detector used to detect which edge a swipe is started from, if any.
+ * @param swipeSourceDetector the source detector used to detect which source a swipe is started
+ *   from, if any.
  * @param transitionInterceptionThreshold used during a scene transition. For the scene to be
  *   intercepted, the progress value must be above the threshold, and below (1 - threshold).
  * @param scenes the configuration of the different scenes of this layout.
@@ -87,7 +93,7 @@
     onChangeScene: (SceneKey) -> Unit,
     transitions: SceneTransitions,
     modifier: Modifier = Modifier,
-    edgeDetector: EdgeDetector = DefaultEdgeDetector,
+    swipeSourceDetector: SwipeSourceDetector = DefaultEdgeDetector,
     @FloatRange(from = 0.0, to = 0.5) transitionInterceptionThreshold: Float = 0f,
     scenes: SceneTransitionLayoutScope.() -> Unit,
 ) {
@@ -95,7 +101,7 @@
     SceneTransitionLayout(
         state,
         modifier,
-        edgeDetector,
+        swipeSourceDetector,
         transitionInterceptionThreshold,
         scenes,
     )
@@ -113,7 +119,7 @@
      */
     fun scene(
         key: SceneKey,
-        userActions: Map<UserAction, SceneKey> = emptyMap(),
+        userActions: Map<UserAction, UserActionResult> = emptyMap(),
         content: @Composable SceneScope.() -> Unit,
     )
 }
@@ -335,7 +341,7 @@
 data class Swipe(
     val direction: SwipeDirection,
     val pointerCount: Int = 1,
-    val fromEdge: Edge? = null,
+    val fromSource: SwipeSource? = null,
 ) : UserAction {
     companion object {
         val Left = Swipe(SwipeDirection.Left)
@@ -353,6 +359,95 @@
 }
 
 /**
+ * The source of a Swipe.
+ *
+ * Important: This can be anything that can be returned by any [SwipeSourceDetector], but this must
+ * implement [equals] and [hashCode]. Note that those can be trivially implemented using data
+ * classes.
+ */
+interface SwipeSource {
+    // Require equals() and hashCode() to be implemented.
+    override fun equals(other: Any?): Boolean
+
+    override fun hashCode(): Int
+}
+
+interface SwipeSourceDetector {
+    /**
+     * Return the [SwipeSource] associated to [position] inside a layout of size [layoutSize], given
+     * [density] and [orientation].
+     */
+    fun source(
+        layoutSize: IntSize,
+        position: IntOffset,
+        density: Density,
+        orientation: Orientation,
+    ): SwipeSource?
+}
+
+/**
+ * The result of performing a [UserAction].
+ *
+ * Note: [UserActionResult] is implemented by [SceneKey], and you can also use [withDistance] to
+ * easily create a [UserActionResult] with a fixed distance:
+ * ```
+ * SceneTransitionLayout(...) {
+ *     scene(
+ *         Scenes.Foo,
+ *         userActions =
+ *             mapOf(
+ *                 Swipe.Right to Scene.Bar,
+ *                 Swipe.Down to Scene.Doe withDistance 100.dp,
+ *             )
+ *         )
+ *     ) { ... }
+ * }
+ * ```
+ */
+interface UserActionResult {
+    /** The scene we should be transitioning to during the [UserAction]. */
+    val toScene: SceneKey
+
+    /**
+     * The distance the action takes to animate from 0% to 100%.
+     *
+     * If `null`, a default distance will be used that depends on the [UserAction] performed.
+     */
+    val distance: UserActionDistance?
+}
+
+interface UserActionDistance {
+    /**
+     * Return the **absolute** distance of the user action given the size of the scene we are
+     * animating from and the [orientation].
+     */
+    fun Density.absoluteDistance(fromSceneSize: IntSize, orientation: Orientation): Float
+}
+
+/**
+ * A utility function to make it possible to define user actions with a distance using the syntax
+ * `Swipe.Up to Scene.foo withDistance 100.dp`
+ */
+infix fun Pair<UserAction, SceneKey>.withDistance(
+    distance: Dp
+): Pair<UserAction, UserActionResult> {
+    val scene = second
+    val distance = FixedDistance(distance)
+    return first to
+        object : UserActionResult {
+            override val toScene: SceneKey = scene
+            override val distance: UserActionDistance = distance
+        }
+}
+
+/** The user action has a fixed [absoluteDistance]. */
+private class FixedDistance(private val distance: Dp) : UserActionDistance {
+    override fun Density.absoluteDistance(fromSceneSize: IntSize, orientation: Orientation): Float {
+        return distance.toPx()
+    }
+}
+
+/**
  * An internal version of [SceneTransitionLayout] to be used for tests.
  *
  * Important: You should use this only in tests and if you need to access the underlying
@@ -362,7 +457,7 @@
 internal fun SceneTransitionLayoutForTesting(
     state: SceneTransitionLayoutState,
     modifier: Modifier = Modifier,
-    edgeDetector: EdgeDetector = DefaultEdgeDetector,
+    swipeSourceDetector: SwipeSourceDetector = DefaultEdgeDetector,
     transitionInterceptionThreshold: Float = 0f,
     onLayoutImpl: ((SceneTransitionLayoutImpl) -> Unit)? = null,
     scenes: SceneTransitionLayoutScope.() -> Unit,
@@ -373,7 +468,7 @@
         SceneTransitionLayoutImpl(
                 state = state as BaseSceneTransitionLayoutState,
                 density = density,
-                edgeDetector = edgeDetector,
+                swipeSourceDetector = swipeSourceDetector,
                 transitionInterceptionThreshold = transitionInterceptionThreshold,
                 builder = scenes,
                 coroutineScope = coroutineScope,
@@ -394,7 +489,7 @@
         }
 
         layoutImpl.density = density
-        layoutImpl.edgeDetector = edgeDetector
+        layoutImpl.swipeSourceDetector = swipeSourceDetector
     }
 
     layoutImpl.Content(modifier)
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayoutImpl.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayoutImpl.kt
index 7cc9d26..8c5a472 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayoutImpl.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayoutImpl.kt
@@ -47,7 +47,7 @@
 internal class SceneTransitionLayoutImpl(
     internal val state: BaseSceneTransitionLayoutState,
     internal var density: Density,
-    internal var edgeDetector: EdgeDetector,
+    internal var swipeSourceDetector: SwipeSourceDetector,
     internal var transitionInterceptionThreshold: Float,
     builder: SceneTransitionLayoutScope.() -> Unit,
     private val coroutineScope: CoroutineScope,
@@ -140,7 +140,7 @@
         object : SceneTransitionLayoutScope {
                 override fun scene(
                     key: SceneKey,
-                    userActions: Map<UserAction, SceneKey>,
+                    userActions: Map<UserAction, UserActionResult>,
                     content: @Composable SceneScope.() -> Unit,
                 ) {
                     scenesToRemove.remove(key)
@@ -229,8 +229,10 @@
                 // Handle back events.
                 // TODO(b/290184746): Make sure that this works with SystemUI once we use
                 // SceneTransitionLayout in Flexiglass.
-                scene(state.transitionState.currentScene).userActions[Back]?.let { backScene ->
-                    BackHandler { with(state) { coroutineScope.onChangeScene(backScene) } }
+                scene(state.transitionState.currentScene).userActions[Back]?.let { result ->
+                    // TODO(b/290184746): Handle predictive back and use result.distance if
+                    // specified.
+                    BackHandler { with(state) { coroutineScope.onChangeScene(result.toScene) } }
                 }
 
                 Box {
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SwipeToScene.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SwipeToScene.kt
index 0d3bc7d..b9c4ac0 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SwipeToScene.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SwipeToScene.kt
@@ -17,40 +17,98 @@
 package com.android.compose.animation.scene
 
 import androidx.compose.foundation.gestures.Orientation
+import androidx.compose.runtime.Stable
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.input.pointer.PointerEvent
+import androidx.compose.ui.input.pointer.PointerEventPass
+import androidx.compose.ui.node.DelegatingNode
+import androidx.compose.ui.node.ModifierNodeElement
+import androidx.compose.ui.node.PointerInputModifierNode
+import androidx.compose.ui.unit.IntSize
 
 /**
  * Configures the swipeable behavior of a [SceneTransitionLayout] depending on the current state.
  */
+@Stable
 internal fun Modifier.swipeToScene(gestureHandler: SceneGestureHandler): Modifier {
-    /** Whether swipe should be enabled in the given [orientation]. */
-    fun Scene.shouldEnableSwipes(orientation: Orientation): Boolean =
-        userActions.keys.any { it is Swipe && it.direction.orientation == orientation }
+    return this.then(SwipeToSceneElement(gestureHandler))
+}
 
-    val layoutImpl = gestureHandler.layoutImpl
-    val currentScene = layoutImpl.scene(layoutImpl.state.transitionState.currentScene)
-    val orientation = gestureHandler.orientation
-    val canSwipe = currentScene.shouldEnableSwipes(orientation)
-    val canOppositeSwipe =
-        currentScene.shouldEnableSwipes(
-            when (orientation) {
+private data class SwipeToSceneElement(
+    val gestureHandler: SceneGestureHandler,
+) : ModifierNodeElement<SwipeToSceneNode>() {
+    override fun create(): SwipeToSceneNode = SwipeToSceneNode(gestureHandler)
+
+    override fun update(node: SwipeToSceneNode) {
+        node.gestureHandler = gestureHandler
+    }
+}
+
+private class SwipeToSceneNode(
+    gestureHandler: SceneGestureHandler,
+) : DelegatingNode(), PointerInputModifierNode {
+    private val delegate =
+        delegate(
+            MultiPointerDraggableNode(
+                orientation = gestureHandler.orientation,
+                enabled = ::enabled,
+                startDragImmediately = ::startDragImmediately,
+                onDragStarted = gestureHandler.draggable::onDragStarted,
+                onDragDelta = gestureHandler.draggable::onDelta,
+                onDragStopped = gestureHandler.draggable::onDragStopped,
+            )
+        )
+
+    var gestureHandler: SceneGestureHandler = gestureHandler
+        set(value) {
+            if (value != field) {
+                field = value
+
+                // Make sure to update the delegate orientation. Note that this will automatically
+                // reset the underlying pointer input handler, so previous gestures will be
+                // cancelled.
+                delegate.orientation = value.orientation
+            }
+        }
+
+    override fun onPointerEvent(
+        pointerEvent: PointerEvent,
+        pass: PointerEventPass,
+        bounds: IntSize,
+    ) = delegate.onPointerEvent(pointerEvent, pass, bounds)
+
+    override fun onCancelPointerInput() = delegate.onCancelPointerInput()
+
+    private fun enabled(): Boolean {
+        return gestureHandler.isDrivingTransition ||
+            currentScene().shouldEnableSwipes(gestureHandler.orientation)
+    }
+
+    private fun currentScene(): Scene {
+        val layoutImpl = gestureHandler.layoutImpl
+        return layoutImpl.scene(layoutImpl.state.transitionState.currentScene)
+    }
+
+    /** Whether swipe should be enabled in the given [orientation]. */
+    private fun Scene.shouldEnableSwipes(orientation: Orientation): Boolean {
+        return userActions.keys.any { it is Swipe && it.direction.orientation == orientation }
+    }
+
+    private fun startDragImmediately(): Boolean {
+        // Immediately start the drag if this our transition is currently animating to a scene
+        // (i.e. the user released their input pointer after swiping in this orientation) and the
+        // user can't swipe in the other direction.
+        return gestureHandler.isDrivingTransition &&
+            gestureHandler.swipeTransition.isAnimatingOffset &&
+            !canOppositeSwipe()
+    }
+
+    private fun canOppositeSwipe(): Boolean {
+        val oppositeOrientation =
+            when (gestureHandler.orientation) {
                 Orientation.Vertical -> Orientation.Horizontal
                 Orientation.Horizontal -> Orientation.Vertical
             }
-        )
-
-    return multiPointerDraggable(
-        orientation = orientation,
-        enabled = gestureHandler.isDrivingTransition || canSwipe,
-        // Immediately start the drag if this our [transition] is currently animating to a scene
-        // (i.e. the user released their input pointer after swiping in this orientation) and the
-        // user can't swipe in the other direction.
-        startDragImmediately =
-            gestureHandler.isDrivingTransition &&
-                gestureHandler.swipeTransition.isAnimatingOffset &&
-                !canOppositeSwipe,
-        onDragStarted = gestureHandler.draggable::onDragStarted,
-        onDragDelta = gestureHandler.draggable::onDelta,
-        onDragStopped = gestureHandler.draggable::onDragStopped,
-    )
+        return currentScene().shouldEnableSwipes(oppositeOrientation)
+    }
 }
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDsl.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDsl.kt
index dc8505c..a764a527 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDsl.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/TransitionDsl.kt
@@ -320,11 +320,3 @@
         anchorHeight: Boolean = true,
     )
 }
-
-/** The edge of a [SceneTransitionLayout]. */
-enum class Edge {
-    Left,
-    Right,
-    Top,
-    Bottom,
-}
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/nestedscroll/PriorityNestedScrollConnection.kt b/packages/SystemUI/compose/scene/src/com/android/compose/nestedscroll/PriorityNestedScrollConnection.kt
index 2841bcf..ac11d30 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/nestedscroll/PriorityNestedScrollConnection.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/nestedscroll/PriorityNestedScrollConnection.kt
@@ -22,6 +22,7 @@
 import androidx.compose.ui.input.nestedscroll.NestedScrollSource
 import androidx.compose.ui.unit.Velocity
 import com.android.compose.ui.util.SpaceVectorConverter
+import kotlin.math.sign
 
 /**
  * This [NestedScrollConnection] waits for a child to scroll ([onPreScroll] or [onPostScroll]), and
@@ -117,7 +118,12 @@
             return Velocity.Zero
         }
 
-        onPriorityStart(available = Offset.Zero)
+        // The offset passed to onPriorityStart() must be != 0f, so we create a small offset of 1px
+        // given the available velocity.
+        // TODO(b/291053278): Remove canStartPostFling() and instead make it possible to define the
+        // overscroll behavior on the Scene level.
+        val smallOffset = Offset(available.x.sign, available.y.sign)
+        onPriorityStart(available = smallOffset)
 
         // This is the last event of a scroll gesture.
         return onPriorityStop(available)
diff --git a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/FixedSizeEdgeDetectorTest.kt b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/FixedSizeEdgeDetectorTest.kt
index a68282a..cceaf57 100644
--- a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/FixedSizeEdgeDetectorTest.kt
+++ b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/FixedSizeEdgeDetectorTest.kt
@@ -35,7 +35,7 @@
     @Test
     fun horizontalEdges() {
         fun horizontalEdge(position: Int): Edge? =
-            detector.edge(
+            detector.source(
                 layoutSize,
                 position = IntOffset(position, 0),
                 density,
@@ -53,7 +53,7 @@
     @Test
     fun verticalEdges() {
         fun verticalEdge(position: Int): Edge? =
-            detector.edge(
+            detector.source(
                 layoutSize,
                 position = IntOffset(0, position),
                 density,
diff --git a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt
index 066a3e4..88363ad 100644
--- a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt
+++ b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt
@@ -77,7 +77,7 @@
                 userActions =
                     mapOf(
                         Swipe.Up to SceneB,
-                        Swipe(SwipeDirection.Up, fromEdge = Edge.Bottom) to SceneA
+                        Swipe(SwipeDirection.Up, fromSource = Edge.Bottom) to SceneA
                     ),
             ) {
                 Text("SceneC")
@@ -90,7 +90,7 @@
             SceneTransitionLayoutImpl(
                     state = layoutState,
                     density = Density(1f),
-                    edgeDetector = DefaultEdgeDetector,
+                    swipeSourceDetector = DefaultEdgeDetector,
                     transitionInterceptionThreshold = transitionInterceptionThreshold,
                     builder = scenesBuilder,
                     coroutineScope = coroutineScope,
@@ -192,16 +192,14 @@
 
     @Test
     fun onDragStarted_shouldStartATransition() = runGestureTest {
-        draggable.onDragStarted()
+        draggable.onDragStarted(overSlop = down(0.1f))
         assertTransition(currentScene = SceneA)
     }
 
     @Test
     fun afterSceneTransitionIsStarted_interceptDragEvents() = runGestureTest {
-        draggable.onDragStarted()
+        draggable.onDragStarted(overSlop = down(0.1f))
         assertTransition(currentScene = SceneA)
-
-        draggable.onDelta(pixels = down(0.1f))
         assertThat(progress).isEqualTo(0.1f)
 
         draggable.onDelta(pixels = down(0.1f))
@@ -210,10 +208,7 @@
 
     @Test
     fun onDragStoppedAfterDrag_velocityLowerThanThreshold_remainSameScene() = runGestureTest {
-        draggable.onDragStarted()
-        assertTransition(currentScene = SceneA)
-
-        draggable.onDelta(pixels = down(0.1f))
+        draggable.onDragStarted(overSlop = down(0.1f))
         assertTransition(currentScene = SceneA)
 
         draggable.onDragStopped(
@@ -228,10 +223,7 @@
 
     @Test
     fun onDragStoppedAfterDrag_velocityAtLeastThreshold_goToNextScene() = runGestureTest {
-        draggable.onDragStarted()
-        assertTransition(currentScene = SceneA)
-
-        draggable.onDelta(pixels = down(0.1f))
+        draggable.onDragStarted(overSlop = down(0.1f))
         assertTransition(currentScene = SceneA)
 
         draggable.onDragStopped(velocity = velocityThreshold)
@@ -245,7 +237,7 @@
 
     @Test
     fun onDragStoppedAfterStarted_returnToIdle() = runGestureTest {
-        draggable.onDragStarted()
+        draggable.onDragStarted(overSlop = down(0.1f))
         assertTransition(currentScene = SceneA)
 
         draggable.onDragStopped(velocity = 0f)
@@ -256,8 +248,7 @@
     @Test
     fun onDragReversedDirection_changeToScene() = runGestureTest {
         // Drag A -> B with progress 0.6
-        draggable.onDragStarted()
-        draggable.onDelta(up(0.6f))
+        draggable.onDragStarted(overSlop = up(0.6f))
         assertTransition(
             currentScene = SceneA,
             fromScene = SceneA,
@@ -366,8 +357,7 @@
     @Test
     fun onAccelaratedScroll_scrollToThirdScene() = runGestureTest {
         // Drag A -> B with progress 0.2
-        draggable.onDragStarted()
-        draggable.onDelta(up(0.2f))
+        draggable.onDragStarted(overSlop = up(0.2f))
         assertTransition(
             currentScene = SceneA,
             fromScene = SceneA,
@@ -401,9 +391,7 @@
 
     @Test
     fun onAccelaratedScrollBothTargetsBecomeNull_settlesToIdle() = runGestureTest {
-        draggable.onDragStarted()
-        draggable.onDelta(up(0.2f))
-
+        draggable.onDragStarted(overSlop = up(0.2f))
         draggable.onDelta(up(0.2f))
         draggable.onDragStopped(velocity = -velocityThreshold)
         assertTransition(currentScene = SceneB, fromScene = SceneA, toScene = SceneB)
@@ -459,16 +447,14 @@
         draggable.onDragStopped(down(0.1f))
 
         // now target changed to C for new drag that started before previous drag settled to Idle
-        draggable.onDragStarted(up(0.1f))
+        draggable.onDragStarted(overSlop = 0f)
+        draggable.onDelta(up(0.1f))
         assertTransition(fromScene = SceneA, toScene = SceneC, progress = 0.3f)
     }
 
     @Test
     fun startGestureDuringAnimatingOffset_shouldImmediatelyStopTheAnimation() = runGestureTest {
-        draggable.onDragStarted()
-        assertTransition(currentScene = SceneA)
-
-        draggable.onDelta(pixels = down(0.1f))
+        draggable.onDragStarted(overSlop = down(0.1f))
         assertTransition(currentScene = SceneA)
 
         draggable.onDragStopped(
@@ -759,10 +745,8 @@
     @Test
     fun startNestedScrollWhileDragging() = runGestureTest {
         val nestedScroll = nestedScrollConnection(nestedScrollBehavior = EdgeAlways)
-        draggable.onDragStarted()
+        draggable.onDragStarted(overSlop = down(0.1f))
         assertTransition(currentScene = SceneA)
-
-        draggable.onDelta(down(0.1f))
         assertThat(progress).isEqualTo(0.1f)
 
         // now we can intercept the scroll events
diff --git a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SwipeToSceneTest.kt b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SwipeToSceneTest.kt
index 1ec3c8b..9403358 100644
--- a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SwipeToSceneTest.kt
+++ b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SwipeToSceneTest.kt
@@ -17,6 +17,7 @@
 package com.android.compose.animation.scene
 
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.size
 import androidx.compose.runtime.Composable
@@ -89,8 +90,8 @@
                     mapOf(
                         Swipe.Down to TestScenes.SceneA,
                         Swipe(SwipeDirection.Down, pointerCount = 2) to TestScenes.SceneB,
-                        Swipe(SwipeDirection.Right, fromEdge = Edge.Left) to TestScenes.SceneB,
-                        Swipe(SwipeDirection.Down, fromEdge = Edge.Top) to TestScenes.SceneB,
+                        Swipe(SwipeDirection.Right, fromSource = Edge.Left) to TestScenes.SceneB,
+                        Swipe(SwipeDirection.Down, fromSource = Edge.Top) to TestScenes.SceneB,
                     ),
             ) {
                 Box(Modifier.fillMaxSize())
@@ -349,4 +350,46 @@
         assertThat(layoutState.transitionState).isInstanceOf(TransitionState.Idle::class.java)
         assertThat(layoutState.transitionState.currentScene).isEqualTo(TestScenes.SceneC)
     }
+
+    @Test
+    fun swipeDistance() {
+        // The draggable touch slop, i.e. the min px distance a touch pointer must move before it is
+        // detected as a drag event.
+        var touchSlop = 0f
+
+        val layoutState = MutableSceneTransitionLayoutState(TestScenes.SceneA)
+        val verticalSwipeDistance = 50.dp
+        assertThat(verticalSwipeDistance).isNotEqualTo(LayoutHeight)
+
+        rule.setContent {
+            touchSlop = LocalViewConfiguration.current.touchSlop
+
+            SceneTransitionLayout(
+                state = layoutState,
+                modifier = Modifier.size(LayoutWidth, LayoutHeight)
+            ) {
+                scene(
+                    TestScenes.SceneA,
+                    userActions =
+                        mapOf(Swipe.Down to TestScenes.SceneB withDistance verticalSwipeDistance),
+                ) {
+                    Spacer(Modifier.fillMaxSize())
+                }
+                scene(TestScenes.SceneB) { Spacer(Modifier.fillMaxSize()) }
+            }
+        }
+
+        assertThat(layoutState.currentTransition).isNull()
+
+        // Swipe by half of verticalSwipeDistance.
+        rule.onRoot().performTouchInput {
+            down(middleTop)
+            moveBy(Offset(0f, touchSlop + (verticalSwipeDistance / 2).toPx()), delayMillis = 1_000)
+        }
+
+        // We should be at 50%
+        val transition = layoutState.currentTransition
+        assertThat(transition).isNotNull()
+        assertThat(transition!!.progress).isEqualTo(0.5f)
+    }
 }