Merge "Refactor only: Move SceneGestureHandler in a separated file" into main

2 files changed, 659 insertions, 656 deletions

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
new file mode 100644
index 000000000000..7563e27d8e5d
--- /dev/null
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneGestureHandler.kt
@@ -0,0 +1,659 @@
+package com.android.compose.animation.scene
+
+import android.util.Log
+import androidx.annotation.VisibleForTesting
+import androidx.compose.animation.core.Animatable
+import androidx.compose.animation.core.Spring
+import androidx.compose.animation.core.spring
+import androidx.compose.foundation.gestures.Orientation
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableFloatStateOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.unit.Velocity
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.round
+import com.android.compose.nestedscroll.PriorityNestedScrollConnection
+import kotlin.math.absoluteValue
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.launch
+
+@VisibleForTesting
+class SceneGestureHandler(
+    private val layoutImpl: SceneTransitionLayoutImpl,
+    internal val orientation: Orientation,
+    private val coroutineScope: CoroutineScope,
+) : GestureHandler {
+    override val draggable: DraggableHandler = SceneDraggableHandler(this)
+
+    override val nestedScroll: SceneNestedScrollHandler = SceneNestedScrollHandler(this)
+
+    private var transitionState
+        get() = layoutImpl.state.transitionState
+        set(value) {
+            layoutImpl.state.transitionState = value
+        }
+
+    /**
+     * The transition controlled by this gesture handler. It will be set as the [transitionState] in
+     * the [SceneTransitionLayoutImpl] whenever this handler is driving the current transition.
+     *
+     * Note: the initialScene here does not matter, it's only used for initializing the transition
+     * and will be replaced when a drag event starts.
+     */
+    private val swipeTransition = SwipeTransition(initialScene = currentScene)
+
+    internal val currentScene: Scene
+        get() = layoutImpl.scene(transitionState.currentScene)
+
+    @VisibleForTesting
+    val isDrivingTransition
+        get() = transitionState == swipeTransition
+
+    @VisibleForTesting
+    var isAnimatingOffset
+        get() = swipeTransition.isAnimatingOffset
+        private set(value) {
+            swipeTransition.isAnimatingOffset = value
+        }
+
+    internal val swipeTransitionToScene
+        get() = swipeTransition._toScene
+
+    /**
+     * The velocity threshold at which the intent of the user is to swipe up or down. It is the same
+     * as SwipeableV2Defaults.VelocityThreshold.
+     */
+    @VisibleForTesting val velocityThreshold = with(layoutImpl.density) { 125.dp.toPx() }
+
+    /**
+     * The positional threshold at which the intent of the user is to swipe to the next scene. It is
+     * the same as SwipeableV2Defaults.PositionalThreshold.
+     */
+    private val positionalThreshold = with(layoutImpl.density) { 56.dp.toPx() }
+
+    internal var gestureWithPriority: Any? = null
+
+    internal fun onDragStarted(pointersDown: Int, startedPosition: Offset?) {
+        if (isDrivingTransition) {
+            // This [transition] was already driving the animation: simply take over it.
+            // Stop animating and start from where the current offset.
+            swipeTransition.stopOffsetAnimation()
+            return
+        }
+
+        val transition = transitionState
+        if (transition is TransitionState.Transition) {
+            // TODO(b/290184746): Better handle interruptions here if state != idle.
+            Log.w(
+                TAG,
+                "start from TransitionState.Transition is not fully supported: from" +
+                    " ${transition.fromScene} to ${transition.toScene} " +
+                    "(progress ${transition.progress})"
+            )
+        }
+
+        val fromScene = currentScene
+
+        swipeTransition._currentScene = fromScene
+        swipeTransition._fromScene = fromScene
+
+        // We don't know where we are transitioning to yet given that the drag just started, so set
+        // it to fromScene, which will effectively be treated the same as Idle(fromScene).
+        swipeTransition._toScene = fromScene
+
+        swipeTransition.stopOffsetAnimation()
+        swipeTransition.dragOffset = 0f
+
+        // 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.
+        swipeTransition.absoluteDistance =
+            when (orientation) {
+                Orientation.Horizontal -> layoutImpl.size.width
+                Orientation.Vertical -> layoutImpl.size.height
+            }.toFloat()
+
+        val fromEdge =
+            startedPosition?.let { position ->
+                layoutImpl.edgeDetector.edge(
+                    layoutImpl.size,
+                    position.round(),
+                    layoutImpl.density,
+                    orientation,
+                )
+            }
+
+        swipeTransition.actionUpOrLeft =
+            Swipe(
+                direction =
+                    when (orientation) {
+                        Orientation.Horizontal -> SwipeDirection.Left
+                        Orientation.Vertical -> SwipeDirection.Up
+                    },
+                pointerCount = pointersDown,
+                fromEdge = fromEdge,
+            )
+
+        swipeTransition.actionDownOrRight =
+            Swipe(
+                direction =
+                    when (orientation) {
+                        Orientation.Horizontal -> SwipeDirection.Right
+                        Orientation.Vertical -> SwipeDirection.Down
+                    },
+                pointerCount = pointersDown,
+                fromEdge = fromEdge,
+            )
+
+        if (fromEdge == null) {
+            swipeTransition.actionUpOrLeftNoEdge = null
+            swipeTransition.actionDownOrRightNoEdge = null
+        } else {
+            swipeTransition.actionUpOrLeftNoEdge =
+                (swipeTransition.actionUpOrLeft as Swipe).copy(fromEdge = null)
+            swipeTransition.actionDownOrRightNoEdge =
+                (swipeTransition.actionDownOrRight as Swipe).copy(fromEdge = null)
+        }
+
+        if (swipeTransition.absoluteDistance > 0f) {
+            transitionState = swipeTransition
+        }
+    }
+
+    internal fun onDrag(delta: Float) {
+        if (delta == 0f) return
+
+        swipeTransition.dragOffset += delta
+
+        // First check transition.fromScene should be changed for the case where the user quickly
+        // swiped twice in a row to accelerate the transition and go from A => B then B => C really
+        // fast.
+        maybeHandleAcceleratedSwipe()
+
+        val offset = swipeTransition.dragOffset
+        val fromScene = swipeTransition._fromScene
+
+        // Compute the target scene depending on the current offset.
+        val target = fromScene.findTargetSceneAndDistance(offset)
+
+        if (swipeTransition._toScene.key != target.sceneKey) {
+            swipeTransition._toScene = layoutImpl.scenes.getValue(target.sceneKey)
+        }
+
+        if (swipeTransition._distance != target.distance) {
+            swipeTransition._distance = target.distance
+        }
+    }
+
+    /**
+     * Change fromScene in the case where the user quickly swiped multiple times in the same
+     * direction to accelerate the transition from A => B then B => C.
+     */
+    private fun maybeHandleAcceleratedSwipe() {
+        val toScene = swipeTransition._toScene
+        val fromScene = swipeTransition._fromScene
+
+        // If the swipe was not committed, don't do anything.
+        if (fromScene == toScene || swipeTransition._currentScene != toScene) {
+            return
+        }
+
+        // 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
+        val absoluteDistance = swipeTransition.absoluteDistance
+        if (offset <= -absoluteDistance && swipeTransition.upOrLeft(fromScene) == toScene.key) {
+            swipeTransition.dragOffset += absoluteDistance
+            swipeTransition._fromScene = toScene
+        } else if (
+            offset >= absoluteDistance && swipeTransition.downOrRight(fromScene) == toScene.key
+        ) {
+            swipeTransition.dragOffset -= absoluteDistance
+            swipeTransition._fromScene = toScene
+        }
+
+        // Important note: toScene and distance will be updated right after this function is called,
+        // using fromScene and dragOffset.
+    }
+
+    private class TargetScene(
+        val sceneKey: SceneKey,
+        val distance: Float,
+    )
+
+    private fun Scene.findTargetSceneAndDistance(directionOffset: Float): TargetScene {
+        val upOrLeft = swipeTransition.upOrLeft(this)
+        val downOrRight = swipeTransition.downOrRight(this)
+
+        // Compute the target scene depending on the current offset.
+        return when {
+            directionOffset < 0f && upOrLeft != null -> {
+                TargetScene(
+                    sceneKey = upOrLeft,
+                    distance = -swipeTransition.absoluteDistance,
+                )
+            }
+            directionOffset > 0f && downOrRight != null -> {
+                TargetScene(
+                    sceneKey = downOrRight,
+                    distance = swipeTransition.absoluteDistance,
+                )
+            }
+            else -> {
+                TargetScene(
+                    sceneKey = key,
+                    distance = 0f,
+                )
+            }
+        }
+    }
+
+    internal fun onDragStopped(velocity: Float, canChangeScene: Boolean) {
+        // The state was changed since the drag started; don't do anything.
+        if (!isDrivingTransition) {
+            return
+        }
+
+        fun animateTo(targetScene: Scene, targetOffset: Float) {
+            // If the effective current scene changed, it should be reflected right now in the
+            // current scene state, even before the settle animation is ongoing. That way all the
+            // swipeables and back handlers will be refreshed and the user can for instance quickly
+            // swipe vertically from A => B then horizontally from B => C, or swipe from A => B then
+            // immediately go back B => A.
+            if (targetScene != swipeTransition._currentScene) {
+                swipeTransition._currentScene = targetScene
+                layoutImpl.onChangeScene(targetScene.key)
+            }
+
+            animateOffset(
+                initialVelocity = velocity,
+                targetOffset = targetOffset,
+                targetScene = targetScene.key
+            )
+        }
+
+        val fromScene = swipeTransition._fromScene
+        if (canChangeScene) {
+            // If we are halfway between two scenes, we check what the target will be based on the
+            // velocity and offset of the transition, then we launch the animation.
+
+            val toScene = swipeTransition._toScene
+            if (fromScene == toScene) {
+                // We were not animating.
+                transitionState = TransitionState.Idle(fromScene.key)
+                return
+            }
+
+            // Compute the destination scene (and therefore offset) to settle in.
+            val offset = swipeTransition.dragOffset
+            val distance = swipeTransition.distance
+            if (
+                shouldCommitSwipe(
+                    offset,
+                    distance,
+                    velocity,
+                    wasCommitted = swipeTransition._currentScene == toScene,
+                )
+            ) {
+                // Animate to the next scene
+                animateTo(targetScene = toScene, targetOffset = distance)
+            } else {
+                // Animate to the initial scene
+                animateTo(targetScene = fromScene, targetOffset = 0f)
+            }
+        } else {
+            // We are doing an overscroll animation between scenes. In this case, we can also start
+            // from the idle position.
+
+            val startFromIdlePosition = swipeTransition.dragOffset == 0f
+
+            if (startFromIdlePosition) {
+                // If there is a next scene, we start the overscroll animation.
+                val target = fromScene.findTargetSceneAndDistance(velocity)
+                val isValidTarget = target.distance != 0f && target.sceneKey != fromScene.key
+                if (isValidTarget) {
+                    swipeTransition._toScene = layoutImpl.scene(target.sceneKey)
+                    swipeTransition._distance = target.distance
+
+                    animateTo(targetScene = fromScene, targetOffset = 0f)
+                } else {
+                    // We will not animate
+                    transitionState = TransitionState.Idle(fromScene.key)
+                }
+            } else {
+                // We were between two scenes: animate to the initial scene.
+                animateTo(targetScene = fromScene, targetOffset = 0f)
+            }
+        }
+    }
+
+    /**
+     * Whether the swipe to the target scene should be committed or not. This is inspired by
+     * SwipeableV2.computeTarget().
+     */
+    private fun shouldCommitSwipe(
+        offset: Float,
+        distance: Float,
+        velocity: Float,
+        wasCommitted: Boolean,
+    ): Boolean {
+        fun isCloserToTarget(): Boolean {
+            return (offset - distance).absoluteValue < offset.absoluteValue
+        }
+
+        // Swiping up or left.
+        if (distance < 0f) {
+            return if (offset > 0f || velocity >= velocityThreshold) {
+                false
+            } else {
+                velocity <= -velocityThreshold ||
+                    (offset <= -positionalThreshold && !wasCommitted) ||
+                    isCloserToTarget()
+            }
+        }
+
+        // Swiping down or right.
+        return if (offset < 0f || velocity <= -velocityThreshold) {
+            false
+        } else {
+            velocity >= velocityThreshold ||
+                (offset >= positionalThreshold && !wasCommitted) ||
+                isCloserToTarget()
+        }
+    }
+
+    private fun animateOffset(
+        initialVelocity: Float,
+        targetOffset: Float,
+        targetScene: SceneKey,
+    ) {
+        swipeTransition.startOffsetAnimation {
+            coroutineScope.launch {
+                if (!isAnimatingOffset) {
+                    swipeTransition.offsetAnimatable.snapTo(swipeTransition.dragOffset)
+                }
+                isAnimatingOffset = true
+
+                swipeTransition.offsetAnimatable.animateTo(
+                    targetOffset,
+                    // TODO(b/290184746): Make this spring spec configurable.
+                    spring(
+                        stiffness = Spring.StiffnessMediumLow,
+                        visibilityThreshold = OffsetVisibilityThreshold
+                    ),
+                    initialVelocity = initialVelocity,
+                )
+
+                isAnimatingOffset = false
+
+                // Now that the animation is done, the state should be idle. Note that if the state
+                // was changed since this animation started, some external code changed it and we
+                // shouldn't do anything here. Note also that this job will be cancelled in the case
+                // where the user intercepts this swipe.
+                if (isDrivingTransition) {
+                    transitionState = TransitionState.Idle(targetScene)
+                }
+            }
+        }
+    }
+
+    private class SwipeTransition(initialScene: Scene) : TransitionState.Transition {
+        var _currentScene by mutableStateOf(initialScene)
+        override val currentScene: SceneKey
+            get() = _currentScene.key
+
+        var _fromScene by mutableStateOf(initialScene)
+        override val fromScene: SceneKey
+            get() = _fromScene.key
+
+        var _toScene by mutableStateOf(initialScene)
+        override val toScene: SceneKey
+            get() = _toScene.key
+
+        override val progress: Float
+            get() {
+                val offset = if (isAnimatingOffset) offsetAnimatable.value else dragOffset
+                if (distance == 0f) {
+                    // This can happen only if fromScene == toScene.
+                    error(
+                        "Transition.progress should be called only when Transition.fromScene != " +
+                            "Transition.toScene"
+                    )
+                }
+                return offset / distance
+            }
+
+        override val isInitiatedByUserInput = true
+
+        /** The current offset caused by the drag gesture. */
+        var dragOffset by mutableFloatStateOf(0f)
+
+        /**
+         * Whether the offset is animated (the user lifted their finger) or if it is driven by
+         * gesture.
+         */
+        var isAnimatingOffset by mutableStateOf(false)
+
+        // If we are not animating offset, it means the offset is being driven by the user's finger.
+        override val isUserInputOngoing: Boolean
+            get() = !isAnimatingOffset
+
+        /** The animatable used to animate the offset once the user lifted its finger. */
+        val offsetAnimatable = Animatable(0f, OffsetVisibilityThreshold)
+
+        /** Job to check that there is at most one offset animation in progress. */
+        private var offsetAnimationJob: Job? = null
+
+        /** Ends any previous [offsetAnimationJob] and runs the new [job]. */
+        fun startOffsetAnimation(job: () -> Job) {
+            stopOffsetAnimation()
+            offsetAnimationJob = job()
+        }
+
+        /** Stops any ongoing offset animation. */
+        fun stopOffsetAnimation() {
+            offsetAnimationJob?.cancel()
+
+            if (isAnimatingOffset) {
+                isAnimatingOffset = false
+                dragOffset = offsetAnimatable.value
+            }
+        }
+
+        /** The absolute distance between [fromScene] and [toScene]. */
+        var absoluteDistance = 0f
+
+        /**
+         * The signed distance between [fromScene] and [toScene]. It is negative if [fromScene] is
+         * above or to the left of [toScene].
+         */
+        var _distance by mutableFloatStateOf(0f)
+        val distance: Float
+            get() = _distance
+
+        /** The [UserAction]s associated to this swipe. */
+        var actionUpOrLeft: UserAction = Back
+        var actionDownOrRight: UserAction = Back
+        var actionUpOrLeftNoEdge: UserAction? = null
+        var actionDownOrRightNoEdge: UserAction? = null
+
+        fun upOrLeft(scene: Scene): SceneKey? {
+            return scene.userActions[actionUpOrLeft]
+                ?: actionUpOrLeftNoEdge?.let { scene.userActions[it] }
+        }
+
+        fun downOrRight(scene: Scene): SceneKey? {
+            return scene.userActions[actionDownOrRight]
+                ?: actionDownOrRightNoEdge?.let { scene.userActions[it] }
+        }
+    }
+
+    companion object {
+        private const val TAG = "SceneGestureHandler"
+    }
+}
+
+private class SceneDraggableHandler(
+    private val gestureHandler: SceneGestureHandler,
+) : DraggableHandler {
+    override fun onDragStarted(startedPosition: Offset, pointersDown: Int) {
+        gestureHandler.gestureWithPriority = this
+        gestureHandler.onDragStarted(pointersDown, startedPosition)
+    }
+
+    override fun onDelta(pixels: Float) {
+        if (gestureHandler.gestureWithPriority == this) {
+            gestureHandler.onDrag(delta = pixels)
+        }
+    }
+
+    override fun onDragStopped(velocity: Float) {
+        if (gestureHandler.gestureWithPriority == this) {
+            gestureHandler.gestureWithPriority = null
+            gestureHandler.onDragStopped(velocity = velocity, canChangeScene = true)
+        }
+    }
+}
+
+@VisibleForTesting
+class SceneNestedScrollHandler(
+    private val gestureHandler: SceneGestureHandler,
+) : NestedScrollHandler {
+    override val connection: PriorityNestedScrollConnection = nestedScrollConnection()
+
+    private fun Offset.toAmount() =
+        when (gestureHandler.orientation) {
+            Orientation.Horizontal -> x
+            Orientation.Vertical -> y
+        }
+
+    private fun Velocity.toAmount() =
+        when (gestureHandler.orientation) {
+            Orientation.Horizontal -> x
+            Orientation.Vertical -> y
+        }
+
+    private fun Float.toOffset() =
+        when (gestureHandler.orientation) {
+            Orientation.Horizontal -> Offset(x = this, y = 0f)
+            Orientation.Vertical -> Offset(x = 0f, y = this)
+        }
+
+    private fun nestedScrollConnection(): PriorityNestedScrollConnection {
+        // The next potential scene is calculated during the canStart
+        var nextScene: SceneKey? = null
+
+        // This is the scene on which we will have priority during the scroll gesture.
+        var priorityScene: SceneKey? = null
+
+        // If we performed a long gesture before entering priority mode, we would have to avoid
+        // moving on to the next scene.
+        var gestureStartedOnNestedChild = false
+
+        val actionUpOrLeft =
+            Swipe(
+                direction =
+                    when (gestureHandler.orientation) {
+                        Orientation.Horizontal -> SwipeDirection.Left
+                        Orientation.Vertical -> SwipeDirection.Up
+                    },
+                pointerCount = 1,
+            )
+
+        val actionDownOrRight =
+            Swipe(
+                direction =
+                    when (gestureHandler.orientation) {
+                        Orientation.Horizontal -> SwipeDirection.Right
+                        Orientation.Vertical -> SwipeDirection.Down
+                    },
+                pointerCount = 1,
+            )
+
+        fun findNextScene(amount: Float): SceneKey? {
+            val fromScene = gestureHandler.currentScene
+            return when {
+                amount < 0f -> fromScene.userActions[actionUpOrLeft]
+                amount > 0f -> fromScene.userActions[actionDownOrRight]
+                else -> null
+            }
+        }
+
+        return PriorityNestedScrollConnection(
+            canStartPreScroll = { offsetAvailable, offsetBeforeStart ->
+                gestureStartedOnNestedChild = offsetBeforeStart != Offset.Zero
+
+                val canInterceptPreScroll =
+                    gestureHandler.isDrivingTransition &&
+                        !gestureStartedOnNestedChild &&
+                        offsetAvailable.toAmount() != 0f
+
+                if (!canInterceptPreScroll) return@PriorityNestedScrollConnection false
+
+                nextScene = gestureHandler.swipeTransitionToScene.key
+
+                true
+            },
+            canStartPostScroll = { offsetAvailable, offsetBeforeStart ->
+                val amount = offsetAvailable.toAmount()
+                if (amount == 0f) return@PriorityNestedScrollConnection false
+
+                gestureStartedOnNestedChild = offsetBeforeStart != Offset.Zero
+                nextScene = findNextScene(amount)
+                nextScene != null
+            },
+            canStartPostFling = { velocityAvailable ->
+                val amount = velocityAvailable.toAmount()
+                if (amount == 0f) return@PriorityNestedScrollConnection false
+
+                // We could start an overscroll animation
+                gestureStartedOnNestedChild = true
+                nextScene = findNextScene(amount)
+                nextScene != null
+            },
+            canContinueScroll = { priorityScene == gestureHandler.swipeTransitionToScene.key },
+            onStart = {
+                gestureHandler.gestureWithPriority = this
+                priorityScene = nextScene
+                gestureHandler.onDragStarted(pointersDown = 1, startedPosition = null)
+            },
+            onScroll = { offsetAvailable ->
+                if (gestureHandler.gestureWithPriority != this) {
+                    return@PriorityNestedScrollConnection Offset.Zero
+                }
+
+                val amount = offsetAvailable.toAmount()
+
+                // TODO(b/297842071) We should handle the overscroll or slow drag if the gesture is
+                // initiated in a nested child.
+                gestureHandler.onDrag(amount)
+
+                amount.toOffset()
+            },
+            onStop = { velocityAvailable ->
+                if (gestureHandler.gestureWithPriority != this) {
+                    return@PriorityNestedScrollConnection Velocity.Zero
+                }
+
+                priorityScene = null
+
+                gestureHandler.onDragStopped(
+                    velocity = velocityAvailable.toAmount(),
+                    canChangeScene = !gestureStartedOnNestedChild
+                )
+
+                // The onDragStopped animation consumes any remaining velocity.
+                velocityAvailable
+            },
+        )
+    }
+}
+
+/**
+ * The number of pixels below which there won't be a visible difference in the transition and from
+ * which the animation can stop.
+ */
+private const val OffsetVisibilityThreshold = 0.5f
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 877ac095af4e..309213a341cc 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
@@ -16,31 +16,13 @@
 
 package com.android.compose.animation.scene
 
-import android.util.Log
-import androidx.annotation.VisibleForTesting
-import androidx.compose.animation.core.Animatable
-import androidx.compose.animation.core.Spring
-import androidx.compose.animation.core.spring
 import androidx.compose.foundation.gestures.Orientation
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
-import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableFloatStateOf
-import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
-import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.input.nestedscroll.nestedScroll
-import androidx.compose.ui.unit.Velocity
-import androidx.compose.ui.unit.dp
-import androidx.compose.ui.unit.round
-import com.android.compose.nestedscroll.PriorityNestedScrollConnection
-import kotlin.math.absoluteValue
-import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.Job
-import kotlinx.coroutines.launch
 
 /**
  * Configures the swipeable behavior of a [SceneTransitionLayout] depending on the current state.
@@ -101,641 +83,3 @@ private fun rememberSceneGestureHandler(
 
     return gestureHandler
 }
-
-@VisibleForTesting
-class SceneGestureHandler(
-    private val layoutImpl: SceneTransitionLayoutImpl,
-    internal val orientation: Orientation,
-    private val coroutineScope: CoroutineScope,
-) : GestureHandler {
-    override val draggable: DraggableHandler = SceneDraggableHandler(this)
-
-    override val nestedScroll: SceneNestedScrollHandler = SceneNestedScrollHandler(this)
-
-    private var transitionState
-        get() = layoutImpl.state.transitionState
-        set(value) {
-            layoutImpl.state.transitionState = value
-        }
-
-    /**
-     * The transition controlled by this gesture handler. It will be set as the [transitionState] in
-     * the [SceneTransitionLayoutImpl] whenever this handler is driving the current transition.
-     *
-     * Note: the initialScene here does not matter, it's only used for initializing the transition
-     * and will be replaced when a drag event starts.
-     */
-    private val swipeTransition = SwipeTransition(initialScene = currentScene)
-
-    internal val currentScene: Scene
-        get() = layoutImpl.scene(transitionState.currentScene)
-
-    @VisibleForTesting
-    val isDrivingTransition
-        get() = transitionState == swipeTransition
-
-    @VisibleForTesting
-    var isAnimatingOffset
-        get() = swipeTransition.isAnimatingOffset
-        private set(value) {
-            swipeTransition.isAnimatingOffset = value
-        }
-
-    internal val swipeTransitionToScene
-        get() = swipeTransition._toScene
-
-    /**
-     * The velocity threshold at which the intent of the user is to swipe up or down. It is the same
-     * as SwipeableV2Defaults.VelocityThreshold.
-     */
-    @VisibleForTesting val velocityThreshold = with(layoutImpl.density) { 125.dp.toPx() }
-
-    /**
-     * The positional threshold at which the intent of the user is to swipe to the next scene. It is
-     * the same as SwipeableV2Defaults.PositionalThreshold.
-     */
-    private val positionalThreshold = with(layoutImpl.density) { 56.dp.toPx() }
-
-    internal var gestureWithPriority: Any? = null
-
-    internal fun onDragStarted(pointersDown: Int, startedPosition: Offset?) {
-        if (isDrivingTransition) {
-            // This [transition] was already driving the animation: simply take over it.
-            // Stop animating and start from where the current offset.
-            swipeTransition.stopOffsetAnimation()
-            return
-        }
-
-        val transition = transitionState
-        if (transition is TransitionState.Transition) {
-            // TODO(b/290184746): Better handle interruptions here if state != idle.
-            Log.w(
-                TAG,
-                "start from TransitionState.Transition is not fully supported: from" +
-                    " ${transition.fromScene} to ${transition.toScene} " +
-                    "(progress ${transition.progress})"
-            )
-        }
-
-        val fromScene = currentScene
-
-        swipeTransition._currentScene = fromScene
-        swipeTransition._fromScene = fromScene
-
-        // We don't know where we are transitioning to yet given that the drag just started, so set
-        // it to fromScene, which will effectively be treated the same as Idle(fromScene).
-        swipeTransition._toScene = fromScene
-
-        swipeTransition.stopOffsetAnimation()
-        swipeTransition.dragOffset = 0f
-
-        // 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.
-        swipeTransition.absoluteDistance =
-            when (orientation) {
-                Orientation.Horizontal -> layoutImpl.size.width
-                Orientation.Vertical -> layoutImpl.size.height
-            }.toFloat()
-
-        val fromEdge =
-            startedPosition?.let { position ->
-                layoutImpl.edgeDetector.edge(
-                    layoutImpl.size,
-                    position.round(),
-                    layoutImpl.density,
-                    orientation,
-                )
-            }
-
-        swipeTransition.actionUpOrLeft =
-            Swipe(
-                direction =
-                    when (orientation) {
-                        Orientation.Horizontal -> SwipeDirection.Left
-                        Orientation.Vertical -> SwipeDirection.Up
-                    },
-                pointerCount = pointersDown,
-                fromEdge = fromEdge,
-            )
-
-        swipeTransition.actionDownOrRight =
-            Swipe(
-                direction =
-                    when (orientation) {
-                        Orientation.Horizontal -> SwipeDirection.Right
-                        Orientation.Vertical -> SwipeDirection.Down
-                    },
-                pointerCount = pointersDown,
-                fromEdge = fromEdge,
-            )
-
-        if (fromEdge == null) {
-            swipeTransition.actionUpOrLeftNoEdge = null
-            swipeTransition.actionDownOrRightNoEdge = null
-        } else {
-            swipeTransition.actionUpOrLeftNoEdge =
-                (swipeTransition.actionUpOrLeft as Swipe).copy(fromEdge = null)
-            swipeTransition.actionDownOrRightNoEdge =
-                (swipeTransition.actionDownOrRight as Swipe).copy(fromEdge = null)
-        }
-
-        if (swipeTransition.absoluteDistance > 0f) {
-            transitionState = swipeTransition
-        }
-    }
-
-    internal fun onDrag(delta: Float) {
-        if (delta == 0f) return
-
-        swipeTransition.dragOffset += delta
-
-        // First check transition.fromScene should be changed for the case where the user quickly
-        // swiped twice in a row to accelerate the transition and go from A => B then B => C really
-        // fast.
-        maybeHandleAcceleratedSwipe()
-
-        val offset = swipeTransition.dragOffset
-        val fromScene = swipeTransition._fromScene
-
-        // Compute the target scene depending on the current offset.
-        val target = fromScene.findTargetSceneAndDistance(offset)
-
-        if (swipeTransition._toScene.key != target.sceneKey) {
-            swipeTransition._toScene = layoutImpl.scenes.getValue(target.sceneKey)
-        }
-
-        if (swipeTransition._distance != target.distance) {
-            swipeTransition._distance = target.distance
-        }
-    }
-
-    /**
-     * Change fromScene in the case where the user quickly swiped multiple times in the same
-     * direction to accelerate the transition from A => B then B => C.
-     */
-    private fun maybeHandleAcceleratedSwipe() {
-        val toScene = swipeTransition._toScene
-        val fromScene = swipeTransition._fromScene
-
-        // If the swipe was not committed, don't do anything.
-        if (fromScene == toScene || swipeTransition._currentScene != toScene) {
-            return
-        }
-
-        // 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
-        val absoluteDistance = swipeTransition.absoluteDistance
-        if (offset <= -absoluteDistance && swipeTransition.upOrLeft(fromScene) == toScene.key) {
-            swipeTransition.dragOffset += absoluteDistance
-            swipeTransition._fromScene = toScene
-        } else if (
-            offset >= absoluteDistance && swipeTransition.downOrRight(fromScene) == toScene.key
-        ) {
-            swipeTransition.dragOffset -= absoluteDistance
-            swipeTransition._fromScene = toScene
-        }
-
-        // Important note: toScene and distance will be updated right after this function is called,
-        // using fromScene and dragOffset.
-    }
-
-    private class TargetScene(
-        val sceneKey: SceneKey,
-        val distance: Float,
-    )
-
-    private fun Scene.findTargetSceneAndDistance(directionOffset: Float): TargetScene {
-        val upOrLeft = swipeTransition.upOrLeft(this)
-        val downOrRight = swipeTransition.downOrRight(this)
-
-        // Compute the target scene depending on the current offset.
-        return when {
-            directionOffset < 0f && upOrLeft != null -> {
-                TargetScene(
-                    sceneKey = upOrLeft,
-                    distance = -swipeTransition.absoluteDistance,
-                )
-            }
-            directionOffset > 0f && downOrRight != null -> {
-                TargetScene(
-                    sceneKey = downOrRight,
-                    distance = swipeTransition.absoluteDistance,
-                )
-            }
-            else -> {
-                TargetScene(
-                    sceneKey = key,
-                    distance = 0f,
-                )
-            }
-        }
-    }
-
-    internal fun onDragStopped(velocity: Float, canChangeScene: Boolean) {
-        // The state was changed since the drag started; don't do anything.
-        if (!isDrivingTransition) {
-            return
-        }
-
-        fun animateTo(targetScene: Scene, targetOffset: Float) {
-            // If the effective current scene changed, it should be reflected right now in the
-            // current scene state, even before the settle animation is ongoing. That way all the
-            // swipeables and back handlers will be refreshed and the user can for instance quickly
-            // swipe vertically from A => B then horizontally from B => C, or swipe from A => B then
-            // immediately go back B => A.
-            if (targetScene != swipeTransition._currentScene) {
-                swipeTransition._currentScene = targetScene
-                layoutImpl.onChangeScene(targetScene.key)
-            }
-
-            animateOffset(
-                initialVelocity = velocity,
-                targetOffset = targetOffset,
-                targetScene = targetScene.key
-            )
-        }
-
-        val fromScene = swipeTransition._fromScene
-        if (canChangeScene) {
-            // If we are halfway between two scenes, we check what the target will be based on the
-            // velocity and offset of the transition, then we launch the animation.
-
-            val toScene = swipeTransition._toScene
-            if (fromScene == toScene) {
-                // We were not animating.
-                transitionState = TransitionState.Idle(fromScene.key)
-                return
-            }
-
-            // Compute the destination scene (and therefore offset) to settle in.
-            val offset = swipeTransition.dragOffset
-            val distance = swipeTransition.distance
-            if (
-                shouldCommitSwipe(
-                    offset,
-                    distance,
-                    velocity,
-                    wasCommitted = swipeTransition._currentScene == toScene,
-                )
-            ) {
-                // Animate to the next scene
-                animateTo(targetScene = toScene, targetOffset = distance)
-            } else {
-                // Animate to the initial scene
-                animateTo(targetScene = fromScene, targetOffset = 0f)
-            }
-        } else {
-            // We are doing an overscroll animation between scenes. In this case, we can also start
-            // from the idle position.
-
-            val startFromIdlePosition = swipeTransition.dragOffset == 0f
-
-            if (startFromIdlePosition) {
-                // If there is a next scene, we start the overscroll animation.
-                val target = fromScene.findTargetSceneAndDistance(velocity)
-                val isValidTarget = target.distance != 0f && target.sceneKey != fromScene.key
-                if (isValidTarget) {
-                    swipeTransition._toScene = layoutImpl.scene(target.sceneKey)
-                    swipeTransition._distance = target.distance
-
-                    animateTo(targetScene = fromScene, targetOffset = 0f)
-                } else {
-                    // We will not animate
-                    transitionState = TransitionState.Idle(fromScene.key)
-                }
-            } else {
-                // We were between two scenes: animate to the initial scene.
-                animateTo(targetScene = fromScene, targetOffset = 0f)
-            }
-        }
-    }
-
-    /**
-     * Whether the swipe to the target scene should be committed or not. This is inspired by
-     * SwipeableV2.computeTarget().
-     */
-    private fun shouldCommitSwipe(
-        offset: Float,
-        distance: Float,
-        velocity: Float,
-        wasCommitted: Boolean,
-    ): Boolean {
-        fun isCloserToTarget(): Boolean {
-            return (offset - distance).absoluteValue < offset.absoluteValue
-        }
-
-        // Swiping up or left.
-        if (distance < 0f) {
-            return if (offset > 0f || velocity >= velocityThreshold) {
-                false
-            } else {
-                velocity <= -velocityThreshold ||
-                    (offset <= -positionalThreshold && !wasCommitted) ||
-                    isCloserToTarget()
-            }
-        }
-
-        // Swiping down or right.
-        return if (offset < 0f || velocity <= -velocityThreshold) {
-            false
-        } else {
-            velocity >= velocityThreshold ||
-                (offset >= positionalThreshold && !wasCommitted) ||
-                isCloserToTarget()
-        }
-    }
-
-    private fun animateOffset(
-        initialVelocity: Float,
-        targetOffset: Float,
-        targetScene: SceneKey,
-    ) {
-        swipeTransition.startOffsetAnimation {
-            coroutineScope.launch {
-                if (!isAnimatingOffset) {
-                    swipeTransition.offsetAnimatable.snapTo(swipeTransition.dragOffset)
-                }
-                isAnimatingOffset = true
-
-                swipeTransition.offsetAnimatable.animateTo(
-                    targetOffset,
-                    // TODO(b/290184746): Make this spring spec configurable.
-                    spring(
-                        stiffness = Spring.StiffnessMediumLow,
-                        visibilityThreshold = OffsetVisibilityThreshold
-                    ),
-                    initialVelocity = initialVelocity,
-                )
-
-                isAnimatingOffset = false
-
-                // Now that the animation is done, the state should be idle. Note that if the state
-                // was changed since this animation started, some external code changed it and we
-                // shouldn't do anything here. Note also that this job will be cancelled in the case
-                // where the user intercepts this swipe.
-                if (isDrivingTransition) {
-                    transitionState = TransitionState.Idle(targetScene)
-                }
-            }
-        }
-    }
-
-    private class SwipeTransition(initialScene: Scene) : TransitionState.Transition {
-        var _currentScene by mutableStateOf(initialScene)
-        override val currentScene: SceneKey
-            get() = _currentScene.key
-
-        var _fromScene by mutableStateOf(initialScene)
-        override val fromScene: SceneKey
-            get() = _fromScene.key
-
-        var _toScene by mutableStateOf(initialScene)
-        override val toScene: SceneKey
-            get() = _toScene.key
-
-        override val progress: Float
-            get() {
-                val offset = if (isAnimatingOffset) offsetAnimatable.value else dragOffset
-                if (distance == 0f) {
-                    // This can happen only if fromScene == toScene.
-                    error(
-                        "Transition.progress should be called only when Transition.fromScene != " +
-                            "Transition.toScene"
-                    )
-                }
-                return offset / distance
-            }
-
-        override val isInitiatedByUserInput = true
-
-        /** The current offset caused by the drag gesture. */
-        var dragOffset by mutableFloatStateOf(0f)
-
-        /**
-         * Whether the offset is animated (the user lifted their finger) or if it is driven by
-         * gesture.
-         */
-        var isAnimatingOffset by mutableStateOf(false)
-
-        // If we are not animating offset, it means the offset is being driven by the user's finger.
-        override val isUserInputOngoing: Boolean
-            get() = !isAnimatingOffset
-
-        /** The animatable used to animate the offset once the user lifted its finger. */
-        val offsetAnimatable = Animatable(0f, OffsetVisibilityThreshold)
-
-        /** Job to check that there is at most one offset animation in progress. */
-        private var offsetAnimationJob: Job? = null
-
-        /** Ends any previous [offsetAnimationJob] and runs the new [job]. */
-        fun startOffsetAnimation(job: () -> Job) {
-            stopOffsetAnimation()
-            offsetAnimationJob = job()
-        }
-
-        /** Stops any ongoing offset animation. */
-        fun stopOffsetAnimation() {
-            offsetAnimationJob?.cancel()
-
-            if (isAnimatingOffset) {
-                isAnimatingOffset = false
-                dragOffset = offsetAnimatable.value
-            }
-        }
-
-        /** The absolute distance between [fromScene] and [toScene]. */
-        var absoluteDistance = 0f
-
-        /**
-         * The signed distance between [fromScene] and [toScene]. It is negative if [fromScene] is
-         * above or to the left of [toScene].
-         */
-        var _distance by mutableFloatStateOf(0f)
-        val distance: Float
-            get() = _distance
-
-        /** The [UserAction]s associated to this swipe. */
-        var actionUpOrLeft: UserAction = Back
-        var actionDownOrRight: UserAction = Back
-        var actionUpOrLeftNoEdge: UserAction? = null
-        var actionDownOrRightNoEdge: UserAction? = null
-
-        fun upOrLeft(scene: Scene): SceneKey? {
-            return scene.userActions[actionUpOrLeft]
-                ?: actionUpOrLeftNoEdge?.let { scene.userActions[it] }
-        }
-
-        fun downOrRight(scene: Scene): SceneKey? {
-            return scene.userActions[actionDownOrRight]
-                ?: actionDownOrRightNoEdge?.let { scene.userActions[it] }
-        }
-    }
-
-    companion object {
-        private const val TAG = "SceneGestureHandler"
-    }
-}
-
-private class SceneDraggableHandler(
-    private val gestureHandler: SceneGestureHandler,
-) : DraggableHandler {
-    override fun onDragStarted(startedPosition: Offset, pointersDown: Int) {
-        gestureHandler.gestureWithPriority = this
-        gestureHandler.onDragStarted(pointersDown, startedPosition)
-    }
-
-    override fun onDelta(pixels: Float) {
-        if (gestureHandler.gestureWithPriority == this) {
-            gestureHandler.onDrag(delta = pixels)
-        }
-    }
-
-    override fun onDragStopped(velocity: Float) {
-        if (gestureHandler.gestureWithPriority == this) {
-            gestureHandler.gestureWithPriority = null
-            gestureHandler.onDragStopped(velocity = velocity, canChangeScene = true)
-        }
-    }
-}
-
-@VisibleForTesting
-class SceneNestedScrollHandler(
-    private val gestureHandler: SceneGestureHandler,
-) : NestedScrollHandler {
-    override val connection: PriorityNestedScrollConnection = nestedScrollConnection()
-
-    private fun Offset.toAmount() =
-        when (gestureHandler.orientation) {
-            Orientation.Horizontal -> x
-            Orientation.Vertical -> y
-        }
-
-    private fun Velocity.toAmount() =
-        when (gestureHandler.orientation) {
-            Orientation.Horizontal -> x
-            Orientation.Vertical -> y
-        }
-
-    private fun Float.toOffset() =
-        when (gestureHandler.orientation) {
-            Orientation.Horizontal -> Offset(x = this, y = 0f)
-            Orientation.Vertical -> Offset(x = 0f, y = this)
-        }
-
-    private fun nestedScrollConnection(): PriorityNestedScrollConnection {
-        // The next potential scene is calculated during the canStart
-        var nextScene: SceneKey? = null
-
-        // This is the scene on which we will have priority during the scroll gesture.
-        var priorityScene: SceneKey? = null
-
-        // If we performed a long gesture before entering priority mode, we would have to avoid
-        // moving on to the next scene.
-        var gestureStartedOnNestedChild = false
-
-        val actionUpOrLeft =
-            Swipe(
-                direction =
-                    when (gestureHandler.orientation) {
-                        Orientation.Horizontal -> SwipeDirection.Left
-                        Orientation.Vertical -> SwipeDirection.Up
-                    },
-                pointerCount = 1,
-            )
-
-        val actionDownOrRight =
-            Swipe(
-                direction =
-                    when (gestureHandler.orientation) {
-                        Orientation.Horizontal -> SwipeDirection.Right
-                        Orientation.Vertical -> SwipeDirection.Down
-                    },
-                pointerCount = 1,
-            )
-
-        fun findNextScene(amount: Float): SceneKey? {
-            val fromScene = gestureHandler.currentScene
-            return when {
-                amount < 0f -> fromScene.userActions[actionUpOrLeft]
-                amount > 0f -> fromScene.userActions[actionDownOrRight]
-                else -> null
-            }
-        }
-
-        return PriorityNestedScrollConnection(
-            canStartPreScroll = { offsetAvailable, offsetBeforeStart ->
-                gestureStartedOnNestedChild = offsetBeforeStart != Offset.Zero
-
-                val canInterceptPreScroll =
-                    gestureHandler.isDrivingTransition &&
-                        !gestureStartedOnNestedChild &&
-                        offsetAvailable.toAmount() != 0f
-
-                if (!canInterceptPreScroll) return@PriorityNestedScrollConnection false
-
-                nextScene = gestureHandler.swipeTransitionToScene.key
-
-                true
-            },
-            canStartPostScroll = { offsetAvailable, offsetBeforeStart ->
-                val amount = offsetAvailable.toAmount()
-                if (amount == 0f) return@PriorityNestedScrollConnection false
-
-                gestureStartedOnNestedChild = offsetBeforeStart != Offset.Zero
-                nextScene = findNextScene(amount)
-                nextScene != null
-            },
-            canStartPostFling = { velocityAvailable ->
-                val amount = velocityAvailable.toAmount()
-                if (amount == 0f) return@PriorityNestedScrollConnection false
-
-                // We could start an overscroll animation
-                gestureStartedOnNestedChild = true
-                nextScene = findNextScene(amount)
-                nextScene != null
-            },
-            canContinueScroll = { priorityScene == gestureHandler.swipeTransitionToScene.key },
-            onStart = {
-                gestureHandler.gestureWithPriority = this
-                priorityScene = nextScene
-                gestureHandler.onDragStarted(pointersDown = 1, startedPosition = null)
-            },
-            onScroll = { offsetAvailable ->
-                if (gestureHandler.gestureWithPriority != this) {
-                    return@PriorityNestedScrollConnection Offset.Zero
-                }
-
-                val amount = offsetAvailable.toAmount()
-
-                // TODO(b/297842071) We should handle the overscroll or slow drag if the gesture is
-                // initiated in a nested child.
-                gestureHandler.onDrag(amount)
-
-                amount.toOffset()
-            },
-            onStop = { velocityAvailable ->
-                if (gestureHandler.gestureWithPriority != this) {
-                    return@PriorityNestedScrollConnection Velocity.Zero
-                }
-
-                priorityScene = null
-
-                gestureHandler.onDragStopped(
-                    velocity = velocityAvailable.toAmount(),
-                    canChangeScene = !gestureStartedOnNestedChild
-                )
-
-                // The onDragStopped animation consumes any remaining velocity.
-                velocityAvailable
-            },
-        )
-    }
-}
-
-/**
- * The number of pixels below which there won't be a visible difference in the transition and from
- * which the animation can stop.
- */
-private const val OffsetVisibilityThreshold = 0.5f