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Commit 9a42e828 authored by omarmt's avatar omarmt
Browse files

Expose startedPosition and pointersDown to NestedScrollHandler 

Until now, we have handled scrolls as gestures without a specific
starting position (using null) and have only considered one finger on
the screen.

Moving forward, we aim to accurately expose this information and we can
achieve this by leveraging the PointerInput API.
The NestedScrollToSceneNode now employs a PointerInputHandler to
determine the number of pointers and obtain the starting position during
 the nested scroll.
The PointerInputHandler awaits the creation of the
AwaitPointerEventScope to register the nestedScrollHandler.
This approach ensures that touch events are always received by the
PointerInputHandler first, in the Initial step, and later these events
are consumed by our descendant scrollable in the Main step.

Test: atest ElementTest
Bug: 330200163
Flag: com.android.systemui.scene_container
Change-Id: Ib912aec5af40145af7a0d580aa81b3098d0ad092
parent 6d28c900

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/DraggableHandler.kt

+28 −24
Original line number Diff line number Diff line
@@ -889,6 +889,7 @@ internal class NestedScrollHandlerImpl( 
    private val topOrLeftBehavior: NestedScrollBehavior,

    private val bottomOrRightBehavior: NestedScrollBehavior,

    private val isExternalOverscrollGesture: () -> Boolean,

    private val pointersInfo: () -> PointersInfo,

) {

    private val layoutState = layoutImpl.state

    private val draggableHandler = layoutImpl.draggableHandler(orientation)
@@ -900,6 +901,13 @@ internal class NestedScrollHandlerImpl( 
        // moving on to the next scene.

        var canChangeScene = false



        fun hasNextScene(amount: Float): Boolean {

            val transitionState = layoutState.transitionState

            val scene = transitionState.currentScene

            val fromScene = layoutImpl.scene(scene)

            val nextScene =

                when {

                    amount < 0f -> {

                        val actionUpOrLeft =

                            Swipe(

                                direction =
@@ -907,9 +915,11 @@ internal class NestedScrollHandlerImpl( 
                                        Orientation.Horizontal -> SwipeDirection.Left

                                        Orientation.Vertical -> SwipeDirection.Up

                                    },

                pointerCount = 1,

                                pointerCount = pointersInfo().pointersDown,

                            )



                        fromScene.userActions[actionUpOrLeft]

                    }

                    amount > 0f -> {

                        val actionDownOrRight =

                            Swipe(

                                direction =
@@ -917,17 +927,10 @@ internal class NestedScrollHandlerImpl( 
                                        Orientation.Horizontal -> SwipeDirection.Right

                                        Orientation.Vertical -> SwipeDirection.Down

                                    },

                pointerCount = 1,

                                pointerCount = pointersInfo().pointersDown,

                            )



        fun hasNextScene(amount: Float): Boolean {

            val transitionState = layoutState.transitionState

            val scene = transitionState.currentScene

            val fromScene = layoutImpl.scene(scene)

            val nextScene =

                when {

                    amount < 0f -> fromScene.userActions[actionUpOrLeft]

                    amount > 0f -> fromScene.userActions[actionDownOrRight]

                        fromScene.userActions[actionDownOrRight]

                    }

                    else -> null

                }

            if (nextScene != null) return true
@@ -1025,10 +1028,11 @@ internal class NestedScrollHandlerImpl( 
            canContinueScroll = { true },

            canScrollOnFling = false,

            onStart = { offsetAvailable ->

                val pointers = pointersInfo()

                dragController =

                    draggableHandler.onDragStarted(

                        pointersDown = 1,

                        startedPosition = null,

                        pointersDown = pointers.pointersDown,

                        startedPosition = pointers.startedPosition,

                        overSlop = if (isIntercepting) 0f else offsetAvailable,

                    )

            },

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/NestedScrollToScene.kt

+53 −11
Original line number Diff line number Diff line
@@ -18,12 +18,21 @@ package com.android.compose.animation.scene 


import androidx.compose.foundation.gestures.Orientation

import androidx.compose.ui.Modifier

import androidx.compose.ui.geometry.Offset

import androidx.compose.ui.input.nestedscroll.nestedScrollModifierNode

import androidx.compose.ui.input.pointer.PointerEventPass

import androidx.compose.ui.input.pointer.PointerInputChange

import androidx.compose.ui.input.pointer.PointerInputScope

import androidx.compose.ui.input.pointer.SuspendingPointerInputModifierNode

import androidx.compose.ui.node.DelegatableNode

import androidx.compose.ui.node.DelegatingNode

import androidx.compose.ui.node.ModifierNodeElement

import androidx.compose.ui.platform.InspectorInfo

import androidx.compose.ui.util.fastMap

import androidx.compose.ui.util.fastReduce

import com.android.compose.nestedscroll.PriorityNestedScrollConnection

import kotlinx.coroutines.coroutineScope

import kotlinx.coroutines.isActive



/**

 * Defines the behavior of the [SceneTransitionLayout] when a scrollable component is scrolled.
@@ -121,6 +130,11 @@ private data class NestedScrollToSceneElement( 
    }

}



internal data class PointersInfo(

    val pointersDown: Int,

    val startedPosition: Offset,

)



private class NestedScrollToSceneNode(

    layoutImpl: SceneTransitionLayoutImpl,

    orientation: Orientation,
@@ -135,22 +149,48 @@ private class NestedScrollToSceneNode( 
            topOrLeftBehavior = topOrLeftBehavior,

            bottomOrRightBehavior = bottomOrRightBehavior,

            isExternalOverscrollGesture = isExternalOverscrollGesture,

            pointersInfo = pointerInfo()

        )



    private var nestedScrollNode: DelegatableNode =

        nestedScrollModifierNode(

            connection = priorityNestedScrollConnection,

            dispatcher = null,

    private var lastPointers: List<PointerInputChange>? = null



    private fun pointerInfo(): () -> PointersInfo = {

        val pointers =

            requireNotNull(lastPointers) { "NestedScroll API was called before PointerInput API" }

        PointersInfo(

            pointersDown = pointers.size,

            startedPosition = pointers.fastMap { it.position }.fastReduce { a, b -> (a + b) / 2f },

        )

    }



    override fun onAttach() {

    private val pointerInputHandler: suspend PointerInputScope.() -> Unit = {

        coroutineScope {

            awaitPointerEventScope {

                // Await this scope to guarantee that the PointerInput API receives touch events

                // before the NestedScroll API.

                delegate(nestedScrollNode)

    }



    override fun onDetach() {

        // Make sure we reset the scroll connection when this modifier is removed from composition

                try {

                    while (isActive) {

                        // During the initial phase, we receive the event after our ancestors.

                        lastPointers = awaitPointerEvent(PointerEventPass.Initial).changes

                    }

                } finally {

                    // Clean up the nested scroll connection

                    priorityNestedScrollConnection.reset()

                    undelegate(nestedScrollNode)

                }

            }

        }

    }



    private val pointerInputNode = delegate(SuspendingPointerInputModifierNode(pointerInputHandler))



    private var nestedScrollNode: DelegatableNode =

        nestedScrollModifierNode(

            connection = priorityNestedScrollConnection,

            dispatcher = null,

        )



    fun update(

        layoutImpl: SceneTransitionLayoutImpl,
@@ -161,7 +201,7 @@ private class NestedScrollToSceneNode( 
    ) {

        // Clean up the old nested scroll connection

        priorityNestedScrollConnection.reset()

        undelegate(nestedScrollNode)

        pointerInputNode.resetPointerInputHandler()



        // Create a new nested scroll connection

        priorityNestedScrollConnection =
@@ -171,13 +211,13 @@ private class NestedScrollToSceneNode( 
                topOrLeftBehavior = topOrLeftBehavior,

                bottomOrRightBehavior = bottomOrRightBehavior,

                isExternalOverscrollGesture = isExternalOverscrollGesture,

                pointersInfo = pointerInfo(),

            )

        nestedScrollNode =

            nestedScrollModifierNode(

                connection = priorityNestedScrollConnection,

                dispatcher = null,

            )

        delegate(nestedScrollNode)

    }

}
@@ -187,6 +227,7 @@ private fun scenePriorityNestedScrollConnection( 
    topOrLeftBehavior: NestedScrollBehavior,

    bottomOrRightBehavior: NestedScrollBehavior,

    isExternalOverscrollGesture: () -> Boolean,

    pointersInfo: () -> PointersInfo,

) =

    NestedScrollHandlerImpl(

            layoutImpl = layoutImpl,
@@ -194,5 +235,6 @@ private fun scenePriorityNestedScrollConnection( 
            topOrLeftBehavior = topOrLeftBehavior,

            bottomOrRightBehavior = bottomOrRightBehavior,

            isExternalOverscrollGesture = isExternalOverscrollGesture,

            pointersInfo = pointersInfo,

        )

        .connection

packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/DraggableHandlerTest.kt

+2 −1
Original line number Diff line number Diff line
@@ -111,7 +111,8 @@ class DraggableHandlerTest { 
                    orientation = draggableHandler.orientation,

                    topOrLeftBehavior = nestedScrollBehavior,

                    bottomOrRightBehavior = nestedScrollBehavior,

                    isExternalOverscrollGesture = { isExternalOverscrollGesture }

                    isExternalOverscrollGesture = { isExternalOverscrollGesture },

                    pointersInfo = { PointersInfo(pointersDown = 1, startedPosition = Offset.Zero) }

                )

                .connection

packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/ElementTest.kt

+73 −0
Original line number Diff line number Diff line
@@ -836,6 +836,79 @@ class ElementTest { 
        fooElement.assertTopPositionInRootIsEqualTo(overscrollTranslateY * 1.5f)

    }



    @Test

    fun elementTransitionDuringNestedScrollWith2Pointers() {

        // 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 translateY = 10.dp

        val layoutWidth = 200.dp

        val layoutHeight = 400.dp



        val state =

            rule.runOnUiThread {

                MutableSceneTransitionLayoutState(

                    initialScene = SceneA,

                    transitions = transitions {

                        from(SceneA, to = SceneB) {

                            translate(TestElements.Foo, y = translateY)

                        }

                    },

                )

                    as MutableSceneTransitionLayoutStateImpl

            }



        rule.setContent {

            touchSlop = LocalViewConfiguration.current.touchSlop

            SceneTransitionLayout(

                state = state,

                modifier = Modifier.size(layoutWidth, layoutHeight)

            ) {

                scene(

                    SceneA,

                    userActions = mapOf(Swipe(SwipeDirection.Down, pointerCount = 2) to SceneB)

                ) {

                    Box(

                        Modifier

                            // Unconsumed scroll gesture will be intercepted by STL

                            .verticalNestedScrollToScene()

                            // A scrollable that does not consume the scroll gesture

                            .scrollable(

                                rememberScrollableState(consumeScrollDelta = { 0f }),

                                Orientation.Vertical

                            )

                            .fillMaxSize()

                    ) {

                        Spacer(Modifier.element(TestElements.Foo).fillMaxSize())

                    }

                }

                scene(SceneB) { Spacer(Modifier.fillMaxSize()) }

            }

        }



        assertThat(state.transitionState).isIdle()

        val fooElement = rule.onNodeWithTag(TestElements.Foo.testTag)

        fooElement.assertTopPositionInRootIsEqualTo(0.dp)



        // Swipe down with 2 pointers by half of verticalSwipeDistance.

        rule.onRoot().performTouchInput {

            val middleTop = Offset((layoutWidth / 2).toPx(), 0f)

            repeat(2) { i -> down(pointerId = i, middleTop) }

            repeat(2) { i ->

                // Scroll 50%

                moveBy(

                    pointerId = i,

                    delta = Offset(0f, touchSlop + layoutHeight.toPx() * 0.5f),

                    delayMillis = 1_000,

                )

            }

        }



        val transition = assertThat(state.transitionState).isTransition()

        assertThat(transition).hasProgress(0.5f)

        fooElement.assertTopPositionInRootIsEqualTo(translateY * 0.5f)

    }



    @Test

    fun elementTransitionWithDistanceDuringOverscroll() {

        val layoutWidth = 200.dp