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Commit e73b0cb0 authored by omarmt's avatar omarmt
Browse files

SwipeToScene must have onPreScroll priority during a scene transition 

To support this case, PriorityNestedScrollConnection can now take
precedence even during preScroll, with its own initial conditions.

Test: atest PriorityNestedScrollConnectionTest
Bug: 291025415
Change-Id: I3ff22580d80b35ac6b94db64354422737ba783d7
parent 2c02d345

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

+20 −6
Original line number Diff line number Diff line
@@ -36,7 +36,7 @@ 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 com.android.compose.nestedscroll.PriorityPostNestedScrollConnection

import com.android.compose.nestedscroll.PriorityNestedScrollConnection

import kotlin.math.absoluteValue

import kotlinx.coroutines.CoroutineScope

import kotlinx.coroutines.Job
@@ -535,7 +535,7 @@ private class SceneDraggableHandler( 
class SceneNestedScrollHandler(

    private val gestureHandler: SceneGestureHandler,

) : NestedScrollHandler {

    override val connection: PriorityPostNestedScrollConnection = nestedScrollConnection()

    override val connection: PriorityNestedScrollConnection = nestedScrollConnection()



    private fun Offset.toAmount() =

        when (gestureHandler.orientation) {
@@ -555,7 +555,7 @@ class SceneNestedScrollHandler( 
            Orientation.Vertical -> Offset(x = 0f, y = this)

        }



    private fun nestedScrollConnection(): PriorityPostNestedScrollConnection {

    private fun nestedScrollConnection(): PriorityNestedScrollConnection {

        // The next potential scene is calculated during the canStart

        var nextScene: SceneKey? = null
@@ -566,10 +566,24 @@ class SceneNestedScrollHandler( 
        // moving on to the next scene.

        var gestureStartedOnNestedChild = false



        return PriorityPostNestedScrollConnection(

            canStart = { offsetAvailable, offsetBeforeStart ->

        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@PriorityPostNestedScrollConnection false

                if (amount == 0f) return@PriorityNestedScrollConnection false



                gestureStartedOnNestedChild = offsetBeforeStart != Offset.Zero

packages/SystemUI/compose/scene/src/com/android/compose/nestedscroll/PriorityPostNestedScrollConnection.kt→packages/SystemUI/compose/scene/src/com/android/compose/nestedscroll/PriorityNestedScrollConnection.kt

+32 −16
Original line number Diff line number Diff line
@@ -22,17 +22,18 @@ import androidx.compose.ui.input.nestedscroll.NestedScrollSource 
import androidx.compose.ui.unit.Velocity



/**

 * This [NestedScrollConnection] waits for a child to scroll ([onPostScroll]), and then decides (via

 * [canStart]) if it should take over scrolling. If it does, it will scroll before its children,

 * until [canContinueScroll] allows it.

 * This [NestedScrollConnection] waits for a child to scroll ([onPreScroll] or [onPostScroll]), and

 * then decides (via [canStartPreScroll] or [canStartPostScroll]) if it should take over scrolling.

 * If it does, it will scroll before its children, until [canContinueScroll] allows it.

 *

 * Note: Call [reset] before destroying this object to make sure you always get a call to [onStop]

 * after [onStart].

 *

 * @sample com.android.compose.animation.scene.rememberSwipeToSceneNestedScrollConnection

 */

class PriorityPostNestedScrollConnection(

    private val canStart: (offsetAvailable: Offset, offsetBeforeStart: Offset) -> Boolean,

class PriorityNestedScrollConnection(

    private val canStartPreScroll: (offsetAvailable: Offset, offsetBeforeStart: Offset) -> Boolean,

    private val canStartPostScroll: (offsetAvailable: Offset, offsetBeforeStart: Offset) -> Boolean,

    private val canContinueScroll: () -> Boolean,

    private val onStart: () -> Unit,

    private val onScroll: (offsetAvailable: Offset) -> Offset,
@@ -57,26 +58,21 @@ class PriorityPostNestedScrollConnection( 
        if (

            isPriorityMode ||

                source == NestedScrollSource.Fling ||

                !canStart(available, offsetBeforeStart)

                !canStartPostScroll(available, offsetBeforeStart)

        ) {

            // The priority mode cannot start so we won't consume the available offset.

            return Offset.Zero

        }



        // Step 1: It's our turn! We start capturing scroll events when one of our children has an

        // available offset following a scroll event.

        isPriorityMode = true



        // Note: onStop will be called if we cannot continue to scroll (step 3a), or the finger is

        // lifted (step 3b), or this object has been destroyed (step 3c).

        onStart()



        return onScroll(available)

        return onPriorityStart(available)

    }



    override fun onPreScroll(available: Offset, source: NestedScrollSource): Offset {

        if (!isPriorityMode) {

            if (source != NestedScrollSource.Fling) {

                if (canStartPreScroll(available, offsetScrolledBeforePriorityMode)) {

                    return onPriorityStart(available)

                }

                // We want to track the amount of offset consumed before entering priority mode

                offsetScrolledBeforePriorityMode += available

            }
@@ -87,6 +83,11 @@ class PriorityPostNestedScrollConnection( 
        if (!canContinueScroll()) {

            // Step 3a: We have lost priority and we no longer need to intercept scroll events.

            onPriorityStop(velocity = Velocity.Zero)



            // We've just reset offsetScrolledBeforePriorityMode to Offset.Zero

            // We want to track the amount of offset consumed before entering priority mode

            offsetScrolledBeforePriorityMode += available



            return Offset.Zero

        }
@@ -110,8 +111,23 @@ class PriorityPostNestedScrollConnection( 
        onPriorityStop(velocity = Velocity.Zero)

    }



    private fun onPriorityStop(velocity: Velocity): Velocity {

    private fun onPriorityStart(available: Offset): Offset {

        if (isPriorityMode) {

            error("This should never happen, onPriorityStart() was called when isPriorityMode")

        }



        // Step 1: It's our turn! We start capturing scroll events when one of our children has an

        // available offset following a scroll event.

        isPriorityMode = true



        // Note: onStop will be called if we cannot continue to scroll (step 3a), or the finger is

        // lifted (step 3b), or this object has been destroyed (step 3c).

        onStart()



        return onScroll(available)

    }



    private fun onPriorityStop(velocity: Velocity): Velocity {

        // We can restart tracking the consumed offsets from scratch.

        offsetScrolledBeforePriorityMode = Offset.Zero

packages/SystemUI/compose/scene/tests/src/com/android/compose/nestedscroll/PriorityPostNestedScrollConnectionTest.kt→packages/SystemUI/compose/scene/tests/src/com/android/compose/nestedscroll/PriorityNestedScrollConnectionTest.kt

+37 −14
Original line number Diff line number Diff line
@@ -29,8 +29,9 @@ import org.junit.Test 
import org.junit.runner.RunWith



@RunWith(AndroidJUnit4::class)

class PriorityPostNestedScrollConnectionTest {

    private var canStart = false

class PriorityNestedScrollConnectionTest {

    private var canStartPreScroll = false

    private var canStartPostScroll = false

    private var canContinueScroll = false

    private var isStarted = false

    private var lastScroll: Offset? = null
@@ -41,8 +42,9 @@ class PriorityPostNestedScrollConnectionTest { 
    private var returnOnPostFling = Velocity.Zero



    private val scrollConnection =

        PriorityPostNestedScrollConnection(

            canStart = { _, _ -> canStart },

        PriorityNestedScrollConnection(

            canStartPreScroll = { _, _ -> canStartPreScroll },

            canStartPostScroll = { _, _ -> canStartPostScroll },

            canContinueScroll = { canContinueScroll },

            onStart = { isStarted = true },

            onScroll = {
@@ -64,8 +66,29 @@ class PriorityPostNestedScrollConnectionTest { 
    private val velocity1 = Velocity(1f, 1f)

    private val velocity2 = Velocity(2f, 2f)



    private fun startPriorityMode() {

        canStart = true

    @Test

    fun step1_priorityModeShouldStartOnlyOnPreScroll() = runTest {

        canStartPreScroll = true



        scrollConnection.onPostScroll(

            consumed = Offset.Zero,

            available = Offset.Zero,

            source = NestedScrollSource.Drag

        )

        assertThat(isStarted).isEqualTo(false)



        scrollConnection.onPreFling(available = Velocity.Zero)

        assertThat(isStarted).isEqualTo(false)



        scrollConnection.onPostFling(consumed = Velocity.Zero, available = Velocity.Zero)

        assertThat(isStarted).isEqualTo(false)



        scrollConnection.onPreScroll(available = Offset.Zero, source = NestedScrollSource.Drag)

        assertThat(isStarted).isEqualTo(true)

    }



    private fun startPriorityModePostScroll() {

        canStartPostScroll = true

        scrollConnection.onPostScroll(

            consumed = Offset.Zero,

            available = Offset.Zero,
@@ -75,7 +98,7 @@ class PriorityPostNestedScrollConnectionTest { 


    @Test

    fun step1_priorityModeShouldStartOnlyOnPostScroll() = runTest {

        canStart = true

        canStartPostScroll = true



        scrollConnection.onPreScroll(available = Offset.Zero, source = NestedScrollSource.Drag)

        assertThat(isStarted).isEqualTo(false)
@@ -86,7 +109,7 @@ class PriorityPostNestedScrollConnectionTest { 
        scrollConnection.onPostFling(consumed = Velocity.Zero, available = Velocity.Zero)

        assertThat(isStarted).isEqualTo(false)



        startPriorityMode()

        startPriorityModePostScroll()

        assertThat(isStarted).isEqualTo(true)

    }
@@ -99,13 +122,13 @@ class PriorityPostNestedScrollConnectionTest { 
        )

        assertThat(isStarted).isEqualTo(false)



        startPriorityMode()

        startPriorityModePostScroll()

        assertThat(isStarted).isEqualTo(true)

    }



    @Test

    fun step1_onPriorityModeStarted_receiveAvailableOffset() {

        canStart = true

        canStartPostScroll = true



        scrollConnection.onPostScroll(

            consumed = offset1,
@@ -118,7 +141,7 @@ class PriorityPostNestedScrollConnectionTest { 


    @Test

    fun step2_onPriorityMode_shouldContinueIfAllowed() {

        startPriorityMode()

        startPriorityModePostScroll()

        canContinueScroll = true



        scrollConnection.onPreScroll(available = offset1, source = NestedScrollSource.Drag)
@@ -132,7 +155,7 @@ class PriorityPostNestedScrollConnectionTest { 


    @Test

    fun step3a_onPriorityMode_shouldStopIfCannotContinue() {

        startPriorityMode()

        startPriorityModePostScroll()

        canContinueScroll = false



        scrollConnection.onPreScroll(available = Offset.Zero, source = NestedScrollSource.Drag)
@@ -142,7 +165,7 @@ class PriorityPostNestedScrollConnectionTest { 


    @Test

    fun step3b_onPriorityMode_shouldStopOnFling() = runTest {

        startPriorityMode()

        startPriorityModePostScroll()

        canContinueScroll = true



        scrollConnection.onPreFling(available = Velocity.Zero)
@@ -152,7 +175,7 @@ class PriorityPostNestedScrollConnectionTest { 


    @Test

    fun step3c_onPriorityMode_shouldStopOnReset() {

        startPriorityMode()

        startPriorityModePostScroll()

        canContinueScroll = true



        scrollConnection.reset()