Simplify PriorityNestedScrollConnection (40c5c231) · Commits · e / os / android_frameworks_base

packages/SystemUI/compose/features/src/com/android/systemui/notifications/ui/composable/NotificationScrimNestedScrollConnection.kt

+8 −10

Original line number	Diff line number	Diff line
		@@ -18,6 +18,8 @@ package com.android.systemui.notifications.ui.composable

		import androidx.compose.foundation.gestures.Orientation
		import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
		import androidx.compose.ui.util.fastCoerceAtLeast
		import androidx.compose.ui.util.fastCoerceAtMost
		import com.android.compose.nestedscroll.PriorityNestedScrollConnection

		/**
		@@ -44,7 +46,7 @@ fun NotificationScrimNestedScrollConnection(
		orientation = Orientation.Vertical,
		// scrolling up and inner content is taller than the scrim, so scrim needs to
		// expand; content can scroll once scrim is at the minScrimOffset.
		canStartPreScroll = { offsetAvailable, offsetBeforeStart ->
		canStartPreScroll = { offsetAvailable, offsetBeforeStart, _ ->
		offsetAvailable < 0 &&
		offsetBeforeStart == 0f &&
		contentHeight() > minVisibleScrimHeight() &&
		@@ -52,25 +54,21 @@ fun NotificationScrimNestedScrollConnection(
		},
		// scrolling down and content is done scrolling to top. After that, the scrim
		// needs to collapse; collapse the scrim until it is at the maxScrimOffset.
		canStartPostScroll = { offsetAvailable, _ ->
		canStartPostScroll = { offsetAvailable, _, _ ->
		offsetAvailable > 0 && (scrimOffset() < maxScrimOffset \|\| isCurrentGestureOverscroll())
		},
		canStartPostFling = { false },
		canContinueScroll = {
		val currentHeight = scrimOffset()
		minScrimOffset() < currentHeight && currentHeight < maxScrimOffset
		},
		canScrollOnFling = true,
		canStopOnPreFling = { false },
		onStart = { offsetAvailable -> onStart(offsetAvailable) },
		onScroll = { offsetAvailable ->
		onScroll = { offsetAvailable, _ ->
		val currentHeight = scrimOffset()
		val amountConsumed =
		if (offsetAvailable > 0) {
		val amountLeft = maxScrimOffset - currentHeight
		offsetAvailable.coerceAtMost(amountLeft)
		offsetAvailable.fastCoerceAtMost(amountLeft)
		} else {
		val amountLeft = minScrimOffset() - currentHeight
		offsetAvailable.coerceAtLeast(amountLeft)
		offsetAvailable.fastCoerceAtLeast(amountLeft)
		}
		snapScrimOffset(currentHeight + amountConsumed)
		amountConsumed

packages/SystemUI/compose/features/src/com/android/systemui/notifications/ui/composable/NotificationStackNestedScrollConnection.kt

+11 −7

Original line number	Diff line number	Diff line
		@@ -28,6 +28,7 @@ import androidx.compose.ui.platform.LocalConfiguration
		import androidx.compose.ui.platform.LocalDensity
		import androidx.compose.ui.unit.IntOffset
		import androidx.compose.ui.unit.dp
		import androidx.compose.ui.util.fastCoerceAtLeast
		import com.android.compose.nestedscroll.PriorityNestedScrollConnection
		import kotlin.math.max
		import kotlin.math.roundToInt
		@@ -86,17 +87,20 @@ fun NotificationStackNestedScrollConnection(
		): PriorityNestedScrollConnection {
		return PriorityNestedScrollConnection(
		orientation = Orientation.Vertical,
		canStartPreScroll = { _, _ -> false },
		canStartPostScroll = { offsetAvailable, offsetBeforeStart ->
		canStartPreScroll = { _, _, _ -> false },
		canStartPostScroll = { offsetAvailable, offsetBeforeStart, _ ->
		offsetAvailable < 0f && offsetBeforeStart < 0f && !canScrollForward()
		},
		canStartPostFling = { velocityAvailable -> velocityAvailable < 0f && !canScrollForward() },
		canContinueScroll = { stackOffset() > 0f },
		canScrollOnFling = true,
		canStopOnPreFling = { false },
		onStart = { offsetAvailable -> onStart(offsetAvailable) },
		onScroll = { offsetAvailable ->
		onScroll(offsetAvailable)
		offsetAvailable
		onScroll = { offsetAvailable, _ ->
		val minOffset = 0f
		val consumed = offsetAvailable.fastCoerceAtLeast(minOffset - stackOffset())
		if (consumed != 0f) {
		onScroll(consumed)
		}
		consumed
		},
		onStop = { velocityAvailable ->
		onStop(velocityAvailable)

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

+4 −5

Original line number	Diff line number	Diff line
		@@ -612,7 +612,7 @@ internal class NestedScrollHandlerImpl(

		return PriorityNestedScrollConnection(
		orientation = orientation,
		canStartPreScroll = { offsetAvailable, offsetBeforeStart ->
		canStartPreScroll = { offsetAvailable, offsetBeforeStart, _ ->
		canChangeScene =
		if (isExternalOverscrollGesture()) false else offsetBeforeStart == 0f

		@@ -638,7 +638,7 @@ internal class NestedScrollHandlerImpl(
		isIntercepting = true
		true
		},
		canStartPostScroll = { offsetAvailable, offsetBeforeStart ->
		canStartPostScroll = { offsetAvailable, offsetBeforeStart, _ ->
		val behavior: NestedScrollBehavior =
		when {
		offsetAvailable > 0f -> topOrLeftBehavior
		@@ -693,8 +693,7 @@ internal class NestedScrollHandlerImpl(

		canStart
		},
		canContinueScroll = { true },
		canScrollOnFling = false,
		canStopOnPreFling = { true },
		onStart = { offsetAvailable ->
		val pointersInfo = pointersInfo()
		dragController =
		@@ -704,7 +703,7 @@ internal class NestedScrollHandlerImpl(
		overSlop = if (isIntercepting) 0f else offsetAvailable,
		)
		},
		onScroll = { offsetAvailable ->
		onScroll = { offsetAvailable, _ ->
		val controller = dragController ?: error("Should be called after onStart")

		// TODO(b/297842071) We should handle the overscroll or slow drag if the gesture is

packages/SystemUI/compose/scene/src/com/android/compose/nestedscroll/LargeTopAppBarNestedScrollConnection.kt

+8 −10

Original line number	Diff line number	Diff line
		@@ -18,6 +18,8 @@ package com.android.compose.nestedscroll

		import androidx.compose.foundation.gestures.Orientation
		import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
		import androidx.compose.ui.util.fastCoerceAtLeast
		import androidx.compose.ui.util.fastCoerceAtMost

		/**
		* A [NestedScrollConnection] that listens for all vertical scroll events and responds in the
		@@ -43,30 +45,26 @@ fun LargeTopAppBarNestedScrollConnection(
		orientation = Orientation.Vertical,
		// When swiping up, the LargeTopAppBar will shrink (to [minHeight]) and the content will
		// expand. Then, you can then scroll down the content.
		canStartPreScroll = { offsetAvailable, offsetBeforeStart ->
		canStartPreScroll = { offsetAvailable, offsetBeforeStart, _ ->
		offsetAvailable < 0 && offsetBeforeStart == 0f && height() > minHeight()
		},
		// When swiping down, the content will scroll up until it reaches the top. Then, the
		// LargeTopAppBar will expand until it reaches its [maxHeight].
		canStartPostScroll = { offsetAvailable, _ ->
		canStartPostScroll = { offsetAvailable, _, _ ->
		offsetAvailable > 0 && height() < maxHeight()
		},
		canStartPostFling = { false },
		canContinueScroll = {
		val currentHeight = height()
		minHeight() < currentHeight && currentHeight < maxHeight()
		},
		canScrollOnFling = true,
		canStopOnPreFling = { false },
		onStart = { /* do nothing */ },
		onScroll = { offsetAvailable ->
		onScroll = { offsetAvailable, _ ->
		val currentHeight = height()
		val amountConsumed =
		if (offsetAvailable > 0) {
		val amountLeft = maxHeight() - currentHeight
		offsetAvailable.coerceAtMost(amountLeft)
		offsetAvailable.fastCoerceAtMost(amountLeft)
		} else {
		val amountLeft = minHeight() - currentHeight
		offsetAvailable.coerceAtLeast(amountLeft)
		offsetAvailable.fastCoerceAtLeast(amountLeft)
		}
		onHeightChanged(currentHeight + amountConsumed)
		amountConsumed

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

+94 −56

Original line number	Diff line number	Diff line
		@@ -27,25 +27,39 @@ import kotlin.math.sign
		internal typealias SuspendedValue<T> = suspend () -> T

		/**
		* 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.
		* A [NestedScrollConnection] that intercepts scroll events in priority mode.
		*
		* Note: Call [reset] before destroying this object to make sure you always get a call to [onStop]
		* after [onStart].
		* Priority mode allows this connection to take control over scroll events within a nested scroll
		* hierarchy. When in priority mode, this connection consumes scroll events before its children,
		* enabling custom scrolling behaviors like sticky headers.
		*
		* @param orientation The orientation of the scroll.
		* @param canStartPreScroll lambda that returns true if the connection can start consuming scroll
		* events in pre-scroll mode.
		* @param canStartPostScroll lambda that returns true if the connection can start consuming scroll
		* events in post-scroll mode.
		* @param canStartPostFling lambda that returns true if the connection can start consuming scroll
		* events in post-fling mode.
		* @param canStopOnPreFling lambda that returns true if the connection can stop consuming scroll
		* events in pre-fling (i.e. as soon as the user lifts their fingers).
		* @param onStart lambda that is called when the connection starts consuming scroll events.
		* @param onScroll lambda that is called when the connection consumes a scroll event and returns the
		* consumed amount.
		* @param onStop lambda that is called when the connection stops consuming scroll events and returns
		* the consumed velocity.
		* @sample LargeTopAppBarNestedScrollConnection
		* @sample com.android.compose.animation.scene.NestedScrollHandlerImpl.nestedScrollConnection
		*/
		class PriorityNestedScrollConnection(
		orientation: Orientation,
		private val canStartPreScroll: (offsetAvailable: Float, offsetBeforeStart: Float) -> Boolean,
		private val canStartPostScroll: (offsetAvailable: Float, offsetBeforeStart: Float) -> Boolean,
		private val canStartPreScroll:
		(offsetAvailable: Float, offsetBeforeStart: Float, source: NestedScrollSource) -> Boolean,
		private val canStartPostScroll:
		(offsetAvailable: Float, offsetBeforeStart: Float, source: NestedScrollSource) -> Boolean,
		private val canStartPostFling: (velocityAvailable: Float) -> Boolean,
		private val canContinueScroll: (source: NestedScrollSource) -> Boolean,
		private val canScrollOnFling: Boolean,
		private val canStopOnPreFling: () -> Boolean,
		private val onStart: (offsetAvailable: Float) -> Unit,
		private val onScroll: (offsetAvailable: Float) -> Float,
		private val onScroll: (offsetAvailable: Float, source: NestedScrollSource) -> Float,
		private val onStop: (velocityAvailable: Float) -> SuspendedValue<Float>,
		) : NestedScrollConnection, SpaceVectorConverter by SpaceVectorConverter(orientation) {

		@@ -64,62 +78,48 @@ class PriorityNestedScrollConnection(
		// the beginning or from the last fling gesture.
		val offsetBeforeStart = offsetScrolledBeforePriorityMode - availableFloat

		if (
		isPriorityMode \|\|
		(source == NestedScrollSource.SideEffect && !canScrollOnFling) \|\|
		!canStartPostScroll(availableFloat, offsetBeforeStart)
		) {
		if (isPriorityMode \|\| !canStartPostScroll(availableFloat, offsetBeforeStart, source)) {
		// The priority mode cannot start so we won't consume the available offset.
		return Offset.Zero
		}

		return onPriorityStart(availableFloat).toOffset()
		return start(availableFloat, source).toOffset()
		}

		override fun onPreScroll(available: Offset, source: NestedScrollSource): Offset {
		if (!isPriorityMode) {
		if (source == NestedScrollSource.UserInput \|\| canScrollOnFling) {
		val availableFloat = available.toFloat()
		if (canStartPreScroll(availableFloat, offsetScrolledBeforePriorityMode)) {
		return onPriorityStart(availableFloat).toOffset()
		if (canStartPreScroll(availableFloat, offsetScrolledBeforePriorityMode, source)) {
		return start(availableFloat, source).toOffset()
		}
		// We want to track the amount of offset consumed before entering priority mode
		offsetScrolledBeforePriorityMode += availableFloat
		}

		return Offset.Zero
		}

		val availableFloat = available.toFloat()
		if (!canContinueScroll(source)) {
		// Step 3a: We have lost priority and we no longer need to intercept scroll events.
		onPriorityStop(velocity = 0f)

		// We've just reset offsetScrolledBeforePriorityMode to 0f
		// We want to track the amount of offset consumed before entering priority mode
		offsetScrolledBeforePriorityMode += availableFloat
		return scroll(available.toFloat(), source).toOffset()
		}

		return Offset.Zero
		override suspend fun onPreFling(available: Velocity): Velocity {
		if (!isPriorityMode) {
		resetOffsetTracker()
		return Velocity.Zero
		}

		// Step 2: We have the priority and can consume the scroll events.
		return onScroll(availableFloat).toOffset()
		if (canStopOnPreFling()) {
		// Step 3b: The finger is lifted, we can stop intercepting scroll events and use the
		// velocity of the fling gesture.
		return stop(velocityAvailable = available.toFloat()).toVelocity()
		}

		override suspend fun onPreFling(available: Velocity): Velocity {
		if (isPriorityMode && canScrollOnFling) {
		// We don't want to consume the velocity, we prefer to continue receiving scroll events.
		return Velocity.Zero
		}
		// Step 3b: The finger is lifted, we can stop intercepting scroll events and use the speed
		// of the fling gesture.
		return onPriorityStop(velocity = available.toFloat()).invoke().toVelocity()
		}

		override suspend fun onPostFling(consumed: Velocity, available: Velocity): Velocity {
		val availableFloat = available.toFloat()
		if (isPriorityMode) {
		return onPriorityStop(velocity = availableFloat).invoke().toVelocity()
		return stop(velocityAvailable = availableFloat).toVelocity()
		}

		if (!canStartPostFling(availableFloat)) {
		@@ -131,10 +131,14 @@ class PriorityNestedScrollConnection(
		// TODO(b/291053278): Remove canStartPostFling() and instead make it possible to define the
		// overscroll behavior on the Scene level.
		val smallOffset = availableFloat.sign
		onPriorityStart(availableOffset = smallOffset)
		start(
		availableOffset = smallOffset,
		source = NestedScrollSource.SideEffect,
		skipScroll = true,
		)

		// This is the last event of a scroll gesture.
		return onPriorityStop(availableFloat).invoke().toVelocity()
		return stop(availableFloat).toVelocity()
		}

		/**
		@@ -143,13 +147,25 @@ class PriorityNestedScrollConnection(
		* TODO(b/303224944) This method should be removed.
		*/
		fun reset() {
		if (isPriorityMode) {
		// Step 3c: To ensure that an onStop is always called for every onStart.
		onPriorityStop(velocity = 0f)
		cancel()
		} else {
		resetOffsetTracker()
		}
		}

		private fun onPriorityStart(availableOffset: Float): Float {
		if (isPriorityMode) {
		error("This should never happen, onPriorityStart() was called when isPriorityMode")
		private fun shouldStop(consumed: Float): Boolean {
		return consumed == 0f
		}

		private fun start(
		availableOffset: Float,
		source: NestedScrollSource,
		skipScroll: Boolean = false,
		): Float {
		check(!isPriorityMode) {
		"This should never happen, start() was called when isPriorityMode"
		}

		// Step 1: It's our turn! We start capturing scroll events when one of our children has an
		@@ -160,19 +176,41 @@ class PriorityNestedScrollConnection(
		// lifted (step 3b), or this object has been destroyed (step 3c).
		onStart(availableOffset)

		return onScroll(availableOffset)
		return if (skipScroll) 0f else scroll(availableOffset, source)
		}

		private fun onPriorityStop(velocity: Float): SuspendedValue<Float> {
		// We can restart tracking the consumed offsets from scratch.
		offsetScrolledBeforePriorityMode = 0f
		private fun scroll(offsetAvailable: Float, source: NestedScrollSource): Float {
		// Step 2: We have the priority and can consume the scroll events.
		val consumedByScroll = onScroll(offsetAvailable, source)

		if (!isPriorityMode) {
		return { 0f }
		if (shouldStop(consumedByScroll)) {
		// Step 3a: We have lost priority and we no longer need to intercept scroll events.
		cancel()

		// We've just reset offsetScrolledBeforePriorityMode to 0f
		// We want to track the amount of offset consumed before entering priority mode
		offsetScrolledBeforePriorityMode += offsetAvailable - consumedByScroll
		}

		return consumedByScroll
		}

		/** Reset the tracking of consumed offsets before entering in priority mode. */
		private fun resetOffsetTracker() {
		offsetScrolledBeforePriorityMode = 0f
		}

		private suspend fun stop(velocityAvailable: Float): Float {
		check(isPriorityMode) { "This should never happen, stop() was called before start()" }
		isPriorityMode = false
		resetOffsetTracker()
		return onStop(velocityAvailable).invoke()
		}

		return onStop(velocity)
		private fun cancel() {
		check(isPriorityMode) { "This should never happen, cancel() was called before start()" }
		isPriorityMode = false
		resetOffsetTracker()
		onStop(0f)
		}
		}