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Commit 6bb2f26c authored by Mike Schneider's avatar Mike Schneider
Browse files

SwipeToDismiss with MotionValue 

- Extract code into `overscrollToDismiss` Modifier
- set `beyondViewportPageCount` to 1 to avoid recomposition during
  animation

Tests:
- Add dependencies for motion tests in `PlatformComposeCore`
- Change test activity theme to `NoActionBar` to ensure composable is
  visible in recordings

Test: OverscrollToDismissTest
Flag: EXEMPT code not in use in production
Change-Id: I9dc94966de7c288e9919680a60a6b2be6bc592ca
parent 13f26f5a

packages/SystemUI/compose/core/Android.bp

+1 −0
Original line number Diff line number Diff line
@@ -40,6 +40,7 @@ android_library { 
        "androidx.savedstate_savedstate",

        "androidx.window_window",

        "//frameworks/libs/systemui:tracinglib-platform",

        "//frameworks/libs/systemui:mechanics",

    ],



    kotlincflags: [

packages/SystemUI/compose/core/src/com/android/compose/gesture/NestedDraggable.kt

+1 −1
Original line number Diff line number Diff line
@@ -205,7 +205,7 @@ private data class NestedDraggableElement( 
 * A root node on top of [NestedDraggableNode] so that no [PointerInputModifierNode] is installed

 * when this draggable is disabled.

 */

private class NestedDraggableRootNode(

internal class NestedDraggableRootNode(

    draggable: NestedDraggable,

    orientation: Orientation,

    overscrollEffect: OverscrollEffect?,

packages/SystemUI/compose/core/src/com/android/compose/gesture/OverscrollToDismiss.kt

0 → 100644
+221 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2025 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */



package com.android.compose.gesture



import androidx.compose.foundation.gestures.Orientation

import androidx.compose.ui.Modifier

import androidx.compose.ui.geometry.Offset

import androidx.compose.ui.input.pointer.PointerType

import androidx.compose.ui.layout.Measurable

import androidx.compose.ui.layout.MeasureResult

import androidx.compose.ui.layout.MeasureScope

import androidx.compose.ui.node.CompositionLocalConsumerModifierNode

import androidx.compose.ui.node.DelegatingNode

import androidx.compose.ui.node.LayoutModifierNode

import androidx.compose.ui.node.ModifierNodeElement

import androidx.compose.ui.node.ObserverModifierNode

import androidx.compose.ui.node.currentValueOf

import androidx.compose.ui.node.observeReads

import androidx.compose.ui.node.requireDensity

import androidx.compose.ui.platform.InspectorInfo

import androidx.compose.ui.platform.LocalViewConfiguration

import androidx.compose.ui.unit.Constraints

import androidx.compose.ui.unit.dp

import com.android.mechanics.DistanceGestureContext

import com.android.mechanics.MotionValue

import com.android.mechanics.debug.findMotionValueDebugger

import com.android.mechanics.effects.MagneticDetach

import com.android.mechanics.effects.MagneticDetach.Companion.Defaults.AttachDetachState

import com.android.mechanics.spec.InputDirection

import com.android.mechanics.spec.SemanticKey

import com.android.mechanics.spec.builder.MotionBuilderContext

import com.android.mechanics.spec.builder.fixedSpatialValueSpec

import com.android.mechanics.spec.builder.spatialMotionSpec

import com.android.mechanics.spec.with

import com.android.mechanics.spring.SpringParameters

import kotlin.math.abs

import kotlin.math.sign

import kotlinx.coroutines.Job

import kotlinx.coroutines.launch



/**

 * "Swipe to dismiss" effect that supports nested scrolling.

 *

 * TODO: Once b/413283893 is done, motionBuilderContext can be read internally via

 *   CompositionLocalConsumerModifierNode, instead of passing it.

 */

fun Modifier.overscrollToDismiss(

    motionBuilderContext: MotionBuilderContext,

    orientation: Orientation = Orientation.Horizontal,

    enabled: Boolean = true,

    onDismissed: () -> Unit,

) = this.then(OverscrollToDismissElement(motionBuilderContext, orientation, enabled, onDismissed))



private data class OverscrollToDismissElement(

    val motionBuilderContext: MotionBuilderContext,

    val orientation: Orientation,

    val enabled: Boolean,

    val onDismissed: () -> Unit,

) : ModifierNodeElement<OverscrollToDismissNode>() {

    override fun create(): OverscrollToDismissNode {

        return OverscrollToDismissNode(orientation, enabled, motionBuilderContext, onDismissed)

    }



    override fun update(node: OverscrollToDismissNode) {

        node.update(orientation, enabled, onDismissed)

    }



    override fun InspectorInfo.inspectableProperties() {

        name = "overscrollToDismiss"

        properties["enabled"] = enabled

        properties["orientation"] = orientation

    }

}



private class OverscrollToDismissNode(

    orientation: Orientation,

    enabled: Boolean,

    var motionBuilderContext: MotionBuilderContext,

    var onDismissed: () -> Unit,

) :

    DelegatingNode(),

    LayoutModifierNode,

    CompositionLocalConsumerModifierNode,

    ObserverModifierNode,

    NestedDraggable,

    NestedDraggable.Controller {



    // This implementation always tracks the gesture from 0..x, independent of whether the

    // overscroll is positive or negative. Thus, the output needs to be multiplied by this sign to

    // compute the actual value.

    private var overscrollSign: Float = 0f

    private val gestureContext =

        DistanceGestureContext(0f, InputDirection.Max, directionChangeSlop = 1f)



    private val motionValue =

        MotionValue(

            gestureContext::dragOffset,

            gestureContext,

            motionBuilderContext.fixedSpatialValueSpec(0f),

        )



    private var delegateNode =

        delegate(NestedDraggableRootNode(this, orientation, null, enabled, true))



    fun update(orientation: Orientation, enabled: Boolean, onDismissed: () -> Unit) {

        this.onDismissed = onDismissed

        delegateNode.update(this, orientation, null, enabled, true)

    }



    private var contentBoxWidth = 0

    private var motionValueJob: Job? = null



    override fun onAttach() {

        onObservedReadsChanged()

        motionValueJob = coroutineScope.launch { keepRunningUntilDismissed() }

    }



    override fun onObservedReadsChanged() {

        observeReads {

            gestureContext.directionChangeSlop = currentValueOf(LocalViewConfiguration).touchSlop

        }

    }



    override fun onDetach() {

        motionValueJob?.cancel()

    }



    override fun MeasureScope.measure(

        measurable: Measurable,

        constraints: Constraints,

    ): MeasureResult {

        val placeable = measurable.measure(constraints)

        contentBoxWidth = placeable.measuredWidth

        return layout(placeable.measuredWidth, placeable.measuredHeight) {

            placeable.place((motionValue.output * overscrollSign).toInt(), 0)

        }

    }



    override val autoStopNestedDrags: Boolean

        get() = true



    override fun onDragStarted(

        position: Offset,

        sign: Float,

        pointersDown: Int,

        pointerType: PointerType?,

    ): NestedDraggable.Controller {

        overscrollSign = sign

        gestureContext.reset(dragOffset = motionValue.output, direction = InputDirection.Max)

        motionValue.spec = motionBuilderContext.spatialMotionSpec { at(0f, MagneticDetach()) }

        return this

    }



    override fun shouldConsumeNestedPreScroll(sign: Float): Boolean {

        return motionValue[isDismissedState] ?: false

    }



    override fun onDrag(delta: Float): Float {

        val previousOffset = gestureContext.dragOffset

        val currentOffset = (gestureContext.dragOffset + delta * overscrollSign).coerceAtLeast(0f)

        gestureContext.dragOffset = currentOffset

        return (currentOffset - previousOffset) * overscrollSign

    }



    override suspend fun onDragStopped(velocity: Float, awaitFling: suspend () -> Unit): Float {

        val currentState = motionValue[AttachDetachState]

        with(requireDensity()) {

            val isFlingInOppositeDirection =

                abs(velocity) > AbortVelocity.toPx() && velocity.sign != overscrollSign



            val settleAttached =

                currentState == MagneticDetach.State.Attached ||

                    (currentState == MagneticDetach.State.Detached && isFlingInOppositeDirection)



            motionValue.spec =

                if (settleAttached) {

                    motionBuilderContext.fixedSpatialValueSpec(0f, SnapBackSpring)

                } else {

                    motionBuilderContext.fixedSpatialValueSpec(

                        contentBoxWidth.toFloat(),

                        SnapBackSpring,

                        listOf(isDismissedState with true),

                    )

                }

        }

        return velocity

    }



    private suspend fun keepRunningUntilDismissed() {

        val debuggerHandle = findMotionValueDebugger()?.register(motionValue)

        try {

            motionValue.keepRunningWhile {

                val isDismissed = get(isDismissedState) ?: false

                !(isDismissed && isStable)

            }

            onDismissed()

        } finally {

            debuggerHandle?.dispose()

        }

    }



    companion object {

        val isDismissedState = SemanticKey<Boolean>("isDismissed")

        val AbortVelocity = 100.dp // dp/s

        val SnapBackSpring = SpringParameters(stiffness = 550f, dampingRatio = 0.95f)

    }

}

packages/SystemUI/compose/core/tests/Android.bp

+3 −0
Original line number Diff line number Diff line
@@ -35,6 +35,8 @@ android_test { 


    static_libs: [

        "PlatformComposeCore",

        "PlatformMotionTestingCompose",

        "platform-test-annotations",



        "androidx.test.runner",

        "androidx.test.ext.junit",
@@ -45,6 +47,7 @@ android_test { 


        "truth",

    ],

    asset_dirs: ["goldens"],



    kotlincflags: ["-Xjvm-default=all"],

    use_resource_processor: true,

packages/SystemUI/compose/core/tests/AndroidManifest.xml

+1 −1
Original line number Diff line number Diff line
@@ -23,7 +23,7 @@ 


        <activity

            android:name="androidx.activity.ComponentActivity"

            android:theme="@android:style/Theme.DeviceDefault.DayNight"

            android:theme="@android:style/Theme.DeviceDefault.NoActionBar"

            android:exported="true"

            tools:replace="android:theme" />

    </application>