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Commit 30211835 authored by Omar Miatello's avatar Omar Miatello
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feat(MM): Make MotionSpec declarative and state-driven (2/3) 

This change refactors `MotionValue` to make its `MotionSpec` (animation
physics) derived from a reactive lambda, replacing the previous
imperative approach.

Previously, `MotionValue` had a mutable `spec` property that consumers
would update directly. This required imperative logic within consumers
(`motionValue.spec = ...`) which did not align well with Compose's
declarative, state-driven architecture.

The `MotionValue` constructor now accepts a `spec: () -> MotionSpec`
lambda. The value now automatically reacts to changes in any state read
within this lambda, making its behavior inherently declarative.

Test: Tested on the previous MotionValueTests
Bug: 428886057
Flag: com.android.systemui.scene_container
Change-Id: I8f1b29da698d6599edcd61d36108f005d21e706e
parent b9eba49b

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

+32 −14
Original line number Original line Diff line number Diff line
@@ -17,6 +17,10 @@ 
package com.android.compose.gesture

package com.android.compose.gesture





import androidx.compose.foundation.gestures.Orientation

import androidx.compose.foundation.gestures.Orientation

import androidx.compose.runtime.derivedStateOf

import androidx.compose.runtime.getValue

import androidx.compose.runtime.mutableStateOf

import androidx.compose.runtime.setValue

import androidx.compose.ui.Modifier

import androidx.compose.ui.Modifier

import androidx.compose.ui.geometry.Offset

import androidx.compose.ui.geometry.Offset

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

import androidx.compose.ui.input.pointer.PointerType
@@ -106,11 +110,34 @@ private class OverscrollToDismissNode( 
    private val gestureContext =

    private val gestureContext =

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

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





    private var dragState: DragState by mutableStateOf(DragState.Idle)



    enum class DragState {

        Idle,

        Dragging,

        Dismissed,

    }



    private val spec = derivedStateOf {

        with(motionBuilderContext) {

            when (dragState) {

                DragState.Idle -> fixedSpatialValueSpec(0f, SnapBackSpring)

                DragState.Dragging -> spatialMotionSpec { after(0f, MagneticDetach()) }

                DragState.Dismissed ->

                    fixedSpatialValueSpec(

                        contentBoxWidth.toFloat(),

                        SnapBackSpring,

                        listOf(isDismissedState with true),

                    )

            }

        }

    }



    private val motionValue =

    private val motionValue =

        MotionValue(

        MotionValue(

            gestureContext::dragOffset,

            input = { gestureContext.dragOffset },

            gestureContext,

            gestureContext = gestureContext,

            motionBuilderContext.fixedSpatialValueSpec(0f),

            spec = spec::value,

        )

        )





    private var delegateNode =

    private var delegateNode =
@@ -161,7 +188,7 @@ private class OverscrollToDismissNode( 
    ): NestedDraggable.Controller {

    ): NestedDraggable.Controller {

        overscrollSign = sign

        overscrollSign = sign

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

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

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

        dragState = DragState.Dragging





        return this

        return this

    }

    }
@@ -187,16 +214,7 @@ private class OverscrollToDismissNode( 
                currentState == MagneticDetach.State.Attached ||

                currentState == MagneticDetach.State.Attached ||

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

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





            motionValue.spec =

            dragState = if (settleAttached) DragState.Idle else DragState.Dismissed

                if (settleAttached) {

                    motionBuilderContext.fixedSpatialValueSpec(0f, SnapBackSpring)

                } else {

                    motionBuilderContext.fixedSpatialValueSpec(

                        contentBoxWidth.toFloat(),

                        SnapBackSpring,

                        listOf(isDismissedState with true),

                    )

                }

        }

        }

        return velocity

        return velocity

    }

    }

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/mechanics/TransitionScopedMechanicsAdapter.kt

+21 −9
Original line number Original line Diff line number Diff line
@@ -17,6 +17,7 @@ 
package com.android.compose.animation.scene.mechanics

package com.android.compose.animation.scene.mechanics





import androidx.annotation.VisibleForTesting

import androidx.annotation.VisibleForTesting

import androidx.compose.runtime.derivedStateOf

import androidx.compose.runtime.mutableFloatStateOf

import androidx.compose.runtime.mutableFloatStateOf

import com.android.compose.animation.scene.ContentKey

import com.android.compose.animation.scene.ContentKey

import com.android.compose.animation.scene.ElementKey

import com.android.compose.animation.scene.ElementKey
@@ -51,11 +52,13 @@ internal class TransitionScopedMechanicsAdapter( 
    private val computeInput: MotionValueInput = { progress, _, _ -> progress },

    private val computeInput: MotionValueInput = { progress, _, _ -> progress },

    private val stableThreshold: Float = MotionValue.StableThresholdEffect,

    private val stableThreshold: Float = MotionValue.StableThresholdEffect,

    private val label: String? = null,

    private val label: String? = null,

    private val createSpec: SpecFactory,

    private val getSpec: SpecFactory,

) {

) {





    private val input = mutableFloatStateOf(0f)

    private val input = mutableFloatStateOf(0f)

    private var motionValue: MotionValue? = null

    private var motionValue: MotionValue? = null

    private var transformationContent: ContentKey? = null

    private var transformationElement: ElementKey? = null





    fun PropertyTransformationScope.update(

    fun PropertyTransformationScope.update(

        content: ContentKey,

        content: ContentKey,
@@ -68,23 +71,32 @@ internal class TransitionScopedMechanicsAdapter( 
        var motionValue = motionValue

        var motionValue = motionValue





        if (motionValue == null) {

        if (motionValue == null) {

            transformationContent = content

            transformationElement = element

            motionValue =

            motionValue =

                MotionValue(

                MotionValue(

                    input::floatValue,

                    input = { input.floatValue },

                    gestureContext =

                        transition.gestureContext

                        transition.gestureContext

                            ?: ProvidedGestureContext(

                            ?: ProvidedGestureContext(

                                0f,

                                0f,

                                appearDirection(content, element, transition),

                                appearDirection(content, element, transition),

                            ),

                            ),

                    createSpec(content, element),

                    spec = derivedStateOf { getSpec(content, element) }::value,

                    stableThreshold = stableThreshold,

                    label = label,

                    label = label,

                    stableThreshold = stableThreshold,

                )

                )



            this@TransitionScopedMechanicsAdapter.motionValue = motionValue

            this@TransitionScopedMechanicsAdapter.motionValue = motionValue





            transitionScope.launch {

            transitionScope.launch {

                motionValue.keepRunningWhile { !transition.isProgressStable || !isStable }

                motionValue.keepRunningWhile { !transition.isProgressStable || !isStable }

            }

            }

        } else {

            check(content == transformationContent && element == transformationElement) {

                "update received ($content, $element), " +

                    "instead of ($transformationContent, $transformationElement)"

            }

        }

        }





        return motionValue.output

        return motionValue.output

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

+1 −1
Original line number Original line Diff line number Diff line
@@ -447,7 +447,7 @@ class TransitionScopedMechanicsAdapterTest { 
        override val property = PropertyTransformation.Property.Offset

        override val property = PropertyTransformation.Property.Offset





        val motionValue =

        val motionValue =

            TransitionScopedMechanicsAdapter(createSpec = specFactory, stableThreshold = 1f)

            TransitionScopedMechanicsAdapter(getSpec = specFactory, stableThreshold = 1f)





        override fun PropertyTransformationScope.transform(

        override fun PropertyTransformationScope.transform(

            content: ContentKey,

            content: ContentKey,