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Commit 4687fafa authored by Mike Schneider's avatar Mike Schneider
Browse files

Fix wrong initial velocity while animating a discontinuity. 

During the investigation, we also noticed that the
`DiscontinuityAnimation.targetValue` is redundant and can be removed.
The change in computation produces tiny rounding errors, requiring a
golden update.

Test: Unit tests
Flag: com.android.systemui.scene_container
Bug: 409726626
Change-Id: I1940d02ae632d9c6a85c257188b91a6045c97441
parent 783e666b

mechanics/src/com/android/mechanics/MotionValue.kt

+2 −8
Original line number Diff line number Diff line
@@ -359,14 +359,8 @@ private class ObservableComputations( 
                // same time not already applying the `last*` state (as this would cause a

                // re-computation if the current state is being read before the next frame).

                if (isAnimatingUninterrupted) {

                    val currentDirectMapped = currentDirectMapped

                    val lastDirectMapped =

                        lastSegment.mapping.map(lastInput) - lastAnimation.targetValue



                    val frameDuration =

                        (currentAnimationTimeNanos - lastFrameTimeNanos) / 1_000_000_000.0

                    val staticDelta = (currentDirectMapped - lastDirectMapped)

                    directMappedVelocity = (staticDelta / frameDuration).toFloat()

                    directMappedVelocity =

                        computeDirectMappedVelocity(currentAnimationTimeNanos - lastFrameTimeNanos)

                } else {

                    directMappedVelocity = 0f

                }

mechanics/src/com/android/mechanics/debug/DebugInspector.kt

+2 −5
Original line number Diff line number Diff line
@@ -76,10 +76,10 @@ internal constructor( 
        get() = segment.key



    val output: Float

        get() = currentDirectMapped + (animation.targetValue + springState.displacement)

        get() = segment.mapping.map(input) + springState.displacement



    val outputTarget: Float

        get() = currentDirectMapped + animation.targetValue

        get() = segment.mapping.map(input)



    fun <T> semantic(semanticKey: SemanticKey<T>): T? {

        return segment.semantic(semanticKey)
@@ -87,7 +87,4 @@ internal constructor( 


    val semantics: List<SemanticValue<*>>

        get() = with(segment) { spec.semantics(key) }



    private val currentDirectMapped: Float

        get() = segment.mapping.map(input) - animation.targetValue

}

mechanics/src/com/android/mechanics/impl/Computations.kt

+25 −27
Original line number Diff line number Diff line
@@ -125,41 +125,24 @@ internal abstract class Computations : CurrentFrameInput, LastFrameState, Static 


    val isSameSegmentAndAtRest: Boolean

        get() =

            lastAnimation.isAtRest &&

            lastSpringState == SpringState.AtRest &&

                lastSegment.spec == spec &&

                lastSegment.isValidForInput(currentInput, currentDirection)



    val currentDirectMapped: Float

        get() =

            if (isSameSegmentAndAtRest) {

                lastSegment.mapping.map(currentInput)

            } else {

                val values = currentComputedValues

                values.segment.mapping.map(currentInput) - values.animation.targetValue

            }



    private val currentAnimatedDelta: Float

        get() =

            if (isSameSegmentAndAtRest) {

                0f

            } else {

                currentComputedValues.animation.targetValue + currentSpringState.displacement

            }



    val output: Float

        get() =

            if (isSameSegmentAndAtRest) {

                lastSegment.mapping.map(currentInput)

            } else {

                currentDirectMapped + currentAnimatedDelta

                outputTarget + currentSpringState.displacement

            }



    val outputTarget: Float

        get() =

            if (isSameSegmentAndAtRest) {

                lastAnimation.targetValue

                lastSegment.mapping.map(currentInput)

            } else {

                currentDirectMapped + currentComputedValues.animation.targetValue

                currentComputedValues.segment.mapping.map(currentInput)

            }



    val isStable: Boolean
@@ -176,6 +159,24 @@ internal abstract class Computations : CurrentFrameInput, LastFrameState, Static 
        }

    }



    fun computeDirectMappedVelocity(frameDurationNanos: Long): Float {

        val directMappedDelta =

            if (

                lastSegment.spec == spec &&

                    lastSegment.isValidForInput(currentInput, currentDirection)

            ) {

                lastSegment.mapping.map(currentInput) - lastSegment.mapping.map(lastInput)

            } else {

                val springChange = currentSpringState.displacement - lastSpringState.displacement



                currentComputedValues.segment.mapping.map(currentInput) -

                    lastSegment.mapping.map(lastInput) + springChange

            }



        val frameDuration = frameDurationNanos / 1_000_000_000.0

        return (directMappedDelta / frameDuration).toFloat()

    }



    /**

     * The current segment, which defines the [Mapping] function used to transform the input to the

     * output.
@@ -357,9 +358,9 @@ internal abstract class Computations : CurrentFrameInput, LastFrameState, Static 
    ): DiscontinuityAnimation {

        return when (segmentChange) {

            SegmentChangeType.Same -> {

                if (lastAnimation.isAtRest) {

                if (lastSpringState == SpringState.AtRest) {

                    // Nothing to update if no animation is ongoing

                    lastAnimation

                    DiscontinuityAnimation.None

                } else if (lastGuaranteeState == guarantee) {

                    // Nothing to update if the spring must not be tightened.

                    lastAnimation
@@ -409,7 +410,6 @@ internal abstract class Computations : CurrentFrameInput, LastFrameState, Static 


                    val newTarget = delta - lastSpringState.displacement

                    DiscontinuityAnimation(

                        newTarget,

                        SpringState(-newTarget, lastSpringState.velocity + directMappedVelocity),

                        springParameters,

                        lastFrameTimeNanos,
@@ -434,7 +434,6 @@ internal abstract class Computations : CurrentFrameInput, LastFrameState, Static 
                    var lastAnimationTime = lastFrameTimeNanos

                    var guaranteeState = lastGuaranteeState

                    var springState = lastSpringState

                    var springTarget = lastAnimation.targetValue

                    var springParameters = lastAnimation.springParameters



                    var segmentIndex = sourceIndex
@@ -507,7 +506,6 @@ internal abstract class Computations : CurrentFrameInput, LastFrameState, Static 
                        }



                        if (deltaIsFinite) {

                            springTarget += delta

                            springState = springState.nudge(displacementDelta = -delta)

                        }

                        segmentIndex += directionOffset
@@ -536,7 +534,7 @@ internal abstract class Computations : CurrentFrameInput, LastFrameState, Static 


                    val tightened = guarantee.updatedSpringParameters(segment.entryBreakpoint)



                    DiscontinuityAnimation(springTarget, springState, tightened, lastAnimationTime)

                    DiscontinuityAnimation(springState, tightened, lastAnimationTime)

                }

            }

        }

mechanics/src/com/android/mechanics/impl/DiscontinuityAnimation.kt

+0 −2
Original line number Diff line number Diff line
@@ -26,7 +26,6 @@ import com.android.mechanics.spring.SpringState 
 * output values for the same input.

 */

internal data class DiscontinuityAnimation(

    val targetValue: Float,

    val springStartState: SpringState,

    val springParameters: SpringParameters,

    val springStartTimeNanos: Long,
@@ -37,7 +36,6 @@ internal data class DiscontinuityAnimation( 
    companion object {

        val None =

            DiscontinuityAnimation(

                targetValue = 0f,

                springStartState = SpringState.AtRest,

                springParameters = SpringParameters.Snap,

                springStartTimeNanos = 0L,

mechanics/src/com/android/mechanics/view/ViewMotionValue.kt

+2 −6
Original line number Diff line number Diff line
@@ -290,12 +290,8 @@ private class ImperativeComputations( 


        // Prepare last* state

        if (isAnimatingUninterrupted) {

            val currentDirectMapped = currentDirectMapped

            val lastDirectMapped = lastSegment.mapping.map(lastInput) - lastAnimation.targetValue



            val frameDuration = (currentAnimationTimeNanos - lastFrameTimeNanos) / 1_000_000_000.0

            val staticDelta = (currentDirectMapped - lastDirectMapped)

            directMappedVelocity = (staticDelta / frameDuration).toFloat()

            directMappedVelocity =

                computeDirectMappedVelocity(currentAnimationTimeNanos - lastFrameTimeNanos)

        } else {

            directMappedVelocity = 0f

        }