[MotionSpecBuilder] for the #MotionMechanics library (ac0a76d2) · Commits · e / os / android_frameworks_libs_systemui

mechanics/src/com/android/mechanics/spec/FluentSpecBuilder.kt

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		/*
		* Copyright (C) 2024 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.mechanics.spec

		import com.android.mechanics.spring.SpringParameters

		/**
		* Fluent builder for [DirectionalMotionSpec].
		*
		* This builder ensures correctness at compile-time, and simplifies the expression of the
		* input-to-output mapping.
		*
		* The [MotionSpec] is defined by specify interleaved [Mapping]s and [Breakpoint]s. [Breakpoint]s
		* must be specified in ascending order.
		*
		* NOTE: The returned fluent interfaces must only be used for chaining calls to build exactly one
		* [DirectionalMotionSpec], otherwise resulting behavior is undefined, since the builder is
		* internally mutated.
		*
		* @param defaultSpring spring to use for all breakpoints by default.
		* @param initialMapping the [Mapping] from [Breakpoint.minLimit] to the next [Breakpoint].
		* @see reverseBuilder to specify [Breakpoint]s in descending order.
		*/
		fun DirectionalMotionSpec.Companion.builder(
		defaultSpring: SpringParameters,
		initialMapping: Mapping = Mapping.Identity,
		): FluentSpecEndSegmentWithNextBreakpoint<DirectionalMotionSpec> {
		return FluentSpecBuilder(defaultSpring, InputDirection.Max) { it }
		.apply { mappings.add(initialMapping) }
		}

		/**
		* Fluent builder for [DirectionalMotionSpec], specifying breakpoints and mappings in reverse order.
		*
		* Variant of [DirectionalMotionSpec.Companion.builder], where [Breakpoint]s must be specified in
		* descending order. The resulting [DirectionalMotionSpec] will contain the breakpoints in
		* ascending order.
		*
		* @param defaultSpring spring to use for all breakpoints by default.
		* @param initialMapping the [Mapping] from [Breakpoint.maxLimit] to the next [Breakpoint].
		* @see DirectionalMotionSpec.Companion.builder for more documentation.
		*/
		fun DirectionalMotionSpec.Companion.reverseBuilder(
		defaultSpring: SpringParameters,
		initialMapping: Mapping = Mapping.Identity,
		): FluentSpecEndSegmentWithNextBreakpoint<DirectionalMotionSpec> {
		return FluentSpecBuilder(defaultSpring, InputDirection.Min) { it }
		.apply { mappings.add(initialMapping) }
		}

		/**
		* Fluent builder for a [MotionSpec], which uses the same spec in both directions.
		*
		* @param defaultSpring spring to use for all breakpoints by default.
		* @param initialMapping [Mapping] for the first segment
		* @param resetSpring the [MotionSpec.resetSpring].
		*/
		fun MotionSpec.Companion.builder(
		defaultSpring: SpringParameters,
		initialMapping: Mapping = Mapping.Identity,
		resetSpring: SpringParameters = defaultSpring,
		): FluentSpecEndSegmentWithNextBreakpoint<MotionSpec> {
		return FluentSpecBuilder(defaultSpring, InputDirection.Max) {
		MotionSpec(it, resetSpring = resetSpring)
		}
		.apply { mappings.add(initialMapping) }
		}

		/** Fluent-interface to end the current segment, by placing the next [Breakpoint]. */
		interface FluentSpecEndSegmentWithNextBreakpoint<R> {
		/**
		* Adds a new [Breakpoint] at the specified position.
		*
		* @param atPosition The position of the breakpoint, in the input domain of the [MotionValue].
		* @param key identifies the breakpoint in the [DirectionalMotionSpec]. Must be specified to
		* reference the breakpoint or segment.
		*/
		fun toBreakpoint(
		atPosition: Float,
		key: BreakpointKey = BreakpointKey(),
		): FluentSpecDefineBreakpointAndStartNextSegment<R>

		/** Completes the spec by placing the last, implicit [Breakpoint]. */
		fun complete(): R
		}

		/** Fluent-interface to define the [Breakpoint]'s properties and start to start the next segment. */
		interface FluentSpecDefineBreakpointAndStartNextSegment<R> {
		/**
		* Default spring parameters for breakpoint, as specified at creation time of the builder.
		*
		* Used as the default `spring` parameters.
		*/
		val defaultSpring: SpringParameters

		/**
		* Starts the next segment, using the specified mapping.
		*
		* @param mapping the mapping to use for the next segment.
		* @param spring the spring to animate this breakpoints discontinuity.
		* @param guarantee a guarantee by when the animation must be complete
		*/
		fun continueWith(
		mapping: Mapping,
		spring: SpringParameters = defaultSpring,
		guarantee: Guarantee = Guarantee.None,
		): FluentSpecEndSegmentWithNextBreakpoint<R>

		/**
		* Starts the next linear-mapped segment, by specifying the output [value] this breakpoint.
		*
		* @param value the output value the new mapping will produce at this breakpoints position.
		* @param spring the spring to animate this breakpoints discontinuity.
		* @param guarantee a guarantee by when the animation must be complete
		*/
		fun jumpTo(
		value: Float,
		spring: SpringParameters = defaultSpring,
		guarantee: Guarantee = Guarantee.None,
		): FluentSpecDefineLinearSegmentMapping<R>

		/**
		* Starts the next linear-mapped segment, by offsetting the output by [delta] from the incoming
		* mapping.
		*
		* @param delta the delta in output from the previous mapping's output.
		* @param spring the spring to animate this breakpoints discontinuity.
		* @param guarantee a guarantee by when the animation must be complete
		*/
		fun jumpBy(
		delta: Float,
		spring: SpringParameters = defaultSpring,
		guarantee: Guarantee = Guarantee.None,
		): FluentSpecDefineLinearSegmentMapping<R>

		/**
		* Completes the spec by using [mapping] between the this and the implicit sentinel breakpoint
		* at infinity.
		*
		* @param mapping the mapping to use for the final segment.
		* @param spring the spring to animate this breakpoints discontinuity.
		* @param guarantee a guarantee by when the animation must be complete
		*/
		fun completeWith(
		mapping: Mapping,
		spring: SpringParameters = defaultSpring,
		guarantee: Guarantee = Guarantee.None,
		): R
		}

		/** Fluent-interface to define a linear mapping between two breakpoints. */
		interface FluentSpecDefineLinearSegmentMapping<R> {
		/**
		* The linear-mapping will produce the specified [target] output at the next breakpoint
		* position.
		*
		* @param target the output value the new mapping will produce at the next breakpoint position.
		*/
		fun continueWithTargetValue(target: Float): FluentSpecEndSegmentWithNextBreakpoint<R>

		/**
		* Defines the slope for the linear mapping, as a fraction of the input value.
		*
		* @param fraction the multiplier applied to the input value..
		*/
		fun continueWithFractionalInput(fraction: Float): FluentSpecEndSegmentWithNextBreakpoint<R>

		/**
		* The linear-mapping will produce a constant value, as defined at the source breakpoint of this
		* segment.
		*/
		fun continueWithConstantValue(): FluentSpecEndSegmentWithNextBreakpoint<R>
		}

		/** Implements the fluent spec builder logic. */
		private class FluentSpecBuilder<R>(
		override val defaultSpring: SpringParameters,
		buildDirection: InputDirection = InputDirection.Max,
		private val toResult: (DirectionalMotionSpec) -> R,
		) :
		FluentSpecDefineLinearSegmentMapping<R>,
		FluentSpecDefineBreakpointAndStartNextSegment<R>,
		FluentSpecEndSegmentWithNextBreakpoint<R> {
		private val buildForward = buildDirection == InputDirection.Max

		val breakpoints = mutableListOf<Breakpoint>()
		val mappings = mutableListOf<Mapping>()

		var sourceValue: Float = Float.NaN
		var targetValue: Float = Float.NaN
		var fractionalMapping: Float = Float.NaN
		var breakpointPosition: Float = Float.NaN
		var breakpointKey: BreakpointKey? = null

		init {
		val initialBreakpoint = if (buildForward) Breakpoint.minLimit else Breakpoint.maxLimit
		breakpoints.add(initialBreakpoint)
		}

		// FluentSpecDefineLinearSegmentMapping

		override fun continueWithTargetValue(target: Float): FluentSpecEndSegmentWithNextBreakpoint<R> {
		check(sourceValue.isFinite())

		// memoize for FluentSpecEndSegmentWithNextBreakpoint
		targetValue = target

		return this
		}

		override fun continueWithFractionalInput(
		fraction: Float
		): FluentSpecEndSegmentWithNextBreakpoint<R> {
		check(sourceValue.isFinite())

		// memoize for FluentSpecEndSegmentWithNextBreakpoint
		fractionalMapping = fraction

		return this
		}

		override fun continueWithConstantValue(): FluentSpecEndSegmentWithNextBreakpoint<R> {
		check(sourceValue.isFinite())

		mappings.add(Mapping.Fixed(sourceValue))

		sourceValue = Float.NaN
		return this
		}

		// FluentSpecDefineBreakpointAndStartNextSegment implementation

		override fun jumpTo(
		value: Float,
		spring: SpringParameters,
		guarantee: Guarantee,
		): FluentSpecDefineLinearSegmentMapping<R> {
		check(sourceValue.isNaN())

		doAddBreakpoint(spring, guarantee)
		sourceValue = value

		return this
		}

		override fun jumpBy(
		delta: Float,
		spring: SpringParameters,
		guarantee: Guarantee,
		): FluentSpecDefineLinearSegmentMapping<R> {
		check(sourceValue.isNaN())

		val breakpoint = doAddBreakpoint(spring, guarantee)
		sourceValue = mappings.last().map(breakpoint.position) + delta

		return this
		}

		override fun continueWith(
		mapping: Mapping,
		spring: SpringParameters,
		guarantee: Guarantee,
		): FluentSpecEndSegmentWithNextBreakpoint<R> {
		check(sourceValue.isNaN())

		doAddBreakpoint(spring, guarantee)
		mappings.add(mapping)

		return this
		}

		override fun completeWith(mapping: Mapping, spring: SpringParameters, guarantee: Guarantee): R {
		check(sourceValue.isNaN())

		doAddBreakpoint(spring, guarantee)
		mappings.add(mapping)

		return complete()
		}

		// FluentSpecEndSegmentWithNextBreakpoint implementation

		override fun toBreakpoint(
		atPosition: Float,
		key: BreakpointKey,
		): FluentSpecDefineBreakpointAndStartNextSegment<R> {
		check(breakpointPosition.isNaN())
		check(breakpointKey == null)

		if (!targetValue.isNaN() \|\| !fractionalMapping.isNaN()) {
		check(!sourceValue.isNaN())

		val sourcePosition = breakpoints.last().position

		if (fractionalMapping.isNaN()) {
		val delta = targetValue - sourceValue
		fractionalMapping = delta / (atPosition - sourcePosition)
		} else {
		val delta = (atPosition - sourcePosition) * fractionalMapping
		targetValue = sourceValue + delta
		}

		val offset =
		if (buildForward) sourceValue - (sourcePosition * fractionalMapping)
		else targetValue - (atPosition * fractionalMapping)

		mappings.add(Mapping.Linear(fractionalMapping, offset))
		targetValue = Float.NaN
		sourceValue = Float.NaN
		fractionalMapping = Float.NaN
		}

		breakpointPosition = atPosition
		breakpointKey = key

		return this
		}

		override fun complete(): R {
		check(targetValue.isNaN()) { "cant specify target value for last segment" }

		if (!fractionalMapping.isNaN()) {
		check(!sourceValue.isNaN())

		val sourcePosition = breakpoints.last().position

		mappings.add(
		Mapping.Linear(
		fractionalMapping,
		sourceValue - (sourcePosition * fractionalMapping),
		)
		)
		}

		if (buildForward) {
		breakpoints.add(Breakpoint.maxLimit)
		} else {
		breakpoints.add(Breakpoint.minLimit)
		breakpoints.reverse()
		mappings.reverse()
		}

		return toResult(DirectionalMotionSpec(breakpoints.toList(), mappings.toList()))
		}

		private fun doAddBreakpoint(springSpec: SpringParameters, guarantee: Guarantee): Breakpoint {
		check(breakpointPosition.isFinite())
		return Breakpoint(checkNotNull(breakpointKey), breakpointPosition, springSpec, guarantee)
		.also {
		breakpoints.add(it)
		breakpointPosition = Float.NaN
		breakpointKey = null
		}
		}
		}

mechanics/src/com/android/mechanics/spec/MotionSpec.kt

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		@@ -94,6 +94,31 @@ data class DirectionalMotionSpec(val breakpoints: List<Breakpoint>, val mappings
		require(mappings.size == breakpoints.size - 1)
		}

		/**
		* Returns the index of the closest breakpoint where `Breakpoint.position <= position`.
		*
		* Guaranteed to be a valid index into [breakpoints], and guaranteed not to be the last element.
		*
		* @param position the position in the input domain.
		* @return Index into [breakpoints], guaranteed to be in range `0..breakpoints.size - 2`
		*/
		fun findBreakpointIndex(position: Float): Int {
		require(position.isFinite())
		val breakpointPosition = breakpoints.binarySearchBy(position) { it.position }

		val result =
		when {
		// position is between two anchors, return the min one.
		breakpointPosition < 0 -> -breakpointPosition - 2
		else -> breakpointPosition
		}

		check(result >= 0)
		check(result < breakpoints.size - 1)

		return result
		}

		companion object {
		/* Empty spec, the full input domain is mapped to output using [Mapping.identity]. */
		val Empty =

mechanics/tests/src/com/android/mechanics/spec/FluentSpecBuilderTest.kt

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		/*
		* Copyright (C) 2024 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.mechanics.spec

		import androidx.test.ext.junit.runners.AndroidJUnit4
		import com.android.mechanics.spring.SpringParameters
		import com.android.mechanics.testing.DirectionalMotionSpecSubject.Companion.assertThat
		import org.junit.Test
		import org.junit.runner.RunWith

		@RunWith(AndroidJUnit4::class)
		class FluentSpecBuilderTest {

		@Test
		fun directionalSpec_buildEmptySpec() {
		val result = DirectionalMotionSpec.builder(spring).complete()

		assertThat(result).breakpoints().isEmpty()
		assertThat(result).mappings().containsExactly(Mapping.Identity)
		}

		@Test
		fun directionalSpec_buildEmptySpec_inReverse() {
		val result = DirectionalMotionSpec.reverseBuilder(spring).complete()

		assertThat(result).breakpoints().isEmpty()
		assertThat(result).mappings().containsExactly(Mapping.Identity)
		}

		@Test
		fun motionSpec_sameSpecInBothDirections() {
		val result =
		MotionSpec.builder(spring, Mapping.Zero)
		.toBreakpoint(0f, b1)
		.continueWith(Mapping.One)
		.toBreakpoint(10f, b2)
		.completeWith(Mapping.Two)

		assertThat(result.maxDirection).isSameInstanceAs(result.minDirection)

		assertThat(result.minDirection).breakpoints().keys().containsExactly(b1, b2).inOrder()
		assertThat(result.minDirection)
		.mappings()
		.containsExactly(Mapping.Zero, Mapping.One, Mapping.Two)
		.inOrder()
		}

		@Test
		fun directionalSpec_addBreakpointsAndMappings() {
		val result =
		DirectionalMotionSpec.builder(spring, Mapping.Zero)
		.toBreakpoint(0f, b1)
		.continueWith(Mapping.One)
		.toBreakpoint(10f, b2)
		.completeWith(Mapping.Two)

		assertThat(result).breakpoints().keys().containsExactly(b1, b2).inOrder()
		assertThat(result).breakpoints().withKey(b1).isAt(0f)
		assertThat(result).breakpoints().withKey(b2).isAt(10f)
		assertThat(result)
		.mappings()
		.containsExactly(Mapping.Zero, Mapping.One, Mapping.Two)
		.inOrder()
		}

		@Test
		fun directionalSpec_addBreakpointsAndMappings_inReverse() {
		val result =
		DirectionalMotionSpec.reverseBuilder(spring, Mapping.Two)
		.toBreakpoint(10f, b2)
		.continueWith(Mapping.One)
		.toBreakpoint(0f, b1)
		.completeWith(Mapping.Zero)

		assertThat(result).breakpoints().keys().containsExactly(b1, b2).inOrder()
		assertThat(result).breakpoints().withKey(b1).isAt(0f)
		assertThat(result).breakpoints().withKey(b2).isAt(10f)
		assertThat(result)
		.mappings()
		.containsExactly(Mapping.Zero, Mapping.One, Mapping.Two)
		.inOrder()
		}

		@Test
		fun directionalSpec_mappingBuilder_setsDefaultSpring() {
		val result =
		DirectionalMotionSpec.builder(spring)
		.toBreakpoint(10f)
		.jumpTo(20f)
		.continueWithConstantValue()
		.complete()

		assertThat(result).breakpoints().atPosition(10f).spring().isEqualTo(spring)
		}

		@Test
		fun directionalSpec_mappingBuilder_canOverrideDefaultSpring() {
		val otherSpring = SpringParameters(stiffness = 10f, dampingRatio = 0.1f)
		val result =
		DirectionalMotionSpec.builder(spring)
		.toBreakpoint(10f)
		.jumpTo(20f, spring = otherSpring)
		.continueWithConstantValue()
		.complete()

		assertThat(result).breakpoints().atPosition(10f).spring().isEqualTo(otherSpring)
		}

		@Test
		fun directionalSpec_mappingBuilder_defaultsToNoGuarantee() {
		val result =
		DirectionalMotionSpec.builder(spring)
		.toBreakpoint(10f)
		.jumpTo(20f)
		.continueWithConstantValue()
		.complete()

		assertThat(result).breakpoints().atPosition(10f).guarantee().isEqualTo(Guarantee.None)
		}

		@Test
		fun directionalSpec_mappingBuilder_canSetGuarantee() {
		val guarantee = Guarantee.InputDelta(10f)
		val result =
		DirectionalMotionSpec.builder(spring)
		.toBreakpoint(10f)
		.jumpTo(20f, guarantee = guarantee)
		.continueWithConstantValue()
		.complete()

		assertThat(result).breakpoints().atPosition(10f).guarantee().isEqualTo(guarantee)
		}

		@Test
		fun directionalSpec_mappingBuilder_jumpTo_setsAbsoluteValue() {
		val result =
		DirectionalMotionSpec.builder(spring, Mapping.Fixed(99f))
		.toBreakpoint(10f)
		.jumpTo(20f)
		.continueWithConstantValue()
		.complete()

		assertThat(result).breakpoints().positions().containsExactly(10f)
		assertThat(result).mappings().atOrAfter(10f).isConstantValue(20f)
		}

		@Test
		fun directionalSpec_mappingBuilder_jumpBy_setsRelativeValue() {
		val result =
		DirectionalMotionSpec.builder(spring, Mapping.Linear(factor = 0.5f))
		.toBreakpoint(10f)
		.jumpBy(30f)
		.continueWithConstantValue()
		.complete()

		assertThat(result).breakpoints().positions().containsExactly(10f)
		assertThat(result).mappings().atOrAfter(10f).isConstantValue(35f)
		}

		@Test
		fun directionalSpec_mappingBuilder_continueWithConstantValue_usesSourceValue() {
		val result =
		DirectionalMotionSpec.builder(spring, Mapping.Linear(factor = 0.5f))
		.toBreakpoint(5f)
		.jumpBy(0f)
		.continueWithConstantValue()
		.complete()

		assertThat(result).mappings().atOrAfter(5f).isConstantValue(2.5f)
		}

		@Test
		fun directionalSpec_mappingBuilder_continueWithFractionalInput_matchesLinearMapping() {
		val result =
		DirectionalMotionSpec.builder(spring)
		.toBreakpoint(5f)
		.jumpTo(1f)
		.continueWithFractionalInput(fraction = .1f)
		.complete()

		assertThat(result)
		.mappings()
		.atOrAfter(5f)
		.matchesLinearMapping(in1 = 5f, out1 = 1f, in2 = 15f, out2 = 2f)
		}

		@Test
		fun directionalSpec_mappingBuilder_reverse_continueWithFractionalInput_matchesLinearMapping() {
		val result =
		DirectionalMotionSpec.reverseBuilder(spring)
		.toBreakpoint(15f)
		.jumpTo(2f)
		.continueWithFractionalInput(fraction = .1f)
		.complete()

		assertThat(result)
		.mappings()
		.atOrAfter(5f)
		.matchesLinearMapping(in1 = 5f, out1 = 1f, in2 = 15f, out2 = 2f)
		}

		@Test
		fun directionalSpec_mappingBuilder_continueWithTargetValue_matchesLinearMapping() {
		val result =
		DirectionalMotionSpec.builder(spring)
		.toBreakpoint(5f)
		.jumpTo(1f)
		.continueWithTargetValue(target = 20f)
		.toBreakpoint(30f)
		.completeWith(Mapping.Identity)

		assertThat(result)
		.mappings()
		.atOrAfter(5f)
		.matchesLinearMapping(in1 = 5f, out1 = 1f, in2 = 30f, out2 = 20f)
		}

		@Test
		fun directionalSpec_mappingBuilder_reverse_continueWithTargetValue_matchesLinearMapping() {
		val result =
		DirectionalMotionSpec.reverseBuilder(spring)
		.toBreakpoint(30f)
		.jumpTo(20f)
		.continueWithTargetValue(target = 1f)
		.toBreakpoint(5f)
		.completeWith(Mapping.Identity)

		assertThat(result)
		.mappings()
		.atOrAfter(5f)
		.matchesLinearMapping(in1 = 5f, out1 = 1f, in2 = 30f, out2 = 20f)
		}

		companion object {
		val spring = SpringParameters(stiffness = 100f, dampingRatio = 1f)
		val b1 = BreakpointKey("One")
		val b2 = BreakpointKey("Two")
		val b3 = BreakpointKey("Three")
		}
		}

mechanics/tests/src/com/android/mechanics/spec/MotionSpecTest.kt

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mechanics/tests/src/com/android/mechanics/testing/MotionSpecSubject.kt

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