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Commit 5fa13efc authored by Omar Miatello's avatar Omar Miatello
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Refactor: Rename `Empty` motion spec to `Identity` 1/2 

This patch is a pure refactoring that renames `MotionSpec.Empty` to
`MotionSpec.Identity` and `DirectionalMotionSpec.Empty` to
`DirectionalMotionSpec.Identity`.

Rationale: The term **`Empty`** was semantically ambiguous. It could be
misinterpreted as a spec with no effect or no content.

The new name, **`Identity`**, more accurately describes the spec's
function: a direct, one-to-one mapping where the output value is always
identical to the input value (an identity function, where `f(x) = x`).

This change improves the clarity and discoverability of the API without
altering any underlying behavior.

Changes:
* Renamed `MotionSpec.Empty` to `MotionSpec.Identity`.
* Renamed `DirectionalMotionSpec.Empty` to `DirectionalMotionSpec
.Identity`.
* Updated all call sites across the library, including tests,
benchmarks, and sample applications, to use the new name.

Test: Existing tests were updated to reflect the name change.
Bug: 402113641
Flag: com.android.systemui.scene_container
Change-Id: I885f0f800a86ea844f73e438080aeac98a39e814
parent 2b309391

mechanics/benchmark/tests/src/com/android/mechanics/benchmark/MotionValueBenchmark.kt

+4 −2
Original line number Diff line number Diff line
@@ -73,7 +73,7 @@ class MotionValueBenchmark { 
    private fun testData(

        gestureContext: DistanceGestureContext = DistanceGestureContext(0f, InputDirection.Max, 2f),

        input: Float = 0f,

        spec: MotionSpec = MotionSpec.Empty,

        spec: MotionSpec = MotionSpec.Identity,

    ): TestData {

        val inputState = mutableFloatStateOf(input)

        return TestData(
@@ -91,7 +91,9 @@ class MotionValueBenchmark { 
        val gestureContext = DistanceGestureContext(0f, InputDirection.Max, 2f)

        val input = { 0f }



        benchmarkRule.measureRepeated { MotionValue(input, gestureContext, { MotionSpec.Empty }) }

        benchmarkRule.measureRepeated {

            MotionValue(input, gestureContext, { MotionSpec.Identity })

        }

    }



    @Test

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

+4 −4
Original line number Diff line number Diff line
@@ -148,8 +148,8 @@ data class MotionSpec( 
         */

        private val DefaultResetSpring = SpringParameters(stiffness = 1400f, dampingRatio = 1f)



        /* Empty motion spec, the output is the same as the input. */

        val Empty = MotionSpec(DirectionalMotionSpec.Empty)

        /* Identity motion spec, the output is the same as the input. */

        val Identity = MotionSpec(DirectionalMotionSpec.Identity)



        /**

         * Placeholder to indicate that a [MotionSpec] cannot be supplied yet.
@@ -254,8 +254,8 @@ data class DirectionalMotionSpec( 
    override fun toString() = toDebugString()



    companion object {

        /* Empty spec, the full input domain is mapped to output using [Mapping.identity]. */

        val Empty =

        /* Identity spec, the full input domain is mapped to output using [Mapping.identity]. */

        val Identity =

            DirectionalMotionSpec(

                listOf(Breakpoint.minLimit, Breakpoint.maxLimit),

                listOf(Mapping.Identity),

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

+1 −1
Original line number Diff line number Diff line
@@ -49,7 +49,7 @@ class ViewMotionValue 
constructor(

    initialInput: Float,

    gestureContext: ViewGestureContext,

    initialSpec: MotionSpec = MotionSpec.Empty,

    initialSpec: MotionSpec = MotionSpec.Identity,

    label: String? = null,

    stableThreshold: Float = StableThresholdEffect,

) : DisposableHandle {

mechanics/tests/src/com/android/mechanics/MotionValueTest.kt

+12 −9
Original line number Diff line number Diff line
@@ -72,7 +72,7 @@ class MotionValueTest : MotionBuilderContext by FakeMotionSpecBuilderContext.Def 
    @Test

    fun emptySpec_outputMatchesInput_withoutAnimation() =

        motion.goldenTest(

            spec = MotionSpec.Empty,

            spec = MotionSpec.Identity,

            verifyTimeSeries = {

                // Output always matches the input

                assertThat(output).containsExactlyElementsIn(input).inOrder()
@@ -112,14 +112,14 @@ class MotionValueTest : MotionBuilderContext by FakeMotionSpecBuilderContext.Def 
            },

        ) {

            animateValueTo(10f, changePerFrame = 5f)

            spec = MotionSpec.Empty

            spec = MotionSpec.Identity

            animateValueTo(20f, changePerFrame = 5f)

        }



    @Test

    fun unspecifiedSpec_onAlreadyInitializedValue_throws() {

        assertFailsWith<IllegalArgumentException> {

            motion.goldenTest(spec = MotionSpec.Empty) {

            motion.goldenTest(spec = MotionSpec.Identity) {

                animateValueTo(10f, changePerFrame = 5f)

                spec = MotionSpec.InitiallyUndefined

                animateValueTo(20f, changePerFrame = 5f)
@@ -529,7 +529,7 @@ class MotionValueTest : MotionBuilderContext by FakeMotionSpecBuilderContext.Def 


    @Test

    fun semantics_returnsNullForUnknownKey() {

        val underTest = MotionValue({ 1f }, FakeGestureContext, { MotionSpec.Empty })

        val underTest = MotionValue({ 1f }, FakeGestureContext, { MotionSpec.Identity })



        val s1 = SemanticKey<String>("Foo")
@@ -575,7 +575,9 @@ class MotionValueTest : MotionBuilderContext by FakeMotionSpecBuilderContext.Def 
        motion.goldenTest(

            spec = specBuilder(Mapping.Zero) { fixedValue(breakpoint = 0.5f, value = 1f) },

            createDerived = { primary ->

                listOf(MotionValue.createDerived(primary, { MotionSpec.Empty }, label = "derived"))

                listOf(

                    MotionValue.createDerived(primary, { MotionSpec.Identity }, label = "derived")

                )

            },

            verifyTimeSeries = {

                // the output of the derived value must match the primary value
@@ -634,7 +636,7 @@ class MotionValueTest : MotionBuilderContext by FakeMotionSpecBuilderContext.Def 
    @Test

    fun nonFiniteNumbers_segmentChange_skipsAnimation() {

        motion.goldenTest(

            spec = MotionSpec.Empty,

            spec = MotionSpec.Identity,

            verifyTimeSeries = {

                // The mappings produce a non-finite number during a segment change.

                // The animation thereof is skipped to avoid poisoning the state with non-finite
@@ -684,7 +686,8 @@ class MotionValueTest : MotionBuilderContext by FakeMotionSpecBuilderContext.Def 


    @Test

    fun keepRunning_concurrentInvocationThrows() = runMonotonicClockTest {

        val underTest = MotionValue({ 1f }, FakeGestureContext, { MotionSpec.Empty }, label = "Foo")

        val underTest =

            MotionValue({ 1f }, FakeGestureContext, { MotionSpec.Identity }, label = "Foo")

        val realJob = launch { underTest.keepRunning() }

        testScheduler.runCurrent()
@@ -702,7 +705,7 @@ class MotionValueTest : MotionBuilderContext by FakeMotionSpecBuilderContext.Def 


    @Test

    fun debugInspector_sameInstance_whileInUse() {

        val underTest = MotionValue({ 1f }, FakeGestureContext, { MotionSpec.Empty })

        val underTest = MotionValue({ 1f }, FakeGestureContext, { MotionSpec.Identity })



        val originalInspector = underTest.debugInspector()

        assertThat(underTest.debugInspector()).isSameInstanceAs(originalInspector)
@@ -710,7 +713,7 @@ class MotionValueTest : MotionBuilderContext by FakeMotionSpecBuilderContext.Def 


    @Test

    fun debugInspector_newInstance_afterUnused() {

        val underTest = MotionValue({ 1f }, FakeGestureContext, { MotionSpec.Empty })

        val underTest = MotionValue({ 1f }, FakeGestureContext, { MotionSpec.Identity })



        val originalInspector = underTest.debugInspector()

        originalInspector.dispose()

mechanics/tests/src/com/android/mechanics/debug/MotionValueDebuggerTest.kt

+3 −3
Original line number Diff line number Diff line
@@ -52,7 +52,7 @@ class MotionValueDebuggerTest { 
            CompositionLocalProvider(LocalMotionValueDebugController provides debuggerState) {

                if (hasValue) {

                    val toDebug = remember {

                        MotionValue(input, gestureContext, { MotionSpec.Empty })

                        MotionValue(input, gestureContext, { MotionSpec.Identity })

                    }

                    Box(modifier = Modifier.debugMotionValue(toDebug))

                }
@@ -76,7 +76,7 @@ class MotionValueDebuggerTest { 
            CompositionLocalProvider(LocalMotionValueDebugController provides debuggerState) {

                if (hasValue) {

                    val toDebug = remember {

                        MotionValue(input, gestureContext, { MotionSpec.Empty })

                        MotionValue(input, gestureContext, { MotionSpec.Identity })

                    }

                    Box(modifier = Modifier.debugMotionValue(toDebug))

                }
@@ -93,7 +93,7 @@ class MotionValueDebuggerTest { 
    @Test

    fun debugMotionValue_noDebugger_isNoOp() {

        rule.setContent {

            val toDebug = remember { MotionValue(input, gestureContext, { MotionSpec.Empty }) }

            val toDebug = remember { MotionValue(input, gestureContext, { MotionSpec.Identity }) }

            Box(modifier = Modifier.debugMotionValue(toDebug))

        }

    }