Make UserActionResult a class instead of interface (1/2)

In ag/25970777, we introduced a new UserActionResult interface to allow
the user to specify the distance of a user action, as well as changing
the transition key of a user action. This CL made the UserActionResult
an interface that was implemented by SceneKey, so that the old and most
common syntax userActions=mapOf(Swipe.Up to Scenes.Foo) still compiles.

After some discussions with other peers, it came out the the
UserActionResult being an interface implemented by SceneKey was
confusing. This CL makes the UserActionResult a class and instead
overloads the infix `to` function in UserAction so that
`UserAction to SceneKey` returns a Pair<UserAction, UserActionResult>
instead of a Pair<UserAction, SceneKey>, still allowing the shorter and
most common syntax to define user actions.

Bug: 321932826
Test: PlatformComposeSceneTransitionLayoutTests
Flag: N/A
Change-Id: I99566aee81bdd14022e0eda2af9144525d77da49

4 files changed, 24 insertions, 67 deletions

diff --git a/packages/SystemUI/compose/features/src/com/android/systemui/scene/ui/composable/SceneContainer.kt b/packages/SystemUI/compose/features/src/com/android/systemui/scene/ui/composable/SceneContainer.kt
index 9f9e1f5bb56a..da1b417ae190 100644
--- a/packages/SystemUI/compose/features/src/com/android/systemui/scene/ui/composable/SceneContainer.kt
+++ b/packages/SystemUI/compose/features/src/com/android/systemui/scene/ui/composable/SceneContainer.kt
@@ -40,6 +40,7 @@ import com.android.compose.animation.scene.SceneTransitionLayout
 import com.android.compose.animation.scene.Swipe
 import com.android.compose.animation.scene.SwipeDirection
 import com.android.compose.animation.scene.UserAction as SceneTransitionUserAction
+import com.android.compose.animation.scene.UserActionResult
 import com.android.compose.animation.scene.observableTransitionState
 import com.android.compose.animation.scene.updateSceneTransitionLayoutState
 import com.android.systemui.ribbon.ui.composable.BottomRightCornerRibbon
@@ -168,7 +169,7 @@ private fun SceneTransitionObservableTransitionState.toModel(): ObservableTransi
 private fun toTransitionModels(
     userAction: UserAction,
     sceneModel: SceneModel,
-): Pair<SceneTransitionUserAction, SceneTransitionSceneKey> {
+): Pair<SceneTransitionUserAction, UserActionResult> {
     return userAction.toTransitionUserAction() to sceneModel.key.toTransitionSceneKey()
 }
 
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Key.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Key.kt
index 2596d4a34b6f..97703992cbf6 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Key.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Key.kt
@@ -44,7 +44,7 @@ sealed class Key(val debugName: String, val identity: Any) {
 class SceneKey(
     debugName: String,
     identity: Any = Object(),
-) : Key(debugName, identity), UserActionResult {
+) : Key(debugName, identity) {
     @VisibleForTesting
     // TODO(b/240432457): Make internal once PlatformComposeSceneTransitionLayoutTestsUtils can
     // access internal members.
@@ -53,11 +53,6 @@ class SceneKey(
     /** The unique [ElementKey] identifying this scene's root element. */
     val rootElementKey = ElementKey(debugName, identity)
 
-    // Implementation of [UserActionResult].
-    override val toScene: SceneKey = this
-    override val transitionKey: TransitionKey? = null
-    override val distance: UserActionDistance? = null
-
     override fun toString(): String {
         return "SceneKey(debugName=$debugName)"
     }
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt
index d904c8b770bf..e1f8a0959f6f 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt
@@ -332,7 +332,11 @@ interface ElementBoxScope {
 @Stable @ElementDsl interface MovableElementContentScope : BaseSceneScope, ElementBoxScope
 
 /** An action performed by the user. */
-sealed interface UserAction
+sealed interface UserAction {
+    infix fun to(scene: SceneKey): Pair<UserAction, UserActionResult> {
+        return this to UserActionResult(toScene = scene)
+    }
+}
 
 /** The user navigated back, either using a gesture or by triggering a KEYCODE_BACK event. */
 data object Back : UserAction
@@ -385,65 +389,26 @@ interface SwipeSourceDetector {
     ): SwipeSource?
 }
 
-/**
- * The result of performing a [UserAction].
- *
- * Note: [UserActionResult] is implemented by [SceneKey], so you can also use scene keys directly
- * when defining your [UserActionResult]s.
- *
- * ```
- * SceneTransitionLayout(...) {
- *     scene(
- *         Scenes.Foo,
- *         userActions =
- *             mapOf(
- *                 Swipe.Right to Scene.Bar,
- *                 Swipe.Down to Scene.Doe,
- *             )
- *         )
- *     ) { ... }
- * }
- * ```
- */
-interface UserActionResult {
+/** The result of performing a [UserAction]. */
+class UserActionResult(
     /** The scene we should be transitioning to during the [UserAction]. */
-    val toScene: SceneKey
-
-    /** The key of the transition that should be used. */
-    val transitionKey: TransitionKey?
+    val toScene: SceneKey,
 
     /**
      * The distance the action takes to animate from 0% to 100%.
      *
      * If `null`, a default distance will be used that depends on the [UserAction] performed.
      */
-    val distance: UserActionDistance?
-}
-
-/** Create a [UserActionResult] to [toScene] with the given [distance] and [transitionKey]. */
-fun UserActionResult(
-    toScene: SceneKey,
-    distance: UserActionDistance? = null,
-    transitionKey: TransitionKey? = null,
-): UserActionResult {
-    return object : UserActionResult {
-        override val toScene: SceneKey = toScene
-        override val transitionKey: TransitionKey? = transitionKey
-        override val distance: UserActionDistance? = distance
-    }
-}
+    val distance: UserActionDistance? = null,
 
-/** Create a [UserActionResult] to [toScene] with the given fixed [distance] and [transitionKey]. */
-fun UserActionResult(
-    toScene: SceneKey,
-    distance: Dp,
-    transitionKey: TransitionKey? = null,
-): UserActionResult {
-    return UserActionResult(
-        toScene = toScene,
-        distance = FixedDistance(distance),
-        transitionKey = transitionKey,
-    )
+    /** The key of the transition that should be used. */
+    val transitionKey: TransitionKey? = null,
+) {
+    constructor(
+        toScene: SceneKey,
+        distance: Dp,
+        transitionKey: TransitionKey? = null,
+    ) : this(toScene, FixedDistance(distance), transitionKey)
 }
 
 interface UserActionDistance {
diff --git a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt
index 2dc94a405ae3..dacbdb484d0c 100644
--- a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt
+++ b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt
@@ -54,12 +54,8 @@ class SceneGestureHandlerTest {
         private val layoutState =
             MutableSceneTransitionLayoutStateImpl(SceneA, EmptyTestTransitions)
 
-        val mutableUserActionsA: MutableMap<UserAction, SceneKey> =
-            mutableMapOf(Swipe.Up to SceneB, Swipe.Down to SceneC)
-
-        val mutableUserActionsB: MutableMap<UserAction, SceneKey> =
-            mutableMapOf(Swipe.Up to SceneC, Swipe.Down to SceneA)
-
+        val mutableUserActionsA = mutableMapOf(Swipe.Up to SceneB, Swipe.Down to SceneC)
+        val mutableUserActionsB = mutableMapOf(Swipe.Up to SceneC, Swipe.Down to SceneA)
         private val scenesBuilder: SceneTransitionLayoutScope.() -> Unit = {
             scene(
                 key = SceneA,
@@ -507,7 +503,7 @@ class SceneGestureHandlerTest {
         onDragStarted(overSlop = up(fractionOfScreen = 0.1f))
         assertTransition(fromScene = SceneA, toScene = SceneB, progress = 0.1f)
 
-        mutableUserActionsA[Swipe.Up] = SceneC
+        mutableUserActionsA[Swipe.Up] = UserActionResult(SceneC)
         onDelta(pixels = up(fractionOfScreen = 0.1f))
         // target stays B even though UserActions changed
         assertTransition(fromScene = SceneA, toScene = SceneB, progress = 0.2f)
@@ -524,7 +520,7 @@ class SceneGestureHandlerTest {
         onDragStarted(overSlop = up(fractionOfScreen = 0.1f))
         assertTransition(fromScene = SceneA, toScene = SceneB, progress = 0.1f)
 
-        mutableUserActionsA[Swipe.Up] = SceneC
+        mutableUserActionsA[Swipe.Up] = UserActionResult(SceneC)
         onDelta(pixels = up(fractionOfScreen = 0.1f))
         onDragStopped(velocity = down(fractionOfScreen = 0.1f))