Reapply "Don't install a pointer input when there are no user actions"

This is a reland of ag/29669127, which was broken (and reverted in
ag/29690066) because SwipeToSceneNode was not properly handling the
update of its draggableHandler.

This reland fixes the issue by introducing a SwipeToSceneRootNode, which
recreates a new delegate node whenever draggableHandler has changed.
This approach was suggested by the Compose team in
http://shortn/_MUgPp4TRmY. A test covering this case was added in
SwipeToSceneTest.swipeToSceneSupportsUpdates().

Bug: 370913106
Test: atest SwipeToSceneTest
Flag: com.android.systemui.scene_container
Change-Id: Ifc1b88a813b6de153028db64aac6cd1103c94a66
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/MultiPointerDraggable.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/MultiPointerDraggable.kt
index dc3135d..aa70a0c 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/MultiPointerDraggable.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/MultiPointerDraggable.kt
@@ -42,10 +42,8 @@
 import androidx.compose.ui.node.CompositionLocalConsumerModifierNode
 import androidx.compose.ui.node.DelegatingNode
 import androidx.compose.ui.node.ModifierNodeElement
-import androidx.compose.ui.node.ObserverModifierNode
 import androidx.compose.ui.node.PointerInputModifierNode
 import androidx.compose.ui.node.currentValueOf
-import androidx.compose.ui.node.observeReads
 import androidx.compose.ui.platform.LocalViewConfiguration
 import androidx.compose.ui.unit.IntSize
 import androidx.compose.ui.unit.Velocity
@@ -79,7 +77,6 @@
 @Stable
 internal fun Modifier.multiPointerDraggable(
     orientation: Orientation,
-    enabled: () -> Boolean,
     startDragImmediately: (startedPosition: Offset) -> Boolean,
     onDragStarted: (startedPosition: Offset, overSlop: Float, pointersDown: Int) -> DragController,
     onFirstPointerDown: () -> Unit = {},
@@ -89,7 +86,6 @@
     this.then(
         MultiPointerDraggableElement(
             orientation,
-            enabled,
             startDragImmediately,
             onDragStarted,
             onFirstPointerDown,
@@ -100,7 +96,6 @@
 
 private data class MultiPointerDraggableElement(
     private val orientation: Orientation,
-    private val enabled: () -> Boolean,
     private val startDragImmediately: (startedPosition: Offset) -> Boolean,
     private val onDragStarted:
         (startedPosition: Offset, overSlop: Float, pointersDown: Int) -> DragController,
@@ -111,7 +106,6 @@
     override fun create(): MultiPointerDraggableNode =
         MultiPointerDraggableNode(
             orientation = orientation,
-            enabled = enabled,
             startDragImmediately = startDragImmediately,
             onDragStarted = onDragStarted,
             onFirstPointerDown = onFirstPointerDown,
@@ -121,7 +115,6 @@
 
     override fun update(node: MultiPointerDraggableNode) {
         node.orientation = orientation
-        node.enabled = enabled
         node.startDragImmediately = startDragImmediately
         node.onDragStarted = onDragStarted
         node.onFirstPointerDown = onFirstPointerDown
@@ -131,27 +124,23 @@
 
 internal class MultiPointerDraggableNode(
     orientation: Orientation,
-    enabled: () -> Boolean,
     var startDragImmediately: (startedPosition: Offset) -> Boolean,
     var onDragStarted:
         (startedPosition: Offset, overSlop: Float, pointersDown: Int) -> DragController,
     var onFirstPointerDown: () -> Unit,
-    var swipeDetector: SwipeDetector = DefaultSwipeDetector,
+    swipeDetector: SwipeDetector = DefaultSwipeDetector,
     private val dispatcher: NestedScrollDispatcher,
 ) :
     DelegatingNode(),
     PointerInputModifierNode,
     CompositionLocalConsumerModifierNode,
-    ObserverModifierNode,
     SpaceVectorConverter {
     private val pointerTracker = delegate(SuspendingPointerInputModifierNode { pointerTracker() })
     private val pointerInput = delegate(SuspendingPointerInputModifierNode { pointerInput() })
     private val velocityTracker = VelocityTracker()
-    private var previousEnabled: Boolean = false
 
-    var enabled: () -> Boolean = enabled
+    var swipeDetector: SwipeDetector = swipeDetector
         set(value) {
-            // Reset the pointer input whenever enabled changed.
             if (value != field) {
                 field = value
                 pointerInput.resetPointerInputHandler()
@@ -178,21 +167,6 @@
             }
         }
 
-    override fun onAttach() {
-        previousEnabled = enabled()
-        onObservedReadsChanged()
-    }
-
-    override fun onObservedReadsChanged() {
-        observeReads {
-            val newEnabled = enabled()
-            if (newEnabled != previousEnabled) {
-                pointerInput.resetPointerInputHandler()
-            }
-            previousEnabled = newEnabled
-        }
-    }
-
     override fun onCancelPointerInput() {
         pointerTracker.onCancelPointerInput()
         pointerInput.onCancelPointerInput()
@@ -254,9 +228,7 @@
                         velocityTracker.resetTracking()
                         velocityTracker.addPointerInputChange(firstPointerDown)
                         startedPosition = firstPointerDown.position
-                        if (enabled()) {
-                            onFirstPointerDown()
-                        }
+                        onFirstPointerDown()
                     }
 
                     // Changes with at least one pointer
@@ -295,10 +267,6 @@
     }
 
     private suspend fun PointerInputScope.pointerInput() {
-        if (!enabled()) {
-            return
-        }
-
         val currentContext = currentCoroutineContext()
         awaitPointerEventScope {
             while (currentContext.isActive) {
diff --git a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SwipeToScene.kt b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SwipeToScene.kt
index 98d4aaa..061583a 100644
--- a/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SwipeToScene.kt
+++ b/packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SwipeToScene.kt
@@ -41,22 +41,62 @@
     draggableHandler: DraggableHandlerImpl,
     swipeDetector: SwipeDetector,
 ): Modifier {
-    return this.then(SwipeToSceneElement(draggableHandler, swipeDetector))
+    return if (draggableHandler.enabled()) {
+        this.then(SwipeToSceneElement(draggableHandler, swipeDetector))
+    } else {
+        this
+    }
+}
+
+private fun DraggableHandlerImpl.enabled(): Boolean {
+    return isDrivingTransition || contentForSwipes().shouldEnableSwipes(orientation)
+}
+
+private fun DraggableHandlerImpl.contentForSwipes(): Content {
+    return layoutImpl.contentForUserActions()
+}
+
+/** Whether swipe should be enabled in the given [orientation]. */
+private fun Content.shouldEnableSwipes(orientation: Orientation): Boolean {
+    if (userActions.isEmpty()) {
+        return false
+    }
+
+    return userActions.keys.any { it is Swipe.Resolved && it.direction.orientation == orientation }
 }
 
 private data class SwipeToSceneElement(
     val draggableHandler: DraggableHandlerImpl,
     val swipeDetector: SwipeDetector,
-) : ModifierNodeElement<SwipeToSceneNode>() {
-    override fun create(): SwipeToSceneNode = SwipeToSceneNode(draggableHandler, swipeDetector)
+) : ModifierNodeElement<SwipeToSceneRootNode>() {
+    override fun create(): SwipeToSceneRootNode =
+        SwipeToSceneRootNode(draggableHandler, swipeDetector)
 
-    override fun update(node: SwipeToSceneNode) {
-        node.draggableHandler = draggableHandler
+    override fun update(node: SwipeToSceneRootNode) {
+        node.update(draggableHandler, swipeDetector)
+    }
+}
+
+private class SwipeToSceneRootNode(
+    draggableHandler: DraggableHandlerImpl,
+    swipeDetector: SwipeDetector,
+) : DelegatingNode() {
+    private var delegate = delegate(SwipeToSceneNode(draggableHandler, swipeDetector))
+
+    fun update(draggableHandler: DraggableHandlerImpl, swipeDetector: SwipeDetector) {
+        if (draggableHandler == delegate.draggableHandler) {
+            // Simple update, just update the swipe detector directly and keep the node.
+            delegate.swipeDetector = swipeDetector
+        } else {
+            // The draggableHandler changed, force recreate the underlying SwipeToSceneNode.
+            undelegate(delegate)
+            delegate = delegate(SwipeToSceneNode(draggableHandler, swipeDetector))
+        }
     }
 }
 
 private class SwipeToSceneNode(
-    draggableHandler: DraggableHandlerImpl,
+    val draggableHandler: DraggableHandlerImpl,
     swipeDetector: SwipeDetector,
 ) : DelegatingNode(), PointerInputModifierNode {
     private val dispatcher = NestedScrollDispatcher()
@@ -64,7 +104,6 @@
         delegate(
             MultiPointerDraggableNode(
                 orientation = draggableHandler.orientation,
-                enabled = ::enabled,
                 startDragImmediately = ::startDragImmediately,
                 onDragStarted = draggableHandler::onDragStarted,
                 onFirstPointerDown = ::onFirstPointerDown,
@@ -73,18 +112,10 @@
             )
         )
 
-    private var _draggableHandler = draggableHandler
-    var draggableHandler: DraggableHandlerImpl
-        get() = _draggableHandler
+    var swipeDetector: SwipeDetector
+        get() = multiPointerDraggableNode.swipeDetector
         set(value) {
-            if (_draggableHandler != value) {
-                _draggableHandler = value
-
-                // Make sure to update the delegate orientation. Note that this will automatically
-                // reset the underlying pointer input handler, so previous gestures will be
-                // cancelled.
-                multiPointerDraggableNode.orientation = value.orientation
-            }
+            multiPointerDraggableNode.swipeDetector = value
         }
 
     private val nestedScrollHandlerImpl =
@@ -124,22 +155,6 @@
 
     override fun onCancelPointerInput() = multiPointerDraggableNode.onCancelPointerInput()
 
-    private fun enabled(): Boolean {
-        return draggableHandler.isDrivingTransition ||
-            contentForSwipes().shouldEnableSwipes(multiPointerDraggableNode.orientation)
-    }
-
-    private fun contentForSwipes(): Content {
-        return draggableHandler.layoutImpl.contentForUserActions()
-    }
-
-    /** Whether swipe should be enabled in the given [orientation]. */
-    private fun Content.shouldEnableSwipes(orientation: Orientation): Boolean {
-        return userActions.keys.any {
-            it is Swipe.Resolved && it.direction.orientation == orientation
-        }
-    }
-
     private fun startDragImmediately(startedPosition: Offset): Boolean {
         // Immediately start the drag if the user can't swipe in the other direction and the gesture
         // handler can intercept it.
@@ -152,7 +167,7 @@
                 Orientation.Vertical -> Orientation.Horizontal
                 Orientation.Horizontal -> Orientation.Vertical
             }
-        return contentForSwipes().shouldEnableSwipes(oppositeOrientation)
+        return draggableHandler.contentForSwipes().shouldEnableSwipes(oppositeOrientation)
     }
 }
 
diff --git a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/MultiPointerDraggableTest.kt b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/MultiPointerDraggableTest.kt
index 493f3a1..c8f6e6d 100644
--- a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/MultiPointerDraggableTest.kt
+++ b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/MultiPointerDraggableTest.kt
@@ -45,6 +45,7 @@
 import androidx.compose.ui.unit.Density
 import androidx.compose.ui.unit.Velocity
 import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.android.compose.modifiers.thenIf
 import com.android.compose.nestedscroll.SuspendedValue
 import com.google.common.truth.Truth.assertThat
 import kotlin.properties.Delegates
@@ -94,19 +95,20 @@
             Box(
                 Modifier.size(with(LocalDensity.current) { Size(size, size).toDpSize() })
                     .nestedScrollDispatcher()
-                    .multiPointerDraggable(
-                        orientation = Orientation.Vertical,
-                        enabled = { enabled },
-                        startDragImmediately = { false },
-                        onDragStarted = { _, _, _ ->
-                            started = true
-                            SimpleDragController(
-                                onDrag = { dragged = true },
-                                onStop = { stopped = true },
-                            )
-                        },
-                        dispatcher = defaultDispatcher,
-                    )
+                    .thenIf(enabled) {
+                        Modifier.multiPointerDraggable(
+                            orientation = Orientation.Vertical,
+                            startDragImmediately = { false },
+                            onDragStarted = { _, _, _ ->
+                                started = true
+                                SimpleDragController(
+                                    onDrag = { dragged = true },
+                                    onStop = { stopped = true },
+                                )
+                            },
+                            dispatcher = defaultDispatcher,
+                        )
+                    }
             )
         }
 
@@ -164,7 +166,6 @@
                     .nestedScrollDispatcher()
                     .multiPointerDraggable(
                         orientation = Orientation.Vertical,
-                        enabled = { true },
                         // We want to start a drag gesture immediately
                         startDragImmediately = { true },
                         onDragStarted = { _, _, _ ->
@@ -238,7 +239,6 @@
                     .nestedScrollDispatcher()
                     .multiPointerDraggable(
                         orientation = Orientation.Vertical,
-                        enabled = { true },
                         startDragImmediately = { false },
                         onDragStarted = { _, _, _ ->
                             started = true
@@ -358,7 +358,6 @@
                     .nestedScrollDispatcher()
                     .multiPointerDraggable(
                         orientation = Orientation.Vertical,
-                        enabled = { true },
                         startDragImmediately = { false },
                         onDragStarted = { _, _, _ ->
                             started = true
@@ -464,7 +463,6 @@
                     .nestedScrollDispatcher()
                     .multiPointerDraggable(
                         orientation = Orientation.Vertical,
-                        enabled = { true },
                         startDragImmediately = { false },
                         onDragStarted = { _, _, _ ->
                             verticalStarted = true
@@ -477,7 +475,6 @@
                     )
                     .multiPointerDraggable(
                         orientation = Orientation.Horizontal,
-                        enabled = { true },
                         startDragImmediately = { false },
                         onDragStarted = { _, _, _ ->
                             horizontalStarted = true
@@ -570,7 +567,6 @@
                     .nestedScrollDispatcher()
                     .multiPointerDraggable(
                         orientation = Orientation.Vertical,
-                        enabled = { true },
                         startDragImmediately = { false },
                         swipeDetector =
                             object : SwipeDetector {
@@ -672,7 +668,6 @@
                     .nestedScrollDispatcher()
                     .multiPointerDraggable(
                         orientation = Orientation.Vertical,
-                        enabled = { true },
                         startDragImmediately = { false },
                         onDragStarted = { _, _, _ ->
                             SimpleDragController(
@@ -744,7 +739,6 @@
                     .nestedScrollDispatcher()
                     .multiPointerDraggable(
                         orientation = Orientation.Vertical,
-                        enabled = { true },
                         startDragImmediately = { false },
                         onDragStarted = { _, _, _ ->
                             SimpleDragController(
diff --git a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SwipeToSceneTest.kt b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SwipeToSceneTest.kt
index 25e8713..28d0a47 100644
--- a/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SwipeToSceneTest.kt
+++ b/packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SwipeToSceneTest.kt
@@ -22,11 +22,15 @@
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.size
+import androidx.compose.material3.Button
+import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
@@ -36,9 +40,14 @@
 import androidx.compose.ui.platform.LocalViewConfiguration
 import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.test.assertPositionInRootIsEqualTo
+import androidx.compose.ui.test.assertTextEquals
 import androidx.compose.ui.test.junit4.createComposeRule
+import androidx.compose.ui.test.onNodeWithTag
 import androidx.compose.ui.test.onRoot
+import androidx.compose.ui.test.performClick
 import androidx.compose.ui.test.performTouchInput
+import androidx.compose.ui.test.swipeRight
+import androidx.compose.ui.test.swipeUp
 import androidx.compose.ui.test.swipeWithVelocity
 import androidx.compose.ui.unit.Density
 import androidx.compose.ui.unit.IntSize
@@ -844,4 +853,62 @@
         assertThat(transition.progress).isEqualTo(1f)
         assertThat(availableOnPostScroll).isEqualTo(ovescrollPx)
     }
+
+    @Test
+    fun sceneWithoutSwipesDoesNotConsumeGestures() {
+        val buttonTag = "button"
+
+        rule.setContent {
+            Box {
+                var count by remember { mutableStateOf(0) }
+                Button(onClick = { count++ }, Modifier.testTag(buttonTag).align(Alignment.Center)) {
+                    Text("Count: $count")
+                }
+
+                SceneTransitionLayout(remember { MutableSceneTransitionLayoutState(SceneA) }) {
+                    scene(SceneA) { Box(Modifier.fillMaxSize()) }
+                }
+            }
+        }
+
+        rule.onNodeWithTag(buttonTag).assertTextEquals("Count: 0")
+
+        // Click on the root at its center, where the button is located. Clicks should go through
+        // the STL and reach the button given that there is no swipes for the current scene.
+        repeat(3) { rule.onRoot().performClick() }
+        rule.onNodeWithTag(buttonTag).assertTextEquals("Count: 3")
+    }
+
+    @Test
+    fun swipeToSceneSupportsUpdates() {
+        val state = rule.runOnUiThread { MutableSceneTransitionLayoutState(SceneA) }
+
+        rule.setContent {
+            SceneTransitionLayout(state) {
+                // SceneA only has vertical actions, so only one vertical Modifier.swipeToScene()
+                // is composed.
+                scene(SceneA, mapOf(Swipe.Up to SceneB)) { Box(Modifier.fillMaxSize()) }
+
+                // SceneB only has horizontal actions, so only one vertical Modifier.swipeToScene()
+                // is composed, which will be force update it with a new draggableHandler.
+                scene(SceneB, mapOf(Swipe.Right to SceneC)) { Box(Modifier.fillMaxSize()) }
+                scene(SceneC) { Box(Modifier.fillMaxSize()) }
+            }
+        }
+
+        assertThat(state.transitionState).isIdle()
+        assertThat(state.transitionState).hasCurrentScene(SceneA)
+
+        // Swipe up to scene B.
+        rule.onRoot().performTouchInput { swipeUp() }
+        rule.waitForIdle()
+        assertThat(state.transitionState).isIdle()
+        assertThat(state.transitionState).hasCurrentScene(SceneB)
+
+        // Swipe right to scene C.
+        rule.onRoot().performTouchInput { swipeRight() }
+        rule.waitForIdle()
+        assertThat(state.transitionState).isIdle()
+        assertThat(state.transitionState).hasCurrentScene(SceneC)
+    }
 }