Merge "[7/N] Desks: Implement desk activation" into main

11 files changed, 373 insertions, 79 deletions

diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellModule.java b/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellModule.java
index 6f16e047a968..89eff5ea618c 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellModule.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellModule.java
@@ -1157,9 +1157,10 @@ public abstract class WMShellModule {
     @WMSingleton
     @Provides
     static DesksTransitionObserver provideDesksTransitionObserver(
-            @NonNull @DynamicOverride DesktopUserRepositories desktopUserRepositories
+            @NonNull @DynamicOverride DesktopUserRepositories desktopUserRepositories,
+            @NonNull DesksOrganizer desksOrganizer
     ) {
-        return new DesksTransitionObserver(desktopUserRepositories);
+        return new DesksTransitionObserver(desktopUserRepositories, desksOrganizer);
     }
 
     @WMSingleton
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopModeShellCommandHandler.kt b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopModeShellCommandHandler.kt
index b93d2e396402..b0a38a85e0b2 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopModeShellCommandHandler.kt
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopModeShellCommandHandler.kt
@@ -131,8 +131,8 @@ class DesktopModeShellCommandHandler(private val controller: DesktopTasksControl
                 pw.println("Error: desk id should be an integer")
                 return false
             }
-        pw.println("Not implemented.")
-        return false
+        controller.activateDesk(deskId)
+        return true
     }
 
     private fun runRemoveDesk(args: Array<String>, pw: PrintWriter): Boolean {
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopRepository.kt b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopRepository.kt
index 043b353ba380..9583f3da2ee3 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopRepository.kt
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopRepository.kt
@@ -226,6 +226,10 @@ class DesktopRepository(
         desktopData.setActiveDesk(displayId = displayId, deskId = deskId)
     }
 
+    /** Returns the id of the active desk in the given display, if any. */
+    @VisibleForTesting
+    fun getActiveDeskId(displayId: Int): Int? = desktopData.getActiveDesk(displayId)?.deskId
+
     /**
      * Adds task with [taskId] to the list of freeform tasks on [displayId]'s active desk.
      *
@@ -435,7 +439,7 @@ class DesktopRepository(
                 ?: error("Expected non-null desk in display $displayId")
             unminimizeTask(displayId, taskId)
         } else {
-            desktopData.getActiveDesk(displayId)?.visibleTasks?.remove(taskId)
+            desktopData.getDefaultDesk(displayId)?.visibleTasks?.remove(taskId)
         }
         val newCount = getVisibleTaskCount(displayId)
         if (prevCount != newCount) {
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopTasksController.kt b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopTasksController.kt
index 53f37659cf49..645367780390 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopTasksController.kt
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopTasksController.kt
@@ -315,24 +315,10 @@ class DesktopTasksController(
     }
 
     /** Show all tasks, that are part of the desktop, on top of launcher */
+    @Deprecated("Use activateDesk() instead.", ReplaceWith("activateDesk()"))
     fun showDesktopApps(displayId: Int, remoteTransition: RemoteTransition? = null) {
         logV("showDesktopApps")
-        val wct = WindowContainerTransaction()
-        bringDesktopAppsToFront(displayId, wct)
-
-        val transitionType = transitionType(remoteTransition)
-        val handler =
-            remoteTransition?.let {
-                OneShotRemoteHandler(transitions.mainExecutor, remoteTransition)
-            }
-        transitions.startTransition(transitionType, wct, handler).also { t ->
-            handler?.setTransition(t)
-        }
-
-        // launch from recent DesktopTaskView
-        desktopModeEnterExitTransitionListener?.onEnterDesktopModeTransitionStarted(
-            FREEFORM_ANIMATION_DURATION
-        )
+        activateDefaultDeskInDisplay(displayId, remoteTransition)
     }
 
     /** Gets number of visible freeform tasks in [displayId]. */
@@ -606,9 +592,9 @@ class DesktopTasksController(
         val wct = WindowContainerTransaction()
         exitSplitIfApplicable(wct, taskInfo)
         if (Flags.enablePerDisplayDesktopWallpaperActivity()) {
-            moveHomeTask(wct, toTop = true, taskInfo.displayId)
+            moveHomeTask(taskInfo.displayId, wct)
         } else {
-            moveHomeTask(wct, toTop = true)
+            moveHomeTask(context.displayId, wct)
         }
         val taskIdToMinimize =
             bringDesktopAppsToFrontBeforeShowingNewTask(taskInfo.displayId, wct, taskInfo.taskId)
@@ -780,7 +766,7 @@ class DesktopTasksController(
 
         // We are moving a freeform task to fullscreen, put the home task under the fullscreen task.
         if (!forceEnterDesktop(task.displayId)) {
-            moveHomeTask(wct, toTop = true, task.displayId)
+            moveHomeTask(task.displayId, wct)
             wct.reorder(task.token, /* onTop= */ true)
         }
 
@@ -1433,33 +1419,36 @@ class DesktopTasksController(
             ?: WINDOWING_MODE_UNDEFINED
     }
 
+    private fun prepareForDeskActivation(displayId: Int, wct: WindowContainerTransaction) {
+        // Move home to front, ensures that we go back home when all desktop windows are closed
+        val useParamDisplayId =
+            Flags.enableMultipleDesktopsBackend() ||
+                Flags.enablePerDisplayDesktopWallpaperActivity()
+        moveHomeTask(displayId = if (useParamDisplayId) displayId else context.displayId, wct = wct)
+        // Currently, we only handle the desktop on the default display really.
+        if (
+            (displayId == DEFAULT_DISPLAY || Flags.enablePerDisplayDesktopWallpaperActivity()) &&
+                ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY.isTrue()
+        ) {
+            // Add translucent wallpaper activity to show the wallpaper underneath.
+            addWallpaperActivity(displayId, wct)
+        }
+    }
+
     private fun bringDesktopAppsToFrontBeforeShowingNewTask(
         displayId: Int,
         wct: WindowContainerTransaction,
         newTaskIdInFront: Int,
     ): Int? = bringDesktopAppsToFront(displayId, wct, newTaskIdInFront)
 
+    @Deprecated("Use activeDesk() instead.", ReplaceWith("activateDesk()"))
     private fun bringDesktopAppsToFront(
         displayId: Int,
         wct: WindowContainerTransaction,
         newTaskIdInFront: Int? = null,
     ): Int? {
         logV("bringDesktopAppsToFront, newTaskId=%d", newTaskIdInFront)
-        // Move home to front, ensures that we go back home when all desktop windows are closed
-        if (Flags.enablePerDisplayDesktopWallpaperActivity()) {
-            moveHomeTask(wct, toTop = true, displayId)
-        } else {
-            moveHomeTask(wct, toTop = true)
-        }
-
-        // Currently, we only handle the desktop on the default display really.
-        if (
-            (displayId == DEFAULT_DISPLAY || Flags.enablePerDisplayDesktopWallpaperActivity()) &&
-                ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY.isTrue()
-        ) {
-            // Add translucent wallpaper activity to show the wallpaper underneath
-            addWallpaperActivity(displayId, wct)
-        }
+        prepareForDeskActivation(displayId, wct)
 
         val expandedTasksOrderedFrontToBack = taskRepository.getExpandedTasksOrdered(displayId)
         // If we're adding a new Task we might need to minimize an old one
@@ -1503,15 +1492,11 @@ class DesktopTasksController(
         return taskIdToMinimize
     }
 
-    private fun moveHomeTask(
-        wct: WindowContainerTransaction,
-        toTop: Boolean,
-        displayId: Int = DEFAULT_DISPLAY,
-    ) {
+    private fun moveHomeTask(displayId: Int, wct: WindowContainerTransaction) {
         shellTaskOrganizer
             .getRunningTasks(displayId)
             .firstOrNull { task -> task.activityType == ACTIVITY_TYPE_HOME }
-            ?.let { homeTask -> wct.reorder(homeTask.getToken(), /* onTop= */ toTop) }
+            ?.let { homeTask -> wct.reorder(homeTask.getToken(), /* onTop= */ true) }
     }
 
     private fun addLaunchHomePendingIntent(wct: WindowContainerTransaction, displayId: Int) {
@@ -2389,6 +2374,57 @@ class DesktopTasksController(
         )
     }
 
+    private fun activateDefaultDeskInDisplay(
+        displayId: Int,
+        remoteTransition: RemoteTransition? = null,
+    ) {
+        val deskId =
+            checkNotNull(taskRepository.getDefaultDeskId(displayId)) {
+                "Expected a default desk to exist"
+            }
+        activateDesk(deskId, remoteTransition)
+    }
+
+    /** Activates the given desk. */
+    fun activateDesk(deskId: Int, remoteTransition: RemoteTransition? = null) {
+        val displayId = taskRepository.getDisplayForDesk(deskId)
+        val wct = WindowContainerTransaction()
+        if (Flags.enableMultipleDesktopsBackend()) {
+            prepareForDeskActivation(displayId, wct)
+            desksOrganizer.activateDesk(wct, deskId)
+            if (DesktopModeFlags.ENABLE_DESKTOP_WINDOWING_PERSISTENCE.isTrue()) {
+                // TODO: 362720497 - do non-running tasks need to be restarted with |wct#startTask|?
+            }
+            taskbarDesktopTaskListener?.onTaskbarCornerRoundingUpdate(
+                doesAnyTaskRequireTaskbarRounding(displayId)
+            )
+        } else {
+            bringDesktopAppsToFront(displayId, wct)
+        }
+
+        val transitionType = transitionType(remoteTransition)
+        val handler =
+            remoteTransition?.let {
+                OneShotRemoteHandler(transitions.mainExecutor, remoteTransition)
+            }
+
+        val transition = transitions.startTransition(transitionType, wct, handler)
+        handler?.setTransition(transition)
+        if (Flags.enableMultipleDesktopsBackend()) {
+            desksTransitionObserver.addPendingTransition(
+                DeskTransition.ActivateDesk(
+                    token = transition,
+                    displayId = displayId,
+                    deskId = deskId,
+                )
+            )
+        }
+
+        desktopModeEnterExitTransitionListener?.onEnterDesktopModeTransitionStarted(
+            FREEFORM_ANIMATION_DURATION
+        )
+    }
+
     /** Removes the default desk in the given display. */
     @Deprecated("Deprecated with multi-desks.", ReplaceWith("removeDesk()"))
     fun removeDefaultDeskInDisplay(displayId: Int) {
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DeskTransition.kt b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DeskTransition.kt
index 47088c0b545a..4b658caf34ed 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DeskTransition.kt
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DeskTransition.kt
@@ -30,4 +30,8 @@ sealed class DeskTransition {
         val tasks: Set<Int>,
         val onDeskRemovedListener: OnDeskRemovedListener?,
     ) : DeskTransition()
+
+    /** A transition to activate a desk in its display. */
+    data class ActivateDesk(override val token: IBinder, val displayId: Int, val deskId: Int) :
+        DeskTransition()
 }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DesksOrganizer.kt b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DesksOrganizer.kt
index 5cbb59fbf323..547890a6200a 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DesksOrganizer.kt
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DesksOrganizer.kt
@@ -43,6 +43,9 @@ interface DesksOrganizer {
      */
     fun getDeskAtEnd(change: TransitionInfo.Change): Int?
 
+    /** Whether the desk is activate according to the given change at the end of a transition. */
+    fun isDeskActiveAtEnd(change: TransitionInfo.Change, deskId: Int): Boolean
+
     /** A callback that is invoked when the desk container is created. */
     fun interface OnCreateCallback {
         /** Calls back when the [deskId] has been created. */
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DesksTransitionObserver.kt b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DesksTransitionObserver.kt
index 3e49b8a4538b..c235f204ece4 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DesksTransitionObserver.kt
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/DesksTransitionObserver.kt
@@ -25,7 +25,10 @@ import com.android.wm.shell.desktopmode.DesktopUserRepositories
  * Observer of desk-related transitions, such as adding, removing or activating a whole desk. It
  * tracks pending transitions and updates repository state once they finish.
  */
-class DesksTransitionObserver(private val desktopUserRepositories: DesktopUserRepositories) {
+class DesksTransitionObserver(
+    private val desktopUserRepositories: DesktopUserRepositories,
+    private val desksOrganizer: DesksOrganizer,
+) {
     private val deskTransitions = mutableMapOf<IBinder, DeskTransition>()
 
     /** Adds a pending desk transition to be tracked. */
@@ -53,6 +56,18 @@ class DesksTransitionObserver(private val desktopUserRepositories: DesktopUserRe
                 desktopRepository.removeDesk(deskTransition.deskId)
                 deskTransition.onDeskRemovedListener?.onDeskRemoved(displayId, deskId)
             }
+            is DeskTransition.ActivateDesk -> {
+                val activeDeskChange =
+                    info.changes.find { change ->
+                        desksOrganizer.isDeskActiveAtEnd(change, deskTransition.deskId)
+                    }
+                activeDeskChange?.let {
+                    desktopRepository.setActiveDesk(
+                        displayId = deskTransition.displayId,
+                        deskId = deskTransition.deskId,
+                    )
+                }
+            }
         }
     }
 }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/RootTaskDesksOrganizer.kt b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/RootTaskDesksOrganizer.kt
index 79c48c5e9594..65c0793aab51 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/RootTaskDesksOrganizer.kt
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/multidesks/RootTaskDesksOrganizer.kt
@@ -22,6 +22,7 @@ import android.app.WindowConfiguration.WINDOWING_MODE_FREEFORM
 import android.app.WindowConfiguration.WINDOWING_MODE_UNDEFINED
 import android.util.SparseArray
 import android.view.SurfaceControl
+import android.view.WindowManager.TRANSIT_TO_FRONT
 import android.window.TransitionInfo
 import android.window.WindowContainerTransaction
 import androidx.core.util.forEach
@@ -94,6 +95,11 @@ class RootTaskDesksOrganizer(
     override fun getDeskAtEnd(change: TransitionInfo.Change): Int? =
         change.taskInfo?.parentTaskId?.takeIf { it in roots }
 
+    override fun isDeskActiveAtEnd(change: TransitionInfo.Change, deskId: Int): Boolean =
+        change.taskInfo?.taskId == deskId &&
+            change.taskInfo?.isVisibleRequested == true &&
+            change.mode == TRANSIT_TO_FRONT
+
     override fun onTaskAppeared(taskInfo: RunningTaskInfo, leash: SurfaceControl) {
         if (taskInfo.parentTaskId in roots) {
             val deskId = taskInfo.parentTaskId
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/DesktopTasksControllerTest.kt b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/DesktopTasksControllerTest.kt
index c10d2afbdc99..f5e45be96fc7 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/DesktopTasksControllerTest.kt
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/DesktopTasksControllerTest.kt
@@ -66,6 +66,7 @@ import android.widget.Toast
 import android.window.DisplayAreaInfo
 import android.window.IWindowContainerToken
 import android.window.RemoteTransition
+import android.window.TransitionInfo
 import android.window.TransitionRequestInfo
 import android.window.WindowContainerToken
 import android.window.WindowContainerTransaction
@@ -519,7 +520,10 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     }
 
     @Test
-    @DisableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
     fun showDesktopApps_allAppsInvisible_bringsToFront_desktopWallpaperDisabled() {
         val homeTask = setUpHomeTask()
         val task1 = setUpFreeformTask()
@@ -540,6 +544,7 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
 
     @Test
     @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND)
     fun showDesktopApps_allAppsInvisible_bringsToFront_desktopWallpaperEnabled() {
         val task1 = setUpFreeformTask()
         val task2 = setUpFreeformTask()
@@ -558,6 +563,29 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     }
 
     @Test
+    @EnableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
+    fun showDesktopApps_deskInactive_bringsToFront_multipleDesksEnabled() {
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(Binder())
+        val deskId = 0
+        // Make desk inactive by activating another desk.
+        taskRepository.addDesk(DEFAULT_DISPLAY, deskId = 1)
+        taskRepository.setActiveDesk(DEFAULT_DISPLAY, deskId = 1)
+
+        controller.activateDesk(deskId, RemoteTransition(TestRemoteTransition()))
+
+        val wct =
+            getLatestWct(type = TRANSIT_TO_FRONT, handlerClass = OneShotRemoteHandler::class.java)
+        // Wallpaper is moved to front.
+        wct.assertPendingIntentAt(index = 0, desktopWallpaperIntent)
+        // Desk is activated.
+        verify(desksOrganizer).activateDesk(wct, deskId)
+    }
+
+    @Test
     fun isDesktopModeShowing_noTasks_returnsFalse() {
         assertThat(controller.isDesktopModeShowing(displayId = 0)).isFalse()
     }
@@ -631,58 +659,83 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
         Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
         Flags.FLAG_ENABLE_PER_DISPLAY_DESKTOP_WALLPAPER_ACTIVITY,
     )
-    @DisableFlags(
-        /** TODO: b/362720497 - re-enable when activation is implemented. */
-        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND
-    )
-    fun showDesktopApps_onSecondaryDisplay_desktopWallpaperEnabled_perDisplayWallpaperEnabled_shouldShowWallpaper() {
+    @DisableFlags(Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND)
+    fun showDesktopApps_onSecondaryDisplay_desktopWallpaperEnabled_perDisplayWallpaperEnabled_bringsTasksToFront() {
         taskRepository.addDesk(displayId = SECOND_DISPLAY, deskId = SECOND_DISPLAY)
-        val homeTask = setUpHomeTask(SECOND_DISPLAY)
+        setUpHomeTask(SECOND_DISPLAY)
         val task1 = setUpFreeformTask(SECOND_DISPLAY)
         val task2 = setUpFreeformTask(SECOND_DISPLAY)
         markTaskHidden(task1)
         markTaskHidden(task2)
 
+        assertThat(taskRepository.getExpandedTasksOrdered(SECOND_DISPLAY)).contains(task1.taskId)
+        assertThat(taskRepository.getExpandedTasksOrdered(SECOND_DISPLAY)).contains(task2.taskId)
         controller.showDesktopApps(SECOND_DISPLAY, RemoteTransition(TestRemoteTransition()))
 
         val wct =
             getLatestWct(type = TRANSIT_TO_FRONT, handlerClass = OneShotRemoteHandler::class.java)
-        assertThat(wct.hierarchyOps).hasSize(4)
-        // Expect order to be from bottom: home, wallpaperIntent, task1, task2
-        wct.assertReorderAt(index = 0, homeTask)
-        wct.assertPendingIntentAt(index = 1, desktopWallpaperIntent)
-        wct.assertReorderAt(index = 2, task1)
-        wct.assertReorderAt(index = 3, task2)
+        wct.assertReorder(task1)
+        wct.assertReorder(task2)
     }
 
     @Test
-    @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
-    @DisableFlags(
+    @EnableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
         Flags.FLAG_ENABLE_PER_DISPLAY_DESKTOP_WALLPAPER_ACTIVITY,
-        /** TODO: b/362720497 - re-enable when activation is implemented. */
         Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
     )
+    fun showDesktopApps_onSecondaryDisplay_desktopWallpaperEnabled_perDisplayWallpaperEnabled_multipleDesksEnabled_bringsDeskToFront() {
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(Binder())
+        taskRepository.addDesk(displayId = SECOND_DISPLAY, deskId = 2)
+        setUpHomeTask(SECOND_DISPLAY)
+
+        controller.showDesktopApps(SECOND_DISPLAY, RemoteTransition(TestRemoteTransition()))
+
+        val wct =
+            getLatestWct(type = TRANSIT_TO_FRONT, handlerClass = OneShotRemoteHandler::class.java)
+        verify(desksOrganizer).activateDesk(wct, deskId = 2)
+    }
+
+    @Test
+    @EnableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_PER_DISPLAY_DESKTOP_WALLPAPER_ACTIVITY,
+    )
+    fun showDesktopApps_onSecondaryDisplay_desktopWallpaperEnabled_perDisplayWallpaperEnabled_shouldShowWallpaper() {
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(Binder())
+        taskRepository.addDesk(displayId = SECOND_DISPLAY, deskId = SECOND_DISPLAY)
+        setUpHomeTask(SECOND_DISPLAY)
+
+        controller.showDesktopApps(SECOND_DISPLAY, RemoteTransition(TestRemoteTransition()))
+
+        val wct =
+            getLatestWct(type = TRANSIT_TO_FRONT, handlerClass = OneShotRemoteHandler::class.java)
+        wct.assertPendingIntent(desktopWallpaperIntent)
+    }
+
+    @Test
+    @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(Flags.FLAG_ENABLE_PER_DISPLAY_DESKTOP_WALLPAPER_ACTIVITY)
     fun showDesktopApps_onSecondaryDisplay_desktopWallpaperEnabled_shouldNotShowWallpaper() {
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(Binder())
         taskRepository.addDesk(displayId = SECOND_DISPLAY, deskId = SECOND_DISPLAY)
         val homeTask = setUpHomeTask(SECOND_DISPLAY)
-        val task1 = setUpFreeformTask(SECOND_DISPLAY)
-        val task2 = setUpFreeformTask(SECOND_DISPLAY)
-        markTaskHidden(task1)
-        markTaskHidden(task2)
 
         controller.showDesktopApps(SECOND_DISPLAY, RemoteTransition(TestRemoteTransition()))
 
         val wct =
             getLatestWct(type = TRANSIT_TO_FRONT, handlerClass = OneShotRemoteHandler::class.java)
-        assertThat(wct.hierarchyOps).hasSize(3)
-        // Expect order to be from bottom: home, task1, task2 (no wallpaper intent)
-        wct.assertReorderAt(index = 0, homeTask)
-        wct.assertReorderAt(index = 1, task1)
-        wct.assertReorderAt(index = 2, task2)
+        wct.assertWithoutPendingIntent(desktopWallpaperIntent)
     }
 
     @Test
-    @DisableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
     fun showDesktopApps_appsAlreadyVisible_bringsToFront_desktopWallpaperDisabled() {
         val homeTask = setUpHomeTask()
         val task1 = setUpFreeformTask()
@@ -704,7 +757,6 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     @Test
     @DisableFlags(
         Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
-        /** TODO: b/362720497 - re-enable when activation is implemented. */
         Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
     )
     fun showDesktopApps_onSecondaryDisplay_desktopWallpaperDisabled_shouldNotMoveLauncher() {
@@ -728,6 +780,7 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
 
     @Test
     @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND)
     fun showDesktopApps_appsAlreadyVisible_bringsToFront_desktopWallpaperEnabled() {
         val task1 = setUpFreeformTask()
         val task2 = setUpFreeformTask()
@@ -746,7 +799,10 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     }
 
     @Test
-    @DisableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
     fun showDesktopApps_someAppsInvisible_reordersAll_desktopWallpaperDisabled() {
         val homeTask = setUpHomeTask()
         val task1 = setUpFreeformTask()
@@ -767,6 +823,7 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
 
     @Test
     @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND)
     fun showDesktopApps_someAppsInvisible_reordersAll_desktopWallpaperEnabled() {
         val task1 = setUpFreeformTask()
         val task2 = setUpFreeformTask()
@@ -785,7 +842,10 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     }
 
     @Test
-    @DisableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
     fun showDesktopApps_noActiveTasks_reorderHomeToTop_desktopWallpaperDisabled() {
         val homeTask = setUpHomeTask()
 
@@ -800,6 +860,8 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     @Test
     @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
     fun showDesktopApps_noActiveTasks_addDesktopWallpaper_desktopWallpaperEnabled() {
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(Binder())
         controller.showDesktopApps(DEFAULT_DISPLAY, RemoteTransition(TestRemoteTransition()))
 
         val wct =
@@ -808,7 +870,10 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     }
 
     @Test
-    @DisableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
     fun showDesktopApps_twoDisplays_bringsToFrontOnlyOneDisplay_desktopWallpaperDisabled() {
         taskRepository.addDesk(displayId = SECOND_DISPLAY, deskId = SECOND_DISPLAY)
         val homeTaskDefaultDisplay = setUpHomeTask(DEFAULT_DISPLAY)
@@ -831,6 +896,8 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     @Test
     @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
     fun showDesktopApps_twoDisplays_bringsToFrontOnlyOneDisplay_desktopWallpaperEnabled() {
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(Binder())
         taskRepository.addDesk(displayId = SECOND_DISPLAY, deskId = SECOND_DISPLAY)
         val homeTaskDefaultDisplay = setUpHomeTask(DEFAULT_DISPLAY)
         val taskDefaultDisplay = setUpFreeformTask(DEFAULT_DISPLAY)
@@ -843,17 +910,63 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
 
         val wct =
             getLatestWct(type = TRANSIT_TO_FRONT, handlerClass = OneShotRemoteHandler::class.java)
-        assertThat(wct.hierarchyOps).hasSize(3)
         // Move home to front
         wct.assertReorderAt(index = 0, homeTaskDefaultDisplay)
         // Add desktop wallpaper activity
         wct.assertPendingIntentAt(index = 1, desktopWallpaperIntent)
+    }
+
+    @Test
+    @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @DisableFlags(Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND)
+    fun showDesktopApps_twoDisplays_bringsToFrontOnlyOneDisplayTasks_desktopWallpaperEnabled_multiDesksDisabled() {
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(Binder())
+        taskRepository.addDesk(displayId = SECOND_DISPLAY, deskId = SECOND_DISPLAY)
+        val homeTaskDefaultDisplay = setUpHomeTask(DEFAULT_DISPLAY)
+        val taskDefaultDisplay = setUpFreeformTask(DEFAULT_DISPLAY)
+        setUpHomeTask(SECOND_DISPLAY)
+        val taskSecondDisplay = setUpFreeformTask(SECOND_DISPLAY)
+        markTaskHidden(taskDefaultDisplay)
+        markTaskHidden(taskSecondDisplay)
+
+        controller.showDesktopApps(DEFAULT_DISPLAY, RemoteTransition(TestRemoteTransition()))
+
+        val wct =
+            getLatestWct(type = TRANSIT_TO_FRONT, handlerClass = OneShotRemoteHandler::class.java)
         // Move freeform task to front
         wct.assertReorderAt(index = 2, taskDefaultDisplay)
     }
 
     @Test
-    @DisableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    @EnableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
+    fun showDesktopApps_twoDisplays_bringsToFrontOnlyOneDisplayTasks_desktopWallpaperEnabled_multiDesksEnabled() {
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(Binder())
+        taskRepository.addDesk(displayId = SECOND_DISPLAY, deskId = SECOND_DISPLAY)
+        val homeTaskDefaultDisplay = setUpHomeTask(DEFAULT_DISPLAY)
+        val taskDefaultDisplay = setUpFreeformTask(DEFAULT_DISPLAY)
+        setUpHomeTask(SECOND_DISPLAY)
+        val taskSecondDisplay = setUpFreeformTask(SECOND_DISPLAY)
+        markTaskHidden(taskDefaultDisplay)
+        markTaskHidden(taskSecondDisplay)
+
+        controller.showDesktopApps(DEFAULT_DISPLAY, RemoteTransition(TestRemoteTransition()))
+
+        val wct =
+            getLatestWct(type = TRANSIT_TO_FRONT, handlerClass = OneShotRemoteHandler::class.java)
+        // Move desktop tasks to front
+        verify(desksOrganizer).activateDesk(wct, deskId = DEFAULT_DISPLAY)
+    }
+
+    @Test
+    @DisableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
     fun showDesktopApps_desktopWallpaperDisabled_dontReorderMinimizedTask() {
         val homeTask = setUpHomeTask()
         val freeformTask = setUpFreeformTask()
@@ -874,6 +987,8 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
 
     @Test
     @EnableFlags(Flags.FLAG_ENABLE_DESKTOP_WINDOWING_WALLPAPER_ACTIVITY)
+    /** TODO: b/362720497 - add multi-desk version when minimization is implemented. */
+    @DisableFlags(Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND)
     fun showDesktopApps_desktopWallpaperEnabled_dontReorderMinimizedTask() {
         val homeTask = setUpHomeTask()
         val freeformTask = setUpFreeformTask()
@@ -3641,6 +3756,34 @@ class DesktopTasksControllerTest(flags: FlagsParameterization) : ShellTestCase()
     }
 
     @Test
+    @EnableFlags(
+        Flags.FLAG_ENABLE_DESKTOP_WINDOWING_BACK_NAVIGATION,
+        Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND,
+    )
+    fun activateDesk_multipleDesks_addsPendingTransition() {
+        val deskId = 0
+        val transition = Binder()
+        val deskChange = mock(TransitionInfo.Change::class.java)
+        whenever(transitions.startTransition(eq(TRANSIT_TO_FRONT), any(), anyOrNull()))
+            .thenReturn(transition)
+        whenever(desksOrganizer.isDeskActiveAtEnd(deskChange, deskId)).thenReturn(true)
+        // Make desk inactive by activating another desk.
+        taskRepository.addDesk(DEFAULT_DISPLAY, deskId = 1)
+        taskRepository.setActiveDesk(DEFAULT_DISPLAY, deskId = 1)
+
+        controller.activateDesk(deskId, RemoteTransition(TestRemoteTransition()))
+
+        verify(desksTransitionsObserver)
+            .addPendingTransition(
+                argThat {
+                    this is DeskTransition.ActivateDesk &&
+                        this.token == transition &&
+                        this.deskId == 0
+                }
+            )
+    }
+
+    @Test
     @EnableFlags(Flags.FLAG_ENABLE_WINDOWING_DYNAMIC_INITIAL_BOUNDS)
     fun dragToDesktop_landscapeDevice_resizable_undefinedOrientation_defaultLandscapeBounds() {
         val spyController = spy(controller)
@@ -5617,6 +5760,29 @@ private fun WindowContainerTransaction.assertIndexInBounds(index: Int) {
         .isGreaterThan(index)
 }
 
+private fun WindowContainerTransaction.assertHop(
+    predicate: (WindowContainerTransaction.HierarchyOp) -> Boolean
+) {
+    assertThat(hierarchyOps.any(predicate)).isTrue()
+}
+
+private fun WindowContainerTransaction.assertWithoutHop(
+    predicate: (WindowContainerTransaction.HierarchyOp) -> Boolean
+) {
+    assertThat(hierarchyOps.none(predicate)).isTrue()
+}
+
+private fun WindowContainerTransaction.assertReorder(
+    task: RunningTaskInfo,
+    toTop: Boolean? = null,
+) {
+    assertHop { hop ->
+        hop.type == HIERARCHY_OP_TYPE_REORDER &&
+            (toTop == null || hop.toTop == toTop) &&
+            hop.container == task.token.asBinder()
+    }
+}
+
 private fun WindowContainerTransaction.assertReorderAt(
     index: Int,
     task: RunningTaskInfo,
@@ -5678,6 +5844,20 @@ private fun WindowContainerTransaction.hasRemoveAt(index: Int, token: WindowCont
     assertThat(op.container).isEqualTo(token.asBinder())
 }
 
+private fun WindowContainerTransaction.assertPendingIntent(intent: Intent) {
+    assertHop { hop ->
+        hop.type == HIERARCHY_OP_TYPE_PENDING_INTENT &&
+            hop.pendingIntent?.intent?.component == intent.component
+    }
+}
+
+private fun WindowContainerTransaction.assertWithoutPendingIntent(intent: Intent) {
+    assertWithoutHop { hop ->
+        hop.type == HIERARCHY_OP_TYPE_PENDING_INTENT &&
+            hop.pendingIntent?.intent?.component == intent.component
+    }
+}
+
 private fun WindowContainerTransaction.assertPendingIntentAt(index: Int, intent: Intent) {
     assertIndexInBounds(index)
     val op = hierarchyOps[index]
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/multidesks/DesksTransitionObserverTest.kt b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/multidesks/DesksTransitionObserverTest.kt
index bfbaa84e9312..00c54c2ecc18 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/multidesks/DesksTransitionObserverTest.kt
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/multidesks/DesksTransitionObserverTest.kt
@@ -21,7 +21,9 @@ import android.platform.test.flag.junit.SetFlagsRule
 import android.testing.AndroidTestingRunner
 import android.view.Display.DEFAULT_DISPLAY
 import android.view.WindowManager.TRANSIT_CLOSE
+import android.view.WindowManager.TRANSIT_TO_FRONT
 import android.window.TransitionInfo
+import android.window.TransitionInfo.Change
 import androidx.test.filters.SmallTest
 import com.android.window.flags.Flags
 import com.android.wm.shell.ShellTestCase
@@ -35,6 +37,7 @@ import org.junit.Rule
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.mockito.kotlin.mock
+import org.mockito.kotlin.whenever
 
 /**
  * Tests for [DesksTransitionObserver].
@@ -47,6 +50,8 @@ class DesksTransitionObserverTest : ShellTestCase() {
 
     @JvmField @Rule val setFlagsRule = SetFlagsRule()
 
+    private val mockDesksOrganizer = mock<DesksOrganizer>()
+
     private lateinit var desktopUserRepositories: DesktopUserRepositories
     private lateinit var observer: DesksTransitionObserver
 
@@ -65,7 +70,7 @@ class DesksTransitionObserverTest : ShellTestCase() {
                 /* mainCoroutineScope= */ mock(),
                 /* userManager= */ mock(),
             )
-        observer = DesksTransitionObserver(desktopUserRepositories)
+        observer = DesksTransitionObserver(desktopUserRepositories, mockDesksOrganizer)
     }
 
     @Test
@@ -121,4 +126,23 @@ class DesksTransitionObserverTest : ShellTestCase() {
 
         assertThat(removeListener.lastDeskRemoved).isEqualTo(5)
     }
+
+    @Test
+    @EnableFlags(Flags.FLAG_ENABLE_MULTIPLE_DESKTOPS_BACKEND)
+    fun onTransitionReady_activateDesk_updatesRepository() {
+        val transition = Binder()
+        val change = Change(mock(), mock())
+        whenever(mockDesksOrganizer.isDeskActiveAtEnd(change, deskId = 5)).thenReturn(true)
+        val activateTransition =
+            DeskTransition.ActivateDesk(transition, displayId = DEFAULT_DISPLAY, deskId = 5)
+        repository.addDesk(DEFAULT_DISPLAY, deskId = 5)
+
+        observer.addPendingTransition(activateTransition)
+        observer.onTransitionReady(
+            transition = transition,
+            info = TransitionInfo(TRANSIT_TO_FRONT, /* flags= */ 0).apply { addChange(change) },
+        )
+
+        assertThat(repository.getActiveDeskId(DEFAULT_DISPLAY)).isEqualTo(5)
+    }
 }
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/multidesks/RootTaskDesksOrganizerTest.kt b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/multidesks/RootTaskDesksOrganizerTest.kt
index a07203d86b75..fbc78b21353e 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/multidesks/RootTaskDesksOrganizerTest.kt
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/multidesks/RootTaskDesksOrganizerTest.kt
@@ -18,6 +18,7 @@ package com.android.wm.shell.desktopmode.multidesks
 import android.testing.AndroidTestingRunner
 import android.view.Display
 import android.view.SurfaceControl
+import android.view.WindowManager.TRANSIT_TO_FRONT
 import android.window.TransitionInfo
 import android.window.WindowContainerTransaction
 import android.window.WindowContainerTransaction.HierarchyOp
@@ -244,6 +245,26 @@ class RootTaskDesksOrganizerTest : ShellTestCase() {
         assertThat(endDesk).isEqualTo(freeformRoot.taskId)
     }
 
+    @Test
+    fun testIsDeskActiveAtEnd() {
+        organizer.createDesk(Display.DEFAULT_DISPLAY, FakeOnCreateCallback())
+        val freeformRoot = createFreeformTask().apply { parentTaskId = -1 }
+        freeformRoot.isVisibleRequested = true
+        organizer.onTaskAppeared(freeformRoot, SurfaceControl())
+
+        val isActive =
+            organizer.isDeskActiveAtEnd(
+                change =
+                    TransitionInfo.Change(freeformRoot.token, SurfaceControl()).apply {
+                        taskInfo = freeformRoot
+                        mode = TRANSIT_TO_FRONT
+                    },
+                deskId = freeformRoot.taskId,
+            )
+
+        assertThat(isActive).isTrue()
+    }
+
     private class FakeOnCreateCallback : DesksOrganizer.OnCreateCallback {
         var deskId: Int? = null
         val created: Boolean