Add hidden system dream API in DreamManagerService.

This change
- adds a new private API in dream manager that allows a client with
  write dream permission to set a system dream component, which takes
  precedence over user configured dream
- fixes startDream() API in DreamManager which shouldn't take in a
  component name

Test: atest SystemDreamTest
Bug: 222529147
Change-Id: Iee9a0af1071e5ed57fa5bd4b0d06d8178118116e

core/api/test-current.txt

@@ -286,7 +286,8 @@ package android.app {
     method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void setActiveDream(@Nullable android.content.ComponentName);
     method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void setDreamOverlay(@Nullable android.content.ComponentName);
     method @RequiresPermission(android.Manifest.permission.WRITE_SECURE_SETTINGS) public void setScreensaverEnabled(boolean);
-    method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void startDream(@NonNull android.content.ComponentName);
+    method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void setSystemDreamComponent(@Nullable android.content.ComponentName);
+    method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void startDream();
     method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void stopDream();
   }
 

core/java/android/app/DreamManager.java

@@ -18,7 +18,6 @@ package android.app;
 
 import static android.Manifest.permission.WRITE_SECURE_SETTINGS;
 
-import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemService;
@@ -86,16 +85,23 @@ public class DreamManager {
     }
 
     /**
-     * Starts dream service with name "name".
+     * Starts dreaming.
+     *
+     * The system dream component, if set by {@link DreamManager#setSystemDreamComponent}, will be
+     * started.
+     * Otherwise, starts the active dream set by {@link DreamManager#setActiveDream}.
      *
      * <p>This is only used for testing the dream service APIs.
      *
+     * @see DreamManager#setActiveDream(ComponentName)
+     * @see DreamManager#setSystemDreamComponent(ComponentName)
+     *
      * @hide
      */
     @TestApi
     @UserHandleAware
     @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE)
-    public void startDream(@NonNull ComponentName name) {
+    public void startDream() {
         try {
             mService.dream();
         } catch (RemoteException e) {
@@ -141,6 +147,25 @@ public class DreamManager {
         }
     }
 
+    /**
+     * Sets or clears the system dream component.
+     *
+     * The system dream component, when set, will be shown instead of the user configured dream
+     * when the system starts dreaming (not dozing). If the system is dreaming at the time the
+     * system dream is set or cleared, it immediately switches dream.
+     *
+     * @hide
+     */
+    @TestApi
+    @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE)
+    public void setSystemDreamComponent(@Nullable ComponentName dreamComponent) {
+        try {
+            mService.setSystemDreamComponent(dreamComponent);
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
     /**
      * Sets the active dream on the device to be "dreamComponent".
      *

core/java/android/service/dreams/IDreamManager.aidl

@@ -43,5 +43,6 @@ interface IDreamManager {
     void forceAmbientDisplayEnabled(boolean enabled);
     ComponentName[] getDreamComponentsForUser(int userId);
     void setDreamComponentsForUser(int userId, in ComponentName[] componentNames);
+    void setSystemDreamComponent(in ComponentName componentName);
     void registerDreamOverlayService(in ComponentName componentName);
 }

services/core/java/com/android/server/dreams/DreamManagerService.java

@@ -110,6 +110,10 @@ public final class DreamManagerService extends SystemService {
     private int mCurrentDreamDozeScreenState = Display.STATE_UNKNOWN;
     private int mCurrentDreamDozeScreenBrightness = PowerManager.BRIGHTNESS_DEFAULT;
 
+    // A temporary dream component that, when present, takes precedence over user configured dream
+    // component.
+    private ComponentName mSystemDreamComponent;
+
     private ComponentName mDreamOverlayServiceName;
 
     private AmbientDisplayConfiguration mDozeConfig;
@@ -352,11 +356,21 @@ public final class DreamManagerService extends SystemService {
         return chooseDreamForUser(doze, ActivityManager.getCurrentUser());
     }
 
+    /**
+     * If doze is true, returns the doze component for the user.
+     * Otherwise, returns the system dream component, if present.
+     * Otherwise, returns the first valid user configured dream component.
+     */
     private ComponentName chooseDreamForUser(boolean doze, int userId) {
         if (doze) {
             ComponentName dozeComponent = getDozeComponent(userId);
             return validateDream(dozeComponent) ? dozeComponent : null;
         }
+
+        if (mSystemDreamComponent != null) {
+            return mSystemDreamComponent;
+        }
+
         ComponentName[] dreams = getDreamComponentsForUser(userId);
         return dreams != null && dreams.length != 0 ? dreams[0] : null;
     }
@@ -416,6 +430,21 @@ public final class DreamManagerService extends SystemService {
                 userId);
     }
 
+    private void setSystemDreamComponentInternal(ComponentName componentName) {
+        synchronized (mLock) {
+            if (Objects.equals(mSystemDreamComponent, componentName)) {
+                return;
+            }
+
+            mSystemDreamComponent = componentName;
+
+            // Switch dream if currently dreaming and not dozing.
+            if (isDreamingInternal() && !mCurrentDreamIsDozing) {
+                startDreamInternal(false);
+            }
+        }
+    }
+
     private ComponentName getDefaultDreamComponentForUser(int userId) {
         String name = Settings.Secure.getStringForUser(mContext.getContentResolver(),
                 Settings.Secure.SCREENSAVER_DEFAULT_COMPONENT,
@@ -667,6 +696,18 @@ public final class DreamManagerService extends SystemService {
             }
         }
 
+        @Override // Binder call
+        public void setSystemDreamComponent(ComponentName componentName) {
+            checkPermission(android.Manifest.permission.WRITE_DREAM_STATE);
+
+            final long ident = Binder.clearCallingIdentity();
+            try {
+                DreamManagerService.this.setSystemDreamComponentInternal(componentName);
+            } finally {
+                Binder.restoreCallingIdentity(ident);
+            }
+        }
+
         @Override // Binder call
         public void registerDreamOverlayService(ComponentName overlayComponent) {
             checkPermission(android.Manifest.permission.WRITE_DREAM_STATE);