Merge "Use saved window surface to start entering animation"
diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index 98cfc7c..7e47006 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -2876,13 +2876,16 @@
         }
 
         if (stackId != task.stack.mStackId) {
-            moveTaskToStackUncheckedLocked(task, stackId, ON_TOP, FORCE_FOCUS, reason);
-        } else {
-            task.stack.moveTaskToFrontLocked(task, false /* noAnimation */, options,
-                task.getTopActivity() == null ? null : task.getTopActivity().appTimeTracker,
-                reason);
+            moveTaskToStackUncheckedLocked(task, stackId, ON_TOP, !FORCE_FOCUS, reason);
+
+            // moveTaskToStackUncheckedLocked() should already placed the task on top,
+            // still need moveTaskToFrontLocked() below for any transition settings.
         }
 
+        final ActivityRecord r = task.getTopActivity();
+        task.stack.moveTaskToFrontLocked(task, false /* noAnimation */, options,
+                r == null ? null : r.appTimeTracker, reason);
+
         if (DEBUG_STACK) Slog.d(TAG_STACK,
                 "findTaskToMoveToFront: moved to front of stack=" + task.stack);
     }
diff --git a/services/core/java/com/android/server/wm/AppWindowAnimator.java b/services/core/java/com/android/server/wm/AppWindowAnimator.java
index bf7063f..a61e83f 100644
--- a/services/core/java/com/android/server/wm/AppWindowAnimator.java
+++ b/services/core/java/com/android/server/wm/AppWindowAnimator.java
@@ -300,7 +300,8 @@
                 return false;
             }
 
-            if ((mAppToken.allDrawn || animating || mAppToken.startingDisplayed)
+            if ((mAppToken.allDrawn || mAppToken.mAnimatingWithSavedSurface
+                    || animating || mAppToken.startingDisplayed)
                     && animation != null) {
                 if (!animating) {
                     if (DEBUG_ANIM) Slog.v(TAG,
diff --git a/services/core/java/com/android/server/wm/AppWindowToken.java b/services/core/java/com/android/server/wm/AppWindowToken.java
index d18c854..943e3ea 100644
--- a/services/core/java/com/android/server/wm/AppWindowToken.java
+++ b/services/core/java/com/android/server/wm/AppWindowToken.java
@@ -52,6 +52,13 @@
 
     final boolean voiceInteraction;
 
+    // Whether the window has a saved surface from last pause, which can be
+    // used to start an entering animation earlier.
+    boolean mHasSavedSurface;
+
+    // Whether we're performing an entering animation with a saved surface.
+    boolean mAnimatingWithSavedSurface;
+
     Task mTask;
     boolean appFullscreen;
     int requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED;
@@ -260,10 +267,13 @@
         final int N = allAppWindows.size();
         for (int i=0; i<N; i++) {
             WindowState win = allAppWindows.get(i);
+            // If we're animating with a saved surface, we're already visible.
+            // Return true so that the alpha doesn't get cleared.
             if (!win.mAppFreezing
-                    && (win.mViewVisibility == View.VISIBLE ||
-                        (win.mWinAnimator.isAnimating() &&
-                                !service.mAppTransition.isTransitionSet()))
+                    && (win.mViewVisibility == View.VISIBLE
+                    || mAnimatingWithSavedSurface
+                    || (win.mWinAnimator.isAnimating() &&
+                            !service.mAppTransition.isTransitionSet()))
                     && !win.mDestroying && win.isDrawnLw()) {
                 return true;
             }
diff --git a/services/core/java/com/android/server/wm/Task.java b/services/core/java/com/android/server/wm/Task.java
index 6527881..4d11452 100644
--- a/services/core/java/com/android/server/wm/Task.java
+++ b/services/core/java/com/android/server/wm/Task.java
@@ -18,6 +18,7 @@
 
 import static android.app.ActivityManager.DOCKED_STACK_ID;
 import static android.app.ActivityManager.FREEFORM_WORKSPACE_STACK_ID;
+import static android.app.ActivityManager.HOME_STACK_ID;
 import static android.app.ActivityManager.PINNED_STACK_ID;
 import static android.app.ActivityManager.RESIZE_MODE_SYSTEM_SCREEN_ROTATION;
 import static com.android.server.wm.WindowManagerService.TAG;
@@ -324,6 +325,10 @@
         return (tokensCount != 0) && mAppTokens.get(tokensCount - 1).showForAllUsers;
     }
 
+    boolean inHomeStack() {
+        return mStack != null && mStack.mStackId == HOME_STACK_ID;
+    }
+
     boolean inFreeformWorkspace() {
         return mStack != null && mStack.mStackId == FREEFORM_WORKSPACE_STACK_ID;
     }
diff --git a/services/core/java/com/android/server/wm/WindowAnimator.java b/services/core/java/com/android/server/wm/WindowAnimator.java
index 928a117..be86e2f 100644
--- a/services/core/java/com/android/server/wm/WindowAnimator.java
+++ b/services/core/java/com/android/server/wm/WindowAnimator.java
@@ -413,7 +413,7 @@
 
             final AppWindowToken atoken = win.mAppToken;
             if (winAnimator.mDrawState == WindowStateAnimator.READY_TO_SHOW) {
-                if (atoken == null || atoken.allDrawn) {
+                if (atoken == null || atoken.allDrawn || atoken.mAnimatingWithSavedSurface) {
                     if (winAnimator.performShowLocked()) {
                         setPendingLayoutChanges(displayId,
                                 WindowManagerPolicy.FINISH_LAYOUT_REDO_ANIM);
diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index e3e3693..8a2442a 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -2687,9 +2687,16 @@
                 if (winAnimator.mSurfaceControl != null) {
                     if (DEBUG_VISIBILITY) Slog.i(TAG, "Relayout invis " + win
                             + ": mExiting=" + win.mExiting);
+                    // If we are using a saved surface to do enter animation, just let the
+                    // animation run and don't destroy the surface. This could happen when
+                    // the app sets visibility to invisible for the first time after resume,
+                    // or when the user exits immediately after a resume. In both cases, we
+                    // don't want to destroy the saved surface.
+                    final boolean isAnimatingWithSavedSurface =
+                            win.mAppToken != null && win.mAppToken.mAnimatingWithSavedSurface;
                     // If we are not currently running the exit animation, we
                     // need to see about starting one.
-                    if (!win.mExiting) {
+                    if (!win.mExiting && !isAnimatingWithSavedSurface) {
                         surfaceChanged = true;
                         // Try starting an animation; if there isn't one, we
                         // can destroy the surface right away.
@@ -2848,6 +2855,12 @@
                         getDefaultDisplayContentLocked().pendingLayoutChanges |=
                                 WindowManagerPolicy.FINISH_LAYOUT_REDO_WALLPAPER;
                     }
+                    if (win.mAppToken != null) {
+                        // App has drawn something to its windows, we're no longer animating with
+                        // the saved surfaces. If the user exits now, we only want to save again
+                        // if allDrawn is true.
+                        win.mAppToken.mAnimatingWithSavedSurface = false;
+                    }
                     win.setDisplayLayoutNeeded();
                     mWindowPlacerLocked.requestTraversal();
                 }
diff --git a/services/core/java/com/android/server/wm/WindowState.java b/services/core/java/com/android/server/wm/WindowState.java
index 42a0e9d..e9ea3a8 100644
--- a/services/core/java/com/android/server/wm/WindowState.java
+++ b/services/core/java/com/android/server/wm/WindowState.java
@@ -36,6 +36,7 @@
 import static com.android.server.wm.WindowManagerService.DEBUG_RESIZE;
 import static com.android.server.wm.WindowManagerService.DEBUG_VISIBILITY;
 
+import android.app.ActivityManager;
 import android.app.AppOpsManager;
 import android.graphics.Point;
 import android.os.PowerManager;
@@ -1504,6 +1505,31 @@
         return mExiting || (mService.mClosingApps.contains(mAppToken));
     }
 
+    boolean saveSurfaceIfNeeded() {
+        if (ActivityManager.isLowRamDeviceStatic()) {
+            // Don't save surfaces on Svelte devices.
+            return false;
+        }
+
+        Task task = getTask();
+        if (task == null || task.inHomeStack()) {
+            // Don't save surfaces for home stack apps. These usually resume and draw
+            // first frame very fast. Saving surfaces are mostly a waste of memory.
+            return false;
+        }
+
+        // We want to save surface if the app's windows are "allDrawn", or if we're
+        // currently animating with save surfaces. (If the app didn't even finish
+        // drawing when the user exits, but we have a saved surface from last time,
+        // we still want to keep that surface.)
+        if (mAppToken.allDrawn || mAppToken.mAnimatingWithSavedSurface) {
+            mAppToken.mHasSavedSurface = true;
+            return true;
+        }
+
+        return false;
+    }
+
     @Override
     public boolean isDefaultDisplay() {
         final DisplayContent displayContent = getDisplayContent();
diff --git a/services/core/java/com/android/server/wm/WindowStateAnimator.java b/services/core/java/com/android/server/wm/WindowStateAnimator.java
index 9344b8d..68c39ba 100644
--- a/services/core/java/com/android/server/wm/WindowStateAnimator.java
+++ b/services/core/java/com/android/server/wm/WindowStateAnimator.java
@@ -535,6 +535,7 @@
             mDrawState = COMMIT_DRAW_PENDING;
             return true;
         }
+
         return false;
     }
 
@@ -554,7 +555,8 @@
         mDrawState = READY_TO_SHOW;
         boolean result = false;
         final AppWindowToken atoken = mWin.mAppToken;
-        if (atoken == null || atoken.allDrawn || mWin.mAttrs.type == TYPE_APPLICATION_STARTING) {
+        if (atoken == null || atoken.allDrawn || atoken.mAnimatingWithSavedSurface ||
+                mWin.mAttrs.type == TYPE_APPLICATION_STARTING) {
             result = performShowLocked();
         }
         if (mDestroyPreservedSurfaceUponRedraw && result) {
@@ -995,12 +997,16 @@
     }
 
     void destroySurfaceLocked() {
-        if (mWin.mAppToken != null && mWin == mWin.mAppToken.startingWindow) {
-            mWin.mAppToken.startingDisplayed = false;
+        final AppWindowToken wtoken = mWin.mAppToken;
+        if (wtoken != null) {
+            wtoken.mHasSavedSurface = false;
+            wtoken.mAnimatingWithSavedSurface = false;
+            if (mWin == wtoken.startingWindow) {
+                wtoken.startingDisplayed = false;
+            }
         }
 
         if (mSurfaceControl != null) {
-
             int i = mWin.mChildWindows.size();
             while (i > 0) {
                 i--;
diff --git a/services/core/java/com/android/server/wm/WindowSurfacePlacer.java b/services/core/java/com/android/server/wm/WindowSurfacePlacer.java
index 0c004b2..e2f4dd9 100644
--- a/services/core/java/com/android/server/wm/WindowSurfacePlacer.java
+++ b/services/core/java/com/android/server/wm/WindowSurfacePlacer.java
@@ -17,6 +17,7 @@
 import static android.view.WindowManagerPolicy.FINISH_LAYOUT_REDO_WALLPAPER;
 import static com.android.server.wm.WindowManagerService.DEBUG;
 import static com.android.server.wm.WindowManagerService.DEBUG_ADD_REMOVE;
+import static com.android.server.wm.WindowManagerService.DEBUG_ANIM;
 import static com.android.server.wm.WindowManagerService.DEBUG_APP_TRANSITIONS;
 import static com.android.server.wm.WindowManagerService.DEBUG_LAYOUT;
 import static com.android.server.wm.WindowManagerService.DEBUG_LAYOUT_REPEATS;
@@ -340,6 +341,10 @@
                 // Don't remove this window until rotation has completed.
                 continue;
             }
+            // Discard the saved surface if window size is changed, it can't be reused.
+            if (win.mAppToken != null && win.mAppToken.mHasSavedSurface) {
+                win.mWinAnimator.destroySurfaceLocked();
+            }
             win.reportResized();
             mService.mResizingWindows.remove(i);
         }
@@ -371,7 +376,9 @@
                 if (mWallpaperControllerLocked.isWallpaperTarget(win)) {
                     wallpaperDestroyed = true;
                 }
-                win.mWinAnimator.destroySurfaceLocked();
+                if (!win.saveSurfaceIfNeeded()) {
+                    win.mWinAnimator.destroySurfaceLocked();
+                }
             } while (i > 0);
             mService.mDestroySurface.clear();
         }
@@ -1174,6 +1181,18 @@
                 }
             }
             createThumbnailAppAnimator(transit, wtoken, topOpeningLayer, topClosingLayer);
+
+            if (wtoken.mHasSavedSurface) {
+                if (DEBUG_APP_TRANSITIONS || DEBUG_ANIM) Slog.v(TAG,
+                        "Early start of animation: " + wtoken + ", allDrawn=" + wtoken.allDrawn);
+
+                for (int j = 0; j < wtoken.windows.size(); j++) {
+                    WindowState ws = wtoken.windows.get(j);
+                    ws.mWinAnimator.mDrawState = WindowStateAnimator.READY_TO_SHOW;
+                }
+                wtoken.mHasSavedSurface = false;
+                wtoken.mAnimatingWithSavedSurface = true;
+            }
         }
 
         AppWindowAnimator openingAppAnimator = (topOpeningApp == null) ?  null :
@@ -1219,6 +1238,10 @@
                         + wtoken.allDrawn + " startingDisplayed="
                         + wtoken.startingDisplayed + " startingMoved="
                         + wtoken.startingMoved);
+
+                if (wtoken.mHasSavedSurface || wtoken.mAnimatingWithSavedSurface) {
+                    continue;
+                }
                 if (!wtoken.allDrawn && !wtoken.startingDisplayed && !wtoken.startingMoved) {
                     return false;
                 }