Use a color container surface to animate rotation with wallpaper

By default, WallpaperService has a 0.05f dim. And SystemUI's
DefaultDeviceEffectsApplier may set 0.6f for battery saver mode.

If the wallpaper surface is not opaque, it may be blending with
the surface behind. E.g.

Before animation starts:
 z=1 Wallpaper 0.6 alpha
 z=0 No other layer (black)

Animation starts:
 z=2 Wallpaper 0.6 alpha <--- looks brighter
 z=1 Bright (assume the content is light color) background layer

Animation ends: (flickering when removing the background layer)
 z=2 Wallpaper 0.6 alpha
 z=0 No other layer (black)

So wrap the surface which contains the wallpaper into a surface
with color that will animate from background color to black, then
the translucent wallpaper can have a smoother transition.

Bug: 326331384
Flag: EXEMPT bugfix
Test: Enable home rotation. Set a white color wallpaper.
      adb shell cmd battery unplug \
        && adb shell settings put global low_power 1
      (or "adb shell cmd wallpaper set-dim-amount 0.5")
      Rotate device.
      The end frame should not flickering from light to dark.
Change-Id: Ie869abf59ecd59c976a503aee14880759f4b42e2
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/DefaultTransitionHandler.java b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/DefaultTransitionHandler.java
index 3a2820ee..1573291 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/DefaultTransitionHandler.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/DefaultTransitionHandler.java
@@ -358,9 +358,12 @@
 
             if (mode == TRANSIT_CHANGE && change.hasFlags(FLAG_IS_DISPLAY)) {
                 if (info.getType() == TRANSIT_CHANGE) {
-                    final int anim = getRotationAnimationHint(change, info, mDisplayController);
+                    int anim = getRotationAnimationHint(change, info, mDisplayController);
                     isSeamlessDisplayChange = anim == ROTATION_ANIMATION_SEAMLESS;
                     if (!(isSeamlessDisplayChange || anim == ROTATION_ANIMATION_JUMPCUT)) {
+                        if (wallpaperTransit != WALLPAPER_TRANSITION_NONE) {
+                            anim |= ScreenRotationAnimation.ANIMATION_HINT_HAS_WALLPAPER;
+                        }
                         startRotationAnimation(startTransaction, change, info, anim, animations,
                                 onAnimFinish);
                         isDisplayRotationAnimationStarted = true;
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/ScreenRotationAnimation.java b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/ScreenRotationAnimation.java
index 5802e2c..b9d11a3 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/ScreenRotationAnimation.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/ScreenRotationAnimation.java
@@ -25,12 +25,9 @@
 import static com.android.wm.shell.transition.Transitions.TAG;
 
 import android.animation.Animator;
-import android.animation.AnimatorListenerAdapter;
-import android.animation.ArgbEvaluator;
 import android.animation.ValueAnimator;
 import android.annotation.NonNull;
 import android.content.Context;
-import android.graphics.Color;
 import android.graphics.Matrix;
 import android.graphics.Rect;
 import android.hardware.HardwareBuffer;
@@ -38,6 +35,7 @@
 import android.view.Surface;
 import android.view.SurfaceControl;
 import android.view.SurfaceControl.Transaction;
+import android.view.animation.AccelerateInterpolator;
 import android.view.animation.Animation;
 import android.view.animation.AnimationUtils;
 import android.window.ScreenCapture;
@@ -74,6 +72,9 @@
  */
 class ScreenRotationAnimation {
     static final int MAX_ANIMATION_DURATION = 10 * 1000;
+    static final int ANIMATION_HINT_HAS_WALLPAPER = 1 << 8;
+    /** It must cover all WindowManager#ROTATION_ANIMATION_*. */
+    private static final int ANIMATION_TYPE_MASK = 0xff;
 
     private final Context mContext;
     private final TransactionPool mTransactionPool;
@@ -81,7 +82,7 @@
     /** The leash of the changing window container. */
     private final SurfaceControl mSurfaceControl;
 
-    private final int mAnimHint;
+    private final int mAnimType;
     private final int mStartWidth;
     private final int mStartHeight;
     private final int mEndWidth;
@@ -98,6 +99,12 @@
     private SurfaceControl mBackColorSurface;
     /** The leash using to animate screenshot layer. */
     private final SurfaceControl mAnimLeash;
+    /**
+     * The container with background color for {@link #mSurfaceControl}. It is only created if
+     * {@link #mSurfaceControl} may be translucent. E.g. visible wallpaper with alpha < 1 (dimmed).
+     * That prevents flickering of alpha blending.
+     */
+    private SurfaceControl mBackEffectSurface;
 
     // The current active animation to move from the old to the new rotated
     // state.  Which animation is run here will depend on the old and new
@@ -115,7 +122,7 @@
             Transaction t, TransitionInfo.Change change, SurfaceControl rootLeash, int animHint) {
         mContext = context;
         mTransactionPool = pool;
-        mAnimHint = animHint;
+        mAnimType = animHint & ANIMATION_TYPE_MASK;
 
         mSurfaceControl = change.getLeash();
         mStartWidth = change.getStartAbsBounds().width();
@@ -170,11 +177,20 @@
                 }
                 hardwareBuffer.close();
             }
+            if ((animHint & ANIMATION_HINT_HAS_WALLPAPER) != 0) {
+                mBackEffectSurface = new SurfaceControl.Builder()
+                        .setCallsite("ShellRotationAnimation").setParent(rootLeash)
+                        .setEffectLayer().setOpaque(true).setName("BackEffect").build();
+                t.reparent(mSurfaceControl, mBackEffectSurface)
+                        .setColor(mBackEffectSurface,
+                                new float[] {mStartLuma, mStartLuma, mStartLuma})
+                        .show(mBackEffectSurface);
+            }
 
             t.setLayer(mAnimLeash, SCREEN_FREEZE_LAYER_BASE);
             t.show(mAnimLeash);
             // Crop the real content in case it contains a larger child layer, e.g. wallpaper.
-            t.setCrop(mSurfaceControl, new Rect(0, 0, mEndWidth, mEndHeight));
+            t.setCrop(getEnterSurface(), new Rect(0, 0, mEndWidth, mEndHeight));
 
             if (!isCustomRotate()) {
                 mBackColorSurface = new SurfaceControl.Builder()
@@ -199,7 +215,12 @@
     }
 
     private boolean isCustomRotate() {
-        return mAnimHint == ROTATION_ANIMATION_CROSSFADE || mAnimHint == ROTATION_ANIMATION_JUMPCUT;
+        return mAnimType == ROTATION_ANIMATION_CROSSFADE || mAnimType == ROTATION_ANIMATION_JUMPCUT;
+    }
+
+    /** Returns the surface which contains the real content to animate enter. */
+    private SurfaceControl getEnterSurface() {
+        return mBackEffectSurface != null ? mBackEffectSurface : mSurfaceControl;
     }
 
     private void setScreenshotTransform(SurfaceControl.Transaction t) {
@@ -260,7 +281,7 @@
         final boolean customRotate = isCustomRotate();
         if (customRotate) {
             mRotateExitAnimation = AnimationUtils.loadAnimation(mContext,
-                    mAnimHint == ROTATION_ANIMATION_JUMPCUT ? R.anim.rotation_animation_jump_exit
+                    mAnimType == ROTATION_ANIMATION_JUMPCUT ? R.anim.rotation_animation_jump_exit
                             : R.anim.rotation_animation_xfade_exit);
             mRotateEnterAnimation = AnimationUtils.loadAnimation(mContext,
                     R.anim.rotation_animation_enter);
@@ -314,7 +335,11 @@
         } else {
             startDisplayRotation(animations, finishCallback, mainExecutor);
             startScreenshotRotationAnimation(animations, finishCallback, mainExecutor);
-            //startColorAnimation(mTransaction, animationScale);
+            if (mBackEffectSurface != null && mStartLuma > 0.1f) {
+                // Animate from the color of background to black for smooth alpha blending.
+                buildLumaAnimation(animations, mStartLuma, 0f /* endLuma */, mBackEffectSurface,
+                        animationScale, finishCallback, mainExecutor);
+            }
         }
 
         return true;
@@ -322,7 +347,7 @@
 
     private void startDisplayRotation(@NonNull ArrayList<Animator> animations,
             @NonNull Runnable finishCallback, @NonNull ShellExecutor mainExecutor) {
-        buildSurfaceAnimation(animations, mRotateEnterAnimation, mSurfaceControl, finishCallback,
+        buildSurfaceAnimation(animations, mRotateEnterAnimation, getEnterSurface(), finishCallback,
                 mTransactionPool, mainExecutor, null /* position */, 0 /* cornerRadius */,
                 null /* clipRect */, false /* isActivity */);
     }
@@ -341,40 +366,17 @@
                 null /* clipRect */, false /* isActivity */);
     }
 
-    private void startColorAnimation(float animationScale, @NonNull ShellExecutor animExecutor) {
-        int colorTransitionMs = mContext.getResources().getInteger(
-                R.integer.config_screen_rotation_color_transition);
-        final float[] rgbTmpFloat = new float[3];
-        final int startColor = Color.rgb(mStartLuma, mStartLuma, mStartLuma);
-        final int endColor = Color.rgb(mEndLuma, mEndLuma, mEndLuma);
-        final long duration = colorTransitionMs * (long) animationScale;
-        final Transaction t = mTransactionPool.acquire();
-
-        final ValueAnimator va = ValueAnimator.ofFloat(0f, 1f);
-        // Animation length is already expected to be scaled.
-        va.overrideDurationScale(1.0f);
-        va.setDuration(duration);
-        va.addUpdateListener(animation -> {
-            final long currentPlayTime = Math.min(va.getDuration(), va.getCurrentPlayTime());
-            final float fraction = currentPlayTime / va.getDuration();
-            applyColor(startColor, endColor, rgbTmpFloat, fraction, mBackColorSurface, t);
-        });
-        va.addListener(new AnimatorListenerAdapter() {
-            @Override
-            public void onAnimationCancel(Animator animation) {
-                applyColor(startColor, endColor, rgbTmpFloat, 1f /* fraction */, mBackColorSurface,
-                        t);
-                mTransactionPool.release(t);
-            }
-
-            @Override
-            public void onAnimationEnd(Animator animation) {
-                applyColor(startColor, endColor, rgbTmpFloat, 1f /* fraction */, mBackColorSurface,
-                        t);
-                mTransactionPool.release(t);
-            }
-        });
-        animExecutor.execute(va::start);
+    private void buildLumaAnimation(@NonNull ArrayList<Animator> animations,
+            float startLuma, float endLuma, SurfaceControl surface, float animationScale,
+            @NonNull Runnable finishCallback, @NonNull ShellExecutor mainExecutor) {
+        final long durationMillis = (long) (mContext.getResources().getInteger(
+                R.integer.config_screen_rotation_color_transition) * animationScale);
+        final LumaAnimation animation = new LumaAnimation(durationMillis);
+        // Align the end with the enter animation.
+        animation.setStartOffset(mRotateEnterAnimation.getDuration() - durationMillis);
+        final LumaAnimationAdapter adapter = new LumaAnimationAdapter(surface, startLuma, endLuma);
+        buildSurfaceAnimation(animations, animation, finishCallback, mTransactionPool,
+                mainExecutor, adapter);
     }
 
     public void kill() {
@@ -389,21 +391,47 @@
         if (mBackColorSurface != null && mBackColorSurface.isValid()) {
             t.remove(mBackColorSurface);
         }
+        if (mBackEffectSurface != null && mBackEffectSurface.isValid()) {
+            t.remove(mBackEffectSurface);
+        }
         t.apply();
         mTransactionPool.release(t);
     }
 
-    private static void applyColor(int startColor, int endColor, float[] rgbFloat,
-            float fraction, SurfaceControl surface, SurfaceControl.Transaction t) {
-        final int color = (Integer) ArgbEvaluator.getInstance().evaluate(fraction, startColor,
-                endColor);
-        Color middleColor = Color.valueOf(color);
-        rgbFloat[0] = middleColor.red();
-        rgbFloat[1] = middleColor.green();
-        rgbFloat[2] = middleColor.blue();
-        if (surface.isValid()) {
-            t.setColor(surface, rgbFloat);
+    /** A no-op wrapper to provide animation duration. */
+    private static class LumaAnimation extends Animation {
+        LumaAnimation(long durationMillis) {
+            setDuration(durationMillis);
         }
-        t.apply();
+    }
+
+    private static class LumaAnimationAdapter extends DefaultTransitionHandler.AnimationAdapter {
+        final float[] mColorArray = new float[3];
+        final float mStartLuma;
+        final float mEndLuma;
+        final AccelerateInterpolator mInterpolation;
+
+        LumaAnimationAdapter(@NonNull SurfaceControl leash, float startLuma, float endLuma) {
+            super(leash);
+            mStartLuma = startLuma;
+            mEndLuma = endLuma;
+            // Make the initial progress color lighter if the background is light. That avoids
+            // darker content when fading into the entering surface.
+            final float factor = Math.min(3f, (Math.max(0.5f, mStartLuma) - 0.5f) * 10);
+            Slog.d(TAG, "Luma=" + mStartLuma + " factor=" + factor);
+            mInterpolation = factor > 0.5f ? new AccelerateInterpolator(factor) : null;
+        }
+
+        @Override
+        void applyTransformation(ValueAnimator animator) {
+            final float fraction = mInterpolation != null
+                    ? mInterpolation.getInterpolation(animator.getAnimatedFraction())
+                    : animator.getAnimatedFraction();
+            final float luma = mStartLuma + fraction * (mEndLuma - mStartLuma);
+            mColorArray[0] = luma;
+            mColorArray[1] = luma;
+            mColorArray[2] = luma;
+            mTransaction.setColor(mLeash, mColorArray);
+        }
     }
 }