Place black background only behind nav bar when letterboxed

Placing black background behind the entire app window causes
alpha animation issues, that can be visible as black flash to
user.
This CL sizes and positions the background only behind the
navigation bar area.

Bug: 64598822
Test: Open letterboxed app, go to/from Recents, observe animations.
Change-Id: I16a2243117f87ca513d5ef291b7c1d3779467f3b
(cherry picked from commit 06ab1e14eb343d45f4b51ff41c62a417ee9e5f51)

1 files changed, 56 insertions, 47 deletions

diff --git a/services/core/java/com/android/server/wm/SurfaceControlWithBackground.java b/services/core/java/com/android/server/wm/SurfaceControlWithBackground.java
index ac06c6db4c5c..3603f2ffeed2 100644
--- a/services/core/java/com/android/server/wm/SurfaceControlWithBackground.java
+++ b/services/core/java/com/android/server/wm/SurfaceControlWithBackground.java
@@ -29,12 +29,16 @@ import android.view.SurfaceSession;
 import static android.view.WindowManager.LayoutParams.FIRST_APPLICATION_WINDOW;
 import static android.view.WindowManager.LayoutParams.LAST_APPLICATION_WINDOW;
 import static android.view.WindowManager.LayoutParams.TYPE_APPLICATION_STARTING;
+import static android.view.WindowManagerPolicy.NAV_BAR_BOTTOM;
+import static android.view.WindowManagerPolicy.NAV_BAR_LEFT;
+import static android.view.WindowManagerPolicy.NAV_BAR_RIGHT;
 
 /**
- * SurfaceControl extension that has background sized to match its container.
+ * SurfaceControl extension that has black background behind navigation bar area for fullscreen
+ * letterboxed apps.
  */
 class SurfaceControlWithBackground extends SurfaceControl {
-    // SurfaceControl that holds the background behind opaque letterboxed app windows.
+    // SurfaceControl that holds the background.
     private SurfaceControl mBackgroundControl;
 
     // Flag that defines whether the background should be shown.
@@ -51,8 +55,10 @@ class SurfaceControlWithBackground extends SurfaceControl {
     private float mLastDsDx = 1, mLastDsDy = 1;
     private float mLastX, mLastY;
 
-    // Will skip alpha animation for background of starting window.
-    private boolean mIsStartingWindow;
+    // SurfaceFlinger doesn't support crop rectangles where width or height is non-positive.
+    // If we just set an empty crop it will behave as if there is no crop at all.
+    // To fix this we explicitly hide the surface and won't let it to be shown.
+    private boolean mHiddenForCrop = false;
 
     public SurfaceControlWithBackground(SurfaceControlWithBackground other) {
         super(other);
@@ -76,7 +82,6 @@ class SurfaceControlWithBackground extends SurfaceControl {
         mLastWidth = w;
         mLastHeight = h;
         mWindowSurfaceController.getContainerRect(mTmpContainerRect);
-        mIsStartingWindow = windowType == TYPE_APPLICATION_STARTING;
         mBackgroundControl = new SurfaceControl(s, "Background for - " + name,
                 mTmpContainerRect.width(), mTmpContainerRect.height(), PixelFormat.OPAQUE,
                 flags | SurfaceControl.FX_SURFACE_DIM);
@@ -89,10 +94,7 @@ class SurfaceControlWithBackground extends SurfaceControl {
         if (mBackgroundControl == null) {
             return;
         }
-        // We won't animate alpha for starting window because it will be visible as a flash for user
-        // when fading out to reveal real app window.
-        final float backgroundAlpha = mIsStartingWindow && alpha < 1.f ? 0 : alpha;
-        mBackgroundControl.setAlpha(backgroundAlpha);
+        mBackgroundControl.setAlpha(alpha);
     }
 
     @Override
@@ -146,15 +148,10 @@ class SurfaceControlWithBackground extends SurfaceControl {
         if (mBackgroundControl == null) {
             return;
         }
-        if (crop.width() < mLastWidth || crop.height() < mLastHeight) {
-            // We're animating and cropping window, compute the appropriate crop for background.
-            calculateBgCrop(crop);
-            mBackgroundControl.setWindowCrop(mTmpContainerRect);
-        } else {
-            // When not animating just set crop to container rect.
-            mWindowSurfaceController.getContainerRect(mTmpContainerRect);
-            mBackgroundControl.setWindowCrop(mTmpContainerRect);
-        }
+        calculateBgCrop(crop);
+        mBackgroundControl.setWindowCrop(mTmpContainerRect);
+        mHiddenForCrop = mTmpContainerRect.isEmpty();
+        updateBackgroundVisibility();
     }
 
     @Override
@@ -164,34 +161,24 @@ class SurfaceControlWithBackground extends SurfaceControl {
         if (mBackgroundControl == null) {
             return;
         }
-        if (crop.width() < mLastWidth || crop.height() < mLastHeight) {
-            // We're animating and cropping window, compute the appropriate crop for background.
-            calculateBgCrop(crop);
-            mBackgroundControl.setFinalCrop(mTmpContainerRect);
-        } else {
-            // When not animating just set crop to container rect.
-            mWindowSurfaceController.getContainerRect(mTmpContainerRect);
-            mBackgroundControl.setFinalCrop(mTmpContainerRect);
-        }
+        mWindowSurfaceController.getContainerRect(mTmpContainerRect);
+        mBackgroundControl.setFinalCrop(mTmpContainerRect);
     }
 
-    /** Compute background crop based on current animation progress for main surface control. */
+    /**
+     * Compute background crop based on current animation progress for main surface control and
+     * update {@link #mTmpContainerRect} with new values.
+     */
     private void calculateBgCrop(Rect crop) {
         // Track overall progress of animation by computing cropped portion of status bar.
         final Rect contentInsets = mWindowSurfaceController.mAnimator.mWin.mContentInsets;
         float d = contentInsets.top == 0 ? 0 : (float) crop.top / contentInsets.top;
         if (d > 1.f) {
             // We're running expand animation from launcher, won't compute custom bg crop here.
-            mTmpContainerRect.set(crop);
+            mTmpContainerRect.setEmpty();
             return;
         }
 
-        // Compute additional offset for the background when app window is positioned not at (0,0).
-        // E.g. landscape with navigation bar on the left.
-        final Rect winFrame = mWindowSurfaceController.mAnimator.mWin.mFrame;
-        final int offsetX = (int) (winFrame.left * mLastDsDx * d + 0.5);
-        final int offsetY = (int) (winFrame.top * mLastDsDy * d + 0.5);
-
         // Compute new scaled width and height for background that will depend on current animation
         // progress. Those consist of current crop rect for the main surface + scaled areas outside
         // of letterboxed area.
@@ -201,17 +188,39 @@ class SurfaceControlWithBackground extends SurfaceControl {
         // computing correct frames for letterboxed windows in WindowState.
         d = d < 0.025f ? 0 : d;
         mWindowSurfaceController.getContainerRect(mTmpContainerRect);
-        final int backgroundWidth =
-                (int) (crop.width() + (mTmpContainerRect.width() - mLastWidth) * (1 - d) + 0.5);
-        final int backgroundHeight =
-                (int) (crop.height() + (mTmpContainerRect.height() - mLastHeight) * (1 - d) + 0.5);
-
-        mTmpContainerRect.set(crop);
-        // Make sure that part of background to left/top is visible and scaled.
-        mTmpContainerRect.offset(offsetX, offsetY);
-        // Set correct width/height, so that area to right/bottom is cropped properly.
-        mTmpContainerRect.right = mTmpContainerRect.left + backgroundWidth;
-        mTmpContainerRect.bottom = mTmpContainerRect.top + backgroundHeight;
+        int backgroundWidth = 0, backgroundHeight = 0;
+        // Compute additional offset for the background when app window is positioned not at (0,0).
+        // E.g. landscape with navigation bar on the left.
+        final Rect winFrame = mWindowSurfaceController.mAnimator.mWin.mFrame;
+        int offsetX = (int)((winFrame.left - mTmpContainerRect.left) * mLastDsDx),
+                offsetY = (int) ((winFrame.top - mTmpContainerRect.top) * mLastDsDy);
+
+        // Position and size background.
+        final int bgPosition = mWindowSurfaceController.mAnimator.mService.getNavBarPosition();
+
+        switch (bgPosition) {
+            case NAV_BAR_LEFT:
+                backgroundWidth = (int) ((mTmpContainerRect.width() - mLastWidth) * (1 - d) + 0.5);
+                backgroundHeight = crop.height();
+                offsetX += crop.left - backgroundWidth;
+                offsetY += crop.top;
+                break;
+            case NAV_BAR_RIGHT:
+                backgroundWidth = (int) ((mTmpContainerRect.width() - mLastWidth) * (1 - d) + 0.5);
+                backgroundHeight = crop.height();
+                offsetX += crop.right;
+                offsetY += crop.top;
+                break;
+            case NAV_BAR_BOTTOM:
+                backgroundWidth = crop.width();
+                backgroundHeight = (int) ((mTmpContainerRect.height() - mLastHeight) * (1 - d)
+                        + 0.5);
+                offsetX += crop.left;
+                offsetY += crop.bottom;
+                break;
+        }
+        mTmpContainerRect.set(offsetX, offsetY, offsetX + backgroundWidth,
+                offsetY + backgroundHeight);
     }
 
     @Override
@@ -317,7 +326,7 @@ class SurfaceControlWithBackground extends SurfaceControl {
             return;
         }
         final AppWindowToken appWindowToken = mWindowSurfaceController.mAnimator.mWin.mAppToken;
-        if (appWindowToken != null && appWindowToken.fillsParent() && mVisible) {
+        if (!mHiddenForCrop && mVisible && appWindowToken != null && appWindowToken.fillsParent()) {
             mBackgroundControl.show();
         } else {
             mBackgroundControl.hide();