BackgroundFallback: Cover all cases where the fallback is needed

Fixes an issue where uncovered regions were not
covered if they are to the right or bottom of the
content view.

Fixes: 78661186
Test: Install test app from bug, enable cuotut, open test app, go to landscape, verify white fallback background is drawn in both landscape and seascape
Test: atest BackgroundFallbackTest
Change-Id: I442f03395a71550a534d64233762aa84002319dd

2 files changed, 77 insertions, 11 deletions

diff --git a/core/java/com/android/internal/policy/DecorView.java b/core/java/com/android/internal/policy/DecorView.java
index eadefc919934..cfc5c4cebea9 100644
--- a/core/java/com/android/internal/policy/DecorView.java
+++ b/core/java/com/android/internal/policy/DecorView.java
@@ -310,10 +310,8 @@ public class DecorView extends FrameLayout implements RootViewSurfaceTaker, Wind
     public void onDraw(Canvas c) {
         super.onDraw(c);
 
-        // When we are resizing, we need the fallback background to cover the area where we have our
-        // system bar background views as the navigation bar will be hidden during resizing.
-        mBackgroundFallback.draw(isResizing() ? this : mContentRoot, mContentRoot, c,
-                mWindow.mContentParent);
+        mBackgroundFallback.draw(this, mContentRoot, c, mWindow.mContentParent,
+                mStatusColorViewState.view, mNavigationColorViewState.view);
     }
 
     @Override
diff --git a/core/java/com/android/internal/widget/BackgroundFallback.java b/core/java/com/android/internal/widget/BackgroundFallback.java
index 309f80cb0d52..2b05f1ecbc70 100644
--- a/core/java/com/android/internal/widget/BackgroundFallback.java
+++ b/core/java/com/android/internal/widget/BackgroundFallback.java
@@ -46,8 +46,11 @@ public class BackgroundFallback {
      * @param root The view group containing the content.
      * @param c The canvas to draw the background onto.
      * @param content The view where the actual app content is contained in.
+     * @param coveringView1 A potentially opaque view drawn atop the content
+     * @param coveringView2 A potentially opaque view drawn atop the content
      */
-    public void draw(ViewGroup boundsView, ViewGroup root, Canvas c, View content) {
+    public void draw(ViewGroup boundsView, ViewGroup root, Canvas c, View content,
+            View coveringView1, View coveringView2) {
         if (!hasFallback()) {
             return;
         }
@@ -55,6 +58,10 @@ public class BackgroundFallback {
         // Draw the fallback in the padding.
         final int width = boundsView.getWidth();
         final int height = boundsView.getHeight();
+
+        final int rootOffsetX = root.getLeft();
+        final int rootOffsetY = root.getTop();
+
         int left = width;
         int top = height;
         int right = 0;
@@ -71,17 +78,58 @@ public class BackgroundFallback {
                         ((ViewGroup) child).getChildCount() == 0) {
                     continue;
                 }
-            } else if (child.getVisibility() != View.VISIBLE || childBg == null ||
-                    childBg.getOpacity() != PixelFormat.OPAQUE) {
+            } else if (child.getVisibility() != View.VISIBLE || !isOpaque(childBg)) {
                 // Potentially translucent or invisible children don't count, and we assume
                 // the content view will cover the whole area if we're in a background
                 // fallback situation.
                 continue;
             }
-            left = Math.min(left, child.getLeft());
-            top = Math.min(top, child.getTop());
-            right = Math.max(right, child.getRight());
-            bottom = Math.max(bottom, child.getBottom());
+            left = Math.min(left, rootOffsetX + child.getLeft());
+            top = Math.min(top, rootOffsetY + child.getTop());
+            right = Math.max(right, rootOffsetX + child.getRight());
+            bottom = Math.max(bottom, rootOffsetY + child.getBottom());
+        }
+
+        // If one of the bar backgrounds is a solid color and covers the entire padding on a side
+        // we can drop that padding.
+        boolean eachBarCoversTopInY = true;
+        for (int i = 0; i < 2; i++) {
+            View v = (i == 0) ? coveringView1 : coveringView2;
+            if (v == null || v.getVisibility() != View.VISIBLE
+                    || v.getAlpha() != 1f || !isOpaque(v.getBackground())) {
+                eachBarCoversTopInY = false;
+                continue;
+            }
+
+            // Bar covers entire left padding
+            if (v.getTop() <= 0 && v.getBottom() >= height
+                    && v.getLeft() <= 0 && v.getRight() >= left) {
+                left = 0;
+            }
+            // Bar covers entire right padding
+            if (v.getTop() <= 0 && v.getBottom() >= height
+                    && v.getLeft() <= right && v.getRight() >= width) {
+                right = width;
+            }
+            // Bar covers entire top padding
+            if (v.getTop() <= 0 && v.getBottom() >= top
+                    && v.getLeft() <= 0 && v.getRight() >= width) {
+                top = 0;
+            }
+            // Bar covers entire bottom padding
+            if (v.getTop() <= bottom && v.getBottom() >= height
+                    && v.getLeft() <= 0 && v.getRight() >= width) {
+                bottom = height;
+            }
+
+            eachBarCoversTopInY &= v.getTop() <= 0 && v.getBottom() >= top;
+        }
+
+        // Special case: Sometimes, both covering views together may cover the top inset, but
+        // neither does on its own.
+        if (eachBarCoversTopInY && (viewsCoverEntireWidth(coveringView1, coveringView2, width)
+                || viewsCoverEntireWidth(coveringView2, coveringView1, width))) {
+            top = 0;
         }
 
         if (left >= right || top >= bottom) {
@@ -106,4 +154,24 @@ public class BackgroundFallback {
             mBackgroundFallback.draw(c);
         }
     }
+
+    private boolean isOpaque(Drawable childBg) {
+        return childBg != null && childBg.getOpacity() == PixelFormat.OPAQUE;
+    }
+
+    /**
+     * Returns true if {@code view1} starts before or on {@code 0} and extends at least
+     * up to {@code view2}, and that view extends at least to {@code width}.
+     *
+     * @param view1 the first view to check if it covers the width
+     * @param view2 the second view to check if it covers the width
+     * @param width the width to check for
+     * @return returns true if both views together cover the entire width (and view1 is to the left
+     *         of view2)
+     */
+    private boolean viewsCoverEntireWidth(View view1, View view2, int width) {
+        return view1.getLeft() <= 0
+                && view1.getRight() >= view2.getLeft()
+                && view2.getRight() >= width;
+    }
 }