View's visibility to the user not checking predecessor alpha.

1. A view is visible to the user if is attached to a visible window,
   its visibility is VISIBLE, its alpha is not zero, all its
   predecessors have visibility VISIBLE and non zero alpha, the
   view is not fully covered by predecessors and is within the
   screen.

   The function that computes whether a view is visible for
   accessibility purposes was not taking into account the
   predecessors' alpha.

bug:7454355

Change-Id: I7609f4366da260091d68e5b25832498843fd3d0a

Author: sganov

core/java/android/view/View.java

@@ -5088,24 +5088,35 @@ protected boolean isVisibleToUser() {
      */
     protected boolean isVisibleToUser(Rect boundInView) {
         if (mAttachInfo != null) {
+            // Attached to invisible window means this view is not visible.
+            if (mAttachInfo.mWindowVisibility != View.VISIBLE) {
+                return false;
+            }
+            // An invisible predecessor or one with alpha zero means
+            // that this view is not visible to the user.
+            Object current = this;
+            while (current instanceof View) {
+                View view = (View) current;
+                // We have attach info so this view is attached and there is no
+                // need to check whether we reach to ViewRootImpl on the way up.
+                if (view.getAlpha() <= 0 || view.getVisibility() != VISIBLE) {
+                    return false;
+                }
+                current = view.mParent;
+            }
+            // Check if the view is entirely covered by its predecessors.
             Rect visibleRect = mAttachInfo.mTmpInvalRect;
             Point offset = mAttachInfo.mPoint;
-            // The first two checks are made also made by isShown() which
-            // however traverses the tree up to the parent to catch that.
-            // Therefore, we do some fail fast check to minimize the up
-            // tree traversal.
-            boolean isVisible = mAttachInfo.mWindowVisibility == View.VISIBLE
-                && getAlpha() > 0
-                && isShown()
-                && getGlobalVisibleRect(visibleRect, offset);
-            if (isVisible && boundInView != null) {
+            if (!getGlobalVisibleRect(visibleRect, offset)) {
+                return false;
+            }
+            // Check if the visible portion intersects the rectangle of interest.
+            if (boundInView != null) {
                 visibleRect.offset(-offset.x, -offset.y);
-                // isVisible is always true here, use a simple assignment
-                isVisible = boundInView.intersect(visibleRect);
+                return boundInView.intersect(visibleRect);
             }
-            return isVisible;
+            return true;
         }
-
         return false;
     }