Events for window's content change should be dispatched only for the active window.

1. Accessibility events for changes in the content of a given window, such as
   click, focus, etc. are dispatched to clients only if they come from the
   active window.

   Events for changes in the state of a window, such as window got input focus
   or a notification appeared, are always dispatched. The notification events
   do not contain source, so a client cannot introspect the notification area
   (unless the user explicitly touches it which generates hove events). The
   events for a window getting input focus change the active window so they
   have to be dispatched.

   Events that are a result of the user touching the screen, such as hover
   enter, first tocuh, etc. should always be dispatched.

bug:7282006

Change-Id: I96b79189f8571285175d9660a22394cc84f39559

Author: sganov

services/java/com/android/server/accessibility/AccessibilityManagerService.java

@@ -2134,9 +2134,30 @@ final class SecurityPolicy {
         private int mActiveWindowId;
 
         private boolean canDispatchAccessibilityEvent(AccessibilityEvent event) {
-            // Send window changed event only for the retrieval allowing window.
-            return (event.getEventType() != AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED
-                    || event.getWindowId() == mActiveWindowId);
+            final int eventType = event.getEventType();
+            switch (eventType) {
+                // All events that are for changes in a global window
+                // state should *always* be dispatched.
+                case AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED:
+                case AccessibilityEvent.TYPE_NOTIFICATION_STATE_CHANGED:
+                // All events generated by the user touching the
+                // screen should *always* be dispatched.
+                case AccessibilityEvent.TYPE_TOUCH_EXPLORATION_GESTURE_START:
+                case AccessibilityEvent.TYPE_TOUCH_EXPLORATION_GESTURE_END:
+                case AccessibilityEvent.TYPE_GESTURE_DETECTION_START:
+                case AccessibilityEvent.TYPE_GESTURE_DETECTION_END:
+                case AccessibilityEvent.TYPE_TOUCH_INTERACTION_START:
+                case AccessibilityEvent.TYPE_TOUCH_INTERACTION_END:
+                // These will change the active window, so dispatch.
+                case AccessibilityEvent.TYPE_VIEW_HOVER_ENTER:
+                case AccessibilityEvent.TYPE_VIEW_HOVER_EXIT: {
+                    return true;
+                }
+                // All events for changes in window content should be
+                // dispatched *only* if this window is the active one.
+                default:
+                    return event.getWindowId() == mActiveWindowId;
+            }
         }
 
         public void updateEventSourceLocked(AccessibilityEvent event) {