Android a11y WINDOW_CONTENT_CHANGED event suppression tests

This CL is an follow-up to: crrev.com/c/2552897

In this CL we add on to the event suppression logic for events
of TYPE_WINDOW_CONTENT_CHANGED type on Android.

With this CL we move the logic into web_contents_accessibility_android,
and we add unit tests. We include a VisibleForTesting method in
WebContentsAccessibilityImpl that allows us to change the
suppression threshold as needed.

AX-Relnotes: N/A
Change-Id: Iba5f332ddc4d0a9889f188d7f2a9583bec144ae0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2575422Reviewed-by: Mark Schillaci <mschillaci@google.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Mark Schillaci <mschillaci@google.com>
Cr-Commit-Position: refs/heads/master@{#838942}

content/browser/accessibility/browser_accessibility_manager_android.cc

@@ -15,12 +15,6 @@
 
 namespace content {
 
-namespace {
-// The maximum number of TYPE_WINDOW_CONTENT_CHANGED events to fire in one
-// atomic update before we give up and fire it on the root node instead.
-constexpr int kMaxContentChangedEventsToFire = 5;
-}  // namespace
-
 // static
 BrowserAccessibilityManager* BrowserAccessibilityManager::Create(
     const ui::AXTreeUpdate& initial_tree,
@@ -201,27 +195,9 @@ void BrowserAccessibilityManagerAndroid::FireGeneratedEvent(
 
   // Always send AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED to notify
   // the Android system that the accessibility hierarchy rooted at this
-  // node has changed. However, if there are a large number of changes
-  // it's too expensive to fire all of them, so we just fire one
-  // on the root instead.
-  if (event_type != ui::AXEventGenerator::Event::SUBTREE_CREATED) {
-    content_changed_events_++;
-    if (content_changed_events_ < kMaxContentChangedEventsToFire) {
-      // If it's less than the max event count, fire the event on the specific
-      // node that changed.
-      wcax->HandleContentChanged(android_node->unique_id());
-    } else if (content_changed_events_ == kMaxContentChangedEventsToFire) {
-      // If it's equal to the max event count, fire the event on the
-      // root instead.
-      BrowserAccessibilityManager* root_manager = GetRootManager();
-      if (root_manager) {
-        auto* root_node =
-            static_cast<BrowserAccessibilityAndroid*>(root_manager->GetRoot());
-        if (root_node)
-          wcax->HandleContentChanged(root_node->unique_id());
-      }
-    }
-  }
+  // node has changed.
+  if (event_type != ui::AXEventGenerator::Event::SUBTREE_CREATED)
+    wcax->HandleContentChanged(android_node->unique_id());
 
   switch (event_type) {
     case ui::AXEventGenerator::Event::ALERT: {
@@ -529,16 +505,17 @@ void BrowserAccessibilityManagerAndroid::OnAtomicUpdateFinished(
     ui::AXTree* tree,
     bool root_changed,
     const std::vector<ui::AXTreeObserver::Change>& changes) {
-  // Reset this every time we get an atomic update.
-  content_changed_events_ = 0;
-
   BrowserAccessibilityManager::OnAtomicUpdateFinished(tree, root_changed,
                                                       changes);
 
+  WebContentsAccessibilityAndroid* wcax = GetWebContentsAXFromRootManager();
+  if (!wcax)
+    return;
+
+  // Reset content changed events counter every time we finish an atomic update.
+  wcax->ResetContentChangedEventsCounter();
+
   if (root_changed) {
-    WebContentsAccessibilityAndroid* wcax = GetWebContentsAXFromRootManager();
-    if (!wcax)
-      return;
     wcax->HandleNavigate();
   }
 }

content/browser/accessibility/browser_accessibility_manager_android.h

@@ -134,10 +134,6 @@ class CONTENT_EXPORT BrowserAccessibilityManagerAndroid
   // See docs for set_prune_tree_for_screen_reader, above.
   bool prune_tree_for_screen_reader_;
 
-  // A count of the number of TYPE_WINDOW_CONTENT_CHANGED events we've
-  // fired during a single atomic update.
-  int content_changed_events_ = 0;
-
   DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityManagerAndroid);
 };
 

content/browser/accessibility/web_contents_accessibility_android.cc

@@ -446,7 +446,27 @@ void WebContentsAccessibilityAndroid::HandleContentChanged(int32_t unique_id) {
   ScopedJavaLocalRef<jobject> obj = java_ref_.get(env);
   if (obj.is_null())
     return;
-  Java_WebContentsAccessibilityImpl_handleContentChanged(env, obj, unique_id);
+
+  // If there are a large number of changes it's too expensive to fire all of
+  // them, so we just fire one on the root instead.
+  content_changed_events_++;
+  if (content_changed_events_ < max_content_changed_events_to_fire_) {
+    // If it's less than the max event count, fire the event on the specific
+    // node that changed.
+    Java_WebContentsAccessibilityImpl_handleContentChanged(env, obj, unique_id);
+  } else if (content_changed_events_ == max_content_changed_events_to_fire_) {
+    // If it's equal to the max event count, fire the event on the
+    // root instead.
+    auto* root_manager = GetRootBrowserAccessibilityManager();
+    if (root_manager) {
+      auto* root_node =
+          static_cast<BrowserAccessibilityAndroid*>(root_manager->GetRoot());
+      if (root_node) {
+        Java_WebContentsAccessibilityImpl_handleContentChanged(
+            env, obj, root_node->unique_id());
+      }
+    }
+  }
 }
 
 void WebContentsAccessibilityAndroid::HandleFocusChanged(int32_t unique_id) {

content/browser/accessibility/web_contents_accessibility_android.h

@@ -17,6 +17,12 @@ class MotionEventAndroid;
 
 namespace content {
 
+namespace {
+// The maximum number of TYPE_WINDOW_CONTENT_CHANGED events to fire in one
+// atomic update before we give up and fire it on the root node instead.
+constexpr int kMaxContentChangedEventsToFire = 5;
+}  // namespace
+
 class BrowserAccessibilityAndroid;
 class BrowserAccessibilityManagerAndroid;
 class WebContents;
@@ -248,6 +254,27 @@ class CONTENT_EXPORT WebContentsAccessibilityAndroid
 
   void UpdateFrameInfo(float page_scale);
 
+  // Set a new max for TYPE_WINDOW_CONTENT_CHANGED events to fire.
+  void SetMaxContentChangedEventsToFireForTesting(
+      JNIEnv* env,
+      const base::android::JavaParamRef<jobject>& obj,
+      jint maxEvents) {
+    // Consider a new |maxEvents| value of -1 to mean to reset to the default.
+    if (maxEvents == -1) {
+      max_content_changed_events_to_fire_ = kMaxContentChangedEventsToFire;
+    } else {
+      max_content_changed_events_to_fire_ = maxEvents;
+    }
+  }
+
+  // Get the current max for TYPE_WINDOW_CONTENT_CHANGED events to fire.
+  jint GetMaxContentChangedEventsToFireForTesting(JNIEnv* env) {
+    return max_content_changed_events_to_fire_;
+  }
+
+  // Reset count of content changed events fired this atomic update.
+  void ResetContentChangedEventsCounter() { content_changed_events_ = 0; }
+
   // --------------------------------------------------------------------------
   // Methods called from the BrowserAccessibilityManager
   // --------------------------------------------------------------------------
@@ -297,6 +324,13 @@ class CONTENT_EXPORT WebContentsAccessibilityAndroid
 
   bool use_zoom_for_dsf_enabled_;
 
+  // Current max number of events to fire, mockable for unit tests
+  int max_content_changed_events_to_fire_ = kMaxContentChangedEventsToFire;
+
+  // A count of the number of TYPE_WINDOW_CONTENT_CHANGED events we've
+  // fired during a single atomic update.
+  int content_changed_events_ = 0;
+
   // Manages the connection between web contents and the RenderFrameHost that
   // receives accessibility events.
   // Owns itself, and destroyed upon WebContentsObserver::WebContentsDestroyed.

content/public/android/java/src/org/chromium/content/browser/accessibility/WebContentsAccessibilityImpl.java

@@ -338,6 +338,18 @@ public class WebContentsAccessibilityImpl extends AccessibilityNodeProvider
                 WebContentsAccessibilityImpl.this, virtualViewId, startOffset, endOffset);
     }
 
+    @VisibleForTesting
+    public void setMaxContentChangedEventsToFireForTesting(int maxEvents) {
+        WebContentsAccessibilityImplJni.get().setMaxContentChangedEventsToFireForTesting(
+                mNativeObj, WebContentsAccessibilityImpl.this, maxEvents);
+    }
+
+    @VisibleForTesting
+    public int getMaxContentChangedEventsToFireForTesting() {
+        return WebContentsAccessibilityImplJni.get().getMaxContentChangedEventsToFireForTesting(
+                mNativeObj);
+    }
+
     // WindowEventObserver
 
     @Override
@@ -2010,5 +2022,8 @@ public class WebContentsAccessibilityImpl extends AccessibilityNodeProvider
                 WebContentsAccessibilityImpl caller, int id);
         void addSpellingErrorForTesting(long nativeWebContentsAccessibilityAndroid,
                 WebContentsAccessibilityImpl caller, int id, int startOffset, int endOffset);
+        void setMaxContentChangedEventsToFireForTesting(long nativeWebContentsAccessibilityAndroid,
+                WebContentsAccessibilityImpl caller, int maxEvents);
+        int getMaxContentChangedEventsToFireForTesting(long nativeWebContentsAccessibilityAndroid);
     }
 }

content/test/data/android/type_window_content_changed_events.html

+<!-- Simple file to generate many TYPE_WINDOW_CONTENT_CHANGED events. -->
+<html>
+  <head>
+    <script>
+      const SCRIPT_COUNT = 250;
+      var elementArray = [];
+
+      function expandComboboxes() {
+        elementArray.forEach(node => {
+          node.setAttribute("aria-expanded", true);
+          node.getElementsByTagName('div')[0].removeAttribute('hidden');
+        });
+      }
+
+      function createComboboxes() {
+        var body = document.getElementsByTagName('body')[0];
+        for (i = 0; i < SCRIPT_COUNT; i++) {
+          var containingDiv = document.createElement('div');
+
+          var combobox = document.createElement('div');
+          combobox.setAttribute("role", "combobox");
+          combobox.setAttribute("aria-expanded", "false");
+
+          var input = document.createElement('input');
+          input.setAttribute("type", "text");
+
+          var childDiv = document.createElement('div');
+          childDiv.setAttribute("hidden", "");
+
+          var paragraph = document.createElement('p');
+          paragraph.innerHTML = "Example Text";
+
+          childDiv.appendChild(paragraph);
+          combobox.appendChild(input);
+          combobox.appendChild(childDiv);
+
+          containingDiv.appendChild(combobox);
+          body.appendChild(containingDiv);
+
+          elementArray[i] = combobox;
+        }
+      }
+    </script>
+  </head>
+  <body onload="createComboboxes()">
+    <button onclick="expandComboboxes()">Expand All</button>
+  </body>
+</html>
\ No newline at end of file