AccessibilityNodeInfo caching for Android performance improvement

This CL expands on our work of improving the performance of
accessibility features on Android.

Here we create a SparseArray<AccessibilityNodeInfo> to store
a mapping of view ids to their corresponding
AccessibilityNodeInfo objects. When the system asks us to create
a new object for that view, we leverage the object stored
in our array (cache) rather than constructing one from scratch.

There are helper methods so the native code can drive clearing
the cache at appropriate times. We are clearing the cache on a
given node during OnDataChanged or during OnNodeWillBeDeleted.

Change-Id: Iaf817886b8d7038d268d4b459d135c46f60cbfff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2080857
Commit-Queue: Mark Schillaci <mschillaci@google.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747861}

content/browser/accessibility/browser_accessibility_android.cc

@@ -1846,6 +1846,10 @@ void BrowserAccessibilityAndroid::OnDataChanged() {
       new_value_ = value;
     }
   }
+
+  auto* manager =
+      static_cast<BrowserAccessibilityManagerAndroid*>(this->manager());
+  manager->ClearNodeInfoCacheForGivenId(unique_id());
 }
 
 int BrowserAccessibilityAndroid::CountChildrenWithRole(

content/browser/accessibility/browser_accessibility_manager_android.cc

@@ -365,6 +365,15 @@ bool BrowserAccessibilityManagerAndroid::PreviousAtGranularity(
   return true;
 }
 
+void BrowserAccessibilityManagerAndroid::ClearNodeInfoCacheForGivenId(
+    int32_t unique_id) {
+  WebContentsAccessibilityAndroid* wcax = GetWebContentsAXFromRootManager();
+  if (!wcax)
+    return;
+
+  wcax->ClearNodeInfoCacheForGivenId(unique_id);
+}
+
 bool BrowserAccessibilityManagerAndroid::OnHoverEvent(
     const ui::MotionEventAndroid& event) {
   WebContentsAccessibilityAndroid* wcax = GetWebContentsAXFromRootManager();
@@ -414,6 +423,17 @@ gfx::Rect BrowserAccessibilityManagerAndroid::GetViewBounds() {
   return gfx::Rect();
 }
 
+void BrowserAccessibilityManagerAndroid::OnNodeWillBeDeleted(ui::AXTree* tree,
+                                                             ui::AXNode* node) {
+  BrowserAccessibility* wrapper = GetFromAXNode(node);
+  BrowserAccessibilityAndroid* android_node =
+      static_cast<BrowserAccessibilityAndroid*>(wrapper);
+
+  ClearNodeInfoCacheForGivenId(android_node->unique_id());
+
+  BrowserAccessibilityManager::OnNodeWillBeDeleted(tree, node);
+}
+
 void BrowserAccessibilityManagerAndroid::OnAtomicUpdateFinished(
     ui::AXTree* tree,
     bool root_changed,

content/browser/accessibility/browser_accessibility_manager_android.h

@@ -103,6 +103,9 @@ class CONTENT_EXPORT BrowserAccessibilityManagerAndroid
                              int32_t* start_index,
                              int32_t* end_index);
 
+  // Helper method to clear AccessibilityNodeInfo cache on given node
+  void ClearNodeInfoCacheForGivenId(int32_t unique_id);
+
  private:
   // AXTreeObserver overrides.
   void OnAtomicUpdateFinished(
@@ -110,6 +113,8 @@ class CONTENT_EXPORT BrowserAccessibilityManagerAndroid
       bool root_changed,
       const std::vector<ui::AXTreeObserver::Change>& changes) override;
 
+  void OnNodeWillBeDeleted(ui::AXTree* tree, ui::AXNode* node) override;
+
   bool UseRootScrollOffsetsWhenComputingBounds() override;
 
   WebContentsAccessibilityAndroid* GetWebContentsAXFromRootManager();

content/browser/accessibility/web_contents_accessibility_android.cc

@@ -579,6 +579,17 @@ void WebContentsAccessibilityAndroid::HandleNavigate() {
   Java_WebContentsAccessibilityImpl_handleNavigate(env, obj);
 }
 
+void WebContentsAccessibilityAndroid::ClearNodeInfoCacheForGivenId(
+    int32_t unique_id) {
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jobject> obj = java_ref_.get(env);
+  if (obj.is_null())
+    return;
+
+  Java_WebContentsAccessibilityImpl_clearNodeInfoCacheForGivenId(env, obj,
+                                                                 unique_id);
+}
+
 base::android::ScopedJavaLocalRef<jstring>
 WebContentsAccessibilityAndroid::GetSupportedHtmlElementTypes(
     JNIEnv* env,
@@ -670,6 +681,46 @@ static size_t ActualUnignoredChildCount(const ui::AXNode* node) {
   return count;
 }
 
+void WebContentsAccessibilityAndroid::UpdateAccessibilityNodeInfoBoundsRect(
+    JNIEnv* env,
+    const JavaParamRef<jobject>& obj,
+    const JavaParamRef<jobject>& info,
+    jint unique_id,
+    BrowserAccessibilityAndroid* node) {
+  float dip_scale = use_zoom_for_dsf_enabled_
+                        ? 1 / root_manager_->device_scale_factor()
+                        : 1.0;
+  gfx::Rect absolute_rect = gfx::ScaleToEnclosingRect(
+      node->GetUnclippedRootFrameBoundsRect(), dip_scale, dip_scale);
+  gfx::Rect parent_relative_rect = absolute_rect;
+  if (node->PlatformGetParent()) {
+    gfx::Rect parent_rect = gfx::ScaleToEnclosingRect(
+        node->PlatformGetParent()->GetUnclippedRootFrameBoundsRect(), dip_scale,
+        dip_scale);
+    parent_relative_rect.Offset(-parent_rect.OffsetFromOrigin());
+  }
+  bool is_root = node->PlatformGetParent() == NULL;
+  Java_WebContentsAccessibilityImpl_setAccessibilityNodeInfoLocation(
+      env, obj, info, unique_id, absolute_rect.x(), absolute_rect.y(),
+      parent_relative_rect.x(), parent_relative_rect.y(), absolute_rect.width(),
+      absolute_rect.height(), is_root);
+}
+
+jboolean WebContentsAccessibilityAndroid::UpdateCachedAccessibilityNodeInfo(
+    JNIEnv* env,
+    const JavaParamRef<jobject>& obj,
+    const JavaParamRef<jobject>& info,
+    jint unique_id) {
+  BrowserAccessibilityAndroid* node = GetAXFromUniqueID(unique_id);
+  if (!node)
+    return false;
+
+  // Update cached nodes by providing new enclosing Rects
+  UpdateAccessibilityNodeInfoBoundsRect(env, obj, info, unique_id, node);
+
+  return true;
+}
+
 jboolean WebContentsAccessibilityAndroid::PopulateAccessibilityNodeInfo(
     JNIEnv* env,
     const JavaParamRef<jobject>& obj,
@@ -744,23 +795,9 @@ jboolean WebContentsAccessibilityAndroid::PopulateAccessibilityNodeInfo(
         base::android::ConvertUTF16ToJavaString(env, element_id));
   }
 
-  float dip_scale = use_zoom_for_dsf_enabled_
-                        ? 1 / root_manager_->device_scale_factor()
-                        : 1.0;
-  gfx::Rect absolute_rect = gfx::ScaleToEnclosingRect(
-      node->GetUnclippedRootFrameBoundsRect(), dip_scale, dip_scale);
-  gfx::Rect parent_relative_rect = absolute_rect;
-  if (node->PlatformGetParent()) {
-    gfx::Rect parent_rect = gfx::ScaleToEnclosingRect(
-        node->PlatformGetParent()->GetUnclippedRootFrameBoundsRect(), dip_scale,
-        dip_scale);
-    parent_relative_rect.Offset(-parent_rect.OffsetFromOrigin());
-  }
+  UpdateAccessibilityNodeInfoBoundsRect(env, obj, info, unique_id, node);
+
   bool is_root = node->PlatformGetParent() == NULL;
-  Java_WebContentsAccessibilityImpl_setAccessibilityNodeInfoLocation(
-      env, obj, info, unique_id, absolute_rect.x(), absolute_rect.y(),
-      parent_relative_rect.x(), parent_relative_rect.y(), absolute_rect.width(),
-      absolute_rect.height(), is_root);
 
   Java_WebContentsAccessibilityImpl_setAccessibilityNodeInfoKitKatAttributes(
       env, obj, info, is_root, node->IsEditableText(),

content/browser/accessibility/web_contents_accessibility_android.h

@@ -82,6 +82,11 @@ class CONTENT_EXPORT WebContentsAccessibilityAndroid
       jint id);
 
   // Populate Java accessibility data structures with info about a node.
+  jboolean UpdateCachedAccessibilityNodeInfo(
+      JNIEnv* env,
+      const base::android::JavaParamRef<jobject>& obj,
+      const base::android::JavaParamRef<jobject>& info,
+      jint id);
   jboolean PopulateAccessibilityNodeInfo(
       JNIEnv* env,
       const base::android::JavaParamRef<jobject>& obj,
@@ -264,6 +269,7 @@ class CONTENT_EXPORT WebContentsAccessibilityAndroid
   bool OnHoverEvent(const ui::MotionEventAndroid& event);
   void HandleHover(int32_t unique_id);
   void HandleNavigate();
+  void ClearNodeInfoCacheForGivenId(int32_t unique_id);
 
   base::WeakPtr<WebContentsAccessibilityAndroid> GetWeakPtr();
 
@@ -271,6 +277,12 @@ class CONTENT_EXPORT WebContentsAccessibilityAndroid
   BrowserAccessibilityAndroid* GetAXFromUniqueID(int32_t unique_id);
 
   void CollectStats();
+  void UpdateAccessibilityNodeInfoBoundsRect(
+      JNIEnv* env,
+      const base::android::JavaParamRef<jobject>& obj,
+      const base::android::JavaParamRef<jobject>& info,
+      jint id,
+      BrowserAccessibilityAndroid* node);
 
   // A weak reference to the Java WebContentsAccessibilityAndroid object.
   JavaObjectWeakGlobalRef java_ref_;

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

@@ -178,6 +178,10 @@ public class WebContentsAccessibilityImpl extends AccessibilityNodeProvider
     // to a single Runnable that will send an event after some delay.
     private SparseArray<Runnable> mPendingEvents = new SparseArray<>();
 
+    // This array maps a given virtualViewId to an |AccessibilityNodeInfo| for that view. We use
+    // this to update a node quickly rather than building from one scratch each time.
+    private SparseArray<AccessibilityNodeInfo> mNodeInfoCache = new SparseArray<>();
+
     /**
      * Create a WebContentsAccessibilityImpl object.
      */
@@ -313,6 +317,15 @@ public class WebContentsAccessibilityImpl extends AccessibilityNodeProvider
         return this;
     }
 
+    @CalledByNative
+    public void clearNodeInfoCacheForGivenId(int virtualViewId) {
+        // Recycle and remove the element in our cache for this |virtualViewId|.
+        if (mNodeInfoCache.get(virtualViewId) != null) {
+            mNodeInfoCache.get(virtualViewId).recycle();
+            mNodeInfoCache.remove(virtualViewId);
+        }
+    }
+
     @Override
     public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualViewId) {
         if (!isAccessibilityEnabled()) {
@@ -329,20 +342,43 @@ public class WebContentsAccessibilityImpl extends AccessibilityNodeProvider
             return null;
         }
 
-        final AccessibilityNodeInfo info = AccessibilityNodeInfo.obtain(mView);
-        info.setPackageName(mContext.getPackageName());
-        info.setSource(mView, virtualViewId);
+        // We need to create an |AccessibilityNodeInfo| object for this |virtualViewId|. If we have
+        // one in our cache, then communicate this so web_contents_accessibility_android.cc
+        // will update a fraction of the object and for the rest leverage what is already there.
+        if (mNodeInfoCache.get(virtualViewId) != null) {
+            AccessibilityNodeInfo cachedNode =
+                    AccessibilityNodeInfo.obtain(mNodeInfoCache.get(virtualViewId));
 
-        if (virtualViewId == rootId) {
-            info.setParent(mView);
-        }
+            if (WebContentsAccessibilityImplJni.get().updateCachedAccessibilityNodeInfo(
+                        mNativeObj, WebContentsAccessibilityImpl.this, cachedNode, virtualViewId)) {
+                // After successfully re-populating this cached node, return result.
+                return cachedNode;
+            } else {
+                // If the node is no longer valid, wipe it from the cache and return null
+                mNodeInfoCache.get(virtualViewId).recycle();
+                mNodeInfoCache.remove(virtualViewId);
+                return null;
+            }
 
-        if (WebContentsAccessibilityImplJni.get().populateAccessibilityNodeInfo(
-                    mNativeObj, WebContentsAccessibilityImpl.this, info, virtualViewId)) {
-            return info;
         } else {
-            info.recycle();
-            return null;
+            // If we have no copy of this node in our cache, build a new one from scratch.
+            final AccessibilityNodeInfo info = AccessibilityNodeInfo.obtain(mView);
+            info.setPackageName(mContext.getPackageName());
+            info.setSource(mView, virtualViewId);
+
+            if (virtualViewId == rootId) {
+                info.setParent(mView);
+            }
+
+            if (WebContentsAccessibilityImplJni.get().populateAccessibilityNodeInfo(
+                        mNativeObj, WebContentsAccessibilityImpl.this, info, virtualViewId)) {
+                // After successfully populating this node, add it to our cache then return.
+                mNodeInfoCache.put(virtualViewId, AccessibilityNodeInfo.obtain(info));
+                return info;
+            } else {
+                info.recycle();
+                return null;
+            }
         }
     }
 
@@ -1765,6 +1801,8 @@ public class WebContentsAccessibilityImpl extends AccessibilityNodeProvider
                 WebContentsAccessibilityImpl caller, int id);
         int getEditableTextSelectionEnd(long nativeWebContentsAccessibilityAndroid,
                 WebContentsAccessibilityImpl caller, int id);
+        boolean updateCachedAccessibilityNodeInfo(long nativeWebContentsAccessibilityAndroid,
+                WebContentsAccessibilityImpl caller, AccessibilityNodeInfo info, int id);
         boolean populateAccessibilityNodeInfo(long nativeWebContentsAccessibilityAndroid,
                 WebContentsAccessibilityImpl caller, AccessibilityNodeInfo info, int id);
         boolean populateAccessibilityEvent(long nativeWebContentsAccessibilityAndroid,

content/public/android/javatests/src/org/chromium/content/browser/accessibility/WebContentsAccessibilityTest.java

@@ -761,6 +761,9 @@ public class WebContentsAccessibilityTest {
         final WebContentsAccessibilityImpl wcax = mActivityTestRule.getWebContentsAccessibility();
         wcax.addSpellingErrorForTesting(textNodeVirtualViewId, 4, 9);
 
+        // Clear our cache for this node.
+        wcax.clearNodeInfoCacheForGivenId(textNodeVirtualViewId);
+
         // Now get that AccessibilityNodeInfo and retrieve its text.
         AccessibilityNodeInfo textNode =
                 provider.createAccessibilityNodeInfo(textNodeVirtualViewId);