Performance improvement for ITextRangeProvider::GetEnclosingElement

This change is an optimizaiton for UIAs GetEnclosingElement.

The cost was in calling |LowestCommonAncestor| because it would compute
multiple parent AXPositions until reaching the common anchor. Creating
a parent Text position is expensive because it calls |MaxTextOffset|.

GetEnclosingElement didn't need an AXPosition so to reduce that cost
a new method |LowestCommonAnchor| has been added which returns the
AXNodeType* that we can use to find the relevant AXPlatformNodeDelegate
to do our work on. |LowestCommonAnchor| may also be used to optimize
other similar APIs which don't necessarily need an AXPosition object.

In order to derive the AXTreeID which is necessary to find the correct
AXPlatformNodeDelegate, AXNode::OwnerTree now exposes its AXTreeID.
This way we can know what the AXTreeID is for an AXNode of an
AXNodePosition anchor. This is already easily accessible from the other
position type BrowserAccessibilityPosition, since BrowserAccessibility
has access to the relevant AXTreeData. Now anchors of  both position
types can know what the relevant AXTreeID is for creating delegates!

I measured the perf difference with std::chrono::high_resolution_clock
on an unoptimized debug build.
With a document that contains 2 columns of 100 divs each, and a single
leaf text child in each column, and a text range that spans between the
two columns.

Without Patch :
439.006ms

With Patch :
0.1371ms

Bug: 928948
Change-Id: Ic9648ff34c7c7030c299c8484fb188a873e3af92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1790066
Commit-Queue: Adam Ettenberger <adettenb@microsoft.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Kurt Catti-Schmidt <kschmi@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#697344}

content/browser/accessibility/browser_accessibility.h

@@ -417,7 +417,7 @@ class CONTENT_EXPORT BrowserAccessibility : public ui::AXPlatformNodeDelegate {
   // Gets the text offsets where new lines start.
   std::vector<int> GetLineStartOffsets() const;
 
-  virtual gfx::NativeViewAccessible GetNativeViewAccessible();
+  gfx::NativeViewAccessible GetNativeViewAccessible() override;
 
   // AXPosition Support
 

ui/accessibility/ax_node.h

@@ -16,6 +16,7 @@
 #include "build/build_config.h"
 #include "ui/accessibility/ax_export.h"
 #include "ui/accessibility/ax_node_data.h"
+#include "ui/accessibility/ax_tree_id.h"
 
 namespace ui {
 
@@ -48,6 +49,8 @@ class AX_EXPORT AXNode final {
       ax::mojom::TextAffinity focus_affinity;
     };
 
+    // See AXTree.
+    virtual AXTreeID GetAXTreeID() const = 0;
     // See AXTree.
     virtual AXTableInfo* GetTableInfo(const AXNode* table_node) const = 0;
     // See AXTree.

ui/accessibility/ax_position.h

@@ -670,17 +670,12 @@ class AXPosition {
     return CreateNextAnchorPosition()->IsNullPosition() && AtEndOfAnchor();
   }
 
-  // This method returns a position instead of a node because this allows us to
-  // return the corresponding text offset or child index in the ancestor that
-  // relates to the current position.
-  // Also, this method uses position instead of tree logic to traverse the tree,
-  // because positions can handle moving across multiple trees, while trees
-  // cannot.
-  AXPositionInstance LowestCommonAncestor(const AXPosition& second) const {
+  // This method finds the lowest common AXNodeType of |this| and |second|.
+  AXNodeType* LowestCommonAnchor(const AXPosition& second) const {
     if (IsNullPosition() || second.IsNullPosition())
-      return CreateNullPosition();
+      return nullptr;
     if (GetAnchor() == second.GetAnchor())
-      return Clone();
+      return GetAnchor();
 
     base::stack<AXNodeType*> our_ancestors = GetAncestorAnchors();
     base::stack<AXNodeType*> other_ancestors = second.GetAncestorAnchors();
@@ -692,6 +687,17 @@ class AXPosition {
       our_ancestors.pop();
       other_ancestors.pop();
     }
+    return common_anchor;
+  }
+
+  // This method returns a position instead of a node because this allows us to
+  // return the corresponding text offset or child index in the ancestor that
+  // relates to the current position.
+  // Also, this method uses position instead of tree logic to traverse the tree,
+  // because positions can handle moving across multiple trees, while trees
+  // cannot.
+  AXPositionInstance LowestCommonAncestor(const AXPosition& second) const {
+    AXNodeType* common_anchor = LowestCommonAnchor(second);
     if (!common_anchor)
       return CreateNullPosition();
 

ui/accessibility/ax_tree.cc

@@ -578,6 +578,10 @@ void AXTree::RemoveObserver(const AXTreeObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+AXTreeID AXTree::GetAXTreeID() const {
+  return data().tree_id;
+}
+
 AXNode* AXTree::GetFromId(int32_t id) const {
   auto iter = id_map_.find(id);
   return iter != id_map_.end() ? iter->second : nullptr;

ui/accessibility/ax_tree.h

@@ -54,6 +54,10 @@ class AX_EXPORT AXTree : public AXNode::OwnerTree {
 
   const AXTreeData& data() const { return data_; }
 
+  // AXNode::OwnerTree override.
+  // Returns the globally unique ID of this accessibility tree.
+  AXTreeID GetAXTreeID() const override;
+
   // AXNode::OwnerTree override.
   // Returns the AXNode with the given |id| if it is part of this AXTree.
   AXNode* GetFromId(int32_t id) const override;

ui/accessibility/platform/ax_fragment_root_win.h

@@ -39,7 +39,7 @@ class AX_EXPORT AXFragmentRootWin : public ui::AXPlatformNodeDelegateBase {
       gfx::AcceleratedWidget widget);
 
   // Returns the NativeViewAccessible for this fragment root.
-  gfx::NativeViewAccessible GetNativeViewAccessible();
+  gfx::NativeViewAccessible GetNativeViewAccessible() override;
 
   // Assistive technologies will typically use UI Automation's control or
   // content view rather than the raw view.

ui/accessibility/platform/ax_platform_node_delegate.h

@@ -77,6 +77,10 @@ class AX_EXPORT AXPlatformNodeDelegate {
   // method is only meaningful on macOS.
   virtual gfx::NativeViewAccessible GetNSWindow() = 0;
 
+  // Get the node for this delegate, which may be an AXPlatformNode or it may
+  // be a native accessible object implemented by another class.
+  virtual gfx::NativeViewAccessible GetNativeViewAccessible() = 0;
+
   // Get the parent of the node, which may be an AXPlatformNode or it may
   // be a native accessible object implemented by another class.
   virtual gfx::NativeViewAccessible GetParent() = 0;

ui/accessibility/platform/ax_platform_node_delegate_base.cc

@@ -44,6 +44,11 @@ gfx::NativeViewAccessible AXPlatformNodeDelegateBase::GetNSWindow() {
   return nullptr;
 }
 
+gfx::NativeViewAccessible
+AXPlatformNodeDelegateBase::GetNativeViewAccessible() {
+  return nullptr;
+}
+
 gfx::NativeViewAccessible AXPlatformNodeDelegateBase::GetParent() {
   return nullptr;
 }

ui/accessibility/platform/ax_platform_node_delegate_base.h

@@ -44,6 +44,10 @@ class AX_EXPORT AXPlatformNodeDelegateBase : public AXPlatformNodeDelegate {
   // See comments in AXPlatformNodeDelegate.
   gfx::NativeViewAccessible GetNSWindow() override;
 
+  // Get the node for this delegate, which may be an AXPlatformNode or it may
+  // be a native accessible object implemented by another class.
+  gfx::NativeViewAccessible GetNativeViewAccessible() override;
+
   // Get the parent of the node, which may be an AXPlatformNode or it may
   // be a native accessible object implemented by another class.
   gfx::NativeViewAccessible GetParent() override;

ui/accessibility/platform/ax_platform_node_textchildprovider_win_unittest.cc

@@ -71,6 +71,8 @@ class AXPlatformNodeTextChildProviderTest : public ui::AXPlatformNodeWinTest {
 
     AXNode* root_node = GetRootNode();
     AXNodePosition::SetTree(tree_.get());
+    AXTreeManagerMap::GetInstance().AddTreeManager(update.tree_data.tree_id,
+                                                   this);
     AXNode* nontext_child_of_root_node = root_node->children()[0];
     AXNode* text_child_of_root_node = root_node->children()[1];
     AXNode* nontext_child_of_nontext_node =

ui/accessibility/platform/ax_platform_node_textrangeprovider_win.cc

@@ -453,17 +453,22 @@ STDMETHODIMP AXPlatformNodeTextRangeProviderWin::GetEnclosingElement(
   WIN_ACCESSIBILITY_API_HISTOGRAM(UMA_API_TEXTRANGE_GETENCLOSINGELEMENT);
   UIA_VALIDATE_TEXTRANGEPROVIDER_CALL();
 
-  AXPositionInstance common_ancestor = start_->LowestCommonAncestor(*end_);
-  AXPlatformNode* node = GetDelegate(common_ancestor.get())
-                             ->GetFromNodeID(common_ancestor->anchor_id());
-  DCHECK(node);
-  while (ui::IsIgnored(node->GetDelegate()->GetData())) {
-    node = static_cast<AXPlatformNodeWin*>(
-        AXPlatformNode::FromNativeViewAccessible(
-            node->GetDelegate()->GetParent()));
-    DCHECK(node);
+  AXNode* common_anchor = start_->LowestCommonAnchor(*end_);
+  DCHECK(common_anchor);
+  if (!common_anchor)
+    return UIA_E_ELEMENTNOTAVAILABLE;
+
+  const AXTreeID tree_id = common_anchor->tree()->GetAXTreeID();
+  const AXNode::AXID node_id = common_anchor->id();
+  AXPlatformNodeDelegate* delegate = GetDelegate(tree_id, node_id);
+  DCHECK(delegate);
+  while (ui::IsIgnored(delegate->GetData())) {
+    AXPlatformNodeWin* parent = static_cast<AXPlatformNodeWin*>(
+        AXPlatformNode::FromNativeViewAccessible(delegate->GetParent()));
+    DCHECK(parent);
+    delegate = parent->GetDelegate();
   }
-  node->GetNativeViewAccessible()->QueryInterface(IID_PPV_ARGS(element));
+  delegate->GetNativeViewAccessible()->QueryInterface(IID_PPV_ARGS(element));
 
   DCHECK(*element);
   return S_OK;
@@ -812,11 +817,15 @@ AXPlatformNodeWin* AXPlatformNodeTextRangeProviderWin::owner() const {
 
 AXPlatformNodeDelegate* AXPlatformNodeTextRangeProviderWin::GetDelegate(
     const AXPositionInstanceType* position) const {
-  AXTreeManager* manager =
-      AXTreeManagerMap::GetInstance().GetManager(position->tree_id());
-  return manager
-             ? manager->GetDelegate(position->tree_id(), position->anchor_id())
-             : owner()->GetDelegate();
+  return GetDelegate(position->tree_id(), position->anchor_id());
+}
+
+AXPlatformNodeDelegate* AXPlatformNodeTextRangeProviderWin::GetDelegate(
+    const AXTreeID tree_id,
+    const AXNode::AXID node_id) const {
+  AXTreeManager* manager = AXTreeManagerMap::GetInstance().GetManager(tree_id);
+  return manager ? manager->GetDelegate(tree_id, node_id)
+                 : owner()->GetDelegate();
 }
 
 AXPlatformNodeTextRangeProviderWin::AXPositionInstance

ui/accessibility/platform/ax_platform_node_textrangeprovider_win.h

@@ -92,6 +92,8 @@ class AX_EXPORT __declspec(uuid("3071e40d-a10d-45ff-a59f-6e8e1138e2c1"))
   AXPlatformNodeWin* owner() const;
   AXPlatformNodeDelegate* GetDelegate(
       const AXPositionInstanceType* position) const;
+  AXPlatformNodeDelegate* GetDelegate(const AXTreeID tree_id,
+                                      const AXNode::AXID node_id) const;
 
   template <typename AnchorIterator, typename ExpandMatchLambda>
   HRESULT FindAttributeRange(const TEXTATTRIBUTEID text_attribute_id,

ui/accessibility/platform/ax_platform_node_textrangeprovider_win_unittest.cc

@@ -948,8 +948,11 @@ TEST_F(AXPlatformNodeTextRangeProviderTest,
 
 TEST_F(AXPlatformNodeTextRangeProviderTest,
        TestITextRangeProviderExpandToEnclosingCharacter) {
-  Init(BuildTextDocument({"some text", "more text"}));
+  ui::AXTreeUpdate update = BuildTextDocument({"some text", "more text"});
+  Init(update);
   AXNodePosition::SetTree(tree_.get());
+  AXTreeManagerMap::GetInstance().AddTreeManager(update.tree_data.tree_id,
+                                                 this);
   AXNode* root_node = GetRootNode();
 
   ComPtr<ITextRangeProvider> text_range_provider;

ui/accessibility/platform/test_ax_node_wrapper.cc

@@ -111,6 +111,10 @@ AXNodePosition::AXPositionInstance TestAXNodeWrapper::CreateTextPositionAt(
       ax::mojom::TextAffinity::kDownstream);
 }
 
+gfx::NativeViewAccessible TestAXNodeWrapper::GetNativeViewAccessible() {
+  return ax_platform_node()->GetNativeViewAccessible();
+}
+
 gfx::NativeViewAccessible TestAXNodeWrapper::GetParent() {
   TestAXNodeWrapper* parent_wrapper =
       GetOrCreate(tree_, node_->GetUnignoredParent());

ui/accessibility/platform/test_ax_node_wrapper.h

@@ -55,6 +55,7 @@ class TestAXNodeWrapper : public AXPlatformNodeDelegateBase {
   const AXTree::Selection GetUnignoredSelection() const override;
   AXNodePosition::AXPositionInstance CreateTextPositionAt(
       int offset) const override;
+  gfx::NativeViewAccessible GetNativeViewAccessible() override;
   gfx::NativeViewAccessible GetParent() override;
   int GetChildCount() override;
   gfx::NativeViewAccessible ChildAtIndex(int index) override;

ui/views/accessibility/ax_virtual_view.cc

@@ -245,6 +245,10 @@ gfx::NativeViewAccessible AXVirtualView::GetNSWindow() {
   return nullptr;
 }
 
+gfx::NativeViewAccessible AXVirtualView::GetNativeViewAccessible() {
+  return GetNativeObject();
+}
+
 gfx::NativeViewAccessible AXVirtualView::GetParent() {
   if (parent_view_)
     return parent_view_->GetNativeObject();

ui/views/accessibility/ax_virtual_view.h

@@ -127,6 +127,7 @@ class VIEWS_EXPORT AXVirtualView : public ui::AXPlatformNodeDelegateBase {
   int GetChildCount() override;
   gfx::NativeViewAccessible ChildAtIndex(int index) override;
   gfx::NativeViewAccessible GetNSWindow() override;
+  gfx::NativeViewAccessible GetNativeViewAccessible() override;
   gfx::NativeViewAccessible GetParent() override;
   gfx::Rect GetBoundsRect(
       const ui::AXCoordinateSystem coordinate_system,

ui/views/accessibility/view_ax_platform_node_delegate.cc

@@ -284,6 +284,11 @@ gfx::NativeViewAccessible ViewAXPlatformNodeDelegate::GetNSWindow() {
   return nullptr;
 }
 
+gfx::NativeViewAccessible
+ViewAXPlatformNodeDelegate::GetNativeViewAccessible() {
+  return GetNativeObject();
+}
+
 gfx::NativeViewAccessible ViewAXPlatformNodeDelegate::GetParent() {
   if (view()->parent())
     return view()->parent()->GetNativeViewAccessible();

ui/views/accessibility/view_ax_platform_node_delegate.h

@@ -50,6 +50,7 @@ class ViewAXPlatformNodeDelegate : public ViewAccessibility,
   int GetChildCount() override;
   gfx::NativeViewAccessible ChildAtIndex(int index) override;
   gfx::NativeViewAccessible GetNSWindow() override;
+  gfx::NativeViewAccessible GetNativeViewAccessible() override;
   gfx::NativeViewAccessible GetParent() override;
   gfx::Rect GetBoundsRect(
       const ui::AXCoordinateSystem coordinate_system,

ui/views/accessibility/view_ax_platform_node_delegate_auralinux.cc

@@ -62,7 +62,7 @@ class AuraLinuxApplication : public ui::AXPlatformNodeDelegateBase,
     window->AddObserver(this);
   }
 
-  gfx::NativeViewAccessible GetNativeViewAccessible() {
+  gfx::NativeViewAccessible GetNativeViewAccessible() override {
     return platform_node_->GetNativeViewAccessible();
   }