Creates AXPosition to uniquely identify a position in the accessibility tree

content/browser/accessibility/ax_platform_position.cc

Index: content/browser/accessibility/ax_platform_position.cc
diff --git a/content/browser/accessibility/ax_platform_position.cc b/content/browser/accessibility/ax_platform_position.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5ed4c8f0113e288bd64108fe1e615bffc34f8499
--- /dev/null
+++ b/content/browser/accessibility/ax_platform_position.cc
@@ -0,0 +1,93 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/accessibility/ax_platform_position.h"
+
+#include "content/browser/accessibility/browser_accessibility_manager.h"
+
+namespace content {
+
+AXPlatformPosition::AXPlatformPosition() {}
+
+AXPlatformPosition::~AXPlatformPosition() {}
+
+void AXPlatformPosition::AnchorChild(int child_index,
+                                     AXTreeID* tree_id,
+                                     int32_t* child_id) const {
+  DCHECK(tree_id);
+  DCHECK(child_id);
+
+  if (!GetAnchor() || child_index < 0 || child_index >= AnchorChildCount()) {
+    *tree_id = AXPosition::INVALID_TREE_ID;
+    *child_id = AXPosition::INVALID_ANCHOR_ID;
+    return;
+  }
+
+  BrowserAccessibility* child = nullptr;
+  if (GetAnchor()->PlatformIsLeaf()) {
+    child = GetAnchor()->InternalGetChild(child_index);
+  } else {
+    child = GetAnchor()->PlatformGetChild(child_index);
+  }
+  DCHECK(child);
+  *tree_id = child->manager()->ax_tree_id();
+  *child_id = child->GetId();
+}
+
+int AXPlatformPosition::AnchorChildCount() const {
+  if (!GetAnchor())
+    return 0;
+
+  if (GetAnchor()->PlatformIsLeaf()) {
+    return static_cast<int>(GetAnchor()->InternalChildCount());
+  } else {
+    return static_cast<int>(GetAnchor()->PlatformChildCount());
+  }
+}
+
+int AXPlatformPosition::AnchorIndexInParent() const {
+  return GetAnchor() ? static_cast<int>(GetAnchor()->GetIndexInParent())
+                     : AXPosition::INVALID_INDEX;
+}
+
+void AXPlatformPosition::AnchorParent(AXTreeID* tree_id,
+                                      int32_t* parent_id) const {
+  DCHECK(tree_id);
+  DCHECK(parent_id);
+
+  if (!GetAnchor() || !GetAnchor()->GetParent()) {
+    *tree_id = AXPosition::INVALID_TREE_ID;
+    *parent_id = AXPosition::INVALID_ANCHOR_ID;
+    return;
+  }
+
+  BrowserAccessibility* parent = GetAnchor()->GetParent();
+  *tree_id = parent->manager()->ax_tree_id();
+  *parent_id = parent->GetId();
+}
+
+BrowserAccessibility* AXPlatformPosition::GetNodeInTree(AXTreeID tree_id,
+                                                        int32_t node_id) const {
+  if (tree_id == AXPosition::INVALID_TREE_ID ||
+      node_id == AXPosition::INVALID_ANCHOR_ID) {
+    return nullptr;
+  }
+
+  auto manager = BrowserAccessibilityManager::FromID(tree_id);
+  if (!manager)
+    return nullptr;
+  return manager->GetFromID(node_id);
+}
+
+int AXPlatformPosition::MaxTextOffset() const {
+  if (IsNullPosition())
+    return AXPosition::INVALID_OFFSET;
+
+  BrowserAccessibility* anchor = GetNodeInTree(tree_id(), anchor_id());
+  if (!anchor)
+    return AXPosition::INVALID_OFFSET;
+  return static_cast<int>(anchor->GetText().length());
+}
+
+}  // namespace content