Creates AXPosition to uniquely identify a position in the accessibility tree

ui/accessibility/ax_node_position.cc

Index: ui/accessibility/ax_node_position.cc
diff --git a/ui/accessibility/ax_node_position.cc b/ui/accessibility/ax_node_position.cc
new file mode 100644
index 0000000000000000000000000000000000000000..368a253da1528e65d4c60b42fef73b9ebd6df77a
--- /dev/null
+++ b/ui/accessibility/ax_node_position.cc
@@ -0,0 +1,90 @@
+// 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 "ui/accessibility/ax_node_position.h"
+
+#include "base/strings/string16.h"
+#include "ui/accessibility/ax_enums.h"
+
+namespace ui {
+
+AXTree* AXNodePosition::tree_ = nullptr;
+
+AXNodePosition::AXNodePosition() {}
+
+AXNodePosition::~AXNodePosition() {}
+
+int AXNodePosition::AnchorChildCount() const {
+  return GetAnchor() ? GetAnchor()->child_count() : -1;
+}
+
+AXNodePosition* AXNodePosition::GetChildPositionAt(int child_index) const {
+  if (IsNullPosition())
+    return static_cast<AXNodePosition*>(CreateNullPosition());
+
+  if (child_index < 0 || child_index >= AnchorChildCount())
+    return static_cast<AXNodePosition*>(CreateNullPosition());
+
+  AXNode* child_anchor = GetAnchor()->ChildAtIndex(child_index);
+  DCHECK(child_anchor);
+  switch (get_kind()) {
+    case AXPositionKind::NullPosition:
+      NOTREACHED();
+      return static_cast<AXNodePosition*>(CreateNullPosition());
+    case AXPositionKind::TreePosition:
+      return static_cast<AXNodePosition*>(CreateTreePosition(
+          get_tree_id(), child_anchor->id(), 0 /* child_index */));
+    case AXPositionKind::TextPosition:
+      return static_cast<AXNodePosition*>(CreateTextPosition(
+          get_tree_id(), child_anchor->id(), 0 /* text_offset */));
+  }
+
+  return static_cast<AXNodePosition*>(CreateNullPosition());
+}
+
+AXNodePosition* AXNodePosition::GetParentPosition() const {
+  if (IsNullPosition())
+    return static_cast<AXNodePosition*>(CreateNullPosition());
+
+  AXNode* parent_anchor = GetAnchor()->parent();
+  if (!parent_anchor)
+    return static_cast<AXNodePosition*>(CreateNullPosition());
+
+  switch (get_kind()) {
+    case AXPositionKind::NullPosition:
+      NOTREACHED();
+      return static_cast<AXNodePosition*>(CreateNullPosition());
+    case AXPositionKind::TreePosition:
+      return static_cast<AXNodePosition*>(CreateTreePosition(
+          get_tree_id(), parent_anchor->id(), 0 /* child_index */));
+    case AXPositionKind::TextPosition:
+      return static_cast<AXNodePosition*>(CreateTextPosition(
+          get_tree_id(), parent_anchor->id(), 0 /* text_offset */));
+  }
+
+  return static_cast<AXNodePosition*>(CreateNullPosition());
+}
+
+int AXNodePosition::AnchorIndexInParent() const {
+  return GetAnchor() ? GetAnchor()->index_in_parent() : -1;
+}
+
+AXNode* AXNodePosition::GetNodeInTree(int tree_id, int32_t node_id) const {
+  if (IsNullPosition() || !tree_)
+    return nullptr;
+  return AXNodePosition::tree_->GetFromId(node_id);
+}
+
+int AXNodePosition::MaxTextOffset() const {
+  if (IsTextPosition()) {
+    DCHECK(GetAnchor());
+    base::string16 name =
+        GetAnchor()->data().GetString16Attribute(AX_ATTR_NAME);
+    return static_cast<int>(name.length());
+  }
+
+  return 0;
+}
+
+}  // namespace ui