ui/accessibility/platform/ax_fragment_root_win.h

// Copyright 2019 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.

#ifndef UI_ACCESSIBILITY_PLATFORM_AX_FRAGMENT_ROOT_WIN_H_
#define UI_ACCESSIBILITY_PLATFORM_AX_FRAGMENT_ROOT_WIN_H_

#include "ui/accessibility/platform/ax_platform_node_delegate_base.h"

#include <wrl/client.h>

namespace ui {

class AXPlatformNodeWin;
class AXFragmentRootPlatformNodeWin;

// UI Automation on Windows requires the root of a multi-element provider to
// implement IRawElementProviderFragmentRoot. Our internal accessibility trees
// may not know their roots for right away; for example, web content may
// deserialize the document for an iframe before the host document. Because of
// this, and because COM rules require that the list of interfaces returned by
// QueryInterface remain static over the lifetime of an object instance, we
// implement IRawElementProviderFragmentRoot on its own node, with the root of
// our internal accessibility tree as its sole child.
//
// Since UIA derives some information from the underlying HWND hierarchy, we
// expose one fragment root per HWND. The class that owns the HWND is expected
// to own the corresponding AXFragmentRootWin.
class AX_EXPORT AXFragmentRootWin : public ui::AXPlatformNodeDelegateBase {
 public:
  AXFragmentRootWin(gfx::AcceleratedWidget widget,
                    gfx::NativeViewAccessible child);
  ~AXFragmentRootWin() override;

  // Fragment roots register themselves in a map upon creation and unregister
  // upon destruction. This method provides a lookup, which allows the internal
  // accessibility root to navigate back to the corresponding fragment root.
  static AXFragmentRootWin* GetForAcceleratedWidget(
      gfx::AcceleratedWidget widget);

  // Return the NativeViewAccessible for this fragment root.
  gfx::NativeViewAccessible GetNativeViewAccessible();

  // The sole child of a fragment root is permitted to change during the
  // fragment root's lifetime. This will happen, for example, on a web content
  // navigation.
  void SetChild(gfx::NativeViewAccessible child);

 private:
  // AXPlatformNodeDelegate overrides.
  int GetChildCount() override;
  gfx::NativeViewAccessible ChildAtIndex(int index) override;
  gfx::NativeViewAccessible HitTestSync(int x, int y) override;
  gfx::NativeViewAccessible GetFocus() override;
  const ui::AXUniqueId& GetUniqueId() const override;
  gfx::AcceleratedWidget GetTargetForNativeAccessibilityEvent() override;

  Microsoft::WRL::ComPtr<ui::AXFragmentRootPlatformNodeWin> platform_node_;
  Microsoft::WRL::ComPtr<ui::AXPlatformNodeWin> child_;
  ui::AXUniqueId unique_id_;
  gfx::AcceleratedWidget widget_;
};

}  // namespace ui

#endif  // UI_ACCESSIBILITY_PLATFORM_AX_FRAGMENT_ROOT_WIN_H_