Create a visible window with class name Chrome_RenderWidgetHostHWND which corresponds to the bounds…

content/browser/renderer_host/legacy_render_widget_host_win.h

+// Copyright (c) 2014 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 CONTENT_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_H_
+#define CONTENT_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_H_
+
+#include <atlbase.h>
+#include <atlapp.h>
+#include <atlcom.h>
+#include <atlcrack.h>
+#include <oleacc.h>
+
+#include "base/basictypes.h"
+#include "base/win/scoped_comptr.h"
+#include "content/common/content_export.h"
+
+namespace content {
+class BrowserAccessibilityManagerWin;
+
+// Some screen readers expect every tab / every unique web content container
+// to be in its own HWND with class name Chrome_RenderWidgetHostHWND.
+// With Aura there is one main HWND which comprises the whole browser window or
+// the whole desktop. So, we need a fake HWND with the window class as
+// Chrome_RenderWidgetHostHWND as the root of the accessibility tree for each
+// tab. Additionally there are legacy drivers for trackpads/trackpoints which
+// also have special code for sending mouse wheel and scroll events to the
+// Chrome_RenderWidgetHostHWND window.
+// We should get rid of this code when the latest two versions of all
+// supported screen readers and legacy drivers no longer make this assumption.
+
+// This class implements a child HWND with the same size as the content area,
+// that delegates its accessibility implementation to the root of the
+// BrowserAccessibilityManager tree. This HWND is hooked up as the parent of
+// the root object in the BrowserAccessibilityManager tree, so when any
+// accessibility client calls ::WindowFromAccessibleObject, they get this
+// HWND instead of the DesktopWindowTreeHostWin.
+class CONTENT_EXPORT LegacyRenderWidgetHostHWND
+    : public ATL::CWindowImpl<LegacyRenderWidgetHostHWND,
+                              NON_EXPORTED_BASE(ATL::CWindow),
+                              ATL::CWinTraits<WS_CHILD> > {
+ public:
+  // Unfortunately, some screen readers trackpoint drivers look for this exact
+  //window class to enable certain features. It'd be great to remove this.
+  DECLARE_WND_CLASS_EX(L"Chrome_RenderWidgetHostHWND", CS_DBLCLKS, 0);
+
+  explicit LegacyRenderWidgetHostHWND(HWND parent);
+  ~LegacyRenderWidgetHostHWND();
+
+  BEGIN_MSG_MAP_EX(LegacyRenderWidgetHostHWND)
+    MESSAGE_HANDLER_EX(WM_GETOBJECT, OnGetObject)
+    MESSAGE_RANGE_HANDLER(WM_KEYFIRST, WM_KEYLAST, OnKeyboardRange)
+    MESSAGE_HANDLER_EX(WM_PAINT, OnPaint)
+    MESSAGE_HANDLER_EX(WM_NCPAINT, OnNCPaint)
+    MESSAGE_HANDLER_EX(WM_ERASEBKGND, OnEraseBkGnd)
+    MESSAGE_RANGE_HANDLER(WM_MOUSEFIRST, WM_MOUSELAST, OnMouseRange)
+    MESSAGE_HANDLER_EX(WM_SETCURSOR, OnSetCursor)
+    MESSAGE_HANDLER_EX(WM_TOUCH, OnTouch)
+  END_MSG_MAP()
+
+  HWND hwnd() { return m_hWnd; }
+
+  HWND parent() { return parent_; }
+
+  IAccessible* window_accessible() { return window_accessible_; }
+
+  void set_browser_accessibility_manager(
+      content::BrowserAccessibilityManagerWin* manager) {
+    manager_ = manager;
+  }
+
+  void OnManagerDeleted();
+
+  void Show();
+  void Hide();
+
+ protected:
+  virtual void OnFinalMessage(HWND hwnd) OVERRIDE;
+
+ private:
+  // To ensure that the Legacy HWND is as non intrusive as possible, we set
+  // capture to the parent window when we receive a mouse move. After that
+  // all mouse messages go to the parent. We need to release capture on the
+  // parent window when the mouse leaves the bounds of the legacy HWND. Tp
+  // achieve this and not touch any existing code, we subclass the parent HWND
+  // and handle mouse moves. When we find that the mouse has left the legacy
+  // HWND or if another HWND lies beneath the mouse, we release capture.
+  class MouseWindowBoundsTracker
+    : public ATL::CWindowImpl<MouseWindowBoundsTracker> {
+   public:
+    MouseWindowBoundsTracker();
+    ~MouseWindowBoundsTracker();
+
+    BEGIN_MSG_MAP_EX(MouseWindowBoundsTracker)
+      MESSAGE_HANDLER_EX(WM_MOUSEMOVE, OnMouseMove)
+    END_MSG_MAP()
+
+    void set_tracking_window(HWND tracking_window) {
+      tracking_window_ = tracking_window;
+    }
+
+   private:
+    LRESULT OnMouseMove(UINT message, WPARAM w_param, LPARAM l_param);
+
+    // The handle to the legacy child window whose bounds are used to track
+    // whether capture is to be released.
+    HWND tracking_window_;
+
+    DISALLOW_COPY_AND_ASSIGN(MouseWindowBoundsTracker);
+  };
+
+  LRESULT OnEraseBkGnd(UINT message, WPARAM w_param, LPARAM l_param);
+  LRESULT OnGetObject(UINT message, WPARAM w_param, LPARAM l_param);
+  LRESULT OnKeyboardRange(UINT message, WPARAM w_param, LPARAM l_param,
+                          BOOL& handled);
+  LRESULT OnMouseRange(UINT message, WPARAM w_param, LPARAM l_param,
+                       BOOL& handled);
+  LRESULT OnNCPaint(UINT message, WPARAM w_param, LPARAM l_param);
+  LRESULT OnPaint(UINT message, WPARAM w_param, LPARAM l_param);
+  LRESULT OnSetCursor(UINT message, WPARAM w_param, LPARAM l_param);
+  LRESULT OnTouch(UINT message, WPARAM w_param, LPARAM l_param);
+
+  content::BrowserAccessibilityManagerWin* manager_;
+  base::win::ScopedComPtr<IAccessible> window_accessible_;
+  HWND parent_;
+  MouseWindowBoundsTracker mouse_window_bounds_tracker_;
+
+  DISALLOW_COPY_AND_ASSIGN(LegacyRenderWidgetHostHWND);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_H_
+