Added a class acting as a fake caret for accessibility.

content/browser/renderer_host/legacy_render_widget_host_win.cc

 // 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.
 
 #include "content/browser/renderer_host/legacy_render_widget_host_win.h"
 
+#include <atlcom.h>
+
 #include <memory>
 
 #include "base/command_line.h"
 #include "base/win/win_util.h"
 #include "base/win/windows_version.h"
 #include "content/browser/accessibility/browser_accessibility_manager_win.h"
 #include "content/browser/accessibility/browser_accessibility_state_impl.h"
 #include "content/browser/accessibility/browser_accessibility_win.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
 #include "content/public/common/content_switches.h"
+#include "ui/accessibility/platform/ax_fake_caret_win.h"
 #include "ui/base/view_prop.h"
 #include "ui/base/win/internal_constants.h"
 #include "ui/base/win/window_event_target.h"
 #include "ui/display/win/screen_win.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/win/direct_manipulation.h"
 
 namespace content {
 
 // A custom MSAA object id used to determine if a screen reader or some
@@ skipping 135 matching lines @@
 
   if (kIdScreenReaderHoneyPot == obj_id) {
     // When an MSAA client has responded to our fake event on this id,
     // enable basic accessibility support. (Full screen reader support is
     // detected later when specific more advanced APIs are accessed.)
     BrowserAccessibilityStateImpl::GetInstance()->AddAccessibilityModeFlags(
         AccessibilityMode::kNativeAPIs | AccessibilityMode::kWebContents);
     return static_cast<LRESULT>(0L);
   }
 
-  if (static_cast<DWORD>(OBJID_CLIENT) != obj_id || !host_)
-    return static_cast<LRESULT>(0L);
+  if (static_cast<DWORD>(OBJID_CLIENT) == obj_id && host_) {
+    RenderWidgetHostImpl* rwhi =
+        RenderWidgetHostImpl::From(host_->GetRenderWidgetHost());
+    if (!rwhi)
+      return static_cast<LRESULT>(0L);
 
-  RenderWidgetHostImpl* rwhi = RenderWidgetHostImpl::From(
-      host_->GetRenderWidgetHost());
-  if (!rwhi)
-    return static_cast<LRESULT>(0L);
+    BrowserAccessibilityManagerWin* manager =
+        static_cast<BrowserAccessibilityManagerWin*>(
+            rwhi->GetRootBrowserAccessibilityManager());
+    if (!manager)
+      return static_cast<LRESULT>(0L);
 
-  BrowserAccessibilityManagerWin* manager =
-      static_cast<BrowserAccessibilityManagerWin*>(
-          rwhi->GetRootBrowserAccessibilityManager());
-  if (!manager)
-    return static_cast<LRESULT>(0L);
+    base::win::ScopedComPtr<IAccessible> root(
+        ToBrowserAccessibilityWin(manager->GetRoot()));
+    return LresultFromObject(IID_IAccessible, w_param,
+                             static_cast<IAccessible*>(root.Detach()));
+  } else if (static_cast<DWORD>(OBJID_CARET) == obj_id) {

[dougt, 2017/03/28 15:23:44]

nit:

the above if-stmt returns making the following else stmt a non-sequitur.  It
might be clearer to not use the 'else'.

+    // Used by some assistive software to retrieve the location of the caret.
+    CComObjectStack<ui::AXFakeCaretWin> fake_caret;
+    DCHECK_EQ(fake_caret.m_hResFinalConstruct, S_OK);

[dougt, 2017/03/28 15:23:44]

I am confused by this DCHECK. Are you concerned with the result of the
construction of the stack of AXFakeCaretWin's?  Or are you just not sure if you
should check it or not at this point?

+    return LresultFromObject(IID_IAccessible, w_param,
+                             static_cast<IAccessible*>(&fake_caret));
+  }
 
-  base::win::ScopedComPtr<IAccessible> root(
-      ToBrowserAccessibilityWin(manager->GetRoot()));
-  return LresultFromObject(IID_IAccessible, w_param,
-      static_cast<IAccessible*>(root.Detach()));
+  return static_cast<LRESULT>(0L);
 }
 
 // We send keyboard/mouse/touch messages to the parent window via SendMessage.
 // While this works, this has the side effect of converting input messages into
 // sent messages which changes their priority and could technically result
 // in these messages starving other messages in the queue. Additionally
 // keyboard/mouse hooks would not see these messages. The alternative approach
 // is to set and release capture as needed on the parent to ensure that it
 // receives all mouse events. However that was shelved due to possible issues
 // with capture changes.
@@ skipping 207 matching lines @@
       direct_manipulation_helper_->Activate(hwnd());
     } else if (window_pos->flags & SWP_HIDEWINDOW) {
       direct_manipulation_helper_->Deactivate(hwnd());
     }
   }
   SetMsgHandled(FALSE);
   return 0;
 }
 
 }  // namespace content