Implement accessibility enhancements (issue #1217)

- Add new CefBrowserHost::SetAccessibilityState method for toggling
  accessibility state when readers are detected by the client.
- Add new CefAccessibilityHandler interface for the delivery of
  accessibility notifications to windowless (OSR) clients.
- Fix delivery of CefFocusHandler callbacks to windowless clients.
- cefclient: Add example windowless accessibility implementation on Windows and macOS.
- cefclient: Automatically detect screen readers on Windows and macOS.

libcef_dll/cpptoc/accessibility_handler_cpptoc.cc

@@ -0,0 +1,81 @@
+// Copyright (c) 2017 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+//
+// ---------------------------------------------------------------------------
+//
+// This file was generated by the CEF translator tool. If making changes by
+// hand only do so within the body of existing method and function
+// implementations. See the translator.README.txt file in the tools directory
+// for more information.
+//
+
+#include "libcef_dll/cpptoc/accessibility_handler_cpptoc.h"
+#include "libcef_dll/ctocpp/value_ctocpp.h"
+
+
+namespace {
+
+// MEMBER FUNCTIONS - Body may be edited by hand.
+
+void CEF_CALLBACK accessibility_handler_on_accessibility_tree_change(
+    struct _cef_accessibility_handler_t* self, struct _cef_value_t* value) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return;
+  // Verify param: value; type: refptr_diff
+  DCHECK(value);
+  if (!value)
+    return;
+
+  // Execute
+  CefAccessibilityHandlerCppToC::Get(self)->OnAccessibilityTreeChange(
+      CefValueCToCpp::Wrap(value));
+}
+
+void CEF_CALLBACK accessibility_handler_on_accessibility_location_change(
+    struct _cef_accessibility_handler_t* self, struct _cef_value_t* value) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return;
+  // Verify param: value; type: refptr_diff
+  DCHECK(value);
+  if (!value)
+    return;
+
+  // Execute
+  CefAccessibilityHandlerCppToC::Get(self)->OnAccessibilityLocationChange(
+      CefValueCToCpp::Wrap(value));
+}
+
+}  // namespace
+
+
+// CONSTRUCTOR - Do not edit by hand.
+
+CefAccessibilityHandlerCppToC::CefAccessibilityHandlerCppToC() {
+  GetStruct()->on_accessibility_tree_change =
+      accessibility_handler_on_accessibility_tree_change;
+  GetStruct()->on_accessibility_location_change =
+      accessibility_handler_on_accessibility_location_change;
+}
+
+template<> CefRefPtr<CefAccessibilityHandler> CefCppToCRefCounted<CefAccessibilityHandlerCppToC,
+    CefAccessibilityHandler, cef_accessibility_handler_t>::UnwrapDerived(
+    CefWrapperType type, cef_accessibility_handler_t* s) {
+  NOTREACHED() << "Unexpected class type: " << type;
+  return NULL;
+}
+
+#if DCHECK_IS_ON()
+template<> base::AtomicRefCount CefCppToCRefCounted<CefAccessibilityHandlerCppToC,
+    CefAccessibilityHandler, cef_accessibility_handler_t>::DebugObjCt = 0;
+#endif
+
+template<> CefWrapperType CefCppToCRefCounted<CefAccessibilityHandlerCppToC,
+    CefAccessibilityHandler, cef_accessibility_handler_t>::kWrapperType =
+    WT_ACCESSIBILITY_HANDLER;

libcef_dll/cpptoc/accessibility_handler_cpptoc.h

@@ -0,0 +1,34 @@
+// Copyright (c) 2017 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+//
+// ---------------------------------------------------------------------------
+//
+// This file was generated by the CEF translator tool. If making changes by
+// hand only do so within the body of existing method and function
+// implementations. See the translator.README.txt file in the tools directory
+// for more information.
+//
+
+#ifndef CEF_LIBCEF_DLL_CPPTOC_ACCESSIBILITY_HANDLER_CPPTOC_H_
+#define CEF_LIBCEF_DLL_CPPTOC_ACCESSIBILITY_HANDLER_CPPTOC_H_
+#pragma once
+
+#if !defined(WRAPPING_CEF_SHARED)
+#error This file can be included wrapper-side only
+#endif
+
+#include "include/cef_accessibility_handler.h"
+#include "include/capi/cef_accessibility_handler_capi.h"
+#include "libcef_dll/cpptoc/cpptoc_ref_counted.h"
+
+// Wrap a C++ class with a C structure.
+// This class may be instantiated and accessed wrapper-side only.
+class CefAccessibilityHandlerCppToC
+    : public CefCppToCRefCounted<CefAccessibilityHandlerCppToC,
+        CefAccessibilityHandler, cef_accessibility_handler_t> {
+ public:
+  CefAccessibilityHandlerCppToC();
+};
+
+#endif  // CEF_LIBCEF_DLL_CPPTOC_ACCESSIBILITY_HANDLER_CPPTOC_H_

libcef_dll/cpptoc/browser_host_cpptoc.cc

@@ -1005,6 +1005,19 @@ struct _cef_navigation_entry_t* CEF_CALLBACK browser_host_get_visible_navigation
   return CefNavigationEntryCppToC::Wrap(_retval);
 }
 
+void CEF_CALLBACK browser_host_set_accessibility_state(
+    struct _cef_browser_host_t* self, cef_state_t accessibility_state) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return;
+
+  // Execute
+  CefBrowserHostCppToC::Get(self)->SetAccessibilityState(
+      accessibility_state);
+}
+
 }  // namespace
 
 
@@ -1072,6 +1085,7 @@ CefBrowserHostCppToC::CefBrowserHostCppToC() {
       browser_host_drag_source_system_drag_ended;
   GetStruct()->get_visible_navigation_entry =
       browser_host_get_visible_navigation_entry;
+  GetStruct()->set_accessibility_state = browser_host_set_accessibility_state;
 }
 
 template<> CefRefPtr<CefBrowserHost> CefCppToCRefCounted<CefBrowserHostCppToC,

libcef_dll/cpptoc/render_handler_cpptoc.cc

@@ -10,6 +10,7 @@
 // for more information.
 //
 
+#include "libcef_dll/cpptoc/accessibility_handler_cpptoc.h"
 #include "libcef_dll/cpptoc/render_handler_cpptoc.h"
 #include "libcef_dll/ctocpp/browser_ctocpp.h"
 #include "libcef_dll/ctocpp/drag_data_ctocpp.h"
@@ -19,6 +20,22 @@ namespace {
 
 // MEMBER FUNCTIONS - Body may be edited by hand.
 
+cef_accessibility_handler_t* CEF_CALLBACK render_handler_get_accessibility_handler(
+    struct _cef_render_handler_t* self) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return NULL;
+
+  // Execute
+  CefRefPtr<CefAccessibilityHandler> _retval = CefRenderHandlerCppToC::Get(
+      self)->GetAccessibilityHandler();
+
+  // Return type: refptr_same
+  return CefAccessibilityHandlerCppToC::Wrap(_retval);
+}
+
 int CEF_CALLBACK render_handler_get_root_screen_rect(
     struct _cef_render_handler_t* self, cef_browser_t* browser,
     cef_rect_t* rect) {
@@ -396,6 +413,8 @@ void CEF_CALLBACK render_handler_on_ime_composition_range_changed(
 // CONSTRUCTOR - Do not edit by hand.
 
 CefRenderHandlerCppToC::CefRenderHandlerCppToC() {
+  GetStruct()->get_accessibility_handler =
+      render_handler_get_accessibility_handler;
   GetStruct()->get_root_screen_rect = render_handler_get_root_screen_rect;
   GetStruct()->get_view_rect = render_handler_get_view_rect;
   GetStruct()->get_screen_point = render_handler_get_screen_point;