Announce alerts through SemanticsService on Windows

ci/licenses_golden/licenses_flutter

@@ -3059,9 +3059,13 @@ FILE: ../../../flutter/shell/platform/linux/public/flutter_linux/fl_texture_regi
 FILE: ../../../flutter/shell/platform/linux/public/flutter_linux/fl_value.h
 FILE: ../../../flutter/shell/platform/linux/public/flutter_linux/fl_view.h
 FILE: ../../../flutter/shell/platform/linux/public/flutter_linux/flutter_linux.h
+FILE: ../../../flutter/shell/platform/windows/accessibility_alert.cc
+FILE: ../../../flutter/shell/platform/windows/accessibility_alert.h
 FILE: ../../../flutter/shell/platform/windows/accessibility_bridge_delegate_windows.cc
 FILE: ../../../flutter/shell/platform/windows/accessibility_bridge_delegate_windows.h
 FILE: ../../../flutter/shell/platform/windows/accessibility_bridge_delegate_windows_unittests.cc
+FILE: ../../../flutter/shell/platform/windows/accessibility_root_node.cc
+FILE: ../../../flutter/shell/platform/windows/accessibility_root_node.h
 FILE: ../../../flutter/shell/platform/windows/angle_surface_manager.cc
 FILE: ../../../flutter/shell/platform/windows/angle_surface_manager.h
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/dart_project_unittests.cc

shell/platform/windows/BUILD.gn

@@ -38,8 +38,12 @@ source_set("flutter_windows_headers") {
 source_set("flutter_windows_source") {
   # Common Windows sources.
   sources = [
+    "accessibility_alert.cc",
+    "accessibility_alert.h",
     "accessibility_bridge_delegate_windows.cc",
     "accessibility_bridge_delegate_windows.h",
+    "accessibility_root_node.cc",
+    "accessibility_root_node.h",
     "angle_surface_manager.cc",
     "angle_surface_manager.h",
     "cursor_handler.cc",

shell/platform/windows/accessibility_alert.cc

@@ -0,0 +1,168 @@
+// Copyright 2013 The Flutter 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 "flutter/shell/platform/windows/accessibility_alert.h"
+
+#include "flutter/shell/platform/windows/accessibility_root_node.h"
+
+namespace flutter {
+
+AccessibilityAlert::AccessibilityAlert() : text_(L""), parent_(nullptr) {}
+
+// IAccessible methods.
+
+IFACEMETHODIMP AccessibilityAlert::accHitTest(LONG screen_physical_pixel_x,
+                                              LONG screen_physical_pixel_y,
+                                              VARIANT* child) {
+  child->vt = VT_EMPTY;
+  return S_FALSE;
+}
+
+// Performs the object's default action.
+IFACEMETHODIMP AccessibilityAlert::accDoDefaultAction(VARIANT var_id) {
+  return E_FAIL;
+}
+
+// Retrieves an IDispatch interface pointer for the specified child.
+IFACEMETHODIMP AccessibilityAlert::get_accChild(VARIANT var_child,
+                                                IDispatch** disp_child) {
+  if (V_VT(&var_child) == VT_I4 && V_I4(&var_child) == CHILDID_SELF) {
+    *disp_child = this;
+    AddRef();
+    return S_OK;
+  }
+  *disp_child = nullptr;
+  return E_FAIL;
+}
+
+// Retrieves the number of accessible children.
+IFACEMETHODIMP AccessibilityAlert::get_accChildCount(LONG* child_count) {
+  *child_count = 0;
+  return S_OK;
+}
+
+// Retrieves the tooltip description.
+IFACEMETHODIMP AccessibilityAlert::get_accDescription(VARIANT var_id,
+                                                      BSTR* desc) {
+  *desc = SysAllocString(text_.c_str());
+  return S_OK;
+}
+
+// Retrieves the name of the specified object.
+IFACEMETHODIMP AccessibilityAlert::get_accName(VARIANT var_id, BSTR* name) {
+  *name = SysAllocString(text_.c_str());
+  return S_OK;
+}
+
+// Retrieves the IDispatch interface of the object's parent.
+IFACEMETHODIMP AccessibilityAlert::get_accParent(IDispatch** disp_parent) {
+  *disp_parent = parent_;
+  if (*disp_parent) {
+    (*disp_parent)->AddRef();
+    return S_OK;
+  }
+  return S_FALSE;
+}
+
+// Retrieves information describing the role of the specified object.
+IFACEMETHODIMP AccessibilityAlert::get_accRole(VARIANT var_id, VARIANT* role) {
+  *role = {.vt = VT_I4, .lVal = ROLE_SYSTEM_ALERT};
+  return S_OK;
+}
+
+// Retrieves the current state of the specified object.
+IFACEMETHODIMP AccessibilityAlert::get_accState(VARIANT var_id,
+                                                VARIANT* state) {
+  *state = {.vt = VT_I4, .lVal = STATE_SYSTEM_DEFAULT};
+  return S_OK;
+}
+
+// Gets the help string for the specified object.
+IFACEMETHODIMP AccessibilityAlert::get_accHelp(VARIANT var_id, BSTR* help) {
+  *help = SysAllocString(L"");
+  return S_OK;
+}
+
+// Retrieve or set the string value associated with the specified object.
+// Setting the value is not typically used by screen readers, but it's
+// used frequently by automation software.
+IFACEMETHODIMP AccessibilityAlert::get_accValue(VARIANT var_id, BSTR* value) {
+  *value = SysAllocString(text_.c_str());
+  return S_OK;
+}
+
+// IAccessible methods not implemented.
+IFACEMETHODIMP AccessibilityAlert::get_accSelection(VARIANT* selected) {
+  selected->vt = VT_EMPTY;
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::accSelect(LONG flags_sel, VARIANT var_id) {
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::put_accValue(VARIANT var_id,
+                                                BSTR new_value) {
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::get_accFocus(VARIANT* focus_child) {
+  focus_child->vt = VT_EMPTY;
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::get_accHelpTopic(BSTR* help_file,
+                                                    VARIANT var_id,
+                                                    LONG* topic_id) {
+  if (help_file) {
+    *help_file = nullptr;
+  }
+  if (topic_id) {
+    *topic_id = 0;
+  }
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::put_accName(VARIANT var_id, BSTR put_name) {
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::get_accKeyboardShortcut(VARIANT var_id,
+                                                           BSTR* access_key) {
+  *access_key = nullptr;
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::accLocation(LONG* physical_pixel_left,
+                                               LONG* physical_pixel_top,
+                                               LONG* width,
+                                               LONG* height,
+                                               VARIANT var_id) {
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::accNavigate(LONG nav_dir,
+                                               VARIANT start,
+                                               VARIANT* end) {
+  end->vt = VT_EMPTY;
+  return E_NOTIMPL;
+}
+
+IFACEMETHODIMP AccessibilityAlert::get_accDefaultAction(VARIANT var_id,
+                                                        BSTR* default_action) {
+  *default_action = nullptr;
+  return E_NOTIMPL;
+}
+
+// End of IAccessible methods.
+
+void AccessibilityAlert::SetText(const std::wstring& text) {
+  text_ = text;
+}
+
+void AccessibilityAlert::SetParent(AccessibilityRootNode* parent) {
+  parent_ = parent;
+}
+
+}  // namespace flutter

shell/platform/windows/accessibility_alert.h

@@ -0,0 +1,110 @@
+// Copyright 2013 The Flutter 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 FLUTTER_SHELL_PLATFORM_WINDOWS_ACCESSIBILITY_ALERT_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_ACCESSIBILITY_ALERT_H_
+
+#include <atlbase.h>
+#include <atlcom.h>
+#include <oleacc.h>
+
+#include <string>
+
+namespace flutter {
+
+class AccessibilityRootNode;
+
+// An IAccessible node representing an alert read to the screen reader.
+// When an announcement is requested by the framework, an instance of
+// this class, if none exists already, is created and made a child of
+// the root AccessibilityRootNode node, and is therefore also a sibling
+// of the window's root node.
+// This node is not interactable to the user.
+class AccessibilityAlert : public CComObjectRootEx<CComMultiThreadModel>,
+                           public IDispatchImpl<IAccessible> {
+ public:
+  BEGIN_COM_MAP(AccessibilityAlert)
+  COM_INTERFACE_ENTRY(IAccessible)
+  END_COM_MAP()
+  //
+  // IAccessible methods.
+  //
+
+  // Retrieves the child element or child object at a given point on the screen.
+  IFACEMETHODIMP accHitTest(LONG screen_physical_pixel_x,
+                            LONG screen_physical_pixel_y,
+                            VARIANT* child) override;
+
+  // Retrieves an IDispatch interface pointer for the specified child.
+  IFACEMETHODIMP get_accChild(VARIANT var_child,
+                              IDispatch** disp_child) override;
+
+  // Retrieves the number of accessible children.
+  IFACEMETHODIMP get_accChildCount(LONG* child_count) override;
+
+  // Retrieves a string that describes the object's default action.
+  IFACEMETHODIMP get_accDefaultAction(VARIANT var_id,
+                                      BSTR* default_action) override;
+
+  // Retrieves the tooltip description.
+  IFACEMETHODIMP get_accDescription(VARIANT var_id, BSTR* desc) override;
+
+  // Retrieves the name of the specified object.
+  IFACEMETHODIMP get_accName(VARIANT var_id, BSTR* name) override;
+
+  // Retrieves the IDispatch interface of the object's parent.
+  IFACEMETHODIMP get_accParent(IDispatch** disp_parent) override;
+
+  // Retrieves information describing the role of the specified object.
+  IFACEMETHODIMP get_accRole(VARIANT var_id, VARIANT* role) override;
+
+  // Retrieves the current state of the specified object.
+  IFACEMETHODIMP get_accState(VARIANT var_id, VARIANT* state) override;
+
+  // Gets the help string for the specified object.
+  IFACEMETHODIMP get_accHelp(VARIANT var_id, BSTR* help) override;
+
+  // Retrieve the string value associated with the specified object.
+  IFACEMETHODIMP get_accValue(VARIANT var_id, BSTR* value) override;
+
+  // IAccessible methods not implemented.
+  IFACEMETHODIMP accLocation(LONG* physical_pixel_left,
+                             LONG* physical_pixel_top,
+                             LONG* width,
+                             LONG* height,
+                             VARIANT var_id) override;
+  IFACEMETHODIMP accNavigate(LONG nav_dir,
+                             VARIANT start,
+                             VARIANT* end) override;
+  IFACEMETHODIMP accDoDefaultAction(VARIANT var_id) override;
+  IFACEMETHODIMP get_accFocus(VARIANT* focus_child) override;
+  IFACEMETHODIMP get_accKeyboardShortcut(VARIANT var_id,
+                                         BSTR* access_key) override;
+  IFACEMETHODIMP get_accSelection(VARIANT* selected) override;
+  IFACEMETHODIMP accSelect(LONG flags_sel, VARIANT var_id) override;
+  IFACEMETHODIMP get_accHelpTopic(BSTR* help_file,
+                                  VARIANT var_id,
+                                  LONG* topic_id) override;
+  IFACEMETHODIMP put_accName(VARIANT var_id, BSTR put_name) override;
+  IFACEMETHODIMP put_accValue(VARIANT var_id, BSTR new_value) override;
+
+  // End of IAccessible methods.
+
+  AccessibilityAlert();
+  ~AccessibilityAlert() = default;
+
+  // Sets the text of this alert to the provided message.
+  void SetText(const std::wstring& text);
+
+  void SetParent(AccessibilityRootNode* parent);
+
+ private:
+  std::wstring text_;
+
+  AccessibilityRootNode* parent_;
+};
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_ACCESSIBILITY_ALERT_H_