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accessibility_plugin.cc
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1 // Copyright 2013 The Flutter Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "flutter/shell/platform/windows/accessibility_plugin.h"
6
7 #include <variant>
8
9 #include "flutter/fml/logging.h"
10 #include "flutter/fml/platform/win/wstring_conversion.h"
11 #include "flutter/shell/platform/common/client_wrapper/include/flutter/standard_message_codec.h"
12 #include "flutter/shell/platform/windows/flutter_windows_engine.h"
13 #include "flutter/shell/platform/windows/flutter_windows_view.h"
14
15 namespace flutter {
16
17 namespace {
18
19 static constexpr char kAccessibilityChannelName[] = "flutter/accessibility";
20 static constexpr char kTypeKey[] = "type";
21 static constexpr char kDataKey[] = "data";
22 static constexpr char kMessageKey[] = "message";
23 static constexpr char kAnnounceValue[] = "announce";
24
25 // Handles messages like:
26 // {"type": "announce", "data": {"message": "Hello"}}
27 void HandleMessage(AccessibilityPlugin* plugin, const EncodableValue& message) {
28 const auto* map = std::get_if<EncodableMap>(&message);
29 if (!map) {
30 FML_LOG(ERROR) << "Accessibility message must be a map.";
31 return;
32 }
33 const auto& type_itr = map->find(EncodableValue{kTypeKey});
34 const auto& data_itr = map->find(EncodableValue{kDataKey});
35 if (type_itr == map->end()) {
36 FML_LOG(ERROR) << "Accessibility message must have a 'type' property.";
37 return;
38 }
39 if (data_itr == map->end()) {
40 FML_LOG(ERROR) << "Accessibility message must have a 'data' property.";
41 return;
42 }
43 const auto* type = std::get_if<std::string>(&type_itr->second);
44 const auto* data = std::get_if<EncodableMap>(&data_itr->second);
45 if (!type) {
46 FML_LOG(ERROR) << "Accessibility message 'type' property must be a string.";
47 return;
48 }
49 if (!data) {
50 FML_LOG(ERROR) << "Accessibility message 'data' property must be a map.";
51 return;
52 }
53
54 if (type->compare(kAnnounceValue) == 0) {
55 const auto& message_itr = data->find(EncodableValue{kMessageKey});
56 if (message_itr == data->end()) {
57 return;
58 }
59 const auto* message = std::get_if<std::string>(&message_itr->second);
60 if (!message) {
61 return;
62 }
63
64 plugin->Announce(*message);
65 } else {
66 FML_LOG(WARNING) << "Accessibility message type '" << *type
67 << "' is not supported.";
68 }
69 }
70
71 } // namespace
72
73 AccessibilityPlugin::AccessibilityPlugin(FlutterWindowsEngine* engine)
74 : engine_(engine) {}
75
76 void AccessibilityPlugin::SetUp(BinaryMessenger* binary_messenger,
77 AccessibilityPlugin* plugin) {
78 BasicMessageChannel<> channel{binary_messenger, kAccessibilityChannelName,
79 &StandardMessageCodec::GetInstance()};
80
81 channel.SetMessageHandler(
82 [plugin](const EncodableValue& message,
83 const MessageReply<EncodableValue>& reply) {
84 HandleMessage(plugin, message);
85
86 // The accessibility channel does not support error handling.
87 // Always return an empty response even on failure.
88 reply(EncodableValue{std::monostate{}});
89 });
90 }
91
92 void AccessibilityPlugin::Announce(const std::string_view message) {
93 if (!engine_->semantics_enabled()) {
94 return;
95 }
96
97 // TODO(loicsharma): Remove implicit view assumption.
98 // https://github.com/flutter/flutter/issues/142845
99 auto view = engine_->view(kImplicitViewId);
100 if (!view) {
101 return;
102 }
103
104 std::wstring wide_text = fml::Utf8ToWideString(message);
105 view->AnnounceAlert(wide_text);
106 }
107
108 } // namespace flutter
accessibility_plugin.h
flutter::AccessibilityPlugin
Definition: accessibility_plugin.h:21
flutter::AccessibilityPlugin::AccessibilityPlugin
AccessibilityPlugin(FlutterWindowsEngine *engine)
Definition: accessibility_plugin.cc:73
flutter::AccessibilityPlugin::Announce
virtual void Announce(const std::string_view message)
Definition: accessibility_plugin.cc:92
flutter::AccessibilityPlugin::SetUp
static void SetUp(BinaryMessenger *binary_messenger, AccessibilityPlugin *plugin)
Definition: accessibility_plugin.cc:76
flutter::BasicMessageChannel
Definition: basic_message_channel.h:56
flutter::BinaryMessenger
Definition: binary_messenger.h:28
flutter::EncodableValue
Definition: encodable_value.h:165
flutter::FlutterWindowsEngine
Definition: flutter_windows_engine.h:90
flutter::FlutterWindowsEngine::view
FlutterWindowsView * view(FlutterViewId view_id) const
Definition: flutter_windows_engine.cc:674
flutter::FlutterWindowsEngine::semantics_enabled
bool semantics_enabled() const
Definition: flutter_windows_engine.h:249
flutter::StandardMessageCodec::GetInstance
static const StandardMessageCodec & GetInstance(const StandardCodecSerializer *serializer=nullptr)
Definition: standard_codec.cc:293
kAccessibilityChannelName
static constexpr char kAccessibilityChannelName[]
Definition: flutter_windows_engine.cc:34
flutter_windows_engine.h
flutter_windows_view.h
type
enum flutter::testing::@88::KeyboardChange::Type type
message
Win32Message message
Definition: keyboard_unittests.cc:137
flutter
Definition: accessibility_bridge_windows.cc:11
flutter::kImplicitViewId
constexpr FlutterViewId kImplicitViewId
Definition: flutter_windows_engine.h:55
flutter::MessageReply
std::function< void(const T &reply)> MessageReply
Definition: basic_message_channel.h:43
standard_message_codec.h