218151583f
_This is the same pull request as https://github.com/flutter/engine/pull/50898. GitHub broke on the previous pull request so I re-created it_ This moves the logic to handle `flutter/accessibility` messages to a new type, `AccessibilityPlugin`. Notable changes: 1. Windows app no longer crashes if it receives accessibility events it does not support 2. Windows app no longer crashes if it receives accessibility events while in headless mode @yaakovschectman After playing around with this, I ended up using a different pattern than what what I suggested on https://github.com/flutter/engine/pull/50598#discussion_r1488728089. This message handler is simple enough that splitting into a child/base types felt like unnecessary boilerplate. The key thing is separating messaging and implementation logic, which was achieved through the `SetUp` method. Let me know what you think, and sorry for all my flip-flopping on this topic! ð This is preparation for: https://github.com/flutter/flutter/issues/143765 Sample app for manual testing: https://github.com/flutter/flutter/issues/113059 [C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
109 lines
3.5 KiB
C++
109 lines
3.5 KiB
C++
// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "flutter/shell/platform/windows/accessibility_plugin.h"
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#include <variant>
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#include "flutter/fml/logging.h"
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#include "flutter/fml/platform/win/wstring_conversion.h"
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#include "flutter/shell/platform/common/client_wrapper/include/flutter/standard_message_codec.h"
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#include "flutter/shell/platform/windows/flutter_windows_engine.h"
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#include "flutter/shell/platform/windows/flutter_windows_view.h"
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namespace flutter {
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namespace {
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static constexpr char kAccessibilityChannelName[] = "flutter/accessibility";
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static constexpr char kTypeKey[] = "type";
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static constexpr char kDataKey[] = "data";
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static constexpr char kMessageKey[] = "message";
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static constexpr char kAnnounceValue[] = "announce";
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// Handles messages like:
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// {"type": "announce", "data": {"message": "Hello"}}
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void HandleMessage(AccessibilityPlugin* plugin, const EncodableValue& message) {
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const auto* map = std::get_if<EncodableMap>(&message);
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if (!map) {
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FML_LOG(ERROR) << "Accessibility message must be a map.";
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return;
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}
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const auto& type_itr = map->find(EncodableValue{kTypeKey});
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const auto& data_itr = map->find(EncodableValue{kDataKey});
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if (type_itr == map->end()) {
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FML_LOG(ERROR) << "Accessibility message must have a 'type' property.";
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return;
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}
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if (data_itr == map->end()) {
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FML_LOG(ERROR) << "Accessibility message must have a 'data' property.";
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return;
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}
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const auto* type = std::get_if<std::string>(&type_itr->second);
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const auto* data = std::get_if<EncodableMap>(&data_itr->second);
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if (!type) {
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FML_LOG(ERROR) << "Accessibility message 'type' property must be a string.";
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return;
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}
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if (!data) {
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FML_LOG(ERROR) << "Accessibility message 'data' property must be a map.";
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return;
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}
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if (type->compare(kAnnounceValue) == 0) {
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const auto& message_itr = data->find(EncodableValue{kMessageKey});
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if (message_itr == data->end()) {
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return;
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}
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const auto* message = std::get_if<std::string>(&message_itr->second);
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if (!message) {
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return;
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}
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plugin->Announce(*message);
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} else {
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FML_LOG(ERROR) << "Accessibility message type '" << *type
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<< "' is not supported.";
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}
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}
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} // namespace
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AccessibilityPlugin::AccessibilityPlugin(FlutterWindowsEngine* engine)
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: engine_(engine) {}
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void AccessibilityPlugin::SetUp(BinaryMessenger* binary_messenger,
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AccessibilityPlugin* plugin) {
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BasicMessageChannel<> channel{binary_messenger, kAccessibilityChannelName,
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&StandardMessageCodec::GetInstance()};
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channel.SetMessageHandler(
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[plugin](const EncodableValue& message,
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const MessageReply<EncodableValue>& reply) {
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HandleMessage(plugin, message);
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// The accessibility channel does not support error handling.
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// Always return an empty response even on failure.
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reply(EncodableValue{std::monostate{}});
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});
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}
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void AccessibilityPlugin::Announce(const std::string_view message) {
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if (!engine_->semantics_enabled()) {
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return;
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}
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// TODO(loicsharma): Remove implicit view assumption.
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// https://github.com/flutter/flutter/issues/142845
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auto view = engine_->view(kImplicitViewId);
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if (!view) {
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return;
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}
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std::wstring wide_text = fml::Utf8ToWideString(message);
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view->AnnounceAlert(wide_text);
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}
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} // namespace flutter
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