Add initial accessibility support to the Linux shell

Author: robert-ancell

ci/licenses_golden/licenses_flutter

@@ -1299,6 +1299,10 @@ FILE: ../../../flutter/shell/platform/glfw/text_input_plugin.h
 FILE: ../../../flutter/shell/platform/linux/egl_utils.cc
 FILE: ../../../flutter/shell/platform/linux/egl_utils.h
 FILE: ../../../flutter/shell/platform/linux/egl_utils_test.cc
+FILE: ../../../flutter/shell/platform/linux/fl_accessibility_plugin.cc
+FILE: ../../../flutter/shell/platform/linux/fl_accessibility_plugin.h
+FILE: ../../../flutter/shell/platform/linux/fl_accessibile.cc
+FILE: ../../../flutter/shell/platform/linux/fl_accessibile.h
 FILE: ../../../flutter/shell/platform/linux/fl_basic_message_channel.cc
 FILE: ../../../flutter/shell/platform/linux/fl_basic_message_channel_test.cc
 FILE: ../../../flutter/shell/platform/linux/fl_binary_codec.cc
@@ -1359,6 +1363,8 @@ FILE: ../../../flutter/shell/platform/linux/fl_text_input_plugin.h
 FILE: ../../../flutter/shell/platform/linux/fl_value.cc
 FILE: ../../../flutter/shell/platform/linux/fl_value_test.cc
 FILE: ../../../flutter/shell/platform/linux/fl_view.cc
+FILE: ../../../flutter/shell/platform/linux/fl_view_accessible.cc
+FILE: ../../../flutter/shell/platform/linux/fl_view_accessible.h
 FILE: ../../../flutter/shell/platform/linux/public/flutter_linux/fl_basic_message_channel.h
 FILE: ../../../flutter/shell/platform/linux/public/flutter_linux/fl_binary_codec.h
 FILE: ../../../flutter/shell/platform/linux/public/flutter_linux/fl_binary_messenger.h

shell/platform/linux/BUILD.gn

@@ -88,6 +88,8 @@ source_set("flutter_linux_sources") {
 
   sources = [
     "egl_utils.cc",
+    "fl_accessibility_plugin.cc",
+    "fl_accessible.cc",
     "fl_basic_message_channel.cc",
     "fl_binary_codec.cc",
     "fl_binary_messenger.cc",
@@ -116,6 +118,7 @@ source_set("flutter_linux_sources") {
     "fl_text_input_plugin.cc",
     "fl_value.cc",
     "fl_view.cc",
+    "fl_view_accessible.cc",
   ]
 
   # Set flag to stop headers being directly included (library users should not do this)

shell/platform/linux/fl_accessibility_plugin.cc

@@ -0,0 +1,58 @@
+// 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/linux/fl_accessibility_plugin.h"
+#include "flutter/shell/platform/linux/fl_accessible.h"
+#include "flutter/shell/platform/linux/fl_view_accessible.h"
+
+struct _FlAccessibilityPlugin {
+  GObject parent_instance;
+
+  FlView* view;
+};
+
+G_DEFINE_TYPE(FlAccessibilityPlugin, fl_accessibility_plugin, G_TYPE_OBJECT)
+
+static void view_weak_notify_cb(gpointer user_data, GObject* object) {
+  FlAccessibilityPlugin* self = FL_ACCESSIBILITY_PLUGIN(object);
+  self->view = nullptr;
+}
+
+static void fl_accessibility_plugin_dispose(GObject* object) {
+  FlAccessibilityPlugin* self = FL_ACCESSIBILITY_PLUGIN(object);
+
+  if (self->view != nullptr) {
+    g_object_weak_unref(G_OBJECT(self->view), view_weak_notify_cb, self);
+    self->view = nullptr;
+  }
+
+  G_OBJECT_CLASS(fl_accessibility_plugin_parent_class)->dispose(object);
+}
+
+static void fl_accessibility_plugin_class_init(
+    FlAccessibilityPluginClass* klass) {
+  G_OBJECT_CLASS(klass)->dispose = fl_accessibility_plugin_dispose;
+}
+
+static void fl_accessibility_plugin_init(FlAccessibilityPlugin* self) {}
+
+FlAccessibilityPlugin* fl_accessibility_plugin_new(FlView* view) {
+  FlAccessibilityPlugin* self = FL_ACCESSIBILITY_PLUGIN(
+      g_object_new(fl_accessibility_plugin_get_type(), nullptr));
+
+  self->view = view;
+  g_object_weak_ref(G_OBJECT(view), view_weak_notify_cb, self);
+
+  return self;
+}
+
+void fl_accessibility_plugin_handle_update_semantics_node(
+    FlAccessibilityPlugin* self,
+    const FlutterSemanticsNode* node) {
+  if (self->view != nullptr) {
+    AtkObject* accessible = gtk_widget_get_accessible(GTK_WIDGET(self->view));
+    fl_view_accessible_handle_update_semantics_node(
+        FL_VIEW_ACCESSIBLE(accessible), node);
+  }
+}

shell/platform/linux/fl_accessibility_plugin.h

@@ -0,0 +1,50 @@
+// 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_LINUX_FL_ACCESSIBILITY_PLUGIN_H_
+#define FLUTTER_SHELL_PLATFORM_LINUX_FL_ACCESSIBILITY_PLUGIN_H_
+
+#include "flutter/shell/platform/linux/public/flutter_linux/fl_view.h"
+
+#include "flutter/shell/platform/embedder/embedder.h"
+
+G_BEGIN_DECLS
+
+G_DECLARE_FINAL_TYPE(FlAccessibilityPlugin,
+                     fl_accessibility_plugin,
+                     FL,
+                     ACCESSIBILITY_PLUGIN,
+                     GObject);
+
+/**
+ * FlAccessibilityPlugin:
+ *
+ * #FlAccessibilityPlugin is a plugin that handles semantic node updates and
+ * converts them to ATK events.
+ */
+
+/**
+ * fl_accessibility_plugin_new:
+ * @view: an #FlView to export accessibility information to.
+ *
+ * Creates a new plugin handles semantic node updates.
+ *
+ * Returns: a new #FlAccessibilityPlugin.
+ */
+FlAccessibilityPlugin* fl_accessibility_plugin_new(FlView* view);
+
+/**
+ * fl_accessibility_plugin_handle_update_semantics_node:
+ * @plugin: an #FlAccessibilityPlugin.
+ * @node: semantic node information.
+ *
+ * Handle a semantics node update.
+ */
+void fl_accessibility_plugin_handle_update_semantics_node(
+    FlAccessibilityPlugin* plugin,
+    const FlutterSemanticsNode* node);
+
+G_END_DECLS
+
+#endif  // FLUTTER_SHELL_PLATFORM_LINUX_FL_ACCESSIBILITY_PLUGIN_H_