runtime/flutter_runner/semantics_bridge.h

// Copyright 2018 The Fuchsia 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 TOPAZ_RUNTIME_FLUTTER_RUNNER_SEMANTICS_BRIDGE_H_
#define TOPAZ_RUNTIME_FLUTTER_RUNNER_SEMANTICS_BRIDGE_H_

#include <map>
#include <unordered_set>

#include <fuchsia/accessibility/cpp/fidl.h>
#include <fuchsia/sys/cpp/fidl.h>
#include <fuchsia/ui/input/cpp/fidl.h>

#include "flutter/lib/ui/semantics/semantics_node.h"
#include "flutter/lib/ui/window/viewport_metrics.h"
#include "lib/fidl/cpp/binding_set.h"

#include "flutter/shell/common/platform_view.h"

namespace flutter_runner {

// Connects the Flutter PlatformView to the Fuchsia accessibility manager and
// provides a way to push semantic tree updates to the manager. Also provides
// a SemanticsProvider implementation for the manager to call SemanticActions
// on nodes on the screen.
class SemanticsBridge final : public fuchsia::accessibility::SemanticsProvider {
 public:
  SemanticsBridge(flutter::PlatformView* platform_view,
                  flutter::LogicalMetrics* metrics);
  ~SemanticsBridge() = default;

  // Store the associated PlatformView's view_id and
  // environment_service_provider to make necessary connections to |root_| and
  // |a11y_toggle_|.
  void SetupEnvironment(
      uint32_t view_id,
      fuchsia::sys::ServiceProvider* environment_service_provider);

  // Converts the updated semantics nodes in |update| to Fidl accessibility
  // node format to send to the accessibility manager. The update is split into
  // three manager calls, one to send updated nodes, one to send deleted node
  // ids, and one to finalize the update.
  void UpdateSemantics(const flutter::SemanticsNodeUpdates& update);

 private:
  // |fuchsia::accessibility::SemanticsProvider|
  void PerformAccessibilityAction(
      int32_t node_id, fuchsia::accessibility::Action action) override;

  // On enabling, sets up a connection to the accessibility manager with
  // the view id passed in from the PlatformView. In order for Flutter to
  // start sending semantics updates, we must call SetSemanticsEnabled(true)
  // in the associated |platform_view_|.
  // On disabling, we disable Flutter from sending semantic updates and break
  // the connection to the accessibility manager.
  void OnAccessibilityToggle(bool enabled);

  fidl::Binding<fuchsia::accessibility::SemanticsProvider> binding_;

  // We keep a reference to the PlatformView's environment service provider
  // to connect to the |fuchsia::accessibility::SemanticsRoot| service
  // and the |fuchsia::accessibility::ToggleBroadcaster| service.
  fuchsia::sys::ServiceProvider* environment_service_provider_;
  fuchsia::accessibility::SemanticsRootPtr root_;
  fuchsia::accessibility::ToggleBroadcasterPtr a11y_toggle_;
  // We keep track of the current on/off state;
  bool enabled_ = false;

  // The associated Scenic view id for the associated PlatformView. This id
  // must registered with the accessibility manager, and sent with every
  // update, delete, and commit.
  // TODO(SCN-847): Update the view_id system to initialize connections with
  // event pair kernel objects.
  uint32_t view_id_;
  // We must make sure that we have a valid view id and environment service
  // provider before registering with the a11y manager.
  bool environment_set_ = false;
  // We keep a reference to the associated PlatformView to call
  // SemanticsActions.
  flutter::PlatformView* platform_view_;
  // Metrics is needed to scale Scenic view space into local
  // Flutter space when performing hit-tests. This is converted into
  // a transform matrix that is applied to this semantic tree's root node
  // transform matrix when sent to the manager.
  flutter::LogicalMetrics* metrics_;

  // Disallow copy and assignment.
  SemanticsBridge(const SemanticsBridge&) = delete;
  SemanticsBridge& operator=(const SemanticsBridge&) = delete;
};

}  // namespace flutter_runner

#endif  // TOPAZ_RUNTIME_FLUTTER_RUNNER_SEMANTICS_BRIDGE_H_