shell/platform/fuchsia/flutter/focus_delegate.h

// 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_FUCHSIA_FOCUS_DELEGATE_H_
#define FLUTTER_SHELL_PLATFORM_FUCHSIA_FOCUS_DELEGATE_H_

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

#include "flutter/fml/macros.h"
#include "flutter/lib/ui/window/platform_message.h"
#include "third_party/rapidjson/include/rapidjson/document.h"

namespace flutter_runner {

class FocusDelegate {
 public:
  FocusDelegate(fidl::InterfaceHandle<fuchsia::ui::views::ViewRefFocused>
                    view_ref_focused,
                fidl::InterfaceHandle<fuchsia::ui::views::Focuser> focuser)
      : view_ref_focused_(view_ref_focused.Bind()), focuser_(focuser.Bind()) {}

  /// Continuously watches the host viewRef for focus events, invoking a
  /// callback each time.
  ///
  /// The callback is invoked on each Watch() call, which consumes the callback
  /// argument. Hence, the callback argument must be copyable, so that a copy
  /// can be freely moved into the Watch() call.
  ///
  /// This method can only be called once.
  void WatchLoop(std::function<void(bool)> callback);

  /// Handles the following focus-related platform message requests:
  /// View.focus.getCurrent
  ///  - Completes with the FocusDelegate's most recent focus state, either
  ///    [true] or [false].
  /// View.focus.getNext
  ///  - Completes with the FocusDelegate's next focus state, either [true] or
  ///    [false].
  ///  - Only one outstanding request may exist at a time. Any others will be
  ///    completed with [null].
  /// View.focus.request
  ///  - Attempts to give focus for a given viewRef. Completes with [0] on
  ///    success, or [fuchsia::ui::views::Error] on failure.
  ///
  /// Returns false if a malformed/invalid request needs to be completed empty.
  bool HandlePlatformMessage(
      rapidjson::Value request,
      fml::RefPtr<flutter::PlatformMessageResponse> response);

 private:
  fuchsia::ui::views::ViewRefFocusedPtr view_ref_focused_;
  fuchsia::ui::views::FocuserPtr focuser_;

  std::function<void(fuchsia::ui::views::FocusState)> watch_loop_;
  bool is_focused_ = false;
  fml::RefPtr<flutter::PlatformMessageResponse> next_focus_request_;

  void Complete(fml::RefPtr<flutter::PlatformMessageResponse> response,
                std::string value);

  /// Completes a platform message request by attempting to give focus for a
  /// given viewRef.
  bool RequestFocus(rapidjson::Value request,
                    fml::RefPtr<flutter::PlatformMessageResponse> response);

  FML_DISALLOW_COPY_AND_ASSIGN(FocusDelegate);
};

}  // namespace flutter_runner
#endif  // FLUTTER_SHELL_PLATFORM_FUCHSIA_FOCUS_DELEGATE_H_