rustdesk/flutter/lib/mobile/pages/view_camera_page.dart

import 'dart:async';
import 'dart:ui' as ui;

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_hbb/common/shared_state.dart';
import 'package:flutter_hbb/common/widgets/toolbar.dart';
import 'package:flutter_hbb/consts.dart';
import 'package:flutter_hbb/models/chat_model.dart';
import 'package:flutter_keyboard_visibility/flutter_keyboard_visibility.dart';
import 'package:flutter_svg/svg.dart';
import 'package:get/get.dart';
import 'package:provider/provider.dart';

import '../../common.dart';
import '../../common/widgets/overlay.dart';
import '../../common/widgets/dialog.dart';
import '../../common/widgets/remote_input.dart';
import '../../models/input_model.dart';
import '../../models/model.dart';
import '../../models/platform_model.dart';
import '../../utils/image.dart';

final initText = '1' * 1024;

// Workaround for Android (default input method, Microsoft SwiftKey keyboard) when using physical keyboard.
// When connecting a physical keyboard, `KeyEvent.physicalKey.usbHidUsage` are wrong is using Microsoft SwiftKey keyboard.
// https://github.com/flutter/flutter/issues/159384
// https://github.com/flutter/flutter/issues/159383
void _disableAndroidSoftKeyboard({bool? isKeyboardVisible}) {
  if (isAndroid) {
    if (isKeyboardVisible != true) {
      // `enable_soft_keyboard` will be set to `true` when clicking the keyboard icon, in `openKeyboard()`.
      gFFI.invokeMethod("enable_soft_keyboard", false);
    }
  }
}

class ViewCameraPage extends StatefulWidget {
  ViewCameraPage(
      {Key? key,
      required this.id,
      this.loginMethod = '',
      this.password,
      this.isSharedPassword,
      this.forceRelay})
      : super(key: key);

  final String id;
  final String loginMethod;
  final String? password;
  final bool? isSharedPassword;
  final bool? forceRelay;

  @override
  State<ViewCameraPage> createState() => _ViewCameraPageState(id);
}

class _ViewCameraPageState extends State<ViewCameraPage>
    with WidgetsBindingObserver {
  Timer? _timer;
  bool _showBar = !isWebDesktop;
  bool _showGestureHelp = false;
  Orientation? _currentOrientation;
  double _viewInsetsBottom = 0;
  final _uniqueKey = UniqueKey();
  Timer? _timerDidChangeMetrics;

  final _blockableOverlayState = BlockableOverlayState();

  final keyboardVisibilityController = KeyboardVisibilityController();
  final FocusNode _mobileFocusNode = FocusNode();
  final FocusNode _physicalFocusNode = FocusNode();
  var _showEdit = false; // use soft keyboard

  InputModel get inputModel => gFFI.inputModel;
  SessionID get sessionId => gFFI.sessionId;

  final TextEditingController _textController =
      TextEditingController(text: initText);

  _ViewCameraPageState(String id) {
    initSharedStates(id);
    gFFI.chatModel.voiceCallStatus.value = VoiceCallStatus.notStarted;
    gFFI.dialogManager.loadMobileActionsOverlayVisible();
  }

  @override
  void initState() {
    super.initState();
    gFFI.ffiModel.updateEventListener(sessionId, widget.id);
    gFFI.start(
      widget.id,
      isViewCamera: true,
      loginMethod: widget.loginMethod,
      password: widget.password,
      isSharedPassword: widget.isSharedPassword,
      forceRelay: widget.forceRelay,
    );
    WidgetsBinding.instance.addPostFrameCallback((_) {
      SystemChrome.setEnabledSystemUIMode(SystemUiMode.manual, overlays: []);
      gFFI.dialogManager
          .showLoading(translate('Connecting...'), onCancel: closeConnection);
    });
    WakelockManager.enable(_uniqueKey);
    _physicalFocusNode.requestFocus();
    gFFI.inputModel.listenToMouse(true);
    gFFI.qualityMonitorModel.checkShowQualityMonitor(sessionId);
    gFFI.chatModel
        .changeCurrentKey(MessageKey(widget.id, ChatModel.clientModeID));
    _blockableOverlayState.applyFfi(gFFI);
    gFFI.imageModel.addCallbackOnFirstImage((String peerId) {
      gFFI.recordingModel
          .updateStatus(bind.sessionGetIsRecording(sessionId: gFFI.sessionId));
      if (gFFI.recordingModel.start) {
        showToast(translate('Automatically record outgoing sessions'));
      }
      _disableAndroidSoftKeyboard(
          isKeyboardVisible: keyboardVisibilityController.isVisible);
    });
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  Future<void> dispose() async {
    WidgetsBinding.instance.removeObserver(this);
    // https://github.com/flutter/flutter/issues/64935
    super.dispose();
    gFFI.dialogManager.hideMobileActionsOverlay(store: false);
    gFFI.inputModel.listenToMouse(false);
    gFFI.imageModel.disposeImage();
    gFFI.cursorModel.disposeImages();
    await gFFI.invokeMethod("enable_soft_keyboard", true);
    _mobileFocusNode.dispose();
    _physicalFocusNode.dispose();
    await gFFI.close();
    _timer?.cancel();
    _timerDidChangeMetrics?.cancel();
    gFFI.dialogManager.dismissAll();
    await SystemChrome.setEnabledSystemUIMode(SystemUiMode.manual,
        overlays: SystemUiOverlay.values);
    WakelockManager.disable(_uniqueKey);
    removeSharedStates(widget.id);
    // `on_voice_call_closed` should be called when the connection is ended.
    // The inner logic of `on_voice_call_closed` will check if the voice call is active.
    // Only one client is considered here for now.
    gFFI.chatModel.onVoiceCallClosed("End connection");
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {}

  @override
  void didChangeMetrics() {
    // If the soft keyboard is visible and the canvas has been changed(panned or scaled)
    // Don't try reset the view style and focus the cursor.
    if (gFFI.cursorModel.lastKeyboardIsVisible &&
        gFFI.canvasModel.isMobileCanvasChanged) {
      return;
    }

    final newBottom = MediaQueryData.fromView(ui.window).viewInsets.bottom;
    _timerDidChangeMetrics?.cancel();
    _timerDidChangeMetrics = Timer(Duration(milliseconds: 100), () async {
      // We need this comparation because poping up the floating action will also trigger `didChangeMetrics()`.
      if (newBottom != _viewInsetsBottom) {
        gFFI.canvasModel.mobileFocusCanvasCursor();
        _viewInsetsBottom = newBottom;
      }
    });
  }

  // to-do: It should be better to use transparent color instead of the bgColor.
  // But for now, the transparent color will cause the canvas to be white.
  // I'm sure that the white color is caused by the Overlay widget in BlockableOverlay.
  // But I don't know why and how to fix it.
  Widget emptyOverlay(Color bgColor) => BlockableOverlay(
        /// the Overlay key will be set with _blockableOverlayState in BlockableOverlay
        /// see override build() in [BlockableOverlay]
        state: _blockableOverlayState,
        underlying: Container(
          color: bgColor,
        ),
      );

  Widget _bottomWidget() => (_showBar && gFFI.ffiModel.pi.displays.isNotEmpty
      ? getBottomAppBar()
      : Offstage());

  @override
  Widget build(BuildContext context) {
    final keyboardIsVisible =
        keyboardVisibilityController.isVisible && _showEdit;
    final showActionButton = !_showBar || keyboardIsVisible || _showGestureHelp;

    return WillPopScope(
      onWillPop: () async {
        clientClose(sessionId, gFFI);
        return false;
      },
      child: Scaffold(
          // workaround for https://github.com/rustdesk/rustdesk/issues/3131
          floatingActionButtonLocation: keyboardIsVisible
              ? FABLocation(FloatingActionButtonLocation.endFloat, 0, -35)
              : null,
          floatingActionButton: !showActionButton
              ? null
              : FloatingActionButton(
                  mini: !keyboardIsVisible,
                  child: Icon(
                    (keyboardIsVisible || _showGestureHelp)
                        ? Icons.expand_more
                        : Icons.expand_less,
                    color: Colors.white,
                  ),
                  backgroundColor: MyTheme.accent,
                  onPressed: () {
                    setState(() {
                      if (keyboardIsVisible) {
                        _showEdit = false;
                        gFFI.invokeMethod("enable_soft_keyboard", false);
                        _mobileFocusNode.unfocus();
                        _physicalFocusNode.requestFocus();
                      } else if (_showGestureHelp) {
                        _showGestureHelp = false;
                      } else {
                        _showBar = !_showBar;
                      }
                    });
                  }),
          bottomNavigationBar: Obx(() => Stack(
                alignment: Alignment.bottomCenter,
                children: [
                  gFFI.ffiModel.pi.isSet.isTrue &&
                          gFFI.ffiModel.waitForFirstImage.isTrue
                      ? emptyOverlay(MyTheme.canvasColor)
                      : () {
                          gFFI.ffiModel.tryShowAndroidActionsOverlay();
                          return Offstage();
                        }(),
                  _bottomWidget(),
                  gFFI.ffiModel.pi.isSet.isFalse
                      ? emptyOverlay(MyTheme.canvasColor)
                      : Offstage(),
                ],
              )),
          body: Obx(
            () => getRawPointerAndKeyBody(Overlay(
              initialEntries: [
                OverlayEntry(builder: (context) {
                  return Container(
                    color: kColorCanvas,
                    child: SafeArea(
                      child: OrientationBuilder(builder: (ctx, orientation) {
                        if (_currentOrientation != orientation) {
                          Timer(const Duration(milliseconds: 200), () {
                            gFFI.dialogManager
                                .resetMobileActionsOverlay(ffi: gFFI);
                            _currentOrientation = orientation;
                            gFFI.canvasModel.updateViewStyle();
                          });
                        }
                        return Container(
                          color: MyTheme.canvasColor,
                          child: inputModel.isPhysicalMouse.value
                              ? getBodyForMobile()
                              : RawTouchGestureDetectorRegion(
                                  child: getBodyForMobile(),
                                  ffi: gFFI,
                                  isCamera: true,
                                ),
                        );
                      }),
                    ),
                  );
                })
              ],
            )),
          )),
    );
  }

  Widget getRawPointerAndKeyBody(Widget child) {
    return CameraRawPointerMouseRegion(
      inputModel: inputModel,
      // Disable RawKeyFocusScope before the connecting is established.
      // The "Delete" key on the soft keyboard may be grabbed when inputting the password dialog.
      child: gFFI.ffiModel.pi.isSet.isTrue
          ? RawKeyFocusScope(
              focusNode: _physicalFocusNode,
              inputModel: inputModel,
              child: child)
          : child,
    );
  }

  Widget getBottomAppBar() {
    return BottomAppBar(
      elevation: 10,
      color: MyTheme.accent,
      child: Row(
        mainAxisSize: MainAxisSize.max,
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: <Widget>[
          Row(
              children: <Widget>[
                    IconButton(
                      color: Colors.white,
                      icon: Icon(Icons.clear),
                      onPressed: () {
                        clientClose(sessionId, gFFI);
                      },
                    ),
                    IconButton(
                      color: Colors.white,
                      icon: Icon(Icons.tv),
                      onPressed: () {
                        setState(() => _showEdit = false);
                        showOptions(context, widget.id, gFFI.dialogManager);
                      },
                    )
                  ] +
                  (isWeb
                      ? []
                      : <Widget>[
                          futureBuilder(
                              future: gFFI.invokeMethod(
                                  "get_value", "KEY_IS_SUPPORT_VOICE_CALL"),
                              hasData: (isSupportVoiceCall) => IconButton(
                                    color: Colors.white,
                                    icon: isAndroid && isSupportVoiceCall
                                        ? SvgPicture.asset('assets/chat.svg',
                                            colorFilter: ColorFilter.mode(
                                                Colors.white, BlendMode.srcIn))
                                        : Icon(Icons.message),
                                    onPressed: () =>
                                        isAndroid && isSupportVoiceCall
                                            ? showChatOptions(widget.id)
                                            : onPressedTextChat(widget.id),
                                  ))
                        ]) +
                  [
                    IconButton(
                      color: Colors.white,
                      icon: Icon(Icons.more_vert),
                      onPressed: () {
                        setState(() => _showEdit = false);
                        showActions(widget.id);
                      },
                    ),
                  ]),
          Obx(() => IconButton(
                color: Colors.white,
                icon: Icon(Icons.expand_more),
                onPressed: gFFI.ffiModel.waitForFirstImage.isTrue
                    ? null
                    : () {
                        setState(() => _showBar = !_showBar);
                      },
              )),
        ],
      ),
    );
  }

  Widget getBodyForMobile() {
    return Container(
        color: MyTheme.canvasColor,
        child: Stack(children: () {
          final paints = [
            ImagePaint(),
            Positioned(
              top: 10,
              right: 10,
              child: QualityMonitor(gFFI.qualityMonitorModel),
            ),
            SizedBox(
              width: 0,
              height: 0,
              child: !_showEdit
                  ? Container()
                  : TextFormField(
                      textInputAction: TextInputAction.newline,
                      autocorrect: false,
                      // Flutter 3.16.9 Android.
                      // `enableSuggestions` causes secure keyboard to be shown.
                      // https://github.com/flutter/flutter/issues/139143
                      // https://github.com/flutter/flutter/issues/146540
                      // enableSuggestions: false,
                      autofocus: true,
                      focusNode: _mobileFocusNode,
                      maxLines: null,
                      controller: _textController,
                      // trick way to make backspace work always
                      keyboardType: TextInputType.multiline,
                      // `onChanged` may be called depending on the input method if this widget is wrapped in
                      // `Focus(onKeyEvent: ..., child: ...)`
                      // For `Backspace` button in the soft keyboard:
                      // en/fr input method:
                      //      1. The button will not trigger `onKeyEvent` if the text field is not empty.
                      //      2. The button will trigger `onKeyEvent` if the text field is empty.
                      // ko/zh/ja input method: the button will trigger `onKeyEvent`
                      //                     and the event will not popup if `KeyEventResult.handled` is returned.
                      onChanged: null,
                    ).workaroundFreezeLinuxMint(),
            ),
          ];
          return paints;
        }()));
  }

  Widget getBodyForDesktopWithListener() {
    var paints = <Widget>[ImagePaint()];
    return Container(
        color: MyTheme.canvasColor, child: Stack(children: paints));
  }

  List<TTextMenu> _getMobileActionMenus() {
    if (gFFI.ffiModel.pi.platform != kPeerPlatformAndroid ||
        !gFFI.ffiModel.keyboard) {
      return [];
    }
    final enabled = versionCmp(gFFI.ffiModel.pi.version, '1.2.7') >= 0;
    if (!enabled) return [];
    return [
      TTextMenu(
        child: Text(translate('Back')),
        onPressed: () => gFFI.inputModel.onMobileBack(),
      ),
      TTextMenu(
        child: Text(translate('Home')),
        onPressed: () => gFFI.inputModel.onMobileHome(),
      ),
      TTextMenu(
        child: Text(translate('Apps')),
        onPressed: () => gFFI.inputModel.onMobileApps(),
      ),
      TTextMenu(
        child: Text(translate('Volume up')),
        onPressed: () => gFFI.inputModel.onMobileVolumeUp(),
      ),
      TTextMenu(
        child: Text(translate('Volume down')),
        onPressed: () => gFFI.inputModel.onMobileVolumeDown(),
      ),
      TTextMenu(
        child: Text(translate('Power')),
        onPressed: () => gFFI.inputModel.onMobilePower(),
      ),
    ];
  }

  void showActions(String id) async {
    final size = MediaQuery.of(context).size;
    final x = 120.0;
    final y = size.height;
    final mobileActionMenus = _getMobileActionMenus();
    final menus = toolbarControls(context, id, gFFI);

    final List<PopupMenuEntry<int>> more = [
      ...mobileActionMenus
          .asMap()
          .entries
          .map((e) =>
              PopupMenuItem<int>(child: e.value.getChild(), value: e.key))
          .toList(),
      if (mobileActionMenus.isNotEmpty) PopupMenuDivider(),
      ...menus
          .asMap()
          .entries
          .map((e) => PopupMenuItem<int>(
              child: e.value.getChild(),
              value: e.key + mobileActionMenus.length))
          .toList(),
    ];
    () async {
      var index = await showMenu(
        context: context,
        position: RelativeRect.fromLTRB(x, y, x, y),
        items: more,
        elevation: 8,
      );
      if (index != null) {
        if (index < mobileActionMenus.length) {
          mobileActionMenus[index].onPressed?.call();
        } else if (index < mobileActionMenus.length + more.length) {
          menus[index - mobileActionMenus.length].onPressed?.call();
        }
      }
    }();
  }

  onPressedTextChat(String id) {
    gFFI.chatModel.changeCurrentKey(MessageKey(id, ChatModel.clientModeID));
    gFFI.chatModel.toggleChatOverlay();
  }

  showChatOptions(String id) async {
    onPressVoiceCall() => bind.sessionRequestVoiceCall(sessionId: sessionId);
    onPressEndVoiceCall() => bind.sessionCloseVoiceCall(sessionId: sessionId);

    makeTextMenu(String label, Widget icon, VoidCallback onPressed,
            {TextStyle? labelStyle}) =>
        TTextMenu(
          child: Text(translate(label), style: labelStyle),
          trailingIcon: Transform.scale(
            scale: (isDesktop || isWebDesktop) ? 0.8 : 1,
            child: IgnorePointer(
              child: IconButton(
                onPressed: null,
                icon: icon,
              ),
            ),
          ),
          onPressed: onPressed,
        );

    final isInVoice = [
      VoiceCallStatus.waitingForResponse,
      VoiceCallStatus.connected
    ].contains(gFFI.chatModel.voiceCallStatus.value);
    final menus = [
      makeTextMenu('Text chat', Icon(Icons.message, color: MyTheme.accent),
          () => onPressedTextChat(widget.id)),
      isInVoice
          ? makeTextMenu(
              'End voice call',
              SvgPicture.asset(
                'assets/call_wait.svg',
                colorFilter:
                    ColorFilter.mode(Colors.redAccent, BlendMode.srcIn),
              ),
              onPressEndVoiceCall,
              labelStyle: TextStyle(color: Colors.redAccent))
          : makeTextMenu(
              'Voice call',
              SvgPicture.asset(
                'assets/call_wait.svg',
                colorFilter: ColorFilter.mode(MyTheme.accent, BlendMode.srcIn),
              ),
              onPressVoiceCall),
    ];

    final menuItems = menus
        .asMap()
        .entries
        .map((e) => PopupMenuItem<int>(child: e.value.getChild(), value: e.key))
        .toList();
    Future.delayed(Duration.zero, () async {
      final size = MediaQuery.of(context).size;
      final x = 120.0;
      final y = size.height;
      var index = await showMenu(
        context: context,
        position: RelativeRect.fromLTRB(x, y, x, y),
        items: menuItems,
        elevation: 8,
      );
      if (index != null && index < menus.length) {
        menus[index].onPressed?.call();
      }
    });
  }
}

class ImagePaint extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final m = Provider.of<ImageModel>(context);
    final c = Provider.of<CanvasModel>(context);
    var s = c.scale;
    final adjust = c.getAdjustY();
    return CustomPaint(
      painter: ImagePainter(
          image: m.image, x: c.x / s, y: (c.y + adjust) / s, scale: s),
    );
  }
}

void showOptions(
    BuildContext context, String id, OverlayDialogManager dialogManager) async {
  var displays = <Widget>[];
  final pi = gFFI.ffiModel.pi;
  final image = gFFI.ffiModel.getConnectionImageText();
  if (image != null) {
    displays.add(Padding(padding: const EdgeInsets.only(top: 8), child: image));
  }
  if (pi.displays.length > 1 && pi.currentDisplay != kAllDisplayValue) {
    final cur = pi.currentDisplay;
    final children = <Widget>[];
    final isDarkTheme = MyTheme.currentThemeMode() == ThemeMode.dark;
    final numColorSelected = Colors.white;
    final numColorUnselected = isDarkTheme ? Colors.grey : Colors.black87;
    // We can't use `Theme.of(context).primaryColor` here, the color is:
    // - light theme: 0xff2196f3 (Colors.blue)
    // - dark theme: 0xff212121 (the canvas color?)
    final numBgSelected =
        Theme.of(context).colorScheme.primary.withOpacity(0.6);
    for (var i = 0; i < pi.displays.length; ++i) {
      children.add(InkWell(
          onTap: () {
            if (i == cur) return;
            openMonitorInTheSameTab(i, gFFI, pi);
            gFFI.dialogManager.dismissAll();
          },
          child: Ink(
              width: 40,
              height: 40,
              decoration: BoxDecoration(
                  border: Border.all(color: Theme.of(context).hintColor),
                  borderRadius: BorderRadius.circular(2),
                  color: i == cur ? numBgSelected : null),
              child: Center(
                  child: Text((i + 1).toString(),
                      style: TextStyle(
                          color:
                              i == cur ? numColorSelected : numColorUnselected,
                          fontWeight: FontWeight.bold))))));
    }
    displays.add(Padding(
        padding: const EdgeInsets.only(top: 8),
        child: Wrap(
          alignment: WrapAlignment.center,
          spacing: 8,
          children: children,
        )));
  }
  if (displays.isNotEmpty) {
    displays.add(const Divider(color: MyTheme.border));
  }

  List<TRadioMenu<String>> viewStyleRadios =
      await toolbarViewStyle(context, id, gFFI);
  List<TRadioMenu<String>> imageQualityRadios =
      await toolbarImageQuality(context, id, gFFI);
  List<TRadioMenu<String>> codecRadios = await toolbarCodec(context, id, gFFI);
  List<TToggleMenu> displayToggles =
      await toolbarDisplayToggle(context, id, gFFI);

  dialogManager.show((setState, close, context) {
    var viewStyle =
        (viewStyleRadios.isNotEmpty ? viewStyleRadios[0].groupValue : '').obs;
    var imageQuality =
        (imageQualityRadios.isNotEmpty ? imageQualityRadios[0].groupValue : '')
            .obs;
    var codec = (codecRadios.isNotEmpty ? codecRadios[0].groupValue : '').obs;
    final radios = [
      for (var e in viewStyleRadios)
        Obx(() => getRadio<String>(
            e.child,
            e.value,
            viewStyle.value,
            e.onChanged != null
                ? (v) {
                    e.onChanged?.call(v);
                    if (v != null) viewStyle.value = v;
                  }
                : null)),
      const Divider(color: MyTheme.border),
      for (var e in imageQualityRadios)
        Obx(() => getRadio<String>(
            e.child,
            e.value,
            imageQuality.value,
            e.onChanged != null
                ? (v) {
                    e.onChanged?.call(v);
                    if (v != null) imageQuality.value = v;
                  }
                : null)),
      const Divider(color: MyTheme.border),
      for (var e in codecRadios)
        Obx(() => getRadio<String>(
            e.child,
            e.value,
            codec.value,
            e.onChanged != null
                ? (v) {
                    e.onChanged?.call(v);
                    if (v != null) codec.value = v;
                  }
                : null)),
      if (codecRadios.isNotEmpty) const Divider(color: MyTheme.border),
    ];

    final rxToggleValues = displayToggles.map((e) => e.value.obs).toList();
    final displayTogglesList = displayToggles
        .asMap()
        .entries
        .map((e) => Obx(() => CheckboxListTile(
            contentPadding: EdgeInsets.zero,
            visualDensity: VisualDensity.compact,
            value: rxToggleValues[e.key].value,
            onChanged: e.value.onChanged != null
                ? (v) {
                    e.value.onChanged?.call(v);
                    if (v != null) rxToggleValues[e.key].value = v;
                  }
                : null,
            title: e.value.child)))
        .toList();
    final toggles = [
      ...displayTogglesList,
    ];

    var popupDialogMenus = List<Widget>.empty(growable: true);
    if (popupDialogMenus.isNotEmpty) {
      popupDialogMenus.add(const Divider(color: MyTheme.border));
    }

    return CustomAlertDialog(
      content: Column(
          mainAxisSize: MainAxisSize.min,
          children: displays + radios + popupDialogMenus + toggles),
    );
  }, clickMaskDismiss: true, backDismiss: true).then((value) {
    _disableAndroidSoftKeyboard();
  });
}

class FABLocation extends FloatingActionButtonLocation {
  FloatingActionButtonLocation location;
  double offsetX;
  double offsetY;
  FABLocation(this.location, this.offsetX, this.offsetY);

  @override
  Offset getOffset(ScaffoldPrelayoutGeometry scaffoldGeometry) {
    final offset = location.getOffset(scaffoldGeometry);
    return Offset(offset.dx + offsetX, offset.dy + offsetY);
  }
}