flame/lib/util.dart

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

import 'package:flutter/gestures.dart';
import 'package:flutter/services.dart';

import 'position.dart';

/// Some utilities that did not fit anywhere else.
///
/// To use this class, access it via [Flame.util].
class Util {
  /// Sets the app to be fullscreen (no buttons bar os notifications on top).
  ///
  /// Most games should probably be this way.
  Future<void> fullScreen() {
    return SystemChrome.setEnabledSystemUIOverlays([]);
  }

  /// Sets the preferred orietation (landscape or protrait for the app).
  ///
  /// When it opens, it will automatically change orientation to the preferred one (if possible).
  Future<void> setOrientation(DeviceOrientation orientation) {
    return SystemChrome.setPreferredOrientations([orientation]);
  }

  /// Waits for the initial screen dimensions to be avaliable.
  ///
  /// Because of flutter's issue #5259, when the app starts the size might be 0x0.
  /// This waits for the information to be properly updated.
  ///
  /// A best practice would be to implement there resize hooks on your game and components and don't use this at all.
  /// Make sure your components are able to render and update themselves for any possible screen size.
  Future<Size> initialDimensions() async {
    // https://github.com/flutter/flutter/issues/5259
    // "In release mode we start off at 0x0 but we don't in debug mode"
    return await new Future<Size>(() {
      if (window.physicalSize.isEmpty) {
        final completer = new Completer<Size>();
        window.onMetricsChanged = () {
          if (!window.physicalSize.isEmpty) {
            completer.complete(window.physicalSize / window.devicePixelRatio);
          }
        };
        return completer.future;
      }
      return window.physicalSize / window.devicePixelRatio;
    });
  }

  /// This properly binds a gesture recognizer to your game.
  ///
  /// Use this in order to get it to work in case your app also contains other widgets.
  void addGestureRecognizer(GestureRecognizer recognizer) {
    GestureBinding.instance.pointerRouter.addGlobalRoute((PointerEvent e) {
      if (e is PointerDownEvent) {
        recognizer.addPointer(e);
      }
    });
  }

  /// Utility method to render stuff on a specific place.
  ///
  /// Some render methods don't allow to pass a offset.
  /// This method translate the canvas, draw what you want, and then translate back.
  void drawWhere(Canvas c, Position p, void Function(Canvas) fn) {
    c.translate(p.x, p.y);
    fn(c);
    c.translate(-p.x, -p.y);
  }
}