Flutter Web fullscreen feature helper, using 'universal_html' package.

fullscreen_helper.dart

import 'package:universal_html/js.dart' as js;
import 'package:universal_html/html.dart' as html;

void example() {
     _enterFullscreen(html.document.documentElement);
     _exitFullscreen(html.document);
}

/// Flutter Web: Enter Fullscreen on Firefox, Chrome, Opera, Safari, etc.
/// Based on https://stackoverflow.com/questions/29714889/how-to-request-fullscreen-in-compiled-dart
/// and https://github.com/dart-lang/sdk/issues/4136
void _enterFullscreen(Object? element) {
  if (element == null) return;

  var elem = js.JsObject.fromBrowserObject(element);

  if (elem.hasProperty("requestFullscreen")) {
    elem.callMethod("requestFullscreen");
  } else {
    List<String> vendors = ['moz', 'webkit', 'ms', 'o'];
    for (String vendor in vendors) {
      String vendorFullscreen = "${vendor}RequestFullscreen";
      if (vendor == 'moz') {
        vendorFullscreen = "${vendor}RequestFullScreen";
      }
      if (elem.hasProperty(vendorFullscreen)) {
        elem.callMethod(vendorFullscreen);
        return;
      }
    }
  }
}

/// Flutter Web: Exit Fullscreen on Firefox, Chrome, Opera, Safari, etc.
/// Based on https://stackoverflow.com/questions/29714889/how-to-request-fullscreen-in-compiled-dart
/// and https://github.com/dart-lang/sdk/issues/4136
void _exitFullscreen(Object? element) {
  if (element == null) return;

  var elem = js.JsObject.fromBrowserObject(element);

  if (elem.hasProperty("exitFullscreen")) {
    elem.callMethod("exitFullscreen");
  } else {
    List<String> vendors = ['moz', 'webkit', 'ms', 'o'];
    for (String vendor in vendors) {
      String vendorFullscreen = "${vendor}ExitFullscreen";
      if (vendor == 'moz') {
        vendorFullscreen = "${vendor}CancelFullScreen";
      }
      if (elem.hasProperty(vendorFullscreen)) {
        elem.callMethod(vendorFullscreen);
        return;
      }
    }
  }
}