refactor: Better future loading dialog without flickering

lib/widgets/chat_settings_popup_menu.dart

@@ -5,11 +5,11 @@ import 'package:flutter/services.dart';
 
 import 'package:adaptive_dialog/adaptive_dialog.dart';
 import 'package:flutter_gen/gen_l10n/l10n.dart';
-import 'package:future_loading_dialog/future_loading_dialog.dart';
 import 'package:go_router/go_router.dart';
 import 'package:keyboard_shortcuts/keyboard_shortcuts.dart';
 import 'package:matrix/matrix.dart';
 
+import 'package:fluffychat/widgets/future_loading_dialog.dart';
 import 'matrix.dart';
 
 enum ChatPopupMenuActions { details, mute, unmute, leave, search }

lib/widgets/future_loading_dialog.dart

@@ -0,0 +1,141 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+
+import 'package:async/async.dart';
+import 'package:flutter_gen/gen_l10n/l10n.dart';
+
+import 'package:fluffychat/utils/localized_exception_extension.dart';
+
+/// Displays a loading dialog which reacts to the given [future]. The dialog
+/// will be dismissed and the value will be returned when the future completes.
+/// If an error occured, then [onError] will be called and this method returns
+/// null.
+Future<Result<T>> showFutureLoadingDialog<T>({
+  required BuildContext context,
+  required Future<T> Function() future,
+  String? title,
+  String? backLabel,
+  String Function(dynamic exception)? onError,
+  bool barrierDismissible = false,
+}) async {
+  final futureExec = future();
+  final resultFuture = ResultFuture(futureExec);
+
+  var i = 3;
+  do {
+    final result = resultFuture.result;
+    if (result != null) {
+      if (result.isError) break;
+      return result;
+    }
+    await Future.delayed(const Duration(milliseconds: 100));
+    i--;
+  } while (i > 0);
+
+  final result = await showAdaptiveDialog<Result<T>>(
+    context: context,
+    barrierDismissible: barrierDismissible,
+    builder: (BuildContext context) => LoadingDialog<T>(
+      future: futureExec,
+      title: title,
+      backLabel: backLabel,
+      onError: onError,
+    ),
+  );
+  return result ??
+      Result.error(
+        Exception('FutureDialog canceled'),
+        StackTrace.current,
+      );
+}
+
+class LoadingDialog<T> extends StatefulWidget {
+  final String? title;
+  final String? backLabel;
+  final Future<T> future;
+  final String Function(dynamic exception)? onError;
+
+  const LoadingDialog({
+    super.key,
+    required this.future,
+    this.title,
+    this.onError,
+    this.backLabel,
+  });
+  @override
+  LoadingDialogState<T> createState() => LoadingDialogState<T>();
+}
+
+class LoadingDialogState<T> extends State<LoadingDialog> {
+  Object? exception;
+  StackTrace? stackTrace;
+
+  @override
+  void initState() {
+    super.initState();
+    widget.future.then(
+      (result) => Navigator.of(context).pop<Result<T>>(Result.value(result)),
+      onError: (e, s) => setState(() {
+        exception = e;
+        stackTrace = s;
+      }),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final exception = this.exception;
+    final titleLabel = exception != null
+        ? widget.onError?.call(exception) ??
+            exception.toLocalizedString(context)
+        : widget.title ?? L10n.of(context).loadingPleaseWait;
+
+    return AlertDialog.adaptive(
+      content: ConstrainedBox(
+        constraints: const BoxConstraints(maxWidth: 256),
+        child: Row(
+          crossAxisAlignment: CrossAxisAlignment.center,
+          children: [
+            if (exception == null)
+              const CircularProgressIndicator.adaptive()
+            else
+              Icon(
+                Icons.error_outline_outlined,
+                color: Theme.of(context).colorScheme.error,
+                size: 48,
+              ),
+            const SizedBox(width: 20),
+            Expanded(
+              child: Text(
+                titleLabel,
+                maxLines: 2,
+                textAlign: TextAlign.left,
+                overflow: TextOverflow.ellipsis,
+              ),
+            ),
+          ],
+        ),
+      ),
+      actions: exception == null
+          ? null
+          : [
+              TextButton(
+                onPressed: () => Navigator.of(context).pop<Result<T>>(
+                  Result.error(
+                    exception,
+                    stackTrace,
+                  ),
+                ),
+                child: Text(widget.backLabel ?? L10n.of(context).close),
+              ),
+            ],
+    );
+  }
+}
+
+extension DeprecatedApiAccessExtension<T> on Result<T> {
+  T? get result => asValue?.value;
+
+  Object? get error => asError?.error;
+}

lib/widgets/matrix.dart

@@ -8,7 +8,6 @@ import 'package:adaptive_dialog/adaptive_dialog.dart';
 import 'package:collection/collection.dart';
 import 'package:desktop_notifications/desktop_notifications.dart';
 import 'package:flutter_gen/gen_l10n/l10n.dart';
-import 'package:future_loading_dialog/future_loading_dialog.dart';
 import 'package:http/http.dart' as http;
 import 'package:image_picker/image_picker.dart';
 import 'package:intl/intl.dart';
@@ -21,12 +20,12 @@ import 'package:url_launcher/url_launcher_string.dart';
 
 import 'package:fluffychat/utils/client_manager.dart';
 import 'package:fluffychat/utils/init_with_restore.dart';
-import 'package:fluffychat/utils/localized_exception_extension.dart';
 import 'package:fluffychat/utils/matrix_sdk_extensions/matrix_file_extension.dart';
 import 'package:fluffychat/utils/platform_infos.dart';
 import 'package:fluffychat/utils/uia_request_manager.dart';
 import 'package:fluffychat/utils/voip_plugin.dart';
 import 'package:fluffychat/widgets/fluffy_chat_app.dart';
+import 'package:fluffychat/widgets/future_loading_dialog.dart';
 import '../config/app_config.dart';
 import '../config/setting_keys.dart';
 import '../pages/key_verification/key_verification_dialog.dart';
@@ -234,16 +233,6 @@ class MatrixState extends State<Matrix> with WidgetsBindingObserver {
     } else {
       initSettings();
     }
-    initLoadingDialog();
-  }
-
-  void initLoadingDialog() {
-    WidgetsBinding.instance.addPostFrameCallback((_) {
-      LoadingDialog.defaultTitle = L10n.of(context).loadingPleaseWait;
-      LoadingDialog.defaultBackLabel = L10n.of(context).close;
-      LoadingDialog.defaultOnError =
-          (e) => (e as Object?)!.toLocalizedString(context);
-    });
   }
 
   Future<void> initConfig() async {

lib/widgets/public_room_bottom_sheet.dart

@@ -2,13 +2,13 @@ import 'package:flutter/material.dart';
 
 import 'package:flutter_gen/gen_l10n/l10n.dart';
 import 'package:flutter_linkify/flutter_linkify.dart';
-import 'package:future_loading_dialog/future_loading_dialog.dart';
 import 'package:go_router/go_router.dart';
 import 'package:matrix/matrix.dart';
 
 import 'package:fluffychat/utils/fluffy_share.dart';
 import 'package:fluffychat/utils/url_launcher.dart';
 import 'package:fluffychat/widgets/avatar.dart';
+import 'package:fluffychat/widgets/future_loading_dialog.dart';
 import 'package:fluffychat/widgets/matrix.dart';
 
 class PublicRoomBottomSheet extends StatelessWidget {