Initial commit: imajViewer Flutter Linux image viewer

lib/services/window_persistence.dart

@@ -0,0 +1,49 @@
+import 'dart:convert';
+import 'dart:io';
+import 'package:flutter/material.dart';
+
+/// Persists and restores window position and size.
+class WindowPersistence {
+  static File get _configFile {
+    final home = Platform.environment['HOME'] ?? '/tmp';
+    return File('$home/.config/imajviewer/window.json');
+  }
+
+  /// Save window rect synchronously (safe to call before destroy).
+  static void saveSync({
+    required Offset position,
+    required Size size,
+  }) {
+    final file = _configFile;
+    file.parent.createSync(recursive: true);
+    file.writeAsStringSync(jsonEncode({
+      'x': position.dx.toInt(),
+      'y': position.dy.toInt(),
+      'width': size.width.toInt(),
+      'height': size.height.toInt(),
+    }));
+  }
+
+  /// Restore saved window rect. Returns null if no saved config.
+  static ({Offset position, Size size})? restore() {
+    final file = _configFile;
+    if (!file.existsSync()) return null;
+
+    try {
+      final data = jsonDecode(file.readAsStringSync()) as Map<String, dynamic>;
+      final x = (data['x'] as num?)?.toDouble() ?? 0;
+      final y = (data['y'] as num?)?.toDouble() ?? 0;
+      final w = (data['width'] as num?)?.toDouble() ?? 1280;
+      final h = (data['height'] as num?)?.toDouble() ?? 800;
+
+      if (w < 200 || h < 200 || x < -1000 || y < -1000) return null;
+
+      return (
+        position: Offset(x, y),
+        size: Size(w, h),
+      );
+    } catch (_) {
+      return null;
+    }
+  }
+}