add centering and focus capabilities

lib/utils/measure_size.dart

@@ -0,0 +1,28 @@
+import 'package:flutter/material.dart';
+
+/// Utility to synchronously measure the size of a widget by building it offscreen in an Overlay.
+/// Only works for widgets with deterministic, constraint-based sizing (no async/layout dependencies).
+Size measureWidgetSize(BuildContext context, WidgetBuilder builder, {BoxConstraints? constraints}) {
+  final key = GlobalKey();
+  final overlay = Overlay.of(context);
+  Size? measuredSize;
+
+  final widget = Offstage(
+    child: ConstrainedBox(
+      constraints: constraints ?? const BoxConstraints(),
+      child: Container(key: key, child: builder(context)),
+    ),
+  );
+
+  final entry = OverlayEntry(builder: (_) => widget);
+  overlay.insert(entry);
+
+  WidgetsBinding.instance.handleDrawFrame();
+
+  final ctx = key.currentContext;
+  if (ctx != null) {
+    measuredSize = (ctx.findRenderObject() as RenderBox).size;
+  }
+  entry.remove();
+  return measuredSize ?? Size.zero;
+}