Reintroduced topmost LayoutBuilder to get widget size instead of screen size

@@ -248,8 +248,8 @@ class _MobileScannerState extends State<MobileScanner>
 
   @override
   Widget build(BuildContext context) {
-    final Size size = MediaQuery.of(context).size;
-
+    return LayoutBuilder(
+      builder: (context, constraints) {
         return ValueListenableBuilder<MobileScannerArguments?>(
           valueListenable: _controller.startArguments,
           builder: (context, value, child) {
@@ -262,7 +262,7 @@ class _MobileScannerState extends State<MobileScanner>
                 widget.fit,
                 widget.scanWindow!,
                 value.size,
-            size,
+                constraints.biggest,
               );
 
               _controller.updateScanWindow(scanWindow);
@@ -280,6 +280,8 @@ class _MobileScannerState extends State<MobileScanner>
             }
           },
         );
+      },
+    );
   }
 
   Widget _scanner(Size size, String? webId, int? textureId) {