fix: Correctly reflect matrix size change

lib/providers/desktop_view_provider.dart

@@ -320,7 +320,9 @@ class DesktopViewProvider extends UnityProvider {
   /// Updates a device in all the layouts.
   ///
   /// If [reload] is `true`, the device player will be reloaded.
-  Future<void> updateDevice(
+  ///
+  /// Return the new device.
+  Device updateDevice(
     Device previousDevice,
     Device device, {
     bool reload = false,
@@ -343,6 +345,8 @@ class DesktopViewProvider extends UnityProvider {
     }
 
     notifyListeners();
-    return save(notifyListeners: false);
+    save(notifyListeners: false);
+
+    return device;
   }
 }

lib/screens/layouts/desktop/multicast_view.dart

@@ -41,8 +41,7 @@ class MulticastViewport extends StatefulWidget {
 }
 
 class _MulticastViewportState extends State<MulticastViewport> {
-  var _placeholderDevice = Device.dump();
-  Device get device => widget.device ?? _placeholderDevice;
+  late Device device = widget.device ?? Device.dump();
 
   Timer? _gap;
 
@@ -163,17 +162,17 @@ class _MulticastViewportState extends State<MulticastViewport> {
                     return HoverButton(
                       onDoubleTap: () {
                         if (widget.device != null) {
-                          views.updateDevice(
+                          device = views.updateDevice(
                             device,
                             device.copyWith(matrixType: matrixType.next),
                           );
+                          setState(() {});
                         } else {
                           setState(() {
-                            _placeholderDevice = _placeholderDevice.copyWith(
+                            device = device.copyWith(
                               matrixType: matrixType.next,
                             );
-                            view.player.zoom.matrixType =
-                                _placeholderDevice.matrixType!;
+                            view.player.zoom.matrixType = device.matrixType!;
                           });
                         }
                       },