windows: emit minimize/restore events to keep custom platform view synced

flutter_inappwebview_windows/lib/src/in_app_webview/custom_platform_view.dart

@@ -356,6 +356,18 @@ class _CustomPlatformViewState extends State<CustomPlatformView>
     _reportWidgetPosition();
   }
 
+  @override
+  void onWindowMinimize() {
+    _reportSurfaceSize();
+    _reportWidgetPosition();
+  }
+
+  @override
+  void onWindowRestore() {
+    _reportSurfaceSize();
+    _reportWidgetPosition();
+  }
+
   @override
   Widget build(BuildContext context) {
     return Focus(

flutter_inappwebview_windows/lib/src/platform_util.dart

@@ -5,6 +5,8 @@ abstract mixin class PlatformUtilListener {
   void onWindowMove() {}
   void onWindowStartMove() {}
   void onWindowEndMove() {}
+  void onWindowMinimize() {}
+  void onWindowRestore() {}
 }
 
 ///Platform native utilities
@@ -51,6 +53,12 @@ class PlatformUtil {
           case 'onWindowEndMove':
             listener.onWindowEndMove();
             break;
+          case 'onWindowMinimize':
+            listener.onWindowMinimize();
+            break;
+          case 'onWindowRestore':
+            listener.onWindowRestore();
+            break;
         }
       }
     }

flutter_inappwebview_windows/windows/platform_util.cpp

@@ -57,6 +57,22 @@ namespace flutter_inappwebview_plugin
         _EmitEvent("onWindowEndMove");
       }
     }
+    else if (message == WM_SIZE) {
+      if (wParam == SIZE_MINIMIZED) {
+        if (!window_is_minimized_) {
+          window_is_minimized_ = true;
+          _EmitEvent("onWindowMinimize");
+        }
+        _EmitEvent("onWindowMove");
+      }
+      else if (wParam == SIZE_RESTORED || wParam == SIZE_MAXIMIZED) {
+        if (window_is_minimized_) {
+          window_is_minimized_ = false;
+          _EmitEvent("onWindowRestore");
+        }
+        _EmitEvent("onWindowMove");
+      }
+    }
 
     return result;
   }

flutter_inappwebview_windows/windows/platform_util.h

@@ -35,6 +35,7 @@ namespace flutter_inappwebview_plugin
     void PlatformUtil::_EmitEvent(std::string eventName);
     bool window_is_moving_ = false;
     bool window_start_move_sent_ = false;
+    bool window_is_minimized_ = false;
   };
 }