fix: macos, main window, dark theme, border (#10749)

Signed-off-by: fufesou <linlong1266@gmail.com>

flutter/lib/main.dart

@@ -133,7 +133,8 @@ void runMainApp(bool startService) async {
   runApp(App());
 
   // Set window option.
-  WindowOptions windowOptions = getHiddenTitleBarWindowOptions();
+  WindowOptions windowOptions =
+      getHiddenTitleBarWindowOptions(isMainWindow: true);
   windowManager.waitUntilReadyToShow(windowOptions, () async {
     // Restore the location of the main window before window hide or show.
     await restoreWindowPosition(WindowType.Main);
@@ -354,7 +355,10 @@ void runInstallPage() async {
 }
 
 WindowOptions getHiddenTitleBarWindowOptions(
-    {Size? size, bool center = false, bool? alwaysOnTop}) {
+    {bool isMainWindow = false,
+    Size? size,
+    bool center = false,
+    bool? alwaysOnTop}) {
   var defaultTitleBarStyle = TitleBarStyle.hidden;
   // we do not hide titlebar on win7 because of the frame overflow.
   if (kUseCompatibleUiMode) {
@@ -363,7 +367,7 @@ WindowOptions getHiddenTitleBarWindowOptions(
   return WindowOptions(
     size: size,
     center: center,
-    backgroundColor: Colors.transparent,
+    backgroundColor: (isMacOS && isMainWindow) ? null : Colors.transparent,
     skipTaskbar: false,
     titleBarStyle: defaultTitleBarStyle,
     alwaysOnTop: alwaysOnTop,