Refine new editor shell host and embedded icons

new_editor/app/Host/WindowMessageDispatcher.cpp

@@ -4,6 +4,13 @@
 
 namespace XCEngine::UI::Editor::Host {
 
+namespace {
+
+constexpr UINT kMessageNcUaDrawCaption = 0x00AEu;
+constexpr UINT kMessageNcUaDrawFrame = 0x00AFu;
+
+} // namespace
+
 void TryEnableNonClientDpiScaling(HWND hwnd) {
     if (hwnd == nullptr) {
         return;
@@ -82,6 +89,20 @@ bool WindowMessageDispatcher::TryDispatch(
             return true;
         }
         return false;
+    case WM_NCHITTEST:
+        if (application.IsBorderlessWindowEnabled()) {
+            outResult = HTCLIENT;
+            return true;
+        }
+        return false;
+    case WM_NCPAINT:
+    case kMessageNcUaDrawCaption:
+    case kMessageNcUaDrawFrame:
+        if (application.IsBorderlessWindowEnabled()) {
+            outResult = 0;
+            return true;
+        }
+        return false;
     case WM_SYSCOMMAND:
         if (application.HandleBorderlessWindowSystemCommand(wParam)) {
             outResult = 0;