Hide Ogre and Ogre2 external window on MacOS and Windows (#1141)

Hides Ogre and Ogre2 external window on MacOS and Windows.

Unlike Linux, Ogre backend must use external window handles. 

Signed-off-by: Vasily Kiniv <[email protected]>

Author: v-kiniv

ogre/src/OgreRenderEngine.cc

@@ -687,6 +687,7 @@ std::string OgreRenderEngine::CreateRenderWindow(const std::string &_handle,
     // Mac and Windows *must* use externalWindow handle.
 #if defined(__APPLE__) || defined(_MSC_VER)
     params["externalWindowHandle"] = _handle;
+    params["hidden"] = "true";
 #else
     params["parentWindowHandle"] = _handle;
 #endif

ogre2/src/Ogre2RenderEngine.cc

@@ -1196,6 +1196,7 @@ std::string Ogre2RenderEngine::CreateRenderWindow(const std::string &_handle,
       // Mac and Windows *must* use externalWindow handle.
 #if defined(__APPLE__) || defined(_MSC_VER)
       params["externalWindowHandle"] = _handle;
+      params["hidden"] = "true";
 #else
       params["parentWindowHandle"] = _handle;
 #endif