Hide dummy OGRE render window on macOS

The initialization render window created by Ogre2RenderEngine for GPU
resource setup (HLMS, compositor) was visible on macOS as a blank
'OgreWindow(0)_0' window. This window serves no purpose after
initialization and can be safely closed by the user without affecting
rendering.

Two changes:
1. Pass params["hidden"] = "true" when creating the dummy window.
   Both Metal (OgreMetalWindow) and GL3Plus (OgreOSXCocoaWindow)
   backends already support this parameter.
2. Guard _setVisible(true) to only apply to real render windows
   (width/height > 1), preventing the dummy window from being
   re-shown after creation.

Tested on macOS 26 (Tahoe) with Apple M4, Gazebo Harmonic 8.10.0
via conda-forge/RoboStack packages.

Signed-off-by: Aldrin Inbaraj <aldrininbaraj@gmail.com>

Generated-by: Claude (Anthropic)

Author: inbarajaldrin

ogre2/src/Ogre2RenderEngine.cc

@@ -1222,6 +1222,7 @@ std::string Ogre2RenderEngine::CreateRenderWindow(const std::string &_handle,
 
   // Hide window if dimensions are less than or equal to one.
   params["border"] = "none";
+  params["hidden"] = "true";
 
   std::ostringstream stream;
   stream << "OgreWindow(0)" << "_" << _handle;
@@ -1299,10 +1300,15 @@ std::string Ogre2RenderEngine::CreateRenderWindow(const std::string &_handle,
 
   if (this->window)
   {
-    this->window->_setVisible(true);
+    // Only show and reposition the window if it was not created as a
+    // hidden dummy window (e.g. for render-to-texture initialization).
+    if (_width > 1u && _height > 1u)
+    {
+      this->window->_setVisible(true);
 
-    // Windows needs to reposition the render window to 0,0.
-    this->window->reposition(0, 0);
+      // Windows needs to reposition the render window to 0,0.
+      this->window->reposition(0, 0);
+    }
   }
   return stream.str();
 }