Hide dummy OGRE render window on macOS

[inbarajaldrin]

🦟 Bug fix

Summary

On macOS, Ogre2RenderEngine::CreateRenderWindow() creates a 1x1 dummy window for GPU resource initialization (HLMS, compositor setup). This window appears as a visible blank "OgreWindow(0)_0" window alongside the actual Gazebo GUI. Users can close it without affecting rendering, but it shouldn't be visible in the first place.

Before: Blank "OgreWindow(0)_0" window appears on every Gazebo launch on macOS

After: Dummy window is created hidden and stays hidden

How to reproduce (before fix):

1. Install Gazebo Harmonic on macOS (Apple Silicon) via conda-forge/RoboStack
2. Run gz sim -s -r shapes.sdf & then gz sim -g
3. Observe blank "OgreWindow(0)_0" window alongside the Gazebo Sim GUI
4. Close the blank window — Gazebo continues rendering normally, confirming the window is unused

Root cause:

Two issues in ogre2/src/Ogre2RenderEngine.cc:

1. Line ~1224: The comment says "Hide window if dimensions are less than or equal to one" but only sets params["border"] = "none" — it never passes params["hidden"] = "true" to OGRE-Next. Both the Metal (OgreMetalWindow) and GL3Plus (OgreOSXCocoaWindow) backends already support this parameter.

2. Line ~1303: After window creation, this->window->_setVisible(true) unconditionally shows the window, which would override the hidden flag even if it were set.

Changes:

• Pass params["hidden"] = "true" when creating the dummy render window
• Guard _setVisible(true) to only apply to real render windows (_width > 1 && _height > 1), preventing the dummy window from being re-shown after creation

Testing:

• Gazebo Harmonic 8.10.0 on macOS 26 (Tahoe), Apple M4
• RoboStack/conda-forge packages via pixi
• Verified: Gazebo GUI renders 3D scene correctly, dummy window no longer appears
• Verified: Closing the dummy window (when visible) does not affect Gazebo — confirming it is unused after initialization

Related: Similar issue reported for RViz on Windows: ms-iot/ROSOnWindows#336 (same OGRE dummy window pattern)

Checklist

• Signed all commits for DCO
• Added a screen capture or video to the PR description that demonstrates the fix (as needed)
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
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• All tests passed (See test coverage)
• Updated Bazel files (if adding new files). Created an issue otherwise.
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Generated-by: Claude (Anthropic)

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[azeey]

Hi @inbarajaldrin thanks for the contribution! Could you please fill out the pull request template? It's the content already placed in the PR description when you create a new PR.

[inbarajaldrin]

Hi @azeey, I've updated the PR description with the template.