Interesting question, especially if you try to port some Shadertoy demos that can read the keyboard from the pixel shader.
If you need to draw few lines with GeeXLab, this article should help you.
Since GeeXLab version 0.9+, a Direct3D 12 renderer plugin is available in the Windows versions (32 and 64-bit).
If you need to retrieve date and time in Lua, here is small demo that displays the current date as well as elapsed time in seconds.
On the Raspberry Pi there is a very nice feature that allows to create very cool shaped windows: the control of the opacity of the 3D window.
In recent versions of GeeXLab, I added the support of reflections (mirror, surface water for example). Here is how to do a reflection with GeeXLab:
It may be useful to know if the current OpenGL implementation supports a particular OpenGL extension. For example you have coded a cool OpenGL 4.0 demo based on tessellation shaders. It would be nice to display a different scene (actually an error scene) if the demo runs on a system that is limited to OpenGL 3.0.