By using the OpenGL wrapper (bgl) I get managed to add a geometry shader to the custom material shader.
I hopefully fixed the Intel bug. I have tested it with an Intel HD Graphics 4000. But sometime it will crash. I seems that Intel attach the shades randomly.
It is very important for Intel and ATI/AMD that are the latests drivers are installed. Legacy drivers will not work (no geometry extension).
I also added some new basic examples.
GeometryShaderExample V1.2.blend (112 KB)
Small improvement. Using GL_CURRENT_PROGRAM to get shader program, which should be faster to get the actual shader program.
Added a new example.
GeometryShaderExample_V1.3.blend (116 KB)
Add four new examples (tessellation, wireframe).