Alright, as promised, here I am with a very simple GLSL shader example. So the first thing to mention is that shaders in ENIGMA, since they were first added, are very pure. This means we have less abstraction on top of them so you'll need to do things like declare the GLSL version at the top. I have plans and intentions of improving shader support and compatibility quite a bit soon. Since we've largely revamped our graphics systems and solved some of the more basic problems... this is the next logical step as I've been incrementally adding DX11 support.
You'll find 3 files attached to this post. simple-shader-example.zip is a GMX that contains a GLSL 110 shader which works in our OpenGL1 graphics system. Shaders will not be saved when saving your project in the GMK format because it did not support them. The shader itself, while GLSL 110 compliant, is not GMS compatible. It will therefore not work in our OpenGL3 system, which is structured more like GMS's shaders. This is one of the areas I plan on improving going into the future. You will also find toonv.glsl and toonf.glsl which is a 3D toon shader that also works in our OpenGL1 graphics system if you would like to use it.
If you have any more questions, please feel free to ask, and I will make sure that when I get to improving the shader support that I make an announcement.