Xonotic shader manual and tools?

I did level design for Quake III Arena up until 2003 and have not been mapping ever since. But a week or two ago I played Xonotic for the first time and I was impressed by the gameplay and the maps.. really awesome!

I'm getting oriented in mapping for Xonotic and ofcourse have lots of questions.

I read that Xonotic uses the Darkplaces engine that is based on the quake1 engine id tech 2?!
But shaders were introduced in Quake III Arena no? So is that same Q3A shader facility added to the Darkplaces/Xonotic Engine?

I still have this shader manual for Q3A revision #12 from end of 1999 on my stack and I was wondering does this apply to DP/Xonotic?

If the shader facility has changed or is is different, where can I find the right shader manual for Xonotic?

I also have this tool on my stack Q3ASE 1.5.3 (Quake 3 Arena Shader Editor). Can I still use it or can you point me to better tools?

Maybe this?
http://www.quakewiki.net/darkplaces-wiki...on-for-dp/

When I was working on maps, I used this manual as a guide:
http://q3map2.robotrenegade.com/docs/shader_manual/

Though as far as I know, you can only have one layer per shader (bar lightmaps) in Xonotic/Darkplaces.

Thanks poVoq, for a good start point.
After some Googling I found this almost same document at Xonotic wiki at gitlab.com,
though with a little additional information.
https://gitlab.com/xonotic/xonotic/wikis.../Materials

Thanks sev, that looks great and really complete.
I read that one layer per shader also somewhere, but still need to figure out what that means.

it means you cannot have multiple shader stages (eg blend multiple textures) in on shader. The exception being alpha blend (typically terrain, have a look at xonotic-maps.pk3dir/scripts/terrain01x.shader for example/s) shaders.

Thanks, tZork, that helps a bit ;-). I can only address that when really getting through to the depths of what shaders does, what's the scope of it, what can be achieved with "one shader stage", and why the "only one" limit? is there.

Long story short, the one stage limit is a engine thing, and you can get away with most things using one stage, you just have to use multiple mesh layers instead (for complicated visual effects