Hello i have curiosity about how to make a decorator, control look and general theme things with haiku os, can suggest me something to read? this things are compatible with the old zeta beos theme standard? it can change the icons too? i know there are son skills for the apearence but is not so clear to me what or how we can do it.
They are actually programs:
AFAIK Zeta themes are incompatible.
Ask s40in Profile - s40in - Haiku Community
He create some of it.
Would be of interest how to do own decorators as part of our knowledge base besly. I one have a description for us, contact me or lorglas.
There are no guides about this. There are only source codes in Haiku.
There are source codes for my decors and controls in my github. But this is not a good example to follow 
Can you make a little step by step list, how to change a source to create a decorator and send it to me. if i get it running, i will write an tutorial
As miqlas said, they are C++ code and not much different from writing a custom BView subclass. There are functions to implement (“draw tab”, “draw window border”, etc) and you get access to the usual FillRect, DrawString, etc drawing primitives.
There is not much more to say about it, the API is rather self explaining and you can figure out the remaining parts by experimenting.
The easiest way to build your decorator is probably from inside the Haiku sourcecode repository, as I don’t know if we published the required headers to do it elsewhere (but maybe @s40in did the work for that?).