ESDL is an api which invokes corresponding functions in the Sdl and Opengl libraries.
Since most of the functions are 1 to 1 mapping to the original libraries, the descriptions (if any) are brief. For detailed descriptions and manual pages take a look at the SDL and Opengl sites which should be able guide you to the documentation. I have tried to generate link to the descriptions on net, but may have failed in some cases.
With some common sense you should be able to figure out the arguments and return values to the functions. Arguments in the 'C' libraries that are used as out parameters, are often returned as a tuple with values. C functions that take pointer to an array as argument takes a list as argument in erlang (and/or tuple).
The thing that differs are of course the memory handling and memory references, check out the examples.
If you have complaints of non trivial (or errors) arguments or return values, send me an email and I'll try to update the documentation or (the fast way) check the source.
      Init and Quit Functions 
      Video Functions
      Audio Functions
      General Event Functions
      TTF Functions
      Image Functions
      
      Opengl functions that uses pointers requires
      that you use the memory functions in sdl_util 
      to handle the memory references.
      
       GL Functions
      GLU Functions