[Xcb] language bindings for xcb

[Thomas Hunger]

Hello, 

the following problem came up when I reactivated my old python 
bindings for xcb [1]. It is a more general problem for all 
object-oriented bindings.

Each extension (e.g. render) has its own library and header file. To 
use it from c one uses pkg-config and the appropiate #include.

In my bindings there is a class "Connection" which connects at 
__init__ time. Now I can use the basic functions like this:

>>> import xcb
>>> c = xcb.Connection()
>>> win = c.generate_id()
>>> ...

The connection object in the first example cannot use e.g. 

>>> c.render_create_picture(...) 

because the connection does not now whether the render extension is 
available at all [2]. The module-source would also need all possible 
extensions installed at compile time (modules cannot be developed 
separatly).

If I follow the c-model for extensions the result would be:

>>> import render
>>> render.create_picture(c, ...)

meaning that the connection is passed as the first argument. The 
explicit import ensures that either the render extension module is 
available or an exception is thrown. The extension-modules can also 
be developed separatly. OTOH this is not very object oriented.

Another possibility would be to override the __new__ method of the 
Connection. When __new__ is called it scans for python-xcb-modules 
and creates an attribute for each found module. Connection could then 
be used like this:

>>> c.render.create_picture(...) # module render exists

After all this the question is: What do you think the api should be 
like for object-oriented programming languages?

Tom

[1] I will put them online next week, I am not at home currently.
[2] It is possible to do create additional render_xxx methods for
    the connection class after an "import render" statement. This is
    not trivial to do from c. I also think that it is not very
    intuitive.