If we had something like ("O@", typeobject) calldll could be extended so you could do something like psapilib = calldll.getlibrary(....) ps_GetDrawableSurface = calldll.newcall(psapilib.ps_GetDrawableSurface, Carbon.Qd.GrafPortType)
(newcall() arguments are funcpointer, return value type, arg1 type, ...)
You cannot do this currently
Please let me try to summarize what this is doing: Given a type object and a long, create an instance of that type. Is that a correct analysis of what has to be done?
That would allow you to do the same thing, but rather more error prone (i.e. I think it is much more of a hack than what I'm trying to get at). As you noted above WinObj's unfortunately need such a hack, but I would expect to get rid of it as soon as possible. I really don't like passing C pointers around in Python integers.
I completely fail to see how O& fits into the puzzle. AFAICT, conversion of the return value occurs inside cdc_call. There is no tuple to parse anyway nearby.
Not at the moment, but in calldll version 2 there would be. In stead of passing types as "l" or "h" you would pass type objects to newcall(). Newcall() would probably special-case the various ints but for all other types simply call PyArg_Parse(arg, "O@", typeobj, &voidptr).
Here's an outline which could work in 2.2:
Create a subtype of type, having a tp_convert slot:
typedef int (*convert_func)(PyTypeObject *, void **);
typedef struct { PyTypeObject type; convert_func tp_convert; } WrapperTypeType;
and use it as metaclass (metatype?) for your WindowObj:
class WindowObj(...): __metaclass__ = WrapperTypeType
Write a function to return a conversion function:
convert_func *get_converter(PyTypeObject *type) { if (WrapperTypeType_Check(type)) return ((WrapperTypeType *)type)->tp_convert; /* code to check additional types and return their converters */ .... }
and then
if (!PyArg_ParseTuple(args, "O&", get_converter(WinObj_Type), &Window))
How does this sound?
Thomas