Implementation
Implementing the GTK-server leads to the following considerations.
1) Accessing foreign functions is only possible when the accessed libraries are created with a non object oriented programming language like C or Pascal. Libraries created with C++ for example, use name mangling in order to unify overloaded functions. This means that the actual functionname in a C++ library cannot be known once the shared library has been compiled. Hence the functions in such a library cannot be accessed. Therefore, libraries like wxWidgets, the Qt toolkit, FLTK which are programmed in C++, cannot be accessed with the GTK-server concept. More on this matter is explained here.
2) The GTK library was implemented in the C programming language. Since C is a strongly typed programming language, the interpreted program needs to know the type of arguments and the type of the return value for each GTK function during runtime. These can be defined on-the-fly or in a configuration file, which is parsed by the GTK-server during startup. However, the GTK-server does not know the actual functions which are going to be used by the interpreted client program, so for GTK-server all arguments and return values for each GTK function are variable types.
This leads to a problem for the implementation, because the GTK functions and the corresponding arguments and return values cannot be hardcoded into the GTK-server binary.
The way to resolve this is by using a foreign function interface. Currently, four external foreign function interfaces are supported by GTK-server: libFFI, FFCALL, C/Invoke and DynCall. One of these libraries should be available on the target system, in order to compile the GTK-server successfully.
Read more about this topic: GTK-server