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Date: Thu, 15 Oct 2020 14:08:19 -0700 (PDT)
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Subject: GDNative thick binding design
From: Michael Hardeman <mhardeman25@gmail.com>
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I'm working on a binding to the Godot game engine for Ada.
Project link here: https://github.com/MichaelAllenHardeman/gdnative_ada

Once the game engine has loaded your dynamic library it will call the funct=
ion *_nativescript_init (where * is the symbol_prefix defined in the librar=
y resource config file). This function is responsible for registering objec=
ts, object methods, and allocating any memory needed.

What I want to discuss here is that I'm a bit at a loss as to how to design=
 a thick binding wrapper around this object registration pattern. So let me=
 describe the pattern.

I have a very simple example translated from C using the thin binding is he=
re: https://github.com/MichaelAllenHardeman/gdnative_ada/blob/master/exampl=
es/gdnative_c_example/src/simple.adb#L44

The objects must have a name, but may or may not override the constructor/d=
estructor life cycle functions (which you pass in during registration)
There are
https://docs.godotengine.org/en/stable/classes/class_object.html#class-obje=
ct

There is kind of a hierarchy at play as well:

the Node type extends Object=20
https://docs.godotengine.org/en/stable/classes/class_node.html#node

and has addition life cycle events like _process (callback on each frame)
https://docs.godotengine.org/en/stable/classes/class_node.html#class-node-m=
ethod-process

Now I don't even know where to start defining something nice in Ada that wo=
uld match this pattern and would hide all the nastiness from the C binding.=
 I kind of want the tagged record hierarchy structure, with overriding func=
tions, but it should only register methods with godot you've overridden. Ho=
w would I know what methods have been overridden? I feel like I need some k=
ind of generic or helper functions?

 I'm hoping some more experienced people might have some suggestions?