Fix object return value of builtin types' methods.

[Daylily-Zeleen]

Currently Signal::get_object() and Callable::get_object() will return an invalid Object * without converting by internal::get_object_instance_binding().

This pr fix this problem by adding necessary Conversion for builtin types in binding generator.

[dsnopek]

Thanks!

I haven't tested, although, looking at the code I think you're right about the bug here.

However, rather than having the binding_generator.py add the call to internal::get_object_instance_binding(), I think it'd be better to handle this similar to how we do in other situations.

For example, we have internal::_call_native_mb_ret() (which is similar to the internal::_call_builtin_method_ptr_ret() used here), and it has a partner function to handle returning objects called internal::_call_native_mb_ret_obj() (note the _obj at the end).

We could add an equivalent internal::_call_builtin_method_ptr_ret_obj() and then binding_generator.py could call that when the method returns an Object *.

[Daylily-Zeleen]

@dsnopek OK, I added internal::_call_builtin_method_ptr_ret_obj(), it should be no problem now.

[dsnopek]

Thanks!

However, it would be nice if this code was also re-organized to look like the similar pre-existing code for engine classes - see https://github.com/godotengine/godot-cpp/blob/master/binding_generator.py#L1585

I personally find that a little easier to follow, and it'll make maintaining both chunks of code easier if they have roughly the same structure. Comparing with that code, we also may be missing a case related to enums?

[dsnopek]

There's a type-o here - this variable name should end with a t. However, I think it'd be better if this was made to look more like the code for engine classes which use is_ref as the variable for this. See https://github.com/godotengine/godot-cpp/blob/master/binding_generator.py#L1585

[Daylily-Zeleen]

@dsnopek Although I make it like engine classes now, it seems that there have not method with enum return type in builtin types.
And the structure of engine classes' methods is different from builtin types' methods in "extension_api.json", so I ignore "meta".

[dsnopek]

Thanks! This looks great to me

[dsnopek]

Cherry-picked for 4.2 in PR #1410

[dsnopek]

Cherry-picked for 4.1 in PR #1411