Re: [pygccxml-development] Auto-wrapping methods taking non-const reference

[Allen B. <al...@vr...>]

Matthias Baas wrote:

> Allen Bierbaum wrote:
>
>> void getSize(float& width, float& height);
>>
>> To wrap this method a user normally needs to manually write a C++ 
>> wrapper method that will call the function and return the values in a 
>> boost.python.tuple.  This is not difficult to do, but it can get very 
>> tedious in a large API.
>>
>> I know there have been discussions about automating this, but has 
>> anyone actually written code that will do it.  I don't need the code 
>> integrated into pyplusplus or anything like that right now, I just 
>> want to know if someone has code they are willing to share so I don't 
>> have to start from scratch. :)
>
>
> I've implemented something in pypp_api that I called "argument 
> policies". The code for that is in pypp_api/argpolicy.py (the naming 
> is somewhat inconsistent because I initially called it "argument 
> transformers" and the base class for the policies is still called 
> "ArgTransformerBase").
>
> The argument policies are applied via decoration just as the normal 
> call policies. In your case, it would be:
>
> cls.Method("getSize").setArgPolicy(Output(1), Output(2))
>
> This specifies that the first and second argument of the method are 
> actually output values. The Python version of the method will then 
> take no arguments and return a tuple (width, height).
>
> I have a few "standard" arg policies such as Output, InputArray and 
> OutputArray that are defined right in argpolicy.py. I've also a few 
> custom policies in my Maya bindings that do things like checking array 
> bounds or manipulating those Maya status objects.
>
> Those arg policies are actually just specialized code creators that 
> each add a block of C++ code before and after the original 
> function/method invocation. They can also manipulate the argument list 
> and the return value.
> Everything is implemented on top of pyplusplus and currently it only 
> works for methods that don't already create wrappers in pyplusplus. It 
> would be great if this functionality could eventually moved "down" to 
> pyplusplus so that the normal wrapper generation also works like this. 
> This would provide a standard way for a user to inject custom code 
> into the generated wrappers. I'm currently trying to investigate how 
> this could be achieved because I want to make some of my wrapped code 
> thread safe which, I believe, is not possible with the current version 
> of pyplusplus and pypp_api.

This sounds like a great idea.  I like the idea of the interface and how 
you specify that arguments should be used in what way.  Please let me 
know if you need help testing or migrating this to Roman's interface in 
pyplusplus.

-Allen

>
> - Matthias -
>