Re: [Rubycocoa-talk] NSBitmapImageRep#bitmapData

[Jonathan P. <jp...@dc...>]

On 14 Jul 2005, at 21:08, Ralph Brorsen wrote:

> The main event here is of course "$1 = StringValuePtr($input);",  
> which should, as I understand it return a char pointer to the  
> string data which bitmapRep.bitmapData() returned. The reason it is  
> converted to a Ruby string, I assume, is because RubyCocoa sees the  
> char *, and thinks it is a string. Perhaps the string is copied to  
> an internal buffer?

As you've identified, the return value of bitmapData is being  
converted to a ruby string. The easiest solution (since you're  
already dealing with some native code) may be to pass the  
NSBitmapImageRep pointer to your native code and get the pointer to  
the bitmapData from within your native code.

A better solution would involve some changes to RubyCocoa to better  
support this.

You could do the 'easy' solution from Objective C++ or link in a  
small bit of Objective C code to do the work for you.

The Objective C object pointer (of type 'id' or whatever your object  
is - e.g., 'NSBitmapImageRep*') is available by calling __ocid__ on  
the ruby object. So, from within your native code you could do  
something like:

    id ocobj = (id) NUM2UINT( rb_funcall(obj, rb_intern("__ocid__"),  
0) );
    unsigned char *pixels = [(NSBitmapImageRep*) ocobj bitmapFormat];

Another option would be to call into RubyCocoa to get it to do this  
for you. There's a function 'rbobj_get_ocid' which does what you want  
(in a more robust fashion). The C function prototype (from  
mdl_osxobjc.h) is:

     id    rbobj_get_ocid (VALUE rcv);

Provided you can get the linker to be happy with this (e.g., by  
linking your native code against RubyCocoa too) it should work.

I'm sorry if the above is a bit vague. I've not tested it (just typed  
into email), but something along those lines should work.

Jonathan