Re: Implementing CFSTR() in corebase

[Vincent R.]

On Fri, 22 Jan 2010 13:26:00 -0700, Eric Wasylishen
<address@hidden>
wrote:
> On 2010-01-22, at 9:53 AM, David Chisnall wrote:
> 
>> Hi Stef,
>> 
>> I had this discussion with Eric yesterday, so good timing...
>> 
>> On OS X, CSTR() calls one of two functions.  
>> 
> 
> Hi,
> On a related note, regarding Opal, David and I decided that Opal should
> just use Foundation directly (internally). The main reasons are:
> 
> - There is no way (with the public API of CoreFoundation) to create new
> CoreFoundation types . The CG objects need to respond to -[retain] and
> -[release], as well as CFRetain(), and the other CF functions available
for
> all CF types, so they really have to be instances of NSObject
subclasses.
> - We need constant Obj-C/CF strings - it sounds like it is best to just
> use @"...".
> 
> Initially I was interested in making Opal independent of Foundation, and
> able to work with Apple's CF or CFLite, but now I think it's not worth
the
> effort. 
> 
Hum Wait. This is exactly what I am working on windows. I have compiled
CoreFoundationLite and now I implement
CoreGraphics with openVG/cairo backend.
First idea was also to be able to use Objective-C but when I read all your
stuff I think it's far too complicated
so I am happy to have a CoreFoundation/Coregraphics writtent in plain C.
However I don't understand your sentence : "There is no way (with the
public API of CoreFoundation) to create new
 CoreFoundation types"...
What do you mean ? 

For instance my CGContext is implemented as shown below : 

static CFRuntimeClass CGContextClass = 
  {
    0,                  // version
    "CGContext",        // className
    0,                  // init
    0,                  // copy
    CGContextFinalize,  // finalize
        0,              // equal
        0,              // hash
        0,              // copyFormattingDesc
        0               // copyDebugDesc
  };
CFTypeID __kCGContextID = _kCFRuntimeNotATypeID;


CFTypeID CGContextGetTypeID(void)
{
        return CGTypeRegisterWithCallbacks(&__kCGContextID, &CGContextClass);
}

CFTypeID CGTypeRegisterWithCallbacks(CFTypeID* typeID, CFRuntimeClass*
rtclass)
{
        CFTypeID id;

        if (*typeID != _kCFRuntimeNotATypeID) { return *typeID; }

        
        id = _CFRuntimeRegisterClass(rtclass);
        *typeID = id;

        return id;
}


CFTypeRef CGTypeCreateInstance(CFTypeID id, CFIndex size)
{
        return CGTypeCreateInstanceWithAllocator(0, id, size);
}

CFTypeRef CGTypeCreateInstanceWithAllocator(CFAllocatorRef allocator,
CFTypeID id, CFIndex size)
{
        CFTypeRef type;
        CFRuntimeClass* rtc;
        char* ptr;
        

        /* Create the CFType */
        //
        type = _CFRuntimeCreateInstance(allocator, id, size, NULL);
        CHK(type);

        ///* Init with zero values all fields except our base object */
        ptr = (char*)type;
        memset((void*)(ptr + sizeof(CFRuntimeBase)), 0, size);
        
        return type;

Cleanup:
        return NULL;
}