On 2010-01-22, at 3:26 PM, Vincent R. wrote:
> On Fri, 22 Jan 2010 13:26:00 -0700, Eric Wasylishen
> <[email protected]>
> 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.
Cool, we should combine our efforts if possible! Implementing CG is a pretty
big task, but Opal is quite far along already. It is licensed under the LGPL
and copyright is assigned to the FSF - is that something you would be
interested in working with?
> 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.
Do you mean the Opal code looks far too complicated? IMHO it's pretty minimal
and simple. (well, a lot of what I have been working on recently is still a
rough prototype and needs to be cleaned up.)
Opal is currently written all in C, and uses a simple home-made object system,
so the CG types are not real CF or Objective-C objects. (I just made some
changes yesterday so it uses Objective-C constant strings, but it's still all C
other than that.) Making the CG objects in to real ObjC/CF objects is something
we need to do at some point.
> 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;
> }
>
I am really a newbie at CoreFoundation - what I meant was I didn't see mention
in the CoreFoundation documentation of how to create/register a new type.
If we could do something in Opal like what you showed and have it work on both
CFLite and GNUstep base + corebase, and keep Opal written in plain C, that
would be great.
Regards,
Eric
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