thanks for your comment.
Strangely enough that's what I did by accident the first time.
It actually seems a bit dodgy (at least to my way of thinking) - that not only are the objects of my method parameter list changing, but that the repository of my data if nil will dictate a different behaviour in the method.
I am not a no-side-effect bigot guy, but I can think of clearer ways to structure methods.
So it then took me a while to figure out why my program was not working because i kept thinking - "but my data is just waiting to be filled - I set it to nil!" - and in fact post method, the "data" reference was still pointing to nil. (There were a lot of more obvious things that could be wrong, that i went through first - and having cycled through three different Apple graphics technologies already ...)
I actually need this data pointer to pop into an opengl call.
Trying to reference it by : data = CGBitmapContextGetData(context) does not work. and:
data = Pointer.new_with_type('^v')
#data = CGBitmapContextGetData(context)
data.assign(CGBitmapContextGetData(context))
does not work either (although at least it does not crash - so the type seems to be correct - the pointer is just not pointing to the correct bitmap and garbage is sent to the opengl method).
data = CGBitmapContextGetData(context) will work for me if i create the context (and malloc the data ref) in objective c and return the context.
Thats my workaround and it works fine.
Cheers,
John.
On Jan 9, 2009, at 11:57 PM, Brian Chapados wrote:
If it helps, for CGBitmapContextCreate you just pass NULL ('nil' in
MacRuby) for the void *data parameter and let CoreGraphics handle
allocating memory. Unless you really need to do the allocation
yourself, it is significantly less painful and less error-prone to
have it done automatically, especially if you're using CoreGraphics
from MacRuby.
Brian
On Fri, Jan 9, 2009 at 12:00 AM, John Shea <
johnmacshea@gmail.com> wrote:
Thanks for the pointer ( ;-)) Dave,
I assume that there is some way to make it work since it seems, as you say,
to be catered for, but with my code it either gives back garbage (ie not a
pointer to the image i want) or falls into the debugger depending on whether
i access it more than once.
Never mind, I have a work-around that works fine - it was easy to call out
to an Objective C method where I could create the pointer in the C way (void
*data = malloc(width * height * 4);).
Cheers,
John
On Thu, Jan 8, 2009 at 6:45 PM, Dave Lee <davelee.com@gmail.com> wrote:
try "^v". ^ is pointer, v is void.
If you look at the .bridgesupport file, in this case
/System/Library/Frameworks/ApplicationServices.framework/Frameworks/CoreGraphics.framework/Resources/BridgeSupport/CoreGraphicsFull.bridgesupport,
you'll see the the objc types listed for the various functions,
structs, etc.
Dave
On Sat, Jan 3, 2009 at 12:28 AM, John Shea <johnmacshea@gmail.com> wrote:
So kind of on this topic ..
which one of these ("c", "i", "s" etc) do I use for void pointers (to
memory) eg. the data parameter in the method below? (when otherwise
appropriately changed to ruby and Application.services imported etc).
CGContextRef CGBitmapContextCreate (
void *data,
size_t width,
size_t height,
size_t bitsPerComponent,
size_t bytesPerRow,
CGColorSpaceRef colorspace,
CGBitmapInfo bitmapInfo
);
Cheers,
J
On Jan 2, 2009, at 11:21 PM, Dave Lee wrote:
On Thu, Jan 1, 2009 at 7:37 PM, Lachie <lachiec@gmail.com> wrote:
Cheque it:
http://developer.apple.com/DOCUMENTATION/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/chapter_7_section_1.html#//apple_ref/doc/uid/TP40008048-CH100-SW1
see also: /usr/include/objc/runtime.h
Dave
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