[Rubycocoa-talk] NSBitmapImageRep#bitmapData

[Ralph B. <ra...@de...>]

Hey everyone,

I'm having a bit of trouble using NSBitmapImageRep#bitmapData. Or at 
least, I think I am. (Source bits are included below, there is a 
testcase up at http://deadfeed.net/sandbox/testcase.zip - beware, the 
Makefile dependencies are not 100%.)

The NSBitmapImageRep should display data in a window, and that data 
should be coming from a C++ extension, via SWIG. Ruby should create the 
window, create views, and call a C++ function to fill the bitmap. But I 
all I get is a bus error (presumably because the pointer handed to the 
C++ function is off).

I have a class, FracWindow, which initializes the window and views 
(@fracView). FracWindow#ShowImage passes a pointer (char *) to the C++ 
function, which then fills it.

def showImage()
	bitmapRep=OSX::NSBitmapImageRep.alloc.initWithBitmapDataPlanes(nil,
		:pixelsWide, 256,
		:pixelsHigh, 256,
		:bitsPerSample, 8,
		:samplesPerPixel, 4,
		:hasAlpha, true,
		:isPlanar, true,
		:colorSpaceName, "NSDeviceRGBColorSpace",
		:bytesPerRow, 0,
		:bitsPerPixel, 0
	)
	
	Testinterface::Test(bitmapRep.bitmapData())
	
	image=OSX::NSImage.alloc.initWithSize([256, 256])
	image.addRepresentation(bitmapRep)
	@fracView.setImage(image)
	@fracView.setNeedsDisplay(true)
end

Testinterface::Test looks like this:

void Test(BitmapPointer p)
{
	std::cout << &p << std::endl;

	unsigned char *pp=p;

	pp[0]=255;
	pp[1]=0;
	pp[2]=0;
	pp[3]=0;
	pp[4]=0;
	pp[5]=0;
	pp[6]=0;
	pp[7]=0;

/*	for (int y=0; y<256; y++)
	{
		for (int x=0; x<256; x++)
		{
			char f=y/2+x/2;
			*pp++=f;
			// *pp++=f;
			// *pp++=f;
			// *pp++=f;
		}
	}*/
}

I made a BitmapPointer typedef in order to let SWIG distinguish the 
data type (char *). The SWIG typemap looks like this:

%typemap(in) BitmapPointer {
	if (TYPE($input)==T_STRING)
	{
	    $1 = StringValuePtr($input);
	}
	else
	{
		rb_raise(rb_eTypeError, "Expected bitmapdata");
		$1 = 0;
	}
}

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?

I'd appreciate it if anyone could point me in the right direction.

Regards,
Ralph Brorsen