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Using Cocoa cursors in a Carbon world

Hello Everyone,

I've been meaning to write this email-list a nice letter stating how much I
appreciate everyone's help and being a part of the community (even if I wait
to contribute until I see no one knows an answer) - however, now is not that
moment :)

I've been struggling with a problem that I would appreciate your suggestions
on. I believe I have exhausted my options, but I thought I would check with
my peers to see if they have any other ideas.

Our application is switching over to a system where we are using NSCursor
for the majority (not all - time constraints) of our cursors. It works quite
nicely. I didn't write the code, but it was written by a Software Engineer
who did a good job.

Unfortunately, he's gone and we are experiencing some issues. It seems that
on the PowerPC (Tiger and Leopard), when the application switches the cursor
from a Carbon cursor (via MacGetCursor and MacSetCursor) to a Cocoa cursor
(via NSImage to NSCursor and NSCursor's -set function) one can see a flicker
of the Carbon cursor in the vicinity of the mouse position (not where the
hotspot is).

I thought that perhaps the issue was switching between the two types. So as
a test, I changed the code to not switch to a Carbon cursor ever, but switch
to another Cocoa based cursor. Flicker was gone. Yay, I thought.

So my next step was to find a way to create a Cocoa based cursor from the
Carbon CursHandle. I found some code on the internet which appears to
fulfill that intention (I've attached it for your info - it doesn't seem to
completely work, but it displays a similar image to what is expected). So
now, I should be switching from Cocoa cursor to Cocoa cursor.

Yet I still see a flicker.

So I thought that perhaps the call MacGetCursor, which was made in the code
to generate the Carbon based Cocoa cursor was causing a problem. So I
changed the code so that it caches the Cocoa cursors and only calls
MacGetCursor for the first time the Carbon-based Cocoa cursor is created.
Flicker still happens.

I've tried tracking down and logging any other call to MacSetCursor so that
I could see if there was any legacy cursor setting while switching between
Carbon/Carbon-based-Cocoa cursor and new Cocoa cursor. No calls to
MacSetCursor are made.

So, now I'm out of ideas. Anyone familiar with pixel copying code able to
comment on the code I've attached with regards to correctness? Anyone else
had to deal with this problem? Ideas? I'm ready to try any suggestion.

Thank you in advance,
Lyndsey Ferguson
-- 
Mr. Lyndsey D. Ferguson
Software Engineer
Nemetschek N.A., Inc.
http://www.nemetschek.net



static NSImageRep* CreateImageRepWith16BitsOfData(const Bits16 data, const Bits16 mask)
 {
	NSBitmapImageRep *result = NULL;
	
	unsigned char *bmData = NULL;
	
	int x;
	int y;
	
	uint16_t row;
	uint16_t rowMask;

	if (data && mask) {
		result = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
														 pixelsWide:16
														 pixelsHigh:16
													  bitsPerSample:8
													samplesPerPixel:2
														   hasAlpha:YES
														   isPlanar:NO
													 colorSpaceName:NSDeviceBlackColorSpace
														bytesPerRow:32
													   bitsPerPixel:16];
		
		bmData = [result bitmapData];
		
		for (y = 0; y < 16; y++) {
			row = CFSwapInt16BigToHost(data[y]);
			rowMask = CFSwapInt16BigToHost(mask[y]);
			for (x = 0; x < 16; x++) {
				bmData[0] = (row & (1 << (15 - x))) ? 0xFF : 0x00;
				bmData[1] = (rowMask & (1 << (15 - x))) ? 0xFF : 0x00;
				bmData += 2;
			}
		}
		return [result autorelease];
	}
	
	return nil;
}

static NSImage* CreateNSImageFromCarbonCursor( CursHandle legacyCursorH )
{
	NSImage* cursorImage = [[NSImage alloc] initWithSize: NSMakeSize(16.0f, 16.0f) ];
	
	[cursorImage addRepresentation: CreateImageRepWith16BitsOfData((*legacyCursorH)->data, (*legacyCursorH)->mask)];
	
	return cursorImage;
}
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