What is wrong with this code?even i tried retaining CF objects, it crashes in lion

Question

CGContextRef ctx = CGContextRetain([[NSGraphicsContext currentContext] graphicsPort]);
CGColorRef color = CGColorRetain([NSColor colorWithCalibratedRed:0 green:0 blue:0 alpha:0.5f].CGColor);

CGContextSaveGState(ctx);
{
    CGContextSetFillColorWithColor(ctx, color);
    CGContextFillRect(ctx, dirtyRect);
}
CGContextRestoreGState(ctx);

CGColorRelease(color);
CGContextRelease(ctx);

Answer 1

Like the error message says, NSColor objects don't respond to CGColor messages in Lion—that method was added in 10.8. On 10.7, you will have to convert the NSColor to a CGColor yourself.

Here's a function that does the conversion. On 10.8, it just returns the NSColor's CGColor. If that isn't available, it does the conversion itself.

CGColorRef PRHCreateCGColorWithNSColor(NSColor *color) {
    if ([color respondsToSelector:@selector(CGColor)]) {
        CGColorRef cgColor = [color CGColor];
        return cgColor != NULL ? (CGColorRef)CFRetain(cgColor) : NULL;
    }

    NSString *colorSpaceName = [color colorSpaceName];
    NSColorSpace *colorSpaceNS;
    if ([colorSpaceName isEqualToString:NSNamedColorSpace] || [colorSpaceName isEqualToString:NSPatternColorSpace]) {
        colorSpaceNS = [NSColorSpace genericRGBColorSpace];
        color = [color colorUsingColorSpace:colorSpaceNS];
    } else {
        colorSpaceNS = [color colorSpace];
    }
    CGColorSpaceRef colorSpace = [colorSpaceNS CGColorSpace];

    size_t numberOfComponents = CGColorSpaceGetNumberOfComponents(colorSpace);
    CGFloat components[numberOfComponents];
    [color getComponents:components];

    return CGColorCreate(colorSpace, components);
}