Open Radar

 
05-Oct-2011 03:11 PM Ben Martz:
Summary:

After migrating my iOS 4 project to iOS 5 and ARC, I struggled to figure out how to properly assign an array of color values to the colors property of a CAGradientLayer. I also discovered that my first attempt to work around the issue resulted in code that worked correctly in the simulator but not on a real device.

I found the following thread on the iOS 5 Beta forum which got me pointed in the correct direction to resolve my issue: https://devforums.apple.com/message/550670

Steps to Reproduce:

CAGradientLayer *gradientLayer = [[CAGradientLayer alloc] init];		

CGColorRef topColor = [[UIColor colorWithRed:0.933333333333333 green:0.933333333333333 blue:0.941176470588235 alpha:1.0] CGColor];
CGColorRef bottomColor = [[UIColor colorWithRed:0.827450980392157 green:0.827450980392157 blue:0.850980392156863 alpha:1.0] CGColor];

// #1 COMPILER ERROR: Cast of C pointer type 'CGColorRef' to Objective-C pointer type 'id' requires a bridged cast
gradientLayer.colors = [NSArray arrayWithObjects:(id)topColor, (id)bottomColor, nil];

// #2 Works in correctly on iPad 5.0 simulator (Xcode 4.2 GM), however throws EXC_BAD_ACCESS on physical 1st gen iPad device running iOS 5.0 GM
gradientLayer.colors = [NSArray arrayWithObjects:(__bridge id)topColor, (__bridge id)bottomColor, nil];

// #3 The explicit inline cast of UIColor property CGColor to id appears to be the ONLY way to make this bridged assignment
// compile and generate code that works correctly on both the simulator and a real device
gradientLayer.colors = [NSArray arrayWithObjects:
     (id)[[UIColor colorWithRed:0.933333333333333 green:0.933333333333333 blue:0.941176470588235 alpha:1.0] CGColor],
     (id)[[UIColor colorWithRed:0.827450980392157 green:0.827450980392157 blue:0.850980392156863 alpha:1.0] CGColor],
     nil];

Expected Results:

Examples #1 and #3 should be considered identical by the compiler. The current requirement that values be provided inline breaks generally accepted best practices of code and constant value reuse.

The equivalence of example #2 is unknown since I can not claim to be 100% clear on the different bridging modes. Nonetheless, IMO, example #2 should demonstrate identical results on both the simulator and a physical device.

Actual Results:

Provided inline with steps to reproduce.

Regression:

n/a

Notes:

n/a

05-Oct-2011 03:22 PM Ben Martz:
Continuing my work, I have found that even a simple color assignment* as follows works correctly on the simulator but DOES NOT work on a physical device:

* declare CGColorRef variable; assign CGColorRef to variable; assign variable to [CAGradientLayer backgroundColor] property

- (void)drawRect:(CGRect)rect
{
	if ([self isHighlighted] != wasHighlighted)
	{
		wasHighlighted = [self isHighlighted];
		
		CGColorRef shadowColor, highlightColor, topColor, bottomColor;

		if ([self isHighlighted])
		{
			shadowColor = [[UIColor colorWithRed:0.356862745098039 green:0.36078431372549 blue:0.380392156862745 alpha:1.0] CGColor];
			highlightColor = [[UIColor colorWithRed:0.850980392156863 green:0.854901960784314 blue:0.870588235294118 alpha:1.0] CGColor];
			topColor = [[UIColor colorWithRed:0.701960784313725 green:0.709803921568627 blue:0.737254901960784 alpha:1.0] CGColor];
			bottomColor = [[UIColor colorWithRed:0.513725490196078 green:0.52156862745098 blue:0.549019607843137 alpha:1.0] CGColor];
		}
		else
		{
			shadowColor = [[UIColor colorWithRed:0.513725490196078 green:0.513725490196078 blue:0.525490196078431 alpha:1.0] CGColor];
			highlightColor = [[UIColor whiteColor] CGColor];
			topColor = [[UIColor colorWithRed:0.933333333333333 green:0.933333333333333 blue:0.941176470588235 alpha:1.0] CGColor];
			bottomColor = [[UIColor colorWithRed:0.827450980392157 green:0.827450980392157 blue:0.850980392156863 alpha:1.0] CGColor];
		}
		
		// EXC_BAD_ACCESS on physical device
		[shadowLayer setBackgroundColor:shadowColor];

		// EXC_BAD_ACCESS on physical device
		[highlightLayer setBackgroundColor:highlightColor];

		// force instant response animation
		CABasicAnimation* selectionAnimation = [CABasicAnimation animationWithKeyPath:@"colors"];
		selectionAnimation.delegate = self;
		selectionAnimation.duration = 0;
		selectionAnimation.fillMode = kCAFillModeForwards;
		selectionAnimation.removedOnCompletion = false;
		
		selectionAnimation.fromValue = (id)[NSArray arrayWithObjects:(__bridge id)topColor, (__bridge id)bottomColor, nil];
		selectionAnimation.toValue = (id)[NSArray arrayWithObjects:(__bridge id)topColor, (__bridge id)bottomColor, nil];
		
		[gradientLayer addAnimation:selectionAnimation forKey:@"selectionAnimation"];
	}
	
	[super drawRect:rect];	
}