Is it possible to draw text with shadows using the NSString UIKit additions?

Question

Is it possible to draw with simple text shadows when using the NSString UIKit additions? I mean without writing code to draw twice in two colors, as can be done with various

Answer 1

The following snippet uses CALayer to add shadow around the edges of the characters in a UILabel:

 _helloLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 320, 30)];
[_helloLabel setBackgroundColor:[UIColor clearColor]];
[_helloLabel setTextColor:[UIColor whiteColor]];
[_helloLabel setTextAlignment:NSTextAlignmentCenter];
[_helloLabel setFont:[UIFont lightApplicationFontOfSize:30]];

_helloLabel.layer.shadowColor = UIColorFromRGB(0xd04942).CGColor;
_helloLabel.layer.shadowOffset = CGSizeMake(0, 0);
_helloLabel.layer.shadowRadius = 2.0;
_helloLabel.layer.shadowOpacity = 1.0;

[self addSubview:_helloLabel];

. . normally this would add a shadow around the border, but UILabel seems to treat these properties as a special case.

Answer 2

A couple of thoughts:

1. The UITextAttributeTextShadow... keys are intended for when using a text attribute dictionary with, for example, UIAppearance methods:

   NSDictionary *attributes = @{UITextAttributeTextShadowColor  : [UIColor blackColor],
                                UITextAttributeTextShadowOffset : [NSValue valueWithUIOffset:UIOffsetMake(2.0, 0.0)],
                                UITextAttributeTextColor        : [UIColor yellowColor]};
   
   [[UINavigationBar appearance] setTitleTextAttributes:attributes];
   

   The UITextAttributeTextShadow... keys are designed for use only in those methods that accept a text attributes dictionary.

2. The closest equivalent key when drawing text strings is the use of attributed strings with the NSShadowAttributeName key:

   - (void)drawRect:(CGRect)rect
   {
       UIFont *font = [UIFont systemFontOfSize:50];
   
       NSShadow *shadow = [[NSShadow alloc] init];
       shadow.shadowColor = [UIColor blackColor];
       shadow.shadowBlurRadius = 0.0;
       shadow.shadowOffset = CGSizeMake(0.0, 2.0);
   
       NSDictionary *attributes = @{NSShadowAttributeName          : shadow,
                                    NSForegroundColorAttributeName : [UIColor yellowColor],
                                    NSFontAttributeName            : font};
   
       NSAttributedString *attributedText = [[NSAttributedString alloc] initWithString:@"this has shadows" attributes:attributes];
   
       [attributedText drawInRect:rect];
   }
   

   If you're concerned about the performance hit of a shadow algorithm capable of doing a bezier curve shadow, though, NSShadow may suffer from that. But doing some benchmarks, changing the shadowBlurRadius dramatically affects performance. For example, animating the rotation of a complex multi-line text with a shadowBlurRadius of 10.0 on a slow iPhone 3GS achieved a frame rate of 31 fps, but changing shadowBlurRadius to 0.0 yielded a frame rate of 60 fps.

   Bottom line, using a shadow blur radius of 0.0 eliminates most (if not all) of the computational overhead of a bezier generated shadow.

3. FYI, I experience a similar performance improvement by setting the blur value to 0.0 for CGContextSetShadow, just like I experienced with the attributed text rendition above.

Bottom line, I don't think you should fear the computational overhead of bezier-based shadows as long as you use a blur radius of 0.0. I wouldn't be surprised if writing the text twice yourself, once for the shadow and again for the foreground color, might even be a bit more efficient, but I'm not sure if the difference will be observable. But I don't know of any API call that will do that for you (other than CGContextSetShadow with blur of 0.0).