UIFontWeightTrait Ignored When Creating a New Font – TextKit Bug or a Jared Goof?
Given the following code and a device running iOS 7.1 or later:
NSDictionary *fontTraitsDictionary = @{UIFontWeightTrait : @(-1.0)};
NSDictionary *attributesDictionary = @{
UIFontDescriptorFamilyAttribute : @"Helvetica Neue",
UIFontDescriptorTraitsAttribute : fontTraitsDictionary
};
UIFontDescriptor *ultraLightDescriptor = [UIFontDescriptor fontDescriptorWithFontAttributes:attributesDictionary];
UIFont *shouldBeAnUltraLightFont = [UIFont fontWithDescriptor:ultraLightDescriptor size:24];
NSLog(@"%@", shouldBeAnUltraLightFont);
I would expect the value of shouldBeAnUltraLightFont to be an instance of HelveticaNeue-UltraLight, but instead it is:
<UICTFont: 0x908d160> font-family: "Helvetica"; font-weight: normal; font-style: normal; font-size: 24.00pt
I am following the Apple documentation as far as I understand it. Why is the font family and font weight information completely ignored?
Things I’ve Tried
Here are some of the things I’ve tried:
- I’ve tried other family names like Helvetica, Avenir, etc.
- I’ve tried other font weights in the valid range from -1 to 1, in increments of 0.25
Regardless of these changes, the font returned is always a vanilla instance of Helvetica at normal weight. The only exception is when I remove the UIFontDescriptorTraitsAttribute key/value pair from the attributes dictionary. This results in a 24-point, normal-weight instance of whatever font family I specified.
Things I Can’t Use
- I can’t use any of the preferred fonts because they’re not guaranteed to be an ultra-light weight.
- I can’t use any of the symbolic font traits because none of them specify an ultra light or even a light weight font.
- I can’t hard-code the font name for Helvetica Neue UltraLight for reasons described below.
Why This Matters
A design calls for an ultra-light system font, which in practice should be an instance of Helvetica Neue UltraLight. I could manually specify something like this:
font = [UIFont fontWithName:@"HelveticaNeue-UltraLight"];
The problem with this approach is that it’s prone to errors. When iOS 7.0.3 was released, Apple quietly renamed all the Helvetica Neue italic font filenames, which broke a lot of apps that were manually specifying the old font names. So I need a solution that is resistant to future errors of this kind, but still allows me to get a specific weight of a system font.
I’ve cross-posted this to Stack Overflow if you have an answer.