Is it possible to use iOS 7's modified Helvetica in apps?

问题

For iOS 7, Apple made a special modified version of Helvetica Thin/Light that has rounded periods and colons:

Compare this to using Helvetica-Neue Thin or Helvetica-Neue Light in Xcode:

Is it possible to develop apps with the special modified version with the rounded colons and periods?

EDIT: Turns out these round colons and periods are not custom designed by Apple, they are "character alternates" and you can see them in your favorite font glyph viewer.

回答1:

Here's how to do it. Even reading the documentation, it's very unclear.

First, you have to get the characteristics of a font, which will give you the constants to use in your UIFontDescriptorFeatureSettingsAttribute. I got mine from this post.

This gives you feature type identifier keys, and your options for their values, the feature selector identifier keys.

NSArray *timerDisplaySettings = @[
                                      @{ UIFontFeatureTypeIdentifierKey: @(6),
                                        UIFontFeatureSelectorIdentifierKey: @(1)
                                     },
                                      @{ UIFontFeatureTypeIdentifierKey: @(17),
                                        UIFontFeatureSelectorIdentifierKey: @(1)
                                        }];

then you create a font descriptor by adding to a descriptor - this way you can specify the font name and family via UIFont:

UIFont *font = [UIFont fontWithName:@"HelveticaNeue-UltraLight" size:32];

UIFontDescriptor *originalDescriptor = [font fontDescriptor];
UIFontDescriptor *timerDescriptor =[originalDescriptor fontDescriptorByAddingAttributes: @{ UIFontDescriptorFeatureSettingsAttribute: timerDisplaySettings }];

Then, close the loop and create the font with your descriptor. (The size "0.0" simply means we aren't scaling it from its original size of 32.

UIFont *timerFont = [UIFont fontWithDescriptor: timerDescriptor size:0.0];

回答2:

For the sake of future readers, to see the font features array, in Objective-C it is:

@import CoreText;

and

- (void)fontFeatures:(UIFont *)font {
    NSArray *features = CFBridgingRelease(CTFontCopyFeatures((__bridge CTFontRef)font));

    if (features) {
        NSLog(@"%@: %@", font.fontName, features);
    }
}

For HelveticaNeue-UltraLight that yields:

HelveticaNeue-UltraLight: (
        {
        CTFeatureTypeIdentifier = 1;
        CTFeatureTypeName = Ligatures;
        CTFeatureTypeNameID = 258;
        CTFeatureTypeSelectors =         (
                        {
                CTFeatureSelectorDefault = 1;
                CTFeatureSelectorIdentifier = 2;
                CTFeatureSelectorName = "Common Ligatures";
                CTFeatureSelectorNameID = 259;
            }
        );
    },
        {
        CTFeatureTypeExclusive = 1;
        CTFeatureTypeIdentifier = 6;
        CTFeatureTypeName = "Number Spacing";
        CTFeatureTypeNameID = 262;
        CTFeatureTypeSelectors =         (
                        {
                CTFeatureSelectorDefault = 1;
                CTFeatureSelectorIdentifier = 0;
                CTFeatureSelectorName = "No Change";
                CTFeatureSelectorNameID = 264;
            },
                        {
                CTFeatureSelectorIdentifier = 1;
                CTFeatureSelectorName = "Proportional Numbers";
                CTFeatureSelectorNameID = 263;
            }
        );
    },
        {
        CTFeatureTypeExclusive = 1;
        CTFeatureTypeIdentifier = 17;
        CTFeatureTypeName = "Character Alternatives";
        CTFeatureTypeNameID = 265;
        CTFeatureTypeSelectors =         (
                        {
                CTFeatureSelectorDefault = 1;
                CTFeatureSelectorIdentifier = 0;
                CTFeatureSelectorName = "No Change";
                CTFeatureSelectorNameID = 264;
            },
                        {
                CTFeatureSelectorIdentifier = 1;
                CTFeatureSelectorName = "Time Punctuation";
                CTFeatureSelectorNameID = 266;
            },
                        {
                CTFeatureSelectorIdentifier = 2;
                CTFeatureSelectorName = "Compass Punctuation";
                CTFeatureSelectorNameID = 267;
            },
                        {
                CTFeatureSelectorIdentifier = 3;
                CTFeatureSelectorName = "Weather Punctuation";
                CTFeatureSelectorNameID = 268;
            },
                        {
                CTFeatureSelectorIdentifier = 4;
                CTFeatureSelectorName = "Round Lowercase Punctuation";
                CTFeatureSelectorNameID = 269;
            }
        );
    }
)

Thus, in iOS 8, for HelveticaNeue-UltraLight, key 17 is "Character Alternatives", and value 1 is "Time Punctuation".

To see these features in Swift, it is:

import CoreText

and

func fontFeatures(font: UIFont) {
    if let features = CTFontCopyFeatures(font) as NSArray! {
        println("\(font.fontName): \(features)")
    }
}

回答3:

Yes, these features are accessible to you via iOS 7's new Dynamic Type system. http://tirania.org/monomac/archive/2013/Sep-25.html

来源：https://stackoverflow.com/questions/21594346/is-it-possible-to-use-ios-7s-modified-helvetica-in-apps

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