Bob Spryn Bob Spryn -4 years ago 160
iOS Question

How to use a custom font with dynamic text sizes in iOS7

In iOS7 there are new API's for getting a font that is automatically adjusted to the text size the user has set in their preferences.

It looks something like this to use it:

UIFont *myFont = [UIFont fontWithDescriptor:[UIFontDescriptor preferredFontDescriptorWithTextStyle:UIFontTextStyleHeadline] size:0];


Now whatever text you assign this to will move up and down in font size as the user changes their system text size setting. (Remember to listen to the
name:UIContentSizeCategoryDidChangeNotification
notification and update your view to account for the change in size).

How do I use dynamic text with a font other than the default Helvetica-Neue?


Answer Source

Behind the scenes of that API, apple has some sort of lookup table that returns a specific font family, size, and sometimes symbolic traits (like bold) that (e.g. UIFontTextStyleHeadline) and the user's preferred text size. The latter is a string pulled off of the sharedApplication like this:

[UIApplication sharedApplication].preferredContentSizeCategory;

(I logged out all the default sizes/fonts/traits for Helvetica-Neue for the various dynamic text sizes). We've since added handling for the accessibility sizes, which is important.

So all you really have to do is build a similar lookup table. Our designer created a simple spreadsheet for me:

Font size lookup table

Notice that we added a couple styles (caption 3 & 4) to have 8 instead of 6 to choose from.

Then you'll want to put it someplace convenient, like a category on UIFontDescriptor. You'll want your method to return a UIFontDescriptor like Apple's API, so that it's still easy to adjust with symbolic traits, etc.

My category looks like this:

UIFontDescriptor+AvenirNext.h

#import <UIKit/UIKit.h>

extern NSString *const ANUIFontTextStyleCaption3;

@interface UIFontDescriptor (AvenirNext)

+(UIFontDescriptor *)preferredAvenirNextFontDescriptorWithTextStyle:(NSString *)style;

@end

UIFontDescriptor+AvenirNext.m

#import "UIFontDescriptor+AvenirNext.h"

NSString *const ANUIFontTextStyleCaption3 = @"ANUIFontTextStyleCaption3";
NSString *const ANUIFontTextStyleCaption4 = @"ANUIFontTextStyleCaption4";

@implementation UIFontDescriptor (AvenirNext)
+(UIFontDescriptor *)preferredAvenirNextFontDescriptorWithTextStyle:(NSString *)style {
    static dispatch_once_t onceToken;
    static NSDictionary *fontSizeTable;
    dispatch_once(&onceToken, ^{
        fontSizeTable = @{
          UIFontTextStyleHeadline: @{
                                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: @26,
                                    UIContentSizeCategoryAccessibilityExtraExtraLarge: @25,
                                    UIContentSizeCategoryAccessibilityExtraLarge: @24,
                                    UIContentSizeCategoryAccessibilityLarge: @24,
                                    UIContentSizeCategoryAccessibilityMedium: @23,
                                    UIContentSizeCategoryExtraExtraExtraLarge: @23,
                                    UIContentSizeCategoryExtraExtraLarge: @22,
                                    UIContentSizeCategoryExtraLarge: @21,
                                    UIContentSizeCategoryLarge: @20,
                                    UIContentSizeCategoryMedium: @19,
                                    UIContentSizeCategorySmall: @18,
                                    UIContentSizeCategoryExtraSmall: @17,},

       UIFontTextStyleSubheadline: @{
                                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: @24,
                                    UIContentSizeCategoryAccessibilityExtraExtraLarge: @23,
                                    UIContentSizeCategoryAccessibilityExtraLarge: @22,
                                    UIContentSizeCategoryAccessibilityLarge: @22,
                                    UIContentSizeCategoryAccessibilityMedium: @21,
                                    UIContentSizeCategoryExtraExtraExtraLarge: @21,
                                    UIContentSizeCategoryExtraExtraLarge: @20,
                                    UIContentSizeCategoryExtraLarge: @19,
                                    UIContentSizeCategoryLarge: @18,
                                    UIContentSizeCategoryMedium: @17,
                                    UIContentSizeCategorySmall: @16,
                                    UIContentSizeCategoryExtraSmall: @15,},

              UIFontTextStyleBody: @{
                                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: @21,
                                    UIContentSizeCategoryAccessibilityExtraExtraLarge: @20,
                                    UIContentSizeCategoryAccessibilityExtraLarge: @19,
                                    UIContentSizeCategoryAccessibilityLarge: @19,
                                    UIContentSizeCategoryAccessibilityMedium: @18,
                                    UIContentSizeCategoryExtraExtraExtraLarge: @18,
                                    UIContentSizeCategoryExtraExtraLarge: @17,
                                    UIContentSizeCategoryExtraLarge: @16,
                                    UIContentSizeCategoryLarge: @15,
                                    UIContentSizeCategoryMedium: @14,
                                    UIContentSizeCategorySmall: @13,
                                    UIContentSizeCategoryExtraSmall: @12,},

          UIFontTextStyleCaption1: @{
                                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: @19,
                                    UIContentSizeCategoryAccessibilityExtraExtraLarge: @18,
                                    UIContentSizeCategoryAccessibilityExtraLarge: @17,
                                    UIContentSizeCategoryAccessibilityLarge: @17,
                                    UIContentSizeCategoryAccessibilityMedium: @16,
                                    UIContentSizeCategoryExtraExtraExtraLarge: @16,
                                    UIContentSizeCategoryExtraExtraLarge: @16,
                                    UIContentSizeCategoryExtraLarge: @15,
                                    UIContentSizeCategoryLarge: @14,
                                    UIContentSizeCategoryMedium: @13,
                                    UIContentSizeCategorySmall: @12,
                                    UIContentSizeCategoryExtraSmall: @12,},

          UIFontTextStyleCaption2: @{
                                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: @18,
                                    UIContentSizeCategoryAccessibilityExtraExtraLarge: @17,
                                    UIContentSizeCategoryAccessibilityExtraLarge: @16,
                                    UIContentSizeCategoryAccessibilityLarge: @16,
                                    UIContentSizeCategoryAccessibilityMedium: @15,
                                    UIContentSizeCategoryExtraExtraExtraLarge: @15,
                                    UIContentSizeCategoryExtraExtraLarge: @14,
                                    UIContentSizeCategoryExtraLarge: @14,
                                    UIContentSizeCategoryLarge: @13,
                                    UIContentSizeCategoryMedium: @12,
                                    UIContentSizeCategorySmall: @12,
                                    UIContentSizeCategoryExtraSmall: @11,},

        ANUIFontTextStyleCaption3: @{
                                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: @17,
                                    UIContentSizeCategoryAccessibilityExtraExtraLarge: @16,
                                    UIContentSizeCategoryAccessibilityExtraLarge: @15,
                                    UIContentSizeCategoryAccessibilityLarge: @15,
                                    UIContentSizeCategoryAccessibilityMedium: @14,
                                    UIContentSizeCategoryExtraExtraExtraLarge: @14,
                                    UIContentSizeCategoryExtraExtraLarge: @13,
                                    UIContentSizeCategoryExtraLarge: @12,
                                    UIContentSizeCategoryLarge: @12,
                                    UIContentSizeCategoryMedium: @12,
                                    UIContentSizeCategorySmall: @11,
                                    UIContentSizeCategoryExtraSmall: @10,},

          UIFontTextStyleFootnote: @{
                                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: @16,
                                    UIContentSizeCategoryAccessibilityExtraExtraLarge: @15,
                                    UIContentSizeCategoryAccessibilityExtraLarge: @14,
                                    UIContentSizeCategoryAccessibilityLarge: @14,
                                    UIContentSizeCategoryAccessibilityMedium: @13,
                                    UIContentSizeCategoryExtraExtraExtraLarge: @13,
                                    UIContentSizeCategoryExtraExtraLarge: @12,
                                    UIContentSizeCategoryExtraLarge: @12,
                                    UIContentSizeCategoryLarge: @11,
                                    UIContentSizeCategoryMedium: @11,
                                    UIContentSizeCategorySmall: @10,
                                    UIContentSizeCategoryExtraSmall: @10,},

          ANUIFontTextStyleCaption4: @{
                                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: @15,
                                    UIContentSizeCategoryAccessibilityExtraExtraLarge: @14,
                                    UIContentSizeCategoryAccessibilityExtraLarge: @13,
                                    UIContentSizeCategoryAccessibilityLarge: @13,
                                    UIContentSizeCategoryAccessibilityMedium: @12,
                                    UIContentSizeCategoryExtraExtraExtraLarge: @12,
                                    UIContentSizeCategoryExtraExtraLarge: @11,
                                    UIContentSizeCategoryExtraLarge: @11,
                                    UIContentSizeCategoryLarge: @10,
                                    UIContentSizeCategoryMedium: @10,
                                    UIContentSizeCategorySmall: @9,
                                    UIContentSizeCategoryExtraSmall: @9,},
        };
    });


    NSString *contentSize = [UIApplication sharedApplication].preferredContentSizeCategory;
    return [UIFontDescriptor fontDescriptorWithName:[self preferredFontName] size:((NSNumber *)fontSizeTable[style][contentSize]).floatValue];
}
+(UIFontDescriptor *)preferredAvenirNextDemiBoldFontDescriptorWithTextStyle:(NSString *)style {
    return [[self preferredAvenirNextFontDescriptorWithTextStyle:style] fontDescriptorWithSymbolicTraits:UIFontDescriptorTraitBold];
}

+(UIFontDescriptor *)preferredAvenirNextBoldFontDescriptorWithTextStyle:(NSString *)style {
    return [UIFontDescriptor fontDescriptorWithName:[self preferredBoldFontName] size:[self preferredAvenirNextFontDescriptorWithTextStyle:style].pointSize];
}

+(NSString *)preferredFontName {
    return @"AvenirNext-Medium";
}
+(NSString *)preferredBoldFontName {
    return @"AvenirNext-Bold";
}

@end

We chose to use the same base font AvenirNext-Medium, and then bold and such via symbolic traits, but you could get crazy and specify different weight variants on your font as part of your lookup table as well if you wanted, like AvenirNext-ExtraBold.

That's all there is to it! We use it like this:

[UIFont fontWithDescriptor:[UIFontDescriptor preferredAvenirNextFontDescriptorWithTextStyle:UIFontTextStyleHeadline] size: 0]
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