Use medieval (lowercase, non-lining) numbers

Question

I have a request from a customer to use a certain font in a iOS 7 project because it has medieval numbers.

Is there any way to activate those numbers for a NSAttributedString? As default lining numbers are used, that are included in the font as-well.

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Here is an example. Both lines have the same font with no variant (Regular), once with medieval numbers activated, the second wit the default lining numbers.

Answer 1

These are called lowercase numbers and can be turned on using UIFontDescriptor.

First, you need to import CoreText for some constants:

#import <CoreText/SFNTLayoutTypes.h>
or
@import CoreText.SFNTLayoutTypes;

Then create font using font descriptor. Here I use Georgia family:

NSDictionary *lowercaseNumbers = @{
                                   UIFontFeatureTypeIdentifierKey: @(kNumberCaseType),
                                   UIFontFeatureSelectorIdentifierKey: @(kLowerCaseNumbersSelector),
                                   };
UIFontDescriptor *descriptor = [[UIFontDescriptor alloc] initWithFontAttributes:
                                @{
                                  UIFontDescriptorFamilyAttribute: @"Georgia",
                                  UIFontDescriptorFeatureSettingsAttribute:@[ lowercaseNumbers ],
                                  }];
UIFont *font = [UIFont fontWithDescriptor:descriptor size:15];

Result:

Edit: As @Random832 pointed out, Georgia has only lowercase numbers, so the result is irrelevant. However, @vikingosegundo confirmed this code works on supported fonts. Thanks.

The top line was generated with

UIFont *font = [UIFont fontWithName:@"DIN Next LT Pro" size:12];
if (font)
    label.font = font;

the second line with

NSDictionary *lowercaseNumbers = @{  UIFontFeatureTypeIdentifierKey:@(kNumberCaseType), UIFontFeatureSelectorIdentifierKey: @(kLowerCaseNumbersSelector)};
UIFontDescriptor *descriptor = [[UIFontDescriptor alloc] initWithFontAttributes:
                                @{UIFontDescriptorFamilyAttribute: @"DIN Next LT Pro",UIFontDescriptorFeatureSettingsAttribute:@[ lowercaseNumbers ]}];
UIFont *font = [UIFont fontWithDescriptor:descriptor size:12];
if (font)
    label.font = font;