Open Radar

 
Summary:
When automatic diagonal fraction is enabled for a UIFont, the displayed text looks broken when system language is set to Chinese or Japanese.
Tested in UILabel and UIButton on iOS 9.1

Steps to Reproduce:
set font of UILabel or UIButton to a UIFont with kDiagonalFractionsSelector enabled:

(see attached project)
sample code:
let systemFontDesc = UIFont.systemFontOfSize(28, weight: UIFontWeightLight).fontDescriptor()
let fractionFontDesc = systemFontDesc.fontDescriptorByAddingAttributes(
			[ UIFontDescriptorFeatureSettingsAttribute: [
				[ UIFontFeatureTypeIdentifierKey: kFractionsType,
					UIFontFeatureSelectorIdentifierKey: kDiagonalFractionsSelector]]])
let diagonalFont = UIFont(descriptor: fractionFontDesc, size:28)
label.font = diagonalFont

then set label.text = "11/22"

run the code on iOS with system language set to Chinese or Japanese

Expected Results:
displayed text should automatically have proper diagonal fraction form, in 11/22, 11 should be superscript, 22 should be subscript, kerning should be adjusted, special diagonal glyph is used.

Actual Results:
(see attached screenshot)
when language is set to Chinese or Japanese, all numbers are in superscript in the fraction, kerning is incorrect, too wide. Normal diagonal glyph is used.