Reputation: 851
This seems like it should be rudimentarily easy, but for whatever reason it's not working. I've read similar posts on SO and it seems like there might be an issue with the Font Traits dictionary? Is this an issue or am I just completely missing something? This is my first time messing around with fonts like this so I think it might be the latter.
I don't want to use the constants or supply a font with it's "-bold" variant. I would like to have fine grain control over the font weight.
let traits = [UIFontWeightTrait : 1.0]
imgFontDescriptor = UIFontDescriptor(fontAttributes: [UIFontDescriptorNameAttribute: "Helvetica"])
imgFontDescriptor = imgFontDescriptor.fontDescriptorByAddingAttributes([UIFontDescriptorTraitsAttribute:traits])
imgTextFont = UIFont(descriptor: imgFontDescriptor!, size: 24.0)
Research:
According to the iOS docs using a number value should work (I'm running iOS 9.2):
UIFontWeightTrait
The normalized weight value as an NSNumber object. The valid value range is from -1.0 to 1.0. The value of 0.0 corresponds to the regular or medium font weight. You can also use a font weight constant to specify a particular weight; for a list of constants you can use, see Font Weights. Available in iOS 7.0 and later.
Upvotes: 19
Views: 23310
Reputation: 1537
A concise extension:
extension UIFont {
/// Returns a new font with the weight specified.
/// - Parameter weight: The new font weight
func withWeight(_ weight: UIFont.Weight) -> UIFont {
let newDescriptor = fontDescriptor.addingAttributes([.traits: [
UIFontDescriptor.TraitKey.weight: weight]
])
return UIFont(descriptor: newDescriptor, size: pointSize)
}
}
Upvotes: 9
Reputation: 1286
Based on the Answers by. @pkamb and @Honghao Zhang
You can update font weight only using the following extension
public extension UIFont {
/// Returns a new font with the weight specified
///
/// - Parameter weight: The new font weight
func fontWeight(_ weight: UIFont.Weight) -> UIFont {
let fontDescriptor = UIFontDescriptor(fontAttributes: [
UIFontDescriptor.AttributeName.size: pointSize,
UIFontDescriptor.AttributeName.family: familyName
])
// Add the font weight to the descriptor
let weightedFontDescriptor = fontDescriptor.addingAttributes([
UIFontDescriptor.AttributeName.traits: [
UIFontDescriptor.TraitKey.weight: weight
]
])
return UIFont(descriptor: weightedFontDescriptor, size: 0)
}
}
Can be used by
UIFont.body.fontWeight(.light)
This is to match the new SwiftUI APIs naming https://developer.apple.com/documentation/swiftui/text/fontweight(_:)
Upvotes: 2
Reputation: 2513
UIFont(descriptor: imgFontDescriptor!, size: 24.0)
is returning a Font what match with the descriptor. If it can't find a Font match with your description, it returns a default font. Therefore, you can't control your weight manually. It depends on the Font you use. If the Font is support that weight, it will return that.
One more thing, you should use [UIFontDescriptorFamilyAttribute: "Helvetica"]
. So it will determine FontName base on FamilyName & your FontWeight.
The correct way is use the constant from Apple lib:
public let UIFontWeightUltraLight: CGFloat
@available(iOS 8.2, *)
public let UIFontWeightThin: CGFloat
@available(iOS 8.2, *)
public let UIFontWeightLight: CGFloat
@available(iOS 8.2, *)
public let UIFontWeightRegular: CGFloat
@available(iOS 8.2, *)
public let UIFontWeightMedium: CGFloat
@available(iOS 8.2, *)
public let UIFontWeightSemibold: CGFloat
@available(iOS 8.2, *)
public let UIFontWeightBold: CGFloat
@available(iOS 8.2, *)
public let UIFontWeightHeavy: CGFloat
@available(iOS 8.2, *)
public let UIFontWeightBlack: CGFloat*/
You should use http://iosfonts.com/ to determine which font weight that family name is supporting.
In case of Helvetica:
let traits = [UIFontWeightTrait: UIFontWeightLight] // UIFontWeightBold / UIFontWeightRegular
let imgFontDescriptor = UIFontDescriptor(fontAttributes: [UIFontDescriptorFamilyAttribute: "Helvetica"])
imgFontDescriptor = imgFontDescriptor.fontDescriptorByAddingAttributes([UIFontDescriptorTraitsAttribute: traits])
Upvotes: 16
Reputation: 35062
Here is Apple's own extension from UIFont+Extensions.swift
in their CareKit framework:
https://github.com/carekit-apple/CareKit/
extension UIFont {
static func preferredCustomFont(forTextStyle textStyle: TextStyle, weight: Weight) -> UIFont {
let defaultDescriptor = UIFontDescriptor.preferredFontDescriptor(withTextStyle: textStyle)
let size = defaultDescriptor.pointSize
let fontDescriptor = UIFontDescriptor(fontAttributes: [
UIFontDescriptor.AttributeName.size: size,
UIFontDescriptor.AttributeName.family: UIFont.systemFont(ofSize: size).familyName
])
// Add the font weight to the descriptor
let weightedFontDescriptor = fontDescriptor.addingAttributes([
UIFontDescriptor.AttributeName.traits: [
UIFontDescriptor.TraitKey.weight: weight
]
])
return UIFont(descriptor: weightedFontDescriptor, size: 0)
}
}
Upvotes: 6
Reputation: 9141
With Swift 4.1, simply do something like this:
var descriptor = UIFontDescriptor(name: "Helvetica Neue", size: 24.0)
descriptor = descriptor.addingAttributes([UIFontDescriptor.AttributeName.traits : [UIFontDescriptor.TraitKey.weight : UIFont.Weight.light]])
let font = UIFont(descriptor: descriptor, size: 24.0)
Upvotes: 14
Reputation: 551
If you use existing fontDescriptor (for example from existing font), it may not working, because of explicit '.name' attribute in fontDescriptor.fontAttributes.
Solution, that works for me (Swift 4):
extension UIFont {
var bold: UIFont { return withWeight(.bold) }
var semibold: UIFont { return withWeight(.semibold) }
private func withWeight(_ weight: UIFont.Weight) -> UIFont {
var attributes = fontDescriptor.fontAttributes
var traits = (attributes[.traits] as? [UIFontDescriptor.TraitKey: Any]) ?? [:]
traits[.weight] = weight
attributes[.name] = nil
attributes[.traits] = traits
attributes[.family] = familyName
let descriptor = UIFontDescriptor(fontAttributes: attributes)
return UIFont(descriptor: descriptor, size: pointSize)
}
}
Usage:
let baseFont = UIFont(name: "American Typewriter", size: 20)!
let boldFont = baseFont.bold
let semibold = baseFont.semibold
Upvotes: 29