Move NSAttributedString+NetNewsWire into Shared/Extensions

Shared/Extensions/NSAttributedString+NetNewsWire.swift

@@ -0,0 +1,134 @@
+//
+//  NSAttributedString+NetNewsWire.swift
+//  NetNewsWire
+//
+//  Created by Nate Weaver on 2020-04-07.
+//  Copyright © 2020 Ranchero Software. All rights reserved.
+//
+
+#if canImport(AppKit)
+import AppKit
+typealias Font = NSFont
+typealias FontDescriptor = NSFontDescriptor
+typealias Color = NSColor
+
+private let boldTrait = NSFontDescriptor.SymbolicTraits.bold
+private let italicTrait = NSFontDescriptor.SymbolicTraits.italic
+private let monoSpaceTrait = NSFontDescriptor.SymbolicTraits.monoSpace
+#else
+import UIKit
+typealias Font = UIFont
+typealias FontDescriptor = UIFontDescriptor
+typealias Color = UIColor
+
+private let boldTrait = UIFontDescriptor.SymbolicTraits.traitBold
+private let italicTrait = UIFontDescriptor.SymbolicTraits.traitItalic
+private let monoSpaceTrait = UIFontDescriptor.SymbolicTraits.traitMonoSpace
+#endif
+
+extension NSAttributedString {
+
+	/// Adds a font and color to an attributed string.
+	///
+	/// Additionally converts super-/subscript runs to super-/subscripted font variants
+	/// and converts bold text to heavy if the base font is semibold.
+	///
+	/// - Parameters:
+	///   - baseFont: The font to add.
+	///   - color: The color to add.
+	func adding(font baseFont: Font, color: Color? = nil) -> NSAttributedString {
+		let mutable = self.mutableCopy() as! NSMutableAttributedString
+		let fullRange = NSRange(location: 0, length: mutable.length)
+
+		if let color = color {
+			mutable.addAttribute(.foregroundColor, value: color as Any, range: fullRange)
+		}
+
+		let size = baseFont.pointSize
+		let baseDescriptor = baseFont.fontDescriptor
+		let baseSymbolicTraits = baseDescriptor.symbolicTraits
+
+		let baseTraits = baseDescriptor.object(forKey: .traits) as! [FontDescriptor.TraitKey: Any]
+		let baseWeight = baseTraits[.weight] as! Font.Weight
+
+		mutable.enumerateAttribute(.font, in: fullRange, options: []) { (font: Any?, range: NSRange, stop: UnsafeMutablePointer<ObjCBool>) in
+			guard let font = font as? Font else { return }
+
+			var newSymbolicTraits = baseSymbolicTraits
+
+			let symbolicTraits = font.fontDescriptor.symbolicTraits
+
+			if symbolicTraits.contains(italicTrait) {
+				newSymbolicTraits.insert(italicTrait)
+			}
+
+			if symbolicTraits.contains(monoSpaceTrait) {
+				newSymbolicTraits.insert(monoSpaceTrait)
+			}
+
+			#if canImport(AppKit)
+			var descriptor = baseDescriptor.withSymbolicTraits(newSymbolicTraits)
+			#else
+			var descriptor = baseDescriptor.withSymbolicTraits(newSymbolicTraits)!
+			#endif
+
+			if symbolicTraits.contains(boldTrait) {
+				// If the base font is semibold (as timeline titles are), make the "bold"
+				// text heavy for better contrast.
+
+				if baseWeight == .semibold {
+					let traits: [FontDescriptor.TraitKey: Any] = [.weight: Font.Weight.heavy]
+					let attributes: [FontDescriptor.AttributeName: Any] = [.traits: traits]
+					descriptor = descriptor.addingAttributes(attributes)
+				}
+			}
+
+			let newFont = Font(descriptor: descriptor, size: size)
+
+			mutable.addAttribute(.font, value: newFont as Any, range: range)
+		}
+
+		// make sup/sub smaller. `Key("NSSupeScript")` is used here because `.superscript`
+		// isn't defined in UIKit.
+		let superscriptAttribute = Key("NSSuperScript")
+
+		mutable.enumerateAttributes(in: fullRange, options: []) { (attributes: [Key : Any], range: NSRange, stop: UnsafeMutablePointer<ObjCBool>) in
+			guard let superscript = attributes[superscriptAttribute] as? Int else {
+				return
+			}
+
+			if superscript != 0 {
+				let font = mutable.attribute(.font, at: range.location, effectiveRange: nil) as! Font
+
+				// There's some discrepancy here: The raw value of AppKit's .typeIdentifier is UIKit's .featureIdentifier,
+				// and AppKit's .selectorIdentifier is UIKit's .typeIdentifier
+				#if canImport(AppKit)
+				let features: [FontDescriptor.FeatureKey: Any] = [.typeIdentifier: kVerticalPositionType, .selectorIdentifier: superscript > 0 ? kSuperiorsSelector : kInferiorsSelector]
+				#else
+				let features: [FontDescriptor.FeatureKey: Any] = [.featureIdentifier: kVerticalPositionType, .typeIdentifier: superscript > 0 ? kSuperiorsSelector : kInferiorsSelector]
+				#endif
+				let attributes: [FontDescriptor.AttributeName: Any] = [.featureSettings: [features]]
+				let descriptor = font.fontDescriptor.addingAttributes(attributes)
+
+				let newFont = Font(descriptor: descriptor, size: font.pointSize)
+
+				let newAttributes: [NSAttributedString.Key: Any] = [
+					.font: newFont as Any,
+					superscriptAttribute: 0,
+				]
+
+				mutable.addAttributes(newAttributes, range: range)
+			}
+		}
+
+		return mutable.copy() as! NSAttributedString
+	}
+
+	/// Creates an attributed string from HTML.
+	convenience init(html: String) {
+		let data = html.data(using: .utf8)!
+		let options: [NSAttributedString.DocumentReadingOptionKey: Any] = [.characterEncoding: String.Encoding.utf8.rawValue, .documentType: NSAttributedString.DocumentType.html]
+		try! self.init(data: data, options: options, documentAttributes: nil)
+	}
+
+}