Add a custom HTML -> NSAttributedString initializer

Shared/Extensions/NSAttributedString+NetNewsWire.swift

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+//
+//  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.
+	///
+	/// - 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
+
+			newSymbolicTraits.insert(symbolicTraits)
+
+			var descriptor = baseDescriptor.addingAttributes(font.fontDescriptor.fontAttributes)
+
+			#if canImport(AppKit)
+			descriptor = descriptor.withSymbolicTraits(newSymbolicTraits)
+			#else
+			var descriptor = descriptor.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)
+		}
+
+		return mutable.copy() as! NSAttributedString
+	}
+
+	/// Creates an attributed string from HTML.
+
+	private enum InTag {
+		case none
+		case opening
+		case closing
+	}
+
+	private enum Style {
+		case bold
+		case italic
+		case superscript
+		case `subscript`
+		case underline
+		case strikethrough
+		case monospace
+
+		init?(tag: String) {
+			switch tag {
+				case "b", "strong":
+					self = .bold
+				case "i", "em", "cite":
+					self = .italic
+				case "sup":
+					self = .superscript
+				case "sub":
+					self = .subscript
+				case "u", "ins":
+					self = .underline
+				case "s", "del":
+					self = .strikethrough
+				case "code", "samp", "tt", "kbd":
+					self = .monospace
+				default:
+					return nil
+			}
+		}
+	}
+
+	private static func decode(entity: String) -> String {
+		// TODO: Support all named entities
+
+		guard entity.hasPrefix("&"), entity.hasSuffix(";") else { return entity }
+
+		let name = entity.dropFirst().dropLast()
+
+		if name.hasPrefix("#") {
+			let value = name.dropFirst()
+			var number: Int? = nil
+
+			if value.hasPrefix("x") {
+				number = Int(value.dropFirst(), radix: 16)
+			} else {
+				number = Int(value)
+			}
+
+			if let number = number, let c = UnicodeScalar(number) {
+				return String(c)
+			}
+		} else {
+			switch name {
+				case "lt":
+					return "<"
+				case "gt":
+					return ">"
+				case "amp":
+					return "&"
+				case "quot":
+					return "\""
+				case "apos":
+					return "'"
+				default:
+					break
+			}
+		}
+
+		return entity
+	}
+
+	/// Returns an attributed string initialized from  HTML text containing basic inline stylistic tags.
+	///
+	/// - Parameters:
+	///   - html: The HTML text.
+	///   - font: The font to use. Defaults to the system font.
+	///   - locale: The locale used for quotation marks when parsing `<q>` tags.
+	convenience init(html: String, font: Font? = nil, locale: Locale = Locale.current) {
+		let baseFont = font ?? Font.systemFont(ofSize: Font.systemFontSize)
+
+		var inTag: InTag = .none
+		var tagBuf = ""
+		var tagStack = [String]()
+		var currentStyles: Set<Style> = []
+
+		var iterator = html.makeIterator()
+
+		let result = NSMutableAttributedString()
+
+		var attributeRanges = [(range: NSRange, styles: Set<Style>)]()
+
+		while let char = iterator.next() {
+			if char == "<" && inTag == .none {
+				tagBuf.removeAll()
+
+				guard let first = iterator.next() else { break }
+
+				if first == "/" {
+					inTag = .closing
+				} else {
+					inTag = .opening
+					tagBuf.append(first)
+				}
+			} else if char == ">" && inTag != .none {
+				if inTag == .opening {
+					tagStack.append(tagBuf)
+
+					if tagBuf == "q" {
+						result.mutableString.append(locale.quotationBeginDelimiter ?? "\"")
+					}
+
+					let lastRange = attributeRanges.last?.range
+					let location = lastRange != nil ? lastRange!.location + lastRange!.length : 0
+					let range = NSRange(location: location, length: result.mutableString.length - location)
+
+					let style = Style(tag: tagBuf)
+
+					attributeRanges.append( (range: range, styles: currentStyles) )
+
+					if style != nil {
+						currentStyles.insert(style!)
+					}
+
+
+				} else {
+					if tagBuf == "q" {
+						result.mutableString.append(locale.quotationEndDelimiter ?? "\"")
+					}
+
+					let lastRange = attributeRanges.last?.range
+					let location = lastRange != nil ? lastRange!.location + lastRange!.length : 0
+					let range = NSRange(location: location, length: result.mutableString.length - location)
+
+					attributeRanges.append( ( range: range, styles: currentStyles ))
+
+					if let style = Style(tag: tagBuf) {
+						currentStyles.remove(style)
+					}
+
+					let _ = tagStack.popLast() // TODO: Handle improperly-nested tags
+				}
+
+				inTag = .none
+			} else if inTag != .none {
+				tagBuf.append(char)
+			} else {
+				if char == "&" {
+					var entity = "&"
+					var lastchar: Character? = nil
+
+					while let entitychar = iterator.next() {
+						if entitychar.isWhitespace {
+							lastchar = entitychar
+							break;
+						}
+
+						entity.append(entitychar)
+
+						if (entitychar == ";") { break }
+					}
+
+
+					result.mutableString.append(Self.decode(entity: entity))
+
+					if let lastchar = lastchar { result.mutableString.append(String(lastchar)) }
+				} else {
+					result.mutableString.append(String(char))
+				}
+			}
+		}
+
+		result.addAttribute(.font, value: baseFont, range: NSRange(location: 0, length: result.length))
+
+		for (range, styles) in attributeRanges {
+			let currentFont = result.attribute(.font, at: range.location, effectiveRange: nil) as! Font
+			let currentDescriptor = currentFont.fontDescriptor
+			var descriptor = currentDescriptor.copy() as! FontDescriptor
+
+			var attributes: [NSAttributedString.Key: Any] = [:]
+
+			if styles.contains(.bold) {
+				let traits: [FontDescriptor.TraitKey: Any] = [.weight: Font.Weight.bold]
+				let descriptorAttributes: [FontDescriptor.AttributeName: Any] = [.traits: traits]
+				descriptor = descriptor.addingAttributes(descriptorAttributes)
+			}
+
+			if styles.contains(.italic) {
+				var symbolicTraits = currentDescriptor.symbolicTraits
+				symbolicTraits.insert(.italic)
+				descriptor = descriptor.withSymbolicTraits(symbolicTraits)
+			}
+
+			if styles.contains(.monospace) {
+				var symbolicTraits = currentDescriptor.symbolicTraits
+				symbolicTraits.insert(.monoSpace)
+				descriptor = descriptor.withSymbolicTraits(symbolicTraits)
+			}
+
+			if styles.contains(.superscript) {
+				#if canImport(AppKit)
+				let features: [FontDescriptor.FeatureKey: Any] = [.typeIdentifier: kVerticalPositionType, .selectorIdentifier: kSuperiorsSelector]
+				#else
+				let features: [FontDescriptor.FeatureKey: Any] = [.featureIdentifier: kVerticalPositionType, .typeIdentifier: kSuperiorsSelector]
+				#endif
+				let descriptorAttributes: [FontDescriptor.AttributeName: Any] = [.featureSettings: [features]]
+				descriptor = descriptor.addingAttributes(descriptorAttributes)
+			}
+
+			if styles.contains(.subscript) {
+				#if canImport(AppKit)
+				let features: [FontDescriptor.FeatureKey: Any] = [.typeIdentifier: kVerticalPositionType, .selectorIdentifier: kInferiorsSelector]
+				#else
+				let features: [FontDescriptor.FeatureKey: Any] = [.featureIdentifier: kVerticalPositionType, .typeIdentifier: kInferiorsSelector]
+				#endif
+				let descriptorAttributes: [FontDescriptor.AttributeName: Any] = [.featureSettings: [features]]
+				descriptor = currentDescriptor.addingAttributes(descriptorAttributes)
+			}
+
+			attributes[.font] = Font(descriptor: descriptor, size: baseFont.pointSize)
+
+			if styles.contains(.strikethrough) {
+				attributes[.strikethroughStyle] = NSUnderlineStyle.single.rawValue
+			}
+
+			if styles.contains(.underline) {
+				attributes[.underlineStyle] = NSUnderlineStyle.single.rawValue
+			}
+
+			result.addAttributes(attributes, range: range)
+		}
+
+		self.init(attributedString: result)
+	}
+
+}

submodules/RSCore

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-Subproject commit 0ba28167babdd4710adc1764ed49979c9eb42ead
+Subproject commit 3dfa570a4600690290cd946b8e122b0b99da0a13

submodules/RSDatabase

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-Subproject commit 0a8718c5c412585141d8374ae01b1e9e75dd1019
+Subproject commit de7753914c4f47aa97adfbe7a121acf0d2f8cd40

submodules/RSParser

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-Subproject commit 8c035b26767e66f5639c2fc0f3398216a46cb3d1
+Subproject commit fcbd9a34ecd8c080c6f26798a4b22ea0c98d8e74

submodules/RSTree

@@ -1 +1 @@
-Subproject commit 81011808b6c4242cbf95cb55120f250c157d594c
+Subproject commit 2fc9b9cff60032a272303ff6d6df5b39ec297179

submodules/RSWeb

@@ -1 +1 @@
-Subproject commit 7af4393f575479d249b83e7761a59d14b6c170d0
+Subproject commit 05388e4f7073b014f786cfce18782c3d61f8e378