Add support for style of subscript.

Author: SergioEstevao

Aztec.xcodeproj/project.pbxproj

@@ -241,6 +241,8 @@
 		FF7EAEC4234D253B007A26E0 /* FontProvider.swift in Sources */ = {isa = PBXBuildFile; fileRef = FF7EAEC3234D253B007A26E0 /* FontProvider.swift */; };
 		FF94935E245738AC0085ABB3 /* SuperscriptStringAttributeConverter.swift in Sources */ = {isa = PBXBuildFile; fileRef = FF94935D245738AC0085ABB3 /* SuperscriptStringAttributeConverter.swift */; };
 		FF949360245740250085ABB3 /* SuperscriptFormatter.swift in Sources */ = {isa = PBXBuildFile; fileRef = FF94935F245740250085ABB3 /* SuperscriptFormatter.swift */; };
+		FF949362245744090085ABB3 /* SubscriptStringAttributeConverter.swift in Sources */ = {isa = PBXBuildFile; fileRef = FF949361245744090085ABB3 /* SubscriptStringAttributeConverter.swift */; };
+		FF949364245744560085ABB3 /* SubscriptFormatter.swift in Sources */ = {isa = PBXBuildFile; fileRef = FF949363245744560085ABB3 /* SubscriptFormatter.swift */; };
 		FFA61E891DF18F3D00B71BF6 /* ParagraphStyle.swift in Sources */ = {isa = PBXBuildFile; fileRef = FFA61E881DF18F3D00B71BF6 /* ParagraphStyle.swift */; };
 		FFA61EC21DF6C1C900B71BF6 /* NSAttributedString+Archive.swift in Sources */ = {isa = PBXBuildFile; fileRef = FFA61EC11DF6C1C900B71BF6 /* NSAttributedString+Archive.swift */; };
 		FFB5D29720BEB21A0038DCFB /* CiteFormatter.swift in Sources */ = {isa = PBXBuildFile; fileRef = FFB5D29620BEB21A0038DCFB /* CiteFormatter.swift */; };
@@ -527,6 +529,8 @@
 		FF7EAEC3234D253B007A26E0 /* FontProvider.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FontProvider.swift; sourceTree = "<group>"; };
 		FF94935D245738AC0085ABB3 /* SuperscriptStringAttributeConverter.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SuperscriptStringAttributeConverter.swift; sourceTree = "<group>"; };
 		FF94935F245740250085ABB3 /* SuperscriptFormatter.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SuperscriptFormatter.swift; sourceTree = "<group>"; };
+		FF949361245744090085ABB3 /* SubscriptStringAttributeConverter.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SubscriptStringAttributeConverter.swift; sourceTree = "<group>"; };
+		FF949363245744560085ABB3 /* SubscriptFormatter.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SubscriptFormatter.swift; sourceTree = "<group>"; };
 		FFA61E881DF18F3D00B71BF6 /* ParagraphStyle.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ParagraphStyle.swift; sourceTree = "<group>"; };
 		FFA61EC11DF6C1C900B71BF6 /* NSAttributedString+Archive.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "NSAttributedString+Archive.swift"; sourceTree = "<group>"; };
 		FFB5D29620BEB21A0038DCFB /* CiteFormatter.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CiteFormatter.swift; sourceTree = "<group>"; };
@@ -1009,6 +1013,7 @@
 				F12F58601EF20394008AE298 /* TextListFormatter.swift */,
 				F12F58611EF20394008AE298 /* UnderlineFormatter.swift */,
 				FF94935F245740250085ABB3 /* SuperscriptFormatter.swift */,
+				FF949363245744560085ABB3 /* SubscriptFormatter.swift */,
 				FF61909D202481F4004BCD0A /* CodeFormatter.swift */,
 				FFB5D29620BEB21A0038DCFB /* CiteFormatter.swift */,
 			);
@@ -1095,6 +1100,7 @@
 				F1656FDD2152A6A6009C7E3A /* CiteStringAttributeConverter.swift */,
 				F15BA60C215159A600424120 /* ItalicStringAttributeConverter.swift */,
 				FF94935D245738AC0085ABB3 /* SuperscriptStringAttributeConverter.swift */,
+				FF949361245744090085ABB3 /* SubscriptStringAttributeConverter.swift */,
 				F15BA60E21515C0F00424120 /* UnderlineStringAttributeConverter.swift */,
 			);
 			path = Implementations;
@@ -1637,6 +1643,7 @@
 				F11326B21EF1AA91007FEE9A /* HTMLPre.swift in Sources */,
 				F1098741214FF55F00983B6A /* BoldElementAttributeConverter.swift in Sources */,
 				F17BC8AB1F4E512800398E2B /* AttributedStringSerializer.swift in Sources */,
+				FF949364245744560085ABB3 /* SubscriptFormatter.swift in Sources */,
 				F18986E11EF2040A0060EDBA /* FontFormatter.swift in Sources */,
 				F1FF7D9D201A147B007B0B32 /* Figure.swift in Sources */,
 				FFA61E891DF18F3D00B71BF6 /* ParagraphStyle.swift in Sources */,
@@ -1645,6 +1652,7 @@
 				FF7C89B01E3BC52F000472A8 /* NSAttributedString+FontTraits.swift in Sources */,
 				B5E94D101FE01335000E7C20 /* FigureElementConverter.swift in Sources */,
 				40A2986D1FD61B0C00AEDF3B /* ElementConverter.swift in Sources */,
+				FF949362245744090085ABB3 /* SubscriptStringAttributeConverter.swift in Sources */,
 				F1FF7DA1201A1D3E007B0B32 /* FigcaptionElementConverter.swift in Sources */,
 				F9982CF621877663001E606B /* TextViewPasteboardDelegate.swift in Sources */,
 				F1289FB72155244A001E07C5 /* AttributeType.swift in Sources */,

Aztec/Classes/Converters/ElementsToAttributedString/Implementations/GenericElementConverter.swift

@@ -35,6 +35,7 @@ class GenericElementConverter: ElementConverter {
     lazy var codeFormatter = CodeFormatter()
     lazy var liFormatter = LiFormatter()
     lazy var superscriptFormatter = SuperscriptFormatter()
+    lazy var subscriptFormatter = SubscriptFormatter()
 
     public lazy var elementFormattersMap: [Element: AttributeFormatter] = {
         return [
@@ -58,6 +59,7 @@ class GenericElementConverter: ElementConverter {
             .code: self.codeFormatter,
             .li: self.liFormatter,
             .sup: self.superscriptFormatter,
+            .sub: self.subscriptFormatter,
         ]
     }()
 

Aztec/Classes/Converters/StringAttributesToAttributes/Implementations/SubscriptStringAttributeConverter.swift

@@ -0,0 +1,48 @@
+import Foundation
+import UIKit
+
+
+/// Converts the subscript style information from string attributes and aggregates it into an
+/// existing array of element nodes.
+///
+open class SubscriptStringAttributeConverter: StringAttributeConverter {
+    
+    private let toggler = HTMLStyleToggler(defaultElement: .sub, cssAttributeMatcher: NeverCSSAttributeMatcher())
+    
+    public func convert(
+        attributes: [NSAttributedString.Key: Any],
+        andAggregateWith elementNodes: [ElementNode]) -> [ElementNode] {
+        
+        var elementNodes = elementNodes
+        
+        // We add the representation right away, if it exists... as it could contain attributes beyond just this
+        // style.  The enable and disable methods below can modify this as necessary.
+        //
+        if let representation = attributes[NSAttributedString.Key.subHtmlRepresentation] as? HTMLRepresentation,
+            case let .element(representationElement) = representation.kind {
+            
+            elementNodes.append(representationElement.toElementNode())
+        }
+        
+        if shouldEnable(for: attributes) {
+            return toggler.enable(in: elementNodes)
+        } else {
+            return toggler.disable(in: elementNodes)
+        }
+    }
+
+    // MARK: - Style Detection
+
+    func shouldEnable(for attributes: [NSAttributedString.Key : Any]) -> Bool {
+        return hasTraits(for: attributes)
+    }
+    
+    func hasTraits(for attributes: [NSAttributedString.Key : Any]) -> Bool {
+        guard let baselineOffset = attributes[.baselineOffset] as? NSNumber else {
+                return false
+        }
+        
+        return baselineOffset.intValue < 0;
+    }
+}
+

Aztec/Classes/Formatters/Implementations/SubscriptFormatter.swift

@@ -0,0 +1,10 @@
+import UIKit
+
+class SubscriptFormatter: StandardAttributeFormatter {
+
+    init() {
+        super.init(attributeKey: .baselineOffset,
+                   attributeValue: NSNumber(-4),
+                   htmlRepresentationKey: .subHtmlRepresentation)
+    }
+}

Aztec/Classes/NSAttributedString/Conversions/AttributedStringParser.swift

@@ -28,6 +28,7 @@ class AttributedStringParser {
         ConditionalItalicStringAttributeConverter(),
         UnderlineStringAttributeConverter(),
         SuperscriptStringAttributeConverter(),
+        SubscriptStringAttributeConverter(),
     ]
 
     // MARK: - Attachment Converters