Add support for textcolor

Sources/SwiftMath/MathRender/MTMathList.swift

@@ -64,6 +64,7 @@ public enum MTMathAtomType: Int, CustomStringConvertible, Comparable {
     /// Denotes style changes during rendering.
     case style
     case color
+    case textcolor
     case colorBox
     
     // Atoms after this point are not part of TeX and do not have the usual structure.
@@ -106,6 +107,7 @@ public enum MTMathAtomType: Int, CustomStringConvertible, Comparable {
             case .space:          return "Space"
             case .style:          return "Style"
             case .color:          return "Color"
+            case .textcolor:      return "TextColor"
             case .colorBox:       return "Colorbox"
             case .table:          return "Table"
         }
@@ -235,6 +237,8 @@ public class MTMathAtom: NSObject {
                 return MTMathSpace(self as? MTMathSpace)
             case .color:
                 return MTMathColor(self as? MTMathColor)
+            case .textcolor:
+                return MTMathTextColor(self as? MTMathTextColor)
             case .colorBox:
                 return MTMathColorbox(self as? MTMathColorbox)
             case .table:
@@ -675,6 +679,38 @@ public class MTMathColor: MTMathAtom {
     }
 }
 
+// MARK: - MTMathTextColor
+/** An atom representing an textcolor element.
+ Note: None of the usual fields of the `MTMathAtom` apply even though this
+ class inherits from `MTMathAtom`. i.e. it is meaningless to have a value
+ in the nucleus, subscript or superscript fields. */
+public class MTMathTextColor: MTMathAtom {
+    public var colorString:String=""
+    public var innerList:MTMathList?
+
+    init(_ color: MTMathTextColor?) {
+        super.init(color)
+        self.type = .textcolor
+        self.colorString = color?.colorString ?? ""
+        self.innerList = MTMathList(color?.innerList)
+    }
+
+    override init() {
+        super.init()
+        self.type = .textcolor
+    }
+
+    public override var string: String {
+        "\\textcolor{\(self.colorString)}{\(self.innerList!.string)}"
+    }
+
+    override public var finalized: MTMathAtom {
+        let newColor = super.finalized as! MTMathTextColor
+        newColor.innerList = newColor.innerList?.finalized
+        return newColor
+    }
+}
+
 // MARK: - MTMathColorbox
 /** An atom representing an colorbox element.
  Note: None of the usual fields of the `MTMathAtom` apply even though this

Sources/SwiftMath/MathRender/MTMathListBuilder.swift

@@ -593,6 +593,12 @@ public struct MTMathListBuilder {
             mathColor.colorString = self.readColor()!
             mathColor.innerList = self.buildInternal(true)
             return mathColor
+        } else if command == "textcolor" {
+            // A textcolor command has 2 arguments
+            let mathColor = MTMathTextColor()
+            mathColor.colorString = self.readColor()!
+            mathColor.innerList = self.buildInternal(true)
+            return mathColor
         } else if command == "colorbox" {
             // A color command has 2 arguments
             let mathColorbox = MTMathColorbox()

Sources/SwiftMath/MathRender/MTTypesetter.swift

@@ -49,7 +49,7 @@ func getInterElementSpaces() -> [[InterElementSpaceType]] {
 // Get's the index for the given type. If row is true, the index is for the row (i.e. left element) otherwise it is for the column (right element)
 func getInterElementSpaceArrayIndexForType(_ type:MTMathAtomType, row:Bool) -> Int {
     switch type {
-        case .color, .colorBox, .ordinary, .placeholder:   // A placeholder is treated as ordinary
+        case .color, .textcolor, .colorBox, .ordinary, .placeholder:   // A placeholder is treated as ordinary
             return 0
         case .largeOperator:
             return 1
@@ -511,7 +511,37 @@ class MTTypesetter {
                     display!.position = currentPosition
                     currentPosition.x += display!.width
                     displayAtoms.append(display!)
-                    
+
+                case .textcolor:
+                    // stash the existing layout
+                    if currentLine.length > 0 {
+                        self.addDisplayLine()
+                    }
+                    let colorAtom = atom as! MTMathTextColor
+                    let display = MTTypesetter.createLineForMathList(colorAtom.innerList, font: font, style: style)
+                    display!.localTextColor = MTColor(fromHexString: colorAtom.colorString)
+
+                    if prevNode != nil {
+                        let subDisplay: MTDisplay = display!.subDisplays[0]
+                        let subDisplayAtom = (subDisplay as? MTCTLineDisplay)!.atoms[0]
+                        let interElementSpace = self.getInterElementSpace(prevNode!.type, right:subDisplayAtom.type)
+                        if currentLine.length > 0 {
+                            if interElementSpace > 0 {
+                                // add a kerning of that space to the previous character
+                                currentLine.addAttribute(kCTKernAttributeName as NSAttributedString.Key,
+                                                         value:NSNumber(floatLiteral: interElementSpace),
+                                                         range:currentLine.mutableString.rangeOfComposedCharacterSequence(at: currentLine.length-1))
+                            }
+                        } else {
+                            // increase the space
+                            currentPosition.x += interElementSpace
+                        }
+                    }
+
+                    display!.position = currentPosition
+                    currentPosition.x += display!.width
+                    displayAtoms.append(display!)
+
                 case .colorBox:
                     // stash the existing layout
                     if currentLine.length > 0 {