support dominant-baseline

DOM/Sources/DOM.PresentationAttributes.swift

@@ -55,6 +55,7 @@ package extension DOM {
         package var fontFamily: [DOM.FontFamily]?
         package var fontSize: Float?
         package var textAnchor: TextAnchor?
+        package var dominantBaseline: TextBaseline?
 
         package var transform: [DOM.Transform]?
         package var clipPath: DOM.URL?
@@ -133,7 +134,8 @@ extension DOM.PresentationAttributes {
         merged.fontFamily = att.fontFamily ?? fontFamily
         merged.fontSize = att.fontSize ?? fontSize
         merged.textAnchor = att.textAnchor ?? textAnchor
-
+        merged.dominantBaseline = att.dominantBaseline ?? dominantBaseline
+
         merged.transform = att.transform ?? transform
         merged.clipPath = att.clipPath ?? clipPath
         merged.clipRule = att.clipRule ?? clipRule

DOM/Sources/DOM.swift

@@ -96,6 +96,14 @@ extension DOM {
         case end
     }
 
+    package enum TextBaseline: String {
+        case auto
+        case middle
+        case central
+        case hanging
+        case alphabetic
+    }
+
     package enum Transform: Equatable {
         case matrix(a: Float, b: Float, c: Float, d: Float, e: Float, f: Float)
         case translate(tx: Float, ty: Float)

DOM/Sources/Parser.XML.Element.swift

@@ -250,10 +250,10 @@ extension XMLParser {
         el.fillOpacity = try att.parsePercentage("fill-opacity")
         el.fillRule = try att.parseRaw("fill-rule")
 
-
         el.fontFamily = try att.parseFontFamily("font-family")
         el.fontSize = try att.parseFloat("font-size")
         el.textAnchor = try att.parseRaw("text-anchor")
+        el.dominantBaseline = try att.parseRaw("dominant-baseline")
 
         if let val = try? att.parseString("transform") {
             el.transform = try parseTransform(val)

DOM/Tests/Parser.XML.TextTests.swift

@@ -45,6 +45,7 @@ struct ParserXMLTextTests {
         el.attributes["font-family"] = "'Futura', sans-serif"
         el.attributes["font-size"] = "12.5"
         el.attributes["text-anchor"] = "end"
+        el.attributes["dominant-baseline"] = "central"
 
         let parsed = try XMLParser().parseGraphicsElement(el) as? DOM.Text
         let text = try #require(parsed)
@@ -55,6 +56,7 @@ struct ParserXMLTextTests {
         #expect(text.attributes.fontFamily == [.name("Futura"), .keyword(.sansSerif)])
         #expect(text.attributes.fontSize == 12.5)
         #expect(text.attributes.textAnchor == .end)
+        #expect(text.attributes.dominantBaseline == .central)
     }
 
     @Test

SwiftDraw/Sources/LayerTree/LayerTree.Builder.Layer.swift

@@ -67,8 +67,10 @@ extension LayerTree.Builder {
         }
         att.size = text.attributes.fontSize ?? att.size
         att.anchor = text.attributes.textAnchor ?? att.anchor
-        let offset = Self.makeXOffset(for: text.value, with: att)
-        point.x += offset
+        let offset = Self.makeOffset(for: text.value, with: att)
+        point.x += offset.width
+        point.y += offset.height
+
         return .text(text.value, point, att)
     }
 

SwiftDraw/Sources/LayerTree/LayerTree.Builder.Text.swift

@@ -40,11 +40,18 @@ import CoreText
 extension LayerTree.Builder {
 
 #if canImport(CoreText)
-    static func makeXOffset(for text: String, with attributes: LayerTree.TextAttributes) -> LayerTree.Float {
+    static func makeOffset(for text: String, with attributes: LayerTree.TextAttributes) -> LayerTree.Size {
         let font = CGProvider.createCTFont(for: attributes.font, size: attributes.size)
         let line = text.toLine(font: font)
+        return LayerTree.Size(
+            makeXOffset(line: line, anchor: attributes.anchor),
+            makeYOffset(font: font, baseline: attributes.baseline)
+        )
+    }
+
+    static func makeXOffset(line: CTLine, anchor: DOM.TextAnchor) -> LayerTree.Float {
         let width = CTLineGetTypographicBounds(line, nil, nil, nil)
-        switch attributes.anchor {
+        switch anchor {
         case .start:
            return 0
         case .middle:
@@ -53,13 +60,29 @@ extension LayerTree.Builder {
             return LayerTree.Float(-width)
         }
     }
+
+    static func makeYOffset(font: CTFont, baseline: DOM.TextBaseline) -> LayerTree.Float {
+        let ascent = CTFontGetAscent(font)
+        let descent = CTFontGetDescent(font)
+        let emHeight = ascent + descent
+        switch baseline {
+        case .central:
+            return LayerTree.Float(-(emHeight / 2 - ascent))
+        case .alphabetic, .auto:
+            return 0
+        case .hanging:
+            return LayerTree.Float(-ascent)
+        case .middle:
+            let xHeight = CTFontGetXHeight(font)
+            return LayerTree.Float(-(xHeight / 2 - ascent))
+        }
+    }
 #else
-    static func makeXOffset(for text: String, with attributes: LayerTree.TextAttributes) -> LayerTree.Float {
-        return 0
+    static func makeOffset(for text: String, with attributes: LayerTree.TextAttributes) -> LayerTree.Size {
+        return .zero
     }
 #endif
 
-
 }
 
 extension DOM.FontFamily {

SwiftDraw/Sources/LayerTree/LayerTree.Builder.swift

@@ -287,7 +287,8 @@ extension LayerTree.Builder {
             color: fill,
             font: state.fontFamily.flatMap(makeFonts),
             size: state.fontSize,
-            anchor: state.textAnchor
+            anchor: state.textAnchor,
+            baseline: state.textBaseline
         )
     }
 
@@ -449,6 +450,7 @@ extension LayerTree.Builder {
         var fontFamily: [DOM.FontFamily]
         var fontSize: DOM.Float
         var textAnchor: DOM.TextAnchor
+        var textBaseline: DOM.TextBaseline
 
         init() {
             //default root SVG element state
@@ -468,6 +470,7 @@ extension LayerTree.Builder {
             fillOpacity = 1.0
             fillRule = .nonzero
             textAnchor = .start
+            textBaseline = .auto
 
             fontFamily = [.name("Helvetica")]
             fontSize = 12.0
@@ -502,6 +505,7 @@ extension LayerTree.Builder {
         state.fontFamily = attributes.fontFamily ?? existing.fontFamily
         state.fontSize = attributes.fontSize ?? existing.fontSize
         state.textAnchor = attributes.textAnchor ?? existing.textAnchor
+        state.textBaseline = attributes.dominantBaseline ?? existing.textBaseline
 
         return state
     }

SwiftDraw/Sources/LayerTree/LayerTree.Layer.swift

@@ -154,6 +154,7 @@ extension LayerTree {
         var font: [Font]
         var size: Float
         var anchor: DOM.TextAnchor
+        var baseline: DOM.TextBaseline
 
         enum Font: Hashable {
             case truetype(Data)

SwiftDraw/Tests/LayerTree/LayerTree.LayerTests.swift

@@ -103,7 +103,8 @@ extension LayerTree.TextAttributes {
             color: .black,
             font: [.name("Times New Roman")],
             size: 12.0,
-            anchor: .start
+            anchor: .start,
+            baseline: .auto
         )
     }
 }