support em/ex units in root SVG size

DOM/Sources/DOM.swift

@@ -121,6 +121,8 @@ extension DOM {
         case millimeter
         case point
         case pica
+        case em
+        case ex
     }
 
     package enum Error: Swift.Error {
@@ -143,6 +145,10 @@ package extension DOM.Unit {
             return "pt"
         case .pica:
             return "pc"
+        case .em:
+            return "em"
+        case .ex:
+            return "ex"
         }
     }
 }
@@ -162,6 +168,8 @@ package extension Double {
             return self * 1.3333
         case .pica:
             return self * 16
+        case .em, .ex:
+            return self
         }
     }
 }

DOM/Sources/Parser.XML.SVG.swift

@@ -88,15 +88,26 @@ package extension XMLParser {
     func resolveRootDimension(_ raw: String?, viewport: DOM.Coordinate?, attribute: String) throws -> DOM.Coordinate? {
         guard let raw, !raw.isEmpty else { return nil }
         var scanner = XMLParser.Scanner(text: raw)
-        let value = try scanner.scanCoordinate()
+        scanner.scanner.currentIndex = scanner.currentIndex
+        guard let number = scanner.scanner.scanDoubleCompatibly() else {
+            throw Error.invalidAttribute(name: attribute, value: raw)
+        }
+        scanner.currentIndex = scanner.scanner.currentIndex
+
         if scanner.scanStringIfPossible("%") {
             guard let viewport else { return nil }
-            return value / 100 * viewport
+            return DOM.Coordinate(number / 100) * viewport
+        }
+        if let unit = scanner.scanUnit() {
+            guard scanner.isEOF else {
+                throw Error.invalidAttribute(name: attribute, value: raw)
+            }
+            return DOM.Coordinate(number.apply(unit: unit))
         }
         guard scanner.isEOF else {
             throw Error.invalidAttribute(name: attribute, value: raw)
         }
-        return value
+        return DOM.Coordinate(number)
     }
 
     func makeUnresolvedReason(attribute: String, raw: String?, hasViewBox: Bool) -> String {

DOM/Sources/Parser.XML.Scanner.swift

@@ -35,7 +35,7 @@ package extension XMLParser {
 
     struct Scanner {
 
-        private let scanner: Foundation.Scanner
+        package let scanner: Foundation.Scanner
         package var currentIndex: String.Index
 
         package init(text: String) {
@@ -256,7 +256,7 @@ package extension XMLParser {
 
         package mutating func scanDouble() throws -> Double {
             scanner.currentIndex = currentIndex
-            guard let val = scanner.scanDouble() else {
+            guard let val = scanner.scanDoubleCompatibly() else {
                 throw Error.invalid
             }
             currentIndex = scanner.currentIndex
@@ -285,6 +285,10 @@ package extension XMLParser {
                 return .point
             } else if scanUnit(.pica) {
                 return .pica
+            } else if scanUnit(.em) {
+                return .em
+            } else if scanUnit(.ex) {
+                return .ex
             } else {
                 return nil
             }
@@ -404,9 +408,42 @@ package extension Scanner {
         _ = scanCharacter()
         return scalar
     }
+
+    func scanDoubleCompatibly() -> Double? {
+        #if canImport(Darwin)
+        return scanDouble()
+        #else
+        let start = currentIndex
+        if let value = scanDouble() {
+            return value
+        }
+
+        currentIndex = start
+        let numeric = Foundation.CharacterSet(charactersIn: "+-0123456789.Ee")
+        guard let scannedNumber = scanCharacters(from: numeric), !scannedNumber.isEmpty else {
+            currentIndex = start
+            return nil
+        }
+
+        var numericEnd = currentIndex
+        var numericPrefix = scannedNumber
+        while Double(numericPrefix) == nil, !numericPrefix.isEmpty {
+            numericEnd = string.index(before: numericEnd)
+            numericPrefix.removeLast()
+        }
+
+        guard let value = Double(numericPrefix), !numericPrefix.isEmpty else {
+            currentIndex = start
+            return nil
+        }
+
+        currentIndex = numericEnd
+        return value
+        #endif
+    }
 
     func scanCoordinate() throws -> DOM.Coordinate {
-        guard let val = scanDouble() else { throw XMLParser.Error.invalid }
+        guard let val = scanDoubleCompatibly() else { throw XMLParser.Error.invalid }
         return DOM.Coordinate(val)
     }
 

DOM/Tests/Parser.SVGTests.swift

@@ -68,6 +68,29 @@ struct ParserSVGTests {
         #expect(parsed.height == 192)
     }
 
+    @Test
+    func root_em_ex_dimensions_fall_back_to_raw_values() throws {
+        let em = XML.Element(name: "svg", attributes: ["width": "2em", "height": "1em"])
+        let ex = XML.Element(name: "svg", attributes: ["width": "2ex", "height": "1ex"])
+        let parser = DOMXMLParser()
+
+        let parsedEm = try parser.parseSVG(em)
+        #expect(parsedEm.width == 2)
+        #expect(parsedEm.height == 1)
+
+        let parsedEx = try parser.parseSVG(ex)
+        #expect(parsedEx.width == 2)
+        #expect(parsedEx.height == 1)
+    }
+
+    @Test
+    func unknown_root_units_still_throw() {
+        let node = XML.Element(name: "svg", attributes: ["width": "2abc", "height": "1abc"])
+        #expect(throws: XMLParser.Error.self) {
+            try XMLParser().parseSVG(node)
+        }
+    }
+
     @Test
     func parseSVGInvalidNode() {
         let node = XML.Element(name: "svg2", attributes: ["width": "100", "height": "200"])

DOM/Tests/Parser.XML.PathTests.swift

@@ -62,6 +62,17 @@ struct ParserXMLPathTests {
         #expect(throws: (any Error).self) { _ = try scanner.scanCoordinate() }
     }
 
+    @Test
+    func scanCoordinate_FontUnitsFallBackToRawValues() throws {
+        let emScanner = XMLParser.PathScanner(string: "2em")
+        let exScanner = XMLParser.PathScanner(string: "3ex")
+
+        #expect(try emScanner.scanCoordinate() == 2.0)
+        #expect(emScanner.isAtEnd == false)
+        #expect(try exScanner.scanCoordinate() == 3.0)
+        #expect(exScanner.isAtEnd == false)
+    }
+
     @Test
     func equality() {
         #expect(Segment.move(x: 10, y: 20, space: .relative) == move(10, 20, .relative))

DOM/Tests/XML.Parser.ScannerTests.swift

@@ -134,9 +134,38 @@ struct ScannerTests {
         #expect(scanDouble("124") == 124)
         #expect(scanDouble(" 045") == 45)
         #expect(scanDouble("-29") == -29)
+        #expect(scanDouble("2em") == 2)
+        #expect(scanDouble(".5em") == 0.5)
         #expect(scanDouble("ab24") == nil)
     }
 
+    @Test
+    func foundationScanDouble_WithTrailingEmEx_IsPlatformDependent() {
+        let emScanner = Foundation.Scanner(string: "2em")
+        emScanner.charactersToBeSkipped = Foundation.CharacterSet.whitespacesAndNewlines
+
+        let exScanner = Foundation.Scanner(string: "2ex")
+        exScanner.charactersToBeSkipped = Foundation.CharacterSet.whitespacesAndNewlines
+
+        #if canImport(Darwin)
+        #expect(emScanner.scanDouble() == 2)
+        #expect(exScanner.scanDouble() == 2)
+        #else
+        #expect(emScanner.scanDouble() == nil)
+        #expect(exScanner.scanDouble() == nil)
+        #endif
+    }
+
+    @Test
+    func scanDoubleCompatibly_FallsBackForTrailingFontUnits() {
+        #expect(scanDoubleCompatibly("2em") == 2)
+        #expect(scanDoubleCompatibly("2ex") == 2)
+        #expect(scanDoubleCompatibly("2e") == 2)
+        #expect(scanDoubleCompatibly("2e+") == 2)
+        #expect(scanDoubleCompatibly(".5em") == 0.5)
+        #expect(scanDoubleCompatibly("ab24") == nil)
+    }
+
     @Test
     func scan_Length() {
         #expect(scanLength("0") == 0)
@@ -217,6 +246,13 @@ struct ScannerTests {
         #expect(try scanner.scanCoordinate() == 5 * 16)
     }
 
+    @Test
+    func scanCoordinate_FontUnitsFallBackToRawValues() {
+        #expect(parseCoordinate("2em") == 2)
+        #expect(parseCoordinate("2ex") == 2)
+        #expect(parseCoordinate(".5em") == 0.5)
+    }
+
     @Test
     func scanUpToPreservesStrings() throws {
         var scanner = XMLParser.Scanner(text: #"foo: bar; baz: "bing;bob" zab;"#)
@@ -289,6 +325,17 @@ private func scanDouble(_ text: String) -> Double? {
     return try? scanner.scanDouble()
 }
 
+private func scanDoubleCompatibly(_ text: String) -> Double? {
+    let scanner = Foundation.Scanner(string: text)
+    scanner.charactersToBeSkipped = Foundation.CharacterSet.whitespacesAndNewlines
+    return scanner.scanDoubleCompatibly()
+}
+
+private func parseCoordinate(_ text: String) -> DOM.Coordinate? {
+    var scanner = XMLParser.Scanner(text: text)
+    return try? scanner.scanCoordinate()
+}
+
 private func scanLength(_ text: String) -> DOM.Length? {
     var scanner = XMLParser.Scanner(text: text)
     return try? scanner.scanLength()

Examples/Sources/GalleryView.swift

@@ -55,6 +55,7 @@ struct GalleryView: View {
         "alert.svg",
         "effigy.svg",
         "d10.svg",
+        "mathjax-latex.svg",
         "stylesheet-multiple.svg"
     ]
 

SwiftDraw/Tests/SVGTests.swift

@@ -59,6 +59,21 @@ struct SVGTests {
         #expect(SVG(named: "missing.svg", in: .test) == nil)
     }
 
+    @Test
+    func root_em_ex_dimensions_parse_as_raw_values() {
+        let ex = #"<svg xmlns="http://www.w3.org/2000/svg" width="2ex" height="1ex"><rect width="5" height="5"/></svg>"#
+        let em = #"<svg xmlns="http://www.w3.org/2000/svg" width="2em" height="1em"><rect width="5" height="5"/></svg>"#
+        let px = #"<svg xmlns="http://www.w3.org/2000/svg" width="2px" height="1px"><rect width="5" height="5"/></svg>"#
+
+        let exSVG = SVG(data: Data(ex.utf8))
+        let emSVG = SVG(data: Data(em.utf8))
+        let pxSVG = SVG(data: Data(px.utf8))
+
+        #expect(exSVG?.size == CGSize(width: 2, height: 1))
+        #expect(emSVG?.size == CGSize(width: 2, height: 1))
+        #expect(pxSVG?.size == CGSize(width: 2, height: 1))
+    }
+
     @Test
     func imageRasterizes() {
         let image = SVG.makeLines()

docker-test.sh → container-run-tests.sh

@@ -1,5 +1,5 @@
-docker run -it \
+container run -it \
   --rm \
   --mount src="$(pwd)",target=/SwiftDraw,type=bind \
-  swift \
+  swift:6.3 \
   /usr/bin/swift test --package-path /SwiftDraw