#2: Implement Text demo

Demo/Demo.playground/Pages/Text.xcplaygroundpage/Contents.swift

@@ -0,0 +1,261 @@
+/*:
+ # Text
+
+ **Text** is a program which show various way of text showing.
+
+ ([Original example that uses LibHaru](https://github.com/libharu/libharu/wiki/Examples#text_democ))
+ */
+import SwiftyHaru
+import func Foundation.tan
+/*:
+ Firstly, we need to define some helper functions.
+ */
+let sampleTextShort  = "ABCabc123"
+let sampleTextLong   = "abcdefgABCDEFG123!#$%&+-@?"
+let sampleTextPhrase = "The quick brown fox jumps over the lazy dog."
+
+func showStripePattern(in context: DrawingContext, x: Float, y: Float) {
+
+    context.strokeColor = #colorLiteral(red: 0, green: 0, blue: 0.5, alpha: 1)
+    context.lineWidth = 1
+
+    for iy in stride(from: 0 as Float, to: 50, by: 3) {
+        context.stroke(
+            Path()
+                .moving(toX: x, y: y + iy)
+                .appendingLine(toX: x + context.textWidth(for: sampleTextShort), y: y + iy)
+        )
+    }
+
+    context.lineWidth = 2.5
+}
+
+func showDescription(in context: DrawingContext, x: Float, y: Float, text: String) throws {
+    let fontSize = context.fontSize
+    let fillColor = context.fillColor
+
+    context.fillColor = .black
+    context.textRenderingMode = .fill
+    context.fontSize = 10
+    try context.show(text: text, atX: x, y: y - 12)
+
+    context.fontSize = fontSize
+    context.fillColor = fillColor
+}
+/*:
+ Then we setup our document.
+ */
+let document = PDFDocument()
+let pageTitle = "Text Demo"
+
+try document.setCompressionMode(to: .all)
+
+try document.addPage() { context in
+
+/*:
+ Let's draw the grid for convenience.
+ */
+    let horizontalLabels = sequence(first: 50, next: { $0 + 50 }).lazy.map(String.init)
+    let verticalLabels = sequence(first: 10, next: { $0 + 10 }).lazy.map(String.init)
+
+    let labels = Grid.Labels(top: Grid.LabelParameters(sequence: "" + horizontalLabels,
+                                                       offset: Vector(dx: 0, dy: -6)),
+                             bottom: Grid.LabelParameters(sequence: "" + horizontalLabels,
+                                                          offset: Vector(dx: 0, dy: 6)),
+                             left: Grid.LabelParameters(sequence: "" + verticalLabels,
+                                                        frequency: 1,
+                                                        offset: Vector(dx: 6, dy: 0)))
+
+    let serifs = Grid.Serifs(top: .default,
+                             bottom: .default,
+                             left: Grid.SerifParameters(frequency: 1),
+                             right: nil)
+
+    let grid = Grid(width: context.page.width,
+                    height: context.page.height,
+                    labels: labels,
+                    serifs: serifs)
+    try context.draw(grid, position: .zero)
+
+/*:
+ Let's print the title of the page:
+ */
+
+    context.fontSize = 24
+    let textWidth = context.textWidth(for: pageTitle)
+    try context.show(text: pageTitle, atX: (context.page.width - textWidth) / 2, y: context.page.height - 50)
+/*:
+ We are now ready to place some text samples.
+ First, let's play with font size.
+ */
+    var textPosition = Point(x: 60, y: context.page.height - 60)
+
+    for fontSize in sequence(first: 8 as Float, next: { $0 * 1.5 }) {
+
+        if fontSize >= 60 {
+            break
+        }
+
+        context.fontSize = fontSize
+        textPosition.y -= 5 + fontSize
+
+        // Measure the number of characters which included in the page
+        let utf8Length = try context
+            .measureText(sampleTextLong, width: context.page.width - 120, wordwrap: false).utf8Length
+
+        try context.show(text: String(sampleTextLong.utf8.prefix(utf8Length))!, atPosition: textPosition)
+
+        // Print the description
+        textPosition.y -= 10
+        context.fontSize = 8
+        try context.show(text: String(format: "Fontsize=%.0f", fontSize), atPosition: textPosition)
+    }
+/*:
+ Then let's experiment with font color.
+ */
+    context.fontSize = 8
+    textPosition.y -= 30
+    try context.show(text: "Font color", atPosition: textPosition)
+
+    context.fontSize = 18
+    textPosition.y -= 20
+    for (i, char) in sampleTextLong.enumerated() {
+        let char = String(char)
+        let red = Float(i) / Float(sampleTextLong.utf8.count)
+        let green = 1 - red
+        context.fillColor = Color(red: red, green: green, blue: 0)!
+        try context.show(text: char, atPosition: textPosition)
+        textPosition.x += context.textWidth(for: char)
+    }
+
+    textPosition.x = 60
+    textPosition.y -= 25
+    for (i, char) in sampleTextLong.enumerated() {
+        let char = String(char)
+        let red = Float(i) / Float(sampleTextLong.utf8.count)
+        let blue = 1 - red
+        context.fillColor = Color(red: red, green: 0, blue: blue)!
+        try context.show(text: char, atPosition: textPosition)
+        textPosition.x += context.textWidth(for: char)
+    }
+
+    textPosition.x = 60
+    textPosition.y -= 25
+    for (i, char) in sampleTextLong.enumerated() {
+        let char = String(char)
+        let blue = Float(i) / Float(sampleTextLong.utf8.count)
+        let green = 1 - blue
+        context.fillColor = Color(red: 0, green: green, blue: blue)!
+        try context.show(text: char, atPosition: textPosition)
+        textPosition.x += context.textWidth(for: char)
+    }
+/*:
+ Explore different font rendering modes:
+ */
+    let ypos: Float = 450
+
+    context.fontSize = 32
+    context.fillColor = #colorLiteral(red: 0.5, green: 0.5, blue: 0, alpha: 1)
+    context.lineWidth
+
+    try showDescription(in: context, x: 60, y: ypos, text: "textRenderingMode = .fill")
+    context.textRenderingMode = .fill
+    try context.show(text: sampleTextShort, atX: 60, y: ypos)
+
+    try showDescription(in: context, x: 60, y: ypos - 50, text: "textRenderingMode = .stroke")
+    context.textRenderingMode = .stroke
+    try context.show(text: sampleTextShort, atX: 60, y: ypos - 50)
+
+    try showDescription(in: context, x: 60, y: ypos - 100, text: "textRenderingMode = .fillThenStroke")
+    context.textRenderingMode = .fillThenStroke
+    try context.show(text: sampleTextShort, atX: 60, y: ypos - 100)
+
+    try showDescription(in: context, x: 60, y: ypos - 150, text: "textRenderingMode = .fillClipping")
+    try context.withNewGState {
+        context.textRenderingMode = .fillClipping
+        try context.show(text: sampleTextShort, atX: 60, y: ypos - 150)
+        showStripePattern(in: context, x: 60, y: ypos - 150)
+    }
+
+    try showDescription(in: context, x: 60, y: ypos - 200, text: "textRenderingMode = .strokeClipping")
+    try context.withNewGState {
+        context.textRenderingMode = .strokeClipping
+        try context.show(text: sampleTextShort, atX: 60, y: ypos - 200)
+        showStripePattern(in: context, x: 60, y: ypos - 200)
+    }
+
+    try showDescription(in: context, x: 60, y: ypos - 250, text: "textRenderingMode = .fillStrokeClipping")
+    try context.withNewGState {
+        context.textRenderingMode = .fillStrokeClipping
+        try context.show(text: sampleTextShort, atX: 60, y: ypos - 250)
+        showStripePattern(in: context, x: 60, y: ypos - 250)
+    }
+
+/*:
+ Reset text attributes and try to transform text in different ways:
+ */
+    context.textRenderingMode = .fill
+    context.fillColor = .black
+    context.fontSize = 30
+
+    try showDescription(in: context, x: 320, y: ypos - 60, text: "Rotating text")
+    let rotatedTextPosition = Point(x: 330, y: ypos - 60)
+    let rotatedTextMatrix = AffineTransform(rotationAngle: .pi / 6) *
+        AffineTransform(translationX: rotatedTextPosition.x, y: rotatedTextPosition.y)
+    try context.show(text: sampleTextShort,
+                     atPosition: rotatedTextPosition,
+                     textMatrix: rotatedTextMatrix)
+
+    try showDescription(in: context, x: 320, y: ypos - 120, text: "Skewing text")
+    let skewedTextPosition = Point(x: 330, y: ypos - 120)
+    let skewedTextMatrix = AffineTransform(a:  1,                    b:  tan(.pi / 18),
+                                           c:  tan(.pi / 9),         d:  1,
+                                           tx: skewedTextPosition.x, ty: skewedTextPosition.y)
+    try context.show(text: sampleTextShort,
+                     atPosition: skewedTextPosition,
+                     textMatrix: skewedTextMatrix)
+
+    try showDescription(in: context, x: 320, y: ypos - 175, text: "Scaling text (X direction)")
+    let scaledXTextPosition = Point(x: 320, y: ypos - 175)
+    let scaledXTextMatrix = AffineTransform(scaleX: 1.5, y: 1) *
+        AffineTransform(translationX: scaledXTextPosition.x, y: scaledXTextPosition.y)
+    try context.show(text: sampleTextShort,
+                     atPosition: scaledXTextPosition,
+                     textMatrix: scaledXTextMatrix)
+
+    try showDescription(in: context, x: 320, y: ypos - 250, text: "Scaling text (Y direction)")
+    let scaledYTextPosition = Point(x: 320, y: ypos - 250)
+    let scaledYTextMatrix = AffineTransform(scaleX: 1, y: 2) *
+        AffineTransform(translationX: scaledYTextPosition.x, y: scaledYTextPosition.y)
+    try context.show(text: sampleTextShort,
+                     atPosition: scaledYTextPosition,
+                     textMatrix: scaledYTextMatrix)
+
+/*:
+ Alter character spacing and word spacing:
+ */
+
+    try showDescription(in: context, x: 60, y: 140, text: "char-spacing 0")
+    try showDescription(in: context, x: 60, y: 100, text: "char-spacing 1.5")
+    try showDescription(in: context, x: 60, y: 60,  text: "char-spacing 1.5, word-spacing 2.5")
+
+    context.fontSize = 20
+    context.fillColor = #colorLiteral(red: 0.1, green: 0.3, blue: 0.1, alpha: 1)
+
+    context.characterSpacing = 0
+    try context.show(text: sampleTextPhrase, atX: 60, y: 140)
+
+    context.characterSpacing = 1.5
+    try context.show(text: sampleTextPhrase, atX: 60, y: 100)
+
+    context.wordSpacing = 2.5
+    try context.show(text: sampleTextPhrase, atX: 60, y: 60)
+}
+
+/*:
+ We need to save our document.
+ */
+document.display()
+/*:
+ [Previous page](@previous) • **[Table of contents](Table%20of%20contents)** • [Next page](@next)
+ */

Demo/Demo.playground/contents.xcplayground

@@ -1,9 +1,10 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<playground version='6.0' target-platform='macos' display-mode='rendered'>
+<playground version='6.0' target-platform='macos' display-mode='raw'>
     <pages>
         <page name='Table of contents'/>
         <page name='Fonts'/>
         <page name='Lines'/>
+        <page name='Text'/>
         <page name='Arcs'/>
         <page name='TrueType Fonts'/>
         <page name='Grid Sheet'/>

Sources/SwiftyHaru/Graphics/Geometry.swift

@@ -100,6 +100,17 @@ public struct Point: Hashable {
     public static func +(lhs: Point, rhs: Vector) -> Point {
         return Point(x: lhs.x + rhs.dx, y: lhs.y + rhs.dy)
     }
+
+    /// Translates the `lhs` point by the specified `rhs` vector and stores the result in `lhs`.
+    ///
+    /// - Parameters:
+    ///   - lhs: The point to translate.
+    ///   - rhs: The difference vector.
+    @inlinable
+    public static func +=(lhs: inout Point, rhs: Vector) {
+        lhs.x += rhs.dx
+        lhs.y += rhs.dy
+    }
 
     /// Translates the `lhs` point by negation of the specified `rhs` vector.
     ///
@@ -112,6 +123,18 @@ public struct Point: Hashable {
         return Point(x: lhs.x - rhs.dx, y: lhs.y - rhs.dy)
     }
 
+    /// Translates the `lhs` point by negation of the specified `rhs` vector and stores the result
+    /// in `lhs`.
+    ///
+    /// - Parameters:
+    ///   - lhs: The point to translate.
+    ///   - rhs: The difference vector.
+    @inlinable
+    public static func -=(lhs: inout Point, rhs: Vector) {
+        lhs.x -= rhs.dx
+        lhs.y -= rhs.dy
+    }
+
     /// Returns the vector that needs to be added to `rhs` to get `lhs`.
     ///
     /// - Parameters: