github.com/kintar/etxt@v0.0.9/examples/ebiten/typewriter/main.go

package main

import "os"
import "log"
import "fmt"
import "math"
import "time"
import "image"
import "image/color"
import "math/rand"
import "regexp"

import "github.com/hajimehoshi/ebiten/v2"
import "golang.org/x/image/math/fixed"

import "github.com/kintar/etxt"
import "github.com/kintar/etxt/emask"

const Text = "Hey, hey... are you \\i{there}?\\pause{}\n\nLately, \\#50CB78{color} has been fading out of this world. I don't know where did they send the \\b{original painter}, but the landscape doesn't \\shake{vibrate} quite the same anymore.\\pause{} I dreamed I'd be able to escape from these walls, \\#FFAAAA{resize} the \\#FF3300{virtual room} that tried to contain me for so long and allow my self-expression to continue expanding, but...\n\nThe ever \\bigger{in\\bigger{cr\\bigger{ea\\bigger{si\\bigger{ng}}}}} madness could get to any of us, anytime..\\pause{} We \\#AAAAAA{may not} have prepared properly for it, but it's \\b{\\b{ok}} now.\\pause{}\n\nI didn't give up so easily, though, and travelling through the desert I finally met \\i{\\b{the documentation \\#FF00FF{m}\\#00FFFF{a}\\#FFFF00{s}\\#80FF8F{t}\\#59B487{e}\\#FFC0CB{r}}}, who unveiled some of the secrets I was looking for... we could press \\b{\\b{\\bigger{R}}}, and then... maybe the world itself would vanish from our sights, starting anew in front of a different observer.\n\n\\pause{}An observer that believed to be the same as it always was.\\pause{}\\pause{} Hah.\\pause{}\\pause{} No chance."

// --- typewriter code ---

// - helper types -
const BasicPause = 4
const PeriodPause = 36
const CommaPause = 20
const ManualPause = 24

type FormatType int

const (
	FmtSize FormatType = iota
	FmtColor
	FmtBold
	FmtItalic
	FmtPause
	FmtShake
)

type FormatUndo struct {
	formatType FormatType
	data       uint64
}

var colorRegexp = regexp.MustCompile(`\A#([0-9A-F]{2})([0-9A-F]{2})([0-9A-F]{2})\z`)

const MaxFormatDepth = 16

// - actual typewriter type -
type Typewriter struct {
	renderer      *etxt.Renderer
	content       string
	maxIndex      int // how far we are into the display of `content`
	pause         int // how many pause updates are left before showing the next char
	minPauseIndex int // helper to allow manual pauses
	shaking       bool
	backtrack     [MaxFormatDepth]FormatUndo
}

func NewTypewriter(font *etxt.Font, size int, content string) *Typewriter {
	cache := etxt.NewDefaultCache(4 * 1024 * 1024) // 4MB cache
	fauxRast := emask.FauxRasterizer{}
	renderer := etxt.NewRenderer(&fauxRast)
	renderer.SetCacheHandler(cache.NewHandler())
	renderer.SetSizePx(size)
	renderer.SetFont(font)
	renderer.SetVertAlign(etxt.Top)
	return &Typewriter{
		renderer: renderer,
		content:  content,
		pause:    PeriodPause,
	}
}

func (self *Typewriter) Reset(content string) {
	self.content = content
	self.maxIndex = 0
	self.shaking = false
	self.pause = BasicPause
}

func (self *Typewriter) Update() {
	self.pause -= 1
	if self.pause <= 0 {
		self.pause = 0
		if self.maxIndex < len(self.content) {
			switch self.content[self.maxIndex] {
			case '.':
				self.pause = PeriodPause
			case '?':
				self.pause = PeriodPause
			case ',':
				self.pause = CommaPause
			default:
				self.pause = BasicPause
			}
			self.maxIndex += 1
		}
	}
}

func (self *Typewriter) Draw(target *ebiten.Image) {
	self.renderer.SetTarget(target)
	bounds := target.Bounds()
	feed := self.renderer.NewFeed(fixed.P(bounds.Min.X, bounds.Min.Y))

	index := 0
	formatDepth := 0
	atLineStart := false

	defer func() {
		for formatDepth > 0 {
			self.undoFormat(self.backtrack[formatDepth-1])
			formatDepth -= 1
		}
	}()

	for index < self.maxIndex {
		allowStop := true
		fragment, advance := self.nextFragment(index)

		switch fragment[0] {
		case '\\': // apply format
			undo := self.applyFormat(fragment, index)
			self.backtrack[formatDepth] = undo
			formatDepth += 1
			allowStop = false
		case '{': // open braces (only allowed for formats)
			// nothing, the style has already been applied
			allowStop = false
		case '}': // close braces (only allowed for formats)
			undo := self.backtrack[formatDepth-1]
			self.undoFormat(undo)
			formatDepth -= 1
		case ' ':
			if !atLineStart {
				feed.Advance(' ')
			}
		case '\n':
			feed.LineBreak()
			atLineStart = true
		default: // draw text
			// first measure it to see if it fits
			width := self.renderer.SelectionRect(fragment).Width
			if (feed.Position.X + width).Ceil() > bounds.Max.X {
				feed.LineBreak() // didn't fit, jump to next line
			}

			// abort if we are going beyond the proper text area
			if feed.Position.Y.Ceil() >= bounds.Max.Y {
				return
			}

			// draw each character individually
			for i, codePoint := range fragment {
				if index+i >= self.maxIndex {
					return
				}
				if self.shaking {
					preY := feed.Position.Y
					vibr := fixed.Int26_6(rand.Intn(96))
					if rand.Intn(2) == 0 {
						vibr = -vibr
					}
					feed.Position.Y += vibr
					feed.Draw(codePoint)
					feed.Position.Y = preY
				} else {
					feed.Draw(codePoint)
				}
			}
			atLineStart = false
		}

		index += advance
		if !allowStop {
			if index >= self.maxIndex && self.maxIndex < len(self.content) {
				self.maxIndex += 1
			}
		}
	}
}

// returns the next fragment and the byte advance
func (self *Typewriter) nextFragment(startIndex int) (string, int) {
	for byteIndex, codePoint := range self.content[startIndex:] {
		switch codePoint {
		case ' ', '\n', '{', '}':
			if byteIndex == 0 {
				return self.content[startIndex : startIndex+1], 1
			} else {
				return self.content[startIndex : startIndex+byteIndex], byteIndex
			}
		case '\\':
			if byteIndex > 0 {
				return self.content[startIndex : startIndex+byteIndex], byteIndex
			}
		}
	}
	return self.content[startIndex:], len(self.content) - startIndex
}

func (self *Typewriter) applyFormat(format string, index int) FormatUndo {
	if len(format) <= 0 {
		panic("invalid format with zero length")
	}
	if format[0] != '\\' {
		panic("formats must start with backslash, but got '" + format + "'")
	}
	format = format[1:]
	switch format {
	case "i", "italic", "italics":
		fauxRast := self.renderer.GetRasterizer().(*emask.FauxRasterizer)
		factor := fauxRast.GetSkewFactor()
		fauxRast.SetSkewFactor(factor + 0.22)
		return FormatUndo{FmtItalic, storeFloat64AsUint64(factor)}
	case "b", "bold":
		fauxRast := self.renderer.GetRasterizer().(*emask.FauxRasterizer)
		factor := fauxRast.GetExtraWidth()
		fauxRast.SetExtraWidth(factor + 1.0)
		return FormatUndo{FmtBold, storeFloat64AsUint64(factor)}
	case "shake":
		self.shaking = true
		return FormatUndo{FmtShake, 0}
	case "pause":
		if self.minPauseIndex <= index {
			self.pause = ManualPause
			self.minPauseIndex = index + 1
		}
		return FormatUndo{FmtPause, 0}
	case "bigger":
		size := self.renderer.GetSizePxFract()
		self.renderer.SetSizePxFract(size + 128)
		return FormatUndo{FmtSize, storeFix26_6AsUint64(size)}
		// note: if we were doing this right, we would have to compute
		//       the whole line in advance, pick the max height and
		//       adjust with that.
	case "smaller":
		size := self.renderer.GetSizePxFract()
		if size > (5 * 64) {
			self.renderer.SetSizePxFract(size - 128)
		}
		return FormatUndo{FmtSize, storeFix26_6AsUint64(size)}
	default:
		matches := colorRegexp.FindStringSubmatch(format)
		if matches == nil {
			panic("unexpected format '" + format + "'")
		}
		r := parseHexColor(matches[1])
		g := parseHexColor(matches[2])
		b := parseHexColor(matches[3])
		oldColor := self.renderer.GetColor().(color.RGBA)
		self.renderer.SetColor(color.RGBA{r, g, b, 255})
		return FormatUndo{FmtColor, storeRgbaAsUint64(oldColor)}
	}
}

func (self *Typewriter) undoFormat(undo FormatUndo) {
	switch undo.formatType {
	case FmtSize:
		self.renderer.SetSizePxFract(loadFix26_6FromUint64(undo.data))
	case FmtColor:
		self.renderer.SetColor(loadRgbaFromUint64(undo.data))
	case FmtBold:
		fauxRast := self.renderer.GetRasterizer().(*emask.FauxRasterizer)
		fauxRast.SetExtraWidth(loadFloat64FromUint64(undo.data))
	case FmtShake:
		self.shaking = false
	case FmtPause:
		// nothing to do for this one
	case FmtItalic:
		fauxRast := self.renderer.GetRasterizer().(*emask.FauxRasterizer)
		fauxRast.SetSkewFactor(loadFloat64FromUint64(undo.data))
		// note: if we were doing this right, we would probably want to
		//       consider adding some extra space after italics too in order
		//       to prevent clumping due to italicized portions
	default:
		panic("unexpected format type")
	}
}

// unsafe but fast, already checked with regexp
func parseHexColor(cc string) uint8 {
	return (runeDigit(cc[0]) << 4) + runeDigit(cc[1])
}

// unsafe but fast, already checked with regexp
func runeDigit(r uint8) uint8 {
	if r > '9' {
		return uint8(r) - 55
	}
	return uint8(r) - 48
}

func storeRgbaAsUint64(c color.RGBA) uint64 {
	var u uint64 = uint64(c.R)
	u = (u << 8) | uint64(c.G)
	u = (u << 8) | uint64(c.B)
	return (u << 8) | uint64(c.A)
}
func loadRgbaFromUint64(u uint64) color.RGBA {
	var c color.RGBA
	c.A = uint8(u & 0xFF)
	c.B = uint8((u >> 8) & 0xFF)
	c.G = uint8((u >> 16) & 0xFF)
	c.R = uint8((u >> 24) & 0xFF)
	return c
}
func storeFix26_6AsUint64(f fixed.Int26_6) uint64  { return uint64(uint32(f)) }
func loadFix26_6FromUint64(u uint64) fixed.Int26_6 { return fixed.Int26_6(uint32(u)) }
func storeFloat64AsUint64(f float64) uint64        { return math.Float64bits(f) }
func loadFloat64FromUint64(u uint64) float64       { return math.Float64frombits(u) }

// --- actual game ---

type Game struct{ typewriter *Typewriter }

func (self *Game) Layout(w int, h int) (int, int) { return w, h }
func (self *Game) Update() error {
	if ebiten.IsKeyPressed(ebiten.KeyR) {
		self.typewriter.Reset(Text)
	} else {
		self.typewriter.Update()
	}
	return nil
}

func (self *Game) Draw(screen *ebiten.Image) {
	// dark background
	screen.Fill(color.RGBA{0, 0, 20, 255})

	// determine positioning and draw
	w, h := screen.Size()
	area := image.Rect(16, 16, w-32, h-32)
	self.typewriter.Draw(screen.SubImage(area).(*ebiten.Image))
}

func main() {
	// seed rand
	rand.Seed(time.Now().UnixNano())

	// get font path
	if len(os.Args) != 2 {
		msg := "Usage: expects one argument with the path to the font to be used\n"
		fmt.Fprint(os.Stderr, msg)
		os.Exit(1)
	}

	// parse font
	font, fontName, err := etxt.ParseFontFrom(os.Args[1])
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Font loaded: %s\n", fontName)

	// run the game
	ebiten.SetWindowTitle("etxt/examples/ebiten/typewriter")
	ebiten.SetWindowSize(640, 480)
	ebiten.SetWindowResizable(true)
	err = ebiten.RunGame(&Game{NewTypewriter(font, 18, Text)})
	if err != nil {
		log.Fatal(err)
	}
}