add 07 guide code

guide/07_typing_text_on_the_screen/main.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"io/ioutil"
+	"os"
+	"time"
+
+	"github.com/faiface/pixel"
+	"github.com/faiface/pixel/pixelgl"
+	"github.com/faiface/pixel/text"
+	"github.com/golang/freetype/truetype"
+	"golang.org/x/image/colornames"
+	"golang.org/x/image/font"
+)
+
+func loadTTF(path string, size float64) (font.Face, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	bytes, err := ioutil.ReadAll(file)
+	if err != nil {
+		return nil, err
+	}
+
+	font, err := truetype.Parse(bytes)
+	if err != nil {
+		return nil, err
+	}
+
+	return truetype.NewFace(font, &truetype.Options{
+		Size:              size,
+		GlyphCacheEntries: 1,
+	}), nil
+}
+
+func run() {
+	cfg := pixelgl.WindowConfig{
+		Title:  "Pixel Rocks!",
+		Bounds: pixel.R(0, 0, 1024, 768),
+	}
+	win, err := pixelgl.NewWindow(cfg)
+	if err != nil {
+		panic(err)
+	}
+	win.SetSmooth(true)
+
+	face, err := loadTTF("intuitive.ttf", 80)
+	if err != nil {
+		panic(err)
+	}
+
+	atlas := text.NewAtlas(face, text.ASCII)
+	txt := text.New(pixel.V(50, 500), atlas)
+
+	txt.Color = colornames.Lightgrey
+
+	fps := time.Tick(time.Second / 120)
+
+	for !win.Closed() {
+		txt.WriteString(win.Typed())
+		if win.JustPressed(pixelgl.KeyEnter) || win.Repeated(pixelgl.KeyEnter) {
+			txt.WriteRune('\n')
+		}
+
+		win.Clear(colornames.Darkcyan)
+		txt.Draw(win, pixel.IM.Moved(win.Bounds().Center().Sub(txt.Bounds().Center())))
+		win.Update()
+
+		<-fps
+	}
+}
+
+func main() {
+	pixelgl.Run(run)
+}