Add display components 041-065; move Icon into display; QR via rsc.io/qr

display/qrcode.go

@@ -0,0 +1,75 @@
+package display
+
+import (
+	"fmt"
+
+	"github.com/egoist/mygo/ui"
+	"rsc.io/qr"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type QRCodeOptions struct {
+	// Scale is dots per module; zero means 2.
+	Scale int
+}
+
+type qrKey struct{}
+
+type qrCache struct {
+	text string
+	code *qr.Code
+}
+
+// QRCode encodes s at level M, with a quiet zone.
+func QRCode(c *ui.Context, s string, o QRCodeOptions) *ui.Element {
+	k := pixel.K(c)
+	sc := orDef("QRCode Scale", o.Scale, 2)
+	e := ui.Box(c)
+	qc := ui.Local(e, qrKey{}, func() qrCache { return qrCache{} })
+	if qc.code == nil || qc.text != s {
+		code, err := qr.Encode(s, qr.M)
+		if err != nil {
+			panic(fmt.Sprintf("display: QRCode %q: %v", s, err))
+		}
+		*qc = qrCache{s, code}
+	}
+	code := qc.code
+	n := (code.Size + 8) * sc
+	dark, light := extremes(k.Palette())
+	return e.Size(k.D(n), k.D(n)).Role(ui.RoleImage).Label(s).Draw(func(p *ui.Painter, r ui.Rect) {
+		g := k.Canvas(p, r)
+		g.Rect(0, 0, n, n, light)
+		for y := range code.Size {
+			for x := 0; x < code.Size; {
+				if !code.Black(x, y) {
+					x++
+					continue
+				}
+				end := x + 1
+				for end < code.Size && code.Black(end, y) {
+					end++
+				}
+				g.Rect((4+x)*sc, (4+y)*sc, (end-x)*sc, sc, dark)
+				x = end
+			}
+		}
+	})
+}
+
+// extremes are the darkest and lightest slots, for scanners.
+func extremes(pal *pixel.Palette) (dark, light pixel.Slot) {
+	lum := func(s pixel.Slot) int {
+		c := pal.Colors[s]
+		return 299*int(c.R) + 587*int(c.G) + 114*int(c.B)
+	}
+	for s := range pixel.Slot(pixel.Slots) {
+		if lum(s) < lum(dark) {
+			dark = s
+		}
+		if lum(s) > lum(light) {
+			light = s
+		}
+	}
+	return dark, light
+}