Add text components 021-040 with demos and behavior tests

text/scrambletext.go

@@ -0,0 +1,53 @@
+package text
+
+import (
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+const scrambleRunes = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789#$%&*+?"
+
+type ScrambleTextOptions struct {
+	Slot  pixel.Slot
+	Scale int
+	// FPS is zero for 30; two steps settle a character.
+	FPS int
+}
+
+type scrambleKey struct{}
+
+type scrambleState struct {
+	text        string
+	start, step int
+}
+
+// ScrambleText settles from random glyphs to s, left to right.
+func ScrambleText(c *ui.Context, s string, o ScrambleTextOptions) *ui.Element {
+	k, sc := pixel.K(c), scale(o.Scale)
+	fps := orDef("ScrambleText FPS", o.FPS, 30)
+	rs := []rune(s)
+	e := ui.Box(c).Size(k.D(pixel.Measure(s)*sc), k.D(pixel.LineHeight*sc)).Label(s).Role(ui.RoleText)
+	st := ui.Local(e, scrambleKey{}, func() scrambleState { return scrambleState{start: -1} })
+	if st.text != s {
+		*st = scrambleState{text: s, start: -1}
+	}
+	settled := len(rs)
+	if !k.Reduce() && (st.start < 0 || (st.step-st.start)/2 < len(rs)) {
+		st.step = k.Tick(c, fps)
+		if st.start < 0 {
+			st.start = st.step
+		}
+		settled = min(len(rs), (st.step-st.start)/2)
+	}
+	step := st.step
+	return e.Draw(func(p *ui.Painter, r ui.Rect) {
+		g := k.Canvas(p, r)
+		each(s, sc, func(i int, ch rune, x int) {
+			if i >= settled && ch != ' ' {
+				ch = rune(scrambleRunes[noise(len(rs), i, step)%uint32(len(scrambleRunes))])
+			}
+			g.Text(x, 0, string(ch), o.Slot, sc)
+		})
+	})
+}