Add text components 021-040 with demos and behavior tests

text/wavetext.go

@@ -0,0 +1,33 @@
+package text
+
+import (
+	"math"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type WaveTextOptions struct {
+	Slot  pixel.Slot
+	Scale int
+	// Amp is the bob in dots; zero means 2.
+	Amp int
+}
+
+// WaveText bobs characters on a sine wave at 10 fps.
+func WaveText(c *ui.Context, s string, o WaveTextOptions) *ui.Element {
+	k, sc := pixel.K(c), scale(o.Scale)
+	amp := orDef("WaveText Amp", o.Amp, 2)
+	return block(c, k, s, pixel.Measure(s)*sc, pixel.LineHeight*sc+2*amp, func(g pixel.Canvas) {
+		step := g.Step(10)
+		each(s, sc, func(i int, r rune, x int) {
+			g.Text(x, amp+wave(amp, step+i), string(r), o.Slot, sc)
+		})
+	})
+}
+
+// wave is the bob at step n of an 8-cycle.
+func wave(amp, n int) int {
+	return int(math.Round(float64(amp) * math.Sin(float64(n%8)*math.Pi/4)))
+}