Add text components 021-040 with demos and behavior tests

text/shaketext.go

@@ -0,0 +1,34 @@
+package text
+
+import (
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type ShakeTextOptions struct {
+	Slot  pixel.Slot
+	Scale int
+	Seed  int
+}
+
+// ShakeText jitters each character a dot, seeded, at 12 fps.
+func ShakeText(c *ui.Context, s string, o ShakeTextOptions) *ui.Element {
+	k, sc := pixel.K(c), scale(o.Scale)
+	return block(c, k, s, pixel.Measure(s)*sc+2, pixel.LineHeight*sc+2, func(g pixel.Canvas) {
+		step := g.Step(12)
+		each(s, sc, func(i int, r rune, x int) {
+			dx, dy := shake(k.Reduce(), o.Seed, i, step)
+			g.Text(1+x+dx, 1+dy, string(r), o.Slot, sc)
+		})
+	})
+}
+
+// shake is a −1…1 offset, or none under Reduce Motion.
+func shake(reduce bool, seed, i, step int) (dx, dy int) {
+	if reduce {
+		return 0, 0
+	}
+	n := noise(seed, i, step)
+	return int(n%3) - 1, int(n/3%3) - 1
+}