Add feedback components 106-130; inert scope, focus return, two-step deploy

feedback/shake.go

@@ -0,0 +1,26 @@
+package feedback
+
+import (
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type ShakeOptions struct {
+	// Cue shakes the child each time it changes.
+	Cue int
+}
+
+// shakes are the child's offsets in dots, a step each.
+var shakes = [...]int{2, -2, 2, -2, 1, -1, 0}
+
+// Shake jolts its child side to side briefly.
+func Shake(c *ui.Context, o ShakeOptions, content func()) *ui.Element {
+	k := pixel.K(c)
+	e := ui.Box(c)
+	dx := 0
+	if step := since(c, k, cue(e, k, o.Cue), 20, len(shakes)-1); !k.Reduce() {
+		dx = shakes[step]
+	}
+	return e.Padding(0, k.D(2-dx), 0, k.D(2+dx)).Children(content)
+}