Add input components 086-105; park focus off disabled controls

input/knob.go

@@ -0,0 +1,55 @@
+package input
+
+import (
+	"math"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type KnobOptions struct {
+	// Min and Max are zero for 0 to 1.
+	Min, Max float64
+	// Step snaps the value; zero means none.
+	Step     float64
+	Disabled bool
+}
+
+type KnobResult = SliderResult
+
+type knobKey struct{}
+
+// Knob turns through 16 angles by vertical drag or arrows.
+func Knob(c *ui.Context, text string, value *float64, o KnobOptions) KnobResult {
+	k := pixel.K(c)
+	lo, hi := bounds(o.Min, o.Max)
+	r := rail{lo: lo, hi: hi, step: o.Step}
+	shell, base, st := pixel.Shell(c, func() *ui.Element {
+		return ui.Box(c).Focusable().Role(ui.RoleSlider).Label(text).Description(fmtValue(*value)).Disabled(o.Disabled)
+	})
+	old, set := *value, r.snap(value)
+	// raw is the unrounded value a drag carries.
+	raw := ui.Local(base, knobKey{}, func() float64 { return *value })
+	if !o.Disabled {
+		if _, dy, held := base.Dragged(); held {
+			*raw = max(lo, min(hi, *raw-float64(dy/k.Dot())*(hi-lo)/64))
+			set(*raw)
+		} else {
+			*raw = *value
+		}
+		r.keys(base, value, set)
+	}
+	shell.Size(k.D(24), k.D(24)).Draw(func(p *ui.Painter, rc ui.Rect) {
+		g := k.Canvas(p, rc)
+		g.Disc(12, 12, 11, pixel.Edge)
+		g.Disc(12, 12, 10, pixel.Shade)
+		g.Disc(11, 11, 9, pixel.Face)
+		a := (-135 + 18*math.Round((*value-lo)/(hi-lo)*15)) * math.Pi / 180
+		x, y := 12+int(math.Round(7*math.Sin(a))), 12-int(math.Round(7*math.Cos(a)))
+		g.Line(12, 12, x, y, pixel.Accent)
+		g.Dot(x, y, pixel.Ink)
+		finish(g, st)
+	})
+	return report(shell, *value != old, "knob", text, *value)
+}