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

input/joystick.go

@@ -0,0 +1,85 @@
+package input
+
+import (
+	"fmt"
+	"math"
+	"time"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type JoystickOptions struct {
+	Disabled bool
+}
+
+type JoystickResult struct {
+	Element *ui.Element
+	// X and Y are in −1…1; Y grows downward.
+	X, Y  float64
+	Moved bool
+}
+
+type stickKey struct{}
+
+// stick is the knob and its last key nudge.
+type stick struct {
+	x, y float64
+	key  time.Time
+}
+
+const (
+	stickSize = 40
+	// stickReach is how far the knob travels, in dots.
+	stickReach = 12
+)
+
+// Joystick drags a knob in a ring; arrows nudge it.
+func Joystick(c *ui.Context, text string, o JoystickOptions) JoystickResult {
+	k := pixel.K(c)
+	shell, base, st := pixel.Shell(c, func() *ui.Element {
+		return ui.Box(c).Focusable().Role(ui.RoleGroup).Label(text).Disabled(o.Disabled)
+	})
+	s := ui.Local(base, stickKey{}, func() stick { return stick{} })
+	ox, oy, now := s.x, s.y, k.Now()
+	for _, m := range []struct {
+		key    ui.Key
+		dx, dy float64
+	}{{ui.KeyLeft, -0.25, 0}, {ui.KeyRight, 0.25, 0}, {ui.KeyUp, 0, -0.25}, {ui.KeyDown, 0, 0.25}} {
+		if base.Shortcut(0, m.key) {
+			s.x, s.y, s.key = s.x+m.dx, s.y+m.dy, now
+		}
+	}
+	_, _, held := base.Dragged()
+	switch {
+	case held && !o.Disabled:
+		px, py, _ := base.PointerPosition()
+		s.x = (float64(px/k.Dot()) - stickSize/2) / stickReach
+		s.y = (float64(py/k.Dot()) - stickSize/2) / stickReach
+		s.key = time.Time{}
+	case now.Sub(s.key) > repeatGap:
+		s.x, s.y = 0, 0
+	default:
+		k.Tick(c, 10)
+	}
+	if l := math.Hypot(s.x, s.y); l > 1 {
+		s.x, s.y = s.x/l, s.y/l
+	}
+	base.Description(fmt.Sprintf("%.2f, %.2f", s.x, s.y))
+	x, y := stickSize/2+int(math.Round(s.x*stickReach)), stickSize/2+int(math.Round(s.y*stickReach))
+	shell.Size(k.D(stickSize), k.D(stickSize)).Draw(func(p *ui.Painter, r ui.Rect) {
+		g := k.Canvas(p, r)
+		const m = stickSize / 2
+		g.Disc(m, m, m-1, pixel.Edge)
+		g.Disc(m, m, m-2, pixel.Well)
+		g.Dither(m-2, 4, 4, stickSize-8, pixel.Well, pixel.Shade, 4)
+		g.Dither(4, m-2, stickSize-8, 4, pixel.Well, pixel.Shade, 4)
+		g.Disc(x+1, y+1, 7, pixel.Shade)
+		g.Disc(x, y, 7, pixel.Edge)
+		g.Disc(x, y, 6, pixel.Accent)
+		g.Disc(x-2, y-2, 2, pixel.AccentLit)
+		finish(g, st)
+	})
+	return JoystickResult{Element: shell, X: s.x, Y: s.y, Moved: s.x != ox || s.y != oy}
+}