Add game components 246-268; data.DrawSlot, Canvas.TextVeil

Health, mana and experience bars, quarter hearts, lives, a spinning
coin counter, score board, stage timer, minimap with fog, compass,
hotbar, paper-doll equipment, skill tree, skill buttons with cooldown
wipes, status effects, a boss bar, damage numbers, quest log and
tracker, party frames, character sheet, level-up screen and shop.
data exports DrawSlot so every slot looks alike; pixel adds TextVeil
for dissolving text. Messages the font cannot draw are fixed and
TestMessagesHaveGlyphs holds every message to the font.

game/compass.go

@@ -0,0 +1,78 @@
+package game
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+// Bearing marks a direction on a compass, in degrees.
+type Bearing struct {
+	Degrees float64
+	Slot    pixel.Slot
+}
+
+type CompassOptions struct {
+	// Width is in dots; zero means 120. It shows 180°.
+	Width int
+}
+
+// Compass is a heading strip with letters and markers.
+func Compass(c *ui.Context, text string, heading float64, marks []Bearing, o CompassOptions) *ui.Element {
+	k := pixel.K(c)
+	for _, v := range append([]float64{heading}, bearings(marks)...) {
+		if math.IsNaN(v) || math.IsInf(v, 0) {
+			panic(fmt.Sprintf("game: Compass bearing %v", v))
+		}
+	}
+	w := pixel.Or("Compass Width", o.Width, 120)
+	letters := strings.Fields(k.Msg("compass"))
+	heading = math.Mod(math.Mod(heading, 360)+360, 360)
+	// x places bearing b; false means off the strip.
+	x := func(b float64) (int, bool) {
+		d := math.Mod(math.Mod(b-heading, 360)+540, 360) - 180
+		return w/2 + int(math.Round(d*float64(w)/180)), d >= -90 && d <= 90
+	}
+	top := tagH(letters[0]) + 3
+	return ui.Box(c).Role(ui.RoleImage).Label(text).Description(strconv.Itoa(int(math.Round(heading)))+"°").Size(k.D(w), k.D(top+10)).Draw(func(p *ui.Painter, r ui.Rect) {
+		g := k.Canvas(p, r)
+		g.Frame(0, top, w, 10, pixel.Sunken, pixel.Well)
+		for b := 0; b < 360; b += 15 {
+			at, ok := x(float64(b))
+			if !ok || at < 1 || at > w-2 {
+				continue
+			}
+			tall := 3
+			if b%45 == 0 {
+				tall = 6
+			}
+			g.VLine(at, top+10-1-tall, tall, pixel.Edge)
+			if b%90 == 0 {
+				l := letters[b/90]
+				tag(g, max(0, min(w-tagW(l), at-tagW(l)/2)), 0, l, pixel.Ink)
+			}
+		}
+		for _, m := range marks {
+			if at, ok := x(m.Degrees); ok {
+				g.Rect(max(1, min(w-4, at-1)), top+2, 3, 3, m.Slot)
+			}
+		}
+		// The heading's own mark points down at the middle.
+		g.Rect(w/2-2, top-1, 5, 1, pixel.Accent)
+		g.Rect(w/2-1, top, 3, 1, pixel.Accent)
+		g.Dot(w/2, top+1, pixel.Accent)
+	})
+}
+
+func bearings(marks []Bearing) []float64 {
+	out := make([]float64, len(marks))
+	for i, m := range marks {
+		out[i] = m.Degrees
+	}
+	return out
+}