Add data components 151-175; clear MyGo row highlights

Lists, tables, trees, grids, inventories and records in data/.
Outline and GridView build on ui.List: ui.Outline strokes its arrows
and ui.GridView spaces and tints items. The pixel theme keeps MyGo's
row highlights clear so scrolled rows stay on whole dots; off lists
take a veil against the wheel. Adds Canvas.Silhouette, SwitchOptions
Label and exports Rarity.Slot.

data/itemslot.go

@@ -0,0 +1,70 @@
+package data
+
+import (
+	"fmt"
+	"strconv"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/display"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+// Item is what a slot holds; no Sprite means empty.
+type Item struct {
+	Sprite *pixel.Sprite
+	Name   string
+	// Count shows when above one.
+	Count  int
+	Rarity display.Rarity
+}
+
+type ItemSlotOptions struct {
+	// Cooldown, 0 to 1, veils the slot downward.
+	Cooldown float64
+	Selected bool
+}
+
+// ItemSlot shows an item, count, rarity edge and cooldown.
+func ItemSlot(c *ui.Context, it Item, o ItemSlotOptions) *ui.Element {
+	k := pixel.K(c)
+	if !(o.Cooldown >= 0 && o.Cooldown <= 1) {
+		panic(fmt.Sprintf("data: Cooldown %v outside 0–1", o.Cooldown))
+	}
+	return ui.Box(c).Role(ui.RoleImage).Label(itemName(it)).Size(k.D(slotSize), k.D(slotSize)).Draw(func(p *ui.Painter, r ui.Rect) {
+		slot(k.Canvas(p, r), 0, 0, it, o.Cooldown, o.Selected)
+	})
+}
+
+const slotSize = 22
+
+// itemName reads an item with its count.
+func itemName(it Item) string {
+	if it.Count > 1 {
+		return it.Name + " ×" + strconv.Itoa(it.Count)
+	}
+	return it.Name
+}
+
+// slot draws a slot with its top-left at x, y.
+func slot(g pixel.Canvas, x, y int, it Item, cool float64, chosen bool) {
+	edge := pixel.Edge
+	if it.Sprite != nil {
+		edge = it.Rarity.Slot()
+	}
+	if chosen {
+		g.Rect(x, y, slotSize, slotSize, pixel.Accent)
+	}
+	g.Rect(x+1, y+1, slotSize-2, slotSize-2, edge)
+	g.Rect(x+2, y+2, slotSize-4, slotSize-4, pixel.Well)
+	if sp := it.Sprite; sp != nil {
+		g.Sprite(x+2+(slotSize-4-sp.W)/2, y+2+(slotSize-4-sp.H)/2, sp, 0, pixel.Ink, 1)
+	}
+	if h := int(cool * (slotSize - 4)); h > 0 {
+		g.Veil(x+2, y+2, slotSize-4, h, pixel.Shade, 10)
+	}
+	if it.Count > 1 {
+		n := strconv.Itoa(it.Count)
+		g.Micro(x+slotSize-2-pixel.MicroWidth(n), y+slotSize-8, n, pixel.Ink, 1)
+	}
+}