Add text components 021-040 with demos and behavior tests

text/text.go

@@ -0,0 +1,63 @@
+// Package text draws words in the pixel font.
+package text
+
+import (
+	"fmt"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+// block is a w×h dot text box that fn draws.
+func block(c *ui.Context, k pixel.Kit, s string, w, h int, fn func(g pixel.Canvas)) *ui.Element {
+	return ui.Box(c).Size(k.D(w), k.D(h)).Label(s).Role(ui.RoleText).Draw(func(p *ui.Painter, r ui.Rect) {
+		fn(k.Canvas(p, r))
+	})
+}
+
+// orDef is v, or def for zero; negative panics.
+func orDef(name string, v, def int) int {
+	if v < 0 {
+		panic(fmt.Sprintf("text: %s %d is negative", name, v))
+	}
+	if v == 0 {
+		return def
+	}
+	return v
+}
+
+// scale is s, or 1 for zero; outside 1–4 panics.
+func scale(s int) int {
+	s = orDef("Scale", s, 1)
+	if s > 4 {
+		panic(fmt.Sprintf("text: Scale %d outside 1–4", s))
+	}
+	return s
+}
+
+// slotOr is s, or def for the zero slot.
+func slotOr(s, def pixel.Slot) pixel.Slot {
+	if s == pixel.Ink {
+		return def
+	}
+	return s
+}
+
+// each walks s rune by rune, with x in dots.
+func each(s string, sc int, fn func(i int, r rune, x int)) {
+	i, x := 0, 0
+	for _, r := range s {
+		fn(i, r, x)
+		x += pixel.Measure(string(r)) * sc
+		i++
+	}
+}
+
+// noise is a seeded hash for jitter and scrambles.
+func noise(seed, i, step int) uint32 {
+	x := uint32(seed*73856093 ^ i*19349663 ^ step*83492791)
+	x ^= x >> 13
+	x *= 0x5bd1e995
+	return x ^ x>>15
+}