Add text components 021-040 with demos and behavior tests

text/heading.go

@@ -0,0 +1,28 @@
+package text
+
+import (
+	"fmt"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type HeadingOptions struct {
+	// Level 1–3 draws at ×3, ×2, ×1; zero means 1.
+	Level int
+	Slot  pixel.Slot
+}
+
+// Heading is a title with a 1-dot Shade shadow.
+func Heading(c *ui.Context, s string, o HeadingOptions) *ui.Element {
+	level := orDef("Heading Level", o.Level, 1)
+	if level > 3 {
+		panic(fmt.Sprintf("text: Heading Level %d outside 1–3", level))
+	}
+	k, sc := pixel.K(c), 4-level
+	return block(c, k, s, pixel.Measure(s)*sc+1, pixel.LineHeight*sc+1, func(g pixel.Canvas) {
+		g.Text(1, 1, s, pixel.Shade, sc)
+		g.Text(0, 0, s, o.Slot, sc)
+	})
+}