Add text widget

cmd/aerc/main.go

@@ -62,6 +62,9 @@ func main() {
 	})
 
 	// TODO: move sidebar into tab content, probably
+	grid.AddChild(ui.NewText("aerc").
+		Strategy(ui.TEXT_CENTER).
+		Color(tb.ColorBlack, tb.ColorWhite))
 	// sidebar placeholder:
 	grid.AddChild(ui.NewBordered(
 		fill('.'), ui.BORDER_RIGHT)).At(1, 0).Span(2, 1)

ui/text.go

@@ -0,0 +1,71 @@
+package ui
+
+import (
+	"github.com/mattn/go-runewidth"
+	tb "github.com/nsf/termbox-go"
+)
+
+const (
+	TEXT_LEFT   = iota
+	TEXT_CENTER = iota
+	TEXT_RIGHT  = iota
+)
+
+type Text struct {
+	text         string
+	strategy     uint
+	fg           tb.Attribute
+	bg           tb.Attribute
+	onInvalidate func(d Drawable)
+}
+
+func NewText(text string) *Text {
+	return &Text{text: text}
+}
+
+func (t *Text) Text(text string) *Text {
+	t.text = text
+	t.Invalidate()
+	return t
+}
+
+func (t *Text) Strategy(strategy uint) *Text {
+	t.strategy = strategy
+	t.Invalidate()
+	return t
+}
+
+func (t *Text) Color(fg tb.Attribute, bg tb.Attribute) *Text {
+	t.fg = fg
+	t.bg = bg
+	t.Invalidate()
+	return t
+}
+
+func (t *Text) Draw(ctx *Context) {
+	size := runewidth.StringWidth(t.text)
+	cell := tb.Cell{
+		Ch: ' ',
+		Fg: t.fg,
+		Bg: t.bg,
+	}
+	x := 0
+	if t.strategy == TEXT_CENTER {
+		x = (ctx.Width() - size) / 2
+	}
+	if t.strategy == TEXT_RIGHT {
+		x = ctx.Width() - size
+	}
+	ctx.Fill(0, 0, ctx.Width(), ctx.Height(), cell)
+	ctx.Printf(x, 0, cell, "%s", t.text)
+}
+
+func (t *Text) OnInvalidate(onInvalidate func(d Drawable)) {
+	t.onInvalidate = onInvalidate
+}
+
+func (t *Text) Invalidate() {
+	if t.onInvalidate != nil {
+		t.onInvalidate(t)
+	}
+}