move menu widget into subpackage

widgets/menu.go

@@ -0,0 +1,89 @@
+package widgets
+
+import (
+	ui "github.com/gizak/termui"
+)
+
+var (
+	padding  = 2
+	minWidth = 30
+)
+
+type Menu struct {
+	ui.Block
+	Items       []string
+	TextFgColor ui.Attribute
+	TextBgColor ui.Attribute
+	Selectable  bool
+	CursorPos   int
+}
+
+func NewMenu(items []string) *Menu {
+	m := &Menu{
+		Block:       *ui.NewBlock(),
+		Items:       items,
+		TextFgColor: ui.ThemeAttr("par.text.fg"),
+		TextBgColor: ui.ThemeAttr("par.text.bg"),
+		Selectable:  false,
+		CursorPos:   0,
+	}
+	m.Width, m.Height = calcSize(items)
+	return m
+}
+
+func (m *Menu) Buffer() ui.Buffer {
+	var cell ui.Cell
+	buf := m.Block.Buffer()
+
+	for n, item := range m.Items {
+		x := padding
+		for _, ch := range item {
+			// invert bg/fg colors on currently selected row
+			if m.Selectable && n == m.CursorPos {
+				cell = ui.Cell{Ch: ch, Fg: m.TextBgColor, Bg: m.TextFgColor}
+			} else {
+				cell = ui.Cell{Ch: ch, Fg: m.TextFgColor, Bg: m.TextBgColor}
+			}
+			buf.Set(x, n+padding, cell)
+			x++
+		}
+	}
+
+	return buf
+}
+
+func (m *Menu) Up(ui.Event) {
+	if m.CursorPos > 0 {
+		m.CursorPos--
+		ui.Render(m)
+	}
+}
+
+func (m *Menu) Down(ui.Event) {
+	if m.CursorPos < (len(m.Items) - 1) {
+		m.CursorPos++
+		ui.Render(m)
+	}
+}
+
+// Setup some default handlers for menu navigation
+func (m *Menu) NavigationHandlers() {
+	ui.Handle("/sys/kbd/<up>", m.Up)
+	ui.Handle("/sys/kbd/<down>", m.Down)
+	ui.Handle("/sys/kbd/q", func(ui.Event) { ui.StopLoop() })
+}
+
+// return width and height based on menu items
+func calcSize(items []string) (w, h int) {
+	h = len(items) + (padding * 2)
+
+	w = minWidth
+	for _, s := range items {
+		if len(s) > w {
+			w = len(s)
+		}
+	}
+	w += (padding * 2)
+
+	return w, h
+}