Add character identifiers to focusable widgets

When no widget has focus, press the letter key to focus on the widget
assigned to that letter.

Example:

    GitHub (d)

    Press "d" to focus on the GitHub widget.

wtf/bargraph.go

@@ -72,10 +72,18 @@ func (widget *BarGraph) Focusable() bool {
 	return widget.enabled && widget.focusable
 }
 
+func (widget *BarGraph) FocusChar() string {
+	return ""
+}
+
 func (widget *BarGraph) RefreshInterval() int {
 	return widget.RefreshInt
 }
 
+func (widget *BarGraph) SetFocusChar(char string) {
+	return
+}
+
 func (widget *BarGraph) TextView() *tview.TextView {
 	return widget.View
 }

wtf/focus_tracker.go

@@ -22,6 +22,28 @@ type FocusTracker struct {
 
 /* -------------------- Exported Functions -------------------- */
 
+// AssignHotKeys assigns an alphabetic keyboard character to each focusable
+// widget so that the widget can be brought into focus by pressing that keyboard key
+func (tracker *FocusTracker) AssignHotKeys() {
+	i := 0
+
+	for _, focusable := range tracker.focusables() {
+		focusable.SetFocusChar(string('a' + i))
+		i++
+	}
+}
+
+func (tracker *FocusTracker) FocusOn(char string) {
+	for idx, focusable := range tracker.focusables() {
+		if focusable.FocusChar() == char {
+			tracker.blur(tracker.Idx)
+			tracker.Idx = idx
+			tracker.focus(tracker.Idx)
+			break
+		}
+	}
+}
+
 // Next sets the focus on the next widget in the widget list. If the current widget is
 // the last widget, sets focus on the first widget.
 func (tracker *FocusTracker) Next() {

wtf/text_widget.go

@@ -13,6 +13,7 @@ var Config *config.Config
 type TextWidget struct {
 	enabled   bool
 	focusable bool
+	focusChar string
 
 	Name        string
 	RefreshedAt time.Time
@@ -53,6 +54,14 @@ func (widget *TextWidget) BorderColor() string {
 	return Config.UString("wtf.colors.border.normal", "gray")
 }
 
+func (widget *TextWidget) ContextualTitle(defaultStr string) string {
+	if widget.FocusChar() == "" {
+		return fmt.Sprintf(" %s ", defaultStr)
+	} else {
+		return fmt.Sprintf(" %s [darkgray](%s)[white] ", defaultStr, widget.FocusChar())
+	}
+}
+
 func (widget *TextWidget) Disable() {
 	widget.enabled = false
 }
@@ -69,10 +78,18 @@ func (widget *TextWidget) Focusable() bool {
 	return widget.enabled && widget.focusable
 }
 
+func (widget *TextWidget) FocusChar() string {
+	return widget.focusChar
+}
+
 func (widget *TextWidget) RefreshInterval() int {
 	return widget.RefreshInt
 }
 
+func (widget *TextWidget) SetFocusChar(char string) {
+	widget.focusChar = char
+}
+
 func (widget *TextWidget) TextView() *tview.TextView {
 	return widget.View
 }
@@ -86,7 +103,7 @@ func (widget *TextWidget) addView() {
 	view.SetBorder(true)
 	view.SetBorderColor(colorFor(widget.BorderColor()))
 	view.SetDynamicColors(true)
-	view.SetTitle(widget.Name)
+	view.SetTitle(widget.ContextualTitle(widget.Name))
 	view.SetWrap(false)
 
 	widget.View = view

wtf/wtfable.go

@@ -10,6 +10,8 @@ type Wtfable interface {
 
 	BorderColor() string
 	Focusable() bool
+	FocusChar() string
+	SetFocusChar(string)
 	TextView() *tview.TextView
 
 	Top() int