Added Primitive demo to go along with the GitHub Wiki entry on how to create your own primitive.

box.go

@@ -130,10 +130,12 @@ func (b *Box) GetDrawFunc() func(screen tcell.Screen, x, y, width, height int) (
 	return b.draw
 }
 
-// wrapInputHandler wraps an input handler (see InputHandler()) with the
+// WrapInputHandler wraps an input handler (see InputHandler()) with the
 // functionality to capture input (see SetInputCapture()) before passing it
 // on to the provided (default) input handler.
-func (b *Box) wrapInputHandler(inputHandler func(*tcell.EventKey, func(p Primitive))) func(*tcell.EventKey, func(p Primitive)) {
+//
+// This is only meant to be used by subclassing primitives.
+func (b *Box) WrapInputHandler(inputHandler func(*tcell.EventKey, func(p Primitive))) func(*tcell.EventKey, func(p Primitive)) {
 	return func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		if b.inputCapture != nil {
 			event = b.inputCapture(event)
@@ -146,7 +148,7 @@ func (b *Box) wrapInputHandler(inputHandler func(*tcell.EventKey, func(p Primiti
 
 // InputHandler returns nil.
 func (b *Box) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return b.wrapInputHandler(nil)
+	return b.WrapInputHandler(nil)
 }
 
 // SetInputCapture installs a function which captures key events before they are

button.go

@@ -121,7 +121,7 @@ func (b *Button) Draw(screen tcell.Screen) {
 
 // InputHandler returns the handler for this primitive.
 func (b *Button) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return b.wrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return b.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		// Process key event.
 		switch key := event.Key(); key {
 		case tcell.KeyEnter: // Selected.

checkbox.go

@@ -155,7 +155,7 @@ func (c *Checkbox) Draw(screen tcell.Screen) {
 
 // InputHandler returns the handler for this primitive.
 func (c *Checkbox) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return c.wrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return c.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		// Process key event.
 		switch key := event.Key(); key {
 		case tcell.KeyRune, tcell.KeyEnter: // Check.

demos/primitive/README.md

@@ -0,0 +1 @@
+![Screenshot](screenshot.png)

demos/primitive/main.go

@@ -0,0 +1,70 @@
+// Demo code which illustrates how to implement your own primitive.
+package main
+
+import (
+	"fmt"
+
+	"github.com/gdamore/tcell"
+	"github.com/rivo/tview"
+)
+
+// RadioButtons implements a simple primitive for radio button selections.
+type RadioButtons struct {
+	*tview.Box
+	options       []string
+	currentOption int
+}
+
+// NewRadioButtons returns a new radio button primitive.
+func NewRadioButtons(options []string) *RadioButtons {
+	return &RadioButtons{
+		Box:     tview.NewBox(),
+		options: options,
+	}
+}
+
+// Draw draws this primitive onto the screen.
+func (r *RadioButtons) Draw(screen tcell.Screen) {
+	r.Box.Draw(screen)
+	x, y, width, height := r.GetInnerRect()
+
+	for index, option := range r.options {
+		if index >= height {
+			break
+		}
+		radioButton := "\u25ef" // Unchecked.
+		if index == r.currentOption {
+			radioButton = "\u25c9" // Checked.
+		}
+		line := fmt.Sprintf(`%s[white]  %s`, radioButton, option)
+		tview.Print(screen, line, x, y+index, width, tview.AlignLeft, tcell.ColorYellow)
+	}
+}
+
+// InputHandler returns the handler for this primitive.
+func (r *RadioButtons) InputHandler() func(event *tcell.EventKey, setFocus func(p tview.Primitive)) {
+	return r.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p tview.Primitive)) {
+		switch event.Key() {
+		case tcell.KeyUp:
+			r.currentOption--
+			if r.currentOption < 0 {
+				r.currentOption = 0
+			}
+		case tcell.KeyDown:
+			r.currentOption++
+			if r.currentOption >= len(r.options) {
+				r.currentOption = len(r.options) - 1
+			}
+		}
+	})
+}
+
+func main() {
+	radioButtons := NewRadioButtons([]string{"Lions", "Elephants", "Giraffes"})
+	radioButtons.SetBorder(true).
+		SetTitle("Radio Button Demo").
+		SetRect(0, 0, 30, 5)
+	if err := tview.NewApplication().SetRoot(radioButtons, false).Run(); err != nil {
+		panic(err)
+	}
+}

dropdown.go

@@ -299,7 +299,7 @@ func (d *DropDown) Draw(screen tcell.Screen) {
 
 // InputHandler returns the handler for this primitive.
 func (d *DropDown) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return d.wrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return d.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		// A helper function which selects an item in the drop-down list based on
 		// the current prefix.
 		evalPrefix := func() {

grid.go

@@ -263,7 +263,7 @@ func (g *Grid) HasFocus() bool {
 
 // InputHandler returns the handler for this primitive.
 func (g *Grid) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return g.wrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return g.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		switch event.Key() {
 		case tcell.KeyRune:
 			switch event.Rune() {

inputfield.go

@@ -289,7 +289,7 @@ func (i *InputField) setCursor(screen tcell.Screen) {
 
 // InputHandler returns the handler for this primitive.
 func (i *InputField) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return i.wrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return i.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		// Trigger changed events.
 		currentText := i.text
 		defer func() {

list.go

@@ -259,7 +259,7 @@ func (l *List) Draw(screen tcell.Screen) {
 
 // InputHandler returns the handler for this primitive.
 func (l *List) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return l.wrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return l.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		previousItem := l.currentItem
 
 		switch key := event.Key(); key {

primitive.go

@@ -31,7 +31,7 @@ type Primitive interface {
 	//
 	// The Box class provides functionality to intercept keyboard input. If you
 	// subclass from Box, it is recommended that you wrap your handler using
-	// Box.wrapInputHandler() so you inherit that functionality.
+	// Box.WrapInputHandler() so you inherit that functionality.
 	InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive))
 
 	// Focus is called by the application when the primitive receives focus.

table.go

@@ -818,7 +818,7 @@ ColumnLoop:
 
 // InputHandler returns the handler for this primitive.
 func (t *Table) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return t.wrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return t.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		key := event.Key()
 
 		if (!t.rowsSelectable && !t.columnsSelectable && key == tcell.KeyEnter) ||

textview.go

@@ -839,7 +839,7 @@ func (t *TextView) Draw(screen tcell.Screen) {
 
 // InputHandler returns the handler for this primitive.
 func (t *TextView) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
-	return t.wrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return t.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
 		key := event.Key()
 
 		if key == tcell.KeyEscape || key == tcell.KeyEnter || key == tcell.KeyTab || key == tcell.KeyBacktab {