Add vertical/horizontal radio button group as a form item

demos/form/main.go

@@ -7,12 +7,24 @@ import (
 
 func main() {
 	app := tview.NewApplication()
-	form := tview.NewForm().
-		AddDropDown("Title", []string{"Mr.", "Ms.", "Mrs.", "Dr.", "Prof."}, 0, nil).
+
+	maleTitles := []string{"Mr.", "Dr.", "Prof."}
+	femaleTitles := []string{"Ms.", "Mrs.", "Dr.", "Prof."}
+
+	form := tview.NewForm()
+	form.AddDropDown("Title", maleTitles, 0, nil).
 		AddInputField("First name", "", 20, nil, nil).
 		AddInputField("Last name", "", 20, nil, nil).
 		AddTextArea("Address", "", 40, 0, 0, nil).
-		AddTextView("Notes", "This is just a demo.\nYou can enter whatever you wish.", 40, 2, true, false).
+		AddRadio("Sex", 0, true, func(newValue int) {
+			dd := form.GetFormItem(0).(*tview.DropDown)
+			if newValue == 0 {
+				dd.SetOptions(maleTitles, nil)
+			} else {
+				dd.SetOptions(femaleTitles, nil)
+			}
+		}, "male", "female").
+		AddTextView("Notes", "This is just a demo.\nYou can enter whatever you wish.\nMind how the radio changes title options", 40, 3, true, false).
 		AddCheckbox("Age 18+", false, nil).
 		AddPasswordField("Password", "", 10, '*', nil).
 		AddButton("Save", nil).

form.go

@@ -309,6 +309,18 @@ func (f *Form) AddCheckbox(label string, checked bool, changed func(checked bool
 	return f
 }
 
+// AddRadio adds a radio button group to the form. It has a label, an initial value,
+// if it's horizontal or vertical, and an (optional) callback function which is invoked
+// when the state of the radio was changed by the user.
+func (f *Form) AddRadio(label string, option int, horizontal bool, changed func(option int), options ...string) *Form {
+	f.items = append(f.items, NewRadio(options...).
+		SetLabel(label).
+		SetValue(option).
+		SetHorizontal(horizontal).
+		SetOnSetValue(changed))
+	return f
+}
+
 // AddImage adds an image to the form. It has a label and the image will fit in
 // the specified width and height (its aspect ratio is preserved). See
 // [Image.SetColors] for a description of the "colors" parameter. Images are not

radio.go

@@ -0,0 +1,286 @@
+package tview
+
+import (
+	"fmt"
+
+	"github.com/gdamore/tcell/v2"
+	"github.com/rivo/uniseg"
+)
+
+var (
+	// RadioCheckedString and RadioUncheckedString are visible characters of checked and unchecked
+	// radio buttons. They can be set globally for the whole app through these variables.
+	RadioCheckedString   = "\u25c9"
+	RadioUncheckedString = "\u25ef"
+)
+
+type Radio struct {
+	*Box
+
+	// The currently selected value.
+	value int
+
+	// The text to be displayed before the input area.
+	label string
+
+	// The list of choosable texts.
+	options []string
+
+	// The screen width of the label area. A value of 0 means use the width of
+	// the label text.
+	labelWidth int
+
+	// A callback function when the user changes the radion button value.
+	onSetValue func(int)
+
+	// The label color.
+	labelColor tcell.Color
+
+	// The background color of the input area.
+	fieldBackgroundColor tcell.Color
+
+	// The text color of the input area.
+	fieldTextColor tcell.Color
+
+	// If set to true, options are positioned from left to right, instead of top to bottom.
+	horizontal bool
+
+	// A callback function set by the Form class and called when the user leaves this form item.
+	finished func(tcell.Key)
+}
+
+// NewRadio creates a radio button group with the given options.
+func NewRadio(options ...string) *Radio {
+	if len(options) == 0 {
+		options = []string{"noOptions"}
+	}
+	return &Radio{
+		Box:                  NewBox(),
+		options:              options,
+		labelColor:           Styles.SecondaryTextColor,
+		fieldBackgroundColor: Styles.ContrastBackgroundColor,
+		fieldTextColor:       Styles.PrimaryTextColor,
+	}
+}
+
+// SetValue sets the current value of the radio group.
+func (r *Radio) SetValue(value int) *Radio {
+	if r.value == value {
+		return r
+	}
+	if value < 0 {
+		value = 0
+	} else if value >= len(r.options) {
+		value = len(r.options) - 1
+	}
+	r.changeValue(value)
+	return r
+}
+
+// Value returns current radio value.
+func (r *Radio) Value() int {
+	return r.value
+}
+
+// changeValue changes the current value, and calls change callback if exists.
+func (r *Radio) changeValue(value int) {
+	r.value = value
+	if r.onSetValue != nil {
+		r.onSetValue(value)
+	}
+}
+
+// SetOnSetValue sets callback handler of a value change.
+func (r *Radio) SetOnSetValue(handler func(int)) *Radio {
+	r.onSetValue = handler
+	return r
+}
+
+// SetHorizontal sets the direction the options are laid out. If set to true, instead
+// of positioning them from top to bottom (the default), they are positioned from left
+// to right, moving into the next row if there is not enough space.
+func (r *Radio) SetHorizontal(horizontal bool) *Radio {
+	r.horizontal = horizontal
+	return r
+}
+
+// InputHandler returns the handler for this primitive.
+func (r *Radio) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
+	return r.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
+		key := event.Key()
+		if r.value > 0 &&
+			((key == tcell.KeyLeft && r.horizontal) ||
+				(key == tcell.KeyUp && !r.horizontal)) {
+			r.changeValue(r.value - 1)
+			return
+		}
+		if r.value < len(r.options)-1 &&
+			((key == tcell.KeyRight && r.horizontal) ||
+				(key == tcell.KeyDown && !r.horizontal)) {
+			r.changeValue(r.value + 1)
+			return
+		}
+		switch key {
+		case tcell.KeyEnter, tcell.KeyTab, tcell.KeyBacktab:
+			if r.finished != nil {
+				r.finished(key)
+			}
+		}
+	})
+}
+
+func (r *Radio) GetLabel() string {
+	return r.label
+}
+
+func (r *Radio) SetLabel(l string) *Radio {
+	r.label = l
+	return r
+}
+
+// SetFormAttributes sets attributes shared by all form items.
+func (r *Radio) SetFormAttributes(labelWidth int, labelColor, bgColor, fieldTextColor, fieldBgColor tcell.Color) FormItem {
+	r.labelWidth = labelWidth
+	r.labelColor = labelColor
+	r.backgroundColor = bgColor
+	r.fieldTextColor = fieldTextColor
+	r.fieldBackgroundColor = fieldBgColor
+	return r
+}
+
+// SetFinishedFunc sets a callback invoked when the user leaves this form item.
+func (r *Radio) SetFinishedFunc(handler func(key tcell.Key)) FormItem {
+	r.finished = handler
+	return r
+}
+
+// GetFieldHeight returns this primitive's field height.
+func (r *Radio) GetFieldHeight() int {
+	if r.horizontal {
+		return 1
+	}
+	return len(r.options)
+}
+
+// GetFieldWidth returns this primitive's field width.
+func (r *Radio) GetFieldWidth() int {
+	w := 0
+	for _, option := range r.options {
+		if r.horizontal {
+			w += len(option) + 3 // checkbox + space + option + space
+			continue
+		}
+		if len(option) > w {
+			w = len(option)
+		}
+	}
+	if r.horizontal {
+		return w - 1
+	}
+	return w + 2
+}
+
+func (r *Radio) Draw(screen tcell.Screen) {
+	r.Box.DrawForSubclass(screen, r)
+	x, y, width, height := r.GetInnerRect()
+	if width < 1 || height < 1 {
+		return
+	}
+
+	// Draw label.
+	var labelBg tcell.Color
+	labelStyle := tcell.StyleDefault.Background(r.fieldBackgroundColor).Foreground(r.labelColor)
+	if r.hasFocus {
+		labelBg = Styles.MoreContrastBackgroundColor
+		labelStyle = labelStyle.Background(Styles.InverseTextColor)
+	} else {
+		_, labelBg, _ = tcell.StyleDefault.Decompose()
+	}
+	if r.labelWidth > 0 {
+		labelWidth := r.labelWidth
+		if labelWidth > width {
+			labelWidth = width
+		}
+		printWithStyle(screen, r.label, x, y, 0, labelWidth, AlignLeft, labelStyle, labelBg == tcell.ColorDefault)
+		x += labelWidth
+	} else {
+		_, drawnWidth, _, _ := printWithStyle(screen, r.label, x, y, 0, width, AlignLeft, labelStyle, labelBg == tcell.ColorDefault)
+		x += drawnWidth
+	}
+
+	// Draw radio buttons.
+	fieldStyle := tcell.StyleDefault.Background(r.fieldBackgroundColor).Foreground(r.fieldTextColor)
+	for i, option := range r.options {
+		rb := RadioUncheckedString
+		if i == r.value {
+			rb = RadioCheckedString
+		}
+		line := fmt.Sprintf("%s %s", rb, option)
+		printWithStyle(screen, line, x, y, 0, width, AlignLeft, fieldStyle, !r.hasFocus || i != r.value)
+		if r.horizontal {
+			x += uniseg.GraphemeClusterCount(line) + 1
+		} else {
+			y += 1
+		}
+	}
+}
+
+// MouseHandler returns the mouse handler for this primitive.
+func (r *Radio) MouseHandler() func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive) {
+	return r.WrapMouseHandler(func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive) {
+		if action != MouseLeftDown && action != MouseLeftClick {
+			return // only interested in these two
+		}
+		x, y := event.Position()
+		if !r.InRect(x, y) {
+			return // out of widget
+		}
+		if action == MouseLeftDown {
+			setFocus(r) // mouse down then moved: focus radio only
+			return true, nil
+		}
+		rectX, rectY, _, _ := r.GetRect()
+		x -= rectX + r.labelWidth
+		y -= rectY
+		if x < 0 {
+			return // clicked on the label
+		}
+		// countOptLen counts this option's width
+		countOptLen := func(i int, option string) int {
+			res := 0
+			if i != r.value {
+				res += uniseg.GraphemeClusterCount(RadioUncheckedString)
+			} else {
+				res += uniseg.GraphemeClusterCount(RadioCheckedString)
+			}
+			res++
+			res += uniseg.GraphemeClusterCount(option)
+			return res
+		}
+		if !r.horizontal {
+			if y < 0 || len(r.options) <= y { // shouldn't be necessary, make sure not to index out
+				return
+			}
+			if x >= countOptLen(y, r.options[y]) {
+				return // clicked to the right of this option
+			}
+			r.SetValue(y) // clicked on this option
+			return true, nil
+		}
+		if y != 0 {
+			return // horizontal radio means single line
+		}
+		for i, option := range r.options { // sum option widths until match
+			x -= countOptLen(i, option)
+			if x < 0 { // match
+				r.SetValue(i)
+				return true, nil
+			}
+			if x == 0 { // the character between two options
+				return
+			}
+			x--
+		}
+		return // not found
+	})
+}