Terminal-based user interface toolkit
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package cview
import (
// frameText holds information about a line of text shown in the frame.
type frameText struct {
Text string // The text to be displayed.
Header bool // true = place in header, false = place in footer.
Align int // One of the Align constants.
Color tcell.Color // The text color.
// Frame is a wrapper which adds space around another primitive. In addition,
// the top area (header) and the bottom area (footer) may also contain text.
type Frame struct {
// The contained primitive.
primitive Primitive
// The lines of text to be displayed.
text []*frameText
// Border spacing.
top, bottom, header, footer, left, right int
// NewFrame returns a new frame around the given primitive. The primitive's
// size will be changed to fit within this frame.
func NewFrame(primitive Primitive) *Frame {
box := NewBox()
f := &Frame{
Box: box,
primitive: primitive,
top: 1,
bottom: 1,
header: 1,
footer: 1,
left: 1,
right: 1,
f.focus = f
return f
// AddText adds text to the frame. Set "header" to true if the text is to appear
// in the header, above the contained primitive. Set it to false for it to
// appear in the footer, below the contained primitive. "align" must be one of
// the Align constants. Rows in the header are printed top to bottom, rows in
// the footer are printed bottom to top. Note that long text can overlap as
// different alignments will be placed on the same row.
func (f *Frame) AddText(text string, header bool, align int, color tcell.Color) {
defer f.Unlock()
f.text = append(f.text, &frameText{
Text: text,
Header: header,
Align: align,
Color: color,
// Clear removes all text from the frame.
func (f *Frame) Clear() {
defer f.Unlock()
f.text = nil
// SetBorders sets the width of the frame borders as well as "header" and
// "footer", the vertical space between the header and footer text and the
// contained primitive (does not apply if there is no text).
func (f *Frame) SetBorders(top, bottom, header, footer, left, right int) {
defer f.Unlock()
f.top, f.bottom, f.header, f.footer, f.left, f.right = top, bottom, header, footer, left, right
// Draw draws this primitive onto the screen.
func (f *Frame) Draw(screen tcell.Screen) {
if !f.GetVisible() {
defer f.Unlock()
// Calculate start positions.
x, top, width, height := f.GetInnerRect()
bottom := top + height - 1
x += f.left
top += f.top
bottom -= f.bottom
width -= f.left + f.right
if width <= 0 || top >= bottom {
return // No space left.
// Draw text.
var rows [6]int // top-left, top-center, top-right, bottom-left, bottom-center, bottom-right.
topMax := top
bottomMin := bottom
for _, text := range f.text {
// Where do we place this text?
var y int
if text.Header {
y = top + rows[text.Align]
if y >= bottomMin {
if y+1 > topMax {
topMax = y + 1
} else {
y = bottom - rows[3+text.Align]
if y <= topMax {
if y-1 < bottomMin {
bottomMin = y - 1
// Draw text.
Print(screen, []byte(text.Text), x, y, width, text.Align, text.Color)
// Set the size of the contained primitive.
if topMax > top {
top = topMax + f.header
if bottomMin < bottom {
bottom = bottomMin - f.footer
if top > bottom {
return // No space for the primitive.
f.primitive.SetRect(x, top, width, bottom+1-top)
// Finally, draw the contained primitive.
// Focus is called when this primitive receives focus.
func (f *Frame) Focus(delegate func(p Primitive)) {
primitive := f.primitive
defer f.Unlock()
// HasFocus returns whether or not this primitive has focus.
func (f *Frame) HasFocus() bool {
defer f.RUnlock()
focusable, ok := f.primitive.(Focusable)
if ok {
return focusable.HasFocus()
return false
// MouseHandler returns the mouse handler for this primitive.
func (f *Frame) MouseHandler() func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive) {
return f.WrapMouseHandler(func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive) {
if !f.InRect(event.Position()) {
return false, nil
// Pass mouse events on to contained primitive.
return f.primitive.MouseHandler()(action, event, setFocus)