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marquee.go
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marquee.go
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package marquee
import (
"context"
"fmt"
"strings"
"sync"
"time"
tea "github.com/charmbracelet/bubbletea"
"github.com/charmbracelet/lipgloss"
"github.com/muesli/ansi"
"github.com/muesli/termenv"
)
const defaultScrollSpeed = time.Millisecond * 250
// Internal ID management. Used during animating to ensure that frame messages
// are received only by marquee components that sent them.
var (
scrollID int
idMtx sync.Mutex
)
// Return the next ID we should use on the Model.
func nextID() int {
idMtx.Lock()
defer idMtx.Unlock()
scrollID++
return scrollID
}
// initialScrollMsg initializes the marquee scrolling.
type initialScrollMsg struct{}
// ScrollMsg signals that the marquee should scroll.
type ScrollMsg struct {
id int
tag int
}
// scrollCanceled is sent when a scroll operation is canceled.
type scrollCanceled struct{}
// scrollCtx manages marquee scrolling.
type scrollCtx struct {
ctx context.Context
cancel context.CancelFunc
}
// Direction describes the direction for the marquee.
type Direction int
// Available directions.
const (
Left Direction = iota
Right
)
// Model is the Bubble Tea model for the marquee.
type Model struct {
ScrollSpeed time.Duration
// Style for styling the marquee block.
Style lipgloss.Style
// The direction in which the text will scroll.
ScrollDirection Direction
// Text holds the text displayed by the marquee.
text string
// Width sets the view's width to a fixed value. If this is not specified,
// the width is assumed to be the length of Text.
width int
// The ID of this Model as it relates to other marquees.
id int
// Used to manage marquee scrolling
scrollCtx *scrollCtx
// The ID of the blink message we're expecting to receive.
tag int
// Holds the current text view.
textView string
// The current text index being displayed
textIndex int
// The non-printable chars prefix.
prefix string
// If the text should be continuous.
isTextContinuous bool
}
// New creates a new model with default settings.
func New() Model {
return Model{
ScrollSpeed: defaultScrollSpeed,
scrollCtx: &scrollCtx{
ctx: context.Background(),
},
id: nextID(),
}
}
// Sets marquee text content.
func (m *Model) SetText(text string) {
m.text = text
if m.width == 0 {
m.SetWidth(ansi.PrintableRuneWidth(m.text))
}
m.resetTextView()
}
func (m *Model) resetTextView() {
if m.isTextContinuous {
m.textView = m.text
} else {
space := strings.Repeat(" ", m.width)
m.textView = fmt.Sprintf("%s%s%s", space, m.text, space)
}
}
// Sets marquee width.
func (m *Model) SetWidth(width int) {
if width <= 0 {
return
}
m.width = width
m.resetTextView()
}
// Sets if the text of the marquee should be continuous.
func (m *Model) SetContinuous(continuous bool) {
m.isTextContinuous = continuous
m.resetTextView()
}
// Update updates the marquee.
func (m Model) Update(msg tea.Msg) (Model, tea.Cmd) {
switch msg := msg.(type) {
case ScrollMsg:
if msg.id != m.id || msg.tag != m.tag {
return m, nil
}
if m.ScrollDirection == Left {
m.textIndex++
if m.textIndex > m.width+len(m.text) || m.isTextContinuous && m.textIndex > len(m.textView) {
m.textIndex = 0
}
var index int
m.prefix, _, index, _ = m.nonPrintableCharactersBeforeIndex(m.textIndex)
if index > m.textIndex {
m.textIndex = index
}
} else {
m.textIndex--
if m.textIndex < 0 {
m.textIndex = m.width + len(m.text)
}
var index int
_, m.prefix, _, index = m.nonPrintableCharactersBeforeIndex(m.textIndex)
if index < m.textIndex {
m.textIndex = index
}
}
return m, m.tick(m.id, m.tag)
case scrollCanceled:
return m, nil
}
return m, nil
}
// ScrollCmd is the command to control the marquee scrolling.
func (m *Model) ScrollCmd() tea.Cmd {
if m.scrollCtx != nil && m.scrollCtx.cancel != nil {
m.scrollCtx.cancel()
}
ctx, cancel := context.WithTimeout(m.scrollCtx.ctx, m.ScrollSpeed)
m.scrollCtx.cancel = cancel
m.tag++
return func() tea.Msg {
defer cancel()
<-ctx.Done()
if ctx.Err() == context.DeadlineExceeded {
return ScrollMsg{id: m.id, tag: m.tag}
}
return scrollCanceled{}
}
}
// Scroll is a command used to initialize marquee scrolling.
func (m Model) Scroll() tea.Msg {
return ScrollMsg{
id: m.id,
tag: m.tag,
}
}
func (m Model) tick(id, tag int) tea.Cmd {
return tea.Tick(m.ScrollSpeed, func(t time.Time) tea.Msg {
return ScrollMsg{
id: id,
tag: tag,
}
})
}
// View displays the marquee.
func (m Model) View() string {
var text string
if m.isTextContinuous {
var b strings.Builder
b.WriteString(m.textView[m.textIndex:])
for i := 0; ansi.PrintableRuneWidth(b.String()) < m.width; i = (i + 1) % len(m.textView) {
b.WriteByte(m.textView[i])
}
text = b.String()
for ansi.PrintableRuneWidth(text) > m.width {
text = text[:len(text)-1]
}
} else {
right := m.textIndex + m.width
for ansi.PrintableRuneWidth(m.textView[m.textIndex:right]) < m.width {
right++
}
text = m.textView[m.textIndex:right]
}
return m.Style.Render(fmt.Sprintf("%s%s%sm", m.prefix, text, termenv.CSI+termenv.ResetSeq))
}
func (m Model) nonPrintableCharactersBeforeIndex(index int) (string, string, int, int) {
var b strings.Builder
inModifier := false
i := 0
prev := len(m.textView)
prevString := ""
for i < len(m.textView) {
c := rune(m.textView[i])
if c == ansi.Marker {
b.WriteRune(c)
inModifier = true
} else if inModifier {
b.WriteRune(c)
if ansi.IsTerminator(c) {
inModifier = false
}
} else {
if i <= index {
prev = i
prevString = b.String()
}
if i >= index {
break
}
}
i++
}
return b.String(), prevString, i, prev
}