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package ui
import (
"github.com/gdamore/tcell"
"github.com/mattn/go-runewidth"
)
// editor is the text field where the user writes messages and commands.
type editor struct {
// text contains the written runes. An empty slice means no text is written.
text []rune
// textWidth[i] contains the width of string(text[:i]). Therefore
// len(textWidth) is always strictly greater than 0 and textWidth[0] is
// always 0.
textWidth []int
// cursorIdx is the index in text of the placement of the cursor, or is
// equal to len(text) if the cursor is at the end.
cursorIdx int
// offsetIdx is the number of elements of text that are skipped when
// rendering.
offsetIdx int
// width is the width of the screen.
width int
}
func newEditor(width int) editor {
return editor{
text: []rune{},
textWidth: []int{0},
width: width,
}
}
func (e *editor) Resize(width int) {
if width < e.width {
e.cursorIdx = 0
e.offsetIdx = 0
}
e.width = width
}
func (e *editor) IsCommand() bool {
return len(e.text) != 0 && e.text[0] == '/'
}
func (e *editor) TextLen() int {
return len(e.text)
}
func (e *editor) PutRune(r rune) {
e.text = append(e.text, ' ')
copy(e.text[e.cursorIdx+1:], e.text[e.cursorIdx:])
e.text[e.cursorIdx] = r
rw := runewidth.RuneWidth(r)
tw := e.textWidth[len(e.textWidth)-1]
e.textWidth = append(e.textWidth, tw+rw)
for i := e.cursorIdx + 1; i < len(e.textWidth); i++ {
e.textWidth[i] = rw + e.textWidth[i-1]
}
e.Right()
}
func (e *editor) RemRune() (ok bool) {
ok = 0 < e.cursorIdx
if !ok {
return
}
// TODO avoid looping twice
rw := e.textWidth[e.cursorIdx] - e.textWidth[e.cursorIdx-1]
for i := e.cursorIdx; i < len(e.textWidth); i++ {
e.textWidth[i] -= rw
}
copy(e.textWidth[e.cursorIdx:], e.textWidth[e.cursorIdx+1:])
e.textWidth = e.textWidth[:len(e.textWidth)-1]
copy(e.text[e.cursorIdx-1:], e.text[e.cursorIdx:])
e.text = e.text[:len(e.text)-1]
e.Left()
return
}
func (e *editor) Flush() (content string) {
content = string(e.text)
e.text = e.text[:0]
e.textWidth = e.textWidth[:1]
e.cursorIdx = 0
e.offsetIdx = 0
return
}
func (e *editor) Right() {
if e.cursorIdx == len(e.text) {
return
}
e.cursorIdx++
if e.width < e.textWidth[e.cursorIdx]-e.textWidth[e.offsetIdx] {
e.offsetIdx += 16
max := len(e.text) - 1
if max < e.offsetIdx {
e.offsetIdx = max
}
}
}
func (e *editor) Left() {
if e.cursorIdx == 0 {
return
}
e.cursorIdx--
if e.cursorIdx <= e.offsetIdx {
e.offsetIdx -= 16
if e.offsetIdx < 0 {
e.offsetIdx = 0
}
}
}
func (e *editor) Draw(screen tcell.Screen, y int) {
st := tcell.StyleDefault
x := 0
i := e.offsetIdx
for i < len(e.text) && x < e.width {
r := e.text[i]
screen.SetContent(x, y, r, nil, st)
x += runewidth.RuneWidth(r)
i++
}
for x < e.width {
screen.SetContent(x, y, ' ', nil, st)
x++
}
curStart := e.textWidth[e.cursorIdx] - e.textWidth[e.offsetIdx]
curEnd := curStart + 1
if e.cursorIdx+1 < len(e.textWidth) {
curEnd = e.textWidth[e.cursorIdx+1] - e.textWidth[e.offsetIdx]
}
for x := curStart; x < curEnd; x++ {
screen.ShowCursor(x, y)
}
}
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