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buffer.go
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buffer.go
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package ui
import (
"strings"
"github.com/u-root/u-root/cmds/core/elvish/util"
)
// Cell is an indivisible unit on the screen. It is not necessarily 1 column
// wide.
type Cell struct {
Text string
Width byte
Style string
}
// Pos is the position within a buffer.
type Pos struct {
Line, Col int
}
// CellsWidth returns the total width of a Cell slice.
func CellsWidth(cs []Cell) int {
w := 0
for _, c := range cs {
w += int(c.Width)
}
return w
}
// CompareCells returns whether two Cell slices are equal, and when they are
// not, the first index at which they differ.
func CompareCells(r1, r2 []Cell) (bool, int) {
for i, c := range r1 {
if i >= len(r2) || c != r2[i] {
return false, i
}
}
if len(r1) < len(r2) {
return false, len(r1)
}
return true, 0
}
// Buffer reflects a continuous range of lines on the terminal.
//
// The Unix terminal API provides only awkward ways of querying the terminal
// Buffer, so we keep an internal reflection and do one-way synchronizations
// (Buffer -> terminal, and not the other way around). This requires us to
// exactly match the terminal's idea of the width of characters (wcwidth) and
// where to insert soft carriage returns, so there could be bugs.
type Buffer struct {
Width, Col, Indent int
// EagerWrap controls whether to wrap line as soon as the cursor reaches the
// right edge of the terminal. This is not often desirable as it creates
// unneessary line breaks, but is is useful when echoing the user input.
// will otherwise
EagerWrap bool
// Lines the content of the buffer.
Lines [][]Cell
// Dot is what the user perceives as the cursor.
Dot Pos
}
// NewBuffer builds a new buffer, with one empty line.
func NewBuffer(width int) *Buffer {
return &Buffer{Width: width, Lines: [][]Cell{make([]Cell, 0, width)}}
}
func (b *Buffer) SetIndent(indent int) *Buffer {
b.Indent = indent
return b
}
func (b *Buffer) SetEagerWrap(v bool) *Buffer {
b.EagerWrap = v
return b
}
func (b *Buffer) SetLines(lines ...[]Cell) *Buffer {
b.Lines = lines
b.Col = CellsWidth(lines[len(lines)-1])
return b
}
func (b *Buffer) SetDot(dot Pos) *Buffer {
b.Dot = dot
return b
}
// Cursor returns the current position of the cursor.
func (b *Buffer) Cursor() Pos {
return Pos{len(b.Lines) - 1, b.Col}
}
// BuffersHeight computes the combined height of a number of buffers.
func BuffersHeight(bufs ...*Buffer) (l int) {
for _, buf := range bufs {
if buf != nil {
l += len(buf.Lines)
}
}
return
}
// Low level buffer mutations.
func (b *Buffer) appendLine() {
b.Lines = append(b.Lines, make([]Cell, 0, b.Width))
b.Col = 0
}
func (b *Buffer) appendCell(c Cell) {
n := len(b.Lines)
b.Lines[n-1] = append(b.Lines[n-1], c)
b.Col += int(c.Width)
}
// High-level buffer mutations.
// Newline starts a newline.
func (b *Buffer) Newline() {
b.appendLine()
if b.Indent > 0 {
for i := 0; i < b.Indent; i++ {
b.appendCell(Cell{Text: " ", Width: 1})
}
}
}
var styleForControlChar = Styles{"inverse"}
// Write writes a single rune to a buffer, wrapping the line when needed. If the
// rune is a control character, it will be written using the caret notation
// (like ^X) and gets the additional style of styleForControlChar.
func (b *Buffer) Write(r rune, style string) {
if r == '\n' {
b.Newline()
return
}
wd := util.Wcwidth(r)
c := Cell{string(r), byte(wd), style}
if r < 0x20 || r == 0x7f {
wd = 2
if style != "" {
style = style + ";" + styleForControlChar.String()
} else {
style = styleForControlChar.String()
}
c = Cell{"^" + string(r^0x40), 2, style}
}
if b.Col+wd > b.Width {
b.Newline()
b.appendCell(c)
} else {
b.appendCell(c)
if b.Col == b.Width && b.EagerWrap {
b.Newline()
}
}
}
// WriteString writes a string to a buffer, with one style.
func (b *Buffer) WriteString(text, style string) {
for _, r := range text {
b.Write(r, style)
}
}
// WriteSpaces writes w spaces.
func (b *Buffer) WriteSpaces(w int, style string) {
b.WriteString(strings.Repeat(" ", w), style)
}
// WriteStyleds writes a slice of styled structs.
func (b *Buffer) WriteStyleds(ss []*Styled) {
for _, s := range ss {
b.WriteString(s.Text, s.Styles.String())
}
}
// TrimToLines trims a buffer to the lines [low, high).
func (b *Buffer) TrimToLines(low, high int) {
for i := 0; i < low; i++ {
b.Lines[i] = nil
}
for i := high; i < len(b.Lines); i++ {
b.Lines[i] = nil
}
b.Lines = b.Lines[low:high]
b.Dot.Line -= low
if b.Dot.Line < 0 {
b.Dot.Line = 0
}
}
// Extend adds all lines from b2 to the bottom of this buffer. If moveDot is
// true, the dot is updated to match the dot of b2.
func (b *Buffer) Extend(b2 *Buffer, moveDot bool) {
if b2 != nil && b2.Lines != nil {
if moveDot {
b.Dot.Line = b2.Dot.Line + len(b.Lines)
b.Dot.Col = b2.Dot.Col
}
b.Lines = append(b.Lines, b2.Lines...)
b.Col = b2.Col
}
}
// ExtendRight extends b to the right. It pads each line in b to be at least of
// width w and appends the corresponding line in b2 to it, making new lines in b
// when b2 has more lines than b.
// BUG(xiaq): after calling ExtendRight, the widths of some lines can exceed
// b.width.
func (b *Buffer) ExtendRight(b2 *Buffer, w int) {
i := 0
for ; i < len(b.Lines) && i < len(b2.Lines); i++ {
if w0 := CellsWidth(b.Lines[i]); w0 < w {
b.Lines[i] = append(b.Lines[i], makeSpacing(w-w0)...)
}
b.Lines[i] = append(b.Lines[i], b2.Lines[i]...)
}
for ; i < len(b2.Lines); i++ {
row := append(makeSpacing(w), b2.Lines[i]...)
b.Lines = append(b.Lines, row)
}
b.Col = CellsWidth(b.Lines[len(b.Lines)-1])
}
func makeSpacing(n int) []Cell {
s := make([]Cell, n)
for i := 0; i < n; i++ {
s[i].Text = " "
s[i].Width = 1
}
return s
}