Terminal-based user interface toolkit
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package cview
import (
"fmt"
"math"
"regexp"
"sort"
"strconv"
"github.com/gdamore/tcell/v2"
"github.com/mattn/go-runewidth"
"github.com/rivo/uniseg"
)
// TrueColorTags is a flag which controls whether color tags should render as
// the specific colors defined by tcell, or as the colors defined by the user's
// terminal configuration (the default).
var TrueColorTags = false
// ColorUnset represents an unset color. This is necessary because the zero
// value of color, ColorDefault, results in default terminal colors.
var ColorUnset = tcell.ColorSpecial | 108
// Horizontal alignment within a box.
const (
AlignLeft = iota
AlignCenter
AlignRight
)
// VerticalAlignment represents vertical alignment.
type VerticalAlignment int
// Vertical alignment within a box.
const (
AlignTop VerticalAlignment = iota
AlignMiddle
AlignBottom
)
// Common regular expressions.
var (
colorPattern = regexp.MustCompile(`\[([a-zA-Z]+|#[0-9a-zA-Z]{6}|\-)?(:([a-zA-Z]+|#[0-9a-zA-Z]{6}|\-)?(:([bdilrsu]+|\-)?)?)?\]`)
regionPattern = regexp.MustCompile(`\["([a-zA-Z0-9_,;: \-\.]*)"\]`)
escapePattern = regexp.MustCompile(`\[([a-zA-Z0-9_,;: \-\."#]+)\[(\[*)\]`)
nonEscapePattern = regexp.MustCompile(`(\[[a-zA-Z0-9_,;: \-\."#]+\[*)\]`)
boundaryPattern = regexp.MustCompile(`(([,\.\-:;!\?&#+]|\n)[ \t\f\r]*|([ \t\f\r]+))`)
spacePattern = regexp.MustCompile(`\s+`)
)
// Positions of substrings in regular expressions.
const (
colorForegroundPos = 1
colorBackgroundPos = 3
colorFlagPos = 5
)
// Predefined InputField acceptance functions.
var (
// InputFieldInteger accepts integers.
InputFieldInteger func(text string, ch rune) bool
// InputFieldFloat accepts floating-point numbers.
InputFieldFloat func(text string, ch rune) bool
// InputFieldMaxLength returns an input field accept handler which accepts
// input strings up to a given length. Use it like this:
//
// inputField.SetAcceptanceFunc(InputFieldMaxLength(10)) // Accept up to 10 characters.
InputFieldMaxLength func(maxLength int) func(text string, ch rune) bool
)
// Transformation describes a widget state modification.
type Transformation int
// Widget transformations.
const (
TransformFirstItem Transformation = 1
TransformLastItem Transformation = 2
TransformPreviousItem Transformation = 3
TransformNextItem Transformation = 4
TransformPreviousPage Transformation = 5
TransformNextPage Transformation = 6
)
// Package initialization.
func init() {
runewidth.EastAsianWidth = true
runewidth.CreateLUT() // Create lookup table
// Initialize the predefined input field handlers.
InputFieldInteger = func(text string, ch rune) bool {
if text == "-" {
return true
}
_, err := strconv.Atoi(text)
return err == nil
}
InputFieldFloat = func(text string, ch rune) bool {
if text == "-" || text == "." || text == "-." {
return true
}
_, err := strconv.ParseFloat(text, 64)
return err == nil
}
InputFieldMaxLength = func(maxLength int) func(text string, ch rune) bool {
return func(text string, ch rune) bool {
return len([]rune(text)) <= maxLength
}
}
}
// StripTags returns the provided text without color and/or region tags.
func StripTags(text []byte, colors bool, regions bool) []byte {
if !colors && !regions {
stripped := make([]byte, len(text))
copy(stripped, text)
return stripped
}
var stripped []byte
src := text
if regions {
stripped = regionPattern.ReplaceAll(text, nil)
src = stripped
}
if colors {
stripped = colorPattern.ReplaceAllFunc(src, func(match []byte) []byte {
if len(match) > 2 {
return nil
}
return match
})
}
return escapePattern.ReplaceAll(stripped, []byte(`[$1$2]`))
}
// ColorHex returns the hexadecimal value of a color as a string, prefixed with #.
// If the color is invalid, a blank string is returned.
func ColorHex(c tcell.Color) string {
if !c.Valid() {
return ""
}
r, g, b := c.RGB()
return fmt.Sprintf("#%02x%02x%02x", r, g, b)
}
// styleFromTag takes the given style, defined by a foreground color (fgColor),
// a background color (bgColor), and style attributes, and modifies it based on
// the substrings (tagSubstrings) extracted by the regular expression for color
// tags. The new colors and attributes are returned where empty strings mean
// "don't modify" and a dash ("-") means "reset to default".
func styleFromTag(fgColor, bgColor, attributes string, tagSubstrings [][]byte) (newFgColor, newBgColor, newAttributes string) {
if len(tagSubstrings[colorForegroundPos]) > 0 {
color := string(tagSubstrings[colorForegroundPos])
if color == "-" {
fgColor = "-"
} else if color != "" {
fgColor = color
}
}
if len(tagSubstrings[colorBackgroundPos-1]) > 0 {
color := string(tagSubstrings[colorBackgroundPos])
if color == "-" {
bgColor = "-"
} else if color != "" {
bgColor = color
}
}
if len(tagSubstrings[colorFlagPos-1]) > 0 {
flags := string(tagSubstrings[colorFlagPos])
if flags == "-" {
attributes = "-"
} else if flags != "" {
attributes = flags
}
}
return fgColor, bgColor, attributes
}
// overlayStyle mixes a background color with a foreground color (fgColor),
// a (possibly new) background color (bgColor), and style attributes, and
// returns the resulting style. For a definition of the colors and attributes,
// see styleFromTag(). Reset instructions cause the corresponding part of the
// default style to be used.
func overlayStyle(background tcell.Color, defaultStyle tcell.Style, fgColor, bgColor, attributes string) tcell.Style {
defFg, defBg, defAttr := defaultStyle.Decompose()
style := defaultStyle.Background(background)
style = style.Foreground(defFg)
if fgColor != "" {
if fgColor == "-" {
style = style.Foreground(defFg)
} else {
c := tcell.GetColor(fgColor)
if TrueColorTags {
c = c.TrueColor()
}
style = style.Foreground(c)
}
}
if bgColor == "-" || bgColor == "" && defBg != tcell.ColorDefault {
style = style.Background(defBg)
} else if bgColor != "" {
c := tcell.GetColor(bgColor)
if TrueColorTags {
c = c.TrueColor()
}
style = style.Background(c)
}
if attributes == "-" {
style = style.Bold(defAttr&tcell.AttrBold > 0)
style = style.Dim(defAttr&tcell.AttrDim > 0)
style = style.Italic(defAttr&tcell.AttrItalic > 0)
style = style.Blink(defAttr&tcell.AttrBlink > 0)
style = style.Reverse(defAttr&tcell.AttrReverse > 0)
style = style.StrikeThrough(defAttr&tcell.AttrStrikeThrough > 0)
style = style.Underline(defAttr&tcell.AttrUnderline > 0)
} else if attributes != "" {
style = style.Normal()
for _, flag := range attributes {
switch flag {
case 'b':
style = style.Bold(true)
case 'd':
style = style.Dim(true)
case 'i':
style = style.Italic(true)
case 'l':
style = style.Blink(true)
case 'r':
style = style.Reverse(true)
case 's':
style = style.StrikeThrough(true)
case 'u':
style = style.Underline(true)
}
}
}
return style
}
// SetAttributes sets attributes on a style.
func SetAttributes(style tcell.Style, attrs tcell.AttrMask) tcell.Style {
return style.
Bold(attrs&tcell.AttrBold != 0).
Dim(attrs&tcell.AttrDim != 0).
Italic(attrs&tcell.AttrItalic != 0).
Blink(attrs&tcell.AttrBlink != 0).
Reverse(attrs&tcell.AttrReverse != 0).
StrikeThrough(attrs&tcell.AttrStrikeThrough != 0).
Underline(attrs&tcell.AttrUnderline != 0)
}
// decomposeText returns information about a string which may contain color
// tags or region tags, depending on which ones are requested to be found. It
// returns the indices of the color tags (as returned by
// re.FindAllStringIndex()), the color tags themselves (as returned by
// re.FindAllStringSubmatch()), the indices of region tags and the region tags
// themselves, the indices of an escaped tags (only if at least color tags or
// region tags are requested), the string stripped by any tags and escaped, and
// the screen width of the stripped string.
func decomposeText(text []byte, findColors, findRegions bool) (colorIndices [][]int, colors [][][]byte, regionIndices [][]int, regions [][][]byte, escapeIndices [][]int, stripped []byte, width int) {
// Shortcut for the trivial case.
if !findColors && !findRegions {
return nil, nil, nil, nil, nil, text, runewidth.StringWidth(string(text))
}
// Get positions of any tags.
if findColors {
colorIndices = colorPattern.FindAllIndex(text, -1)
colors = colorPattern.FindAllSubmatch(text, -1)
}
if findRegions {
regionIndices = regionPattern.FindAllIndex(text, -1)
regions = regionPattern.FindAllSubmatch(text, -1)
}
escapeIndices = escapePattern.FindAllIndex(text, -1)
// Because the color pattern detects empty tags, we need to filter them out.
for i := len(colorIndices) - 1; i >= 0; i-- {
if colorIndices[i][1]-colorIndices[i][0] == 2 {
colorIndices = append(colorIndices[:i], colorIndices[i+1:]...)
colors = append(colors[:i], colors[i+1:]...)
}
}
// Make a (sorted) list of all tags.
var allIndices [][]int
if findColors && findRegions {
allIndices = colorIndices
allIndices = make([][]int, len(colorIndices)+len(regionIndices))
copy(allIndices, colorIndices)
copy(allIndices[len(colorIndices):], regionIndices)
sort.Slice(allIndices, func(i int, j int) bool {
return allIndices[i][0] < allIndices[j][0]
})
} else if findColors {
allIndices = colorIndices
} else {
allIndices = regionIndices
}
// Remove the tags from the original string.
var from int
buf := make([]byte, 0, len(text))
for _, indices := range allIndices {
buf = append(buf, text[from:indices[0]]...)
from = indices[1]
}
buf = append(buf, text[from:]...)
// Escape string.
stripped = escapePattern.ReplaceAll(buf, []byte("[$1$2]"))
// Get the width of the stripped string.
width = runewidth.StringWidth(string(stripped))
return
}
// Print prints text onto the screen into the given box at (x,y,maxWidth,1),
// not exceeding that box. "align" is one of AlignLeft, AlignCenter, or
// AlignRight. The screen's background color will not be changed.
//
// You can change the colors and text styles mid-text by inserting a color tag.
// See the package description for details.
//
// Returns the number of actual bytes of the text printed (including color tags)
// and the actual width used for the printed runes.
func Print(screen tcell.Screen, text []byte, x, y, maxWidth, align int, color tcell.Color) (int, int) {
return PrintStyle(screen, text, x, y, maxWidth, align, tcell.StyleDefault.Foreground(color))
}
// PrintStyle works like Print() but it takes a style instead of just a
// foreground color.
func PrintStyle(screen tcell.Screen, text []byte, x, y, maxWidth, align int, style tcell.Style) (int, int) {
if maxWidth <= 0 || len(text) == 0 {
return 0, 0
}
// Decompose the text.
colorIndices, colors, _, _, escapeIndices, strippedText, strippedWidth := decomposeText(text, true, false)
// We want to reduce all alignments to AlignLeft.
if align == AlignRight {
if strippedWidth <= maxWidth {
// There's enough space for the entire text.
return PrintStyle(screen, text, x+maxWidth-strippedWidth, y, maxWidth, AlignLeft, style)
}
// Trim characters off the beginning.
var (
bytes, width, colorPos, escapePos, tagOffset int
foregroundColor, backgroundColor, attributes string
)
_, originalBackground, _ := style.Decompose()
iterateString(string(strippedText), func(main rune, comb []rune, textPos, textWidth, screenPos, screenWidth int) bool {
// Update color/escape tag offset and style.
if colorPos < len(colorIndices) && textPos+tagOffset >= colorIndices[colorPos][0] && textPos+tagOffset < colorIndices[colorPos][1] {
foregroundColor, backgroundColor, attributes = styleFromTag(foregroundColor, backgroundColor, attributes, colors[colorPos])
style = overlayStyle(originalBackground, style, foregroundColor, backgroundColor, attributes)
tagOffset += colorIndices[colorPos][1] - colorIndices[colorPos][0]
colorPos++
}
if escapePos < len(escapeIndices) && textPos+tagOffset >= escapeIndices[escapePos][0] && textPos+tagOffset < escapeIndices[escapePos][1] {
tagOffset++
escapePos++
}
if strippedWidth-screenPos < maxWidth {
// We chopped off enough.
if escapePos > 0 && textPos+tagOffset-1 >= escapeIndices[escapePos-1][0] && textPos+tagOffset-1 < escapeIndices[escapePos-1][1] {
// Unescape open escape sequences.
escapeCharPos := escapeIndices[escapePos-1][1] - 2
text = append(text[:escapeCharPos], text[escapeCharPos+1:]...)
}
// Print and return.
bytes, width = PrintStyle(screen, text[textPos+tagOffset:], x, y, maxWidth, AlignLeft, style)
return true
}
return false
})
return bytes, width
} else if align == AlignCenter {
if strippedWidth == maxWidth {
// Use the exact space.
return PrintStyle(screen, text, x, y, maxWidth, AlignLeft, style)
} else if strippedWidth < maxWidth {
// We have more space than we need.
half := (maxWidth - strippedWidth) / 2
return PrintStyle(screen, text, x+half, y, maxWidth-half, AlignLeft, style)
} else {
// Chop off runes until we have a perfect fit.
var choppedLeft, choppedRight, leftIndex, rightIndex int
rightIndex = len(strippedText)
for rightIndex-1 > leftIndex && strippedWidth-choppedLeft-choppedRight > maxWidth {
if choppedLeft < choppedRight {
// Iterate on the left by one character.
iterateString(string(strippedText[leftIndex:]), func(main rune, comb []rune, textPos, textWidth, screenPos, screenWidth int) bool {
choppedLeft += screenWidth
leftIndex += textWidth
return true
})
} else {
// Iterate on the right by one character.
iterateStringReverse(string(strippedText[leftIndex:rightIndex]), func(main rune, comb []rune, textPos, textWidth, screenPos, screenWidth int) bool {
choppedRight += screenWidth
rightIndex -= textWidth
return true
})
}
}
// Add tag offsets and determine start style.
var (
colorPos, escapePos, tagOffset int
foregroundColor, backgroundColor, attributes string
)
_, originalBackground, _ := style.Decompose()
for index := range strippedText {
// We only need the offset of the left index.
if index > leftIndex {
// We're done.
if escapePos > 0 && leftIndex+tagOffset-1 >= escapeIndices[escapePos-1][0] && leftIndex+tagOffset-1 < escapeIndices[escapePos-1][1] {
// Unescape open escape sequences.
escapeCharPos := escapeIndices[escapePos-1][1] - 2
text = append(text[:escapeCharPos], text[escapeCharPos+1:]...)
}
break
}
// Update color/escape tag offset.
if colorPos < len(colorIndices) && index+tagOffset >= colorIndices[colorPos][0] && index+tagOffset < colorIndices[colorPos][1] {
if index <= leftIndex {
foregroundColor, backgroundColor, attributes = styleFromTag(foregroundColor, backgroundColor, attributes, colors[colorPos])
style = overlayStyle(originalBackground, style, foregroundColor, backgroundColor, attributes)
}
tagOffset += colorIndices[colorPos][1] - colorIndices[colorPos][0]
colorPos++
}
if escapePos < len(escapeIndices) && index+tagOffset >= escapeIndices[escapePos][0] && index+tagOffset < escapeIndices[escapePos][1] {
tagOffset++
escapePos++
}
}
return PrintStyle(screen, text[leftIndex+tagOffset:], x, y, maxWidth, AlignLeft, style)
}
}
// Draw text.
var (
drawn, drawnWidth, colorPos, escapePos, tagOffset int
foregroundColor, backgroundColor, attributes string
)
iterateString(string(strippedText), func(main rune, comb []rune, textPos, length, screenPos, screenWidth int) bool {
// Only continue if there is still space.
if drawnWidth+screenWidth > maxWidth {
return true
}
// Handle color tags.
for colorPos < len(colorIndices) && textPos+tagOffset >= colorIndices[colorPos][0] && textPos+tagOffset < colorIndices[colorPos][1] {
foregroundColor, backgroundColor, attributes = styleFromTag(foregroundColor, backgroundColor, attributes, colors[colorPos])
tagOffset += colorIndices[colorPos][1] - colorIndices[colorPos][0]
colorPos++
}
// Handle scape tags.
if escapePos < len(escapeIndices) && textPos+tagOffset >= escapeIndices[escapePos][0] && textPos+tagOffset < escapeIndices[escapePos][1] {
if textPos+tagOffset == escapeIndices[escapePos][1]-2 {
tagOffset++
escapePos++
}
}
// Print the rune sequence.
finalX := x + drawnWidth
_, _, finalStyle, _ := screen.GetContent(finalX, y)
_, background, _ := finalStyle.Decompose()
finalStyle = overlayStyle(background, style, foregroundColor, backgroundColor, attributes)
for offset := screenWidth - 1; offset >= 0; offset-- {
// To avoid undesired effects, we populate all cells.
if offset == 0 {
screen.SetContent(finalX+offset, y, main, comb, finalStyle)
} else {
screen.SetContent(finalX+offset, y, ' ', nil, finalStyle)
}
}
// Advance.
drawn += length
drawnWidth += screenWidth
return false
})
return drawn + tagOffset + len(escapeIndices), drawnWidth
}
// PrintSimple prints white text to the screen at the given position.
func PrintSimple(screen tcell.Screen, text []byte, x, y int) {
Print(screen, text, x, y, math.MaxInt32, AlignLeft, Styles.PrimaryTextColor)
}
// TaggedTextWidth returns the width of the given string needed to print it on
// screen. The text may contain color tags which are not counted.
func TaggedTextWidth(text []byte) int {
_, _, _, _, _, _, width := decomposeText(text, true, false)
return width
}
// TaggedStringWidth returns the width of the given string needed to print it on
// screen. The text may contain color tags which are not counted.
func TaggedStringWidth(text string) int {
return TaggedTextWidth([]byte(text))
}
// WordWrap splits a text such that each resulting line does not exceed the
// given screen width. Possible split points are after any punctuation or
// whitespace. Whitespace after split points will be dropped.
//
// This function considers color tags to have no width.
//
// Text is always split at newline characters ('\n').
//
// BUG(tslocum) Text containing square brackets is not escaped properly.
// Use TextView.SetWrapWidth where possible.
//
// Issue: https://code.rocketnine.space/tslocum/cview/issues/27
func WordWrap(text string, width int) (lines []string) {
colorTagIndices, _, _, _, escapeIndices, strippedText, _ := decomposeText([]byte(text), true, false)
// Find candidate breakpoints.
breakpoints := boundaryPattern.FindAllSubmatchIndex(strippedText, -1)
// Results in one entry for each candidate. Each entry is an array a of
// indices into strippedText where a[6] < 0 for newline/punctuation matches
// and a[4] < 0 for whitespace matches.
// Process stripped text one character at a time.
var (
colorPos, escapePos, breakpointPos, tagOffset int
lastBreakpoint, lastContinuation, currentLineStart int
lineWidth, overflow int
forceBreak bool
)
unescape := func(substr string, startIndex int) string {
// A helper function to unescape escaped tags.
for index := escapePos; index >= 0; index-- {
if index < len(escapeIndices) && startIndex > escapeIndices[index][0] && startIndex < escapeIndices[index][1]-1 {
pos := escapeIndices[index][1] - 2 - startIndex
if pos < 0 || pos > len(substr) { // Workaround for issue #27
return substr
}
return substr[:pos] + substr[pos+1:]
}
}
return substr
}
iterateString(string(strippedText), func(main rune, comb []rune, textPos, textWidth, screenPos, screenWidth int) bool {
// Handle tags.
for {
if colorPos < len(colorTagIndices) && textPos+tagOffset >= colorTagIndices[colorPos][0] && textPos+tagOffset < colorTagIndices[colorPos][1] {
// Colour tags.
tagOffset += colorTagIndices[colorPos][1] - colorTagIndices[colorPos][0]
colorPos++
} else if escapePos < len(escapeIndices) && textPos+tagOffset == escapeIndices[escapePos][1]-2 {
// Escape tags.
tagOffset++
escapePos++
} else {
break
}
}
// Is this a breakpoint?
if breakpointPos < len(breakpoints) && textPos+tagOffset == breakpoints[breakpointPos][0] {
// Yes, it is. Set up breakpoint infos depending on its type.
lastBreakpoint = breakpoints[breakpointPos][0] + tagOffset
lastContinuation = breakpoints[breakpointPos][1] + tagOffset
overflow = 0
forceBreak = main == '\n'
if breakpoints[breakpointPos][6] < 0 && !forceBreak {
lastBreakpoint++ // Don't skip punctuation.
}
breakpointPos++
}
// Check if a break is warranted.
if forceBreak || lineWidth > 0 && lineWidth+screenWidth > width {
breakpoint := lastBreakpoint
continuation := lastContinuation
if forceBreak {
breakpoint = textPos + tagOffset
continuation = textPos + tagOffset + 1
lastBreakpoint = 0
overflow = 0
} else if lastBreakpoint <= currentLineStart {
breakpoint = textPos + tagOffset
continuation = textPos + tagOffset
overflow = 0
}
lines = append(lines, unescape(text[currentLineStart:breakpoint], currentLineStart))
currentLineStart, lineWidth, forceBreak = continuation, overflow, false
}
// Remember the characters since the last breakpoint.
if lastBreakpoint > 0 && lastContinuation <= textPos+tagOffset {
overflow += screenWidth
}
// Advance.
lineWidth += screenWidth
// But if we're still inside a breakpoint, skip next character (whitespace).
if textPos+tagOffset < currentLineStart {
lineWidth -= screenWidth
}
return false
})
// Flush the rest.
if currentLineStart < len(text) {
lines = append(lines, unescape(text[currentLineStart:], currentLineStart))
}
return
}
// EscapeBytes escapes the given text such that color and/or region tags are not
// recognized and substituted by the print functions of this package. For
// example, to include a tag-like string in a box title or in a TextView:
//
// box.SetTitle(cview.Escape("[squarebrackets]"))
// fmt.Fprint(textView, cview.EscapeBytes(`["quoted"]`))
func EscapeBytes(text []byte) []byte {
return nonEscapePattern.ReplaceAll(text, []byte("$1[]"))
}
// Escape escapes the given text such that color and/or region tags are not
// recognized and substituted by the print functions of this package. For
// example, to include a tag-like string in a box title or in a TextView:
//
// box.SetTitle(cview.Escape("[squarebrackets]"))
// fmt.Fprint(textView, cview.Escape(`["quoted"]`))
func Escape(text string) string {
return nonEscapePattern.ReplaceAllString(text, "$1[]")
}
// iterateString iterates through the given string one printed character at a
// time. For each such character, the callback function is called with the
// Unicode code points of the character (the first rune and any combining runes
// which may be nil if there aren't any), the starting position (in bytes)
// within the original string, its length in bytes, the screen position of the
// character, and the screen width of it. The iteration stops if the callback
// returns true. This function returns true if the iteration was stopped before
// the last character.
func iterateString(text string, callback func(main rune, comb []rune, textPos, textWidth, screenPos, screenWidth int) bool) bool {
var screenPos int
gr := uniseg.NewGraphemes(text)
for gr.Next() {
r := gr.Runes()
from, to := gr.Positions()
width := runewidth.StringWidth(gr.Str())
var comb []rune
if len(r) > 1 {
comb = r[1:]
}
if callback(r[0], comb, from, to-from, screenPos, width) {
return true
}
screenPos += width
}
return false
}
// iterateStringReverse iterates through the given string in reverse, starting
// from the end of the string, one printed character at a time. For each such
// character, the callback function is called with the Unicode code points of
// the character (the first rune and any combining runes which may be nil if
// there aren't any), the starting position (in bytes) within the original
// string, its length in bytes, the screen position of the character, and the
// screen width of it. The iteration stops if the callback returns true. This
// function returns true if the iteration was stopped before the last character.
func iterateStringReverse(text string, callback func(main rune, comb []rune, textPos, textWidth, screenPos, screenWidth int) bool) bool {
type cluster struct {
main rune
comb []rune
textPos, textWidth, screenPos, screenWidth int
}
// Create the grapheme clusters.
var clusters []cluster
iterateString(text, func(main rune, comb []rune, textPos int, textWidth int, screenPos int, screenWidth int) bool {
clusters = append(clusters, cluster{
main: main,
comb: comb,
textPos: textPos,
textWidth: textWidth,
screenPos: screenPos,
screenWidth: screenWidth,
})
return false
})
// Iterate in reverse.
for index := len(clusters) - 1; index >= 0; index-- {
if callback(
clusters[index].main,
clusters[index].comb,
clusters[index].textPos,
clusters[index].textWidth,
clusters[index].screenPos,
clusters[index].screenWidth,
) {
return true
}
}
return false
}
// ScrollBarVisibility specifies the display of a scroll bar.
type ScrollBarVisibility int
const (
// ScrollBarNever never shows a scroll bar.
ScrollBarNever ScrollBarVisibility = iota
// ScrollBarAuto shows a scroll bar when there are items offscreen.
ScrollBarAuto
// ScrollBarAlways always shows a scroll bar.
ScrollBarAlways
)
// Scroll bar render text (must be one cell wide)
var (
ScrollBarArea = []byte("[-:-:-]░")
ScrollBarAreaFocused = []byte("[-:-:-]▒")
ScrollBarHandle = []byte("[-:-:-]▓")
ScrollBarHandleFocused = []byte("[::r] [-:-:-]")
)
// RenderScrollBar renders a scroll bar at the specified position.
func RenderScrollBar(screen tcell.Screen, visibility ScrollBarVisibility, x int, y int, height int, items int, cursor int, printed int, focused bool, color tcell.Color) {
if visibility == ScrollBarNever || (visibility == ScrollBarAuto && items <= height) {
return
}
// Place cursor at top when there are no items offscreen.
if items <= height {
cursor = 0
}
// Handle negative cursor.
if cursor < 0 {
cursor = 0
}
// Calculate handle position.
handlePosition := int(float64(height-1) * (float64(cursor) / float64(items-1)))
// Print scroll bar.
var text []byte
if printed == handlePosition {
if focused {
text = ScrollBarHandleFocused
} else {
text = ScrollBarHandle
}
} else {
if focused {
text = ScrollBarAreaFocused
} else {
text = ScrollBarArea
}
}
Print(screen, text, x, y, 1, AlignLeft, color)
}