Terminal-based user interface toolkit
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package tview
import (
"bytes"
"math"
"regexp"
"sync"
"unicode/utf8"
"github.com/gdamore/tcell"
)
// textColors maps color strings which may be embedded in text sent to a
// TextView to their tcell counterparts.
var textColors = map[string]tcell.Color{
"red": tcell.ColorRed,
"white": tcell.ColorWhite,
"yellow": tcell.ColorYellow,
"blue": tcell.ColorBlue,
"green": tcell.ColorGreen,
}
// Regular expressions commonly used throughout the TextView class.
var (
colorPattern = regexp.MustCompile(`\[(white|yellow|blue|green|red)\]`)
regionPattern = regexp.MustCompile(`\["([a-zA-Z0-9_,;: \-\.]*)"\]`)
)
// textViewIndex contains information about each line displayed in the text
// view.
type textViewIndex struct {
Line int // The index into the "buffer" variable.
Pos int // The index into the "buffer" string.
Color tcell.Color // The starting color.
Region string // The starting region ID.
}
// TextView is a box which displays text. It implements the io.Writer interface
// so you can stream text to it. This does not trigger a redraw automatically
// but if a handler is installed via SetChangedFunc(), you can cause it to be
// redrawn.
//
// Navigation
//
// If the text view is scrollable (the default), text is kept in a buffer which
// may be larger than the screen and can be navigated similarly to Vim:
//
// - h, left arrow: Move left.
// - l, right arrow: Move right.
// - j, down arrow: Move down.
// - k, up arrow: Move up.
// - g, home: Move to the top.
// - G, end: Move to the bottom.
// - Ctrl-F, page down: Move down by one page.
// - Ctrl-B, page up: Move up by one page.
//
// If the text is not scrollable, any text above the top line is discarded.
//
// Navigation can be intercepted by installing a callback function via
// SetCaptureFunc() which receives all keyboard events and decides which ones
// to forward to the default handler.
//
// Colors
//
// If dynamic colors are enabled via SetDynamicColors(), text color can be
// changed dynamically by embedding color strings in square brackets. For
// example,
//
// This is a [red]warning[white]!
//
// will print the word "warning" in red. The following colors are currently
// supported: white, yellow, blue, green, red.
//
// Regions and Highlights
//
// If regions are enabled via SetRegions(), you can define text regions within
// the text and assign region IDs to them. Text regions start with region tags.
// Region tags are square brackets that contain a region ID in double quotes,
// for example:
//
// We define a ["rg"]region[""] here.
//
// A text region ends with the next region tag. Tags with no region ID ([""])
// don't start new regions. They can therefore be used to mark the end of a
// region. Region IDs must satisfy the following regular expression:
//
// [a-zA-Z0-9_,;: \-\.]+
//
// Regions can be highlighted by calling the Highlight() function with one or
// more region IDs. This can be used to display search results, for example.
//
// The ScrollToHighlight() function can be used to jump to the currently
// highlighted region once when the text view is drawn the next time.
type TextView struct {
sync.Mutex
*Box
// The text buffer.
buffer []string
// The last bytes that have been received but are not part of the buffer yet.
recentBytes []byte
// The processed line index. This is nil if the buffer has changed and needs
// to be re-indexed.
index []*textViewIndex
// Indices into the "index" slice which correspond to the first line of the
// first highlight and the last line of the last highlight. This is calculated
// during re-indexing. Set to -1 if there is no current highlight.
fromHighlight, toHighlight int
// A set of region IDs that are currently highlighted.
highlights map[string]struct{}
// The display width for which the index is created.
indexWidth int
// The index of the first line shown in the text view.
lineOffset int
// If set to true, the text view will always remain at the end of the content.
trackEnd bool
// The number of characters to be skipped on each line (not in wrap mode).
columnOffset int
// The height of the content the last time the text view was drawn.
pageSize int
// If set to true, the text view will keep a buffer of text which can be
// navigated when the text is longer than what fits into the box.
scrollable bool
// If set to true, lines that are longer than the available width are wrapped
// onto the next line. If set to false, any characters beyond the available
// width are discarded.
wrap bool
// The (starting) color of the text.
textColor tcell.Color
// If set to true, the text color can be changed dynamically by piping color
// strings in square brackets to the text view.
dynamicColors bool
// If set to true, region tags can be used to define regions.
regions bool
// A temporary flag which, when true, will automatically bring the current
// highlight(s) into the visible screen.
scrollToHighlights bool
// An optional function which will receive all key events sent to this text
// view. Returning true also invokes the default key handling.
capture func(*tcell.EventKey) bool
// An optional function which is called when the content of the text view has
// changed.
changed func()
// An optional function which is called when the user presses one of the
// following keys: Escape, Enter, Tab, Backtab.
done func(tcell.Key)
}
// NewTextView returns a new text view.
func NewTextView() *TextView {
return &TextView{
Box: NewBox(),
highlights: make(map[string]struct{}),
lineOffset: -1,
scrollable: true,
wrap: true,
textColor: tcell.ColorWhite,
dynamicColors: false,
}
}
// SetScrollable sets the flag that decides whether or not the text view is
// scollable. If true, text is kept in a buffer and can be navigated.
func (t *TextView) SetScrollable(scrollable bool) *TextView {
t.scrollable = scrollable
return t
}
// SetWrap sets the flag that, if true, leads to lines that are longer than the
// available width being wrapped onto the next line. If false, any characters
// beyond the available width are not displayed.
func (t *TextView) SetWrap(wrap bool) *TextView {
if t.wrap != wrap {
t.index = nil
}
t.wrap = wrap
return t
}
// SetTextColor sets the initial color of the text (which can be changed
// dynamically by sending color strings in square brackets to the text view if
// dynamic colors are enabled).
func (t *TextView) SetTextColor(color tcell.Color) *TextView {
t.textColor = color
return t
}
// SetDynamicColors sets the flag that allows the text color to be changed
// dynamically. See class description for details.
func (t *TextView) SetDynamicColors(dynamic bool) *TextView {
if t.dynamicColors != dynamic {
t.index = nil
}
t.dynamicColors = dynamic
return t
}
// SetRegions sets the flag that allows to define regions in the text. See class
// description for details.
func (t *TextView) SetRegions(regions bool) *TextView {
t.regions = regions
return t
}
// SetCaptureFunc sets a handler which is called whenever a key is pressed.
// This allows you to override the default key handling of the text view.
// Returning true will allow the default key handling to go forward after the
// handler returns. Returning false will disable any default key handling.
func (t *TextView) SetCaptureFunc(handler func(event *tcell.EventKey) bool) *TextView {
t.capture = handler
return t
}
// SetChangedFunc sets a handler function which is called when the text of the
// text view has changed. This is typically used to cause the application to
// redraw the screen.
func (t *TextView) SetChangedFunc(handler func()) *TextView {
t.changed = handler
return t
}
// SetDoneFunc sets a handler which is called when the user presses on the
// following keys: Escape, Enter, Tab, Backtab. The key is passed to the
// handler.
func (t *TextView) SetDoneFunc(handler func(key tcell.Key)) *TextView {
t.done = handler
return t
}
// Clear removes all text from the buffer.
func (t *TextView) Clear() *TextView {
t.buffer = nil
t.recentBytes = nil
t.index = nil
return t
}
// Highlight specifies which regions should be highlighted. See class
// description for details on regions. Empty region strings are ignored.
//
// Text in highlighted regions will be drawn inverted, i.e. with their
// background and foreground colors swapped.
//
// Calling this function will remove any previous highlights. To remove all
// highlights, call this function without any arguments.
func (t *TextView) Highlight(regionIDs ...string) *TextView {
t.highlights = make(map[string]struct{})
for _, id := range regionIDs {
if id == "" {
continue
}
t.highlights[id] = struct{}{}
}
return t
}
// GetHighlights returns the IDs of all currently highlighted regions.
func (t *TextView) GetHighlights() (regionIDs []string) {
for id := range t.highlights {
regionIDs = append(regionIDs, id)
}
return
}
// ScrollToHighlight will cause the visible area to be scrolled so that the
// highlighted regions appear in the visible area of the text view. This
// repositioning happens the next time the text view is drawn. It happens only
// once so you will need to call this function repeatedly to always keep
// highlighted regions in view.
//
// Nothing happens if there are no highlighted regions or if the text view is
// not scrollable.
func (t *TextView) ScrollToHighlight() *TextView {
if len(t.highlights) == 0 || !t.scrollable || !t.regions {
return t
}
t.index = nil
t.scrollToHighlights = true
t.trackEnd = false
return t
}
// GetRegionText returns the text of the region with the given ID. If dynamic
// colors are enabled, color tags are stripped from the text. Newlines are
// always returned as '\n' runes.
//
// If the region does not exist or if regions are turned off, an empty string
// is returned.
func (t *TextView) GetRegionText(regionID string) string {
if !t.regions || regionID == "" {
return ""
}
var (
buffer bytes.Buffer
currentRegionID string
)
for _, str := range t.buffer {
// Find all color tags in this line.
var colorTagIndices [][]int
if t.dynamicColors {
colorTagIndices = colorPattern.FindAllStringIndex(str, -1)
}
// Find all regions in this line.
var (
regionIndices [][]int
regions [][]string
)
if t.regions {
regionIndices = regionPattern.FindAllStringIndex(str, -1)
regions = regionPattern.FindAllStringSubmatch(str, -1)
}
// Analyze this line.
var currentTag, currentRegion int
for pos, ch := range str {
// Skip any color tags.
if currentTag < len(colorTagIndices) && pos >= colorTagIndices[currentTag][0] && pos < colorTagIndices[currentTag][1] {
if pos == colorTagIndices[currentTag][1]-1 {
currentTag++
}
continue
}
// Skip any regions.
if currentRegion < len(regionIndices) && pos >= regionIndices[currentRegion][0] && pos < regionIndices[currentRegion][1] {
if pos == regionIndices[currentRegion][1]-1 {
if currentRegionID == regionID {
// This is the end of the requested region. We're done.
return buffer.String()
}
currentRegionID = regions[currentRegion][1]
currentRegion++
}
continue
}
// Add this rune.
if currentRegionID == regionID {
buffer.WriteRune(ch)
}
}
// Add newline.
if currentRegionID == regionID {
buffer.WriteRune('\n')
}
}
return buffer.String()
}
// Write lets us implement the io.Writer interface.
func (t *TextView) Write(p []byte) (n int, err error) {
// Notify at the end.
if t.changed != nil {
defer t.changed()
}
t.Lock()
defer t.Unlock()
// Copy data over.
newBytes := append(t.recentBytes, p...)
t.recentBytes = nil
// If we have a trailing invalid UTF-8 byte, we'll wait.
if r, _ := utf8.DecodeLastRune(p); r == utf8.RuneError {
t.recentBytes = newBytes
return len(p), nil
}
// If we have a trailing open dynamic color, exclude it.
if t.dynamicColors {
openColor := regexp.MustCompile(`\[[a-z]+$`)
location := openColor.FindIndex(newBytes)
if location != nil {
t.recentBytes = newBytes[location[0]:]
newBytes = newBytes[:location[0]]
}
}
// Transform the new bytes into strings.
newLine := regexp.MustCompile(`\r?\n`)
for index, line := range newLine.Split(string(newBytes), -1) {
if index == 0 {
if len(t.buffer) == 0 {
t.buffer = []string{line}
} else {
t.buffer[len(t.buffer)-1] += line
}
} else {
t.buffer = append(t.buffer, line)
}
}
// Reset the index.
t.index = nil
return len(p), nil
}
// reindexBuffer re-indexes the buffer such that we can use it to easily draw
// the buffer onto the screen. Each line in the index will contain a pointer
// into the buffer from which on we will print text. It will also contain the
// color with which the line starts.
func (t *TextView) reindexBuffer(width int) {
if t.index != nil && width == t.indexWidth {
return // Nothing has changed. We can still use the current index.
}
t.index = nil
t.fromHighlight, t.toHighlight = -1, -1
var (
regionID string
highlighted bool
)
color := t.textColor
if !t.wrap {
width = math.MaxInt64
}
for index, str := range t.buffer {
// Find all color tags in this line.
var (
colorTagIndices [][]int
colorTags [][]string
)
if t.dynamicColors {
colorTagIndices = colorPattern.FindAllStringIndex(str, -1)
colorTags = colorPattern.FindAllStringSubmatch(str, -1)
}
// Find all regions in this line.
var (
regionIndices [][]int
regions [][]string
)
if t.regions {
regionIndices = regionPattern.FindAllStringIndex(str, -1)
regions = regionPattern.FindAllStringSubmatch(str, -1)
}
// We also keep a reference to empty lines.
if len(str) == 0 {
t.index = append(t.index, &textViewIndex{
Line: index,
Pos: 0,
Color: color,
Region: regionID,
})
}
// Break down the line.
var currentTag, currentRegion, currentWidth int
for pos := range str {
// Skip any color tags.
if currentTag < len(colorTags) && pos >= colorTagIndices[currentTag][0] && pos < colorTagIndices[currentTag][1] {
if pos == colorTagIndices[currentTag][1]-1 {
color = textColors[colorTags[currentTag][1]]
currentTag++
}
continue
}
// Check regions.
if currentRegion < len(regionIndices) && pos >= regionIndices[currentRegion][0] && pos < regionIndices[currentRegion][1] {
if pos == regionIndices[currentRegion][1]-1 {
// We're done with this region.
regionID = regions[currentRegion][1]
// Is this region highlighted?
_, highlighted = t.highlights[regionID]
currentRegion++
}
continue
}
// Add this line.
if currentWidth == 0 {
t.index = append(t.index, &textViewIndex{
Line: index,
Pos: pos,
Color: color,
Region: regionID,
})
}
// Update highlight range.
if highlighted {
line := len(t.index) - 1
if t.fromHighlight < 0 {
t.fromHighlight, t.toHighlight = line, line
} else if line > t.toHighlight {
t.toHighlight = line
}
}
// Proceed.
currentWidth++
// Have we crossed the width?
if t.wrap && currentWidth >= width {
currentWidth = 0
}
}
}
t.indexWidth = width
}
// Draw draws this primitive onto the screen.
func (t *TextView) Draw(screen tcell.Screen) {
t.Lock()
defer t.Unlock()
t.Box.Draw(screen)
// Get the available size.
x, y, width, height := t.GetInnerRect()
t.pageSize = height
// Re-index.
t.reindexBuffer(width)
// Move to highlighted regions.
if t.regions && t.scrollToHighlights && t.fromHighlight >= 0 {
// Do we fit the entire height?
if t.toHighlight-t.fromHighlight+1 < height {
// Yes, let's center the highlights.
t.lineOffset = (t.fromHighlight + t.toHighlight - height) / 2
} else {
// No, let's move to the start of the highlights.
t.lineOffset = t.fromHighlight
}
}
t.scrollToHighlights = false
// Adjust line offset.
if t.lineOffset+height > len(t.index) {
t.trackEnd = true
}
if t.trackEnd {
t.lineOffset = len(t.index) - height
}
if t.lineOffset < 0 {
t.lineOffset = 0
}
// Draw the buffer.
for line := t.lineOffset; line < len(t.index); line++ {
// Are we done?
if line-t.lineOffset >= height {
break
}
// Get the text for this line.
index := t.index[line]
text := t.buffer[index.Line][index.Pos:]
color := index.Color
regionID := index.Region
// Get color tags.
var (
colorTagIndices [][]int
colorTags [][]string
)
if t.dynamicColors {
colorTagIndices = colorPattern.FindAllStringIndex(text, -1)
colorTags = colorPattern.FindAllStringSubmatch(text, -1)
}
// Get regions.
var (
regionIndices [][]int
regions [][]string
)
if t.regions {
regionIndices = regionPattern.FindAllStringIndex(text, -1)
regions = regionPattern.FindAllStringSubmatch(text, -1)
}
// Print one line.
var currentTag, currentRegion, skip, posX int
for pos, ch := range text {
// Get the color.
if currentTag < len(colorTags) && pos >= colorTagIndices[currentTag][0] && pos < colorTagIndices[currentTag][1] {
if pos == colorTagIndices[currentTag][1]-1 {
color = textColors[colorTags[currentTag][1]]
currentTag++
}
continue
}
// Get the region.
if currentRegion < len(regionIndices) && pos >= regionIndices[currentRegion][0] && pos < regionIndices[currentRegion][1] {
if pos == regionIndices[currentRegion][1]-1 {
regionID = regions[currentRegion][1]
currentRegion++
}
continue
}
// Skip to the right.
if !t.wrap && skip < t.columnOffset {
skip++
continue
}
// Stop at the right border.
if posX >= width {
break
}
// Do we highlight this character?
style := tcell.StyleDefault.Background(t.backgroundColor).Foreground(color)
if len(regionID) > 0 {
if _, ok := t.highlights[regionID]; ok {
style = tcell.StyleDefault.Background(color).Foreground(t.backgroundColor)
}
}
// Draw the character.
screen.SetContent(x+posX, y+line-t.lineOffset, ch, nil, style)
// Advance.
posX++
}
}
// If this view is not scrollable, we'll purge the buffer of lines that have
// scrolled out of view.
if !t.scrollable && t.lineOffset > 0 {
t.buffer = t.buffer[t.index[t.lineOffset].Line:]
t.index = nil
}
}
// InputHandler returns the handler for this primitive.
func (t *TextView) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
return func(event *tcell.EventKey, setFocus func(p Primitive)) {
// Do we pass this event on?
if t.capture != nil {
if !t.capture(event) {
return
}
}
key := event.Key()
if key == tcell.KeyEscape || key == tcell.KeyEnter || key == tcell.KeyTab || key == tcell.KeyBacktab {
if t.done != nil {
t.done(key)
}
return
}
if !t.scrollable {
return
}
switch key {
case tcell.KeyRune:
switch event.Rune() {
case 'g': // Home.
t.trackEnd = false
t.lineOffset = 0
t.columnOffset = 0
case 'G': // End.
t.trackEnd = true
t.columnOffset = 0
case 'j': // Down.
t.lineOffset++
case 'k': // Up.
t.trackEnd = false
t.lineOffset--
case 'h': // Left.
t.columnOffset--
if t.columnOffset < 0 {
t.columnOffset = 0
}
case 'l': // Right.
t.columnOffset++
}
case tcell.KeyHome:
t.trackEnd = false
t.lineOffset = 0
t.columnOffset = 0
case tcell.KeyEnd:
t.trackEnd = true
t.columnOffset = 0
case tcell.KeyUp:
t.trackEnd = false
t.lineOffset--
case tcell.KeyDown:
t.lineOffset++
case tcell.KeyLeft:
t.columnOffset--
if t.columnOffset < 0 {
t.columnOffset = 0
}
case tcell.KeyRight:
t.columnOffset++
case tcell.KeyPgDn, tcell.KeyCtrlF:
t.lineOffset += t.pageSize
case tcell.KeyPgUp, tcell.KeyCtrlB:
t.trackEnd = false
t.lineOffset -= t.pageSize
}
}
}