Terminal-based user interface toolkit
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package cview
import (
"bytes"
"regexp"
"sync"
"unicode"
"unicode/utf8"
"github.com/gdamore/tcell/v2"
"github.com/lucasb-eyer/go-colorful"
"github.com/mattn/go-runewidth"
"github.com/rivo/uniseg"
)
var (
// TabSize is the number of spaces with which a tab character will be replaced.
TabSize = 4
)
var (
openColorRegex = regexp.MustCompile(`\[([a-zA-Z]*|#[0-9a-zA-Z]*)$`)
openRegionRegex = 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" line ([]byte position).
NextPos int // The (byte) index of the next character in this buffer line.
Width int // The screen width of this line.
ForegroundColor string // The starting foreground color ("" = don't change, "-" = reset).
BackgroundColor string // The starting background color ("" = don't change, "-" = reset).
Attributes string // The starting attributes ("" = don't change, "-" = reset).
Region []byte // The starting region ID.
}
// textViewRegion contains information about a region.
type textViewRegion struct {
// The region ID.
ID []byte
// The starting and end screen position of the region as determined the last
// time Draw() was called. A negative value indicates out-of-rect positions.
FromX, FromY, ToX, ToY int
}
// 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. (See SetChangedFunc() for more details.)
//
// 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 visible line is
// discarded.
//
// Use SetInputCapture() to override or modify keyboard input.
//
// Colors
//
// If dynamic colors are enabled via SetDynamicColors(), text color can be
// changed dynamically by embedding color strings in square brackets. This works
// the same way as anywhere else. Please see the package documentation for more
// information.
//
// 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 {
*Box
// The text buffer.
buffer [][]byte
// The last bytes that have been received but are not part of the buffer yet.
recentBytes []byte
// The last width and height of the text view.
lastWidth, lastHeight int
// The processed line index. This is nil if the buffer has changed and needs
// to be re-indexed.
index []*textViewIndex
// The width of the text view buffer index.
indexWidth int
// If set to true, the buffer will be reindexed each time it is modified.
reindex bool
// The horizontal text alignment, one of AlignLeft, AlignCenter, or AlignRight.
align int
// The vertical text alignment, one of AlignTop, AlignMiddle, or AlignBottom.
valign VerticalAlignment
// Information about visible regions as of the last call to Draw().
regionInfos []*textViewRegion
// 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
// The screen space column of the highlight in its first line. Set to -1 if
// there is no current highlight.
posHighlight int
// A set of region IDs that are currently highlighted.
highlights map[string]struct{}
// The screen width of the longest line in the index (not the buffer).
longestLine int
// The index of the first line shown in the text view.
lineOffset int
// The maximum number of newlines the text view will hold (0 = unlimited).
maxLines 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
// Visibility of the scroll bar.
scrollBarVisibility ScrollBarVisibility
// The scroll bar color.
scrollBarColor tcell.Color
// 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 maximum line width when wrapping (0 = use TextView width).
wrapWidth int
// If set to true and if wrap is also true, lines are split at spaces or
// after punctuation characters.
wordWrap bool
// The (starting) color of the text.
textColor tcell.Color
// The foreground color of highlighted text.
highlightForeground tcell.Color
// The background color of highlighted text.
highlightBackground 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
// If true, setting new highlights will be a XOR instead of an overwrite
// operation.
toggleHighlights 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)
// An optional function which is called when one or more regions were
// highlighted.
highlighted func(added, removed, remaining []string)
sync.RWMutex
}
// NewTextView returns a new text view.
func NewTextView() *TextView {
return &TextView{
Box: NewBox(),
highlights: make(map[string]struct{}),
lineOffset: -1,
reindex: true,
scrollable: true,
scrollBarVisibility: ScrollBarAuto,
scrollBarColor: Styles.ScrollBarColor,
align: AlignLeft,
valign: AlignTop,
wrap: true,
textColor: Styles.PrimaryTextColor,
highlightForeground: Styles.PrimitiveBackgroundColor,
highlightBackground: Styles.PrimaryTextColor,
}
}
// SetScrollable sets the flag that decides whether or not the text view is
// scrollable. If true, text is kept in a buffer and can be navigated. If false,
// the last line will always be visible.
func (t *TextView) SetScrollable(scrollable bool) {
t.Lock()
defer t.Unlock()
t.scrollable = scrollable
if !scrollable {
t.trackEnd = true
}
}
// SetScrollBarVisibility specifies the display of the scroll bar.
func (t *TextView) SetScrollBarVisibility(visibility ScrollBarVisibility) {
t.Lock()
defer t.Unlock()
t.scrollBarVisibility = visibility
}
// SetScrollBarColor sets the color of the scroll bar.
func (t *TextView) SetScrollBarColor(color tcell.Color) {
t.Lock()
defer t.Unlock()
t.scrollBarColor = color
}
// 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) {
t.Lock()
defer t.Unlock()
if t.wrap != wrap {
t.index = nil
}
t.wrap = wrap
}
// SetWordWrap sets the flag that, if true and if the "wrap" flag is also true
// (see SetWrap()), wraps the line at spaces or after punctuation marks. Note
// that trailing spaces will not be printed.
//
// This flag is ignored if the "wrap" flag is false.
func (t *TextView) SetWordWrap(wrapOnWords bool) {
t.Lock()
defer t.Unlock()
if t.wordWrap != wrapOnWords {
t.index = nil
}
t.wordWrap = wrapOnWords
}
// SetTextAlign sets the horizontal alignment of the text. This must be either
// AlignLeft, AlignCenter, or AlignRight.
func (t *TextView) SetTextAlign(align int) {
t.Lock()
defer t.Unlock()
if t.align != align {
t.index = nil
}
t.align = align
}
// SetVerticalAlign sets the vertical alignment of the text. This must be
// either AlignTop, AlignMiddle, or AlignBottom.
func (t *TextView) SetVerticalAlign(valign VerticalAlignment) {
t.Lock()
defer t.Unlock()
if t.valign != valign {
t.index = nil
}
t.valign = valign
}
// 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) {
t.Lock()
defer t.Unlock()
t.textColor = color
}
// SetHighlightForegroundColor sets the foreground color of highlighted text.
func (t *TextView) SetHighlightForegroundColor(color tcell.Color) {
t.Lock()
defer t.Unlock()
t.highlightForeground = color
}
// SetHighlightBackgroundColor sets the foreground color of highlighted text.
func (t *TextView) SetHighlightBackgroundColor(color tcell.Color) {
t.Lock()
defer t.Unlock()
t.highlightBackground = color
}
// SetBytes sets the text of this text view to the provided byte slice.
// Previously contained text will be removed.
func (t *TextView) SetBytes(text []byte) {
t.Lock()
defer t.Unlock()
t.clear()
t.write(text)
}
// SetText sets the text of this text view to the provided string. Previously
// contained text will be removed.
func (t *TextView) SetText(text string) {
t.SetBytes([]byte(text))
}
// GetBytes returns the current text of this text view. If "stripTags" is set
// to true, any region/color tags are stripped from the text.
func (t *TextView) GetBytes(stripTags bool) []byte {
t.RLock()
defer t.RUnlock()
if !stripTags {
if len(t.recentBytes) > 0 {
return bytes.Join(append(t.buffer, t.recentBytes), []byte("\n"))
}
return bytes.Join(t.buffer, []byte("\n"))
}
buffer := bytes.Join(t.buffer, []byte("\n"))
return StripTags(buffer, t.dynamicColors, t.regions)
}
// GetText returns the current text of this text view. If "stripTags" is set
// to true, any region/color tags are stripped from the text.
func (t *TextView) GetText(stripTags bool) string {
return string(t.GetBytes(stripTags))
}
// GetBufferSize returns the number of lines and the length of the longest line
// in the text buffer. The screen size of the widget is available via GetRect.
func (t *TextView) GetBufferSize() (rows int, maxLen int) {
t.RLock()
defer t.RUnlock()
return len(t.buffer), t.longestLine
}
// SetDynamicColors sets the flag that allows the text color to be changed
// dynamically. See class description for details.
func (t *TextView) SetDynamicColors(dynamic bool) {
t.Lock()
defer t.Unlock()
if t.dynamicColors != dynamic {
t.index = nil
}
t.dynamicColors = dynamic
}
// SetRegions sets the flag that allows to define regions in the text. See class
// description for details.
func (t *TextView) SetRegions(regions bool) {
t.Lock()
defer t.Unlock()
if t.regions != regions {
t.index = nil
}
t.regions = regions
}
// SetChangedFunc sets a handler function which is called when the text of the
// text view has changed. This is useful when text is written to this io.Writer
// in a separate goroutine. Doing so does not automatically cause the screen to
// be refreshed so you may want to use the "changed" handler to redraw the
// screen.
//
// Note that to avoid race conditions or deadlocks, there are a few rules you
// should follow:
//
// - You can call Application.Draw() from this handler.
// - You can call TextView.HasFocus() from this handler.
// - During the execution of this handler, access to any other variables from
// this primitive or any other primitive should be queued using
// Application.QueueUpdate().
//
// See package description for details on dealing with concurrency.
func (t *TextView) SetChangedFunc(handler func()) {
t.Lock()
defer t.Unlock()
t.changed = handler
}
// 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)) {
t.Lock()
defer t.Unlock()
t.done = handler
}
// SetHighlightedFunc sets a handler which is called when the list of currently
// highlighted regions change. It receives a list of region IDs which were newly
// highlighted, those that are not highlighted anymore, and those that remain
// highlighted.
//
// Note that because regions are only determined during drawing, this function
// can only fire for regions that have existed during the last call to Draw().
func (t *TextView) SetHighlightedFunc(handler func(added, removed, remaining []string)) {
t.highlighted = handler
}
func (t *TextView) clipBuffer() {
if t.maxLines <= 0 {
return
}
lenbuf := len(t.buffer)
if lenbuf > t.maxLines {
t.buffer = t.buffer[lenbuf-t.maxLines:]
}
}
// SetMaxLines sets the maximum number of newlines the text view will hold
// before discarding older data from the buffer.
func (t *TextView) SetMaxLines(maxLines int) {
t.maxLines = maxLines
t.clipBuffer()
}
// ScrollTo scrolls to the specified row and column (both starting with 0).
func (t *TextView) ScrollTo(row, column int) {
t.Lock()
defer t.Unlock()
if !t.scrollable {
return
}
t.lineOffset = row
t.columnOffset = column
t.trackEnd = false
}
// ScrollToBeginning scrolls to the top left corner of the text if the text view
// is scrollable.
func (t *TextView) ScrollToBeginning() {
t.Lock()
defer t.Unlock()
if !t.scrollable {
return
}
t.trackEnd = false
t.lineOffset = 0
t.columnOffset = 0
}
// ScrollToEnd scrolls to the bottom left corner of the text if the text view
// is scrollable. Adding new rows to the end of the text view will cause it to
// scroll with the new data.
func (t *TextView) ScrollToEnd() {
t.Lock()
defer t.Unlock()
if !t.scrollable {
return
}
t.trackEnd = true
t.columnOffset = 0
}
// GetScrollOffset returns the number of rows and columns that are skipped at
// the top left corner when the text view has been scrolled.
func (t *TextView) GetScrollOffset() (row, column int) {
t.RLock()
defer t.RUnlock()
return t.lineOffset, t.columnOffset
}
// Clear removes all text from the buffer.
func (t *TextView) Clear() {
t.Lock()
defer t.Unlock()
t.clear()
}
func (t *TextView) clear() {
t.buffer = nil
t.recentBytes = nil
if t.reindex {
t.index = nil
}
}
// Highlight specifies which regions should be highlighted. If highlight
// toggling is set to true (see SetToggleHighlights()), the highlight of the
// provided regions is toggled (highlighted regions are un-highlighted and vice
// versa). If toggling is set to false, the provided regions are highlighted and
// all other regions will not be highlighted (you may also provide nil to turn
// off all highlights).
//
// For more information on regions, see class description. Empty region strings
// are ignored.
//
// Text in highlighted regions will be drawn inverted, i.e. with their
// background and foreground colors swapped.
func (t *TextView) Highlight(regionIDs ...string) {
t.Lock()
// Toggle highlights.
if t.toggleHighlights {
var newIDs []string
HighlightLoop:
for regionID := range t.highlights {
for _, id := range regionIDs {
if regionID == id {
continue HighlightLoop
}
}
newIDs = append(newIDs, regionID)
}
for _, regionID := range regionIDs {
if _, ok := t.highlights[regionID]; !ok {
newIDs = append(newIDs, regionID)
}
}
regionIDs = newIDs
} // Now we have a list of region IDs that end up being highlighted.
// Determine added and removed regions.
var added, removed, remaining []string
if t.highlighted != nil {
for _, regionID := range regionIDs {
if _, ok := t.highlights[regionID]; ok {
remaining = append(remaining, regionID)
delete(t.highlights, regionID)
} else {
added = append(added, regionID)
}
}
for regionID := range t.highlights {
removed = append(removed, regionID)
}
}
// Make new selection.
t.highlights = make(map[string]struct{})
for _, id := range regionIDs {
if id == "" {
continue
}
t.highlights[id] = struct{}{}
}
t.index = nil
// Notify.
if t.highlighted != nil && (len(added) > 0 || len(removed) > 0) {
t.Unlock()
t.highlighted(added, removed, remaining)
} else {
t.Unlock()
}
}
// GetHighlights returns the IDs of all currently highlighted regions.
func (t *TextView) GetHighlights() (regionIDs []string) {
t.RLock()
defer t.RUnlock()
for id := range t.highlights {
regionIDs = append(regionIDs, id)
}
return
}
// SetToggleHighlights sets a flag to determine how regions are highlighted.
// When set to true, the Highlight() function (or a mouse click) will toggle the
// provided/selected regions. When set to false, Highlight() (or a mouse click)
// will simply highlight the provided regions.
func (t *TextView) SetToggleHighlights(toggle bool) {
t.toggleHighlights = toggle
}
// 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() {
t.Lock()
defer t.Unlock()
if len(t.highlights) == 0 || !t.scrollable || !t.regions {
return
}
t.index = nil
t.scrollToHighlights = true
t.trackEnd = false
}
// 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 {
t.RLock()
defer t.RUnlock()
if !t.regions || len(regionID) == 0 {
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.FindAllIndex(str, -1)
}
// Find all regions in this line.
var (
regionIndices [][]int
regions [][][]byte
)
if t.regions {
regionIndices = regionPattern.FindAllIndex(str, -1)
regions = regionPattern.FindAllSubmatch(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++
}
if colorTagIndices[currentTag][1]-colorTagIndices[currentTag][0] > 2 {
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 = string(regions[currentRegion][1])
currentRegion++
}
continue
}
// Add this rune.
if currentRegionID == regionID {
buffer.WriteByte(ch)
}
}
// Add newline.
if currentRegionID == regionID {
buffer.WriteRune('\n')
}
}
return escapePattern.ReplaceAllString(buffer.String(), `[$1$2]`)
}
// Focus is called when this primitive receives focus.
func (t *TextView) Focus(delegate func(p Primitive)) {
t.Lock()
defer t.Unlock()
// Implemented here with locking because this is used by layout primitives.
t.hasFocus = true
}
// HasFocus returns whether or not this primitive has focus.
func (t *TextView) HasFocus() bool {
t.RLock()
defer t.RUnlock()
// Implemented here with locking because this may be used in the "changed"
// callback.
return t.hasFocus
}
// Write lets us implement the io.Writer interface. Tab characters will be
// replaced with TabSize space characters. A "\n" or "\r\n" will be interpreted
// as a new line.
func (t *TextView) Write(p []byte) (n int, err error) {
t.Lock()
changed := t.changed
if changed != nil {
// Notify at the end.
defer changed()
}
defer t.Unlock()
return t.write(p)
}
func (t *TextView) write(p []byte) (n int, err error) {
// 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 {
location := openColorRegex.FindIndex(newBytes)
if location != nil {
t.recentBytes = newBytes[location[0]:]
newBytes = newBytes[:location[0]]
}
}
// If we have a trailing open region, exclude it.
if t.regions {
location := openRegionRegex.FindIndex(newBytes)
if location != nil {
t.recentBytes = newBytes[location[0]:]
newBytes = newBytes[:location[0]]
}
}
// Transform the new bytes into strings.
newBytes = bytes.Replace(newBytes, []byte{'\t'}, bytes.Repeat([]byte{' '}, TabSize), -1)
for index, line := range bytes.Split(newBytes, []byte("\n")) {
if index == 0 {
if len(t.buffer) == 0 {
t.buffer = [][]byte{line}
} else {
t.buffer[len(t.buffer)-1] = append(t.buffer[len(t.buffer)-1], line...)
}
} else {
t.buffer = append(t.buffer, line)
}
}
t.clipBuffer()
// Reset the index.