Source file src/code.rocketnine.space/tslocum/cview/textview.go

Documentation: code.rocketnine.space/tslocum/cview

     1  package cview
     2  
     3  import (
     4  	"bytes"
     5  	"regexp"
     6  	"sync"
     7  	"unicode"
     8  	"unicode/utf8"
     9  
    10  	"github.com/gdamore/tcell/v2"
    11  	"github.com/lucasb-eyer/go-colorful"
    12  	"github.com/mattn/go-runewidth"
    13  	"github.com/rivo/uniseg"
    14  )
    15  
    16  var (
    17  	// TabSize is the number of spaces with which a tab character will be replaced.
    18  	TabSize = 4
    19  )
    20  
    21  var (
    22  	openColorRegex  = regexp.MustCompile(`\[([a-zA-Z]*|#[0-9a-zA-Z]*)$`)
    23  	openRegionRegex = regexp.MustCompile(`\["[a-zA-Z0-9_,;: \-\.]*"?$`)
    24  )
    25  
    26  // textViewIndex contains information about each line displayed in the text
    27  // view.
    28  type textViewIndex struct {
    29  	Line            int    // The index into the "buffer" variable.
    30  	Pos             int    // The index into the "buffer" line ([]byte position).
    31  	NextPos         int    // The (byte) index of the next character in this buffer line.
    32  	Width           int    // The screen width of this line.
    33  	ForegroundColor string // The starting foreground color ("" = don't change, "-" = reset).
    34  	BackgroundColor string // The starting background color ("" = don't change, "-" = reset).
    35  	Attributes      string // The starting attributes ("" = don't change, "-" = reset).
    36  	Region          []byte // The starting region ID.
    37  }
    38  
    39  // textViewRegion contains information about a region.
    40  type textViewRegion struct {
    41  	// The region ID.
    42  	ID []byte
    43  
    44  	// The starting and end screen position of the region as determined the last
    45  	// time Draw() was called. A negative value indicates out-of-rect positions.
    46  	FromX, FromY, ToX, ToY int
    47  }
    48  
    49  // TextView is a box which displays text. It implements the io.Writer interface
    50  // so you can stream text to it. This does not trigger a redraw automatically
    51  // but if a handler is installed via SetChangedFunc(), you can cause it to be
    52  // redrawn. (See SetChangedFunc() for more details.)
    53  //
    54  // Navigation
    55  //
    56  // If the text view is scrollable (the default), text is kept in a buffer which
    57  // may be larger than the screen and can be navigated similarly to Vim:
    58  //
    59  //   - h, left arrow: Move left.
    60  //   - l, right arrow: Move right.
    61  //   - j, down arrow: Move down.
    62  //   - k, up arrow: Move up.
    63  //   - g, home: Move to the top.
    64  //   - G, end: Move to the bottom.
    65  //   - Ctrl-F, page down: Move down by one page.
    66  //   - Ctrl-B, page up: Move up by one page.
    67  //
    68  // If the text is not scrollable, any text above the top visible line is
    69  // discarded.
    70  //
    71  // Use SetInputCapture() to override or modify keyboard input.
    72  //
    73  // Colors
    74  //
    75  // If dynamic colors are enabled via SetDynamicColors(), text color can be
    76  // changed dynamically by embedding color strings in square brackets. This works
    77  // the same way as anywhere else. Please see the package documentation for more
    78  // information.
    79  //
    80  // Regions and Highlights
    81  //
    82  // If regions are enabled via SetRegions(), you can define text regions within
    83  // the text and assign region IDs to them. Text regions start with region tags.
    84  // Region tags are square brackets that contain a region ID in double quotes,
    85  // for example:
    86  //
    87  //   We define a ["rg"]region[""] here.
    88  //
    89  // A text region ends with the next region tag. Tags with no region ID ([""])
    90  // don't start new regions. They can therefore be used to mark the end of a
    91  // region. Region IDs must satisfy the following regular expression:
    92  //
    93  //   [a-zA-Z0-9_,;: \-\.]+
    94  //
    95  // Regions can be highlighted by calling the Highlight() function with one or
    96  // more region IDs. This can be used to display search results, for example.
    97  //
    98  // The ScrollToHighlight() function can be used to jump to the currently
    99  // highlighted region once when the text view is drawn the next time.
   100  type TextView struct {
   101  	*Box
   102  
   103  	// The text buffer.
   104  	buffer [][]byte
   105  
   106  	// The last bytes that have been received but are not part of the buffer yet.
   107  	recentBytes []byte
   108  
   109  	// The last width and height of the text view.
   110  	lastWidth, lastHeight int
   111  
   112  	// The processed line index. This is nil if the buffer has changed and needs
   113  	// to be re-indexed.
   114  	index []*textViewIndex
   115  
   116  	// The width of the text view buffer index.
   117  	indexWidth int
   118  
   119  	// If set to true, the buffer will be reindexed each time it is modified.
   120  	reindex bool
   121  
   122  	// The horizontal text alignment, one of AlignLeft, AlignCenter, or AlignRight.
   123  	align int
   124  
   125  	// The vertical text alignment, one of AlignTop, AlignMiddle, or AlignBottom.
   126  	valign VerticalAlignment
   127  
   128  	// Information about visible regions as of the last call to Draw().
   129  	regionInfos []*textViewRegion
   130  
   131  	// Indices into the "index" slice which correspond to the first line of the
   132  	// first highlight and the last line of the last highlight. This is calculated
   133  	// during re-indexing. Set to -1 if there is no current highlight.
   134  	fromHighlight, toHighlight int
   135  
   136  	// The screen space column of the highlight in its first line. Set to -1 if
   137  	// there is no current highlight.
   138  	posHighlight int
   139  
   140  	// A set of region IDs that are currently highlighted.
   141  	highlights map[string]struct{}
   142  
   143  	// The screen width of the longest line in the index (not the buffer).
   144  	longestLine int
   145  
   146  	// The index of the first line shown in the text view.
   147  	lineOffset int
   148  
   149  	// The maximum number of newlines the text view will hold (0 = unlimited).
   150  	maxLines int
   151  
   152  	// If set to true, the text view will always remain at the end of the content.
   153  	trackEnd bool
   154  
   155  	// The number of characters to be skipped on each line (not in wrap mode).
   156  	columnOffset int
   157  
   158  	// The height of the content the last time the text view was drawn.
   159  	pageSize int
   160  
   161  	// If set to true, the text view will keep a buffer of text which can be
   162  	// navigated when the text is longer than what fits into the box.
   163  	scrollable bool
   164  
   165  	// Visibility of the scroll bar.
   166  	scrollBarVisibility ScrollBarVisibility
   167  
   168  	// The scroll bar color.
   169  	scrollBarColor tcell.Color
   170  
   171  	// If set to true, lines that are longer than the available width are wrapped
   172  	// onto the next line. If set to false, any characters beyond the available
   173  	// width are discarded.
   174  	wrap bool
   175  
   176  	// The maximum line width when wrapping (0 = use TextView width).
   177  	wrapWidth int
   178  
   179  	// If set to true and if wrap is also true, lines are split at spaces or
   180  	// after punctuation characters.
   181  	wordWrap bool
   182  
   183  	// The (starting) color of the text.
   184  	textColor tcell.Color
   185  
   186  	// The foreground color of highlighted text.
   187  	highlightForeground tcell.Color
   188  
   189  	// The background color of highlighted text.
   190  	highlightBackground tcell.Color
   191  
   192  	// If set to true, the text color can be changed dynamically by piping color
   193  	// strings in square brackets to the text view.
   194  	dynamicColors bool
   195  
   196  	// If set to true, region tags can be used to define regions.
   197  	regions bool
   198  
   199  	// A temporary flag which, when true, will automatically bring the current
   200  	// highlight(s) into the visible screen.
   201  	scrollToHighlights bool
   202  
   203  	// If true, setting new highlights will be a XOR instead of an overwrite
   204  	// operation.
   205  	toggleHighlights bool
   206  
   207  	// An optional function which is called when the content of the text view has
   208  	// changed.
   209  	changed func()
   210  
   211  	// An optional function which is called when the user presses one of the
   212  	// following keys: Escape, Enter, Tab, Backtab.
   213  	done func(tcell.Key)
   214  
   215  	// An optional function which is called when one or more regions were
   216  	// highlighted.
   217  	highlighted func(added, removed, remaining []string)
   218  
   219  	sync.RWMutex
   220  }
   221  
   222  // NewTextView returns a new text view.
   223  func NewTextView() *TextView {
   224  	return &TextView{
   225  		Box:                 NewBox(),
   226  		highlights:          make(map[string]struct{}),
   227  		lineOffset:          -1,
   228  		reindex:             true,
   229  		scrollable:          true,
   230  		scrollBarVisibility: ScrollBarAuto,
   231  		scrollBarColor:      Styles.ScrollBarColor,
   232  		align:               AlignLeft,
   233  		valign:              AlignTop,
   234  		wrap:                true,
   235  		textColor:           Styles.PrimaryTextColor,
   236  		highlightForeground: Styles.PrimitiveBackgroundColor,
   237  		highlightBackground: Styles.PrimaryTextColor,
   238  	}
   239  }
   240  
   241  // SetScrollable sets the flag that decides whether or not the text view is
   242  // scrollable. If true, text is kept in a buffer and can be navigated. If false,
   243  // the last line will always be visible.
   244  func (t *TextView) SetScrollable(scrollable bool) {
   245  	t.Lock()
   246  	defer t.Unlock()
   247  
   248  	t.scrollable = scrollable
   249  	if !scrollable {
   250  		t.trackEnd = true
   251  	}
   252  }
   253  
   254  // SetScrollBarVisibility specifies the display of the scroll bar.
   255  func (t *TextView) SetScrollBarVisibility(visibility ScrollBarVisibility) {
   256  	t.Lock()
   257  	defer t.Unlock()
   258  
   259  	t.scrollBarVisibility = visibility
   260  }
   261  
   262  // SetScrollBarColor sets the color of the scroll bar.
   263  func (t *TextView) SetScrollBarColor(color tcell.Color) {
   264  	t.Lock()
   265  	defer t.Unlock()
   266  
   267  	t.scrollBarColor = color
   268  }
   269  
   270  // SetWrap sets the flag that, if true, leads to lines that are longer than the
   271  // available width being wrapped onto the next line. If false, any characters
   272  // beyond the available width are not displayed.
   273  func (t *TextView) SetWrap(wrap bool) {
   274  	t.Lock()
   275  	defer t.Unlock()
   276  
   277  	if t.wrap != wrap {
   278  		t.index = nil
   279  	}
   280  	t.wrap = wrap
   281  }
   282  
   283  // SetWordWrap sets the flag that, if true and if the "wrap" flag is also true
   284  // (see SetWrap()), wraps the line at spaces or after punctuation marks. Note
   285  // that trailing spaces will not be printed.
   286  //
   287  // This flag is ignored if the "wrap" flag is false.
   288  func (t *TextView) SetWordWrap(wrapOnWords bool) {
   289  	t.Lock()
   290  	defer t.Unlock()
   291  
   292  	if t.wordWrap != wrapOnWords {
   293  		t.index = nil
   294  	}
   295  	t.wordWrap = wrapOnWords
   296  }
   297  
   298  // SetTextAlign sets the horizontal alignment of the text. This must be either
   299  // AlignLeft, AlignCenter, or AlignRight.
   300  func (t *TextView) SetTextAlign(align int) {
   301  	t.Lock()
   302  	defer t.Unlock()
   303  
   304  	if t.align != align {
   305  		t.index = nil
   306  	}
   307  	t.align = align
   308  }
   309  
   310  // SetVerticalAlign sets the vertical alignment of the text. This must be
   311  // either AlignTop, AlignMiddle, or AlignBottom.
   312  func (t *TextView) SetVerticalAlign(valign VerticalAlignment) {
   313  	t.Lock()
   314  	defer t.Unlock()
   315  
   316  	if t.valign != valign {
   317  		t.index = nil
   318  	}
   319  	t.valign = valign
   320  }
   321  
   322  // SetTextColor sets the initial color of the text (which can be changed
   323  // dynamically by sending color strings in square brackets to the text view if
   324  // dynamic colors are enabled).
   325  func (t *TextView) SetTextColor(color tcell.Color) {
   326  	t.Lock()
   327  	defer t.Unlock()
   328  
   329  	t.textColor = color
   330  }
   331  
   332  // SetHighlightForegroundColor sets the foreground color of highlighted text.
   333  func (t *TextView) SetHighlightForegroundColor(color tcell.Color) {
   334  	t.Lock()
   335  	defer t.Unlock()
   336  
   337  	t.highlightForeground = color
   338  }
   339  
   340  // SetHighlightBackgroundColor sets the foreground color of highlighted text.
   341  func (t *TextView) SetHighlightBackgroundColor(color tcell.Color) {
   342  	t.Lock()
   343  	defer t.Unlock()
   344  
   345  	t.highlightBackground = color
   346  }
   347  
   348  // SetBytes sets the text of this text view to the provided byte slice.
   349  // Previously contained text will be removed.
   350  func (t *TextView) SetBytes(text []byte) {
   351  	t.Lock()
   352  	defer t.Unlock()
   353  
   354  	t.clear()
   355  	t.write(text)
   356  }
   357  
   358  // SetText sets the text of this text view to the provided string. Previously
   359  // contained text will be removed.
   360  func (t *TextView) SetText(text string) {
   361  	t.SetBytes([]byte(text))
   362  }
   363  
   364  // GetBytes returns the current text of this text view. If "stripTags" is set
   365  // to true, any region/color tags are stripped from the text.
   366  func (t *TextView) GetBytes(stripTags bool) []byte {
   367  	t.RLock()
   368  	defer t.RUnlock()
   369  
   370  	if !stripTags {
   371  		if len(t.recentBytes) > 0 {
   372  			return bytes.Join(append(t.buffer, t.recentBytes), []byte("\n"))
   373  		}
   374  		return bytes.Join(t.buffer, []byte("\n"))
   375  	}
   376  
   377  	buffer := bytes.Join(t.buffer, []byte("\n"))
   378  	return StripTags(buffer, t.dynamicColors, t.regions)
   379  }
   380  
   381  // GetText returns the current text of this text view. If "stripTags" is set
   382  // to true, any region/color tags are stripped from the text.
   383  func (t *TextView) GetText(stripTags bool) string {
   384  	return string(t.GetBytes(stripTags))
   385  }
   386  
   387  // GetBufferSize returns the number of lines and the length of the longest line
   388  // in the text buffer. The screen size of the widget is available via GetRect.
   389  func (t *TextView) GetBufferSize() (rows int, maxLen int) {
   390  	t.RLock()
   391  	defer t.RUnlock()
   392  
   393  	return len(t.buffer), t.longestLine
   394  }
   395  
   396  // SetDynamicColors sets the flag that allows the text color to be changed
   397  // dynamically. See class description for details.
   398  func (t *TextView) SetDynamicColors(dynamic bool) {
   399  	t.Lock()
   400  	defer t.Unlock()
   401  
   402  	if t.dynamicColors != dynamic {
   403  		t.index = nil
   404  	}
   405  	t.dynamicColors = dynamic
   406  }
   407  
   408  // SetRegions sets the flag that allows to define regions in the text. See class
   409  // description for details.
   410  func (t *TextView) SetRegions(regions bool) {
   411  	t.Lock()
   412  	defer t.Unlock()
   413  
   414  	if t.regions != regions {
   415  		t.index = nil
   416  	}
   417  	t.regions = regions
   418  }
   419  
   420  // SetChangedFunc sets a handler function which is called when the text of the
   421  // text view has changed. This is useful when text is written to this io.Writer
   422  // in a separate goroutine. Doing so does not automatically cause the screen to
   423  // be refreshed so you may want to use the "changed" handler to redraw the
   424  // screen.
   425  //
   426  // Note that to avoid race conditions or deadlocks, there are a few rules you
   427  // should follow:
   428  //
   429  //   - You can call Application.Draw() from this handler.
   430  //   - You can call TextView.HasFocus() from this handler.
   431  //   - During the execution of this handler, access to any other variables from
   432  //     this primitive or any other primitive should be queued using
   433  //     Application.QueueUpdate().
   434  //
   435  // See package description for details on dealing with concurrency.
   436  func (t *TextView) SetChangedFunc(handler func()) {
   437  	t.Lock()
   438  	defer t.Unlock()
   439  
   440  	t.changed = handler
   441  }
   442  
   443  // SetDoneFunc sets a handler which is called when the user presses on the
   444  // following keys: Escape, Enter, Tab, Backtab. The key is passed to the
   445  // handler.
   446  func (t *TextView) SetDoneFunc(handler func(key tcell.Key)) {
   447  	t.Lock()
   448  	defer t.Unlock()
   449  
   450  	t.done = handler
   451  }
   452  
   453  // SetHighlightedFunc sets a handler which is called when the list of currently
   454  // highlighted regions change. It receives a list of region IDs which were newly
   455  // highlighted, those that are not highlighted anymore, and those that remain
   456  // highlighted.
   457  //
   458  // Note that because regions are only determined during drawing, this function
   459  // can only fire for regions that have existed during the last call to Draw().
   460  func (t *TextView) SetHighlightedFunc(handler func(added, removed, remaining []string)) {
   461  	t.highlighted = handler
   462  }
   463  
   464  func (t *TextView) clipBuffer() {
   465  	if t.maxLines <= 0 {
   466  		return
   467  	}
   468  
   469  	lenbuf := len(t.buffer)
   470  	if lenbuf > t.maxLines {
   471  		t.buffer = t.buffer[lenbuf-t.maxLines:]
   472  	}
   473  }
   474  
   475  // SetMaxLines sets the maximum number of newlines the text view will hold
   476  // before discarding older data from the buffer.
   477  func (t *TextView) SetMaxLines(maxLines int) {
   478  	t.maxLines = maxLines
   479  	t.clipBuffer()
   480  }
   481  
   482  // ScrollTo scrolls to the specified row and column (both starting with 0).
   483  func (t *TextView) ScrollTo(row, column int) {
   484  	t.Lock()
   485  	defer t.Unlock()
   486  
   487  	if !t.scrollable {
   488  		return
   489  	}
   490  	t.lineOffset = row
   491  	t.columnOffset = column
   492  	t.trackEnd = false
   493  }
   494  
   495  // ScrollToBeginning scrolls to the top left corner of the text if the text view
   496  // is scrollable.
   497  func (t *TextView) ScrollToBeginning() {
   498  	t.Lock()
   499  	defer t.Unlock()
   500  
   501  	if !t.scrollable {
   502  		return
   503  	}
   504  	t.trackEnd = false
   505  	t.lineOffset = 0
   506  	t.columnOffset = 0
   507  }
   508  
   509  // ScrollToEnd scrolls to the bottom left corner of the text if the text view
   510  // is scrollable. Adding new rows to the end of the text view will cause it to
   511  // scroll with the new data.
   512  func (t *TextView) ScrollToEnd() {
   513  	t.Lock()
   514  	defer t.Unlock()
   515  
   516  	if !t.scrollable {
   517  		return
   518  	}
   519  	t.trackEnd = true
   520  	t.columnOffset = 0
   521  }
   522  
   523  // GetScrollOffset returns the number of rows and columns that are skipped at
   524  // the top left corner when the text view has been scrolled.
   525  func (t *TextView) GetScrollOffset() (row, column int) {
   526  	t.RLock()
   527  	defer t.RUnlock()
   528  
   529  	return t.lineOffset, t.columnOffset
   530  }
   531  
   532  // Clear removes all text from the buffer.
   533  func (t *TextView) Clear() {
   534  	t.Lock()
   535  	defer t.Unlock()
   536  
   537  	t.clear()
   538  }
   539  
   540  func (t *TextView) clear() {
   541  	t.buffer = nil
   542  	t.recentBytes = nil
   543  	if t.reindex {
   544  		t.index = nil
   545  	}
   546  }
   547  
   548  // Highlight specifies which regions should be highlighted. If highlight
   549  // toggling is set to true (see SetToggleHighlights()), the highlight of the
   550  // provided regions is toggled (highlighted regions are un-highlighted and vice
   551  // versa). If toggling is set to false, the provided regions are highlighted and
   552  // all other regions will not be highlighted (you may also provide nil to turn
   553  // off all highlights).
   554  //
   555  // For more information on regions, see class description. Empty region strings
   556  // are ignored.
   557  //
   558  // Text in highlighted regions will be drawn inverted, i.e. with their
   559  // background and foreground colors swapped.
   560  func (t *TextView) Highlight(regionIDs ...string) {
   561  	t.Lock()
   562  
   563  	// Toggle highlights.
   564  	if t.toggleHighlights {
   565  		var newIDs []string
   566  	HighlightLoop:
   567  		for regionID := range t.highlights {
   568  			for _, id := range regionIDs {
   569  				if regionID == id {
   570  					continue HighlightLoop
   571  				}
   572  			}
   573  			newIDs = append(newIDs, regionID)
   574  		}
   575  		for _, regionID := range regionIDs {
   576  			if _, ok := t.highlights[regionID]; !ok {
   577  				newIDs = append(newIDs, regionID)
   578  			}
   579  		}
   580  		regionIDs = newIDs
   581  	} // Now we have a list of region IDs that end up being highlighted.
   582  
   583  	// Determine added and removed regions.
   584  	var added, removed, remaining []string
   585  	if t.highlighted != nil {
   586  		for _, regionID := range regionIDs {
   587  			if _, ok := t.highlights[regionID]; ok {
   588  				remaining = append(remaining, regionID)
   589  				delete(t.highlights, regionID)
   590  			} else {
   591  				added = append(added, regionID)
   592  			}
   593  		}
   594  		for regionID := range t.highlights {
   595  			removed = append(removed, regionID)
   596  		}
   597  	}
   598  
   599  	// Make new selection.
   600  	t.highlights = make(map[string]struct{})
   601  	for _, id := range regionIDs {
   602  		if id == "" {
   603  			continue
   604  		}
   605  		t.highlights[id] = struct{}{}
   606  	}
   607  	t.index = nil
   608  
   609  	// Notify.
   610  	if t.highlighted != nil && (len(added) > 0 || len(removed) > 0) {
   611  		t.Unlock()
   612  		t.highlighted(added, removed, remaining)
   613  	} else {
   614  		t.Unlock()
   615  	}
   616  }
   617  
   618  // GetHighlights returns the IDs of all currently highlighted regions.
   619  func (t *TextView) GetHighlights() (regionIDs []string) {
   620  	t.RLock()
   621  	defer t.RUnlock()
   622  
   623  	for id := range t.highlights {
   624  		regionIDs = append(regionIDs, id)
   625  	}
   626  	return
   627  }
   628  
   629  // SetToggleHighlights sets a flag to determine how regions are highlighted.
   630  // When set to true, the Highlight() function (or a mouse click) will toggle the
   631  // provided/selected regions. When set to false, Highlight() (or a mouse click)
   632  // will simply highlight the provided regions.
   633  func (t *TextView) SetToggleHighlights(toggle bool) {
   634  	t.toggleHighlights = toggle
   635  }
   636  
   637  // ScrollToHighlight will cause the visible area to be scrolled so that the
   638  // highlighted regions appear in the visible area of the text view. This
   639  // repositioning happens the next time the text view is drawn. It happens only
   640  // once so you will need to call this function repeatedly to always keep
   641  // highlighted regions in view.
   642  //
   643  // Nothing happens if there are no highlighted regions or if the text view is
   644  // not scrollable.
   645  func (t *TextView) ScrollToHighlight() {
   646  	t.Lock()
   647  	defer t.Unlock()
   648  
   649  	if len(t.highlights) == 0 || !t.scrollable || !t.regions {
   650  		return
   651  	}
   652  	t.index = nil
   653  	t.scrollToHighlights = true
   654  	t.trackEnd = false
   655  }
   656  
   657  // GetRegionText returns the text of the region with the given ID. If dynamic
   658  // colors are enabled, color tags are stripped from the text. Newlines are
   659  // always returned as '\n' runes.
   660  //
   661  // If the region does not exist or if regions are turned off, an empty string
   662  // is returned.
   663  func (t *TextView) GetRegionText(regionID string) string {
   664  	t.RLock()
   665  	defer t.RUnlock()
   666  
   667  	if !t.regions || len(regionID) == 0 {
   668  		return ""
   669  	}
   670  
   671  	var (
   672  		buffer          bytes.Buffer
   673  		currentRegionID string
   674  	)
   675  
   676  	for _, str := range t.buffer {
   677  		// Find all color tags in this line.
   678  		var colorTagIndices [][]int
   679  		if t.dynamicColors {
   680  			colorTagIndices = colorPattern.FindAllIndex(str, -1)
   681  		}
   682  
   683  		// Find all regions in this line.
   684  		var (
   685  			regionIndices [][]int
   686  			regions       [][][]byte
   687  		)
   688  		if t.regions {
   689  			regionIndices = regionPattern.FindAllIndex(str, -1)
   690  			regions = regionPattern.FindAllSubmatch(str, -1)
   691  		}
   692  
   693  		// Analyze this line.
   694  		var currentTag, currentRegion int
   695  		for pos, ch := range str {
   696  			// Skip any color tags.
   697  			if currentTag < len(colorTagIndices) && pos >= colorTagIndices[currentTag][0] && pos < colorTagIndices[currentTag][1] {
   698  				if pos == colorTagIndices[currentTag][1]-1 {
   699  					currentTag++
   700  					if currentTag == len(colorTagIndices) {
   701  						continue
   702  					}
   703  				}
   704  				if colorTagIndices[currentTag][1]-colorTagIndices[currentTag][0] > 2 {
   705  					continue
   706  				}
   707  			}
   708  
   709  			// Skip any regions.
   710  			if currentRegion < len(regionIndices) && pos >= regionIndices[currentRegion][0] && pos < regionIndices[currentRegion][1] {
   711  				if pos == regionIndices[currentRegion][1]-1 {
   712  					if currentRegionID == regionID {
   713  						// This is the end of the requested region. We're done.
   714  						return buffer.String()
   715  					}
   716  					currentRegionID = string(regions[currentRegion][1])
   717  					currentRegion++
   718  				}
   719  				continue
   720  			}
   721  
   722  			// Add this rune.
   723  			if currentRegionID == regionID {
   724  				buffer.WriteByte(ch)
   725  			}
   726  		}
   727  
   728  		// Add newline.
   729  		if currentRegionID == regionID {
   730  			buffer.WriteRune('\n')
   731  		}
   732  	}
   733  
   734  	return escapePattern.ReplaceAllString(buffer.String(), `[$1$2]`)
   735  }
   736  
   737  // Focus is called when this primitive receives focus.
   738  func (t *TextView) Focus(delegate func(p Primitive)) {
   739  	t.Lock()
   740  	defer t.Unlock()
   741  
   742  	// Implemented here with locking because this is used by layout primitives.
   743  	t.hasFocus = true
   744  }
   745  
   746  // HasFocus returns whether or not this primitive has focus.
   747  func (t *TextView) HasFocus() bool {
   748  	t.RLock()
   749  	defer t.RUnlock()
   750  
   751  	// Implemented here with locking because this may be used in the "changed"
   752  	// callback.
   753  	return t.hasFocus
   754  }
   755  
   756  // Write lets us implement the io.Writer interface. Tab characters will be
   757  // replaced with TabSize space characters. A "\n" or "\r\n" will be interpreted
   758  // as a new line.
   759  func (t *TextView) Write(p []byte) (n int, err error) {
   760  	t.Lock()
   761  	changed := t.changed
   762  	if changed != nil {
   763  		// Notify at the end.
   764  		defer changed()
   765  	}
   766  	defer t.Unlock()
   767  
   768  	return t.write(p)
   769  }
   770  
   771  func (t *TextView) write(p []byte) (n int, err error) {
   772  	// Copy data over.
   773  	newBytes := append(t.recentBytes, p...)
   774  	t.recentBytes = nil
   775  
   776  	// If we have a trailing invalid UTF-8 byte, we'll wait.
   777  	if r, _ := utf8.DecodeLastRune(p); r == utf8.RuneError {
   778  		t.recentBytes = newBytes
   779  		return len(p), nil
   780  	}
   781  
   782  	// If we have a trailing open dynamic color, exclude it.
   783  	if t.dynamicColors {
   784  		location := openColorRegex.FindIndex(newBytes)
   785  		if location != nil {
   786  			t.recentBytes = newBytes[location[0]:]
   787  			newBytes = newBytes[:location[0]]
   788  		}
   789  	}
   790  
   791  	// If we have a trailing open region, exclude it.
   792  	if t.regions {
   793  		location := openRegionRegex.FindIndex(newBytes)
   794  		if location != nil {
   795  			t.recentBytes = newBytes[location[0]:]
   796  			newBytes = newBytes[:location[0]]
   797  		}
   798  	}
   799  
   800  	// Transform the new bytes into strings.
   801  	newBytes = bytes.Replace(newBytes, []byte{'\t'}, bytes.Repeat([]byte{' '}, TabSize), -1)
   802  	for index, line := range bytes.Split(newBytes, []byte("\n")) {
   803  		if index == 0 {
   804  			if len(t.buffer) == 0 {
   805  				t.buffer = [][]byte{line}
   806  			} else {
   807  				t.buffer[len(t.buffer)-1] = append(t.buffer[len(t.buffer)-1], line...)
   808  			}
   809  		} else {
   810  			t.buffer = append(t.buffer, line)
   811  		}
   812  	}
   813  
   814  	t.clipBuffer()
   815  
   816  	// Reset the index.
   817  	if t.reindex {
   818  		t.index = nil
   819  	}
   820  
   821  	return len(p), nil
   822  }
   823  
   824  // SetWrapWidth set the maximum width of lines when wrapping is enabled.
   825  // When set to 0 the width of the TextView is used.
   826  func (t *TextView) SetWrapWidth(width int) {
   827  	t.Lock()
   828  	defer t.Unlock()
   829  
   830  	t.wrapWidth = width
   831  }
   832  
   833  // SetReindexBuffer set a flag controlling whether the buffer is reindexed when
   834  // it is modified. This improves the performance of TextViews whose contents
   835  // always have line-breaks in the same location. This must be called after the
   836  // buffer has been indexed.
   837  func (t *TextView) SetReindexBuffer(reindex bool) {
   838  	t.Lock()
   839  	defer t.Unlock()
   840  
   841  	t.reindex = reindex
   842  
   843  	if reindex {
   844  		t.index = nil
   845  	}
   846  }
   847  
   848  // reindexBuffer re-indexes the buffer such that we can use it to easily draw
   849  // the buffer onto the screen. Each line in the index will contain a pointer
   850  // into the buffer from which on we will print text. It will also contain the
   851  // color with which the line starts.
   852  func (t *TextView) reindexBuffer(width int) {
   853  	if t.index != nil && (!t.wrap || width == t.indexWidth) {
   854  		return // Nothing has changed. We can still use the current index.
   855  	}
   856  	t.index = nil
   857  	t.indexWidth = width
   858  	t.fromHighlight, t.toHighlight, t.posHighlight = -1, -1, -1
   859  
   860  	// If there's no space, there's no index.
   861  	if width < 1 {
   862  		return
   863  	}
   864  
   865  	if t.wrapWidth > 0 && t.wrapWidth < width {
   866  		width = t.wrapWidth
   867  	}
   868  
   869  	// Initial states.
   870  	var regionID []byte
   871  	var (
   872  		highlighted                                  bool
   873  		foregroundColor, backgroundColor, attributes string
   874  	)
   875  
   876  	// Go through each line in the buffer.
   877  	for bufferIndex, buf := range t.buffer {
   878  		colorTagIndices, colorTags, regionIndices, regions, escapeIndices, strippedStr, _ := decomposeText(buf, t.dynamicColors, t.regions)
   879  
   880  		// Split the line if required.
   881  		var splitLines []string
   882  		str := string(strippedStr)
   883  		if t.wrap && len(str) > 0 {
   884  			for len(str) > 0 {
   885  				extract := runewidth.Truncate(str, width, "")
   886  				if len(extract) == 0 {
   887  					// We'll extract at least one grapheme cluster.
   888  					gr := uniseg.NewGraphemes(str)
   889  					gr.Next()
   890  					_, to := gr.Positions()
   891  					extract = str[:to]
   892  				}
   893  				if t.wordWrap && len(extract) < len(str) {
   894  					// Add any spaces from the next line.
   895  					if spaces := spacePattern.FindStringIndex(str[len(extract):]); spaces != nil && spaces[0] == 0 {
   896  						extract = str[:len(extract)+spaces[1]]
   897  					}
   898  
   899  					// Can we split before the mandatory end?
   900  					matches := boundaryPattern.FindAllStringIndex(extract, -1)
   901  					if len(matches) > 0 {
   902  						// Yes. Let's split there.
   903  						extract = extract[:matches[len(matches)-1][1]]
   904  					}
   905  				}
   906  				splitLines = append(splitLines, extract)
   907  				str = str[len(extract):]
   908  			}
   909  		} else {
   910  			// No need to split the line.
   911  			splitLines = []string{str}
   912  		}
   913  
   914  		// Create index from split lines.
   915  		var originalPos, colorPos, regionPos, escapePos int
   916  		for _, splitLine := range splitLines {
   917  			line := &textViewIndex{
   918  				Line:            bufferIndex,
   919  				Pos:             originalPos,
   920  				ForegroundColor: foregroundColor,
   921  				BackgroundColor: backgroundColor,
   922  				Attributes:      attributes,
   923  				Region:          regionID,
   924  			}
   925  
   926  			// Shift original position with tags.
   927  			lineLength := len(splitLine)
   928  			remainingLength := lineLength
   929  			tagEnd := originalPos
   930  			totalTagLength := 0
   931  			for {
   932  				// Which tag comes next?
   933  				nextTag := make([][3]int, 0, 3)
   934  				if colorPos < len(colorTagIndices) {
   935  					nextTag = append(nextTag, [3]int{colorTagIndices[colorPos][0], colorTagIndices[colorPos][1], 0}) // 0 = color tag.
   936  				}
   937  				if regionPos < len(regionIndices) {
   938  					nextTag = append(nextTag, [3]int{regionIndices[regionPos][0], regionIndices[regionPos][1], 1}) // 1 = region tag.
   939  				}
   940  				if escapePos < len(escapeIndices) {
   941  					nextTag = append(nextTag, [3]int{escapeIndices[escapePos][0], escapeIndices[escapePos][1], 2}) // 2 = escape tag.
   942  				}
   943  				minPos := -1
   944  				tagIndex := -1
   945  				for index, pair := range nextTag {
   946  					if minPos < 0 || pair[0] < minPos {
   947  						minPos = pair[0]
   948  						tagIndex = index
   949  					}
   950  				}
   951  
   952  				// Is the next tag in range?
   953  				if tagIndex < 0 || minPos > tagEnd+remainingLength {
   954  					break // No. We're done with this line.
   955  				}
   956  
   957  				// Advance.
   958  				strippedTagStart := nextTag[tagIndex][0] - originalPos - totalTagLength
   959  				tagEnd = nextTag[tagIndex][1]
   960  				tagLength := tagEnd - nextTag[tagIndex][0]
   961  				if nextTag[tagIndex][2] == 2 {
   962  					tagLength = 1
   963  				}
   964  				totalTagLength += tagLength
   965  				remainingLength = lineLength - (tagEnd - originalPos - totalTagLength)
   966  
   967  				// Process the tag.
   968  				switch nextTag[tagIndex][2] {
   969  				case 0:
   970  					// Process color tags.
   971  					foregroundColor, backgroundColor, attributes = styleFromTag(foregroundColor, backgroundColor, attributes, colorTags[colorPos])
   972  					colorPos++
   973  				case 1:
   974  					// Process region tags.
   975  					regionID = regions[regionPos][1]
   976  					_, highlighted = t.highlights[string(regionID)]
   977  
   978  					// Update highlight range.
   979  					if highlighted {
   980  						line := len(t.index)
   981  						if t.fromHighlight < 0 {
   982  							t.fromHighlight, t.toHighlight = line, line
   983  							t.posHighlight = runewidth.StringWidth(splitLine[:strippedTagStart])
   984  						} else if line > t.toHighlight {
   985  							t.toHighlight = line
   986  						}
   987  					}
   988  
   989  					regionPos++
   990  				case 2:
   991  					// Process escape tags.
   992  					escapePos++
   993  				}
   994  			}
   995  
   996  			// Advance to next line.
   997  			originalPos += lineLength + totalTagLength
   998  
   999  			// Append this line.
  1000  			line.NextPos = originalPos
  1001  			line.Width = runewidth.StringWidth(splitLine)
  1002  			t.index = append(t.index, line)
  1003  		}
  1004  
  1005  		// Word-wrapped lines may have trailing whitespace. Remove it.
  1006  		if t.wrap && t.wordWrap {
  1007  			for _, line := range t.index {
  1008  				str := t.buffer[line.Line][line.Pos:line.NextPos]
  1009  				trimmed := bytes.TrimRightFunc(str, unicode.IsSpace)
  1010  				if len(trimmed) != len(str) {
  1011  					oldNextPos := line.NextPos
  1012  					line.NextPos -= len(str) - len(trimmed)
  1013  					line.Width -= runewidth.StringWidth(string(t.buffer[line.Line][line.NextPos:oldNextPos]))
  1014  				}
  1015  			}
  1016  		}
  1017  	}
  1018  
  1019  	// Calculate longest line.
  1020  	t.longestLine = 0
  1021  	for _, line := range t.index {
  1022  		if line.Width > t.longestLine {
  1023  			t.longestLine = line.Width
  1024  		}
  1025  	}
  1026  }
  1027  
  1028  // Draw draws this primitive onto the screen.
  1029  func (t *TextView) Draw(screen tcell.Screen) {
  1030  	if !t.GetVisible() {
  1031  		return
  1032  	}
  1033  
  1034  	t.Box.Draw(screen)
  1035  
  1036  	t.Lock()
  1037  	defer t.Unlock()
  1038  
  1039  	// Get the available size.
  1040  	x, y, width, height := t.GetInnerRect()
  1041  	if height == 0 {
  1042  		return
  1043  	}
  1044  	t.pageSize = height
  1045  
  1046  	if t.index == nil || width != t.lastWidth || height != t.lastHeight {
  1047  		t.reindexBuffer(width)
  1048  	}
  1049  	t.lastWidth, t.lastHeight = width, height
  1050  
  1051  	showVerticalScrollBar := t.scrollBarVisibility == ScrollBarAlways || (t.scrollBarVisibility == ScrollBarAuto && len(t.index) > height)
  1052  	if showVerticalScrollBar {
  1053  		width-- // Subtract space for scroll bar.
  1054  	}
  1055  
  1056  	t.reindexBuffer(width)
  1057  	if t.regions {
  1058  		t.regionInfos = nil
  1059  	}
  1060  
  1061  	// Draw scroll bar last.
  1062  	defer func() {
  1063  		if !showVerticalScrollBar {
  1064  			return
  1065  		}
  1066  
  1067  		items := len(t.index)
  1068  		cursor := int(float64(len(t.index)) * (float64(t.lineOffset) / float64(len(t.index)-height)))
  1069  
  1070  		// Render cursor at the bottom when tracking end
  1071  		if t.trackEnd && items <= height {
  1072  			items = height + 1
  1073  			cursor = height
  1074  		}
  1075  
  1076  		for printed := 0; printed < height; printed++ {
  1077  			RenderScrollBar(screen, t.scrollBarVisibility, x+width, y+printed, height, items, cursor, printed, t.hasFocus, t.scrollBarColor)
  1078  		}
  1079  	}()
  1080  
  1081  	// If we don't have an index, there's nothing to draw.
  1082  	if t.index == nil {
  1083  		return
  1084  	}
  1085  
  1086  	// Move to highlighted regions.
  1087  	if t.regions && t.scrollToHighlights && t.fromHighlight >= 0 {
  1088  		// Do we fit the entire height?
  1089  		if t.toHighlight-t.fromHighlight+1 < height {
  1090  			// Yes, let's center the highlights.
  1091  			t.lineOffset = (t.fromHighlight + t.toHighlight - height) / 2
  1092  		} else {
  1093  			// No, let's move to the start of the highlights.
  1094  			t.lineOffset = t.fromHighlight
  1095  		}
  1096  
  1097  		// If the highlight is too far to the right, move it to the middle.
  1098  		if t.posHighlight-t.columnOffset > 3*width/4 {
  1099  			t.columnOffset = t.posHighlight - width/2
  1100  		}
  1101  
  1102  		// If the highlight is offscreen on the left, move it onscreen.
  1103  		if t.posHighlight-t.columnOffset < 0 {
  1104  			t.columnOffset = t.posHighlight - width/4
  1105  		}
  1106  	}
  1107  	t.scrollToHighlights = false
  1108  
  1109  	// Adjust line offset.
  1110  	if t.lineOffset+height > len(t.index) {
  1111  		t.trackEnd = true
  1112  	}
  1113  	if t.trackEnd {
  1114  		t.lineOffset = len(t.index) - height
  1115  	}
  1116  	if t.lineOffset < 0 {
  1117  		t.lineOffset = 0
  1118  	}
  1119  
  1120  	// Adjust column offset.
  1121  	if t.align == AlignLeft {
  1122  		if t.columnOffset+width > t.longestLine {
  1123  			t.columnOffset = t.longestLine - width
  1124  		}
  1125  		if t.columnOffset < 0 {
  1126  			t.columnOffset = 0
  1127  		}
  1128  	} else if t.align == AlignRight {
  1129  		if t.columnOffset-width < -t.longestLine {
  1130  			t.columnOffset = width - t.longestLine
  1131  		}
  1132  		if t.columnOffset > 0 {
  1133  			t.columnOffset = 0
  1134  		}
  1135  	} else { // AlignCenter.
  1136  		half := (t.longestLine - width) / 2
  1137  		if half > 0 {
  1138  			if t.columnOffset > half {
  1139  				t.columnOffset = half
  1140  			}
  1141  			if t.columnOffset < -half {
  1142  				t.columnOffset = -half
  1143  			}
  1144  		} else {
  1145  			t.columnOffset = 0
  1146  		}
  1147  	}
  1148  
  1149  	// Calculate offset to apply vertical alignment
  1150  	verticalOffset := 0
  1151  	if len(t.index) < height {
  1152  		if t.valign == AlignMiddle {
  1153  			verticalOffset = (height - len(t.index)) / 2
  1154  		} else if t.valign == AlignBottom {
  1155  			verticalOffset = height - len(t.index)
  1156  		}
  1157  	}
  1158  
  1159  	// Draw the buffer.
  1160  	defaultStyle := tcell.StyleDefault.Foreground(t.textColor).Background(t.backgroundColor)
  1161  	for line := t.lineOffset; line < len(t.index); line++ {
  1162  		// Are we done?
  1163  		if line-t.lineOffset >= height {
  1164  			break
  1165  		}
  1166  
  1167  		// Get the text for this line.
  1168  		index := t.index[line]
  1169  		text := t.buffer[index.Line][index.Pos:index.NextPos]
  1170  		foregroundColor := index.ForegroundColor
  1171  		backgroundColor := index.BackgroundColor
  1172  		attributes := index.Attributes
  1173  		regionID := index.Region
  1174  		if t.regions {
  1175  			if len(t.regionInfos) > 0 && !bytes.Equal(t.regionInfos[len(t.regionInfos)-1].ID, regionID) {
  1176  				// End last region.
  1177  				t.regionInfos[len(t.regionInfos)-1].ToX = x
  1178  				t.regionInfos[len(t.regionInfos)-1].ToY = y + line - t.lineOffset
  1179  			}
  1180  			if len(regionID) > 0 && (len(t.regionInfos) == 0 || !bytes.Equal(t.regionInfos[len(t.regionInfos)-1].ID, regionID)) {
  1181  				// Start a new region.
  1182  				t.regionInfos = append(t.regionInfos, &textViewRegion{
  1183  					ID:    regionID,
  1184  					FromX: x,
  1185  					FromY: y + line - t.lineOffset,
  1186  					ToX:   -1,
  1187  					ToY:   -1,
  1188  				})
  1189  			}
  1190  		}
  1191  
  1192  		// Process tags.
  1193  		colorTagIndices, colorTags, regionIndices, regions, escapeIndices, strippedText, _ := decomposeText(text, t.dynamicColors, t.regions)
  1194  
  1195  		// Calculate the position of the line.
  1196  		var skip, posX int
  1197  		if t.align == AlignLeft {
  1198  			posX = -t.columnOffset
  1199  		} else if t.align == AlignRight {
  1200  			posX = width - index.Width - t.columnOffset
  1201  		} else { // AlignCenter.
  1202  			posX = (width-index.Width)/2 - t.columnOffset
  1203  		}
  1204  		if posX < 0 {
  1205  			skip = -posX
  1206  			posX = 0
  1207  		}
  1208  
  1209  		drawAtY := y + line - t.lineOffset + verticalOffset
  1210  
  1211  		// Print the line.
  1212  		if drawAtY >= 0 {
  1213  			var colorPos, regionPos, escapePos, tagOffset, skipped int
  1214  			iterateString(string(strippedText), func(main rune, comb []rune, textPos, textWidth, screenPos, screenWidth int) bool {
  1215  				// Process tags.
  1216  				for {
  1217  					if colorPos < len(colorTags) && textPos+tagOffset >= colorTagIndices[colorPos][0] && textPos+tagOffset < colorTagIndices[colorPos][1] {
  1218  						// Get the color.
  1219  						foregroundColor, backgroundColor, attributes = styleFromTag(foregroundColor, backgroundColor, attributes, colorTags[colorPos])
  1220  						tagOffset += colorTagIndices[colorPos][1] - colorTagIndices[colorPos][0]
  1221  						colorPos++
  1222  					} else if regionPos < len(regionIndices) && textPos+tagOffset >= regionIndices[regionPos][0] && textPos+tagOffset < regionIndices[regionPos][1] {
  1223  						// Get the region.
  1224  						if len(regionID) > 0 && len(t.regionInfos) > 0 && bytes.Equal(t.regionInfos[len(t.regionInfos)-1].ID, regionID) {
  1225  							// End last region.
  1226  							t.regionInfos[len(t.regionInfos)-1].ToX = x + posX
  1227  							t.regionInfos[len(t.regionInfos)-1].ToY = y + line - t.lineOffset
  1228  						}
  1229  						regionID = regions[regionPos][1]
  1230  						if len(regionID) > 0 {
  1231  							// Start new region.
  1232  							t.regionInfos = append(t.regionInfos, &textViewRegion{
  1233  								ID:    regionID,
  1234  								FromX: x + posX,
  1235  								FromY: y + line - t.lineOffset,
  1236  								ToX:   -1,
  1237  								ToY:   -1,
  1238  							})
  1239  						}
  1240  						tagOffset += regionIndices[regionPos][1] - regionIndices[regionPos][0]
  1241  						regionPos++
  1242  					} else {
  1243  						break
  1244  					}
  1245  				}
  1246  
  1247  				// Skip the second-to-last character of an escape tag.
  1248  				if escapePos < len(escapeIndices) && textPos+tagOffset == escapeIndices[escapePos][1]-2 {
  1249  					tagOffset++
  1250  					escapePos++
  1251  				}
  1252  
  1253  				// Mix the existing style with the new style.
  1254  				_, _, existingStyle, _ := screen.GetContent(x+posX, drawAtY)
  1255  				_, background, _ := existingStyle.Decompose()
  1256  				style := overlayStyle(background, defaultStyle, foregroundColor, backgroundColor, attributes)
  1257  
  1258  				// Do we highlight this character?
  1259  				var highlighted bool
  1260  				if len(regionID) > 0 {
  1261  					if _, ok := t.highlights[string(regionID)]; ok {
  1262  						highlighted = true
  1263  					}
  1264  				}
  1265  				if highlighted {
  1266  					fg := t.highlightForeground
  1267  					bg := t.highlightBackground
  1268  					if fg == tcell.ColorDefault {
  1269  						fg = Styles.PrimaryTextColor
  1270  						if fg == tcell.ColorDefault {
  1271  							fg = tcell.ColorWhite.TrueColor()
  1272  						}
  1273  					}
  1274  					if bg == tcell.ColorDefault {
  1275  						r, g, b := fg.RGB()
  1276  						c := colorful.Color{R: float64(r) / 255, G: float64(g) / 255, B: float64(b) / 255}
  1277  						_, _, li := c.Hcl()
  1278  						if li < .5 {
  1279  							bg = tcell.ColorWhite.TrueColor()
  1280  						} else {
  1281  							bg = tcell.ColorBlack.TrueColor()
  1282  						}
  1283  					}
  1284  					style = style.Foreground(fg).Background(bg)
  1285  				}
  1286  
  1287  				// Skip to the right.
  1288  				if !t.wrap && skipped < skip {
  1289  					skipped += screenWidth
  1290  					return false
  1291  				}
  1292  
  1293  				// Stop at the right border.
  1294  				if posX+screenWidth > width {
  1295  					return true
  1296  				}
  1297  
  1298  				// Draw the character.
  1299  				for offset := screenWidth - 1; offset >= 0; offset-- {
  1300  					if offset == 0 {
  1301  						screen.SetContent(x+posX+offset, drawAtY, main, comb, style)
  1302  					} else {
  1303  						screen.SetContent(x+posX+offset, drawAtY, ' ', nil, style)
  1304  					}
  1305  				}
  1306  
  1307  				// Advance.
  1308  				posX += screenWidth
  1309  				return false
  1310  			})
  1311  		}
  1312  	}
  1313  
  1314  	// If this view is not scrollable, we'll purge the buffer of lines that have
  1315  	// scrolled out of view.
  1316  	if !t.scrollable && t.lineOffset > 0 {
  1317  		if t.lineOffset >= len(t.index) {
  1318  			t.buffer = nil
  1319  		} else {
  1320  			t.buffer = t.buffer[t.index[t.lineOffset].Line:]
  1321  		}
  1322  		t.index = nil
  1323  		t.lineOffset = 0
  1324  	}
  1325  }
  1326  
  1327  // InputHandler returns the handler for this primitive.
  1328  func (t *TextView) InputHandler() func(event *tcell.EventKey, setFocus func(p Primitive)) {
  1329  	return t.WrapInputHandler(func(event *tcell.EventKey, setFocus func(p Primitive)) {
  1330  		key := event.Key()
  1331  
  1332  		if HitShortcut(event, Keys.Cancel, Keys.Select, Keys.Select2, Keys.MovePreviousField, Keys.MoveNextField) {
  1333  			if t.done != nil {
  1334  				t.done(key)
  1335  			}
  1336  			return
  1337  		}
  1338  
  1339  		t.Lock()
  1340  		defer t.Unlock()
  1341  
  1342  		if !t.scrollable {
  1343  			return
  1344  		}
  1345  
  1346  		if HitShortcut(event, Keys.MoveFirst, Keys.MoveFirst2) {
  1347  			t.trackEnd = false
  1348  			t.lineOffset = 0
  1349  			t.columnOffset = 0
  1350  		} else if HitShortcut(event, Keys.MoveLast, Keys.MoveLast2) {
  1351  			t.trackEnd = true
  1352  			t.columnOffset = 0
  1353  		} else if HitShortcut(event, Keys.MoveUp, Keys.MoveUp2) {
  1354  			t.trackEnd = false
  1355  			t.lineOffset--
  1356  		} else if HitShortcut(event, Keys.MoveDown, Keys.MoveDown2) {
  1357  			t.lineOffset++
  1358  		} else if HitShortcut(event, Keys.MoveLeft, Keys.MoveLeft2) {
  1359  			t.columnOffset--
  1360  		} else if HitShortcut(event, Keys.MoveRight, Keys.MoveRight2) {
  1361  			t.columnOffset++
  1362  		} else if HitShortcut(event, Keys.MovePreviousPage) {
  1363  			t.trackEnd = false
  1364  			t.lineOffset -= t.pageSize
  1365  		} else if HitShortcut(event, Keys.MoveNextPage) {
  1366  			t.lineOffset += t.pageSize
  1367  		}
  1368  	})
  1369  }
  1370  
  1371  // MouseHandler returns the mouse handler for this primitive.
  1372  func (t *TextView) MouseHandler() func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive) {
  1373  	return t.WrapMouseHandler(func(action MouseAction, event *tcell.EventMouse, setFocus func(p Primitive)) (consumed bool, capture Primitive) {
  1374  		x, y := event.Position()
  1375  		if !t.InRect(x, y) {
  1376  			return false, nil
  1377  		}
  1378  
  1379  		switch action {
  1380  		case MouseLeftClick:
  1381  			if t.regions {
  1382  				// Find a region to highlight.
  1383  				for _, region := range t.regionInfos {
  1384  					if y == region.FromY && x < region.FromX ||
  1385  						y == region.ToY && x >= region.ToX ||
  1386  						region.FromY >= 0 && y < region.FromY ||
  1387  						region.ToY >= 0 && y > region.ToY {
  1388  						continue
  1389  					}
  1390  					t.Highlight(string(region.ID))
  1391  					break
  1392  				}
  1393  			}
  1394  			consumed = true
  1395  			setFocus(t)
  1396  		case MouseScrollUp:
  1397  			if t.scrollable {
  1398  				t.trackEnd = false
  1399  				t.lineOffset--
  1400  				consumed = true
  1401  			}
  1402  		case MouseScrollDown:
  1403  			if t.scrollable {
  1404  				t.lineOffset++
  1405  				consumed = true
  1406  			}
  1407  		}
  1408  
  1409  		return
  1410  	})
  1411  }
  1412  

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