rtxt.go

package richtext

import (
	"fmt"
	"image"
	"image/color"
	"math/rand"
	"sort"
	"strings"
	"time"
	"unicode"
	"unicode/utf8"

	"github.com/aarzilli/nucular"
	"github.com/aarzilli/nucular/font"
	"golang.org/x/image/math/fixed"
	"golang.org/x/mobile/event/mouse"
)

type RichText struct {
	name       string
	chunks     []chunk    // the full text of this widget, divided into chunks as they were added by the caller
	styleSels  []styleSel // styling for the text in non-overlapping selections of increasing S
	Sel        Sel        // selected text if this widget is selectable, cursor position will have S == E
	Flags      Flags
	flags      Flags                   // flags for this widget
	SelFgColor color.RGBA              // foreground color for selection, zero value specifies that it should be copied from the window style
	SelColor   color.RGBA              // background color for selection, zero value specifies that it should be copied from the window style
	Width      int                     // maximum line width
	Events     Events                  // events that happened during current frame
	Group      *SelectionGroup         // selection group for this object, only one object in the group can have a selection
	Replace    func(Sel, *string) bool // if set and the Editable flag is set it will be called when the user wants to edit and should replace the specified selection with the given string

	txtColor, selFgColor, selColor color.RGBA // default foreground color and background selected color

	face font.Face // default face

	first bool
	ctor  Ctor

	changed  bool            // must recalculate text advances
	width    int             // currently flowed width
	maxWidth int             // maximum line width
	adv      []fixed.Int26_6 // advance for each rune in chunks
	lines    []line          // line of text, possibly wrapped

	down              bool  // a click/selection is in progress
	isClick           bool  // the click/selection in progress could be a click (unless the mouse moves too much)
	hadSelection      bool  // had a non-empty selection when the click/selection started
	dragStart         int32 // stat of drag
	lastClickTime     time.Time
	clickCount        int // number of consecutive clicks
	wasFocused        bool
	pageKey, arrowKey int

	undoEdit *undoEdit

	followCursor bool // scroll to show cursor on screen

	focused bool
}

type Sel struct {
	S, E int32
}

func (sel Sel) contains(p int32) bool {
	return p >= sel.S && p < sel.E
}

type Flags uint16

const (
	AutoWrap Flags = 1 << iota
	Selectable
	Clipboard
	ShowTick
	Keyboard // scrolling using keyboard
	MimicLabel
	Editable // supports editing
)

type FaceFlags uint16

const (
	Underline FaceFlags = 1 << iota
	Strikethrough
)

type Align uint8

const (
	AlignLeftDumb Align = iota
	AlignLeft
	AlignRight
	AlignCenter
	AlignJustified
)

type Events uint8

const (
	Clicked Events = 1 << iota
	Active
)

type SelectionGroup struct {
	cur *RichText
}

type chunk struct {
	b []byte
	s string
}

func (chunk chunk) len() int32 {
	if chunk.b != nil {
		return int32(len(chunk.b))
	}
	return int32(len(chunk.s))
}

func (c chunk) sub(start, end int32) chunk {
	if c.b != nil {
		return chunk{b: c.b[start:end]}
	}
	return chunk{s: c.s[start:end]}
}

func (chunk chunk) isspacing() bool {
	if chunk.b != nil {
		return len(chunk.b) == 0 || (len(chunk.b) == 1 && (chunk.b[0] == '\t' || chunk.b[0] == ' '))
	}
	return chunk.s == "\t" || chunk.s == " " || chunk.s == ""
}

func (chunk chunk) runeCount() int {
	if chunk.b != nil {
		return utf8.RuneCount(chunk.b)
	}
	return utf8.RuneCountInString(chunk.s)
}

func (chunk chunk) str() string {
	if chunk.b != nil {
		return string(chunk.b)
	}
	return chunk.s
}

type TextStyle struct {
	Face   font.Face
	Cursor font.Cursor
	Flags  FaceFlags

	Color, SelFgColor, BgColor color.RGBA // foreground color, selected foreground color, background color

	LeftMarginHere bool // moves the left margin to this position, must be AlignLeft or AlignLeftDumb

	Tooltip      func(*nucular.Window)
	TooltipWidth int

	ContextMenu func(*nucular.Window)
}

type styleSel struct {
	Sel
	TextStyle

	align     Align
	paraColor color.RGBA

	link   func()
	isLink bool

	hoverColor color.RGBA // hover color for links
}

type line struct {
	chunks  []chunk     // each chunk has a uniform style
	w       []int       // width of each chunk
	off     []int32     // character offset of the start of each chunk
	runeoff int         // offset in number of runes of the first character in the line
	h       int         // height of the line
	asc     int         // ascent of the biggest font of the line
	p       image.Point // insertion point for the line

	leftMargin int // displacement from the left of the first chunk, used to implement right and center alignment
}

func (ln line) width() int {
	w := 0
	for i := range ln.w {
		w += ln.w[i]
	}
	return w
}

func (ln line) endoff() int32 {
	if len(ln.chunks) == 0 {
		return ln.off[0]
	}
	return ln.off[len(ln.chunks)-1] + ln.chunks[len(ln.chunks)-1].len()
}

func (ln line) sel() Sel {
	if len(ln.chunks) == 0 {
		return Sel{ln.off[0], ln.off[0] + 1}
	}
	return Sel{ln.off[0], ln.endoff()}
}

type Ctor struct {
	rtxt *RichText
	mode ctorMode
	w    *nucular.Window
	off  int32 // offset for append mode
	len  int32

	chunks    []chunk
	styleSels []styleSel // not ordered, possibly overlapping
	alignSels []styleSel // not ordered, possibly overlapping
	linkSels  []styleSel

	savedStyleOk bool
	savedStyle   styleSel

	selsDone bool // all sels are closed

	linkClick int32 // position of click in link mode

	appendScroll bool
}

type ctorMode uint8

const (
	ctorWidget ctorMode = iota
	ctorRows
	ctorAppend
	ctorLink
)

func New(flags Flags) *RichText {
	n := rand.Int()
	if flags&Editable != 0 {
		flags |= ShowTick
		flags &^= Keyboard
	}
	return &RichText{
		name:  fmt.Sprintf("richtext%d", n),
		Flags: flags,
		flags: flags,
		first: true,
	}
}

// Widget adds this rich text widget as a widget to w. The returned
// constructor allows populating the rich text widget with text and
// responding to events.
// The constructor will be returned under this circumstances:
// 1. the first time this function or Rows is called
// 2. changed is true
// 3. a link was clicked
func (rtxt *RichText) Widget(w *nucular.Window, changed bool) *Ctor {
	rtxt.initialize(w, &changed)
	if rtxt.first || changed {
		rtxt.changed = true
		rtxt.ctor = Ctor{rtxt: rtxt, mode: ctorWidget, w: w}
		return &rtxt.ctor
	}
	return rtxt.drawWidget(w)
}

// Rows is like Widget but adds the contents as a series of rows instead of
// a single widget.
func (rtxt *RichText) Rows(w *nucular.Window, changed bool) *Ctor {
	rtxt.initialize(w, &changed)
	if rtxt.first || changed {
		rtxt.changed = true
		rtxt.ctor = Ctor{rtxt: rtxt, mode: ctorRows, w: w}
		return &rtxt.ctor
	}
	return rtxt.drawRows(w, 0)
}

// Append allows adding text at the end of the widget. Calling Link or
// LinkBytes on the returned constructor is illegal if callback is nil.
// Selections for SetStyleForSel and SetAlignForSel are interpreted to be
// relative to the newly added text.
func (rtxt *RichText) Append(scroll bool) *Ctor {
	if rtxt.first {
		panic("Append called on a RichText widget that isn't initialized")
	}
	off := int32(0)
	for _, chunk := range rtxt.chunks {
		off += chunk.len()
	}
	rtxt.ctor = Ctor{rtxt: rtxt, mode: ctorAppend, off: off, appendScroll: scroll}

	lastSel := rtxt.styleSels[len(rtxt.styleSels)-1]

	rtxt.ctor.alignSels = append(rtxt.ctor.alignSels, styleSel{Sel: Sel{S: int32(rtxt.ctor.off + rtxt.ctor.len)}, align: lastSel.align, paraColor: lastSel.paraColor})
	return &rtxt.ctor
}

// Look searches from the next occurence of text inside rtxt, starting at
// rtxt.Sel.S. Restarts the search from the start if nothing is found.
func (rtxt *RichText) Look(text string, wraparound bool) bool {
	insensitive := true

	for _, ch := range text {
		if unicode.IsUpper(ch) {
			insensitive = false
			break
		}
	}

	var titer textIter
	titer.Init(rtxt)
	if titer.Advance(rtxt.Sel.S) {
		for {
			if ok, sel := textIterMatch(titer, text, insensitive); ok {
				rtxt.Sel = sel
				return true
			}
			if !titer.Next() {
				break
			}
		}
	}

	if !wraparound {
		return false
	}

	titer.Init(rtxt)
	for {
		if ok, sel := textIterMatch(titer, text, insensitive); ok {
			rtxt.Sel = sel
			return true
		}
		if !titer.Next() {
			break
		}
	}

	rtxt.Sel.S = rtxt.Sel.E
	return false
}

func (rtxt *RichText) FollowCursor() {
	rtxt.followCursor = true
}

func (rtxt *RichText) Get(sel Sel) string {
	var titer textIter
	titer.Init(rtxt)
	if !titer.Advance(rtxt.Sel.S) {
		return ""
	}

	startChunkIdx := titer.chunkIdx
	startByteIdx := titer.j

	var endChunkIdx int
	var endByteIdx int32
	if titer.Advance(rtxt.Sel.E - rtxt.Sel.S) {
		endChunkIdx = titer.chunkIdx
		endByteIdx = titer.j
	} else {
		endChunkIdx = len(rtxt.chunks)
		endByteIdx = 0
	}

	if startChunkIdx == endChunkIdx {
		return rtxt.chunks[startChunkIdx].sub(startByteIdx, endByteIdx).str()
	}

	var out strings.Builder
	out.WriteString(rtxt.chunks[startChunkIdx].sub(startByteIdx, rtxt.chunks[startChunkIdx].len()).str())

	for i := startChunkIdx + 1; i < endChunkIdx; i++ {
		out.WriteString(rtxt.chunks[i].str())
	}

	if endChunkIdx < len(rtxt.chunks) {
		out.WriteString(rtxt.chunks[endChunkIdx].sub(0, endByteIdx).str())
	}

	return out.String()
}

// Tail removes everything but the last n physical lines
func (rtxt *RichText) Tail(n int) {
	if len(rtxt.lines) <= n {
		return
	}

	off := rtxt.lines[len(rtxt.lines)-n].off[0]
	runeoff := rtxt.lines[len(rtxt.lines)-n].runeoff

	off2 := int32(0)
	for i, chunk := range rtxt.chunks {
		if off2+chunk.len() > off {
			rtxt.chunks = append(rtxt.chunks[:0], rtxt.chunks[i:]...)
			s := off - off2
			if s >= chunk.len() {
				rtxt.chunks = append(rtxt.chunks[:0], rtxt.chunks[1:]...)
			} else {
				if rtxt.chunks[0].b != nil {
					rtxt.chunks[0].b = rtxt.chunks[0].b[s:]
				} else {
					rtxt.chunks[0].s = rtxt.chunks[0].s[s:]
				}
			}
			break
		}
		off2 += chunk.len()
	}

	rtxt.adv = append(rtxt.adv[:0], rtxt.adv[runeoff:]...)
	rtxt.reflow()
}

// Len returns the length in physical lines of rtxt
func (rtxt *RichText) Len() int {
	return len(rtxt.lines)
}

func (rtxt *RichText) initialize(w *nucular.Window, changed *bool) {
	style := w.Master().Style()
	if (rtxt.SelColor != color.RGBA{}) {
		rtxt.selColor = rtxt.SelColor
	} else {
		rtxt.selColor = style.Edit.SelectedHover
	}
	if (rtxt.SelFgColor != color.RGBA{}) {
		rtxt.selFgColor = rtxt.SelFgColor
	} else {
		rtxt.selFgColor = style.Edit.SelectedTextHover
	}
	rtxt.txtColor = style.Edit.TextActive
	if rtxt.face != style.Font {
		rtxt.changed = true
	}
	rtxt.face = style.Font
	if rtxt.flags != rtxt.Flags {
		rtxt.flags = rtxt.Flags
		rtxt.changed = true
	}

	rtxt.wasFocused = rtxt.focused
	if rtxt.flags&Keyboard != 0 && (w.Input().Mouse.Buttons[mouse.ButtonLeft].Down || w.Input().Mouse.Buttons[mouse.ButtonRight].Down) {
		rtxt.focused = false
	}
	if rtxt.Group != nil && rtxt.Group.cur != rtxt {
		rtxt.focused = false
		rtxt.Sel.S = 0
		rtxt.Sel.E = 0
	}
	if mw, _ := w.Master().(activateEditor); mw != nil && mw.ActivatingEditor() != nil {
		if mw.ActivatingEditor() == rtxt {
			rtxt.focused = true
			rtxt.Group.grab(rtxt, w)
		} else {
			rtxt.focused = false
			rtxt.Sel.S = 0
			rtxt.Sel.E = 0
		}
	}

	rtxt.arrowKey, rtxt.pageKey = 0, 0
	if rtxt.focused && (rtxt.flags&Keyboard != 0 || rtxt.flags&Editable != 0) {
		rtxt.arrowKey, rtxt.pageKey = rtxt.handleKeyboard(w.Input(), changed)
	}

	rtxt.Events = 0
	if rtxt.focused {
		rtxt.Events |= Active
	}
}

func (ctor *Ctor) End() {
	if !ctor.selsDone {
		ctor.closeSels()
	}
	ctor.styleSels = removeEmptySels(ctor.styleSels)
	ctor.alignSels = removeEmptySels(ctor.alignSels)
	ctor.linkSels = removeEmptySels(ctor.linkSels)
	ctor.styleSels = separateStyles(ctor.styleSels)
	ctor.alignSels = separateStyles(ctor.alignSels)
	styleSels := mergeStyles(ctor.styleSels, ctor.alignSels, ctor.linkSels)
	styleSels = removeEmptySels(styleSels)
	switch ctor.mode {
	case ctorAppend:
		n := len(ctor.rtxt.chunks)
		ctor.rtxt.chunks = append(ctor.rtxt.chunks, ctor.chunks...)
		ctor.rtxt.styleSels = append(ctor.rtxt.styleSels, styleSels...)
		ctor.rtxt.calcAdvances(n)
		ctor.rtxt.reflow()
		if ctor.appendScroll {
			ctor.rtxt.Sel = Sel{ctor.off + ctor.len, ctor.off + ctor.len}
			ctor.rtxt.followCursor = true
		}
	case ctorRows:
		ctor.rtxt.styleSels = styleSels
		ctor.rtxt.chunks = ctor.chunks
		ctor.rtxt.drawRows(ctor.w, 0)
	case ctorWidget:
		ctor.rtxt.styleSels = styleSels
		ctor.rtxt.chunks = ctor.chunks
		ctor.rtxt.drawWidget(ctor.w)
	case ctorLink:
		// nothing to do
	}
}

// Align changes current text alignment. It is only legal to call Align
// before inserting text or after a newline character is inserted.
func (ctor *Ctor) Align(align Align) {
	ctor.ParagraphStyle(align, color.RGBA{})
}

func (ctor *Ctor) ParagraphStyle(align Align, color color.RGBA) {
	const badAlign = "Align call not at the start of a line"
	var lastChunk chunk
	if len(ctor.chunks) > 0 {
		lastChunk = ctor.chunks[len(ctor.chunks)-1]
	} else if ctor.mode == ctorAppend && len(ctor.rtxt.chunks) > 0 {
		lastChunk = ctor.rtxt.chunks[len(ctor.rtxt.chunks)-1]
	}
	if lastChunk.b != nil && lastChunk.b[len(lastChunk.b)-1] != '\n' {
		panic(badAlign)
	} else if len(lastChunk.s) > 0 && lastChunk.s[len(lastChunk.s)-1] != '\n' {
		panic(badAlign)
	}

	if ctor.mode == ctorLink {
		return
	}

	if len(ctor.alignSels) > 0 {
		ctor.alignSels[len(ctor.alignSels)-1].E = int32(ctor.off + ctor.len)
	}
	ctor.alignSels = append(ctor.alignSels, styleSel{Sel: Sel{S: int32(ctor.off + ctor.len)}, align: align, paraColor: color})
}

// SetStyle changes current text style. If color or selColor are the zero
// value the default value (copied from the window) will be used.
// If face is nil the default font face from the window style will be used.
func (ctor *Ctor) SetStyle(s TextStyle) {
	if ctor.mode == ctorLink {
		return
	}
	if len(ctor.styleSels) > 0 {
		ctor.styleSels[len(ctor.styleSels)-1].E = ctor.off + ctor.len
	}
	ctor.styleSels = append(ctor.styleSels, styleSel{Sel: Sel{S: int32(ctor.off + ctor.len)}, TextStyle: s})
}

// SaveStyle saves the current text style.
func (ctor *Ctor) SaveStyle() {
	if ctor.mode == ctorLink {
		return
	}
	if len(ctor.styleSels) <= 0 || ctor.styleSels[len(ctor.styleSels)-1].E != 0 {
		ctor.savedStyleOk = false
	} else {
		ctor.savedStyle = ctor.styleSels[len(ctor.styleSels)-1]
		ctor.savedStyleOk = true
	}
}

// ClearStyle resets the text style to the default.
func (ctor *Ctor) ClearStyle() {
	if len(ctor.styleSels) > 0 {
		ctor.styleSels[len(ctor.styleSels)-1].E = ctor.off + ctor.len
	}
}

// RestoreStyle restores the last saved text style.
func (ctor *Ctor) RestoreStyle() {
	if ctor.mode == ctorLink {
		return
	}
	if ctor.savedStyleOk {
		ctor.SetStyle(ctor.savedStyle.TextStyle)
	} else {
		ctor.ClearStyle()
	}
}

// SetAlignForSel changes the alignment for the specified region.
func (ctor *Ctor) SetAlignForSel(sel Sel, align Align) {
	ctor.SetParagraphStyleForSel(sel, align, color.RGBA{})
}

func (ctor *Ctor) SetParagraphStyleForSel(sel Sel, align Align, color color.RGBA) {
	if !ctor.selsDone {
		ctor.closeSels()
	}
	if ctor.mode == ctorLink {
		return
	}
	const badAlign = "Align call not at the start of a line"
	if sel.S > 0 {
		if ctor.findByte(sel.S-1) != '\n' {
			panic(badAlign)
		}
	}
	if sel.E > 0 && sel.E < ctor.len {
		if ctor.findByte(sel.E-1) != '\n' {
			panic(badAlign)
		}
	}
	ctor.alignSels = append(ctor.alignSels, styleSel{Sel: sel, align: align, paraColor: color})
}

func (ctor *Ctor) findByte(off int32) byte {
	cur := int32(0)
	for _, chunk := range ctor.chunks {
		if off < cur+chunk.len() {
			chunkoff := off - cur
			if chunk.b != nil {
				return chunk.b[chunkoff]
			}
			return chunk.s[chunkoff]
		}
		cur += chunk.len()
	}
	return 0
}

// SetStyleForSel changes the text style for the specified region.
func (ctor *Ctor) SetStyleForSel(sel Sel, s TextStyle) {
	if !ctor.selsDone {
		ctor.closeSels()
	}
	if ctor.mode == ctorLink {
		return
	}
	ctor.styleSels = append(ctor.styleSels, styleSel{Sel: sel, TextStyle: s})
}

// Text adds text to the widget.
func (ctor *Ctor) Text(text string) {
	ctor.textChunk(chunk{s: text})
}

// LastChunkSel returns the selection for the last chunk added
func (ctor *Ctor) LastChunkSel() Sel {
	start := int32(0)
	for i := range ctor.chunks {
		if i == len(ctor.chunks)-1 {
			return Sel{start, start + ctor.chunks[i].len()}
		}
		start += ctor.chunks[i].len()
	}
	return Sel{0, 0}
}

// TextBytes adds text to the widget.
//TODO: reenable when implemetned
// func (ctor *Ctor) TextBytes(text []byte) {
// 	ctor.textChunk(chunk{b: text})
// }

func (ctor *Ctor) textChunk(chunk chunk) {
	if ctor.selsDone {
		panic("Text add after selections were finalized")
	}
	if chunk.len() <= 0 {
		return
	}
	ctor.chunks = append(ctor.chunks, chunk)
	ctor.len += chunk.len()
}

// Link adds a link to the widget. It will return true if the link was
// clicked and callback is nil.
func (ctor *Ctor) Link(text string, hoverColor color.RGBA, callback func()) bool {
	return ctor.linkChunk(chunk{s: text}, hoverColor, callback)
}

// LinkBytes adds a link to the widget. It will return true if the link was
// clicked and callback is nil.
//TODO: reenable when implemented
// func (ctor *Ctor) LinkBytes(text []byte, callback func(string)) bool {
// 	panic("not implemented")
// 	return ctor.linkChunk(chunk{b: text}, callback)
// }

func (ctor *Ctor) linkChunk(chunk chunk, hoverColor color.RGBA, callback func()) bool {
	if ctor.mode == ctorAppend && callback == nil {
		panic("Link added in append mode without callback")
	}
	if ctor.selsDone {
		panic("Link added after selections were finalized")
	}
	if chunk.len() <= 0 {
		return false
	}
	sel := Sel{S: ctor.len + ctor.off}
	ctor.textChunk(chunk)
	sel.E = ctor.len + ctor.off
	ctor.linkSels = append(ctor.linkSels, styleSel{Sel: sel, link: callback, isLink: true, hoverColor: hoverColor})
	return ctor.mode == ctorLink && sel.contains(ctor.linkClick)
}

func (ctor *Ctor) closeSels() {
	ctor.selsDone = true
	if len(ctor.alignSels) > 0 {
		ctor.alignSels[len(ctor.alignSels)-1].E = int32(ctor.off + ctor.len)
	}
	if len(ctor.styleSels) > 0 {
		ctor.styleSels[len(ctor.styleSels)-1].E = int32(ctor.off + ctor.len)
	}
}

// separateStyles takes a slice of possibly overlapping styles and makes it
// non-overlapping.
func separateStyles(ssels []styleSel) []styleSel {
	sort.SliceStable(ssels, func(i, j int) bool { return ssels[i].S < ssels[j].S })

	sstack := []styleSel{}
	cur := int32(0)
	r := make([]styleSel, 0, len(ssels))

	for len(ssels) > 0 || len(sstack) > 0 {
		switch {
		case len(sstack) == 0:
			sstack = append(sstack, ssels[0])
			cur = ssels[0].S
			ssels = ssels[1:]

		case len(ssels) == 0 || sstack[len(sstack)-1].E < ssels[0].S:
			s := sstack[len(sstack)-1]
			if cur < s.Sel.E {
				s.Sel.S = cur
				r = append(r, s)
				cur = s.Sel.E
			}
			sstack = sstack[:len(sstack)-1]

		default:
			s := sstack[len(sstack)-1]
			s.Sel.S = cur
			cur = ssels[0].S
			s.Sel.E = cur
			r = append(r, s)
			sstack = append(sstack, ssels[0])
			ssels = ssels[1:]
		}
	}

	return r
}

func mergeStyles(styleSels, alignSels, linkSels []styleSel) []styleSel {
	minPosAfter := func(p0 int32) int32 {
		min := int32((^uint32(0)) >> 1)

		if len(styleSels) > 0 && styleSels[0].S > p0 && styleSels[0].S < min {
			min = styleSels[0].S
		}
		if len(alignSels) > 0 && alignSels[0].S > p0 && alignSels[0].S < min {
			min = alignSels[0].S
		}
		if len(linkSels) > 0 && linkSels[0].S > p0 && linkSels[0].S < min {
			min = linkSels[0].S
		}
		if len(styleSels) > 0 && styleSels[0].E > p0 && styleSels[0].E < min {
			min = styleSels[0].E
		}
		if len(alignSels) > 0 && alignSels[0].E > p0 && alignSels[0].E < min {
			min = alignSels[0].E
		}
		if len(linkSels) > 0 && linkSels[0].E > p0 && linkSels[0].E < min {
			min = linkSels[0].E
		}
		return min
	}

	r := make([]styleSel, 0, len(styleSels))

	appendCurrentStyle := func(sel Sel) {
		s := styleSel{Sel: sel}
		ok := false

		if len(styleSels) > 0 && styleSels[0].contains(sel.S) {
			s = styleSels[0]
			s.Sel = sel
			ok = true
		}
		if len(alignSels) > 0 && alignSels[0].contains(sel.S) {
			s.align = alignSels[0].align
			s.paraColor = alignSels[0].paraColor
			ok = true
		}
		if len(linkSels) > 0 && linkSels[0].contains(sel.S) {
			s.link = linkSels[0].link
			s.isLink = linkSels[0].isLink
			s.hoverColor = linkSels[0].hoverColor
			ok = true
		}
		if ok {
			r = append(r, s)
		}
	}

	removeBefore := func(p0 int32) {
		if len(styleSels) > 0 && styleSels[0].E <= p0 {
			styleSels = styleSels[1:]
		}
		if len(alignSels) > 0 && alignSels[0].E <= p0 {
			alignSels = alignSels[1:]
		}
		if len(linkSels) > 0 && linkSels[0].E <= p0 {
			linkSels = linkSels[1:]
		}
	}

	cur := minPosAfter(-1)

	for {
		next := minPosAfter(cur)
		appendCurrentStyle(Sel{cur, next})
		cur = next
		removeBefore(cur)
		if len(styleSels) == 0 && len(alignSels) == 0 && len(linkSels) == 0 {
			break
		}
	}

	return r
}

func removeEmptySels(styleSels []styleSel) []styleSel {
	r := styleSels[:0]
	for _, styleSel := range styleSels {
		if styleSel.S < styleSel.E {
			r = append(r, styleSel)
		}
	}
	return r
}

type textIter struct {
	rtxt     *RichText
	chunkIdx int
	j        int32
	off      int32
	valid    bool
}

func (titer *textIter) Init(rtxt *RichText) {
	titer.rtxt = rtxt
	titer.chunkIdx = 0
	titer.j = 0
	titer.off = 0
	titer.valid = true
}

func (titer *textIter) Next() bool {
	if !titer.valid {
		return false
	}
	titer.j++
	titer.off++

	if titer.j >= titer.rtxt.chunks[titer.chunkIdx].len() {
		titer.j = 0
		titer.chunkIdx++
		if titer.chunkIdx >= len(titer.rtxt.chunks) {
			titer.valid = false
			return false
		}
	}

	return true
}

func (titer *textIter) Char() byte {
	if !titer.valid {
		return 0
	}
	chunk := titer.rtxt.chunks[titer.chunkIdx]
	if chunk.b != nil {
		return chunk.b[titer.j]
	}
	return chunk.s[titer.j]
}

func (titer *textIter) Advance(off int32) bool {
	titer.j += off
	titer.off += off

	for titer.j >= titer.rtxt.chunks[titer.chunkIdx].len() {
		titer.j -= titer.rtxt.chunks[titer.chunkIdx].len()
		titer.chunkIdx++
		if titer.chunkIdx >= len(titer.rtxt.chunks) {
			titer.valid = false
			return false
		}
	}

	return true
}

func (titer *textIter) Valid() bool {
	return titer.valid
}

func textIterMatch(titer textIter, needle string, insensitive bool) (bool, Sel) {
	start := titer.off
	for i := 0; i < len(needle); i++ {
		ch := titer.Char()
		if insensitive {
			ch = byte(unicode.ToLower(rune(ch)))
		}
		if !titer.Valid() || needle[i] != ch {
			return false, Sel{}
		}
		titer.Next()
	}
	return true, Sel{start, titer.off}
}

func (rtxt *RichText) length() int32 {
	r := int32(0)
	for _, chunk := range rtxt.chunks {
		r += chunk.len()
	}
	return r
}