widget: replace segmentIterator with simpler functions

The replacement functions all use the single seeking function, seekPosition.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/editor.go

@@ -61,7 +61,6 @@ type Editor struct {
 	viewSize     image.Point
 	valid        bool
 	lines        []text.Line
-	shapes       []line
 	dims         layout.Dimensions
 	requestFocus bool
 
@@ -620,34 +619,6 @@ func (e *Editor) layout(gtx layout.Context, content layout.Widget) layout.Dimens
 		e.scrollToCaret()
 	}
 
-	off := image.Point{
-		X: -e.scrollOff.X,
-		Y: -e.scrollOff.Y,
-	}
-	cl := textPadding(e.lines)
-	cl.Max = cl.Max.Add(e.viewSize)
-	caretStart := e.closestPosition(combinedPos{runes: e.caret.start})
-	caretEnd := e.closestPosition(combinedPos{runes: e.caret.end})
-	startSel, endSel := sortPoints(caretStart.lineCol, caretEnd.lineCol)
-	it := segmentIterator{
-		startSel:  startSel,
-		endSel:    endSel,
-		Lines:     e.lines,
-		Clip:      cl,
-		Alignment: e.Alignment,
-		Width:     e.viewSize.X,
-		Offset:    off,
-	}
-	e.shapes = e.shapes[:0]
-	for {
-		layout, off, selected, yOffs, size, ok := it.Next()
-		if !ok {
-			break
-		}
-		op := clip.Outline{Path: e.shaper.Shape(e.font, e.textSize, layout)}.Op()
-		e.shapes = append(e.shapes, line{off, op, selected, yOffs, size})
-	}
-
 	key.InputOp{Tag: &e.eventKey, Hint: e.InputHint}.Add(gtx.Ops)
 	if e.requestFocus {
 		key.FocusOp{Tag: &e.eventKey}.Add(gtx.Ops)
@@ -700,17 +671,50 @@ func (e *Editor) PaintSelection(gtx layout.Context) {
 	cl := textPadding(e.lines)
 	cl.Max = cl.Max.Add(e.viewSize)
 	defer clip.Rect(cl).Push(gtx.Ops).Pop()
-	for _, shape := range e.shapes {
-		if !shape.selected {
-			continue
+	selStart, selEnd := e.caret.start, e.caret.end
+	if selStart > selEnd {
+		selStart, selEnd = selEnd, selStart
+	}
+	caretStart := e.closestPosition(combinedPos{runes: selStart})
+	caretEnd := e.closestPosition(combinedPos{runes: selEnd})
+	scroll := image.Point{
+		X: e.scrollOff.X,
+		Y: e.scrollOff.Y,
+	}
+	cl = cl.Add(scroll)
+	pos := e.seekFirstVisibleLine(cl.Min.Y)
+	for !posIsBelow(e.lines, pos, cl.Max.Y) {
+		start, end := clipLine(e.lines, e.Alignment, e.viewSize.X, cl, pos)
+		lineIdx := start.lineCol.Y
+		if lineIdx > caretEnd.lineCol.Y {
+			// Line is after selection end; we're done.
+			return
 		}
-		offset := shape.offset
-		offset.Y += shape.selectionYOffs
-		t := op.Offset(layout.FPt(offset)).Push(gtx.Ops)
-		cl := clip.Rect(image.Rectangle{Max: shape.selectionSize}).Push(gtx.Ops)
+		// Clamp start, end to selection.
+		if start.runes < selStart {
+			start = caretStart
+		}
+		if end.runes > selEnd {
+			end = caretEnd
+		}
+
+		line := e.lines[start.lineCol.Y]
+		dotStart := image.Pt(start.x.Round(), start.y)
+		dotEnd := image.Pt(end.x.Round(), end.y)
+		t := op.Offset(layout.FPt(scroll.Mul(-1))).Push(gtx.Ops)
+		size := image.Rectangle{
+			Min: dotStart.Sub(image.Point{Y: line.Ascent.Ceil()}),
+			Max: dotEnd.Add(image.Point{Y: line.Descent.Ceil()}),
+		}
+		op := clip.Rect(size).Push(gtx.Ops)
 		paint.PaintOp{}.Add(gtx.Ops)
-		cl.Pop()
+		op.Pop()
 		t.Pop()
+
+		if pos.lineCol.Y == len(e.lines)-1 {
+			break
+		}
+		pos = e.closestPosition(combinedPos{lineCol: screenPos{Y: pos.lineCol.Y + 1}})
 	}
 }
 
@@ -718,12 +722,28 @@ func (e *Editor) PaintText(gtx layout.Context) {
 	cl := textPadding(e.lines)
 	cl.Max = cl.Max.Add(e.viewSize)
 	defer clip.Rect(cl).Push(gtx.Ops).Pop()
-	for _, shape := range e.shapes {
-		t := op.Offset(layout.FPt(shape.offset)).Push(gtx.Ops)
-		cl := shape.clip.Push(gtx.Ops)
+	scroll := image.Point{
+		X: e.scrollOff.X,
+		Y: e.scrollOff.Y,
+	}
+	cl = cl.Add(scroll)
+	pos := e.seekFirstVisibleLine(cl.Min.Y)
+	for !posIsBelow(e.lines, pos, cl.Max.Y) {
+		start, end := clipLine(e.lines, e.Alignment, e.viewSize.X, cl, pos)
+		line := e.lines[start.lineCol.Y]
+		l := subLayout(line, start.lineCol.X, end.lineCol.X)
+
+		off := image.Point{X: start.x.Floor(), Y: start.y}.Sub(scroll)
+		t := op.Offset(layout.FPt(off)).Push(gtx.Ops)
+		op := clip.Outline{Path: e.shaper.Shape(e.font, e.textSize, l)}.Op().Push(gtx.Ops)
 		paint.PaintOp{}.Add(gtx.Ops)
-		cl.Pop()
+		op.Pop()
 		t.Pop()
+
+		if pos.lineCol.Y == len(e.lines)-1 {
+			break
+		}
+		pos = e.closestPosition(combinedPos{lineCol: screenPos{Y: pos.lineCol.Y + 1}})
 	}
 }
 
@@ -757,6 +777,19 @@ func (e *Editor) PaintCaret(gtx layout.Context) {
 	}
 }
 
+func (e *Editor) seekFirstVisibleLine(y int) combinedPos {
+	pos := e.closestPosition(combinedPos{y: y})
+	for pos.lineCol.Y > 0 {
+		prevLine := pos.lineCol.Y - 1
+		prev := e.closestPosition(combinedPos{lineCol: screenPos{Y: prevLine}})
+		if posIsAbove(e.lines, prev, y) {
+			break
+		}
+		pos = prev
+	}
+	return pos
+}
+
 func (e *Editor) caretInfo() (pos image.Point, ascent, descent int) {
 	caretStart := e.closestPosition(combinedPos{runes: e.caret.start})
 	carX := caretStart.x
@@ -889,11 +922,7 @@ func (e *Editor) indexPosition(pos combinedPos) combinedPos {
 	e.makeValid()
 	// Initialize index with first caret position.
 	if len(e.index) == 0 {
-		l := e.lines[0]
-		e.index = append(e.index, combinedPos{
-			x: align(e.Alignment, l.Width, e.viewSize.X),
-			y: l.Ascent.Ceil(),
-		})
+		e.index = append(e.index, firstPos(e.lines[0], e.Alignment, e.viewSize.X))
 	}
 	i := sort.Search(len(e.index), func(i int) bool {
 		return positionGreaterOrEqual(e.lines, e.index[i], pos)
@@ -949,7 +978,7 @@ func (e *Editor) closestPosition(pos combinedPos) combinedPos {
 	const runesPerIndexEntry = 50
 	for {
 		var done bool
-		closest, done = seekPosition(e.lines, closest, pos, e.Alignment, e.viewSize.X, runesPerIndexEntry)
+		closest, done = seekPosition(e.lines, e.Alignment, e.viewSize.X, closest, pos, runesPerIndexEntry)
 		if done {
 			return closest
 		}
@@ -959,7 +988,7 @@ func (e *Editor) closestPosition(pos combinedPos) combinedPos {
 
 // seekPosition seeks to the position closest to needle, starting at start and returns true.
 // If limit is non-zero, seekPosition stops seeks after limit runes and returns false.
-func seekPosition(lines []text.Line, start, needle combinedPos, alignment text.Alignment, width, limit int) (combinedPos, bool) {
+func seekPosition(lines []text.Line, alignment text.Alignment, width int, start, needle combinedPos, limit int) (combinedPos, bool) {
 	l := lines[start.lineCol.Y]
 	count := 0
 	// Advance next and prev until next is greater than or equal to pos.

widget/label.go

@@ -30,125 +30,57 @@ type Label struct {
 // not pixels): Y = line number, X = rune column.
 type screenPos image.Point
 
-type segmentIterator struct {
-	Lines     []text.Line
-	Clip      image.Rectangle
-	Alignment text.Alignment
-	Width     int
-	Offset    image.Point
-	startSel  screenPos
-	endSel    screenPos
-
-	pos    screenPos   // current position
-	line   text.Line   // current line
-	layout text.Layout // current line's Layout
-
-	// pixel positions
-	off         fixed.Point26_6
-	y, prevDesc fixed.Int26_6
-}
-
 const inf = 1e6
 
-func (l *segmentIterator) Next() (text.Layout, image.Point, bool, int, image.Point, bool) {
-	for l.pos.Y < len(l.Lines) {
-		if l.pos.X == 0 {
-			l.line = l.Lines[l.pos.Y]
+func posIsAbove(lines []text.Line, pos combinedPos, y int) bool {
+	line := lines[pos.lineCol.Y]
+	return pos.y+line.Bounds.Max.Y.Ceil() < y
+}
 
-			// Calculate X & Y pixel coordinates of left edge of line. We need y
-			// for the next line, so it's in l, but we only need x here, so it's
-			// not.
-			x := align(l.Alignment, l.line.Width, l.Width) + fixed.I(l.Offset.X)
-			l.y += l.prevDesc + l.line.Ascent
-			l.prevDesc = l.line.Descent
-			// Align baseline and line start to the pixel grid.
-			l.off = fixed.Point26_6{X: fixed.I(x.Floor()), Y: fixed.I(l.y.Ceil())}
-			l.y = l.off.Y
-			l.off.Y += fixed.I(l.Offset.Y)
-			if (l.off.Y + l.line.Bounds.Min.Y).Floor() > l.Clip.Max.Y {
-				break
-			}
+func posIsBelow(lines []text.Line, pos combinedPos, y int) bool {
+	line := lines[pos.lineCol.Y]
+	return pos.y+line.Bounds.Min.Y.Floor() > y
+}
 
-			if (l.off.Y + l.line.Bounds.Max.Y).Ceil() < l.Clip.Min.Y {
-				// This line is outside/before the clip area; go on to the next line.
-				l.pos.Y++
-				continue
-			}
+func clipLine(lines []text.Line, alignment text.Alignment, width int, clip image.Rectangle, linePos combinedPos) (start combinedPos, end combinedPos) {
+	// Seek to first (potentially) visible column.
+	lineIdx := linePos.lineCol.Y
+	line := lines[lineIdx]
+	// runeWidth is the width of the widest rune in line.
+	runeWidth := (line.Bounds.Max.X - line.Width).Ceil()
+	q := combinedPos{y: start.y, x: fixed.I(clip.Min.X - runeWidth)}
+	start, _ = seekPosition(lines, alignment, width, linePos, q, 0)
+	// Seek to first invisible column after start.
+	q = combinedPos{y: start.y, x: fixed.I(clip.Max.X + runeWidth)}
+	end, _ = seekPosition(lines, alignment, width, start, q, 0)
+	return start, end
+}
 
-			// Copy the line's Layout, since we slice it up later.
-			l.layout = l.line.Layout
-
-			// Find the left edge of the text visible in the l.Clip clipping
-			// area.
-			for len(l.layout.Advances) > 0 {
-				_, n := utf8.DecodeRuneInString(l.layout.Text)
-				adv := l.layout.Advances[0]
-				if (l.off.X + adv + l.line.Bounds.Max.X - l.line.Width).Ceil() >= l.Clip.Min.X {
-					break
-				}
-				l.off.X += adv
-				l.layout.Text = l.layout.Text[n:]
-				l.layout.Advances = l.layout.Advances[1:]
-				l.pos.X++
-			}
-		}
-
-		selected := l.inSelection()
-		endx := l.off.X
-		rune := 0
-		nextLine := true
-		retLayout := l.layout
-		for n := range l.layout.Text {
-			selChanged := selected != l.inSelection()
-			beyondClipEdge := (endx + l.line.Bounds.Min.X).Floor() > l.Clip.Max.X
-			if selChanged || beyondClipEdge {
-				retLayout.Advances = l.layout.Advances[:rune]
-				retLayout.Text = l.layout.Text[:n]
-				if selChanged {
-					// Save the rest of the line
-					l.layout.Advances = l.layout.Advances[rune:]
-					l.layout.Text = l.layout.Text[n:]
-					nextLine = false
-				}
-				break
-			}
-			endx += l.layout.Advances[rune]
-			rune++
-			l.pos.X++
-		}
-		offFloor := image.Point{X: l.off.X.Floor(), Y: l.off.Y.Floor()}
-
-		// Calculate the width & height if the returned text.
-		//
-		// If there's a better way to do this, I'm all ears.
-		var d fixed.Int26_6
-		for _, adv := range retLayout.Advances {
-			d += adv
-		}
-		size := image.Point{
-			X: d.Ceil(),
-			Y: (l.line.Ascent + l.line.Descent).Ceil(),
-		}
-
-		if nextLine {
-			l.pos.Y++
-			l.pos.X = 0
-		} else {
-			l.off.X = endx
-		}
-
-		return retLayout, offFloor, selected, l.prevDesc.Ceil() - size.Y, size, true
+func subLayout(line text.Line, startCol, endCol int) text.Layout {
+	adv := line.Layout.Advances
+	if startCol == len(adv) {
+		return text.Layout{}
 	}
-	return text.Layout{}, image.Point{}, false, 0, image.Point{}, false
+	adv = adv[startCol:endCol]
+	txt := line.Layout.Text
+	for i := 0; i < startCol; i++ {
+		_, s := utf8.DecodeRuneInString(txt)
+		txt = txt[s:]
+	}
+	n := 0
+	for i := startCol; i < endCol; i++ {
+		_, s := utf8.DecodeRuneInString(txt[n:])
+		n += s
+	}
+	txt = txt[:n]
+	return text.Layout{Text: txt, Advances: adv}
 }
 
-func (l *segmentIterator) inSelection() bool {
-	return l.startSel.LessOrEqual(l.pos) &&
-		l.pos.Less(l.endSel)
-}
-
-func (p1 screenPos) LessOrEqual(p2 screenPos) bool {
-	return p1.Y < p2.Y || (p1.Y == p2.Y && p1.X <= p2.X)
+func firstPos(line text.Line, alignment text.Alignment, width int) combinedPos {
+	return combinedPos{
+		x: align(alignment, line.Width, width),
+		y: line.Ascent.Ceil(),
+	}
 }
 
 func (p1 screenPos) Less(p2 screenPos) bool {
@@ -164,29 +96,31 @@ func (l Label) Layout(gtx layout.Context, s text.Shaper, font text.Font, size un
 	}
 	dims := linesDimens(lines)
 	dims.Size = cs.Constrain(dims.Size)
+	if len(lines) == 0 {
+		return dims
+	}
 	cl := textPadding(lines)
 	cl.Max = cl.Max.Add(dims.Size)
-	it := segmentIterator{
-		Lines:     lines,
-		Clip:      cl,
-		Alignment: l.Alignment,
-		Width:     dims.Size.X,
-	}
-	for {
-		l, off, _, _, _, ok := it.Next()
-		if !ok {
+	defer clip.Rect(cl).Push(gtx.Ops).Pop()
+	semantic.LabelOp(txt).Add(gtx.Ops)
+	pos := firstPos(lines[0], l.Alignment, dims.Size.X)
+	for !posIsBelow(lines, pos, cl.Max.Y) {
+		start, end := clipLine(lines, l.Alignment, dims.Size.X, cl, pos)
+		line := lines[start.lineCol.Y]
+		lt := subLayout(line, start.lineCol.X, end.lineCol.X)
+
+		off := image.Point{X: start.x.Floor(), Y: start.y}
+		t := op.Offset(layout.FPt(off)).Push(gtx.Ops)
+		op := clip.Outline{Path: s.Shape(font, textSize, lt)}.Op().Push(gtx.Ops)
+		paint.PaintOp{}.Add(gtx.Ops)
+		op.Pop()
+		t.Pop()
+
+		if pos.lineCol.Y == len(lines)-1 {
 			break
 		}
-		t := op.Offset(layout.FPt(off)).Push(gtx.Ops)
-		rcl := clip.Rect(cl.Sub(off)).Push(gtx.Ops)
-		cl := clip.Outline{Path: s.Shape(font, textSize, l)}.Op().Push(gtx.Ops)
-		paint.PaintOp{}.Add(gtx.Ops)
-		cl.Pop()
-		rcl.Pop()
-		t.Pop()
+		pos, _ = seekPosition(lines, l.Alignment, dims.Size.X, pos, combinedPos{lineCol: screenPos{Y: pos.lineCol.Y + 1}}, 0)
 	}
-	defer clip.Rect(image.Rectangle{Max: dims.Size}).Push(gtx.Ops).Pop()
-	semantic.LabelOp(txt).Add(gtx.Ops)
 	return dims
 }