widget: fix text selection and selection area rendering issues

1. When selecting multiple lines of text, the rendered selection area does not include the last character of the first line.
2. When selecting a specific line (other than the last line) in multiline text, the last character of that line cannot be selected.

Signed-off-by: CoyAce <AkeyCoy@gmail.com>

widget/editor_test.go

@@ -1042,6 +1042,59 @@ func TestEditorSelectShortcuts(t *testing.T) {
 	}
 }
 
+func TestEditorSelect(t *testing.T) {
+	tFont := font.Font{}
+	tFontSize := unit.Sp(10)
+	tShaper := text.NewShaper(text.NoSystemFonts(), text.WithCollection(gofont.Collection()))
+	tEditor := &Editor{
+		SingleLine: false,
+		ReadOnly:   true,
+	}
+	lines := "abc abc abc def def def ghi ghi ghi"
+	tEditor.SetText(lines)
+
+	tRouter := new(input.Router)
+	gtx := layout.Context{
+		Ops:         new(op.Ops),
+		Locale:      english,
+		Constraints: layout.Exact(image.Pt(50, 100)),
+		Source:      tRouter.Source(),
+	}
+	gtx.Execute(key.FocusCmd{Tag: tEditor})
+	tEditor.Layout(gtx, tShaper, tFont, tFontSize, op.CallOp{}, op.CallOp{})
+
+	index := tEditor.text.index
+
+	firstLineGlyphs := index.lines[0].glyphs
+	firstLine := lines[:firstLineGlyphs]
+	yOffFirstLineCenter := index.lines[0].yOff / 2
+
+	tEditor.ClearSelection()
+	tEditor.text.MoveCoord(image.Pt(100, yOffFirstLineCenter))
+	if cStart, cEnd := tEditor.Selection(); cStart != len(firstLine) || cEnd != 0 {
+		t.Errorf("TestEditorSelect %d: initial selection", len(firstLine))
+	}
+	if got := tEditor.SelectedText(); got != firstLine {
+		t.Errorf("TestEditorSelect : Expected %q, got %q", firstLine, got)
+	}
+
+	yOffSecondLineCenter := (index.lines[1].yOff-index.lines[0].yOff)/2 + index.lines[0].yOff
+	tEditor.text.MoveCoord(image.Pt(100, yOffSecondLineCenter))
+
+	secondLineGlyphs := index.lines[1].glyphs
+	firstTwoLines := lines[:firstLineGlyphs+secondLineGlyphs]
+	if got := tEditor.SelectedText(); got != firstTwoLines {
+		t.Errorf("TestEditorSelect : Expected %q, got %q", firstTwoLines, got)
+	}
+
+	tEditor.Layout(gtx, tShaper, tFont, tFontSize, op.CallOp{}, op.CallOp{})
+	firstLineEnd := index.lines[0].width.Round()
+	firstRegionMaxWidth := tEditor.text.regions[0].Bounds.Max.X
+	if firstRegionMaxWidth != firstLineEnd {
+		t.Errorf("Selection paint should contain last character")
+	}
+}
+
 // Verify that an existing selection is dismissed when you press arrow keys.
 func TestSelectMove(t *testing.T) {
 	e := new(Editor)

widget/index.go

@@ -22,6 +22,10 @@ type lineInfo struct {
 	glyphs          int
 }
 
+func (l lineInfo) getLineEnd() fixed.Int26_6 {
+	return l.xOff + l.width
+}
+
 type glyphIndex struct {
 	// glyphs holds the glyphs processed.
 	glyphs []text.Glyph
@@ -231,46 +235,61 @@ func (g *glyphIndex) Glyph(gl text.Glyph) {
 }
 
 func (g *glyphIndex) closestToRune(runeIdx int) (combinedPos, int) {
-	if len(g.positions) == 0 {
+	n := len(g.positions)
+	if n == 0 {
 		return combinedPos{}, 0
 	}
-	i := sort.Search(len(g.positions), func(i int) bool {
+	i := sort.Search(n, func(i int) bool {
 		pos := g.positions[i]
 		return pos.runes >= runeIdx
 	})
-	if i > 0 {
+
-		i--
+	notFound := i == n
+	if notFound {
+		return g.positions[n-1], n - 1
 	}
-	closest := g.positions[i]
+	return g.positions[i], i
-	closestI := i
-	for ; i < len(g.positions); i++ {
-		if g.positions[i].runes == runeIdx {
-			return g.positions[i], i
-		}
-	}
-	return closest, closestI
 }
 
 func (g *glyphIndex) closestToLineCol(lineCol screenPos) combinedPos {
-	if len(g.positions) == 0 {
+	n := len(g.positions)
+	if n == 0 {
 		return combinedPos{}
 	}
-	i := sort.Search(len(g.positions), func(i int) bool {
+	i := sort.Search(n, func(i int) bool {
 		pos := g.positions[i]
 		return pos.lineCol.line > lineCol.line || (pos.lineCol.line == lineCol.line && pos.lineCol.col >= lineCol.col)
 	})
-	if i > 0 {
+	notFound := i == n
-		i--
+	if notFound {
+		return g.positions[n-1]
 	}
-	prior := g.positions[i]
+	pos := g.positions[i]
-	if i+1 >= len(g.positions) {
+	foundInNextLine := pos.lineCol.line > lineCol.line
+	if foundInNextLine && i > 0 {
+		prior := g.positions[i-1]
+		prior.x = g.lines[lineCol.line].getLineEnd()
 		return prior
 	}
-	next := g.positions[i+1]
+	return pos
-	if next.lineCol != lineCol {
+}
-		return prior
+
+func (g *glyphIndex) atStartOfLine(pos combinedPos) bool {
+	if pos.runes == 0 {
+		return true
 	}
-	return next
+	prevRuneIndex := pos.runes - 1
+	lineOfPrevRune := g.positions[prevRuneIndex].lineCol.line
+	return lineOfPrevRune < pos.lineCol.line
+}
+
+func (g *glyphIndex) atEndOfLine(pos combinedPos) bool {
+	if pos.runes == g.positions[len(g.positions)-1].runes {
+		return true
+	}
+	next := pos.runes + 1
+	hasNext := next < len(g.positions)
+	return hasNext && g.positions[next].lineCol.line > pos.lineCol.line
 }
 
 func dist(a, b fixed.Int26_6) fixed.Int26_6 {
@@ -280,9 +299,9 @@ func dist(a, b fixed.Int26_6) fixed.Int26_6 {
 	return b - a
 }
 
-func (g *glyphIndex) closestToXY(x fixed.Int26_6, y int) combinedPos {
+func (g *glyphIndex) closestToXY(x fixed.Int26_6, y int) (pos combinedPos, atEndOfLine bool) {
 	if len(g.positions) == 0 {
-		return combinedPos{}
+		return combinedPos{}, false
 	}
 	i := sort.Search(len(g.positions), func(i int) bool {
 		pos := g.positions[i]
@@ -292,7 +311,7 @@ func (g *glyphIndex) closestToXY(x fixed.Int26_6, y int) combinedPos {
 	// short. Return either the last position or (if there are no
 	// positions) the zero position.
 	if i == len(g.positions) {
-		return g.positions[i-1]
+		return g.positions[i-1], false
 	}
 	first := g.positions[i]
 	// Find the best X coordinate.
@@ -308,14 +327,22 @@ func (g *glyphIndex) closestToXY(x fixed.Int26_6, y int) combinedPos {
 		distance := dist(candidate.x, x)
 		// If we are *really* close to the current position candidate, just choose it.
 		if distance.Round() == 0 {
-			return g.positions[i]
+			return g.positions[i], false
 		}
 		if distance < closestDist {
 			closestDist = distance
 			closest = i
 		}
 	}
-	return g.positions[closest]
+	next := closest + 1
+	hasNext := next < len(g.positions)
+	if hasNext && g.atEndOfLine(g.positions[closest]) {
+		distance := dist(g.lines[line].getLineEnd(), x)
+		if distance < closestDist {
+			return g.positions[next], true
+		}
+	}
+	return g.positions[closest], false
 }
 
 // makeRegion creates a text-aligned rectangle from start to end. The vertical

widget/text.go

@@ -173,14 +173,17 @@ func (e *textView) closestToLineCol(line, col int) combinedPos {
 	return e.index.closestToLineCol(screenPos{line: line, col: col})
 }
 
-func (e *textView) closestToXY(x fixed.Int26_6, y int) combinedPos {
+func (e *textView) closestToXY(x fixed.Int26_6, y int) (combinedPos, bool) {
 	e.makeValid()
 	return e.index.closestToXY(x, y)
 }
 
-func (e *textView) closestToXYGraphemes(x fixed.Int26_6, y int) combinedPos {
+func (e *textView) closestToXYGraphemes(x fixed.Int26_6, y int) (combinedPos, bool) {
 	// Find the closest existing rune position to the provided coordinates.
-	pos := e.closestToXY(x, y)
+	pos, atEndOfLine := e.closestToXY(x, y)
+	if atEndOfLine {
+		return pos, true
+	}
 	// Resolve cluster boundaries on either side of the rune position.
 	firstOption := e.moveByGraphemes(pos.runes, 0)
 	distance := 1
@@ -194,9 +197,9 @@ func (e *textView) closestToXYGraphemes(x fixed.Int26_6, y int) combinedPos {
 	second := e.closestToRune(secondOption)
 	secondDist := absFixed(second.x - x)
 	if firstDist > secondDist {
-		return second
+		return second, false
 	} else {
-		return first
+		return first, false
 	}
 }
 
@@ -214,8 +217,11 @@ func (e *textView) MoveLines(distance int, selAct selectionAction) {
 	x := caretStart.x + e.caret.xoff
 	// Seek to line.
 	pos := e.closestToLineCol(caretStart.lineCol.line+distance, 0)
-	pos = e.closestToXYGraphemes(x, pos.y)
+	pos, atEndOfLine := e.closestToXYGraphemes(x, pos.y)
 	e.caret.start = pos.runes
+	if atEndOfLine && pos.runes > 0 {
+		e.caret.start = pos.runes - 1
+	}
 	e.caret.xoff = x - pos.x
 	e.updateSelection(selAct)
 }
@@ -472,7 +478,8 @@ func (e *textView) scrollAbs(x, y int) {
 func (e *textView) MoveCoord(pos image.Point) {
 	x := fixed.I(pos.X + e.scrollOff.X)
 	y := pos.Y + e.scrollOff.Y
-	e.caret.start = e.closestToXYGraphemes(x, y).runes
+	p, _ := e.closestToXYGraphemes(x, y)
+	e.caret.start = p.runes
 	e.caret.xoff = 0
 }
 
@@ -610,7 +617,7 @@ func (e *textView) MovePages(pages int, selAct selectionAction) {
 	caret := e.closestToRune(e.caret.start)
 	x := caret.x + e.caret.xoff
 	y := caret.y + pages*e.viewSize.Y
-	pos := e.closestToXYGraphemes(x, y)
+	pos, _ := e.closestToXYGraphemes(x, y)
 	e.caret.start = pos.runes
 	e.caret.xoff = x - pos.x
 	e.updateSelection(selAct)