Implement whitespace preserving wordwrap

entry.go

@@ -32,14 +32,15 @@ func (e *Entry) Draw(p *Painter) {
 	}
 	p.WithStyle(style, func(p *Painter) {
 		s := e.Size()
+		e.text.SetMaxWidth(s.X)
 
 		text := e.visibleText()
 
 		p.FillRect(0, 0, s.X, 1)
 		p.DrawText(0, 0, text)
 
 		if e.IsFocused() {
-			pos := e.text.CursorPos(s.X)
+			pos := e.text.CursorPos()
 			p.DrawCursor(pos.X-e.offset, 0)
 		}
 	})
@@ -56,6 +57,9 @@ func (e *Entry) OnKeyEvent(ev KeyEvent) {
 		return
 	}
 
+	screenWidth := e.Size().X
+	e.text.SetMaxWidth(screenWidth)
+
 	if ev.Key != KeyRune {
 		switch ev.Key {
 		case KeyEnter:
@@ -83,8 +87,7 @@ func (e *Entry) OnKeyEvent(ev KeyEvent) {
 		case KeyRight, KeyCtrlF:
 			e.text.MoveForward()
 
-			screenWidth := e.Size().X
-			isCursorTooFar := e.text.CursorPos(screenWidth).X >= screenWidth
+			isCursorTooFar := e.text.CursorPos().X >= screenWidth
 			isTextLeft := (e.text.Width() - e.offset) > (screenWidth - 1)
 
 			if isCursorTooFar && isTextLeft {
@@ -95,7 +98,7 @@ func (e *Entry) OnKeyEvent(ev KeyEvent) {
 			e.offset = 0
 		case KeyEnd, KeyCtrlE:
 			e.text.MoveToLineEnd()
-			left := e.text.Width() - (e.Size().X - 1)
+			left := e.text.Width() - (screenWidth - 1)
 			if left >= 0 {
 				e.offset = left
 			}
@@ -106,7 +109,7 @@ func (e *Entry) OnKeyEvent(ev KeyEvent) {
 	}
 
 	e.text.WriteRune(ev.Rune)
-	if e.text.CursorPos(e.Size().X).X >= e.Size().X {
+	if e.text.CursorPos().X >= screenWidth {
 		e.offset++
 	}
 	if e.onTextChange != nil {

entry_test.go

@@ -386,6 +386,7 @@ func TestEntry_MoveToStartAndEnd(t *testing.T) {
 		e := NewEntry()
 		e.SetText("Lorem ipsum")
 		e.SetFocused(true)
+		e.text.SetMaxWidth(5)
 		e.offset = 6
 
 		surface := newTestSurface(5, 1)
@@ -397,7 +398,7 @@ func TestEntry_MoveToStartAndEnd(t *testing.T) {
 
 			want := "\nLorem\n"
 
-			if got := e.text.CursorPos(5); got.X != 0 {
+			if got := e.text.CursorPos(); got.X != 0 {
 				t.Errorf("cursor position should be %d, but was %d", 0, got.X)
 			}
 			if e.offset != 0 {
@@ -413,7 +414,7 @@ func TestEntry_MoveToStartAndEnd(t *testing.T) {
 
 			want := "\npsum \n"
 
-			if got := e.text.CursorPos(5); got.X != 11 {
+			if got := e.text.CursorPos(); got.X != 11 {
 				t.Errorf("cursor position should be %d, but was %d", 11, got.X)
 			}
 			if e.offset != 7 {
@@ -430,6 +431,7 @@ func TestEntry_OnKeyBackspaceEvent(t *testing.T) {
 		e := NewEntry()
 		e.SetText("Lorem ipsum")
 		e.SetFocused(true)
+		e.text.SetMaxWidth(5)
 		e.offset = 6
 
 		surface := newTestSurface(5, 1)
@@ -441,7 +443,7 @@ func TestEntry_OnKeyBackspaceEvent(t *testing.T) {
 
 			want := "\nm ips\n"
 
-			if got := e.text.CursorPos(5); got.X != 9 {
+			if got := e.text.CursorPos(); got.X != 9 {
 				t.Errorf("cursor position should be %d, but was %d", 9, got.X)
 			}
 			if e.offset != 4 {

runebuf.go

@@ -4,8 +4,8 @@ import (
 	"image"
 	"strings"
 
+	"github.com/marcusolsson/tui-go/wordwrap"
 	runewidth "github.com/mattn/go-runewidth"
-	wordwrap "github.com/mitchellh/go-wordwrap"
 )
 
 // RuneBuffer provides readline functionality for text widgets.
@@ -14,6 +14,13 @@ type RuneBuffer struct {
 	idx int
 
 	wordwrap bool
+
+	width int
+}
+
+// SetMaxWidth sets the maximum text width.
+func (r *RuneBuffer) SetMaxWidth(w int) {
+	r.width = w
 }
 
 // Width returns the width of the rune buffer, taking into account for CJK.
@@ -55,35 +62,39 @@ func (r *RuneBuffer) Len() int {
 }
 
 // SplitByLine returns the lines for a given width.
-func (r *RuneBuffer) SplitByLine(width int) []string {
-	var text string
-	if r.wordwrap {
-		text = wordwrap.WrapString(r.String(), uint(width))
-	} else {
-		text = r.String()
-	}
-	return strings.Split(text, "\n")
+func (r *RuneBuffer) SplitByLine() []string {
+	return r.getSplitByLine(r.width)
 }
 
-func getSplitByLine(rs []rune, width int, wrap bool) []string {
+func (r *RuneBuffer) getSplitByLine(w int) []string {
 	var text string
-	if wrap {
-		text = wordwrap.WrapString(string(rs), uint(width))
+	if r.wordwrap {
+		text = wordwrap.WrapString(r.String(), w)
 	} else {
-		text = string(rs)
+		text = r.String()
 	}
 	return strings.Split(text, "\n")
 }
 
 // CursorPos returns the coordinate for the cursor for a given width.
-func (r *RuneBuffer) CursorPos(width int) image.Point {
-	if width == 0 {
+func (r *RuneBuffer) CursorPos() image.Point {
+	if r.width == 0 {
 		return image.ZP
 	}
 
-	sp := getSplitByLine(r.buf[:r.idx], width, r.wordwrap)
-
-	return image.Pt(stringWidth(sp[len(sp)-1]), len(sp)-1)
+	sp := r.SplitByLine()
+	var x, y int
+	remaining := r.idx
+	for _, l := range sp {
+		if len(l) < remaining {
+			y++
+			remaining -= len(l) + 1
+		} else {
+			x = remaining
+			break
+		}
+	}
+	return image.Pt(x, y)
 }
 
 func (r *RuneBuffer) String() string {
@@ -120,7 +131,7 @@ func (r *RuneBuffer) MoveToLineStart() {
 // MoveToLineEnd moves the cursor to the end of the current line.
 func (r *RuneBuffer) MoveToLineEnd() {
 	for i := r.idx; i < len(r.buf)-1; i++ {
-		if r.buf[i+1] == '\n' {
+		if r.buf[i] == '\n' {
 			r.idx = i
 			return
 		}
@@ -156,5 +167,5 @@ func (r *RuneBuffer) Kill() {
 }
 
 func (r *RuneBuffer) heightForWidth(w int) int {
-	return len(r.SplitByLine(w))
+	return len(r.getSplitByLine(w))
 }