Optimize LightRenderer for slow terminals

src/terminal.go

@@ -46,6 +46,7 @@ type itemLine struct {
 	current  bool
 	selected bool
 	label    string
+	width    int
 	result   Result
 }
 
@@ -678,13 +679,17 @@ func (t *Terminal) printItem(result *Result, line int, i int, current bool) {
 	}
 
 	// Avoid unnecessary redraw
-	newLine := itemLine{current, selected, label, *result}
-	if t.prevLines[i] == newLine {
+	newLine := itemLine{current: current, selected: selected, label: label, result: *result, width: 0}
+	prevLine := t.prevLines[i]
+	if prevLine.current == newLine.current &&
+		prevLine.selected == newLine.selected &&
+		prevLine.label == newLine.label &&
+		prevLine.result == newLine.result {
 		return
 	}
-	t.prevLines[i] = newLine
 
-	t.move(line, 0, true)
+	// Optimized renderer can simply erase to the end of the window
+	t.move(line, 0, t.tui.IsOptimized())
 	t.window.CPrint(tui.ColCursor, t.strong, label)
 	if current {
 		if selected {
@@ -692,15 +697,22 @@ func (t *Terminal) printItem(result *Result, line int, i int, current bool) {
 		} else {
 			t.window.CPrint(tui.ColCurrent, t.strong, " ")
 		}
-		t.printHighlighted(result, t.strong, tui.ColCurrent, tui.ColCurrentMatch, true, true)
+		newLine.width = t.printHighlighted(result, t.strong, tui.ColCurrent, tui.ColCurrentMatch, true, true)
 	} else {
 		if selected {
 			t.window.CPrint(tui.ColSelected, t.strong, ">")
 		} else {
 			t.window.Print(" ")
 		}
-		t.printHighlighted(result, 0, tui.ColNormal, tui.ColMatch, false, true)
+		newLine.width = t.printHighlighted(result, 0, tui.ColNormal, tui.ColMatch, false, true)
 	}
+	if !t.tui.IsOptimized() {
+		fillSpaces := prevLine.width - newLine.width
+		if fillSpaces > 0 {
+			t.window.Print(strings.Repeat(" ", fillSpaces))
+		}
+	}
+	t.prevLines[i] = newLine
 }
 
 func (t *Terminal) trimRight(runes []rune, width int) ([]rune, int) {
@@ -745,17 +757,10 @@ func (t *Terminal) trimLeft(runes []rune, width int) ([]rune, int32) {
 }
 
 func (t *Terminal) overflow(runes []rune, max int) bool {
-	l := 0
-	for _, r := range runes {
-		l += util.RuneWidth(r, l, t.tabstop)
-		if l > max {
-			return true
-		}
-	}
-	return false
+	return t.displayWidthWithLimit(runes, 0, max) > max
 }
 
-func (t *Terminal) printHighlighted(result *Result, attr tui.Attr, col1 tui.ColorPair, col2 tui.ColorPair, current bool, match bool) {
+func (t *Terminal) printHighlighted(result *Result, attr tui.Attr, col1 tui.ColorPair, col2 tui.ColorPair, current bool, match bool) int {
 	item := result.item
 
 	// Overflow
@@ -783,7 +788,8 @@ func (t *Terminal) printHighlighted(result *Result, attr tui.Attr, col1 tui.Colo
 	offsets := result.colorOffsets(charOffsets, t.theme, col2, attr, current)
 	maxWidth := t.window.Width() - 3
 	maxe = util.Constrain(maxe+util.Min(maxWidth/2-2, t.hscrollOff), 0, len(text))
-	if t.overflow(text, maxWidth) {
+	displayWidth := t.displayWidthWithLimit(text, 0, maxWidth)
+	if displayWidth > maxWidth {
 		if t.hscroll {
 			// Stri..
 			if !t.overflow(text[:maxe], maxWidth-2) {
@@ -845,6 +851,7 @@ func (t *Terminal) printHighlighted(result *Result, attr tui.Attr, col1 tui.Colo
 		substr, _ = t.processTabs(text[index:], prefixWidth)
 		t.window.CPrint(col1, attr, substr)
 	}
+	return displayWidth
 }
 
 func numLinesMax(str string, max int) int {

src/tui/light.go

@@ -32,13 +32,18 @@ func openTtyIn() *os.File {
 	return in
 }
 
-// FIXME: Need better handling of non-displayable characters
 func (r *LightRenderer) stderr(str string) {
+	r.stderrInternal(str, true)
+}
+
+// FIXME: Need better handling of non-displayable characters
+func (r *LightRenderer) stderrInternal(str string, allowNLCR bool) {
 	bytes := []byte(str)
 	runes := []rune{}
 	for len(bytes) > 0 {
 		r, sz := utf8.DecodeRune(bytes)
-		if r == utf8.RuneError || r != '\x1b' && r != '\n' && r != '\r' && r < 32 {
+		if r == utf8.RuneError || r < 32 &&
+			r != '\x1b' && (!allowNLCR || r != '\n' && r != '\r') {
 			runes = append(runes, '?')
 		} else {
 			runes = append(runes, r)
@@ -553,6 +558,10 @@ func (r *LightRenderer) DoesAutoWrap() bool {
 	return true
 }
 
+func (r *LightRenderer) IsOptimized() bool {
+	return false
+}
+
 func (r *LightRenderer) NewWindow(top int, left int, width int, height int, border bool) Window {
 	w := &LightWindow{
 		renderer: r,
@@ -594,6 +603,10 @@ func (w *LightWindow) stderr(str string) {
 	w.renderer.stderr(str)
 }
 
+func (w *LightWindow) stderrInternal(str string, allowNLCR bool) {
+	w.renderer.stderrInternal(str, allowNLCR)
+}
+
 func (w *LightWindow) Top() int {
 	return w.top
 }
@@ -703,7 +716,7 @@ func (w *LightWindow) CPrint(pair ColorPair, attr Attr, text string) {
 	} else {
 		w.csiColor(pair.Fg(), pair.Bg(), attr)
 	}
-	w.stderr(text)
+	w.stderrInternal(text, false)
 	w.csi("m")
 }
 
@@ -711,7 +724,7 @@ func (w *LightWindow) cprint2(fg Color, bg Color, attr Attr, text string) {
 	if w.csiColor(fg, bg, attr) {
 		defer w.csi("m")
 	}
-	w.stderr(text)
+	w.stderrInternal(text, false)
 }
 
 type wrappedLine struct {
@@ -754,7 +767,7 @@ func (w *LightWindow) fill(str string, onMove func()) FillReturn {
 				}
 				return FillNextLine
 			}
-			w.stderr(wl.text)
+			w.stderrInternal(wl.text, false)
 			w.posx += wl.displayWidth
 			if j < len(lines)-1 || i < len(allLines)-1 {
 				if w.posy+1 >= w.height {

src/tui/ncurses.go

@@ -279,6 +279,10 @@ func (r *FullscreenRenderer) DoesAutoWrap() bool {
 	return true
 }
 
+func (r *FullscreenRenderer) IsOptimized() bool {
+	return true
+}
+
 func (w *CursesWindow) Fill(str string) FillReturn {
 	if C.waddstr(w.impl, C.CString(str)) == C.OK {
 		return FillContinue

src/tui/tcell.go

@@ -158,6 +158,10 @@ func (r *FullscreenRenderer) DoesAutoWrap() bool {
 	return false
 }
 
+func (r *FullscreenRenderer) IsOptimized() bool {
+	return false
+}
+
 func (r *FullscreenRenderer) Clear() {
 	_screen.Sync()
 	_screen.Clear()

src/tui/tui.go

@@ -204,6 +204,7 @@ type Renderer interface {
 	MaxX() int
 	MaxY() int
 	DoesAutoWrap() bool
+	IsOptimized() bool
 
 	NewWindow(top int, left int, width int, height int, border bool) Window
 }