v0.5.2 tui: titles and labels drawn a column a rune; an unchanged frame writes nothing

* tui: titles, labels and buttons drawn a column a rune

Ten places drew each rune of a title or label at its byte offset, so a
string holding runes of more than one byte drew with holes and ran past the
width it was measured and truncated to: the Pane title, the Modal title and
hint, the Divider label, TabBar titles, Table cells, Form labels, the
TextField placeholder, the ConfirmDialog and AlertDialog buttons, and the
ProgressOverlay title. Each now draws through Region.Text, which counts
columns by rune, within the bound its loop kept; a Form label stays within
its label column, as the byte count meant it to.

* an unchanged frame writes nothing

flush closed every frame with SGR 0, so a frame that changed no cell still
sent four bytes, and an app drawing an idle screen kept writing to the
terminal. The reset now follows only a frame that wrote cells: the next
cell written restates its whole style, and Fini resets on its own.

Each widget, given a title such as "● é · ñ", draws it whole where it drew
it with holes before; a frame flushed twice writes nothing the second time,
where it wrote ESC [ 0 m.

output.go

@@ -100,6 +100,7 @@ func (o *outputBuffer) flush(cells []Cell, width, height int) {
 	}
 
 	w := &o.buf
+	start := w.Len()
 
 	for y := 0; y < height; y++ {
 		rowStart := y * width
@@ -194,7 +195,10 @@ func (o *outputBuffer) flush(cells []Cell, width, height int) {
 		}
 	}
 
-	w.Write(csiSGR0)
+	// A frame that changed no cell writes nothing, the reset included
+	if w.Len() > start {
+		w.Write(csiSGR0)
+	}
 	o.lastValid = false
 }
 

terminal_test.go

@@ -121,6 +121,18 @@ func TestEachCellIsOneColumn(t *testing.T) {
 	}
 }
 
+// A frame that changes no cell writes nothing, so drawing an idle screen
+// again costs the terminal no bytes
+func TestUnchangedFrameWritesNothing(t *testing.T) {
+	o := newOutputBuffer(ColorMode256)
+	frame := []Cell{{Rune: 'a'}, {Rune: 'é'}}
+	o.flush(frame, len(frame), 1)
+	o.buf.Reset()
+	if o.flush(frame, len(frame), 1); o.buf.Len() != 0 {
+		t.Fatalf("unchanged frame wrote %q", o.buf.String())
+	}
+}
+
 // A paste arrives as one event, whatever reads split it into: an escape
 // inside it is text even when a poll times out on it, and a paste the
 // terminal never ends ends when input pauses, whether reads time out or

tui/border.go

@@ -149,10 +149,7 @@ func (r Region) Divider(y int, label string, line LineType, fg color.RGB) {
 			text = Truncate(text, r.W-2)
 			textLen = RuneLen(text)
 		}
-		startX := (r.W - textLen) / 2
-		for i, ch := range text {
-			r.Cell(startX+i, y, ch, fg, color.RGB{}, terminal.AttrBold)
-		}
+		r.Text((r.W-textLen)/2, y, text, fg, color.RGB{}, terminal.AttrBold)
 	}
 }
 

tui/dialog.go

@@ -225,11 +225,7 @@ func (r Region) ConfirmDialog(state *ConfirmState, opts ConfirmOpts) Region {
 			yesBg = style.ButtonFocusBg
 		}
 	}
-	for i, ch := range yesLabel {
-		if buttonX+i < content.W {
-			content.Cell(buttonX+i, buttonY, ch, yesFg, yesBg, terminal.AttrNone)
-		}
-	}
+	content.Text(buttonX, buttonY, yesLabel, yesFg, yesBg, terminal.AttrNone)
 
 	// No button
 	noX := buttonX + yesW + buttonGap
@@ -239,11 +235,7 @@ func (r Region) ConfirmDialog(state *ConfirmState, opts ConfirmOpts) Region {
 		noFg = style.ButtonFocusFg
 		noBg = style.ButtonFocusBg
 	}
-	for i, ch := range noLabel {
-		if noX+i < content.W {
-			content.Cell(noX+i, buttonY, ch, noFg, noBg, terminal.AttrNone)
-		}
-	}
+	content.Text(noX, buttonY, noLabel, noFg, noBg, terminal.AttrNone)
 
 	return content.Sub(0, 0, content.W, buttonY-1)
 }
@@ -317,11 +309,7 @@ func (r Region) AlertDialog(opts AlertOpts) Region {
 	buttonW := RuneLen(buttonLabel)
 	buttonX := (content.W - buttonW) / 2
 
-	for i, ch := range buttonLabel {
-		if buttonX+i < content.W {
-			content.Cell(buttonX+i, buttonY, ch, style.ButtonFocusFg, style.ButtonFocusBg, terminal.AttrNone)
-		}
-	}
+	content.Text(buttonX, buttonY, buttonLabel, style.ButtonFocusFg, style.ButtonFocusBg, terminal.AttrNone)
 
 	return content.Sub(0, 0, content.W, buttonY-1)
 }

tui/form.go

@@ -164,12 +164,7 @@ func (r Region) Form(state *FormState, opts FormOpts) int {
 
 		// Label
 		label := field.Label + ":"
-		for j, ch := range label {
-			if j >= labelW || j >= r.W {
-				break
-			}
-			r.Cell(j, y, ch, style.LabelFg, style.Bg, terminal.AttrNone)
-		}
+		r.Sub(0, y, labelW, 1).Text(0, 0, label, style.LabelFg, style.Bg, terminal.AttrNone)
 
 		// Field area
 		fieldX := labelW

tui/modal.go

@@ -36,10 +36,7 @@ func (r Region) Modal(opts ModalOpts) Region {
 			title = Truncate(title, r.W-4)
 			titleLen = RuneLen(title)
 		}
-		x := (r.W - titleLen) / 2
-		for i, ch := range title {
-			r.Cell(x+i, 0, ch, opts.TitleFg, opts.Bg, terminal.AttrBold)
-		}
+		r.Text((r.W-titleLen)/2, 0, title, opts.TitleFg, opts.Bg, terminal.AttrBold)
 	}
 
 	// Hint right-aligned on top edge
@@ -54,12 +51,7 @@ func (r Region) Modal(opts ModalOpts) Region {
 		if x < r.W/2 {
 			x = r.W / 2
 		}
-		for i, ch := range hint {
-			if x+i >= r.W-1 {
-				break
-			}
-			r.Cell(x+i, 0, ch, opts.HintFg, opts.Bg, terminal.AttrNone)
-		}
+		r.Sub(0, 0, r.W-1, 1).Text(x, 0, hint, opts.HintFg, opts.Bg, terminal.AttrNone)
 	}
 
 	// Return content region

tui/pane.go

@@ -33,13 +33,7 @@ func (r Region) Pane(opts PaneOpts) Region {
 		if RuneLen(title) > r.W-4 {
 			title = Truncate(title, r.W-4)
 		}
-		x := 2
-		for i, ch := range title {
-			if x+i >= r.W-1 {
-				break
-			}
-			r.Cell(x+i, 0, ch, opts.TitleFg, opts.Bg, terminal.AttrBold)
-		}
+		r.Text(2, 0, title, opts.TitleFg, opts.Bg, terminal.AttrBold)
 	}
 
 	// Content region is everything inside the border. The title sits ON the border row.

tui/progress_overlay.go

@@ -194,10 +194,7 @@ func (r Region) ProgressOverlay(opts ProgressOverlayOpts) Region {
 			title = Truncate(title, overlayW-4)
 			titleLen = RuneLen(title)
 		}
-		titleX := (overlayW - titleLen) / 2
-		for i, ch := range title {
-			overlay.Cell(titleX+i, 0, ch, opts.AccentFg, opts.Bg, terminal.AttrBold)
-		}
+		overlay.Text((overlayW-titleLen)/2, 0, title, opts.AccentFg, opts.Bg, terminal.AttrBold)
 	}
 
 	// Content area

tui/tab.go

@@ -64,13 +64,7 @@ func (r Region) TabBar(y int, titles []string, active int, opts TabBarOpts) []Ta
 			r.Cell(x+j, y, ' ', style.Fg, style.Bg, style.Attr)
 		}
 
-		titleStart := x + opts.Padding
-		for j, ch := range title {
-			if titleStart+j >= r.W {
-				break
-			}
-			r.Cell(titleStart+j, y, ch, style.Fg, style.Bg, style.Attr)
-		}
+		r.TextStyled(x+opts.Padding, y, title, style)
 
 		for j := 0; j < opts.Padding; j++ {
 			pos := x + opts.Padding + RuneLen(title) + j

tui/table.go

@@ -171,11 +171,7 @@ func (r Region) renderTableRow(y int, cells []string, widths []int, aligns []Ali
 			startX = x
 		}
 
-		for j, ch := range text {
-			if startX+j < r.W {
-				r.Cell(startX+j, y, ch, style.Fg, style.Bg, style.Attr)
-			}
-		}
+		r.TextStyled(startX, y, text, style)
 
 		x += w
 

tui/textfield.go

@@ -108,12 +108,7 @@ func (r Region) TextField(state *TextFieldState, opts TextFieldOpts) int {
 		if RuneLen(placeholder) > viewportW {
 			placeholder = Truncate(placeholder, viewportW)
 		}
-		for i, ch := range placeholder {
-			if x+i >= contentX+contentW {
-				break
-			}
-			r.Cell(x+i, contentY, ch, style.PlaceholderFg, style.TextBg, terminal.AttrDim)
-		}
+		r.Text(x, contentY, placeholder, style.PlaceholderFg, style.TextBg, terminal.AttrDim)
 	} else {
 		// Scroll indicators
 		if state.Scroll > 0 && x > contentX {

tui/widget_test.go

@@ -467,3 +467,37 @@ func TestWindowShowsTheRowsInView(t *testing.T) {
 	}
 	r.Sub(8, 0, 4, 3).Window(10, &v, MonoTheme.Text, content) // no columns, past the right edge
 }
+
+// A label is drawn a column a rune, so one holding runes of more than a byte
+// keeps them together: each widget draws s as many times as it is given it
+func TestLabelsKeepTheirRunesTogether(t *testing.T) {
+	const s = "● é · ñ"
+	for _, c := range []struct {
+		name string
+		n    int
+		draw func(r Region)
+	}{
+		{"pane", 1, func(r Region) { r.Pane(PaneOpts{Title: s}) }},
+		{"modal", 2, func(r Region) { r.Modal(ModalOpts{Title: s, Hint: s}) }},
+		{"divider", 1, func(r Region) { r.Divider(0, s, LineSingle, color.RGB{}) }},
+		{"tabs", 2, func(r Region) { r.TabBar(0, []string{s, s}, 0, DefaultTabBarOpts()) }},
+		{"table", 2, func(r Region) { r.Table([]string{s}, [][]string{{s}}, TableOpts{}) }},
+		{"form", 1, func(r Region) { r.Form(NewFormState(s), FormOpts{}) }},
+		{"field", 1, func(r Region) { r.TextField(NewTextFieldState(""), TextFieldOpts{Placeholder: s}) }},
+		{"confirm", 4, func(r Region) {
+			r.ConfirmDialog(NewConfirmState(true), ConfirmOpts{Title: s, Message: s, YesLabel: s, NoLabel: s})
+		}},
+		{"alert", 3, func(r Region) { r.AlertDialog(AlertOpts{Title: s, Message: s, Button: s}) }},
+		{"progress", 1, func(r Region) { r.ProgressOverlay(DefaultProgressOpts(s, "", ProgressSpinner)) }},
+	} {
+		r := canvas(48, 14, MonoTheme)
+		c.draw(r)
+		rows := make([]string, r.H)
+		for y := range rows {
+			rows[y] = row(r, y)
+		}
+		if got := strings.Count(strings.Join(rows, "\n"), s); got != c.n {
+			t.Errorf("%s: %d of %d, rows %q", c.name, got, c.n, rows)
+		}
+	}
+}