Merge pull request #171 from bnema/fix/viewport-sync-after-delete

fix(vt): clear erased characters during viewport sync

commit: cc1081385397f18e0a5bdb1acb674bf01e4a0205
author: bnema · 2mo ago · 2026-08-03 07:54 UTC
committer: GitHub · 2mo ago · 2026-08-03 07:54 UTC
merge of: 090a62a + bc06f3f · diff against the first parent
signature: GPG UnverifiedB5690EEEBB952194 The key is unknown

2 files · +87 -0

M pkg/vt/screen_csi.go +17 -0


@@ -99,6 +99,8 @@ func (s *Screen) applyCSI(params string, cmd byte) {
99	99		mode = parts[0]
100	100		}
101	101		s.clearLineMode(mode)
	102	+	case 'X':
	103	+	s.eraseChars(firstPositive(parts, 1))
102	104		case 'S':
103	105		s.scrollUpBy(firstPositive(parts, 1))
104	106		case 'T':

@@ -439,6 +441,21 @@ func (s *Screen) clearLineMode(mode int) {
439	441		}
440	442		}
441	443
	444	+	func (s *Screen) eraseChars(n int) {
	445	+	if n <= 0 {
	446	+	return
	447	+	}
	448	+	s.clampCursor()
	449	+	if remaining := s.Frame.Width - s.Col; n > remaining {
	450	+	n = remaining
	451	+	}
	452	+	end := s.Col + n
	453	+	start, width := s.clearRow(s.Row, s.Col, end)
	454	+	if width > 0 {
	455	+	s.record(renderer.Damage{Kind: renderer.DamageClear, X: start, Y: s.Row, Width: width, Height: 1, Count: 1})
	456	+	}
	457	+	}
	458	+
442	459		func (s *Screen) clampCursor() {
443	460		s.Row = clamp(s.Row, 0, s.Frame.Height-1)
444	461		s.Col = clamp(s.Col, 0, s.Frame.Width-1)


@@ -99,6 +99,8 @@ func (s *Screen) applyCSI(params string, cmd byte) {
99	mode = parts[0]	99		mode = parts[0]
100	}	100		}
101	s.clearLineMode(mode)	101		s.clearLineMode(mode)
		102	+	case 'X':
		103	+	s.eraseChars(firstPositive(parts, 1))
102	case 'S':	104		case 'S':
103	s.scrollUpBy(firstPositive(parts, 1))	105		s.scrollUpBy(firstPositive(parts, 1))
104	case 'T':	106		case 'T':

@@ -439,6 +441,21 @@ func (s *Screen) clearLineMode(mode int) {
439	}	441		}
440	}	442		}
441		443
		444	+	func (s *Screen) eraseChars(n int) {
		445	+	if n <= 0 {
		446	+	return
		447	+	}
		448	+	s.clampCursor()
		449	+	if remaining := s.Frame.Width - s.Col; n > remaining {
		450	+	n = remaining
		451	+	}
		452	+	end := s.Col + n
		453	+	start, width := s.clearRow(s.Row, s.Col, end)
		454	+	if width > 0 {
		455	+	s.record(renderer.Damage{Kind: renderer.DamageClear, X: start, Y: s.Row, Width: width, Height: 1, Count: 1})
		456	+	}
		457	+	}
		458	+
442	func (s *Screen) clampCursor() {	459		func (s *Screen) clampCursor() {
443	s.Row = clamp(s.Row, 0, s.Frame.Height-1)	460		s.Row = clamp(s.Row, 0, s.Frame.Height-1)
444	s.Col = clamp(s.Col, 0, s.Frame.Width-1)	461		s.Col = clamp(s.Col, 0, s.Frame.Width-1)

M pkg/vt/screen_csi_test.go +70 -0

@@ -1,6 +1,7 @@
1	1		package vt
2	2
3	3		import (
	4	+	"strconv"
4	5		"testing"
5	6
6	7		"github.com/bnema/vev/pkg/renderer"

@@ -608,6 +609,75 @@ func TestClearAndErase(t *testing.T) {
608	609		}
609	610		}
610	611
	612	+	func TestEraseCharacters(t *testing.T) {
	613	+	maxInt := strconv.Itoa(int(^uint(0) >> 1))
	614	+	tests := []struct {
	615	+	name string
	616	+	width int
	617	+	row int
	618	+	initial string
	619	+	seq string
	620	+	wantRow string
	621	+	wantCol int
	622	+	wantDamage []renderer.Damage
	623	+	}{
	624	+	{
	625	+	name: "explicit count",
	626	+	width: 50,
	627	+	row: 1,
	628	+	initial: ` // scroll-method "on-button-down"`,
	629	+	seq: "\x1b[19Gbutton 273\x1b[13X",
	630	+	wantRow: " // scroll-button 273",
	631	+	wantCol: 28,
	632	+	wantDamage: []renderer.Damage{
	633	+	{Kind: renderer.DamageText, X: 18, Y: 1, Width: 10, Height: 1, Count: 1},
	634	+	{Kind: renderer.DamageClear, X: 28, Y: 1, Width: 13, Height: 1, Count: 1},
	635	+	},
	636	+	},
	637	+	{
	638	+	name: "omitted count erases exactly one cell",
	639	+	width: 6,
	640	+	row: 1,
	641	+	initial: "abcdef",
	642	+	seq: "\x1b[3G\x1b[X",
	643	+	wantRow: "ab def",
	644	+	wantCol: 2,
	645	+	wantDamage: []renderer.Damage{{Kind: renderer.DamageClear, X: 2, Y: 1, Width: 1, Height: 1, Count: 1}},
	646	+	},
	647	+	{
	648	+	name: "maximum count clips to screen edge",
	649	+	width: 6,
	650	+	row: 1,
	651	+	initial: "abcdef",
	652	+	seq: "\x1b[4G\x1b[" + maxInt + "X",
	653	+	wantRow: "abc",
	654	+	wantCol: 3,
	655	+	wantDamage: []renderer.Damage{{Kind: renderer.DamageClear, X: 3, Y: 1, Width: 3, Height: 1, Count: 1}},
	656	+	},
	657	+	}
	658	+
	659	+	for _, tt := range tests {
	660	+	t.Run(tt.name, func(t *testing.T) {
	661	+	s := NewScreen(tt.width, 2)
	662	+	s.Write([]byte("\x1b[2;1H"))
	663	+	s.Write([]byte(tt.initial))
	664	+	s.ClearDamage()
	665	+	s.Write([]byte(tt.seq))
	666	+
	667	+	for x := range tt.width {
	668	+	want := ' '
	669	+	if x < len(tt.wantRow) {
	670	+	want = rune(tt.wantRow[x])
	671	+	}
	672	+	require.Equal(t, want, cellAt(s, x, tt.row).Rune, "cell(%d,%d)", x, tt.row)
	673	+	}
	674	+	require.Equal(t, tt.row, s.Row)
	675	+	require.Equal(t, tt.wantCol, s.Col)
	676	+	require.Equal(t, tt.wantDamage, s.Damage())
	677	+	})
	678	+	}
	679	+	}
	680	+
611	681		func TestBackgroundColorErase(t *testing.T) {
612	682		tests := []struct {
613	683		name string

@@ -1,6 +1,7 @@
1	package vt	1		package vt
2		2
3	import (	3		import (
		4	+	"strconv"
4	"testing"	5		"testing"
5		6
6	"github.com/bnema/vev/pkg/renderer"	7		"github.com/bnema/vev/pkg/renderer"

@@ -608,6 +609,75 @@ func TestClearAndErase(t *testing.T) {
608	}	609		}
609	}	610		}
610		611
		612	+	func TestEraseCharacters(t *testing.T) {
		613	+	maxInt := strconv.Itoa(int(^uint(0) >> 1))
		614	+	tests := []struct {
		615	+	name string
		616	+	width int
		617	+	row int
		618	+	initial string
		619	+	seq string
		620	+	wantRow string
		621	+	wantCol int
		622	+	wantDamage []renderer.Damage
		623	+	}{
		624	+	{
		625	+	name: "explicit count",
		626	+	width: 50,
		627	+	row: 1,
		628	+	initial: ` // scroll-method "on-button-down"`,
		629	+	seq: "\x1b[19Gbutton 273\x1b[13X",
		630	+	wantRow: " // scroll-button 273",
		631	+	wantCol: 28,
		632	+	wantDamage: []renderer.Damage{
		633	+	{Kind: renderer.DamageText, X: 18, Y: 1, Width: 10, Height: 1, Count: 1},
		634	+	{Kind: renderer.DamageClear, X: 28, Y: 1, Width: 13, Height: 1, Count: 1},
		635	+	},
		636	+	},
		637	+	{
		638	+	name: "omitted count erases exactly one cell",
		639	+	width: 6,
		640	+	row: 1,
		641	+	initial: "abcdef",
		642	+	seq: "\x1b[3G\x1b[X",
		643	+	wantRow: "ab def",
		644	+	wantCol: 2,
		645	+	wantDamage: []renderer.Damage{{Kind: renderer.DamageClear, X: 2, Y: 1, Width: 1, Height: 1, Count: 1}},
		646	+	},
		647	+	{
		648	+	name: "maximum count clips to screen edge",
		649	+	width: 6,
		650	+	row: 1,
		651	+	initial: "abcdef",
		652	+	seq: "\x1b[4G\x1b[" + maxInt + "X",
		653	+	wantRow: "abc",
		654	+	wantCol: 3,
		655	+	wantDamage: []renderer.Damage{{Kind: renderer.DamageClear, X: 3, Y: 1, Width: 3, Height: 1, Count: 1}},
		656	+	},
		657	+	}
		658	+
		659	+	for _, tt := range tests {
		660	+	t.Run(tt.name, func(t *testing.T) {
		661	+	s := NewScreen(tt.width, 2)
		662	+	s.Write([]byte("\x1b[2;1H"))
		663	+	s.Write([]byte(tt.initial))
		664	+	s.ClearDamage()
		665	+	s.Write([]byte(tt.seq))
		666	+
		667	+	for x := range tt.width {
		668	+	want := ' '
		669	+	if x < len(tt.wantRow) {
		670	+	want = rune(tt.wantRow[x])
		671	+	}
		672	+	require.Equal(t, want, cellAt(s, x, tt.row).Rune, "cell(%d,%d)", x, tt.row)
		673	+	}
		674	+	require.Equal(t, tt.row, s.Row)
		675	+	require.Equal(t, tt.wantCol, s.Col)
		676	+	require.Equal(t, tt.wantDamage, s.Damage())
		677	+	})
		678	+	}
		679	+	}
		680	+
611	func TestBackgroundColorErase(t *testing.T) {	681		func TestBackgroundColorErase(t *testing.T) {
612	tests := []struct {	682		tests := []struct {
613	name string	683		name string