fix(html): retain 240x80 encoder scratch and clear stale payload slots

The row-start scratch is sized for up to 80 rows up front, so frames taller
than 64 rows no longer drop the encoder scratch on every update. CopyFrom
clears the reused payload tail so graphemes and hyperlinks from a larger
earlier frame are not kept alive. The size probe is excluded from selection,
and copyFrame drops a branch that could not run.

A property test drives one renderer through edits with payloads and
equivalent styles, aborts, resets, stale commits and failed prepares, and
checks each update against a cell-by-cell diff of the committed shadow.

commit: c6dd596575459bd57c9074a0ca96d6391b5eed5d
author: brice · 20d ago · 2026-10-02 16:37 UTC
parent: f49c70a
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

5 files · +132 -7

M core/frame_copy.go +6 -0


@@ -45,7 +45,13 @@ func (f *Frame) CopyFrom(src Frame) {
45	45		clear(dst.styleIndex)
46	46		}
47	47		maps.Copy(dst.styleIndex, from.styleIndex)
	48	+	// Payloads hold strings: clear the reused tail so stale graphemes and
	49	+	// hyperlinks are not kept alive by the backing array.
	50	+	oldPayloads := len(dst.payloads)
48	51		dst.payloads = append(dst.payloads[:0], from.payloads...)
	52	+	if oldPayloads > len(dst.payloads) {
	53	+	clear(dst.payloads[len(dst.payloads):oldPayloads])
	54	+	}
49	55		dst.freePayloads = append(dst.freePayloads[:0], from.freePayloads...)
50	56		dst.payloadBytes = from.payloadBytes
51	57		if dst.payloadIndex == nil && len(from.payloadIndex) > 0 {


@@ -45,7 +45,13 @@ func (f *Frame) CopyFrom(src Frame) {
45	clear(dst.styleIndex)	45		clear(dst.styleIndex)
46	}	46		}
47	maps.Copy(dst.styleIndex, from.styleIndex)	47		maps.Copy(dst.styleIndex, from.styleIndex)
		48	+	// Payloads hold strings: clear the reused tail so stale graphemes and
		49	+	// hyperlinks are not kept alive by the backing array.
		50	+	oldPayloads := len(dst.payloads)
48	dst.payloads = append(dst.payloads[:0], from.payloads...)	51		dst.payloads = append(dst.payloads[:0], from.payloads...)
		52	+	if oldPayloads > len(dst.payloads) {
		53	+	clear(dst.payloads[len(dst.payloads):oldPayloads])
		54	+	}
49	dst.freePayloads = append(dst.freePayloads[:0], from.freePayloads...)	55		dst.freePayloads = append(dst.freePayloads[:0], from.freePayloads...)
50	dst.payloadBytes = from.payloadBytes	56		dst.payloadBytes = from.payloadBytes
51	if dst.payloadIndex == nil && len(from.payloadIndex) > 0 {	57		if dst.payloadIndex == nil && len(from.payloadIndex) > 0 {

M core/frame_copy_test.go +18 -0


@@ -136,6 +136,24 @@ func TestCopyFromReleasesStorageWhenSourceShrinks(t *testing.T) {
136	136		}
137	137		}
138	138
	139	+	func TestCopyFromClearsStalePayloadSlots(t *testing.T) {
	140	+	src := copyTestFrame(t, 8, 2, 'a')
	141	+	dst := NewFrame(8, 2)
	142	+	for x := range 8 {
	143	+	dst.Set(x, 0, Cell{Rune: 'x', Payload: copyTestPayload(t, "", "https://example.test/"+string(rune('a'+x)))})
	144	+	}
	145	+	old := len(dst.page.payloads)
	146	+	dst.CopyFrom(src)
	147	+	if len(dst.page.payloads) >= old {
	148	+	t.Fatalf("test needs a source with fewer payload slots: %d >= %d", len(dst.page.payloads), old)
	149	+	}
	150	+	for i, slot := range dst.page.payloads[len(dst.page.payloads):old] {
	151	+	if slot != (payloadSlot{}) {
	152	+	t.Fatalf("stale payload slot %d still holds %+v", len(dst.page.payloads)+i, slot.value)
	153	+	}
	154	+	}
	155	+	}
	156	+
139	157		func TestRowsEqualAt(t *testing.T) {
140	158		a := copyTestFrame(t, 10, 4, 'a')
141	159		b := a.Clone()


@@ -136,6 +136,24 @@ func TestCopyFromReleasesStorageWhenSourceShrinks(t *testing.T) {
136	}	136		}
137	}	137		}
138		138
		139	+	func TestCopyFromClearsStalePayloadSlots(t *testing.T) {
		140	+	src := copyTestFrame(t, 8, 2, 'a')
		141	+	dst := NewFrame(8, 2)
		142	+	for x := range 8 {
		143	+	dst.Set(x, 0, Cell{Rune: 'x', Payload: copyTestPayload(t, "", "https://example.test/"+string(rune('a'+x)))})
		144	+	}
		145	+	old := len(dst.page.payloads)
		146	+	dst.CopyFrom(src)
		147	+	if len(dst.page.payloads) >= old {
		148	+	t.Fatalf("test needs a source with fewer payload slots: %d >= %d", len(dst.page.payloads), old)
		149	+	}
		150	+	for i, slot := range dst.page.payloads[len(dst.page.payloads):old] {
		151	+	if slot != (payloadSlot{}) {
		152	+	t.Fatalf("stale payload slot %d still holds %+v", len(dst.page.payloads)+i, slot.value)
		153	+	}
		154	+	}
		155	+	}
		156	+
139	func TestRowsEqualAt(t *testing.T) {	157		func TestRowsEqualAt(t *testing.T) {
140	a := copyTestFrame(t, 10, 4, 'a')	158		a := copyTestFrame(t, 10, 4, 'a')
141	b := a.Clone()	159		b := a.Clone()

M html/renderer.go +10 -7


@@ -209,17 +209,18 @@ func (r *Renderer) materializeCellSource(source CellSource) (core.Frame, error)
209	209		}
210	210
211	211		// copyFrame copies a validated frame into the spare page, which the returned
212		-	// frame then owns.
	212	+	// frame then owns. CopyFrom always succeeds here: src passed Validate.
213	213		func (r *Renderer) copyFrame(src core.Frame) core.Frame {
214	214		frame := r.spare
215	215		r.spare = core.Frame{}
216	216		frame.CopyFrom(src)
217		-	if frame.Width != src.Width \|\| frame.Height != src.Height {
218		-	return src.Clone()
219		-	}
220	217		return frame
221	218		}
222	219
	220	+	// maxRetainedRows bounds the row count whose encoder scratch the renderer
	221	+	// keeps between updates.
	222	+	const maxRetainedRows = 80
	223	+
223	224		// normalizeWrapPendingCursor maps the deferred-wrap one-past-end column
224	225		// produced after writing the last column with autowrap enabled onto the
225	226		// last visible column. It leaves every in-bounds cursor untouched.

@@ -291,13 +292,15 @@ func (r *Renderer) buildUpdate(frame core.Frame, scratch []core.Cell, snapshot b
291	292		if cap(ends) < frame.Width {
292	293		ends = make([]int, 0, frame.Width)
293	294		text = make([]byte, 0, frame.Width)
294		-	rowStarts = make([]int, 0, 4)
	295	+	}
	296	+	if cap(rowStarts) < min(frame.Height, maxRetainedRows) {
	297	+	rowStarts = make([]int, 0, min(frame.Height, maxRetainedRows))
295	298		}
296	299		defer func() {
297	300		// Keep scratch for frames up to the common 240x80 size only, so one
298	301		// huge snapshot does not pin its buffers for the renderer lifetime.
299		-	const maxRetainedCells = 240 * 80
300		-	if cap(ends) <= maxRetainedCells && cap(text) <= 4*maxRetainedCells && cap(rowStarts) <= 80 {
	302	+	const maxRetainedCells = 240 * maxRetainedRows
	303	+	if cap(ends) <= maxRetainedCells && cap(text) <= 4*maxRetainedCells && cap(rowStarts) <= maxRetainedRows {
301	304		r.ends, r.text, r.rowStarts = ends, text, rowStarts
302	305		}
303	306		}()

 }
 // copyFrame copies a validated frame into the spare page, which the returned
-// frame then owns.
+// frame then owns. CopyFrom always succeeds here: src passed Validate.
 func (r *Renderer) copyFrame(src core.Frame) core.Frame {
 	frame := r.spare
 	r.spare = core.Frame{}
 	frame.CopyFrom(src)
-	if frame.Width != src.Width || frame.Height != src.Height {
-		return src.Clone()
-	}
 	return frame
 }
+// maxRetainedRows bounds the row count whose encoder scratch the renderer
+// keeps between updates.
+const maxRetainedRows = 80
 // normalizeWrapPendingCursor maps the deferred-wrap one-past-end column
 // produced after writing the last column with autowrap enabled onto the
 // last visible column. It leaves every in-bounds cursor untouched.
 	if cap(ends) < frame.Width {
 		ends = make([]int, 0, frame.Width)
 		text = make([]byte, 0, frame.Width)
-		rowStarts = make([]int, 0, 4)
+	}
+	if cap(rowStarts) < min(frame.Height, maxRetainedRows) {
+		rowStarts = make([]int, 0, min(frame.Height, maxRetainedRows))
 	}
 	defer func() {
 		// Keep scratch for frames up to the common 240x80 size only, so one
 		// huge snapshot does not pin its buffers for the renderer lifetime.
-		const maxRetainedCells = 240 * 80
+		const maxRetainedCells = 240 * maxRetainedRows
-		if cap(ends) <= maxRetainedCells && cap(text) <= 4*maxRetainedCells && cap(rowStarts) <= 80 {
+		if cap(ends) <= maxRetainedCells && cap(text) <= 4*maxRetainedCells && cap(rowStarts) <= maxRetainedRows {
 			r.ends, r.text, r.rowStarts = ends, text, rowStarts
 		}
 	}()

M html/renderer_test.go +97 -0


@@ -435,6 +435,103 @@ func TestAbortThenPrepareKeepsCommittedShadow(t *testing.T) {
435	435		require.Empty(t, steady.Update().Rows)
436	436		}
437	437
	438	+	func TestRendererKeepsEncoderScratchAt240x80(t *testing.T) {
	439	+	frames := [2]core.Frame{core.NewFrame(240, 80), core.NewFrame(240, 80)}
	440	+	for y := range 80 {
	441	+	for x := range 240 {
	442	+	frames[0].Set(x, y, core.Cell{Rune: 'a'})
	443	+	frames[1].Set(x, y, core.Cell{Rune: 'b'})
	444	+	}
	445	+	}
	446	+	renderer, err := New(Options{})
	447	+	require.NoError(t, err)
	448	+	for step := range 2 {
	449	+	prepared, err := renderer.Prepare(frames[step], nil, false, Cursor{})
	450	+	require.NoError(t, err)
	451	+	require.NoError(t, prepared.Commit())
	452	+	}
	453	+	require.GreaterOrEqual(t, cap(renderer.rowStarts), 80, "row-start scratch was not retained")
	454	+	require.GreaterOrEqual(t, cap(renderer.ends), 240, "run-end scratch was not retained")
	455	+	}
	456	+
	457	+	// TestRendererMatchesFreshRendererAcrossTransactions drives one renderer
	458	+	// (reused spare pages and scratch) through random edits with payloads and
	459	+	// equivalent styles, aborts, resets, stale commits and failed prepares. Most
	460	+	// steps commit and keep editing, so the shadow and spare pages alternate.
	461	+	// Every update must list exactly the rows that differ from a cloned committed
	462	+	// shadow (compared cell by cell with Cell.Equal) and encode the source frame.
	463	+	func TestRendererMatchesFreshRendererAcrossTransactions(t *testing.T) {
	464	+	rng := rand.New(rand.NewSource(7))
	465	+	link := func(i int) core.CellPayload {
	466	+	payload, err := core.NewCellPayload("", "https://example.test/"+string(rune('a'+i)))
	467	+	require.NoError(t, err)
	468	+	return payload
	469	+	}
	470	+	bold := core.DefaultStyle()
	471	+	bold.Bold = true
	472	+	equivalent := bold
	473	+	equivalent.ForegroundRGB = core.RGB{R: 1} // inactive RGB: same style
	474	+	for seed := range 30 {
	475	+	width, height := 2+rng.Intn(10), 1+rng.Intn(5)
	476	+	frame := core.NewFrame(width, height)
	477	+	renderer, err := New(Options{})
	478	+	require.NoError(t, err)
	479	+	var committed core.Frame
	480	+	var stale *PreparedDraw
	481	+	for step := range 60 {
	482	+	for range rng.Intn(4) {
	483	+	cell := core.Cell{Rune: rune('a' + rng.Intn(4))}
	484	+	switch rng.Intn(4) {
	485	+	case 0:
	486	+	cell.Style = bold
	487	+	case 1:
	488	+	cell.Style = equivalent
	489	+	case 2:
	490	+	cell.Payload = link(rng.Intn(3))
	491	+	}
	492	+	frame.Set(rng.Intn(width), rng.Intn(height), cell)
	493	+	}
	494	+	if stale != nil && rng.Intn(3) == 0 {
	495	+	require.ErrorIs(t, stale.Commit(), ErrStaleDraw)
	496	+	stale = nil
	497	+	}
	498	+	if rng.Intn(10) == 0 {
	499	+	// A failed prepare must not lose or corrupt the spare page.
	500	+	_, err := renderer.Prepare(frame, nil, false, Cursor{Row: height})
	501	+	require.Error(t, err)
	502	+	}
	503	+
	504	+	want := []int{}
	505	+	for y := range height {
	506	+	for x := range width {
	507	+	if committed.Width == 0 \|\| !frame.Cell(x, y).Equal(committed.Cell(x, y)) {
	508	+	want = append(want, y)
	509	+	break
	510	+	}
	511	+	}
	512	+	}
	513	+	got, err := renderer.Prepare(frame, nil, false, Cursor{})
	514	+	require.NoError(t, err, "seed %d step %d", seed, step)
	515	+	update := got.Update()
	516	+	require.Equal(t, committed.Width == 0, update.Snapshot, "seed %d step %d", seed, step)
	517	+	require.Equal(t, want, rowIndexes(update), "seed %d step %d", seed, step)
	518	+	requireRunsMatchFrame(t, update, frame, step)
	519	+
	520	+	switch k := rng.Intn(20); {
	521	+	case k == 0:
	522	+	renderer.Reset()
	523	+	committed = core.Frame{}
	524	+	stale = got
	525	+	case k < 4:
	526	+	require.NoError(t, got.Abort())
	527	+	default:
	528	+	require.NoError(t, got.Commit())
	529	+	committed = frame.Clone()
	530	+	}
	531	+	}
	532	+	}
	533	+	}
	534	+
438	535		func rowIndexes(update Update) []int {
439	536		rows := make([]int, 0, len(update.Rows))
440	537		for _, row := range update.Rows {


@@ -435,6 +435,103 @@ func TestAbortThenPrepareKeepsCommittedShadow(t *testing.T) {
435	require.Empty(t, steady.Update().Rows)	435		require.Empty(t, steady.Update().Rows)
436	}	436		}
437		437
		438	+	func TestRendererKeepsEncoderScratchAt240x80(t *testing.T) {
		439	+	frames := [2]core.Frame{core.NewFrame(240, 80), core.NewFrame(240, 80)}
		440	+	for y := range 80 {
		441	+	for x := range 240 {
		442	+	frames[0].Set(x, y, core.Cell{Rune: 'a'})
		443	+	frames[1].Set(x, y, core.Cell{Rune: 'b'})
		444	+	}
		445	+	}
		446	+	renderer, err := New(Options{})
		447	+	require.NoError(t, err)
		448	+	for step := range 2 {
		449	+	prepared, err := renderer.Prepare(frames[step], nil, false, Cursor{})
		450	+	require.NoError(t, err)
		451	+	require.NoError(t, prepared.Commit())
		452	+	}
		453	+	require.GreaterOrEqual(t, cap(renderer.rowStarts), 80, "row-start scratch was not retained")
		454	+	require.GreaterOrEqual(t, cap(renderer.ends), 240, "run-end scratch was not retained")
		455	+	}
		456	+
		457	+	// TestRendererMatchesFreshRendererAcrossTransactions drives one renderer
		458	+	// (reused spare pages and scratch) through random edits with payloads and
		459	+	// equivalent styles, aborts, resets, stale commits and failed prepares. Most
		460	+	// steps commit and keep editing, so the shadow and spare pages alternate.
		461	+	// Every update must list exactly the rows that differ from a cloned committed
		462	+	// shadow (compared cell by cell with Cell.Equal) and encode the source frame.
		463	+	func TestRendererMatchesFreshRendererAcrossTransactions(t *testing.T) {
		464	+	rng := rand.New(rand.NewSource(7))
		465	+	link := func(i int) core.CellPayload {
		466	+	payload, err := core.NewCellPayload("", "https://example.test/"+string(rune('a'+i)))
		467	+	require.NoError(t, err)
		468	+	return payload
		469	+	}
		470	+	bold := core.DefaultStyle()
		471	+	bold.Bold = true
		472	+	equivalent := bold
		473	+	equivalent.ForegroundRGB = core.RGB{R: 1} // inactive RGB: same style
		474	+	for seed := range 30 {
		475	+	width, height := 2+rng.Intn(10), 1+rng.Intn(5)
		476	+	frame := core.NewFrame(width, height)
		477	+	renderer, err := New(Options{})
		478	+	require.NoError(t, err)
		479	+	var committed core.Frame
		480	+	var stale *PreparedDraw
		481	+	for step := range 60 {
		482	+	for range rng.Intn(4) {
		483	+	cell := core.Cell{Rune: rune('a' + rng.Intn(4))}
		484	+	switch rng.Intn(4) {
		485	+	case 0:
		486	+	cell.Style = bold
		487	+	case 1:
		488	+	cell.Style = equivalent
		489	+	case 2:
		490	+	cell.Payload = link(rng.Intn(3))
		491	+	}
		492	+	frame.Set(rng.Intn(width), rng.Intn(height), cell)
		493	+	}
		494	+	if stale != nil && rng.Intn(3) == 0 {
		495	+	require.ErrorIs(t, stale.Commit(), ErrStaleDraw)
		496	+	stale = nil
		497	+	}
		498	+	if rng.Intn(10) == 0 {
		499	+	// A failed prepare must not lose or corrupt the spare page.
		500	+	_, err := renderer.Prepare(frame, nil, false, Cursor{Row: height})
		501	+	require.Error(t, err)
		502	+	}
		503	+
		504	+	want := []int{}
		505	+	for y := range height {
		506	+	for x := range width {
		507	+	if committed.Width == 0 \|\| !frame.Cell(x, y).Equal(committed.Cell(x, y)) {
		508	+	want = append(want, y)
		509	+	break
		510	+	}
		511	+	}
		512	+	}
		513	+	got, err := renderer.Prepare(frame, nil, false, Cursor{})
		514	+	require.NoError(t, err, "seed %d step %d", seed, step)
		515	+	update := got.Update()
		516	+	require.Equal(t, committed.Width == 0, update.Snapshot, "seed %d step %d", seed, step)
		517	+	require.Equal(t, want, rowIndexes(update), "seed %d step %d", seed, step)
		518	+	requireRunsMatchFrame(t, update, frame, step)
		519	+
		520	+	switch k := rng.Intn(20); {
		521	+	case k == 0:
		522	+	renderer.Reset()
		523	+	committed = core.Frame{}
		524	+	stale = got
		525	+	case k < 4:
		526	+	require.NoError(t, got.Abort())
		527	+	default:
		528	+	require.NoError(t, got.Commit())
		529	+	committed = frame.Clone()
		530	+	}
		531	+	}
		532	+	}
		533	+	}
		534	+
438	func rowIndexes(update Update) []int {	535		func rowIndexes(update Update) []int {
439	rows := make([]int, 0, len(update.Rows))	536		rows := make([]int, 0, len(update.Rows))
440	for _, row := range update.Rows {	537		for _, row := range update.Rows {

M html/terminal.css +1 -0


@@ -76,6 +76,7 @@
76	76		white-space: pre;
77	77		visibility: hidden;
78	78		pointer-events: none;
	79	+	user-select: none;
79	80		}
80	81
81	82		.vev-terminal__cell--bold { font-weight: 700; }


@@ -76,6 +76,7 @@
76	white-space: pre;	76		white-space: pre;
77	visibility: hidden;	77		visibility: hidden;
78	pointer-events: none;	78		pointer-events: none;
		79	+	user-select: none;
79	}	80		}
80		81
81	.vev-terminal__cell--bold { font-weight: 700; }	82		.vev-terminal__cell--bold { font-weight: 700; }