fix(vt): bound pending screen damage

commit: 22dd02927a2d406c9d9f978cffac6f96183ac2ee
author: brice · 3mo ago · 2026-07-12 09:12 UTC
parent: ef75ff9
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

2 files · +18 -2

M pkg/vt/screen.go +17 -1


@@ -35,6 +35,10 @@ type screenState struct {
35	35		// so keep this value in sync if that payload cap changes.
36	36		const maxEscapeBufferLen = 128 * 1024
37	37
	38	+	// maxPendingDamage bounds metadata retained while no render transaction can
	39	+	// acknowledge a screen. Saturation falls back to one exact full redraw.
	40	+	const maxPendingDamage = 1024
	41	+
38	42		const (
39	43		// ColorSchemeReportDark is the DEC 2031 dark-scheme report.
40	44		ColorSchemeReportDark = "\x1b[?997;1n"

@@ -88,6 +92,7 @@ type Screen struct {
88	92
89	93		damage []renderer.Damage
90	94		damageGeneration uint64
	95	+	damageSaturated bool
91	96		escapeBuf []byte
92	97		csiScratch []int
93	98		sgrScratch []int

@@ -173,7 +178,10 @@ type DamageCapture struct {
173	178		// Damage returns the current damage list. The caller must not modify the
174	179		// returned slice; ClearDamage must be called after the damage is consumed.
175	180		func (s *Screen) Damage() []renderer.Damage { return s.damage }
176		-	func (s *Screen) ClearDamage() { s.damage = s.damage[:0] }
	181	+	func (s *Screen) ClearDamage() {
	182	+	s.damage = s.damage[:0]
	183	+	s.damageSaturated = false
	184	+	}
177	185
178	186		// CaptureDamage snapshots pending damage without consuming it.
179	187		func (s *Screen) CaptureDamage() DamageCapture {

@@ -625,6 +633,14 @@ func (s *Screen) normalizedRegion(top, bottom int) (int, int, bool) {
625	633
626	634		func (s *Screen) record(d renderer.Damage) {
627	635		s.damageGeneration++
	636	+	if s.damageSaturated {
	637	+	return
	638	+	}
	639	+	if len(s.damage) >= maxPendingDamage {
	640	+	s.damage = []renderer.Damage{renderer.FullRedraw()}
	641	+	s.damageSaturated = true
	642	+	return
	643	+	}
628	644		// Replace FullRedraw with the first concrete damage item.
629	645		if len(s.damage) == 1 && s.damage[0].Kind == renderer.DamageFullRedraw {
630	646		s.damage[0] = d

 // so keep this value in sync if that payload cap changes.
 const maxEscapeBufferLen = 128 * 1024
+// maxPendingDamage bounds metadata retained while no render transaction can
+// acknowledge a screen. Saturation falls back to one exact full redraw.
+const maxPendingDamage = 1024
 const (
 	// ColorSchemeReportDark is the DEC 2031 dark-scheme report.
 	ColorSchemeReportDark = "\x1b[?997;1n"
 	damage           []renderer.Damage
 	damageGeneration uint64
+	damageSaturated  bool
 	escapeBuf        []byte
 	csiScratch       []int
 	sgrScratch       []int
 // Damage returns the current damage list. The caller must not modify the
 // returned slice; ClearDamage must be called after the damage is consumed.
 func (s *Screen) Damage() []renderer.Damage { return s.damage }
-func (s *Screen) ClearDamage()              { s.damage = s.damage[:0] }
+func (s *Screen) ClearDamage() {
+	s.damage = s.damage[:0]
+	s.damageSaturated = false
+}
 // CaptureDamage snapshots pending damage without consuming it.
 func (s *Screen) CaptureDamage() DamageCapture {
 func (s *Screen) record(d renderer.Damage) {
 	s.damageGeneration++
+	if s.damageSaturated {
+		return
+	}
+	if len(s.damage) >= maxPendingDamage {
+		s.damage = []renderer.Damage{renderer.FullRedraw()}
+		s.damageSaturated = true
+		return
+	}
 	// Replace FullRedraw with the first concrete damage item.
 	if len(s.damage) == 1 && s.damage[0].Kind == renderer.DamageFullRedraw {
 		s.damage[0] = d

M pkg/vt/screen_test.go +1 -1


@@ -2060,7 +2060,7 @@ func TestDamageSaturationBoundsPendingRecords(t *testing.T) {
2060	2060		s.ClearDamage()
2061	2061
2062	2062		for i := range 1_100 {
2063		-	s.record(renderer.Damage{Kind: renderer.DamageText, X: i % 2, Y: (i / 2) % 2, Width: 1, Height: 1, Count: 1})
	2063	+	s.record(renderer.Damage{Kind: renderer.DamageText, X: 0, Y: i % 2, Width: 1, Height: 1, Count: 1})
2064	2064		}
2065	2065		require.Equal(t, []renderer.Damage{renderer.FullRedraw()}, s.Damage())
2066	2066


@@ -2060,7 +2060,7 @@ func TestDamageSaturationBoundsPendingRecords(t *testing.T) {
2060		s.ClearDamage()	2060		s.ClearDamage()
2061			2061
2062		for i := range 1_100 {	2062		for i := range 1_100 {
2063	-	s.record(renderer.Damage{Kind: renderer.DamageText, X: i % 2, Y: (i / 2) % 2, Width: 1, Height: 1, Count: 1})	2063	+	s.record(renderer.Damage{Kind: renderer.DamageText, X: 0, Y: i % 2, Width: 1, Height: 1, Count: 1})
2064		}	2064		}
2065		require.Equal(t, []renderer.Damage{renderer.FullRedraw()}, s.Damage())	2065		require.Equal(t, []renderer.Damage{renderer.FullRedraw()}, s.Damage())
2066			2066