perf(ansi): compare whole retained rows before scroll applicability checks

canApplyDenseScrollAgainst walked every retained cell through Frame.At. For
full-width scrolls it now first compares the committed row (y+offset) with
the target row via core.RowsEqualAt and only falls back to the per-cell damage
coverage check for rows that differ.

commit: 1bbdfc6d77a80ff4974f8c71d6b9853c1544294e
author: brice · 20d ago · 2026-10-02 09:47 UTC
parent: 748182f
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

1 file · +7 -0

M ansi/scroll.go +7 -0


@@ -3,6 +3,8 @@ package ansi
3	3		import (
4	4		"bytes"
5	5		"strconv"
	6	+
	7	+	"github.com/bnema/vev-vt/core"
6	8		)
7	9
8	10		func findSafeScroll(frame CellSource, damage []Damage) (Damage, bool) {

@@ -92,6 +94,11 @@ func canApplyScrollAgainst(frame CellSource, scroll Damage, damage []Damage, com
92	94		func canApplyDenseScrollAgainst(frame Frame, scroll Damage, damage []Damage, committed Frame) bool {
93	95		start, end, offset := scrollRetainedRows(scroll)
94	96		for y := start; y < end; y++ {
	97	+	// Scrolls are full width, so a retained row that matches whole needs no
	98	+	// per-cell damage lookups.
	99	+	if scroll.X == 0 && scroll.Width == frame.Width && core.RowsEqualAt(committed, y+offset, frame, y) {
	100	+	continue
	101	+	}
95	102		for x := range scroll.Width {
96	103		column := scroll.X + x
97	104		committedCell, frameCell := committed.At(column, y+offset), frame.At(column, y)


@@ -3,6 +3,8 @@ package ansi
3	import (	3		import (
4	"bytes"	4		"bytes"
5	"strconv"	5		"strconv"
		6	+
		7	+	"github.com/bnema/vev-vt/core"
6	)	8		)
7		9
8	func findSafeScroll(frame CellSource, damage []Damage) (Damage, bool) {	10		func findSafeScroll(frame CellSource, damage []Damage) (Damage, bool) {

@@ -92,6 +94,11 @@ func canApplyScrollAgainst(frame CellSource, scroll Damage, damage []Damage, com
92	func canApplyDenseScrollAgainst(frame Frame, scroll Damage, damage []Damage, committed Frame) bool {	94		func canApplyDenseScrollAgainst(frame Frame, scroll Damage, damage []Damage, committed Frame) bool {
93	start, end, offset := scrollRetainedRows(scroll)	95		start, end, offset := scrollRetainedRows(scroll)
94	for y := start; y < end; y++ {	96		for y := start; y < end; y++ {
		97	+	// Scrolls are full width, so a retained row that matches whole needs no
		98	+	// per-cell damage lookups.
		99	+	if scroll.X == 0 && scroll.Width == frame.Width && core.RowsEqualAt(committed, y+offset, frame, y) {
		100	+	continue
		101	+	}
95	for x := range scroll.Width {	102		for x := range scroll.Width {
96	column := scroll.X + x	103		column := scroll.X + x
97	committedCell, frameCell := committed.At(column, y+offset), frame.At(column, y)	104		committedCell, frameCell := committed.At(column, y+offset), frame.At(column, y)