fix(term): disable autowrap while vev owns the alt screen

A frame the daemon composed for a wider terminal than the one currently
attached bleeds onto the next row: the tab bar is a full-width styled run,
so with DECAWM on it wraps and paints a second row in the accent colour.
The result reads as a multi-line text selection flashing at startup, when
the terminal is created at its configured initial size and the compositor
resizes it a few milliseconds later.

vev addresses every row explicitly and never relies on the terminal
wrapping its output — emitSpan invalidates the tracked cursor as soon as a
span reaches the right edge, so the next write always re-issues an
absolute move. Turning DECAWM off therefore only changes what happens to
an over-long row: it is clipped at the right margin instead of wrapping.

DECAWM is global and is not saved by the alt-screen switch, so it is
restored alongside the other modes, before the alt-screen exit.

Verified against pyte (which implements DECAWM, unlike pkg/vt) by
replaying a captured 204-column frame into an 80-column screen: 2 rows
carry a non-default background with autowrap on, 1 with it off.

commit: fd7fd716c488fccd4875c28625549c48610cbf71
author: brice · 2mo ago · 2026-07-25 13:58 UTC
parent: 33be6b4
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

3 files · +88 -5

M internal/adapters/term/pty_integration_test.go +1 -1


@@ -89,7 +89,7 @@ func TestTerminal_RealPTY_RawModeSizeAndEscapes(t *testing.T) {
89	89
90	90		select {
91	91		case got := <-captured:
92		-	want := altScreenEnter + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + altScreenExit
	92	+	want := altScreenEnter + autowrapDisable + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + autowrapEnable + altScreenExit
93	93		if string(got) != want {
94	94		t.Fatalf("captured escapes = %q, want %q", got, want)
95	95		}


@@ -89,7 +89,7 @@ func TestTerminal_RealPTY_RawModeSizeAndEscapes(t *testing.T) {
89			89
90		select {	90		select {
91		case got := <-captured:	91		case got := <-captured:
92	-	want := altScreenEnter + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + altScreenExit	92	+	want := altScreenEnter + autowrapDisable + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + autowrapEnable + altScreenExit
93		if string(got) != want {	93		if string(got) != want {
94		t.Fatalf("captured escapes = %q, want %q", got, want)	94		t.Fatalf("captured escapes = %q, want %q", got, want)
95		}	95		}

M internal/adapters/term/terminal.go +10 -2


@@ -31,6 +31,14 @@ const (
31	31		bracketedPasteDisable = "\x1b[?2004l"
32	32		colorSchemeEnable = "\x1b[?2031h"
33	33		colorSchemeDisable = "\x1b[?2031l"
	34	+	// DECAWM. vev addresses every row explicitly and never relies on the
	35	+	// terminal wrapping its output, so autowrap stays off while it owns the
	36	+	// alt screen: a frame the daemon composed for a wider terminal is then
	37	+	// clipped at the right margin instead of bleeding a styled run onto the
	38	+	// next row. Restored alongside the other modes, since DECAWM is global
	39	+	// and is not saved by the alt-screen switch.
	40	+	autowrapDisable = "\x1b[?7l"
	41	+	autowrapEnable = "\x1b[?7h"
34	42		)
35	43
36	44		// bufSize is the batched writer's buffer capacity.

@@ -107,7 +115,7 @@ func (t *Terminal) EnterRaw() (func() error, error) {
107	115		}
108	116		t.orig = old
109	117
110		-	if _, err := t.bw.WriteString(altScreenEnter + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable); err != nil {
	118	+	if _, err := t.bw.WriteString(altScreenEnter + autowrapDisable + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable); err != nil {
111	119		_ = t.restoreRawLocked()
112	120		return nil, fmt.Errorf("term: enter alt screen: %w", err)
113	121		}

@@ -141,7 +149,7 @@ func (t *Terminal) restore() error {
141	149		t.mu.Lock()
142	150		defer t.mu.Unlock()
143	151
144		-	_, werr := t.bw.WriteString(cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + altScreenExit)
	152	+	_, werr := t.bw.WriteString(cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + autowrapEnable + altScreenExit)
145	153		ferr := t.bw.Flush()
146	154
147	155		rerr := t.restoreRawLocked()

 	bracketedPasteDisable = "\x1b[?2004l"
 	colorSchemeEnable     = "\x1b[?2031h"
 	colorSchemeDisable    = "\x1b[?2031l"
+	// DECAWM. vev addresses every row explicitly and never relies on the
+	// terminal wrapping its output, so autowrap stays off while it owns the
+	// alt screen: a frame the daemon composed for a wider terminal is then
+	// clipped at the right margin instead of bleeding a styled run onto the
+	// next row. Restored alongside the other modes, since DECAWM is global
+	// and is not saved by the alt-screen switch.
+	autowrapDisable = "\x1b[?7l"
+	autowrapEnable  = "\x1b[?7h"
 )
 // bufSize is the batched writer's buffer capacity.
 	}
 	t.orig = old
-	if _, err := t.bw.WriteString(altScreenEnter + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable); err != nil {
+	if _, err := t.bw.WriteString(altScreenEnter + autowrapDisable + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable); err != nil {
 		_ = t.restoreRawLocked()
 		return nil, fmt.Errorf("term: enter alt screen: %w", err)
 	}
 	t.mu.Lock()
 	defer t.mu.Unlock()
-	_, werr := t.bw.WriteString(cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + altScreenExit)
+	_, werr := t.bw.WriteString(cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + autowrapEnable + altScreenExit)
 	ferr := t.bw.Flush()
 	rerr := t.restoreRawLocked()

M internal/adapters/term/terminal_test.go +77 -2


@@ -4,6 +4,7 @@ import (
4	4		"bytes"
5	5		"io"
6	6		"os"
	7	+	"strings"
7	8		"testing"
8	9		"time"
9	10

@@ -60,7 +61,7 @@ func TestTerminal_EnterRaw_NonTTY_EmitsAltScreenAndCursorEscapes(t *testing.T) {
60	61		_ = outW.Close()
61	62		<-done
62	63
63		-	want := altScreenEnter + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + altScreenExit
	64	+	want := altScreenEnter + autowrapDisable + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + autowrapEnable + altScreenExit
64	65		if got := captured.String(); got != want {
65	66		t.Fatalf("captured escapes = %q, want %q", got, want)
66	67		}

@@ -69,6 +70,80 @@ func TestTerminal_EnterRaw_NonTTY_EmitsAltScreenAndCursorEscapes(t *testing.T) {
69	70		}
70	71		}
71	72
	73	+	// A frame the daemon composed for a wider terminal must never bleed onto the
	74	+	// next row: with DECAWM left on, an over-long styled run (the full-width tab
	75	+	// bar) wraps and paints a second row in the accent colour. vev positions every
	76	+	// row explicitly and never relies on the terminal wrapping for it, so autowrap
	77	+	// stays off for as long as vev owns the alt screen.
	78	+	func TestTerminal_EnterRaw_DisablesAutowrapInsideAltScreen(t *testing.T) {
	79	+	const (
	80	+	autowrapOff = "\x1b[?7l"
	81	+	autowrapOn = "\x1b[?7h"
	82	+	altEnter = "\x1b[?1049h"
	83	+	altExit = "\x1b[?1049l"
	84	+	)
	85	+
	86	+	inR, inW, err := os.Pipe()
	87	+	if err != nil {
	88	+	t.Fatalf("os.Pipe(in): %v", err)
	89	+	}
	90	+	defer func() { _ = inW.Close() }()
	91	+	defer func() { _ = inR.Close() }()
	92	+
	93	+	outR, outW, captured, done := pipeCapture(t)
	94	+	defer func() { _ = outR.Close() }()
	95	+
	96	+	tm := NewWithFiles(inR, outW)
	97	+
	98	+	restore, err := tm.EnterRaw()
	99	+	if err != nil {
	100	+	t.Fatalf("EnterRaw: %v", err)
	101	+	}
	102	+	if err := restore(); err != nil {
	103	+	t.Fatalf("restore: %v", err)
	104	+	}
	105	+
	106	+	_ = outW.Close()
	107	+	<-done
	108	+	got := captured.String()
	109	+
	110	+	for _, tc := range []struct {
	111	+	name string
	112	+	seq string
	113	+	}{
	114	+	{"autowrap disabled exactly once", autowrapOff},
	115	+	{"autowrap restored exactly once", autowrapOn},
	116	+	} {
	117	+	t.Run(tc.name, func(t *testing.T) {
	118	+	if n := strings.Count(got, tc.seq); n != 1 {
	119	+	t.Fatalf("emitted %q %d times, want exactly 1; full output %q", tc.seq, n, got)
	120	+	}
	121	+	})
	122	+	}
	123	+
	124	+	// Ordering: disabling autowrap must land inside the alt screen, and it
	125	+	// must be restored before vev hands the screen back to the shell.
	126	+	for _, tc := range []struct {
	127	+	name string
	128	+	before string
	129	+	after string
	130	+	}{
	131	+	{"alt screen entered before autowrap is disabled", altEnter, autowrapOff},
	132	+	{"autowrap disabled before it is restored", autowrapOff, autowrapOn},
	133	+	{"autowrap restored before leaving the alt screen", autowrapOn, altExit},
	134	+	} {
	135	+	t.Run(tc.name, func(t *testing.T) {
	136	+	i, j := strings.Index(got, tc.before), strings.Index(got, tc.after)
	137	+	if i < 0 \|\| j < 0 {
	138	+	t.Fatalf("missing sequence: %q at %d, %q at %d; full output %q", tc.before, i, tc.after, j, got)
	139	+	}
	140	+	if i >= j {
	141	+	t.Fatalf("%q (index %d) must precede %q (index %d); full output %q", tc.before, i, tc.after, j, got)
	142	+	}
	143	+	})
	144	+	}
	145	+	}
	146	+
72	147		func TestTerminal_EnterRaw_IsIdempotentAcrossCalls(t *testing.T) {
73	148		inR, inW, err := os.Pipe()
74	149		if err != nil {

@@ -103,7 +178,7 @@ func TestTerminal_EnterRaw_IsIdempotentAcrossCalls(t *testing.T) {
103	178
104	179		// Alt-screen/cursor escapes must appear exactly once for enter and exits
105	180		// exactly once, regardless of how many times EnterRaw/restore were called.
106		-	want := altScreenEnter + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + altScreenExit
	181	+	want := altScreenEnter + autowrapDisable + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + autowrapEnable + altScreenExit
107	182		if got := captured.String(); got != want {
108	183		t.Fatalf("captured escapes = %q, want %q", got, want)
109	184		}


@@ -4,6 +4,7 @@ import (
4		"bytes"	4		"bytes"
5		"io"	5		"io"
6		"os"	6		"os"
			7	+	"strings"
7		"testing"	8		"testing"
8		"time"	9		"time"
9			10

@@ -60,7 +61,7 @@ func TestTerminal_EnterRaw_NonTTY_EmitsAltScreenAndCursorEscapes(t *testing.T) {
60		_ = outW.Close()	61		_ = outW.Close()
61		<-done	62		<-done
62			63
63	-	want := altScreenEnter + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + altScreenExit	64	+	want := altScreenEnter + autowrapDisable + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + autowrapEnable + altScreenExit
64		if got := captured.String(); got != want {	65		if got := captured.String(); got != want {
65		t.Fatalf("captured escapes = %q, want %q", got, want)	66		t.Fatalf("captured escapes = %q, want %q", got, want)
66		}	67		}

@@ -69,6 +70,80 @@ func TestTerminal_EnterRaw_NonTTY_EmitsAltScreenAndCursorEscapes(t *testing.T) {
69		}	70		}
70		}	71		}
71			72
			73	+	// A frame the daemon composed for a wider terminal must never bleed onto the
			74	+	// next row: with DECAWM left on, an over-long styled run (the full-width tab
			75	+	// bar) wraps and paints a second row in the accent colour. vev positions every
			76	+	// row explicitly and never relies on the terminal wrapping for it, so autowrap
			77	+	// stays off for as long as vev owns the alt screen.
			78	+	func TestTerminal_EnterRaw_DisablesAutowrapInsideAltScreen(t *testing.T) {
			79	+	const (
			80	+	autowrapOff = "\x1b[?7l"
			81	+	autowrapOn = "\x1b[?7h"
			82	+	altEnter = "\x1b[?1049h"
			83	+	altExit = "\x1b[?1049l"
			84	+	)
			85	+
			86	+	inR, inW, err := os.Pipe()
			87	+	if err != nil {
			88	+	t.Fatalf("os.Pipe(in): %v", err)
			89	+	}
			90	+	defer func() { _ = inW.Close() }()
			91	+	defer func() { _ = inR.Close() }()
			92	+
			93	+	outR, outW, captured, done := pipeCapture(t)
			94	+	defer func() { _ = outR.Close() }()
			95	+
			96	+	tm := NewWithFiles(inR, outW)
			97	+
			98	+	restore, err := tm.EnterRaw()
			99	+	if err != nil {
			100	+	t.Fatalf("EnterRaw: %v", err)
			101	+	}
			102	+	if err := restore(); err != nil {
			103	+	t.Fatalf("restore: %v", err)
			104	+	}
			105	+
			106	+	_ = outW.Close()
			107	+	<-done
			108	+	got := captured.String()
			109	+
			110	+	for _, tc := range []struct {
			111	+	name string
			112	+	seq string
			113	+	}{
			114	+	{"autowrap disabled exactly once", autowrapOff},
			115	+	{"autowrap restored exactly once", autowrapOn},
			116	+	} {
			117	+	t.Run(tc.name, func(t *testing.T) {
			118	+	if n := strings.Count(got, tc.seq); n != 1 {
			119	+	t.Fatalf("emitted %q %d times, want exactly 1; full output %q", tc.seq, n, got)
			120	+	}
			121	+	})
			122	+	}
			123	+
			124	+	// Ordering: disabling autowrap must land inside the alt screen, and it
			125	+	// must be restored before vev hands the screen back to the shell.
			126	+	for _, tc := range []struct {
			127	+	name string
			128	+	before string
			129	+	after string
			130	+	}{
			131	+	{"alt screen entered before autowrap is disabled", altEnter, autowrapOff},
			132	+	{"autowrap disabled before it is restored", autowrapOff, autowrapOn},
			133	+	{"autowrap restored before leaving the alt screen", autowrapOn, altExit},
			134	+	} {
			135	+	t.Run(tc.name, func(t *testing.T) {
			136	+	i, j := strings.Index(got, tc.before), strings.Index(got, tc.after)
			137	+	if i < 0 \|\| j < 0 {
			138	+	t.Fatalf("missing sequence: %q at %d, %q at %d; full output %q", tc.before, i, tc.after, j, got)
			139	+	}
			140	+	if i >= j {
			141	+	t.Fatalf("%q (index %d) must precede %q (index %d); full output %q", tc.before, i, tc.after, j, got)
			142	+	}
			143	+	})
			144	+	}
			145	+	}
			146	+
72		func TestTerminal_EnterRaw_IsIdempotentAcrossCalls(t *testing.T) {	147		func TestTerminal_EnterRaw_IsIdempotentAcrossCalls(t *testing.T) {
73		inR, inW, err := os.Pipe()	148		inR, inW, err := os.Pipe()
74		if err != nil {	149		if err != nil {

@@ -103,7 +178,7 @@ func TestTerminal_EnterRaw_IsIdempotentAcrossCalls(t *testing.T) {
103			178
104		// Alt-screen/cursor escapes must appear exactly once for enter and exits	179		// Alt-screen/cursor escapes must appear exactly once for enter and exits
105		// exactly once, regardless of how many times EnterRaw/restore were called.	180		// exactly once, regardless of how many times EnterRaw/restore were called.
106	-	want := altScreenEnter + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + altScreenExit	181	+	want := altScreenEnter + autowrapDisable + cursorHide + mouseEnable + bracketedPasteEnable + colorSchemeEnable + cursorShow + cursorStyleDefault + mouseDisable + bracketedPasteDisable + colorSchemeDisable + autowrapEnable + altScreenExit
107		if got := captured.String(); got != want {	182		if got := captured.String(); got != want {
108		t.Fatalf("captured escapes = %q, want %q", got, want)	183		t.Fatalf("captured escapes = %q, want %q", got, want)
109		}	184		}