a54a8105

fix: a blank row paints nothing, and a trailing default space is not a divergence

a73x 2026-09-04 18:04

Commit message

fix: a blank row paints nothing, and a trailing default space is not a divergence

Two consequences of the cell wire that the e2e convergence check found.

The serializer stopped a row at column 0 when every cell was blank, which
printed a space into every empty row and left a screen that could never look
empty again. It now writes nothing at all for a row with nothing on it.

The styled convergence leg normalizes trailing default spaces on both sides,
as the plain leg already did. The row encoder stops a row at its last cell
that is not a default blank, so a space the shell wrote at the end of a row
never leaves the daemon: the client's grid holds an erased cell where the
daemon's holds a space, and the two paint identically. A trailing space
carrying a colour is sent, arrives wrapped in SGR bytes, and is untouched.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CsWfuJFQbTfGtKZLS5qw4q

src/tui/paint.zig

Old		New
@@ -49,15 +49,22 @@ pub fn rowToVtFrom(
49	if (s.from > last) break :blk null;	49	if (s.from > last) break :blk null;
50	break :blk grid.snapWideOf(r, cols, s.from, @min(s.to, last));	50	break :blk grid.snapWideOf(r, cols, s.from, @min(s.to, last));
51	} else null;	51	} else null;
52	var end: u16 = last;	52	// The last cell worth writing: trailing default blanks are the caller's
53	// Trailing default blanks are the caller's clear, not ours — but a	53	// clear, not ours — but a selected blank is a cell the user can see they
54	// selected blank is a cell the user can see they selected, so the span	54	// selected, so the span holds the stop open past it. A row with nothing
55	// holds the stop open past it.	55	// on it writes nothing at all, or an empty row would print a space and a
56	while (end > 0 and r.cells[end].isBlank() and (snapped == null or end > snapped.?.to)) end -= 1;	56	// screen would never look empty again.
		57	var end: ?u16 = null;
		58	var i: u16 = 0;
		59	while (i <= last) : (i += 1) {
		60	const selected = if (snapped) \|s\| i >= s.from and i <= s.to else false;
		61	if (!r.cells[i].isBlank() or selected) end = i;
		62	}
		63	const stop = end orelse return out.toOwnedSlice(alloc);
57	var cur: proto.CellStyle = .{};	64	var cur: proto.CellStyle = .{};
58	var x: u16 = 0;	65	var x: u16 = 0;
59	var inverted = false;	66	var inverted = false;
60	while (x <= end) : (x += 1) {	67	while (x <= stop) : (x += 1) {
61	const c = r.cells[x];	68	const c = r.cells[x];
62	if (c.wide == .spacer_tail or c.wide == .spacer_head) continue;	69	if (c.wide == .spacer_tail or c.wide == .spacer_head) continue;
63	const in_span = if (snapped) \|s\| x >= s.from and x <= s.to else false;	70	const in_span = if (snapped) \|s\| x >= s.from and x <= s.to else false;

test/e2e_01_boot.sh

Old		New
@@ -98,7 +98,8 @@ if converged_quiet "$OUT.doctored" "$SOCK"; then
98	fi	98	fi
99	rm_swept "$OUT.doctored" "$OUT.doctored.render" "$OUT.doctored.dump" \	99	rm_swept "$OUT.doctored" "$OUT.doctored.render" "$OUT.doctored.dump" \
100	"$OUT.doctored.render.n" "$OUT.doctored.dump.n" "$OUT.doctored.diff" \	100	"$OUT.doctored.render.n" "$OUT.doctored.dump.n" "$OUT.doctored.diff" \
101	"$OUT.doctored.rvt" "$OUT.doctored.dvt"	101	"$OUT.doctored.rvt" "$OUT.doctored.dvt" \
		102	"$OUT.doctored.rvt.n" "$OUT.doctored.dvt.n"
102	ok "convergence control fires on a doctored stream"	103	ok "convergence control fires on a doctored stream"
103		104
104	# --- M11: a styled specimen, so the byte-exact leg has something to compare.	105	# --- M11: a styled specimen, so the byte-exact leg has something to compare.

test/e2e_lib.sh

Old		New
@@ -1041,9 +1041,20 @@ converged_quiet() {
1041	# shellcheck disable=SC2086	1041	# shellcheck disable=SC2086
1042	"$RENDER" --vt $_sz $_drop < "$_co" > "$_co.rvt" \|\| return 1	1042	"$RENDER" --vt $_sz $_drop < "$_co" > "$_co.rvt" \|\| return 1
1043	"$MUX" d dump --vt --sock "$_cs" > "$_co.dvt" \|\| return 1	1043	"$MUX" d dump --vt --sock "$_cs" > "$_co.dvt" \|\| return 1
1044	cmp -s "$_co.dvt" "$_co.rvt" \|\| return 1	1044	# Trailing DEFAULT spaces are normalized away on both sides for the same
		1045	# reason the plain leg strips them: the row encoder stops a row at its
		1046	# last cell that is not a default blank, so a space the shell wrote at
		1047	# the end of a row never leaves the daemon and the client's grid holds an
		1048	# erased cell where the daemon's holds a space. The two paint identically.
		1049	# A trailing space carrying a colour is NOT a default blank — it is sent,
		1050	# and it arrives wrapped in SGR bytes, so the line does not end in
		1051	# whitespace and this leaves it alone.
		1052	_cr=$(printf '\r')
		1053	sed "s/ *\$${_cr}\\{0,1\\}\$\$/\\1/" "$_co.dvt" > "$_co.dvt.n"
		1054	sed "s/ *\$${_cr}\\{0,1\\}\$\$/\\1/" "$_co.rvt" > "$_co.rvt.n"
		1055	cmp -s "$_co.dvt.n" "$_co.rvt.n" \|\| return 1
1045	rm -f "$_co.render" "$_co.dump" "$_co.render.n" "$_co.dump.n" \	1056	rm -f "$_co.render" "$_co.dump" "$_co.render.n" "$_co.dump.n" \
1046	"$_co.diff" "$_co.rvt" "$_co.dvt"	1057	"$_co.diff" "$_co.rvt" "$_co.dvt" "$_co.rvt.n" "$_co.dvt.n"
1047	return 0	1058	return 0
1048	}	1059	}
1049		1060