From e7544e0a3b64688addb8ea7cdbe67152177c51b5 Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicholas.marriott@gmail.com>
Date: Fri, 19 Jun 2026 11:35:19 +0100
Subject: [PATCH] Add a test for tty_draw_line.

---
 regress/tty-draw-line.sh | 228 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 228 insertions(+)
 create mode 100644 regress/tty-draw-line.sh

diff --git a/regress/tty-draw-line.sh b/regress/tty-draw-line.sh
new file mode 100644
index 00000000..0352c33a
--- /dev/null
+++ b/regress/tty-draw-line.sh
@@ -0,0 +1,228 @@
+#!/bin/sh
+
+# Exercise tty_draw_line through a real client. An inner tmux is attached
+# inside an outer tmux pane; the outer pane is then captured to inspect what
+# the inner client actually drew.
+
+PATH=/bin:/usr/bin
+TERM=screen
+LC_ALL=C.UTF-8
+export TERM LC_ALL
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+
+fail() {
+	echo "$*" >&2
+	exit 1
+}
+
+capture() {
+	$TMUX capturep -pS0 -E- >$TMP || exit 1
+}
+
+capturee() {
+	$TMUX capturep -peS0 -E- >$TMP || exit 1
+}
+
+capturen() {
+	$TMUX capturep -pNS0 -E- >$TMP || exit 1
+}
+
+captureen() {
+	$TMUX capturep -peNS0 -E- >$TMP || exit 1
+}
+
+check_line() {
+	line=$1
+	want=$2
+	got=$(sed -n "$line"p $TMP)
+	[ "$got" = "$want" ] || fail "line $line: expected '$want', got '$got'"
+}
+
+check_grep() {
+	pattern=$1
+	grep -q "$pattern" $TMP || fail "missing pattern: $pattern"
+}
+
+$TMUX kill-server 2>/dev/null
+$TMUX2 kill-server 2>/dev/null
+
+TMP=$(mktemp)
+trap "rm -f $TMP; $TMUX kill-server 2>/dev/null; $TMUX2 kill-server 2>/dev/null" 0 1 15
+
+$TMUX2 -f/dev/null new -d -x20 -y6 -s test \
+	"printf 'abcdefghijklmnopqrst'; exec sleep 100" || exit 1
+$TMUX2 set -g status off || exit 1
+$TMUX2 set -g mode-style "fg=white,bg=red" || exit 1
+$TMUX2 setw -g mode-keys vi || exit 1
+$TMUX2 neww -d \
+	"printf '\033[31;44;1mRED\033[0m\tTAIL\nu:e\314\201:\347\225\214:\360\237\207\272\360\237\207\270:Z\nAAA      BBB'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf '12345678\347\225\214Z'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf 'wrap-ABCDEFGHIJKLMNOZ'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf 'AA    BB'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf 'XYZ'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf '\347\225\214\347\225\214\347\225\214\347\225\214\347\225\214'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf '123456789Z'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf 'abcdef\347\225\214GHIJKLMNOPQRSTUVWXYZ'; printf '\033[H'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf 'abcdefghijklmnopqrst\r\033[KXYZ\nnext'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf 'ab\tcdefghijklmnopqrstuvwxyz'; printf '\033[H'; exec sleep 100" || exit 1
+$TMUX2 selectw -t:0 || exit 1
+
+$TMUX -f/dev/null new -d -x20 -y6 || exit 1
+$TMUX set -g status off || exit 1
+$TMUX send -l "$TMUX2 attach" || exit 1
+$TMUX send Enter || exit 1
+sleep 1
+CLIENT=$($TMUX2 list-clients -F '#{client_name}' | head -1)
+[ -n "$CLIENT" ] || fail "no inner client"
+
+# Long line, then short line: default cells after cellsize must clear stale text.
+capture
+check_line 1 "abcdefghijklmnopqrst"
+$TMUX2 selectw -t:5 || exit 1
+sleep 1
+capture
+check_line 1 "XYZ"
+grep -q '^XYZdefghijklmnopqrst$' $TMP && fail "short redraw left stale tail"
+
+# Styles, tabs, same runs, Unicode combining/wide/flag cells.
+$TMUX2 selectw -t:1 || exit 1
+sleep 1
+capture
+check_grep '^RED[	 ]*TAIL$'
+check_grep '^u:e.*:.*:.*:Z$'
+check_line 3 "AAA      BBB"
+capturee
+esc=$(printf '\033')
+grep -q "$esc" $TMP || fail "styled redraw did not preserve attributes"
+
+# Wide character clipping and padding after resize.
+$TMUX2 selectw -t:2 || exit 1
+$TMUX resizew -x10 -y6 || exit 1
+sleep 1
+$TMUX2 respawnp -k "printf '12345678\347\225\214Z'; exec sleep 100" || exit 1
+sleep 1
+capture
+check_line 1 "12345678界"
+$TMUX resizew -x9 -y6 || exit 1
+sleep 1
+capture
+check_line 1 "12345678"
+grep -q '^12345678Z$' $TMP && fail "wide clipping left stale cell"
+
+# Repeated wide characters at the right edge should not leave orphan padding.
+$TMUX resizew -x9 -y6 || exit 1
+$TMUX2 selectw -t:6 || exit 1
+sleep 1
+$TMUX2 respawnp -k "printf '\347\225\214\347\225\214\347\225\214\347\225\214\347\225\214'; exec sleep 100" || exit 1
+sleep 1
+capture
+check_line 1 "界界界界"
+
+# Tabs should clear stale cells as an empty run.
+$TMUX resizew -x10 -y6 || exit 1
+$TMUX2 selectw -t:7 || exit 1
+sleep 1
+capture
+check_line 1 "123456789Z"
+$TMUX2 respawnp -k "printf '123456789\t'; exec sleep 100" || exit 1
+sleep 1
+capture
+check_line 1 "123456789"
+grep -q '^123456789.*Z$' $TMP && fail "tab clipping left stale cell"
+
+# Tabs clipped at both ends, at the right, and at the left. This is like
+# drawing spans over the middle of a tab when an overlay or viewport clips the
+# pane line.
+$TMUX resizew -x4 -y6 || exit 1
+$TMUX2 selectw -t:10 || exit 1
+$TMUX2 resizew -t:10 -x26 -y6 || exit 1
+$TMUX2 respawnp -k "printf 'ab\tcdefghijklmnopqrstuvwxyz'; printf '\033[H'; exec sleep 100" || exit 1
+$TMUX2 refresh -t"$CLIENT" -c || exit 1
+sleep 1
+capturen
+check_line 1 "ab  "
+$TMUX2 refresh -t"$CLIENT" -R 2 || exit 1
+sleep 1
+capturen
+check_line 1 "    "
+$TMUX2 refresh -t"$CLIENT" -R 4 || exit 1
+sleep 1
+capturen
+check_line 1 "  cd"
+$TMUX2 refresh -t"$CLIENT" -R 2 || exit 1
+sleep 1
+capturen
+check_line 1 "cdef"
+$TMUX2 refresh -t"$CLIENT" -L 8 || exit 1
+
+# Horizontal clipping that starts in or near a wide character should not draw
+# partial padding or stale cells.
+$TMUX resizew -x20 -y6 || exit 1
+$TMUX2 selectw -t:8 || exit 1
+$TMUX2 resizew -t:8 -x26 -y6 || exit 1
+$TMUX2 respawnp -k "printf 'abcdef\347\225\214GHIJKLMNOPQRSTUVWXYZ'; printf '\033[H'; exec sleep 100" || exit 1
+$TMUX2 refresh -t"$CLIENT" -c || exit 1
+sleep 1
+$TMUX2 refresh -t"$CLIENT" -R 4 || exit 1
+sleep 1
+capture
+check_line 1 "ef界GHIJKLMNOPQRSTUV"
+$TMUX2 refresh -t"$CLIENT" -R 1 || exit 1
+sleep 1
+capture
+check_line 1 "f界GHIJKLMNOPQRSTUVW"
+$TMUX2 refresh -t"$CLIENT" -L 5 || exit 1
+
+# Wrapped line redraw.
+$TMUX resizew -x20 -y6 || exit 1
+$TMUX2 selectw -t:3 || exit 1
+sleep 1
+capture
+check_line 1 "wrap-ABCDEFGHIJKLMNO"
+check_line 2 "Z"
+
+# Selection over spaces should still paint attributes for otherwise empty cells.
+$TMUX2 selectw -t:4 || exit 1
+sleep 1
+$TMUX2 copy-mode -H || exit 1
+$TMUX2 send -X start-of-line || exit 1
+$TMUX2 send -X -N 2 cursor-right || exit 1
+$TMUX2 send -X begin-selection || exit 1
+$TMUX2 send -X -N 3 cursor-right || exit 1
+sleep 1
+capture
+check_line 1 "AA    BB"
+capturee
+sed -n 1p $TMP | grep -q "$esc" || fail "selected spaces did not draw attributes"
+
+# Selection on a short line should still draw attributes correctly. This line
+# was previously expanded, then cleared and rewritten shorter, so cellsize
+# remains larger than the visible text.
+$TMUX2 selectw -t:9 || exit 1
+sleep 1
+$TMUX2 copy-mode -H || exit 1
+$TMUX2 send -X history-top || exit 1
+$TMUX2 send -X start-of-line || exit 1
+$TMUX2 send -X begin-selection || exit 1
+$TMUX2 send -X cursor-down || exit 1
+sleep 1
+capture
+check_line 1 "XYZ"
+check_line 2 "next"
+captureen
+sed -n 1p $TMP | grep -q "$esc" || \
+	fail "selected short-line tail did not draw attributes"
+
+exit 0