Add multiline-scroll regression test

src/tests/Makefile.am

@@ -10,6 +10,7 @@ displaytests = \
 	e2e-success.test \
 	e2e-failure.test \
 	emulation-back-tab.test \
+	emulation-multiline-scroll.test \
 	unicode-combine-fallback-assert.test \
 	unicode-later-combining.test
 

src/tests/emulation-multiline-scroll.test

@@ -0,0 +1,83 @@
+#!/bin/sh
+
+#
+# This is a regression test for a crash seen in my development
+# of performance code for Mosh, involving insert/delete line.
+# It does insert/delete line from 0 to 2 more than the window height
+# 24 in this test environment).
+fail()
+{
+    printf "$@" 2>&1
+    exit 99
+}
+
+
+
+PATH=$PATH:.:$srcdir
+# Top-level wrapper.
+if [ $# -eq 0 ]; then
+    e2e-test $0 baseline
+    exit
+fi
+
+# OK, we have arguments, we're one of the test hooks.
+if [ $# -ne 1 ]; then
+    fail "bad arguments %s\n" "$@"
+fi
+
+sleepf()
+{
+    (sleep .1 || sleep 1) > /dev/null 2>&1
+}
+
+seq()
+{
+    if [ $# -lt 1 -o $# -gt 3 ]; then
+	echo "bad args" >&2
+    fi
+    first=$1
+    incr=1
+    last=0
+    case $# in
+	3)
+	    incr=$2
+	    last=$3
+	    ;;
+	2)
+	    last=$2
+	    ;;
+	1)
+	    ;;
+    esac
+    while :; do
+	printf '%d\n' $first
+	first=$(expr $first + $incr)
+	if [ $first -gt $last ]; then
+	    break
+	fi
+    done
+}
+
+baseline()
+{
+    printf '\033[H\033[J'
+    for dir in L M; do
+	for i in $(seq 0 2) $(seq 22 26); do
+	    printf '%d\r' $i
+	    printf '\033[%d%s' $i $dir
+	    # On the one hand, we'd like to test that this works
+	    # properly on both client and server, which requires
+	    # delays so that each iteration percolates to the client
+	    # by itself.  On the other hand, that makes the test take
+	    # a long time.  Compromise on .1 second.
+	    (sleep .1 || sleep 1) > /dev/null 2>&1
+	done
+    done
+}
+
+case $1 in
+    baseline)
+	baseline;;
+    *)
+	fail "unknown test argument %s\n" $1;;
+esac