From 805e4b31a16d5e986087786cc2b41f41ab804a9e Mon Sep 17 00:00:00 2001
From: David Adam <zanchey@ucc.gu.uwa.edu.au>
Date: Mon, 16 Oct 2017 12:13:30 +0800
Subject: [PATCH] only call ioctl to export new termsize if process is in the
 foreground

Closes #4477.

(cherry picked from commit 216c4b811a5a19157ce9843527ec2f96517c6699)
---
 src/common.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/common.cpp b/src/common.cpp
index 27ca11930..abd2b2b51 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -1592,7 +1592,10 @@ static void export_new_termsize(struct winsize *new_termsize) {
     env_set(L"LINES", buf, ENV_GLOBAL | (lines.missing_or_empty() ? 0 : ENV_EXPORT));
 
 #ifdef HAVE_WINSIZE
-    ioctl(STDOUT_FILENO, TIOCSWINSZ, new_termsize);
+    // Only write the new terminal size if we are in the foreground (#4477)
+    if (tcgetpgrp(STDOUT_FILENO) == getpgrp()) {
+        ioctl(STDOUT_FILENO, TIOCSWINSZ, new_termsize);
+    }
 #endif
 }