[PATCH] Cygwin: pty: Fix a bug regarding ESC[?3h and ESC[?3l handling.

[Takashi Yano]

- Midnight commander (mc) does not work after the commit
  1626569222066ee601f6c41b29efcc95202674b7 as reported in
  https://www.cygwin.com/ml/cygwin/2019-12/msg00173.html.
  This patch fixes the issue.
---
 winsup/cygwin/fhandler_tty.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index 1d344c7fe..8c3a6e72e 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -1262,16 +1262,19 @@ fhandler_pty_slave::push_to_pcon_screenbuffer (const char *ptr, size_t len)
   while ((p0 = (char *) memmem (p0, nlen - (p0 - buf), "\033[?", 3)))
     {
       p0 += 3;
-      while (p0 < buf + nlen && *p0 != 'h' && *p0 != 'l')
+      bool exist_arg_3 = false;
+      while (p0 < buf + nlen && !isalpha (*p0))
 	{
 	  int arg = 0;
 	  while (p0 < buf + nlen && isdigit (*p0))
 	    arg = arg * 10 + (*p0 ++) - '0';
 	  if (arg == 3)
-	    get_ttyp ()->need_redraw_screen = true;
+	    exist_arg_3 = true;
 	  if (p0 < buf + nlen && *p0 == ';')
 	    p0 ++;
 	}
+      if (p0 < buf + nlen && exist_arg_3 && (*p0 == 'h' || *p0 == 'l'))
+	get_ttyp ()->need_redraw_screen = true;
       p0 ++;
       if (p0 >= buf + nlen)
 	break;
-- 
2.21.0