From 1626569222066ee601f6c41b29efcc95202674b7 Mon Sep 17 00:00:00 2001
From: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Wed, 13 Nov 2019 19:49:29 +0900
Subject: [PATCH] Cygwin: pty: Trigger redraw screen if ESC[?3h or ESC[?3l is
 sent.

- Pseudo console clears console screen buffer if ESC[?3h or ESC[?3l
  is sent. However, xterm/vt100 does not clear screen. This cause
  mismatch between real screen and console screen buffer. Therefore,
  this patch triggers redraw screen in that situation so that the
  synchronization is done on the next execution of native app.
  This solves the problem reported in:
  https://www.cygwin.com/ml/cygwin-patches/2019-q4/msg00116.html
---
 winsup/cygwin/fhandler_tty.cc | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index e02a8f43b..f9c7c3ade 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -1255,6 +1255,28 @@ fhandler_pty_slave::push_to_pcon_screenbuffer (const char *ptr, size_t len)
       memmove (p0, p0+4, nlen - (p0+4 - buf));
       nlen -= 4;
     }
+
+  /* If the ESC sequence ESC[?3h or ESC[?3l which clears console screen
+     buffer is pushed, set need_redraw_screen to trigger redraw screen. */
+  p0 = buf;
+  while ((p0 = (char *) memmem (p0, nlen - (p0 - buf), "\033[?", 3)))
+    {
+      p0 += 3;
+      while (p0 < buf + nlen && *p0 != 'h' && *p0 != 'l')
+	{
+	  int arg = 0;
+	  while (p0 < buf + nlen && isdigit (*p0))
+	    arg = arg * 10 + (*p0 ++) - '0';
+	  if (arg == 3)
+	    get_ttyp ()->need_redraw_screen = true;
+	  if (p0 < buf + nlen && *p0 == ';')
+	    p0 ++;
+	}
+      p0 ++;
+      if (p0 >= buf + nlen)
+	break;
+    }
+
   DWORD dwMode, flags;
   flags = ENABLE_VIRTUAL_TERMINAL_PROCESSING;
   GetConsoleMode (get_output_handle (), &dwMode);