[newlib-cygwin] Cygwin: console: Add emulation of CSI3J on Win10 1809.

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=c13cdfd00ed09d23e5cf1864033a1bfd54bc3aab

commit c13cdfd00ed09d23e5cf1864033a1bfd54bc3aab
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Thu Feb 27 00:33:02 2020 +0900

    Cygwin: console: Add emulation of CSI3J on Win10 1809.
    
    - This patch add emulation of CSI3J, which is broken in Win10 1809,
      rather than ignoring it as before.

Diff:
---
 winsup/cygwin/fhandler_console.cc | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/fhandler_console.cc b/winsup/cygwin/fhandler_console.cc
index f87d932..4ab9bca 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -2102,8 +2102,23 @@ fhandler_console::char_command (char c)
 	  break;
 	case 'J': /* ED */
 	  wpbuf_put (c);
-	  /* Ignore CSI3J in Win10 1809 because it is broken. */
-	  if (con.args[0] != 3 || !wincap.has_con_broken_csi3j ())
+	  if (con.args[0] == 3 && wincap.has_con_broken_csi3j ())
+	    { /* Workaround for broken CSI3J in Win10 1809 */
+	      CONSOLE_SCREEN_BUFFER_INFO sbi;
+	      GetConsoleScreenBufferInfo (get_output_handle (), &sbi);
+	      SMALL_RECT r = {0, sbi.srWindow.Top,
+		(SHORT) (sbi.dwSize.X - 1), (SHORT) (sbi.dwSize.Y - 1)};
+	      CHAR_INFO f = {' ', sbi.wAttributes};
+	      COORD d = {0, 0};
+	      ScrollConsoleScreenBufferA (get_output_handle (),
+					  &r, NULL, d, &f);
+	      SetConsoleCursorPosition (get_output_handle (), d);
+	      d = sbi.dwCursorPosition;
+	      d.Y -= sbi.srWindow.Top;
+	      SetConsoleCursorPosition (get_output_handle (), d);
+	    }
+	  else
+	    /* Just send the sequence */
 	    WriteConsoleA (get_output_handle (), wpbuf, wpixput, &wn, 0);
 	  break;
 	case 'h': /* DECSET */