[newlib-cygwin] Cygwin: console: Add a workaround for "ESC 7" and "ESC 8".

[Corinna Vinschen <corinna at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=b4bc238311ca66ce34de5bec2f8219e881cedfd0

commit b4bc238311ca66ce34de5bec2f8219e881cedfd0
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Mon Mar 2 10:12:57 2020 +0900

    Cygwin: console: Add a workaround for "ESC 7" and "ESC 8".
    
    - In xterm compatible mode, "ESC 7" and "ESC 8" do not work properly
      in the senario:
       1) Execute /bin/ls /bin to fill screen.
       2) Sned CSI?1049h to alternate screen.
       3) Reduce window size.
       4) Send CSI?1049l to resume screen.
       5) Send "ESC 7" and "ESC 8".
      After sending "ESC 8", the cursor goes to incorrect position. This
      patch adds a workaround for this issue.

Diff:
---
 winsup/cygwin/fhandler.h          |  1 +
 winsup/cygwin/fhandler_console.cc | 53 +++++++++++++++++++++++++++++----------
 2 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index adaf192..463bb83 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1869,6 +1869,7 @@ class dev_console
   bool alternate_charset_active;
   bool metabit;
   char backspace_keycode;
+  bool screen_alternated; /* For xterm compatible mode only */
 
   char my_title_buf [TITLESIZE + 1];
 
diff --git a/winsup/cygwin/fhandler_console.cc b/winsup/cygwin/fhandler_console.cc
index 8b46877..dffee24 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -207,6 +207,8 @@ fhandler_console::setup ()
       con.dwLastCursorPosition.Y = -1;
       con.dwLastMousePosition.X = -1;
       con.dwLastMousePosition.Y = -1;
+      con.savex = con.savey = -1;
+      con.screen_alternated = false;
       con.dwLastButtonState = 0;	/* none pressed */
       con.last_button_code = 3;	/* released */
       con.underline_color = FOREGROUND_GREEN | FOREGROUND_BLUE;
@@ -2130,6 +2132,10 @@ fhandler_console::char_command (char c)
 	  break;
 	case 'h': /* DECSET */
 	case 'l': /* DECRST */
+	  if (c == 'h')
+	    con.screen_alternated = true;
+	  else
+	    con.screen_alternated = false;
 	  wpbuf_put (c);
 	  /* Just send the sequence */
 	  WriteConsoleA (get_output_handle (), wpbuf, wpixput, &wn, 0);
@@ -2989,6 +2995,36 @@ fhandler_console::write (const void *vsrc, size_t len)
 	      con.saw_space = false;
 	      con.saw_exclamation_mark = false;
 	    }
+	  else if (*src == '8')		/* DECRC Restore cursor position */
+	    {
+	      if (con.screen_alternated)
+		{
+		  /* For xterm mode only */
+		  DWORD n;
+		  /* Just send the sequence */
+		  wpbuf_put (*src);
+		  WriteConsoleA (get_output_handle (), wpbuf, wpixput, &n, 0);
+		}
+	      else if (con.savex >= 0 && con.savey >= 0)
+		cursor_set (false, con.savex, con.savey);
+	      con.state = normal;
+	      wpixput = 0;
+	    }
+	  else if (*src == '7')		/* DECSC Save cursor position */
+	    {
+	      if (con.screen_alternated)
+		{
+		  /* For xterm mode only */
+		  DWORD n;
+		  /* Just send the sequence */
+		  wpbuf_put (*src);
+		  WriteConsoleA (get_output_handle (), wpbuf, wpixput, &n, 0);
+		}
+	      else
+		cursor_get (&con.savex, &con.savey);
+	      con.state = normal;
+	      wpixput = 0;
+	    }
 	  else if (wincap.has_con_24bit_colors () && !con_is_legacy
 		   && wincap.has_con_broken_il_dl () && *src == 'M')
 	    { /* Reverse Index (scroll down) */
@@ -3019,12 +3055,15 @@ fhandler_console::write (const void *vsrc, size_t len)
 	      wpixput = 0;
 	    }
 	  else if (wincap.has_con_24bit_colors () && !con_is_legacy)
-	    { /* Only CSI is handled in xterm compatible mode. */
+	    {
 	      if (*src == 'c') /* RIS Full reset */
 		{
 		  con.scroll_region.Top = 0;
 		  con.scroll_region.Bottom = -1;
 		}
+	      /* ESC sequences below (e.g. OSC, etc) are left to xterm
+		 emulation in xterm compatible mode, therefore, are not
+		 handled and just sent them. */
 	      wpbuf_put (*src);
 	      /* Just send the sequence */
 	      DWORD n;
@@ -3067,18 +3106,6 @@ fhandler_console::write (const void *vsrc, size_t len)
 	      con.state = normal;
 	      wpixput = 0;
 	    }
-	  else if (*src == '8')		/* DECRC Restore cursor position */
-	    {
-	      cursor_set (false, con.savex, con.savey);
-	      con.state = normal;
-	      wpixput = 0;
-	    }
-	  else if (*src == '7')		/* DECSC Save cursor position */
-	    {
-	      cursor_get (&con.savex, &con.savey);
-	      con.state = normal;
-	      wpixput = 0;
-	    }
 	  else if (*src == 'R')		/* ? */
 	    {
 	      con.state = normal;