- Cygwin console with xterm compatible mode causes problem reported
  in https://www.cygwin.com/ml/cygwin-patches/2020-q1/msg00212.html
  if background/foreground colors are set to gray/black respectively
  in Win10 1903/1909. This is caused by "CSI Ps L" (IL), "CSI Ps M"
  (DL) and "ESC M" (RI) control sequences which are broken. This
  patch adds a workaround for the issue.
---
 winsup/cygwin/fhandler_console.cc | 156 +++++++++++++++++++++++++++++-
 winsup/cygwin/wincap.cc           |  10 ++
 winsup/cygwin/wincap.h            |   2 +
 3 files changed, 166 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/fhandler_console.cc 
b/winsup/cygwin/fhandler_console.cc
index 328424a7d..c2198ea1e 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -57,6 +57,16 @@ bool NO_COPY fhandler_console::invisible_console;
    Only one console can exist in a process, therefore, static is suitable. */
 static struct fhandler_base::rabuf_t con_ra;
 
+/* Write pending buffer for ESC sequence handling
+   in xterm compatible mode */
+#define WPBUF_LEN 256
+static unsigned char wpbuf[WPBUF_LEN];
+static int wpixput;
+#define wpbuf_put(x) \
+  wpbuf[wpixput++] = x; \
+  if (wpixput > WPBUF_LEN) \
+    wpixput--;
+
 static void
 beep ()
 {
@@ -2014,6 +2024,82 @@ fhandler_console::char_command (char c)
   char buf[40];
   int r, g, b;
 
+  if (wincap.has_con_24bit_colors () && !con_is_legacy)
+    {
+      /* For xterm compatible mode */
+      DWORD wn;
+      switch (c)
+       {
+       case 'r': /* DECSTBM */
+         con.scroll_region.Top = con.args[0] ? con.args[0] - 1 : 0;
+         con.scroll_region.Bottom = con.args[1] ? con.args[1] - 1 : -1;
+         wpbuf_put (c);
+         /* Just send the sequence */
+         WriteConsoleA (get_output_handle (), wpbuf, wpixput, &wn, 0);
+         break;
+       case 'L': /* IL */
+         if (wincap.has_con_broken_il_dl ())
+           {
+             /* Use "CSI Ps T" instead */
+             cursor_get (&x, &y);
+             __small_sprintf (buf, "\033[%d;%dr",
+                              y + 1 - con.b.srWindow.Top,
+                              srBottom + 1 - con.b.srWindow.Top);
+             WriteConsoleA (get_output_handle (), buf, strlen (buf), &wn, 0);
+             wpbuf_put ('T');
+             WriteConsoleA (get_output_handle (), wpbuf, wpixput, &wn, 0);
+             __small_sprintf (buf, "\033[%d;%dr",
+                              srTop + 1 - con.b.srWindow.Top,
+                              srBottom + 1 - con.b.srWindow.Top);
+             WriteConsoleA (get_output_handle (), buf, strlen (buf), &wn, 0);
+             __small_sprintf (buf, "\033[%d;%dH",
+                              y + 1 - con.b.srWindow.Top, x + 1);
+             WriteConsoleA (get_output_handle (), buf, strlen (buf), &wn, 0);
+           }
+         else
+           {
+             wpbuf_put (c);
+             /* Just send the sequence */
+             WriteConsoleA (get_output_handle (), wpbuf, wpixput, &wn, 0);
+           }
+         break;
+       case 'M': /* DL */
+         if (wincap.has_con_broken_il_dl ())
+           {
+             /* Use "CSI Ps S" instead */
+             cursor_get (&x, &y);
+             __small_sprintf (buf, "\033[%d;%dr",
+                              y + 1 - con.b.srWindow.Top,
+                              srBottom + 1 - con.b.srWindow.Top);
+             WriteConsoleA (get_output_handle (), buf, strlen (buf), &wn, 0);
+             wpbuf_put ('S');
+             WriteConsoleA (get_output_handle (), wpbuf, wpixput, &wn, 0);
+             __small_sprintf (buf, "\033[%d;%dr",
+                              srTop + 1 - con.b.srWindow.Top,
+                              srBottom + 1 - con.b.srWindow.Top);
+             WriteConsoleA (get_output_handle (), buf, strlen (buf), &wn, 0);
+             __small_sprintf (buf, "\033[%d;%dH",
+                              y + 1 - con.b.srWindow.Top, x + 1);
+             WriteConsoleA (get_output_handle (), buf, strlen (buf), &wn, 0);
+           }
+         else
+           {
+             wpbuf_put (c);
+             /* Just send the sequence */
+             WriteConsoleA (get_output_handle (), wpbuf, wpixput, &wn, 0);
+           }
+         break;
+       default:
+         /* Other escape sequences */
+         wpbuf_put (c);
+         /* Just send the sequence */
+         WriteConsoleA (get_output_handle (), wpbuf, wpixput, &wn, 0);
+         break;
+       }
+      return;
+    }
+
+  /* For legacy cygwin treminal */
   switch (c)
     {
     case 'm':   /* Set Graphics Rendition */
@@ -2641,6 +2727,7 @@ fhandler_console::write_normal (const unsigned char *src,
   while (found < end
         && found - src < CONVERT_LIMIT
         && base_chars[*found] != IGN
+        && base_chars[*found] != ESC
         && ((wincap.has_con_24bit_colors () && !con_is_legacy)
             || base_chars[*found] == NOR))
     {
@@ -2712,6 +2799,7 @@ do_print:
          break;
        case ESC:
          con.state = gotesc;
+         wpbuf_put (*found);
          break;
        case DWN:
          cursor_get (&x, &y);
@@ -2826,6 +2914,7 @@ fhandler_console::write (const void *vsrc, size_t len)
        case gotesc:
          if (*src == '[')              /* CSI Control Sequence Introducer */
            {
+             wpbuf_put (*src);
              con.state = gotsquare;
              memset (con.args, 0, sizeof con.args);
              con.nargs = 0;
@@ -2833,18 +2922,55 @@ fhandler_console::write (const void *vsrc, size_t len)
              con.saw_greater_than_sign = false;
              con.saw_space = false;
            }
+         else if (wincap.has_con_24bit_colors () && !con_is_legacy
+                  && wincap.has_con_broken_il_dl () && *src == 'M')
+           { /* Reverse Index (scroll down) */
+             int x, y;
+             DWORD n;
+             cursor_get (&x, &y);
+             if (y == srTop)
+               {
+                 /* Erase scroll down area */
+                 char buf[] = "\033[32768;1H\033[J\033[32768;32768";
+                 __small_sprintf (buf, "\033[%d;1H\033[J\033[%d;%dH",
+                            srBottom - con.b.srWindow.Top + 1,
+                            y + 1 - con.b.srWindow.Top, x + 1);
+                 WriteConsoleA (get_output_handle (),
+                                buf, strlen (buf), &n, 0);
+                 /* Substitute "CSI Ps T" */
+                 wpbuf_put ('[');
+                 wpbuf_put ('T');
+               }
+             else
+               wpbuf_put (*src);
+             WriteConsoleA (get_output_handle (), wpbuf, wpixput, &n, 0);
+             con.state = normal;
+             wpixput = 0;
+           }
+         else if (wincap.has_con_24bit_colors () && !con_is_legacy)
+           { /* Only CSI is handled in xterm compatible mode. */
+             wpbuf_put (*src);
+             /* Just send the sequence */
+             DWORD n;
+             WriteConsoleA (get_output_handle (), wpbuf, wpixput, &n, 0);
+             con.state = normal;
+             wpixput = 0;
+           }
          else if (*src == ']')         /* OSC Operating System Command */
            {
+             wpbuf_put (*src);
              con.rarg = 0;
              con.my_title_buf[0] = '\0';
              con.state = gotrsquare;
            }
          else if (*src == '(')         /* Designate G0 character set */
            {
+             wpbuf_put (*src);
              con.state = gotparen;
            }
          else if (*src == ')')         /* Designate G1 character set */
            {
+             wpbuf_put (*src);
              con.state = gotrparen;
            }
          else if (*src == 'M')         /* Reverse Index (scroll down) */
@@ -2852,6 +2978,7 @@ fhandler_console::write (const void *vsrc, size_t len)
              con.fillin (get_output_handle ());
              scroll_buffer_screen (0, 0, -1, -1, 0, 1);
              con.state = normal;
+             wpixput = 0;
            }
          else if (*src == 'c')         /* RIS Full Reset */
            {
@@ -2862,22 +2989,29 @@ fhandler_console::write (const void *vsrc, size_t len)
              cursor_set (false, 0, 0);
              clear_screen (cl_buf_beg, cl_buf_beg, cl_buf_end, cl_buf_end);
              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;
+             wpixput = 0;
+           }
          else
            {
              con.state = normal;
+             wpixput = 0;
            }
          src++;
          break;
@@ -2885,10 +3019,12 @@ fhandler_console::write (const void *vsrc, size_t len)
          if (isdigit (*src))
            {
              con.args[con.nargs] = con.args[con.nargs] * 10 + *src - '0';
+             wpbuf_put (*src);
              src++;
            }
          else if (*src == ';')
            {
+             wpbuf_put (*src);
              src++;
              con.nargs++;
              if (con.nargs > MAXARGS)
@@ -2896,6 +3032,7 @@ fhandler_console::write (const void *vsrc, size_t len)
            }
          else if (*src == ' ')
            {
+             wpbuf_put (*src);
              src++;
              con.saw_space = true;
              con.state = gotcommand;
@@ -2909,6 +3046,7 @@ fhandler_console::write (const void *vsrc, size_t len)
            con.nargs--;
          char_command (*src++);
          con.state = normal;
+         wpixput = 0;
          break;
        case gotrsquare:
          if (isdigit (*src))
@@ -2919,6 +3057,7 @@ fhandler_console::write (const void *vsrc, size_t len)
            con.state = eatpalette;
          else
            con.state = eattitle;
+         wpbuf_put (*src);
          src++;
          break;
        case eattitle:
@@ -2930,20 +3069,28 @@ fhandler_console::write (const void *vsrc, size_t len)
                if (*src == '\007' && con.state == gettitle)
                  set_console_title (con.my_title_buf);
                con.state = normal;
+               wpixput = 0;
              }
            else if (n < TITLESIZE)
              {
                con.my_title_buf[n++] = *src;
                con.my_title_buf[n] = '\0';
+               wpbuf_put (*src);
              }
            src++;
            break;
          }
        case eatpalette:
          if (*src == '\033')
-           con.state = endpalette;
+           {
+             wpbuf_put (*src);
+             con.state = endpalette;
+           }
          else if (*src == '\a')
-           con.state = normal;
+           {
+             con.state = normal;
+             wpixput = 0;
+           }
          src++;
          break;
        case endpalette:
@@ -2952,12 +3099,14 @@ fhandler_console::write (const void *vsrc, size_t len)
          else
            /* Sequence error (abort) */
            con.state = normal;
+         wpixput = 0;
          src++;
          break;
        case gotsquare:
          if (*src == ';')
            {
              con.state = gotarg1;
+             wpbuf_put (*src);
              con.nargs++;
              if (con.nargs > MAXARGS)
                con.nargs--;
@@ -2971,6 +3120,7 @@ fhandler_console::write (const void *vsrc, size_t len)
                con.saw_question_mark = true;
              else if (*src == '>')
                con.saw_greater_than_sign = true;
+             wpbuf_put (*src);
              /* ignore any extra chars between [ and first arg or command */
              src++;
            }
@@ -2983,6 +3133,7 @@ fhandler_console::write (const void *vsrc, size_t len)
          else
            con.vt100_graphics_mode_G0 = false;
          con.state = normal;
+         wpixput = 0;
          src++;
          break;
        case gotrparen: /* Designate G1 Character Set (ISO 2022) */
@@ -2991,6 +3142,7 @@ fhandler_console::write (const void *vsrc, size_t len)
          else
            con.vt100_graphics_mode_G1 = false;
          con.state = normal;
+         wpixput = 0;
          src++;
          break;
        }
diff --git a/winsup/cygwin/wincap.cc b/winsup/cygwin/wincap.cc
index a52262b89..714a6d49f 100644
--- a/winsup/cygwin/wincap.cc
+++ b/winsup/cygwin/wincap.cc
@@ -43,6 +43,7 @@ wincaps wincap_vista __attribute__((section 
(".cygwin_dll_common"), shared)) = {
     no_msv1_0_s4u_logon_in_wow64:true,
     has_con_24bit_colors:false,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -71,6 +72,7 @@ wincaps wincap_7 __attribute__((section 
(".cygwin_dll_common"), shared)) = {
     no_msv1_0_s4u_logon_in_wow64:true,
     has_con_24bit_colors:false,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -99,6 +101,7 @@ wincaps wincap_8 __attribute__((section 
(".cygwin_dll_common"), shared)) = {
     no_msv1_0_s4u_logon_in_wow64:false,
     has_con_24bit_colors:false,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -127,6 +130,7 @@ wincaps wincap_8_1 __attribute__((section 
(".cygwin_dll_common"), shared)) = {
     no_msv1_0_s4u_logon_in_wow64:false,
     has_con_24bit_colors:false,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -155,6 +159,7 @@ wincaps  wincap_10_1507 __attribute__((section 
(".cygwin_dll_common"), shared))
     no_msv1_0_s4u_logon_in_wow64:false,
     has_con_24bit_colors:false,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -183,6 +188,7 @@ wincaps wincap_10_1703 __attribute__((section 
(".cygwin_dll_common"), shared)) =
     no_msv1_0_s4u_logon_in_wow64:false,
     has_con_24bit_colors:true,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -211,6 +217,7 @@ wincaps wincap_10_1709 __attribute__((section 
(".cygwin_dll_common"), shared)) =
     no_msv1_0_s4u_logon_in_wow64:false,
     has_con_24bit_colors:true,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -239,6 +246,7 @@ wincaps wincap_10_1803 __attribute__((section 
(".cygwin_dll_common"), shared)) =
     no_msv1_0_s4u_logon_in_wow64:false,
     has_con_24bit_colors:true,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -267,6 +275,7 @@ wincaps wincap_10_1809 __attribute__((section 
(".cygwin_dll_common"), shared)) =
     no_msv1_0_s4u_logon_in_wow64:false,
     has_con_24bit_colors:true,
     has_con_broken_csi3j:true,
+    has_con_broken_il_dl:false,
   },
 };
 
@@ -295,6 +304,7 @@ wincaps wincap_10_1903 __attribute__((section 
(".cygwin_dll_common"), shared)) =
     no_msv1_0_s4u_logon_in_wow64:false,
     has_con_24bit_colors:true,
     has_con_broken_csi3j:false,
+    has_con_broken_il_dl:true,
   },
 };
 
diff --git a/winsup/cygwin/wincap.h b/winsup/cygwin/wincap.h
index 11902d976..f85a88877 100644
--- a/winsup/cygwin/wincap.h
+++ b/winsup/cygwin/wincap.h
@@ -37,6 +37,7 @@ struct wincaps
     unsigned no_msv1_0_s4u_logon_in_wow64      : 1;
     unsigned has_con_24bit_colors              : 1;
     unsigned has_con_broken_csi3j              : 1;
+    unsigned has_con_broken_il_dl              : 1;
   };
 };
 
@@ -97,6 +98,7 @@ public:
   bool IMPLEMENT (no_msv1_0_s4u_logon_in_wow64)
   bool IMPLEMENT (has_con_24bit_colors)
   bool IMPLEMENT (has_con_broken_csi3j)
+  bool IMPLEMENT (has_con_broken_il_dl)
 
   void disable_case_sensitive_dirs ()
   {
-- 
2.21.0

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