Revert "tui: improve support for GNU Screen (#12098)"

This reverts commit f3ffe0b325170dd214b80e371bee5a56b7054940.
Sending a control sequence to the host terminal, wrapped in DCS, causes
problems because it changes the state of the host terminal outside the
screen's control. This change will therefore be reverted.

2 files changed, 43 insertions, 106 deletions

diff --git a/src/nvim/ascii.h b/src/nvim/ascii.h
index 31423e79af..2397af27cc 100644
--- a/src/nvim/ascii.h
+++ b/src/nvim/ascii.h
@@ -31,9 +31,7 @@
 #define CSI             0x9b    // Control Sequence Introducer
 #define CSI_STR         "\233"
 #define DCS             0x90    // Device Control String
-#define DCS_STR         "\033P"
 #define STERM           0x9c    // String Terminator
-#define STERM_STR       "\033\\"
 
 #define POUND           0xA3
 
diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index a0e7a26b16..3b71066094 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -52,15 +52,10 @@
 #define OUTBUF_SIZE 0xffff
 
 #define TOO_MANY_EVENTS 1000000
-#define STARTS_WITH(str, prefix) \
-  (strlen(str) >= (sizeof(prefix) - 1) && 0 == memcmp((str), (prefix), \
-                                                      sizeof(prefix) - 1))
-#define SCREEN_WRAP(is_screen, seq) ((is_screen) \
-                                     ? DCS_STR seq STERM_STR : seq)
-#define SCREEN_TMUX_WRAP(is_screen, is_tmux, seq) \
-    ((is_screen) \
-     ? DCS_STR seq STERM_STR : (is_tmux) \
-     ? DCS_STR "tmux;\x1b" seq STERM_STR : seq)
+#define STARTS_WITH(str, prefix) (strlen(str) >= (sizeof(prefix) - 1) \
+    && 0 == memcmp((str), (prefix), sizeof(prefix) - 1))
+#define TMUX_WRAP(is_tmux, seq) ((is_tmux) \
+    ? "\x1bPtmux;\x1b" seq "\x1b\\" : seq)
 #define LINUXSET0C "\x1b[?0c"
 #define LINUXSET1C "\x1b[?1c"
 
@@ -1574,10 +1569,7 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
   bool rxvt = terminfo_is_term_family(term, "rxvt");
   bool teraterm = terminfo_is_term_family(term, "teraterm");
   bool putty = terminfo_is_term_family(term, "putty");
-  bool screen = terminfo_is_term_family(term, "screen") && !os_getenv("TMUX");
-  bool screen_host_linuxvt =
-    terminfo_is_term_family(screen && term[6] == '.'
-                            ? term + 7 : NULL, "linux");
+  bool screen = terminfo_is_term_family(term, "screen");
   bool tmux = terminfo_is_term_family(term, "tmux") || !!os_getenv("TMUX");
   bool st = terminfo_is_term_family(term, "st");
   bool gnome = terminfo_is_term_family(term, "gnome")
@@ -1736,9 +1728,8 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
 #define XTERM_SETAB_16 \
   "\x1b[%?%p1%{8}%<%t4%p1%d%e%p1%{16}%<%t10%p1%{8}%-%d%e39%;m"
 
-  data->unibi_ext.get_bg =
-    (int)unibi_add_ext_str(ut, "ext.get_bg",
-                           SCREEN_TMUX_WRAP(screen, tmux, "\x1b]11;?\x07"));
+  data->unibi_ext.get_bg = (int)unibi_add_ext_str(ut, "ext.get_bg",
+                                                  "\x1b]11;?\x07");
 
   // Terminals with 256-colour SGR support despite what terminfo says.
   if (unibi_get_num(ut, unibi_max_colors) < 256) {
@@ -1773,32 +1764,6 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
     data->unibi_ext.set_cursor_style = unibi_find_ext_str(ut, "Ss");
   }
 
-  // GNU Screen does not have Ss/Se. When terminfo has Ss/Se, it is wrapped with
-  // DCS because it is inherited from the host terminal.
-  if (screen) {
-    size_t len;
-    size_t dcs_st_len = strlen(DCS_STR) + strlen(STERM_STR);
-    if (-1 != data->unibi_ext.set_cursor_style) {
-      const char *orig_ss =
-        unibi_get_ext_str(data->ut, (size_t)data->unibi_ext.reset_cursor_style);
-      len = STRLEN(orig_ss) + dcs_st_len + 1;
-      char *ss = xmalloc(len);
-      snprintf(ss, len, "%s%s%s", DCS_STR, orig_ss, STERM_STR);
-      unibi_set_ext_str(data->ut, (size_t)data->unibi_ext.set_cursor_style, ss);
-      xfree(ss);
-    }
-    if (-1 != data->unibi_ext.reset_cursor_style) {
-      const char *orig_se =
-        unibi_get_ext_str(data->ut, (size_t)data->unibi_ext.reset_cursor_style);
-      len = strlen(orig_se) + dcs_st_len + 1;
-      char *se = xmalloc(len);
-      snprintf(se, len, "%s%s%s", DCS_STR, orig_se, STERM_STR);
-      unibi_set_ext_str(data->ut,
-                        (size_t)data->unibi_ext.reset_cursor_style, se);
-      xfree(se);
-    }
-  }
-
   // Dickey ncurses terminfo includes Ss/Se capabilities since 2011-07-14. So
   // adding them to terminal types, that have such control sequences but lack
   // the correct terminfo entries, is a fixup, not an augmentation.
@@ -1814,12 +1779,7 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
             || (konsolev >= 180770)  // #9364
             || tmux       // per tmux manual page
             // https://lists.gnu.org/archive/html/screen-devel/2013-03/msg00000.html
-            || (screen
-                && (!screen_host_linuxvt
-                    || (screen_host_linuxvt
-                        && (xterm_version || (vte_version > 0) || colorterm))))
-            // Since GNU Screen does not support DECSCUSR, DECSCUSR is wrapped
-            // in DCS and output to the host terminal.
+            || screen
             || st         // #7641
             || rxvt       // per command.C
             // per analysis of VT100Terminal.m
@@ -1832,43 +1792,34 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
             || (linuxvt
                 && (xterm_version || (vte_version > 0) || colorterm)))) {
       data->unibi_ext.set_cursor_style =
-        (int)unibi_add_ext_str(ut, "Ss", SCREEN_WRAP(screen, "\x1b[%p1%d q"));
+        (int)unibi_add_ext_str(ut, "Ss", "\x1b[%p1%d q");
       if (-1 == data->unibi_ext.reset_cursor_style) {
           data->unibi_ext.reset_cursor_style = (int)unibi_add_ext_str(ut, "Se",
                                                                       "");
       }
       unibi_set_ext_str(ut, (size_t)data->unibi_ext.reset_cursor_style,
-                        SCREEN_WRAP(screen, "\x1b[ q"));
-    } else if (linuxvt || screen_host_linuxvt) {
+                        "\x1b[ q");
+    } else if (linuxvt) {
       // Linux uses an idiosyncratic escape code to set the cursor shape and
       // does not support DECSCUSR.
       // See http://linuxgazette.net/137/anonymous.html for more info
-      //
-      // Since gnu Screen does not have Ss/Se, if the host terminal is a linux
-      // console that does not support xterm extensions, it will wraps the
-      // linux-specific sequence in DCS and outputs it.
-      data->unibi_ext.set_cursor_style = (int)unibi_add_ext_str(
-          ut, "Ss",
-          SCREEN_WRAP(screen,
-                      "\x1b[?"
-                      "%?"
-                      // The parameter passed to Ss is the DECSCUSR parameter,
-                      // so the
-                      // terminal capability has to translate into the Linux
-                      // idiosyncratic parameter.
-                      //
-                      // linuxvt only supports block and underline. It is also
-                      // only possible to have a steady block (no steady
-                      // underline)
-                      "%p1%{2}%<" "%t%{8}"       // blink block
-                      "%e%p1%{2}%=" "%t%{112}"   // steady block
-                      "%e%p1%{3}%=" "%t%{4}"     // blink underline (set to half
-                                                 // block)
-                      "%e%p1%{4}%=" "%t%{4}"     // steady underline
-                      "%e%p1%{5}%=" "%t%{2}"     // blink bar (set to underline)
-                      "%e%p1%{6}%=" "%t%{2}"     // steady bar
-                      "%e%{0}"                   // anything else
-                      "%;" "%dc"));
+      data->unibi_ext.set_cursor_style = (int)unibi_add_ext_str(ut, "Ss",
+          "\x1b[?"
+          "%?"
+          // The parameter passed to Ss is the DECSCUSR parameter, so the
+          // terminal capability has to translate into the Linux idiosyncratic
+          // parameter.
+          //
+          // linuxvt only supports block and underline. It is also only
+          // possible to have a steady block (no steady underline)
+          "%p1%{2}%<" "%t%{8}"       // blink block
+          "%e%p1%{2}%=" "%t%{112}"   // steady block
+          "%e%p1%{3}%=" "%t%{4}"     // blink underline (set to half block)
+          "%e%p1%{4}%=" "%t%{4}"     // steady underline
+          "%e%p1%{5}%=" "%t%{2}"     // blink bar (set to underline)
+          "%e%p1%{6}%=" "%t%{2}"     // steady bar
+          "%e%{0}"                   // anything else
+          "%;" "%dc");
       if (-1 == data->unibi_ext.reset_cursor_style) {
           data->unibi_ext.reset_cursor_style = (int)unibi_add_ext_str(ut, "Se",
                                                                       "");
@@ -1878,25 +1829,21 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
     } else if (konsolev > 0 && konsolev < 180770) {
       // Konsole before version 18.07.70: set up a nonce profile. This has
       // side-effects on temporary font resizing. #6798
-      data->unibi_ext.set_cursor_style = (int)unibi_add_ext_str(
-          ut, "Ss",
-          SCREEN_TMUX_WRAP(screen, tmux,
-                           "\x1b]50;CursorShape=%?"
-                           "%p1%{3}%<" "%t%{0}"    // block
-                           "%e%p1%{5}%<" "%t%{2}"  // underline
-                           "%e%{1}"                // everything else is bar
-                           "%;%d;BlinkingCursorEnabled=%?"
-                           "%p1%{1}%<" "%t%{1}"  // Fortunately if we exclude
-                                                 // zero as special,
-                           "%e%p1%{1}%&"  // in all other c2ses we can treat bit
-                                          // #0 as a flag.
-                           "%;%d\x07"));
+      data->unibi_ext.set_cursor_style = (int)unibi_add_ext_str(ut, "Ss",
+          TMUX_WRAP(tmux, "\x1b]50;CursorShape=%?"
+          "%p1%{3}%<" "%t%{0}"    // block
+          "%e%p1%{5}%<" "%t%{2}"  // underline
+          "%e%{1}"                // everything else is bar
+          "%;%d;BlinkingCursorEnabled=%?"
+          "%p1%{1}%<" "%t%{1}"  // Fortunately if we exclude zero as special,
+          "%e%p1%{1}%&"  // in all other cases we can treat bit #0 as a flag.
+          "%;%d\x07"));
       if (-1 == data->unibi_ext.reset_cursor_style) {
           data->unibi_ext.reset_cursor_style = (int)unibi_add_ext_str(ut, "Se",
                                                                       "");
       }
       unibi_set_ext_str(ut, (size_t)data->unibi_ext.reset_cursor_style,
-                        SCREEN_TMUX_WRAP(screen, tmux, "\x1b]50;\x07"));
+          "\x1b]50;\x07");
     }
   }
 }
@@ -1925,8 +1872,6 @@ static void augment_terminfo(TUIData *data, const char *term,
   bool alacritty = terminfo_is_term_family(term, "alacritty");
   // None of the following work over SSH; see :help TERM .
   bool iterm_pretending_xterm = xterm && iterm_env;
-  bool screen_host_rxvt =
-    terminfo_is_term_family(screen && term[6] == '.' ? term + 7 : NULL, "rxvt");
 
   const char *xterm_version = os_getenv("XTERM_VERSION");
   bool true_xterm = xterm && !!xterm_version && !bsdvt;
@@ -1996,7 +1941,7 @@ static void augment_terminfo(TUIData *data, const char *term,
     // all panes, which is not particularly desirable.  A better approach
     // would use a tmux control sequence and an extra if(screen) test.
     data->unibi_ext.set_cursor_color = (int)unibi_add_ext_str(
-        ut, NULL, SCREEN_TMUX_WRAP(screen, tmux, "\033]Pl%p1%06x\033\\"));
+        ut, NULL, TMUX_WRAP(tmux, "\033]Pl%p1%06x\033\\"));
   } else if ((xterm || rxvt || tmux || alacritty)
              && (vte_version == 0 || vte_version >= 3900)) {
     // Supported in urxvt, newer VTE.
@@ -2016,27 +1961,21 @@ static void augment_terminfo(TUIData *data, const char *term,
 
   /// Terminals usually ignore unrecognized private modes, and there is no
   /// known ambiguity with these. So we just set them unconditionally.
-  /// If the DECSET is not supported by GNU Screen, it is wrapped with DCS and
-  /// sent to the host terminal.
   data->unibi_ext.enable_lr_margin = (int)unibi_add_ext_str(
       ut, "ext.enable_lr_margin", "\x1b[?69h");
   data->unibi_ext.disable_lr_margin = (int)unibi_add_ext_str(
       ut, "ext.disable_lr_margin", "\x1b[?69l");
   data->unibi_ext.enable_bracketed_paste = (int)unibi_add_ext_str(
-      ut, "ext.enable_bpaste", SCREEN_WRAP(screen, "\x1b[?2004h"));
+      ut, "ext.enable_bpaste", "\x1b[?2004h");
   data->unibi_ext.disable_bracketed_paste = (int)unibi_add_ext_str(
-      ut, "ext.disable_bpaste", SCREEN_WRAP(screen, "\x1b[?2004l"));
+      ut, "ext.disable_bpaste", "\x1b[?2004l");
   // For urxvt send BOTH xterm and old urxvt sequences. #8695
   data->unibi_ext.enable_focus_reporting = (int)unibi_add_ext_str(
       ut, "ext.enable_focus",
-      (rxvt || screen_host_rxvt)
-      ? SCREEN_WRAP(screen, "\x1b[?1004h\x1b]777;focus;on\x7")
-      : SCREEN_WRAP(screen, "\x1b[?1004h"));
+      rxvt ? "\x1b[?1004h\x1b]777;focus;on\x7" : "\x1b[?1004h");
   data->unibi_ext.disable_focus_reporting = (int)unibi_add_ext_str(
       ut, "ext.disable_focus",
-      (rxvt || screen_host_rxvt)
-      ? SCREEN_WRAP(screen, "\x1b[?1004l\x1b]777;focus;off\x7")
-      : SCREEN_WRAP(screen, "\x1b[?1004l"));
+      rxvt ? "\x1b[?1004l\x1b]777;focus;off\x7" : "\x1b[?1004l");
   data->unibi_ext.enable_mouse = (int)unibi_add_ext_str(
       ut, "ext.enable_mouse", "\x1b[?1002h\x1b[?1006h");
   data->unibi_ext.disable_mouse = (int)unibi_add_ext_str(