Revert "tui: improve support for tmux, GNU Screen" (#14786)

* Revert "tui: improve support for tmux, GNU Screen"

This reverts commit c266c2f36ea56220268d2b19364e28815e338c2f.

This commit broke neovim under tmux, where it "types" the background
string as input to the terminal. Fixing this with neovim as-is requires
changing tmux keybindings or TERM settings, which has to be done by
every single user, therefore a fix should happen on neovim's side.

Fixes #14298

* tui: fix code lints.

2 files changed, 11 insertions, 22 deletions

diff --git a/src/nvim/ascii.h b/src/nvim/ascii.h
index 7e4dee3d34..f41068ea70 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 fd83681aed..6e885279a9 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -52,21 +52,18 @@
 #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 TMUX_WRAP(is_tmux, seq) ((is_tmux) \
-                                 ? DCS_STR "tmux;\x1b" 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"
 
 #ifdef NVIM_UNIBI_HAS_VAR_FROM
 #define UNIBI_SET_NUM_VAR(var, num) \
   do { \
-    (var) = unibi_var_from_num((num)); \
+      (var) = unibi_var_from_num((num)); \
   } while (0)
 #else
 #define UNIBI_SET_NUM_VAR(var, num) (var).i = (num);
@@ -301,12 +298,6 @@ static void terminfo_start(UI *ui)
                                      data->invis, sizeof data->invis);
   // Set 't_Co' from the result of unibilium & fix_terminfo.
   t_colors = unibi_get_num(data->ut, unibi_max_colors);
-  // Ask the terminal to send us the background color.
-  // If get_bg is sent at the same time after enter_ca_mode, tmux will not send
-  // get_bg to the host terminal. To avoid this, send get_bg before
-  // enter_ca_mode.
-  data->input.waiting_for_bg_response = 5;
-  unibi_out_ext(ui, data->unibi_ext.get_bg);
   // Enter alternate screen, save title, and clear.
   // NOTE: Do this *before* changing terminal settings. #6433
   unibi_out(ui, unibi_enter_ca_mode);
@@ -314,6 +305,9 @@ static void terminfo_start(UI *ui)
   unibi_out_ext(ui, data->unibi_ext.save_title);
   unibi_out(ui, unibi_keypad_xmit);
   unibi_out(ui, unibi_clear_screen);
+  // Ask the terminal to send us the background color.
+  data->input.waiting_for_bg_response = 5;
+  unibi_out_ext(ui, data->unibi_ext.get_bg);
   // Enable bracketed paste
   unibi_out_ext(ui, data->unibi_ext.enable_bracketed_paste);
 
@@ -335,7 +329,6 @@ static void terminfo_start(UI *ui)
     uv_pipe_init(&data->write_loop, &data->output_handle.pipe, 0);
     uv_pipe_open(&data->output_handle.pipe, data->out_fd);
   }
-
   flush_buf(ui);
 }
 
@@ -1780,10 +1773,8 @@ 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), 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) {