Merge PR #1820 'Reimplement builtin terminal UI with termkey/unibilium'

42 files changed, 1439 insertions, 4800 deletions

diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index 6fc5022d48..922b8b85a1 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -26,13 +26,16 @@ file(MAKE_DIRECTORY ${GENERATED_DIR}/os)
 file(MAKE_DIRECTORY ${GENERATED_DIR}/api)
 file(MAKE_DIRECTORY ${GENERATED_DIR}/api/private)
 file(MAKE_DIRECTORY ${GENERATED_DIR}/msgpack_rpc)
+file(MAKE_DIRECTORY ${GENERATED_DIR}/tui)
 file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR})
 file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR}/os)
 file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR}/api)
 file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR}/api/private)
 file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR}/msgpack_rpc)
+file(MAKE_DIRECTORY ${GENERATED_INCLUDES_DIR}/tui)
 
-file(GLOB NEOVIM_SOURCES *.c os/*.c api/*.c api/private/*.c msgpack_rpc/*.c)
+file(GLOB NEOVIM_SOURCES *.c os/*.c api/*.c api/private/*.c msgpack_rpc/*.c
+  tui/*.c)
 file(GLOB_RECURSE NEOVIM_HEADERS *.h)
 
 foreach(sfile ${NEOVIM_SOURCES})
@@ -164,19 +167,6 @@ if (LibIntl_FOUND)
   list(APPEND NVIM_LINK_LIBRARIES ${LibIntl_LIBRARY})
 endif()
 
-check_library_exists(curses tgetent "" HAVE_LIBCURSES)
-if (HAVE_LIBCURSES)
-  list(APPEND NVIM_LINK_LIBRARIES curses)
-else()
-  check_library_exists(tinfo tgetent "" HAVE_LIBTINFO)
-  if (HAVE_LIBTINFO)
-    list(APPEND NVIM_LINK_LIBRARIES tinfo)
-  else()
-    find_package(Curses REQUIRED)
-    list(APPEND NVIM_LINK_LIBRARIES ${CURSES_LIBRARY})
-  endif()
-endif()
-
 if(Iconv_LIBRARIES)
   list(APPEND NVIM_LINK_LIBRARIES ${Iconv_LIBRARIES})
 endif()
@@ -186,8 +176,12 @@ list(APPEND NVIM_LINK_LIBRARIES
     ${LIBUV_LIBRARIES}
     ${MSGPACK_LIBRARIES}
     ${LUAJIT_LIBRARIES}
+    ${LIBTICKIT_LIBRARIES}
+    ${LIBTERMKEY_LIBRARIES}
+    ${LIBUNIBILIUM_LIBRARIES}
     m
-    ${CMAKE_THREAD_LIBS_INIT})
+    ${CMAKE_THREAD_LIBS_INIT}
+    )
 
 add_executable(nvim ${NEOVIM_GENERATED_SOURCES} ${NEOVIM_SOURCES}
   ${NEOVIM_HEADERS})
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index 6fb5ebf3e4..b8fcd2de09 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -1849,25 +1849,6 @@ int hex2nr(int c)
   return c - '0';
 }
 
-#if defined(FEAT_TERMRESPONSE) || defined(FEAT_GUI_GTK)
-
-/// Convert two hex characters to a byte.
-/// Return -1 if one of the characters is not hex.
-///
-/// @param p
-///
-/// @return The two hex characters converted to a byte or -1 if one of the
-///         character is not hex.
-int hexhex2nr(char_u *p)
-{
-  if (!vim_isxdigit(p[0]) || !vim_isxdigit(p[1])) {
-    return -1;
-  }
-  return (hex2nr(p[0]) << 4) + hex2nr(p[1]);
-}
-
-#endif  // if defined(FEAT_TERMRESPONSE) || defined(FEAT_GUI_GTK)
-
 /// Return true if "str" starts with a backslash that should be removed.
 /// For WIN32 this is only done when the character after the
 /// backslash is not a normal file name character.
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index a4bd4d89ef..97993eb651 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -9955,14 +9955,8 @@ static void f_has(typval_T *argvars, typval_T *rettv)
 #endif
     "tag_binary",
     "tag_old_static",
-#ifdef TERMINFO
-    "terminfo",
-#endif
     "termresponse",
     "textobjects",
-#ifdef HAVE_TGETENT
-    "tgetent",
-#endif
     "title",
     "user-commands",        /* was accidentally included in 5.4 */
     "user_commands",
@@ -14424,13 +14418,10 @@ static void f_synIDattr(typval_T *argvars, typval_T *rettv)
   if (argvars[2].v_type != VAR_UNKNOWN) {
     mode = get_tv_string_buf(&argvars[2], modebuf);
     modec = TOLOWER_ASC(mode[0]);
-    if (modec != 't' && modec != 'c' && modec != 'g')
+    if (modec != 'c' && modec != 'g')
       modec = 0;        /* replace invalid with current */
   } else {
-    if (abstract_ui || t_colors > 1)
-      modec = 'c';
-    else
-      modec = 't';
+    modec = 'c';
   }
 
 
@@ -18080,21 +18071,6 @@ static int function_exists(char_u *name)
   return n;
 }
 
-char_u *get_expanded_name(char_u *name, int check)
-{
-  char_u      *nm = name;
-  char_u      *p;
-
-  p = trans_function_name(&nm, FALSE, TFN_INT|TFN_QUIET, NULL);
-
-  if (p != NULL && *nm == NUL)
-    if (!check || translated_function_exists(p))
-      return p;
-
-  free(p);
-  return NULL;
-}
-
 /// Return TRUE if "name" looks like a builtin function name: starts with a
 /// lower case letter and doesn't contain AUTOLOAD_CHAR.
 /// "len" is the length of "name", or -1 for NUL terminated.
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index b03c25a098..49f33c5017 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -1232,9 +1232,6 @@ do_shell (
    * avoid having to type return below.
    */
   msg_putchar('\r');                    /* put cursor at start of line */
-  if (!autocmd_busy) {
-    stoptermcap();
-  }
   msg_putchar('\n');                    /* may shift screen one line up */
 
   /* warning message before calling the shell */
@@ -1292,8 +1289,6 @@ do_shell (
       wait_return(msg_silent == 0);
       no_wait_return = save_nwr;
     }
-
-    starttermcap();             /* start termcap if not done by wait_return() */
   }
 
   /* display any error messages now */
diff --git a/src/nvim/ex_cmds.lua b/src/nvim/ex_cmds.lua
index aade4d736d..98a2b2814d 100644
--- a/src/nvim/ex_cmds.lua
+++ b/src/nvim/ex_cmds.lua
@@ -2483,7 +2483,7 @@ return {
   {
     command='winpos',
     flags=bit.bor(EXTRA, TRLBAR, CMDWIN),
-    func='ex_winpos',
+    func='ex_ni',
   },
   {
     command='wnext',
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 7de47cb296..9bcbfa2f26 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -155,10 +155,6 @@ void do_debug(char_u *cmd)
 #define CMD_INTERRUPT   6
 
 
-  /* Make sure we are in raw mode and start termcap mode.  Might have side
-   * effects... */
-  starttermcap();
-
   ++RedrawingDisabled;          /* don't redisplay the window */
   ++no_wait_return;             /* don't wait for return */
   did_emsg = FALSE;             /* don't use error from debugged stuff */
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 9b48398d96..7ff69a3d41 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -146,10 +146,6 @@ struct dbg_stuff {
 # define gui_mch_find_dialog    ex_ni
 # define gui_mch_replace_dialog ex_ni
 # define ex_helpfind            ex_ni
-#if defined(FEAT_GUI) || defined(UNIX) || defined(MSWIN)
-#else
-# define ex_winpos          ex_ni
-#endif
 static int did_lcd;             /* whether ":lcd" was produced for a session */
 #ifndef HAVE_WORKING_LIBINTL
 # define ex_language            ex_ni
@@ -5397,13 +5393,11 @@ static void ex_stop(exarg_T *eap)
     windgoto((int)Rows - 1, 0);
     out_char('\n');
     out_flush();
-    stoptermcap();
     out_flush();                /* needed for SUN to restore xterm buffer */
     mch_restore_title(3);       /* restore window titles */
     ui_suspend();               /* call machine specific function */
     maketitle();
     resettitle();               /* force updating the title */
-    starttermcap();
     scroll_start();             /* scroll screen before redrawing */
     redraw_later_clear();
     shell_resized();            /* may have resized window */
@@ -6438,7 +6432,7 @@ static void ex_winsize(exarg_T *eap)
   p = arg;
   h = getdigits_int(&arg);
   if (*p != NUL && *arg == NUL)
-    screen_resize(w, h, TRUE);
+    screen_resize(w, h);
   else
     EMSG(_("E465: :winsize requires two number arguments"));
 }
@@ -6473,35 +6467,6 @@ static void ex_wincmd(exarg_T *eap)
   }
 }
 
-#if defined(FEAT_GUI) || defined(UNIX) || defined(MSWIN)
-/*
- * ":winpos".
- */
-static void ex_winpos(exarg_T *eap)
-{
-  int x, y;
-  char_u      *arg = eap->arg;
-  char_u      *p;
-
-  if (*arg == NUL) {
-    EMSG(_("E188: Obtaining window position not implemented for this platform"));
-  } else {
-    x = getdigits_int(&arg);
-    arg = skipwhite(arg);
-    p = arg;
-    y = getdigits_int(&arg);
-    if (*p == NUL || *arg != NUL) {
-      EMSG(_("E466: :winpos requires two number arguments"));
-      return;
-    }
-# ifdef HAVE_TGETENT
-    if (*T_CWP)
-      term_set_winpos(x, y);
-# endif
-  }
-}
-#endif
-
 /*
  * Handle command that work like operators: ":delete", ":yank", ":>" and ":<".
  */
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 2855f0cc12..6a3bd16feb 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -4618,35 +4618,6 @@ int del_history_idx(int histype, int idx)
   return TRUE;
 }
 
-
-/*
- * Very specific function to remove the value in ":set key=val" from the
- * history.
- */
-void remove_key_from_history(void)
-{
-  char_u      *p;
-  int i;
-
-  i = hisidx[HIST_CMD];
-  if (i < 0)
-    return;
-  p = history[HIST_CMD][i].hisstr;
-  if (p != NULL)
-    for (; *p; ++p)
-      if (STRNCMP(p, "key", 3) == 0 && !isalpha(p[3])) {
-        p = vim_strchr(p + 3, '=');
-        if (p == NULL)
-          break;
-        ++p;
-        for (i = 0; p[i] && !vim_iswhite(p[i]); ++i)
-          if (p[i] == '\\' && p[i + 1])
-            ++i;
-        STRMOVE(p, p + i);
-        --p;
-      }
-}
-
 /*
  * Get indices "num1,num2" that specify a range within a list (not a range of
  * text lines in a buffer!) from a string.  Used for ":history" and ":clist".
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index a4728b245b..dd6e5ace3f 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -1813,7 +1813,6 @@ failed:
      * Switch on raw mode now and clear the screen.
      */
     if (read_stdin) {
-      starttermcap();
       screenclear();
     }
 
@@ -6471,12 +6470,6 @@ int has_cmdundefined(void)
   return first_autopat[(int)EVENT_CMDUNDEFINED] != NULL;
 }
 
-/// @returns true when there is an FuncUndefined autocommand defined.
-int has_funcundefined(void)
-{
-  return first_autopat[(int)EVENT_FUNCUNDEFINED] != NULL;
-}
-
 static int 
 apply_autocmds_group (
     event_T event,
diff --git a/src/nvim/garray.c b/src/nvim/garray.c
index c3a3426e87..31a79db209 100644
--- a/src/nvim/garray.c
+++ b/src/nvim/garray.c
@@ -198,23 +198,3 @@ void ga_append(garray_T *gap, char c)
 {
   GA_APPEND(char, gap, c);
 }
-
-#if defined(UNIX) || defined(WIN3264)
-
-/// Append the text in "gap" below the cursor line and clear "gap".
-///
-/// @param gap
-void append_ga_line(garray_T *gap)
-{
-  // Remove trailing CR.
-  if (!GA_EMPTY(gap)
-      && !curbuf->b_p_bin
-      && (((char_u *)gap->ga_data)[gap->ga_len - 1] == CAR)) {
-    gap->ga_len--;
-  }
-  ga_append(gap, NUL);
-  ml_append(curwin->w_cursor.lnum++, gap->ga_data, 0, FALSE);
-  gap->ga_len = 0;
-}
-
-#endif  // if defined(UNIX) || defined(WIN3264)
diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index d97c983133..b8a145483f 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -1203,7 +1203,6 @@ void save_typeahead(tasave_T *tp)
   readbuf1.bh_first.b_next = NULL;
   tp->save_readbuf2 = readbuf2;
   readbuf2.bh_first.b_next = NULL;
-  tp->save_inputbuf = input_buffer_save();
 }
 
 /*
@@ -1224,7 +1223,6 @@ void restore_typeahead(tasave_T *tp)
   readbuf1 = tp->save_readbuf1;
   free_buff(&readbuf2);
   readbuf2 = tp->save_readbuf2;
-  input_buffer_restore(tp->save_inputbuf);
 }
 
 /*
@@ -1546,22 +1544,6 @@ int vpeekc(void)
 }
 
 /*
- * Like vpeekc(), but don't allow mapping.  Do allow checking for terminal
- * codes.
- */
-int vpeekc_nomap(void)
-{
-  int c;
-
-  ++no_mapping;
-  ++allow_keys;
-  c = vpeekc();
-  --no_mapping;
-  --allow_keys;
-  return c;
-}
-
-/*
  * Check if any character is available, also half an escape sequence.
  * Trick: when no typeahead found, but there is something in the typeahead
  * buffer, it must be an ESC that is recognized as the start of a key code.
@@ -1929,8 +1911,6 @@ static int vgetorpeek(int advance)
 
           if ((mp == NULL || max_mlen >= mp_match_len)
               && keylen != KEYLEN_PART_MAP) {
-            int save_keylen = keylen;
-
             /*
              * When no matching mapping found or found a
              * non-matching mapping that matches at least what the
@@ -1947,25 +1927,7 @@ static int vgetorpeek(int advance)
                     || (p_remap && typebuf.tb_noremap[
                           typebuf.tb_off] == RM_YES))
                 && !timedout) {
-              keylen = check_termcode(max_mlen + 1,
-                  NULL, 0, NULL);
-
-              /* If no termcode matched but 'pastetoggle'
-               * matched partially it's like an incomplete key
-               * sequence. */
-              if (keylen == 0 && save_keylen == KEYLEN_PART_KEY)
-                keylen = KEYLEN_PART_KEY;
-
-              /*
-               * When getting a partial match, but the last
-               * characters were not typed, don't wait for a
-               * typed character to complete the termcode.
-               * This helps a lot when a ":normal" command ends
-               * in an ESC.
-               */
-              if (keylen < 0
-                  && typebuf.tb_len == typebuf.tb_maplen)
-                keylen = 0;
+              keylen = 0;
             } else
               keylen = 0;
             if (keylen == 0) {                  /* no matching terminal code */
@@ -2515,29 +2477,27 @@ fix_input_buffer (
     int script                     /* TRUE when reading from a script */
 )
 {
-  if (abstract_ui) {
-    // Should not escape K_SPECIAL/CSI while in embedded mode because vim key
-    // codes keys are processed in input.c/input_enqueue.
+  if (!using_script()) {
+    // Should not escape K_SPECIAL/CSI reading input from the user because vim
+    // key codes keys are processed in input.c/input_enqueue.
     buf[len] = NUL;
     return len;
   }
 
+  // Reading from script, need to process special bytes
   int i;
   char_u      *p = buf;
 
-  /*
-   * Two characters are special: NUL and K_SPECIAL.
-   * When compiled With the GUI CSI is also special.
-   * Replace	     NUL by K_SPECIAL KS_ZERO	 KE_FILLER
-   * Replace K_SPECIAL by K_SPECIAL KS_SPECIAL KE_FILLER
-   * Replace       CSI by K_SPECIAL KS_EXTRA   KE_CSI
-   * Don't replace K_SPECIAL when reading a script file.
-   */
+  // Two characters are special: NUL and K_SPECIAL.
+  // Replace	     NUL by K_SPECIAL KS_ZERO	 KE_FILLER
+  // Replace K_SPECIAL by K_SPECIAL KS_SPECIAL KE_FILLER
+  // Replace       CSI by K_SPECIAL KS_EXTRA   KE_CSI
+  // Don't replace K_SPECIAL when reading a script file.
   for (i = len; --i >= 0; ++p) {
     if (p[0] == NUL
         || (p[0] == K_SPECIAL
           && !script
-          && (i < 2 || p[1] != KS_EXTRA || is_user_input(p[2])))) {
+          && (i < 2 || p[1] != KS_EXTRA))) {
       memmove(p + 3, p + 1, (size_t)i);
       p[2] = K_THIRD(p[0]);
       p[1] = K_SECOND(p[0]);
@@ -2546,7 +2506,7 @@ fix_input_buffer (
       len += 2;
     }
   }
-  *p = NUL;             /* add trailing NUL */
+  *p = NUL;  // add trailing NUL
   return len;
 }
 
@@ -3772,11 +3732,6 @@ eval_map_expr (
   return res;
 }
 
-static bool is_user_input(int k)
-{
-  return k != (int)KE_EVENT && k != (int)KE_CURSORHOLD;
-}
-
 /*
  * Copy "p" to allocated memory, escaping K_SPECIAL and CSI so that the result
  * can be put in the typeahead buffer.
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 1aa90777fa..86c28e823a 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -904,13 +904,10 @@ EXTERN char_u   *use_viminfo INIT(= NULL);  /* name of viminfo file to use */
 EXTERN FILE     *scriptin[NSCRIPT];         /* streams to read script from */
 EXTERN int curscript INIT(= 0);             /* index in scriptin[] */
 EXTERN FILE     *scriptout INIT(= NULL);    /* stream to write script to */
-EXTERN int read_cmd_fd INIT(= 0);           /* fd to read commands from */
 
 /* volatile because it is used in signal handler catch_sigint(). */
 EXTERN volatile int got_int INIT(= FALSE);    /* set to TRUE when interrupt
                                                  signal occurred */
-EXTERN int termcap_active INIT(= FALSE);        /* set by starttermcap() */
-EXTERN int cur_tmode INIT(= TMODE_COOK);        /* input terminal mode */
 EXTERN int bangredo INIT(= FALSE);          /* set to TRUE with ! command */
 EXTERN int searchcmdlen;                    /* length of previous search cmd */
 EXTERN int reg_do_extmatch INIT(= 0);       /* Used when compiling regexp:
@@ -1237,14 +1234,8 @@ EXTERN FILE *time_fd INIT(= NULL);  /* where to write startup timing */
 EXTERN int ignored;
 EXTERN char *ignoredp;
 
-/* Temporarily moved these static variables to assist in migrating from
- * os_unix.c */
-EXTERN int curr_tmode INIT(= TMODE_COOK); /* contains current terminal mode */
-
 // If a msgpack-rpc channel should be started over stdin/stdout
 EXTERN bool embedded_mode INIT(= false);
-// Using the "abstract_ui" termcap
-EXTERN bool abstract_ui INIT(= false);
 
 /// Used to track the status of external functions.
 /// Currently only used for iconv().
diff --git a/src/nvim/hardcopy.c b/src/nvim/hardcopy.c
index c01f763d20..2dbe33d6e2 100644
--- a/src/nvim/hardcopy.c
+++ b/src/nvim/hardcopy.c
@@ -617,10 +617,7 @@ void ex_hardcopy(exarg_T *eap)
           eap->forceit) == FAIL)
     return;
 
-  if (t_colors > 1)
-    settings.modec = 'c';
-  else
-    settings.modec = 't';
+  settings.modec = 'c';
 
   if (!syntax_present(curwin))
     settings.do_syntax = FALSE;
diff --git a/src/nvim/keymap.c b/src/nvim/keymap.c
index 251926c01a..8d98a0a95d 100644
--- a/src/nvim/keymap.c
+++ b/src/nvim/keymap.c
@@ -752,26 +752,3 @@ int get_mouse_button(int code, bool *is_click, bool *is_drag)
     }
   return 0;         /* Shouldn't get here */
 }
-
-/*
- * Return the appropriate pseudo mouse event token (KE_LEFTMOUSE etc) based on
- * the given information about which mouse button is down, and whether the
- * mouse was clicked, dragged or released.
- */
-int 
-get_pseudo_mouse_code (
-    int button,             /* eg MOUSE_LEFT */
-    int is_click,
-    int is_drag
-)
-{
-  int i;
-
-  for (i = 0; mouse_table[i].pseudo_code; i++)
-    if (button == mouse_table[i].button
-        && is_click == mouse_table[i].is_click
-        && is_drag == mouse_table[i].is_drag) {
-      return mouse_table[i].pseudo_code;
-    }
-  return (int)KE_IGNORE;            /* not recognized, ignore it */
-}
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 6e24806c56..f2891f0979 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -95,7 +95,12 @@ typedef struct {
   char_u      *use_ef;                  /* 'errorfile' from -q argument */
 
   int want_full_screen;
-  bool stdout_isatty;                   /* is stdout a terminal? */
+  bool input_isatty;                    // stdin is a terminal
+  bool output_isatty;                   // stdout is a terminal
+  bool err_isatty;                      // stderr is a terminal
+  bool headless;                        // Dont try to start an user interface
+                                        // or read/write to stdio(unless
+                                        // embedding)
   char_u      *term;                    /* specified terminal name */
   int no_swap_file;                     /* "-n" argument used */
   int use_debug_break_level;
@@ -197,9 +202,7 @@ int main(int argc, char **argv)
 
   early_init();
 
-  /*
-   * Check if we have an interactive window.
-   */
+  // Check if we have an interactive window.
   check_and_set_isatty(&params);
 
   /*
@@ -242,34 +245,20 @@ int main(int argc, char **argv)
     printf(_("%d files to edit\n"), GARGCOUNT);
 
   if (params.want_full_screen && !silent_mode) {
-    if (embedded_mode) {
-      // embedded mode implies abstract_ui
-      termcapinit((uint8_t *)"abstract_ui");
-    } else {
-      // set terminal name and get terminal capabilities (will set full_screen)
-      // Do some initialization of the screen
-      termcapinit(params.term);
-    }
+    termcapinit((uint8_t *)"abstract_ui");
     screen_start();             /* don't know where cursor is now */
     TIME_MSG("Termcap init");
   }
 
   event_init();
-
-  if (abstract_ui) {
-    full_screen = true;
-    t_colors = 256;
-    T_CCO = (uint8_t *)"256";
-  } else {
-    // Print a warning if stdout is not a terminal TODO(tarruda): Remove this
-    // check once the new terminal UI is implemented
-    check_tty(&params);
-  }
+  full_screen = true;
+  t_colors = 256;
+  T_CCO = (uint8_t *)"256";
+  check_tty(&params);
 
   /*
    * Set the default values for the options that use Rows and Columns.
    */
-  ui_get_shellsize();           /* inits Rows and Columns */
   win_init_size();
   /* Set the 'diff' option now, so that it can be checked for in a .vimrc
    * file.  There is no buffer yet though. */
@@ -382,25 +371,22 @@ int main(int argc, char **argv)
     newline_on_exit = TRUE;
 #endif
 
-  /*
-   * When done something that is not allowed or error message call
-   * wait_return.  This must be done before starttermcap(), because it may
-   * switch to another screen. It must be done after settmode(TMODE_RAW),
-   * because we want to react on a single key stroke.
-   * Call settmode and starttermcap here, so the T_KS and T_TI may be
-   * defined by termcapinit and redefined in .exrc.
-   */
-  settmode(TMODE_RAW);
-  TIME_MSG("setting raw mode");
+  if (!params.headless && (params.output_isatty || params.err_isatty)) {
+    if (params.input_isatty && (need_wait_return || msg_didany)) {
+      // Since at this point there's no UI instance running yet, error messages
+      // would have been printed to stdout. Before starting (which can result
+      // in a alternate screen buffer being shown) we need confirmation that
+      // the user has seen the messages and that is done with a call to
+      // wait_return. For that to work, stdin must be openend temporarily.
+      input_start_stdin();
+      wait_return(TRUE);
+      TIME_MSG("waiting for return");
+      input_stop_stdin();
+    }
 
-  if (need_wait_return || msg_didany) {
-    wait_return(TRUE);
-    TIME_MSG("waiting for return");
+    ui_builtin_start();
   }
 
-  starttermcap(); // start termcap if not done by wait_return()
-  TIME_MSG("start termcap");
-  may_req_ambiguous_char_width();
   setmouse();  // may start using the mouse
 
   if (scroll_region) {
@@ -480,10 +466,6 @@ int main(int argc, char **argv)
   no_wait_return = FALSE;
   starting = 0;
 
-  /* Requesting the termresponse is postponed until here, so that a "-c q"
-   * argument doesn't make it appear in the shell Vim was started from. */
-  may_req_termresponse();
-
   /* start in insert mode */
   if (p_im)
     need_start_insertmode = TRUE;
@@ -965,14 +947,14 @@ static void command_line_scan(mparm_T *parmp)
       c = argv[0][argv_idx++];
       switch (c) {
         case NUL:                 /* "vim -"  read from stdin */
-          /* "ex -" silent mode */
-          if (exmode_active)
+          if (exmode_active) {
+            // "ex -" silent mode
             silent_mode = TRUE;
-          else {
-            if (parmp->edit_type != EDIT_NONE)
+          } else {
+            if (parmp->edit_type != EDIT_NONE) {
               mainerr(ME_TOO_MANY_ARGS, argv[0]);
+            }
             parmp->