neovim

edit.c (129514B)

---

// edit.c: functions for Insert mode

#include <assert.h>
#include <ctype.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stddef.h>
#include <string.h>
#include <uv.h>

#include "klib/kvec.h"
#include "nvim/api/private/defs.h"
#include "nvim/ascii_defs.h"
#include "nvim/autocmd.h"
#include "nvim/autocmd_defs.h"
#include "nvim/buffer.h"
#include "nvim/buffer_defs.h"
#include "nvim/change.h"
#include "nvim/charset.h"
#include "nvim/cursor.h"
#include "nvim/decoration.h"
#include "nvim/digraph.h"
#include "nvim/drawscreen.h"
#include "nvim/edit.h"
#include "nvim/errors.h"
#include "nvim/eval.h"
#include "nvim/eval/typval_defs.h"
#include "nvim/eval/vars.h"
#include "nvim/ex_cmds_defs.h"
#include "nvim/ex_docmd.h"
#include "nvim/extmark.h"
#include "nvim/extmark_defs.h"
#include "nvim/fileio.h"
#include "nvim/fold.h"
#include "nvim/getchar.h"
#include "nvim/gettext_defs.h"
#include "nvim/globals.h"
#include "nvim/grid.h"
#include "nvim/grid_defs.h"
#include "nvim/highlight.h"
#include "nvim/highlight_defs.h"
#include "nvim/highlight_group.h"
#include "nvim/indent.h"
#include "nvim/indent_c.h"
#include "nvim/insexpand.h"
#include "nvim/keycodes.h"
#include "nvim/macros_defs.h"
#include "nvim/mapping.h"
#include "nvim/mark.h"
#include "nvim/mark_defs.h"
#include "nvim/marktree_defs.h"
#include "nvim/mbyte.h"
#include "nvim/mbyte_defs.h"
#include "nvim/memline.h"
#include "nvim/memline_defs.h"
#include "nvim/memory.h"
#include "nvim/message.h"
#include "nvim/mouse.h"
#include "nvim/move.h"
#include "nvim/normal.h"
#include "nvim/normal_defs.h"
#include "nvim/ops.h"
#include "nvim/option.h"
#include "nvim/option_vars.h"
#include "nvim/os/input.h"
#include "nvim/plines.h"
#include "nvim/popupmenu.h"
#include "nvim/pos_defs.h"
#include "nvim/register.h"
#include "nvim/search.h"
#include "nvim/state.h"
#include "nvim/state_defs.h"
#include "nvim/strings.h"
#include "nvim/syntax.h"
#include "nvim/terminal.h"
#include "nvim/textformat.h"
#include "nvim/textobject.h"
#include "nvim/types_defs.h"
#include "nvim/ui.h"
#include "nvim/ui_defs.h"
#include "nvim/undo.h"
#include "nvim/vim_defs.h"
#include "nvim/window.h"

typedef struct {
 VimState state;
 cmdarg_T *ca;
 int mincol;
 int cmdchar;
 int cmdchar_todo;                  // cmdchar to handle once in init_prompt
 bool ins_just_started;
 int startln;
 int count;
 int c;
 int lastc;
 int i;
 bool did_backspace;                // previous char was backspace
 bool line_is_white;                // line is empty before insert
 linenr_T old_topline;              // topline before insertion
 int old_topfill;
 int inserted_space;                // just inserted a space
 int replaceState;
 int did_restart_edit;              // remember if insert mode was restarted
                                    // after a ctrl+o
 bool nomove;
} InsertState;

#include "edit.c.generated.h"
enum {
 BACKSPACE_CHAR = 1,
 BACKSPACE_WORD = 2,
 BACKSPACE_WORD_NOT_SPACE = 3,
 BACKSPACE_LINE = 4,
};

/// Set when doing something for completion that may call edit() recursively,
/// which is not allowed.
static bool compl_busy = false;

static colnr_T Insstart_textlen;        // length of line when insert started
static colnr_T Insstart_blank_vcol;     // vcol for first inserted blank
static bool update_Insstart_orig = true;  // set Insstart_orig to Insstart

/// the text of the previous insert, K_SPECIAL is escaped
static String last_insert = STRING_INIT;
static int last_insert_skip;            // nr of chars in front of previous insert
static int new_insert_skip;             // nr of chars in front of current insert
static int did_restart_edit;            // "restart_edit" when calling edit()

static bool can_cindent;                // may do cindenting on this line

static bool revins_on;                  // reverse insert mode on
static int revins_chars;                // how much to skip after edit
static int revins_legal;                // was the last char 'legal'?
static int revins_scol;                 // start column of revins session

static bool ins_need_undo;              // call u_save() before inserting a
                                       // char.  Set when edit() is called.
                                       // after that arrow_used is used.

static TriState dont_sync_undo = kFalse;  // CTRL-G U prevents syncing undo
                                         // for the next left/right cursor key

static linenr_T o_lnum = 0;

static kvec_t(char) replace_stack = KV_INITIAL_VALUE;

#define TRIGGER_AUTOCOMPLETE() \
 do { \
   redraw_later(curwin, UPD_VALID); \
   update_screen();  /* Show char deletion immediately */ \
   ui_flush(); \
   ins_compl_enable_autocomplete(); \
   insert_do_complete(s); \
   break; \
 } while (0)

#define MAY_TRIGGER_AUTOCOMPLETE(c) \
 do { \
   if (ins_compl_has_autocomplete() && !char_avail() && curwin->w_cursor.col > 0) { \
     (c) = char_before_cursor(); \
     if (vim_isprintc(c)) { \
       TRIGGER_AUTOCOMPLETE(); \
     } \
   } \
 } while (0)

static void insert_enter(InsertState *s)
{
 s->did_backspace = true;
 s->old_topfill = -1;
 s->replaceState = MODE_REPLACE;
 s->cmdchar_todo = s->cmdchar;
 s->ins_just_started = true;
 // Remember whether editing was restarted after CTRL-O
 did_restart_edit = restart_edit;
 // sleep before redrawing, needed for "CTRL-O :" that results in an
 // error message
 msg_check_for_delay(true);
 // set Insstart_orig to Insstart
 update_Insstart_orig = true;

 ins_compl_clear();        // clear stuff for CTRL-X mode

 // Trigger InsertEnter autocommands.  Do not do this for "r<CR>" or "grx".
 if (s->cmdchar != 'r' && s->cmdchar != 'v') {
   pos_T save_cursor = curwin->w_cursor;

   const char *const ptr = s->cmdchar == 'R' ? "r" : s->cmdchar == 'V' ? "v" : "i";
   set_vim_var_string(VV_INSERTMODE, ptr, 1);
   set_vim_var_string(VV_CHAR, NULL, -1);
   ins_apply_autocmds(EVENT_INSERTENTER);

   // Check for changed highlighting, e.g. for ModeMsg.
   if (need_highlight_changed) {
     highlight_changed();
   }

   // Make sure the cursor didn't move.  Do call check_cursor_col() in
   // case the text was modified.  Since Insert mode was not started yet
   // a call to check_cursor_col() may move the cursor, especially with
   // the "A" command, thus set State to avoid that. Also check that the
   // line number is still valid (lines may have been deleted).
   // Do not restore if v:char was set to a non-empty string.
   if (!equalpos(curwin->w_cursor, save_cursor)
       && *get_vim_var_str(VV_CHAR) == NUL
       && save_cursor.lnum <= curbuf->b_ml.ml_line_count) {
     int save_state = State;

     curwin->w_cursor = save_cursor;
     State = MODE_INSERT;
     check_cursor_col(curwin);
     State = save_state;
   }
 }

 // When doing a paste with the middle mouse button, Insstart is set to
 // where the paste started.
 if (where_paste_started.lnum != 0) {
   Insstart = where_paste_started;
 } else {
   Insstart = curwin->w_cursor;
   if (s->startln) {
     Insstart.col = 0;
   }
 }

 Insstart_textlen = linetabsize_str(get_cursor_line_ptr());
 Insstart_blank_vcol = MAXCOL;

 if (!did_ai) {
   ai_col = 0;
 }

 if (s->cmdchar != NUL && restart_edit == 0) {
   ResetRedobuff();
   AppendNumberToRedobuff(s->count);
   if (s->cmdchar == 'V' || s->cmdchar == 'v') {
     // "gR" or "gr" command
     AppendCharToRedobuff('g');
     AppendCharToRedobuff((s->cmdchar == 'v') ? 'r' : 'R');
   } else {
     AppendCharToRedobuff(s->cmdchar);
     if (s->cmdchar == 'g') {          // "gI" command
       AppendCharToRedobuff('I');
     } else if (s->cmdchar == 'r') {  // "r<CR>" command
       s->count = 1;                  // insert only one <CR>
     }
   }
 }

 if (s->cmdchar == 'R') {
   State = MODE_REPLACE;
 } else if (s->cmdchar == 'V' || s->cmdchar == 'v') {
   State = MODE_VREPLACE;
   s->replaceState = MODE_VREPLACE;
   orig_line_count = curbuf->b_ml.ml_line_count;
   vr_lines_changed = 1;
 } else {
   State = MODE_INSERT;
 }

 may_trigger_modechanged();
 stop_insert_mode = false;

 // need to position cursor again when on a TAB and
 // when on a char with inline virtual text
 if (gchar_cursor() == TAB || buf_meta_total(curbuf, kMTMetaInline) > 0) {
   curwin->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL);
 }

 // Enable langmap or IME, indicated by 'iminsert'.
 // Note that IME may enabled/disabled without us noticing here, thus the
 // 'iminsert' value may not reflect what is actually used.  It is updated
 // when hitting <Esc>.
 if (curbuf->b_p_iminsert == B_IMODE_LMAP) {
   State |= MODE_LANGMAP;
 }

 setmouse();
 clear_showcmd();
 // there is no reverse replace mode
 revins_on = (State == MODE_INSERT && p_ri);
 if (revins_on) {
   undisplay_dollar();
 }
 revins_chars = 0;
 revins_legal = 0;
 revins_scol = -1;

 // Handle restarting Insert mode.
 // Don't do this for "CTRL-O ." (repeat an insert): we get here with
 // restart_edit non-zero, and something in the stuff buffer.
 if (restart_edit != 0 && stuff_empty()) {
   // After a paste we consider text typed to be part of the insert for
   // the pasted text. You can backspace over the pasted text too.
   arrow_used = where_paste_started.lnum == 0;
   restart_edit = 0;

   // If the cursor was after the end-of-line before the CTRL-O and it is
   // now at the end-of-line, put it after the end-of-line (this is not
   // correct in very rare cases).
   // Also do this if curswant is greater than the current virtual
   // column.  Eg after "^O$" or "^O80|".
   validate_virtcol(curwin);
   update_curswant();
   const char *ptr;
   if (((ins_at_eol && curwin->w_cursor.lnum == o_lnum)
        || curwin->w_curswant > curwin->w_virtcol)
       && *(ptr = get_cursor_line_ptr() + curwin->w_cursor.col) != NUL) {
     if (ptr[1] == NUL) {
       curwin->w_cursor.col++;
     } else {
       s->i = utfc_ptr2len(ptr);
       if (ptr[s->i] == NUL) {
         curwin->w_cursor.col += s->i;
       }
     }
   }
   ins_at_eol = false;
 } else {
   arrow_used = false;
 }

 // we are in insert mode now, don't need to start it anymore
 need_start_insertmode = false;

 // Need to save the line for undo before inserting the first char.
 ins_need_undo = true;

 where_paste_started.lnum = 0;
 can_cindent = true;
 // The cursor line is not in a closed fold, unless restarting.
 if (did_restart_edit == 0) {
   foldOpenCursor();
 }

 // If 'showmode' is set, show the current (insert/replace/..) mode.
 // A warning message for changing a readonly file is given here, before
 // actually changing anything.  It's put after the mode, if any.
 s->i = 0;
 if (p_smd && msg_silent == 0) {
   s->i = showmode();
 }

 if (did_restart_edit == 0) {
   change_warning(curbuf, s->i == 0 ? 0 : s->i + 1);
 }

 ui_cursor_shape();            // may show different cursor shape
 do_digraph(-1);               // clear digraphs

 // Get the current length of the redo buffer, those characters have to be
 // skipped if we want to get to the inserted characters.
 String inserted = get_inserted();
 new_insert_skip = (int)inserted.size;
 if (inserted.data != NULL) {
   xfree(inserted.data);
 }

 old_indent = 0;

 do {
   state_enter(&s->state);
   // If s->count != 0, `ins_esc` will prepare the redo buffer for reprocessing
   // and return false, causing `state_enter` to be called again.
 } while (!ins_esc(&s->count, s->cmdchar, s->nomove));

 // Always update o_lnum, so that a "CTRL-O ." that adds a line
 // still puts the cursor back after the inserted text.
 if (ins_at_eol) {
   o_lnum = curwin->w_cursor.lnum;
 }

 pum_check_clear();

 foldUpdateAfterInsert();
 // When CTRL-C was typed got_int will be set, with the result
 // that the autocommands won't be executed. When mapped got_int
 // is not set, but let's keep the behavior the same.
 if (s->cmdchar != 'r' && s->cmdchar != 'v' && s->c != Ctrl_C) {
   ins_apply_autocmds(EVENT_INSERTLEAVE);
 }
 did_cursorhold = false;

 // ins_redraw() triggers TextChangedI only when no characters
 // are in the typeahead buffer, so reset curbuf->b_last_changedtick
 // if the TextChangedI was not blocked by char_avail() (e.g. using :norm!)
 // and the TextChangedI autocommand has been triggered.
 if (!char_avail() && curbuf->b_last_changedtick_i == buf_get_changedtick(curbuf)) {
   curbuf->b_last_changedtick = buf_get_changedtick(curbuf);
 }
}

static int insert_check(VimState *state)
{
 InsertState *s = (InsertState *)state;

 if (!revins_legal) {
   revins_scol = -1;     // reset on illegal motions
 } else {
   revins_legal = 0;
 }

 if (arrow_used) {       // don't repeat insert when arrow key used
   s->count = 0;
 }

 if (update_Insstart_orig) {
   Insstart_orig = Insstart;
 }

 if (curbuf->terminal && !stop_insert_mode) {
   // Exit Insert mode and go to Terminal mode.
   stop_insert_mode = true;
   restart_edit = 'I';
   stuffcharReadbuff(K_NOP);
 }

 if (stop_insert_mode && !ins_compl_active()) {
   // ":stopinsert" used
   s->count = 0;
   return 0;  // exit insert mode
 }

 // set curwin->w_curswant for next K_DOWN or K_UP
 if (!arrow_used) {
   curwin->w_set_curswant = true;
 }

 // If there is no typeahead may check for timestamps (e.g., for when a
 // menu invoked a shell command).
 if (stuff_empty()) {
   did_check_timestamps = false;
   if (need_check_timestamps) {
     check_timestamps(false);
   }
 }

 // When emsg() was called msg_scroll will have been set.
 msg_scroll = false;

 // Open fold at the cursor line, according to 'foldopen'.
 if (fdo_flags & kOptFdoFlagInsert) {
   foldOpenCursor();
 }

 // Close folds where the cursor isn't, according to 'foldclose'
 if (!char_avail()) {
   foldCheckClose();
 }

 if (bt_prompt(curbuf)) {
   init_prompt(s->cmdchar_todo);
   s->cmdchar_todo = NUL;
 }

 // If we inserted a character at the last position of the last line in the
 // window, scroll the window one line up. This avoids an extra redraw.  This
 // is detected when the cursor column is smaller after inserting something.
 // Don't do this when the topline changed already, it has already been
 // adjusted (by insertchar() calling open_line())).
 // Also don't do this when 'smoothscroll' is set, as the window should then
 // be scrolled by screen lines.
 if (curbuf->b_mod_set
     && curwin->w_p_wrap
     && !curwin->w_p_sms
     && !s->did_backspace
     && curwin->w_topline == s->old_topline
     && curwin->w_topfill == s->old_topfill
     && s->count <= 1) {
   s->mincol = curwin->w_wcol;
   validate_cursor_col(curwin);

   if (curwin->w_wcol < s->mincol - tabstop_at(get_nolist_virtcol(),
                                               curbuf->b_p_ts,
                                               curbuf->b_p_vts_array,
                                               false)
       && curwin->w_wrow == curwin->w_view_height - 1 - get_scrolloff_value(curwin)
       && (curwin->w_cursor.lnum != curwin->w_topline
           || curwin->w_topfill > 0)) {
     if (curwin->w_topfill > 0) {
       curwin->w_topfill--;
     } else if (hasFolding(curwin, curwin->w_topline, NULL, &s->old_topline)) {
       set_topline(curwin, s->old_topline + 1);
     } else {
       set_topline(curwin, curwin->w_topline + 1);
     }
   }
 }

 // May need to adjust w_topline to show the cursor.
 if (s->count <= 1) {
   update_topline(curwin);
 }

 s->did_backspace = false;

 if (s->count <= 1) {
   validate_cursor(curwin);  // may set must_redraw
 }

 // Redraw the display when no characters are waiting.
 // Also shows mode, ruler and positions cursor.
 ins_redraw(true);

 if (curwin->w_p_scb) {
   do_check_scrollbind(true);
 }

 if (curwin->w_p_crb) {
   do_check_cursorbind();
 }

 if (s->count <= 1) {
   update_curswant();
 }
 s->old_topline = curwin->w_topline;
 s->old_topfill = curwin->w_topfill;

 if (s->c != K_EVENT) {
   s->lastc = s->c;  // remember previous char for CTRL-D
 }

 // After using CTRL-G U the next cursor key will not break undo.
 if (dont_sync_undo == kNone) {
   dont_sync_undo = kTrue;
 } else {
   dont_sync_undo = kFalse;
 }

 // Trigger autocomplete when entering Insert mode, either directly
 // or via change commands like 'ciw', 'cw', etc., before the first
 // character is typed.
 if (s->ins_just_started) {
   s->ins_just_started = false;
   if (ins_compl_has_autocomplete() && !char_avail() && curwin->w_cursor.col > 0) {
     s->c = char_before_cursor();
     if (vim_isprintc(s->c)) {
       ins_compl_enable_autocomplete();
       ins_compl_init_get_longest();
       insert_do_complete(s);
       insert_handle_key_post(s);
       return 1;
     }
   }
 }

 return 1;
}

static int insert_execute(VimState *state, int key)
{
 InsertState *const s = (InsertState *)state;
 if (stop_insert_mode) {
   // Insert mode ended, possibly from a callback.
   if (key != K_IGNORE && key != K_NOP) {
     vungetc(key);
   }
   s->count = 0;
   s->nomove = true;
   ins_compl_prep(ESC);
   return 0;
 }

 if (key == K_IGNORE || key == K_NOP) {
   return -1;  // get another key
 }
 s->c = key;

 // Don't want K_EVENT with cursorhold for the second key, e.g., after CTRL-V.
 if (key != K_EVENT) {
   did_cursorhold = true;
 }

 // Special handling of keys while the popup menu is visible or wanted
 // and the cursor is still in the completed word.  Only when there is
 // a match, skip this when no matches were found.
 if (ins_compl_active() && curwin->w_cursor.col >= ins_compl_col()
     && ins_compl_has_shown_match() && pum_wanted()) {
   // BS: Delete one character from "compl_leader".
   if ((s->c == K_BS || s->c == Ctrl_H)
       && curwin->w_cursor.col > ins_compl_col()
       && (s->c = ins_compl_bs()) == NUL) {
     return 1;  // continue
   }

   // When no match was selected or it was edited.
   if (!ins_compl_used_match()) {
     // CTRL-L: Add one character from the current match to
     // "compl_leader".  Except when at the original match and
     // there is nothing to add, CTRL-L works like CTRL-P then.
     if (s->c == Ctrl_L
         && (!ctrl_x_mode_line_or_eval()
             || ins_compl_long_shown_match())) {
       ins_compl_addfrommatch();
       return 1;  // continue
     }

     // A non-white character that fits in with the current
     // completion: Add to "compl_leader".
     if (ins_compl_accept_char(s->c)) {
       // Trigger InsertCharPre.
       char *str = do_insert_char_pre(s->c);

       if (str != NULL) {
         for (char *p = str; *p != NUL; MB_PTR_ADV(p)) {
           ins_compl_addleader(utf_ptr2char(p));
         }
         xfree(str);
       } else {
         ins_compl_addleader(s->c);
       }
       return 1;  // continue
     }

     // Pressing CTRL-Y selects the current match.  When
     // compl_enter_selects is set the Enter key does the same.
     if ((s->c == Ctrl_Y
          || (ins_compl_enter_selects()
              && (s->c == CAR || s->c == K_KENTER || s->c == NL)))
         && stop_arrow() == OK) {
       ins_compl_delete(false);
       if (ins_compl_preinsert_longest() && !ins_compl_is_match_selected()) {
         ins_compl_insert(false, true);
         ins_compl_init_get_longest();
         return 1;  // continue
       } else {
         ins_compl_insert(false, false);
       }
     } else if (ascii_iswhite_nl_or_nul(s->c) && ins_compl_preinsert_effect()) {
       // Delete preinserted text when typing special chars
       ins_compl_delete(false);
     }
   }
 }

 // Prepare for or stop CTRL-X mode. This doesn't do completion, but it does
 // fix up the text when finishing completion.
 ins_compl_init_get_longest();
 if (ins_compl_prep(s->c)) {
   return 1;  // continue
 }

 // CTRL-\ CTRL-N goes to Normal mode,
 // CTRL-\ CTRL-O is like CTRL-O but without moving the cursor
 if (s->c == Ctrl_BSL) {
   // may need to redraw when no more chars available now
   ins_redraw(false);
   no_mapping++;
   allow_keys++;
   s->c = plain_vgetc();
   no_mapping--;
   allow_keys--;
   if (s->c != Ctrl_N && s->c != Ctrl_G && s->c != Ctrl_O) {
     // it's something else
     vungetc(s->c);
     s->c = Ctrl_BSL;
   } else {
     if (s->c == Ctrl_O) {
       ins_ctrl_o();
       ins_at_eol = false;  // cursor keeps its column
       s->nomove = true;
     }
     s->count = 0;
     return 0;
   }
 }

 if (s->c != K_EVENT) {
   s->c = do_digraph(s->c);
 }

 if ((s->c == Ctrl_V || s->c == Ctrl_Q) && ctrl_x_mode_cmdline()) {
   insert_do_complete(s);
   insert_handle_key_post(s);
   return 1;
 }

 if (s->c == Ctrl_V || s->c == Ctrl_Q) {
   ins_ctrl_v();
   s->c = Ctrl_V;       // pretend CTRL-V is last typed character
   return 1;  // continue
 }

 if (cindent_on() && ctrl_x_mode_none()) {
   s->line_is_white = inindent(0);
   // A key name preceded by a bang means this key is not to be
   // inserted.  Skip ahead to the re-indenting below.
   if (in_cinkeys(s->c, '!', s->line_is_white)
       && stop_arrow() == OK) {
     do_c_expr_indent();
     return 1;  // continue
   }
   // A key name preceded by a star means that indenting has to be
   // done before inserting the key.
   if (can_cindent && in_cinkeys(s->c, '*', s->line_is_white)
       && stop_arrow() == OK) {
     do_c_expr_indent();
   }
 }

 if (curwin->w_p_rl) {
   switch (s->c) {
   case K_LEFT:
     s->c = K_RIGHT; break;
   case K_S_LEFT:
     s->c = K_S_RIGHT; break;
   case K_C_LEFT:
     s->c = K_C_RIGHT; break;
   case K_RIGHT:
     s->c = K_LEFT; break;
   case K_S_RIGHT:
     s->c = K_S_LEFT; break;
   case K_C_RIGHT:
     s->c = K_C_LEFT; break;
   }
 }

 // If 'keymodel' contains "startsel", may start selection.  If it
 // does, a CTRL-O and c will be stuffed, we need to get these
 // characters.
 if (ins_start_select(s->c)) {
   return 1;  // continue
 }

 return insert_handle_key(s);
}

static int insert_handle_key(InsertState *s)
{
 // The big switch to handle a character in insert mode.
 // TODO(tarruda): This could look better if a lookup table is used.
 // (similar to normal mode `nv_cmds[]`)
 switch (s->c) {
 case ESC:           // End input mode
   if (echeck_abbr(ESC + ABBR_OFF)) {
     break;
   }
   FALLTHROUGH;

 case Ctrl_C:        // End input mode
   if (s->c == Ctrl_C && cmdwin_type != 0) {
     // Close the cmdline window.
     cmdwin_result = K_IGNORE;
     got_int = false;         // don't stop executing autocommands et al
     s->nomove = true;
     return 0;  // exit insert mode
   }
   if (s->c == Ctrl_C && bt_prompt(curbuf)) {
     if (invoke_prompt_interrupt()) {
       if (!bt_prompt(curbuf)) {
         // buffer changed to a non-prompt buffer, get out of
         // Insert mode
         return 0;
       }
       break;
     }
   }

   return 0;  // exit insert mode

 case Ctrl_Z:
   goto normalchar;                // insert CTRL-Z as normal char

 case Ctrl_O:        // execute one command
   if (ctrl_x_mode_omni()) {
     insert_do_complete(s);
     break;
   }

   if (echeck_abbr(Ctrl_O + ABBR_OFF)) {
     break;
   }

   ins_ctrl_o();

   // don't move the cursor left when 'virtualedit' has "onemore".
   if (get_ve_flags(curwin) & kOptVeFlagOnemore) {
     ins_at_eol = false;
     s->nomove = true;
   }

   s->count = 0;
   return 0;  // exit insert mode

 case K_INS:         // toggle insert/replace mode
 case K_KINS:
   ins_insert(s->replaceState);
   break;

 case K_SELECT:      // end of Select mode mapping - ignore
   break;

 case K_HELP:        // Help key works like <ESC> <Help>
 case K_F1:
 case K_XF1:
   stuffcharReadbuff(K_HELP);
   return 0;  // exit insert mode

 case ' ':
   if (mod_mask != MOD_MASK_CTRL) {
     goto normalchar;
   }
   FALLTHROUGH;
 case K_ZERO:        // Insert the previously inserted text.
 case NUL:
 case Ctrl_A:
   // For ^@ the trailing ESC will end the insert, unless there is an
   // error.
   if (stuff_inserted(NUL, 1, (s->c == Ctrl_A)) == FAIL
       && s->c != Ctrl_A) {
     return 0;  // exit insert mode
   }
   s->inserted_space = false;
   break;

 case Ctrl_R:        // insert the contents of a register
   if (ctrl_x_mode_register() && !ins_compl_active()) {
     insert_do_complete(s);
     break;
   }
   ins_reg();
   auto_format(false, true);
   s->inserted_space = false;
   break;

 case Ctrl_G:        // commands starting with CTRL-G
   ins_ctrl_g();
   break;

 case Ctrl_HAT:      // switch input mode and/or langmap
   ins_ctrl_hat();
   break;

 case Ctrl__:        // switch between languages
   if (!p_ari) {
     goto normalchar;
   }
   ins_ctrl_();
   break;

 case Ctrl_D:        // Make indent one shiftwidth smaller.
   if (ctrl_x_mode_path_defines()) {
     insert_do_complete(s);
     break;
   }
   FALLTHROUGH;

 case Ctrl_T:        // Make indent one shiftwidth greater.
   if (s->c == Ctrl_T && ctrl_x_mode_thesaurus()) {
     if (check_compl_option(false)) {
       insert_do_complete(s);
     }
     break;
   }
   ins_shift(s->c, s->lastc);
   auto_format(false, true);
   s->inserted_space = false;
   break;

 case K_DEL:         // delete character under the cursor
 case K_KDEL:
   ins_del();
   auto_format(false, true);
   break;

 case K_BS:          // delete character before the cursor
 case Ctrl_H:
   s->did_backspace = ins_bs(s->c, BACKSPACE_CHAR, &s->inserted_space);
   auto_format(false, true);
   if (s->did_backspace) {
     MAY_TRIGGER_AUTOCOMPLETE(s->c);
   }
   break;

 case Ctrl_W:        // delete word before the cursor
   if (bt_prompt(curbuf) && (mod_mask & MOD_MASK_SHIFT) == 0) {
     // In a prompt window CTRL-W is used for window commands.
     // Use Shift-CTRL-W to delete a word.
     stuffcharReadbuff(Ctrl_W);
     restart_edit = 'A';
     s->nomove = true;
     s->count = 0;
     return 0;
   }
   s->did_backspace = ins_bs(s->c, BACKSPACE_WORD, &s->inserted_space);
   auto_format(false, true);
   if (s->did_backspace) {
     MAY_TRIGGER_AUTOCOMPLETE(s->c);
   }
   break;

 case Ctrl_U:        // delete all inserted text in current line
   // CTRL-X CTRL-U completes with 'completefunc'.
   if (ctrl_x_mode_function()) {
     insert_do_complete(s);
   } else {
     s->did_backspace = ins_bs(s->c, BACKSPACE_LINE, &s->inserted_space);
     auto_format(false, true);
     s->inserted_space = false;
     if (s->did_backspace) {
       MAY_TRIGGER_AUTOCOMPLETE(s->c);
     }
   }
   break;

 case K_LEFTMOUSE:     // mouse keys
 case K_LEFTMOUSE_NM:
 case K_LEFTDRAG:
 case K_LEFTRELEASE:
 case K_LEFTRELEASE_NM:
 case K_MOUSEMOVE:
 case K_MIDDLEMOUSE:
 case K_MIDDLEDRAG:
 case K_MIDDLERELEASE:
 case K_RIGHTMOUSE:
 case K_RIGHTDRAG:
 case K_RIGHTRELEASE:
 case K_X1MOUSE:
 case K_X1DRAG:
 case K_X1RELEASE:
 case K_X2MOUSE:
 case K_X2DRAG:
 case K_X2RELEASE:
   ins_mouse(s->c);
   break;

 case K_MOUSEDOWN:   // Default action for scroll wheel up: scroll up
   ins_mousescroll(MSCR_DOWN);
   break;

 case K_MOUSEUP:     // Default action for scroll wheel down: scroll down
   ins_mousescroll(MSCR_UP);
   break;

 case K_MOUSELEFT:   // Scroll wheel left
   ins_mousescroll(MSCR_LEFT);
   break;

 case K_MOUSERIGHT:  // Scroll wheel right
   ins_mousescroll(MSCR_RIGHT);
   break;

 case K_IGNORE:      // Something mapped to nothing
   break;

 case K_PASTE_START:
   paste_repeat(1);
   goto check_pum;

 case K_EVENT:       // some event
   state_handle_k_event();
   // If CTRL-G U was used apply it to the next typed key.
   if (dont_sync_undo == kTrue) {
     dont_sync_undo = kNone;
   }
   goto check_pum;

 case K_COMMAND:     // <Cmd>command<CR>
   do_cmdline(NULL, getcmdkeycmd, NULL, 0);
   goto check_pum;

 case K_LUA:
   map_execute_lua(false, false);

check_pum:
   // nvim_select_popupmenu_item() can be called from the handling of
   // K_EVENT, K_COMMAND, or K_LUA.
   // TODO(bfredl): Not entirely sure this indirection is necessary
   // but doing like this ensures using nvim_select_popupmenu_item is
   // equivalent to selecting the item with a typed key.
   if (pum_want.active) {
     if (pum_visible()) {
       // Set this to NULL so that ins_complete() will update the message.
       edit_submode_extra = NULL;
       insert_do_complete(s);
       if (pum_want.finish) {
         // accept the item and stop completion
         ins_compl_prep(Ctrl_Y);
       }
     }
     pum_want.active = false;
   }

   if (curbuf->b_u_synced) {
     // The K_EVENT, K_COMMAND, or K_LUA caused undo to be synced.
     // Need to save the line for undo before inserting the next char.
     ins_need_undo = true;
   }
   break;

 case K_HOME:        // <Home>
 case K_KHOME:
 case K_S_HOME:
 case K_C_HOME:
   ins_home(s->c);
   break;

 case K_END:         // <End>
 case K_KEND:
 case K_S_END:
 case K_C_END:
   ins_end(s->c);
   break;

 case K_LEFT:        // <Left>
   if (mod_mask & (MOD_MASK_SHIFT|MOD_MASK_CTRL)) {
     ins_s_left();
   } else {
     ins_left();
   }
   break;

 case K_S_LEFT:      // <S-Left>
 case K_C_LEFT:
   ins_s_left();
   break;

 case K_RIGHT:       // <Right>
   if (mod_mask & (MOD_MASK_SHIFT|MOD_MASK_CTRL)) {
     ins_s_right();
   } else {
     ins_right();
   }
   break;

 case K_S_RIGHT:     // <S-Right>
 case K_C_RIGHT:
   ins_s_right();
   break;

 case K_UP:          // <Up>
   if (pum_visible()) {
     insert_do_complete(s);
   } else if (mod_mask & MOD_MASK_SHIFT) {
     ins_pageup();
   } else {
     ins_up(false);
   }
   break;

 case K_S_UP:        // <S-Up>
 case K_PAGEUP:
 case K_KPAGEUP:
   if (pum_visible()) {
     insert_do_complete(s);
   } else {
     ins_pageup();
   }
   break;

 case K_DOWN:        // <Down>
   if (pum_visible()) {
     insert_do_complete(s);
   } else if (mod_mask & MOD_MASK_SHIFT) {
     ins_pagedown();
   } else {
     ins_down(false);
   }
   break;

 case K_S_DOWN:      // <S-Down>
 case K_PAGEDOWN:
 case K_KPAGEDOWN:
   if (pum_visible()) {
     insert_do_complete(s);
   } else {
     ins_pagedown();
   }
   break;

 case K_S_TAB:       // When not mapped, use like a normal TAB
   s->c = TAB;
   FALLTHROUGH;

 case TAB:           // TAB or Complete patterns along path
   if (ctrl_x_mode_path_patterns()) {
     insert_do_complete(s);
     break;
   }
   s->inserted_space = false;
   if (ins_tab()) {
     goto normalchar;                // insert TAB as a normal char
   }
   auto_format(false, true);
   break;

 case K_KENTER:      // <Enter>
   s->c = CAR;
   FALLTHROUGH;
 case CAR:
 case NL:
   // In a quickfix window a <CR> jumps to the error under the
   // cursor.
   if (bt_quickfix(curbuf) && s->c == CAR) {
     if (curwin->w_llist_ref == NULL) {          // quickfix window
       do_cmdline_cmd(".cc");
     } else {                                    // location list window
       do_cmdline_cmd(".ll");
     }
     break;
   }
   if (cmdwin_type != 0) {
     // Execute the command in the cmdline window.
     cmdwin_result = CAR;
     return 0;
   }
   if ((mod_mask & MOD_MASK_SHIFT) == 0 && bt_prompt(curbuf)) {
     prompt_invoke_callback();
     if (!bt_prompt(curbuf)) {
       // buffer changed to a non-prompt buffer, get out of
       // Insert mode
       return 0;
     }
     break;
   }
   if (!ins_eol(s->c)) {
     return 0;  // out of memory
   }
   auto_format(false, false);
   s->inserted_space = false;
   break;

 case Ctrl_K:        // digraph or keyword completion
   if (ctrl_x_mode_dictionary()) {
     if (check_compl_option(true)) {
       insert_do_complete(s);
     }
     break;
   }

   s->c = ins_digraph();
   if (s->c == NUL) {
     break;
   }
   goto normalchar;

 case Ctrl_X:        // Enter CTRL-X mode
   ins_ctrl_x();
   break;

 case Ctrl_RSB:      // Tag name completion after ^X
   if (!ctrl_x_mode_tags()) {
     goto normalchar;
   } else {
     insert_do_complete(s);
   }
   break;

 case Ctrl_F:        // File name completion after ^X
   if (!ctrl_x_mode_files()) {
     goto normalchar;
   } else {
     insert_do_complete(s);
   }
   break;

 case 's':           // Spelling completion after ^X
 case Ctrl_S:
   if (!ctrl_x_mode_spell()) {
     goto normalchar;
   } else {
     insert_do_complete(s);
   }
   break;

 case Ctrl_L:        // Whole line completion after ^X
   if (!ctrl_x_mode_whole_line()) {
     goto normalchar;
   }
   FALLTHROUGH;

 case Ctrl_P:        // Do previous/next pattern completion
 case Ctrl_N:
   // if 'complete' is empty then plain ^P is no longer special,
   // but it is under other ^X modes
   if (*curbuf->b_p_cpt == NUL
       && (ctrl_x_mode_normal() || ctrl_x_mode_whole_line())
       && !compl_status_local()) {
     goto normalchar;
   }

   insert_do_complete(s);
   break;

 case Ctrl_Y:        // copy from previous line or scroll down
 case Ctrl_E:        // copy from next line or scroll up
   s->c = ins_ctrl_ey(s->c);
   break;

 default:

normalchar:
   // Insert a normal character.

   if (!p_paste) {
     // Trigger InsertCharPre.
     char *str = do_insert_char_pre(s->c);

     if (str != NULL) {
       if (*str != NUL && stop_arrow() != FAIL) {
         // Insert the new value of v:char literally.
         for (char *p = str; *p != NUL; MB_PTR_ADV(p)) {
           s->c = utf_ptr2char(p);
           if (s->c == CAR || s->c == K_KENTER || s->c == NL) {
             ins_eol(s->c);
           } else {
             ins_char(s->c);
           }
         }
         AppendToRedobuffLit(str, -1);
       }
       xfree(str);
       s->c = NUL;
     }

     // If the new value is already inserted or an empty string
     // then don't insert any character.
     if (s->c == NUL) {
       break;
     }
   }
   // Try to perform smart-indenting.
   ins_try_si(s->c);

   if (s->c == ' ') {
     s->inserted_space = true;
     if (inindent(0)) {
       can_cindent = false;
     }
     if (Insstart_blank_vcol == MAXCOL
         && curwin->w_cursor.lnum == Insstart.lnum) {
       Insstart_blank_vcol = get_nolist_virtcol();
     }
   }

   // Insert a normal character and check for abbreviations on a
   // special character.  Let CTRL-] expand abbreviations without
   // inserting it.
   if (vim_iswordc(s->c)
       // Add ABBR_OFF for characters above 0x100, this is
       // what check_abbr() expects.
       || (!echeck_abbr((s->c >= 0x100) ? (s->c + ABBR_OFF) : s->c)
           && s->c != Ctrl_RSB)) {
     insert_special(s->c, false, false);
     revins_legal++;
     revins_chars++;
   }

   auto_format(false, true);

   // When inserting a character the cursor line must never be in a
   // closed fold.
   foldOpenCursor();
   // Trigger autocompletion
   if (ins_compl_has_autocomplete() && !char_avail() && vim_isprintc(s->c)) {
     TRIGGER_AUTOCOMPLETE();
   }

   break;
 }       // end of switch (s->c)

 insert_handle_key_post(s);
 return 1;  // continue
}

static void insert_do_complete(InsertState *s)
{
 compl_busy = true;
 disable_fold_update++;  // don't redraw folds here
 if (ins_complete(s->c, true) == FAIL) {
   compl_status_clear();
 }
 disable_fold_update--;
 compl_busy = false;
 can_si = may_do_si();  // allow smartindenting
}

static void insert_do_cindent(InsertState *s)
{
 // Indent now if a key was typed that is in 'cinkeys'.
 if (in_cinkeys(s->c, ' ', s->line_is_white)) {
   if (stop_arrow() == OK) {
     // re-indent the current line
     do_c_expr_indent();
   }
 }
}

static void insert_handle_key_post(InsertState *s)
{
 // If typed something may trigger CursorHoldI again.
 if (s->c != K_EVENT
     // but not in CTRL-X mode, a script can't restore the state
     && ctrl_x_mode_normal()) {
   did_cursorhold = false;
 }

 // Check if we need to cancel completion mode because the window
 // or tab page was changed
 if (ins_compl_active() && !ins_compl_win_active(curwin)) {
   ins_compl_cancel();
 }

 // If the cursor was moved we didn't just insert a space
 if (arrow_used) {
   s->inserted_space = false;
 }

 if (can_cindent && cindent_on() && ctrl_x_mode_normal()) {
   insert_do_cindent(s);
 }
}

/// edit(): Start inserting text.
///
/// "cmdchar" can be:
/// 'i' normal insert command
/// 'a' normal append command
/// 'R' replace command
/// 'r' "r<CR>" command: insert one <CR>.
///     Note: count can be > 1, for redo, but still only one <CR> is inserted.
///           <Esc> is not used for redo.
/// 'g' "gI" command.
/// 'V' "gR" command for Virtual Replace mode.
/// 'v' "gr" command for single character Virtual Replace mode.
///
/// This function is not called recursively.  For CTRL-O commands, it returns
/// and lets the caller handle the Normal-mode command.
///
/// @param  cmdchar  command that started the insert
/// @param  startln  if true, insert at start of line
/// @param  count    repeat count for the command
///
/// @return true if a CTRL-O command caused the return (insert mode pending).
bool edit(int cmdchar, bool startln, int count)
{
 if (curbuf->terminal) {
   if (ex_normal_busy) {
     // Do not enter terminal mode from ex_normal(), which would cause havoc
     // (such as terminal-mode recursiveness). Instead set a flag to force-set
     // the value of `restart_edit` before `ex_normal` returns.
     restart_edit = 'i';
     force_restart_edit = true;
     return false;
   }
   return terminal_enter();
 }

 // Don't allow inserting in the sandbox.
 if (sandbox != 0) {
   emsg(_(e_sandbox));
   return false;
 }

 // Don't allow changes in the buffer while editing the cmdline.  The
 // caller of getcmdline() may get confused.
 // Don't allow recursive insert mode when busy with completion.
 // Allow in dummy buffers since they are only used internally
 if (textlock != 0 || ins_compl_active() || compl_busy || pum_visible()
     || expr_map_locked()) {
   emsg(_(e_textlock));
   return false;
 }

 InsertState s[1];
 memset(s, 0, sizeof(InsertState));
 s->state.execute = insert_execute;
 s->state.check = insert_check;
 s->cmdchar = cmdchar;
 s->startln = startln;
 s->count = count;
 insert_enter(s);
 return s->c == Ctrl_O;
}

bool ins_need_undo_get(void)
{
 return ins_need_undo;
}

/// Redraw for Insert mode.
/// This is postponed until getting the next character to make '$' in the 'cpo'
/// option work correctly.
/// Only redraw when there are no characters available.  This speeds up
/// inserting sequences of characters (e.g., for CTRL-R).
///
/// @param ready  not busy with something
void ins_redraw(bool ready)
{
 if (char_avail()) {
   return;
 }

 // Trigger CursorMoved if the cursor moved.  Not when the popup menu is
 // visible, the command might delete it.
 if (ready && has_event(EVENT_CURSORMOVEDI)
     && (last_cursormoved_win != curwin
         || !equalpos(last_cursormoved, curwin->w_cursor))
     && !pum_visible()) {
   // Need to update the screen first, to make sure syntax
   // highlighting is correct after making a change (e.g., inserting
   // a "(".  The autocommand may also require a redraw, so it's done
   // again below, unfortunately.
   if (syntax_present(curwin) && must_redraw) {
     update_screen();
   }
   // Make sure curswant is correct, an autocommand may call
   // getcurpos()
   update_curswant();
   ins_apply_autocmds(EVENT_CURSORMOVEDI);
   last_cursormoved_win = curwin;
   last_cursormoved = curwin->w_cursor;
 }

 // Trigger TextChangedI if changedtick_i differs.
 if (ready && has_event(EVENT_TEXTCHANGEDI)
     && curbuf->b_last_changedtick_i != buf_get_changedtick(curbuf)
     && !pum_visible()) {
   aco_save_T aco;
   varnumber_T tick = buf_get_changedtick(curbuf);

   // save and restore curwin and curbuf, in case the autocmd changes them
   aucmd_prepbuf(&aco, curbuf);
   apply_autocmds(EVENT_TEXTCHANGEDI, NULL, NULL, false, curbuf);
   aucmd_restbuf(&aco);
   curbuf->b_last_changedtick_i = buf_get_changedtick(curbuf);
   if (tick != buf_get_changedtick(curbuf)) {  // see ins_apply_autocmds()
     u_save(curwin->w_cursor.lnum,
            (linenr_T)(curwin->w_cursor.lnum + 1));
   }
 }

 // Trigger TextChangedP if changedtick_pum differs. When the popupmenu
 // closes TextChangedI will need to trigger for backwards compatibility,
 // thus use different b_last_changedtick* variables.
 if (ready && has_event(EVENT_TEXTCHANGEDP)
     && curbuf->b_last_changedtick_pum != buf_get_changedtick(curbuf)
     && pum_visible()) {
   aco_save_T aco;
   varnumber_T tick = buf_get_changedtick(curbuf);

   // save and restore curwin and curbuf, in case the autocmd changes them
   aucmd_prepbuf(&aco, curbuf);
   apply_autocmds(EVENT_TEXTCHANGEDP, NULL, NULL, false, curbuf);
   aucmd_restbuf(&aco);
   curbuf->b_last_changedtick_pum = buf_get_changedtick(curbuf);
   if (tick != buf_get_changedtick(curbuf)) {  // see ins_apply_autocmds()
     u_save(curwin->w_cursor.lnum,
            (linenr_T)(curwin->w_cursor.lnum + 1));
   }
 }

 if (ready) {
   may_trigger_win_scrolled_resized();
 }

 // Trigger BufModified if b_changed_invalid is set.
 if (ready && has_event(EVENT_BUFMODIFIEDSET)
     && curbuf->b_changed_invalid == true
     && !pum_visible()) {
   apply_autocmds(EVENT_BUFMODIFIEDSET, NULL, NULL, false, curbuf);
   curbuf->b_changed_invalid = false;
 }

 // Trigger SafeState if nothing is pending.
 may_trigger_safestate(ready
                       && !ins_compl_active()
                       && !pum_visible());

 pum_check_clear();
 show_cursor_info_later(false);
 if (must_redraw) {
   update_screen();
 } else {
   redraw_statuslines();
   if (clear_cmdline || redraw_cmdline || redraw_mode) {
     showmode();  // clear cmdline and show mode
   }
 }
 setcursor();
 emsg_on_display = false;      // may remove error message now
}

// Handle a CTRL-V or CTRL-Q typed in Insert mode.
static void ins_ctrl_v(void)
{
 bool did_putchar = false;

 // may need to redraw when no more chars available now
 ins_redraw(false);

 if (redrawing() && !char_avail()) {
   edit_putchar('^', true);
   did_putchar = true;
 }
 AppendToRedobuff(CTRL_V_STR);

 add_to_showcmd_c(Ctrl_V);

 // Do not include modifiers into the key for CTRL-SHIFT-V.
 int c = get_literal(mod_mask & MOD_MASK_SHIFT);
 if (did_putchar) {
   // when the line fits in 'columns' the '^' is at the start of the next
   // line and will not removed by the redraw
   edit_unputchar();
 }
 clear_showcmd();
 insert_special(c, true, true);
 revins_chars++;
 revins_legal++;
}

// Put a character directly onto the screen.  It's not stored in a buffer.
// Used while handling CTRL-K, CTRL-V, etc. in Insert mode.
static int pc_status;
#define PC_STATUS_UNSET 0  // nothing was put on screen
#define PC_STATUS_RIGHT 1  // right half of double-wide char
#define PC_STATUS_LEFT  2  // left half of double-wide char
#define PC_STATUS_SET   3  // pc_schar was filled
static schar_T pc_schar;   // saved char
static int pc_attr;
static int pc_row;
static int pc_col;

void edit_putchar(int c, bool highlight)
{
 if (curwin->w_grid_alloc.chars == NULL && default_grid.chars == NULL) {
   return;
 }

 int attr;
 update_topline(curwin);  // just in case w_topline isn't valid
 validate_cursor(curwin);
 if (highlight) {
   attr = HL_ATTR(HLF_8);
 } else {
   attr = 0;
 }
 pc_row = curwin->w_wrow;
 pc_status = PC_STATUS_UNSET;
 grid_line_start(&curwin->w_grid, pc_row);
 if (curwin->w_p_rl) {
   pc_col = curwin->w_view_width - 1 - curwin->w_wcol;

   if (grid_line_getchar(pc_col, NULL) == NUL) {
     grid_line_put_schar(pc_col - 1, schar_from_ascii(' '), attr);
     curwin->w_wcol--;
     pc_status = PC_STATUS_RIGHT;
   }
 } else {
   pc_col = curwin->w_wcol;

   if (grid_line_getchar(pc_col + 1, NULL) == NUL) {
     // pc_col is the left half of a double-width char
     pc_status = PC_STATUS_LEFT;
   }
 }

 // save the character to be able to put it back
 if (pc_status == PC_STATUS_UNSET) {
   pc_schar = grid_line_getchar(pc_col, &pc_attr);
   pc_status = PC_STATUS_SET;
 }

 char buf[MB_MAXCHAR + 1];
 grid_line_puts(pc_col, buf, utf_char2bytes(c, buf), attr);
 grid_line_flush();
}

/// @return    the effective prompt for the specified buffer.
char *buf_prompt_text(const buf_T *const buf)
 FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_PURE
{
 if (buf->b_prompt_text == NULL) {
   return "% ";
 }
 return buf->b_prompt_text;
}

/// @return  the effective prompt for the current buffer.
char *prompt_text(void)
 FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_PURE
{
 return buf_prompt_text(curbuf);
}

// Prepare for prompt mode: Make sure the last line has the prompt text.
// Move the cursor to this line.
static void init_prompt(int cmdchar_todo)
{
 char *prompt = prompt_text();
 int prompt_len = (int)strlen(prompt);

 // In case the mark is set to a nonexistent line.
 curbuf->b_prompt_start.mark.lnum = MAX(1, MIN(curbuf->b_prompt_start.mark.lnum,
                                               curbuf->b_ml.ml_line_count));

 curwin->w_cursor.lnum = MAX(curwin->w_cursor.lnum, curbuf->b_prompt_start.mark.lnum);
 char *text = ml_get(curbuf->b_prompt_start.mark.lnum);
 colnr_T text_len = ml_get_len(curbuf->b_prompt_start.mark.lnum);

 if ((curbuf->b_prompt_start.mark.lnum == curwin->w_cursor.lnum
      && (curbuf->b_prompt_start.mark.col < prompt_len
          || curbuf->b_prompt_start.mark.col > text_len
          || !strnequal(text + curbuf->b_prompt_start.mark.col - prompt_len, prompt,
                        (size_t)prompt_len)))) {
   // prompt is missing, insert it or append a line with it
   if (*text == NUL) {
     ml_replace(curbuf->b_prompt_start.mark.lnum, prompt, true);
     inserted_bytes(curbuf->b_prompt_start.mark.lnum, 0, 0, prompt_len);
   } else {
     const linenr_T lnum = curbuf->b_ml.ml_line_count;
     ml_append(lnum, prompt, 0, false);
     appended_lines_mark(lnum, 1);
     curbuf->b_prompt_start.mark.lnum = curbuf->b_ml.ml_line_count;
     // Like submitting, undo history was relevant to the old prompt.
     u_clearallandblockfree(curbuf);
   }
   curbuf->b_prompt_start.mark.col = prompt_len;
   curwin->w_cursor.lnum = curbuf->b_ml.ml_line_count;
   coladvance(curwin, MAXCOL);
 }

 // Insert always starts after the prompt, allow editing text after it.
 if (Insstart_orig.lnum != curbuf->b_prompt_start.mark.lnum
     || Insstart_orig.col != curbuf->b_prompt_start.mark.col) {
   Insstart.lnum = curbuf->b_prompt_start.mark.lnum;
   Insstart.col = curbuf->b_prompt_start.mark.col;
   Insstart_orig = Insstart;
   Insstart_textlen = Insstart.col;
   Insstart_blank_vcol = MAXCOL;
   arrow_used = false;
 }

 if (cmdchar_todo == 'A') {
   coladvance(curwin, MAXCOL);
 }
 if (curbuf->b_prompt_start.mark.lnum == curwin->w_cursor.lnum) {
   curwin->w_cursor.col = MAX(curwin->w_cursor.col, curbuf->b_prompt_start.mark.col);
 }
 // Make sure the cursor is in a valid position.
 check_cursor(curwin);
}

/// @return  true if the cursor is in the editable position of the prompt line.
bool prompt_curpos_editable(void)
 FUNC_ATTR_PURE
{
 return curwin->w_cursor.lnum > curbuf->b_prompt_start.mark.lnum
        || (curwin->w_cursor.lnum == curbuf->b_prompt_start.mark.lnum
            && curwin->w_cursor.col >= curbuf->b_prompt_start.mark.col);
}

// Undo the previous edit_putchar().
void edit_unputchar(void)
{
 if (pc_status != PC_STATUS_UNSET) {
   if (pc_status == PC_STATUS_RIGHT) {
     curwin->w_wcol++;
   }
   if (pc_status == PC_STATUS_RIGHT || pc_status == PC_STATUS_LEFT) {
     redrawWinline(curwin, curwin->w_cursor.lnum);
   } else {
     // TODO(bfredl): this could be smarter and also handle the dubyawidth case
     grid_line_start(&curwin->w_grid, pc_row);
     grid_line_put_schar(pc_col, pc_schar, pc_attr);
     grid_line_flush();
   }
 }
}

/// Called when "$" is in 'cpoptions': display a '$' at the end of the changed
/// text.  Only works when cursor is in the line that changes.
void display_dollar(colnr_T col_arg)
{
 colnr_T col = MAX(col_arg, 0);

 if (!redrawing()) {
   return;
 }

 colnr_T save_col = curwin->w_cursor.col;
 curwin->w_cursor.col = col;

 // If on the last byte of a multi-byte move to the first byte.
 char *p = get_cursor_line_ptr();
 curwin->w_cursor.col -= utf_head_off(p, p + col);
 curs_columns(curwin, false);              // Recompute w_wrow and w_wcol
 if (curwin->w_wcol < curwin->w_view_width) {
   edit_putchar('$', false);
   dollar_vcol = curwin->w_virtcol;
 }
 curwin->w_cursor.col = save_col;
}

// Call this function before moving the cursor from the normal insert position
// in insert mode.
void undisplay_dollar(void)
{
 if (dollar_vcol < 0) {
   return;
 }

 dollar_vcol = -1;
 redrawWinline(curwin, curwin->w_cursor.lnum);
}

/// Truncate the space at the end of a line.  This is to be used only in an
/// insert mode.  It handles fixing the replace stack for MODE_REPLACE and
/// MODE_VREPLACE modes.
void truncate_spaces(char *line, size_t len)
{
 int i;

 // find start of trailing white space
 for (i = (int)len - 1; i >= 0 && ascii_iswhite(line[i]); i--) {
   if (State & REPLACE_FLAG) {
     replace_join(0);              // remove a NUL from the replace stack
   }
 }
 line[i + 1] = NUL;
}

/// Backspace the cursor until the given column.  Handles MODE_REPLACE and
/// MODE_VREPLACE modes correctly.  May also be used when not in insert mode at
/// all.  Will attempt not to go before "col" even when there is a composing
/// character.
void backspace_until_column(int col)
{
 while ((int)curwin->w_cursor.col > col) {
   curwin->w_cursor.col--;
   if (State & REPLACE_FLAG) {
     replace_do_bs(col);
   } else if (!del_char_after_col(col)) {
     break;
   }
 }
}

/// Like del_char(), but make sure not to go before column "limit_col".
/// Only matters when there are composing characters.
///
/// @param  limit_col  only delete the character if it is after this column
//
/// @return true when something was deleted.
static bool del_char_after_col(int limit_col)
{
 if (limit_col >= 0) {
   colnr_T ecol = curwin->w_cursor.col + 1;

   // Make sure the cursor is at the start of a character, but
   // skip forward again when going too far back because of a
   // composing character.
   mb_adjust_cursor();
   while (curwin->w_cursor.col < (colnr_T)limit_col) {
     int l = utf_ptr2len(get_cursor_pos_ptr());

     if (l == 0) {  // end of line
       break;
     }
     curwin->w_cursor.col += l;
   }
   if (*get_cursor_pos_ptr() == NUL || curwin->w_cursor.col == ecol) {
     return false;
   }
   del_bytes(ecol - curwin->w_cursor.col, false, true);
 } else {
   del_char(false);
 }
 return true;
}

/// Next character is interpreted literally.
/// A one, two or three digit decimal number is interpreted as its byte value.
/// If one or two digits are entered, the next character is given to vungetc().
/// For Unicode a character > 255 may be returned.
///
/// @param  no_simplify  do not include modifiers into the key
int get_literal(bool no_simplify)
{
 int nc;
 bool hex = false;
 bool octal = false;
 int unicode = 0;

 if (got_int) {
   return Ctrl_C;
 }

 no_mapping++;                 // don't map the next key hits
 int cc = 0;
 int i = 0;
 while (true) {
   nc = plain_vgetc();
   if (!no_simplify) {
     nc = merge_modifiers(nc, &mod_mask);
   }
   if ((mod_mask & ~MOD_MASK_SHIFT) != 0) {
     // A character with non-Shift modifiers should not be a valid
     // character for i_CTRL-V_digit.
     break;
   }
   if ((State & MODE_CMDLINE) == 0 && MB_BYTE2LEN_CHECK(nc) == 1) {
     add_to_showcmd(nc);
   }
   if (nc == 'x' || nc == 'X') {
     hex = true;
   } else if (nc == 'o' || nc == 'O') {
     octal = true;
   } else if (nc == 'u' || nc == 'U') {
     unicode = nc;
   } else {
     if (hex
         || unicode != 0) {
       if (!ascii_isxdigit(nc)) {
         break;
       }
       cc = cc * 16 + hex2nr(nc);
     } else if (octal) {
       if (nc < '0' || nc > '7') {
         break;
       }
       cc = cc * 8 + nc - '0';
     } else {
       if (!ascii_isdigit(nc)) {
         break;
       }
       cc = cc * 10 + nc - '0';
     }

     i++;
   }

   if (cc > 255
       && unicode == 0) {
     cc = 255;                 // limit range to 0-255
   }
   nc = 0;

   if (hex) {                  // hex: up to two chars
     if (i >= 2) {
       break;
     }
   } else if (unicode) {     // Unicode: up to four or eight chars
     if ((unicode == 'u' && i >= 4) || (unicode == 'U' && i >= 8)) {
       break;
     }
   } else if (i >= 3) {        // decimal or octal: up to three chars
     break;
   }
 }
 if (i == 0) {     // no number entered
   if (nc == K_ZERO) {     // NUL is stored as NL
     cc = '\n';
     nc = 0;
   } else {
     cc = nc;
     nc = 0;
   }
 }

 if (cc == 0) {        // NUL is stored as NL
   cc = '\n';
 }

 no_mapping--;
 if (nc) {
   vungetc(nc);
   // A character typed with i_CTRL-V_digit cannot have modifiers.
   mod_mask = 0;
 }
 got_int = false;          // CTRL-C typed after CTRL-V is not an interrupt
 return cc;
}

/// Insert character, taking care of special keys and mod_mask
///
/// @param ctrlv `c` was typed after CTRL-V
static void insert_special(int c, int allow_modmask, int ctrlv)
{
 // Special function key, translate into "<Key>". Up to the last '>' is
 // inserted with ins_str(), so as not to replace characters in replace
 // mode.
 // Only use mod_mask for special keys, to avoid things like <S-Space>,
 // unless 'allow_modmask' is true.
 if (mod_mask & MOD_MASK_CMD) {  // Command-key never produces a normal key.
   allow_modmask = true;
 }
 if (IS_SPECIAL(c) || (mod_mask && allow_modmask)) {
   char *p = get_special_key_name(c, mod_mask);
   int len = (int)strlen(p);
   c = (uint8_t)p[len - 1];
   if (len > 2) {
     if (stop_arrow() == FAIL) {
       return;
     }
     p[len - 1] = NUL;
     ins_str(p, (size_t)(len - 1));
     AppendToRedobuffLit(p, -1);
     ctrlv = false;
   }
 }
 if (stop_arrow() == OK) {
   insertchar(c, ctrlv ? INSCHAR_CTRLV : 0, -1);
 }
}

// Special characters in this context are those that need processing other
// than the simple insertion that can be performed here. This includes ESC
// which terminates the insert, and CR/NL which need special processing to
// open up a new line. This routine tries to optimize insertions performed by
// the "redo", "undo" or "put" commands, so it needs to know when it should
// stop and defer processing to the "normal" mechanism.
// '0' and '^' are special, because they can be followed by CTRL-D.
#define ISSPECIAL(c)   ((c) < ' ' || (c) >= DEL || (c) == '0' || (c) == '^')

/// "flags": INSCHAR_FORMAT - force formatting
///          INSCHAR_CTRLV  - char typed just after CTRL-V
///          INSCHAR_NO_FEX - don't use 'formatexpr'
///
///   NOTE: passes the flags value straight through to internal_format() which,
///         beside INSCHAR_FORMAT (above), is also looking for these:
///          INSCHAR_DO_COM   - format comments
///          INSCHAR_COM_LIST - format comments with num list or 2nd line indent
///
/// @param c              character to insert or NUL
/// @param flags          INSCHAR_FORMAT, etc.
/// @param second_indent  indent for second line if >= 0
void insertchar(int c, int flags, int second_indent)
{
 char *p;
 int force_format = flags & INSCHAR_FORMAT;

 const int textwidth = comp_textwidth(force_format);
 const bool fo_ins_blank = has_format_option(FO_INS_BLANK);

 // Try to break the line in two or more pieces when:
 // - Always do this if we have been called to do formatting only.
 // - Always do this when 'formatoptions' has the 'a' flag and the line
 //   ends in white space.
 // - Otherwise:
 //     - Don't do this if inserting a blank
 //     - Don't do this if an existing character is being replaced, unless
 //       we're in MODE_VREPLACE state.
 //     - Do this if the cursor is not on the line where insert started
 //     or - 'formatoptions' doesn't have 'l' or the line was not too long
 //           before the insert.
 //        - 'formatoptions' doesn't have 'b' or a blank was inserted at or
 //          before 'textwidth'
 if (textwidth > 0
     && (force_format
         || (!ascii_iswhite(c)
             && !((State & REPLACE_FLAG)
                  && !(State & VREPLACE_FLAG)
                  && *get_cursor_pos_ptr() != NUL)
             && (curwin->w_cursor.lnum != Insstart.lnum
                 || ((!has_format_option(FO_INS_LONG)
                      || Insstart_textlen <= (colnr_T)textwidth)
                     && (!fo_ins_blank
                         || Insstart_blank_vcol <= (colnr_T)textwidth)))))) {
   // Format with 'formatexpr' when it's set.  Use internal formatting
   // when 'formatexpr' isn't set or it returns non-zero.
   bool do_internal = true;
   colnr_T virtcol = get_nolist_virtcol()
                     + char2cells(c != NUL ? c : gchar_cursor());

   if (*curbuf->b_p_fex != NUL && (flags & INSCHAR_NO_FEX) == 0
       && (force_format || virtcol > (colnr_T)textwidth)) {
     do_internal = (fex_format(curwin->w_cursor.lnum, 1, c) != 0);
     // It may be required to save for undo again, e.g. when setline()
     // was called.
     ins_need_undo = true;
   }
   if (do_internal) {
     internal_format(textwidth, second_indent, flags, c == NUL, c);
   }
 }

 if (c == NUL) {           // only formatting was wanted
   return;
 }

 // Check whether this character should end a comment.
 if (did_ai && c == end_comment_pending) {
   char lead_end[COM_MAX_LEN];  // end-comment string

   // Need to remove existing (middle) comment leader and insert end
   // comment leader.  First, check what comment leader we can find.
   char *line = get_cursor_line_ptr();
   int i = get_leader_len(line, &p, false, true);
   if (i > 0 && vim_strchr(p, COM_MIDDLE) != NULL) {  // Just checking
     // Skip middle-comment string
     while (*p && p[-1] != ':') {  // find end of middle flags
       p++;
     }
     int middle_len = (int)copy_option_part(&p, lead_end, COM_MAX_LEN, ",");
     // Don't count trailing white space for middle_len
     while (middle_len > 0 && ascii_iswhite(lead_end[middle_len - 1])) {
       middle_len--;
     }

     // Find the end-comment string
     while (*p && p[-1] != ':') {  // find end of end flags
       p++;
     }
     int end_len = (int)copy_option_part(&p, lead_end, COM_MAX_LEN, ",");

     // Skip white space before the cursor
     i = curwin->w_cursor.col;
     while (--i >= 0 && ascii_iswhite(line[i])) {}
     i++;

     // Skip to before the middle leader
     i -= middle_len;

     // Check some expected things before we go on
     if (i >= 0 && end_len > 0
         && (uint8_t)lead_end[end_len - 1] == end_comment_pending) {
       // Backspace over all the stuff we want to replace
       backspace_until_column(i);

       // Insert the end-comment string, except for the last
       // character, which will get inserted as normal later.
       ins_bytes_len(lead_end, (size_t)(end_len - 1));
     }
   }
 }
 end_comment_pending = NUL;

 did_ai = false;
 did_si = false;
 can_si = false;
 can_si_back = false;

 // If there's any pending input, grab up to INPUT_BUFLEN at once.
 // This speeds up normal text input considerably.
 // Don't do this when 'cindent' or 'indentexpr' is set, because we might
 // need to re-indent at a ':', or any other character (but not what
 // 'paste' is set)..
 // Don't do this when there an InsertCharPre autocommand is defined,
 // because we need to fire the event for every character.
 // Do the check for InsertCharPre before the call to vpeekc() because the
 // InsertCharPre autocommand could change the input buffer.
 if (!ISSPECIAL(c)
     && (utf_char2len(c) == 1)
     && !has_event(EVENT_INSERTCHARPRE)
     && !test_disable_char_avail
     && vpeekc() != NUL
     && !(State & REPLACE_FLAG)
     && !cindent_on()
     && !p_ri) {
#define INPUT_BUFLEN 100
   char buf[INPUT_BUFLEN + 1];
   colnr_T virtcol = 0;

   buf[0] = (char)c;
   int i = 1;
   if (textwidth > 0) {
     virtcol = get_nolist_virtcol();
   }
   // Stop the string when:
   // - no more chars available
   // - finding a special character (command key)
   // - buffer is full
   // - running into the 'textwidth' boundary
   // - need to check for abbreviation: A non-word char after a word-char
   while ((c = vpeekc()) != NUL
          && !ISSPECIAL(c)
          && MB_BYTE2LEN(c) == 1
          && i < INPUT_BUFLEN
          && (textwidth == 0
              || (virtcol += byte2cells((uint8_t)buf[i - 1])) < (colnr_T)textwidth)
          && !(!no_abbr && !vim_iswordc(c) && vim_iswordc((uint8_t)buf[i - 1]))) {
     c = vgetc();
     buf[i++] = (char)c;
   }

   do_digraph(-1);                     // clear digraphs
   do_digraph((uint8_t)buf[i - 1]);               // may be the start of a digraph
   buf[i] = NUL;
   ins_str(buf, (size_t)i);
   if (flags & INSCHAR_CTRLV) {
     redo_literal((uint8_t)(*buf));
     i = 1;
   } else {
     i = 0;
   }
   if (buf[i] != NUL) {
     AppendToRedobuffLit(buf + i, -1);
   }
 } else {
   int cc;

   if ((cc = utf_char2len(c)) > 1) {
     char buf[MB_MAXCHAR + 1];

     utf_char2bytes(c, buf);
     buf[cc] = NUL;
     ins_char_bytes(buf, (size_t)cc);
     AppendCharToRedobuff(c);
   } else {
     ins_char(c);
     if (flags & INSCHAR_CTRLV) {
       redo_literal(c);
     } else {
       AppendCharToRedobuff(c);
     }
   }
 }
}

// Put a character in the redo buffer, for when just after a CTRL-V.
static void redo_literal(int c)
{
 char buf[10];

 // Only digits need special treatment.  Translate them into a string of
 // three digits.
 if (ascii_isdigit(c)) {
   vim_snprintf(buf, sizeof(buf), "%03d", c);
   AppendToRedobuff(buf);
 } else {
   AppendCharToRedobuff(c);
 }
}

/// start_arrow() is called when an arrow key is used in insert mode.
/// For undo/redo it resembles hitting the <ESC> key.
///
/// @param end_insert_pos  can be NULL
void start_arrow(pos_T *end_insert_pos)
{
 start_arrow_common(end_insert_pos, true);
}

/// Like start_arrow() but with end_change argument.
/// Will prepare for redo of CTRL-G U if "end_change" is false.
///
/// @param end_insert_pos  can be NULL
/// @param end_change      end undoable change
static void start_arrow_with_change(pos_T *end_insert_pos, bool end_change)
{
 start_arrow_common(end_insert_pos, end_change);
 if (!end_change) {
   AppendCharToRedobuff(Ctrl_G);
   AppendCharToRedobuff('U');
 }
}

/// @param end_insert_pos  can be NULL
/// @param end_change      end undoable change
static void start_arrow_common(pos_T *end_insert_pos, bool end_change)
{
 if (!arrow_used && end_change) {  // something has been inserted
   AppendToRedobuff(ESC_STR);
   stop_insert(end_insert_pos, false, false);
   arrow_used = true;  // This means we stopped the current insert.
 }
 check_spell_redraw();
}

// If we skipped highlighting word at cursor, do it now.
// It may be skipped again, thus reset spell_redraw_lnum first.
static void check_spell_redraw(void)
{
 if (spell_redraw_lnum != 0) {
   linenr_T lnum = spell_redraw_lnum;

   spell_redraw_lnum = 0;
   redrawWinline(curwin, lnum);
 }
}

// stop_arrow() is called before a change is made in insert mode.
// If an arrow key has been used, start a new insertion.
// Returns FAIL if undo is impossible, shouldn't insert then.
int stop_arrow(void)
{
 if (arrow_used) {
   Insstart = curwin->w_cursor;  // new insertion starts here
   if (Insstart.col > Insstart_orig.col && !ins_need_undo) {
     // Don't update the original insert position when moved to the
     // right, except when nothing was inserted yet.
     update_Insstart_orig = false;
   }
   Insstart_textlen = linetabsize_str(get_cursor_line_ptr());

   if (u_save_cursor() == OK) {
     arrow_used = false;
     ins_need_undo = false;
   }
   ai_col = 0;
   if (State & VREPLACE_FLAG) {
     orig_line_count = curbuf->b_ml.ml_line_count;
     vr_lines_changed = 1;
   }
   ResetRedobuff();
   AppendToRedobuff("1i");  // Pretend we start an insertion.
   new_insert_skip = 2;
 } else if (ins_need_undo) {
   if (u_save_cursor() == OK) {
     ins_need_undo = false;
   }
 }

 // Always open fold at the cursor line when inserting something.
 foldOpenCursor();

 return arrow_used || ins_need_undo ? FAIL : OK;
}

/// Do a few things to stop inserting.
/// "end_insert_pos" is where insert ended.  It is NULL when we already jumped
/// to another window/buffer.
///
/// @param esc     called by ins_esc()
/// @param nomove  <c-\><c-o>, don't move cursor
static void stop_insert(pos_T *end_insert_pos, int esc, int nomove)
{
 stop_redo_ins();
 kv_destroy(replace_stack);  // abandon replace stack (reinitializes)

 // Save the inserted text for later redo with ^@ and CTRL-A.
 // Don't do it when "restart_edit" was set and nothing was inserted,
 // otherwise CTRL-O w and then <Left> will clear "last_insert".
 String inserted = get_inserted();
 int added = inserted.data == NULL ? 0 : (int)inserted.size - new_insert_skip;
 if (did_restart_edit == 0 || added > 0) {
   xfree(last_insert.data);
   last_insert = inserted;  // structure copy
   last_insert_skip = added < 0 ? 0 : new_insert_skip;
 } else {
   xfree(inserted.data);
 }

 if (!arrow_used && end_insert_pos != NULL) {
   int cc;
   // Auto-format now.  It may seem strange to do this when stopping an
   // insertion (or moving the cursor), but it's required when appending
   // a line and having it end in a space.  But only do it when something
   // was actually inserted, otherwise undo won't work.
   if (!ins_need_undo && has_format_option(FO_AUTO)) {
     pos_T tpos = curwin->w_cursor;

     // When the cursor is at the end of the line after a space the
     // formatting will move it to the following word.  Avoid that by
     // moving the cursor onto the space.
     cc = 'x';
     if (curwin->w_cursor.col > 0 && gchar_cursor() == NUL) {
       dec_cursor();
       cc = gchar_cursor();
       if (!ascii_iswhite(cc)) {
         curwin->w_cursor = tpos;
       }
     }

     auto_format(true, false);

     if (ascii_iswhite(cc)) {
       if (gchar_cursor() != NUL) {
         inc_cursor();
       }
       // If the cursor is still at the same character, also keep
       // the "coladd".
       if (gchar_cursor() == NUL
           && curwin->w_cursor.lnum == tpos.lnum
           && curwin->w_cursor.col == tpos.col) {
         curwin->w_cursor.coladd = tpos.coladd;
       }
     }
   }

   // If a space was inserted for auto-formatting, remove it now.
   check_auto_format(true);

   // If we just did an auto-indent, remove the white space from the end
   // of the line, and put the cursor back.
   // Do this when ESC was used or moving the cursor up/down.
   // Check for the old position still being valid, just in case the text
   // got changed unexpectedly.
   if (!nomove && did_ai && (esc || (vim_strchr(p_cpo, CPO_INDENT) == NULL
                                     && curwin->w_cursor.lnum !=
                                     end_insert_pos->lnum))
       && end_insert_pos->lnum <= curbuf->b_ml.ml_line_count) {
     pos_T tpos = curwin->w_cursor;
     colnr_T prev_col = end_insert_pos->col;

     curwin->w_cursor = *end_insert_pos;
     check_cursor_col(curwin);        // make sure it is not past the line
     while (true) {
       if (gchar_cursor() == NUL && curwin->w_cursor.col > 0) {
         curwin->w_cursor.col--;
       }
       cc = gchar_cursor();
       if (!ascii_iswhite(cc)) {
         break;
       }
       if (del_char(true) == FAIL) {
         break;            // should not happen
       }
     }
     if (curwin->w_cursor.lnum != tpos.lnum) {
       curwin->w_cursor = tpos;
     } else if (curwin->w_cursor.col < prev_col) {
       // reset tpos, could have been invalidated in the loop above
       tpos = curwin->w_cursor;
       tpos.col++;
       if (cc != NUL && gchar_pos(&tpos) == NUL) {
         curwin->w_cursor.col++;         // put cursor back on the NUL
       }
     }

     // <C-S-Right> may have started Visual mode, adjust the position for
     // deleted characters.
     if (VIsual_active) {
       check_visual_pos();
     }
   }
 }
 did_ai = false;
 did_si = false;
 can_si = false;
 can_si_back = false;

 // Set '[ and '] to the inserted text.  When end_insert_pos is NULL we are
 // now in a different buffer.
 if (end_insert_pos != NULL) {
   curbuf->b_op_start = Insstart;
   curbuf->b_op_start_orig = Insstart_orig;
   curbuf->b_op_end = *end_insert_pos;
 }
}

// Set the last inserted text to a single character.
// Used for the replace command.
void set_last_insert(int c)
{
 xfree(last_insert.data);
 last_insert.data = xmalloc(MB_MAXBYTES * 3 + 5);
 char *s = last_insert.data;
 // Use the CTRL-V only when entering a special char
 if (c < ' ' || c == DEL) {
   *s++ = Ctrl_V;
 }
 s = add_char2buf(c, s);
 *s++ = ESC;
 *s = NUL;
 last_insert.size = (size_t)(s - last_insert.data);
 last_insert_skip = 0;
}

#if defined(EXITFREE)
void free_last_insert(void)
{
 API_CLEAR_STRING(last_insert);
}
#endif

// move cursor to start of line
// if flags & BL_WHITE  move to first non-white
// if flags & BL_SOL    move to first non-white if startofline is set,
//                          otherwise keep "curswant" column
// if flags & BL_FIX    don't leave the cursor on a NUL.
void beginline(int flags)
{
 if ((flags & BL_SOL) && !p_sol) {
   coladvance(curwin, curwin->w_curswant);
 } else {
   curwin->w_cursor.col = 0;
   curwin->w_cursor.coladd = 0;

   if (flags & (BL_WHITE | BL_SOL)) {
     for (char *ptr = get_cursor_line_ptr(); ascii_iswhite(*ptr)
          && !((flags & BL_FIX) && ptr[1] == NUL); ptr++) {
       curwin->w_cursor.col++;
     }
   }
   curwin->w_set_curswant = true;
 }
 adjust_skipcol();
}

// oneright oneleft cursor_down cursor_up
//
// Move one char {right,left,down,up}.
// Doesn't move onto the NUL past the end of the line, unless it is allowed.
// Return OK when successful, FAIL when we hit a line of file boundary.

int oneright(void)
{
 char *ptr;

 if (virtual_active(curwin)) {
   pos_T prevpos = curwin->w_cursor;

   // Adjust for multi-wide char (excluding TAB)
   ptr = get_cursor_pos_ptr();
   coladvance(curwin, getviscol() + ((*ptr != TAB && vim_isprintc(utf_ptr2char(ptr)))
                                     ? ptr2cells(ptr) : 1));
   curwin->w_set_curswant = true;
   // Return OK if the cursor moved, FAIL otherwise (at window edge).
   return (prevpos.col != curwin->w_cursor.col
           || prevpos.coladd != curwin->w_cursor.coladd) ? OK : FAIL;
 }

 ptr = get_cursor_pos_ptr();
 if (*ptr == NUL) {
   return FAIL;            // already at the very end
 }

 int l = utfc_ptr2len(ptr);

 // move "l" bytes right, but don't end up on the NUL, unless 'virtualedit'
 // contains "onemore".
 if (ptr[l] == NUL && (get_ve_flags(curwin) & kOptVeFlagOnemore) == 0) {
   return FAIL;
 }
 curwin->w_cursor.col += l;

 curwin->w_set_curswant = true;
 adjust_skipcol();
 return OK;
}

int oneleft(void)
{
 if (virtual_active(curwin)) {
   int v = getviscol();

   if (v == 0) {
     return FAIL;
   }

   // We might get stuck on 'showbreak', skip over it.
   int width = 1;
   while (true) {
     coladvance(curwin, v - width);
     // getviscol() is slow, skip it when 'showbreak' is empty,
     // 'breakindent' is not set and there are no multi-byte
     // characters
     if (getviscol() < v) {
       break;
     }
     width++;
   }

   if (curwin->w_cursor.coladd == 1) {
     // Adjust for multi-wide char (not a TAB)
     char *ptr = get_cursor_pos_ptr();
     if (*ptr != TAB && vim_isprintc(utf_ptr2char(ptr)) && ptr2cells(ptr) > 1) {
       curwin->w_cursor.coladd = 0;
     }
   }

   curwin->w_set_curswant = true;
   adjust_skipcol();
   return OK;
 }

 if (curwin->w_cursor.col == 0) {
   return FAIL;
 }

 curwin->w_set_curswant = true;
 curwin->w_cursor.col--;

 // if the character on the left of the current cursor is a multi-byte
 // character, move to its first byte
 mb_adjust_cursor();
 adjust_skipcol();
 return OK;
}

/// Move the cursor up "n" lines in window "wp". Takes care of closed folds.
/// Skips over concealed lines when "skip_conceal" is true.
void cursor_up_inner(win_T *wp, linenr_T n, bool skip_conceal)
{
 linenr_T lnum = wp->w_cursor.lnum;

 if (n >= lnum) {
   lnum = 1;
 } else if (win_lines_concealed(wp)) {
   // Count each sequence of folded lines as one logical line.

   // go to the start of the current fold
   hasFolding(wp, lnum, &lnum, NULL);

   while (n--) {
     // move up one line
     lnum--;
     if (lnum <= 1) {
       break;
     }
     n += skip_conceal && decor_conceal_line(wp, lnum - 1, true);
     // If we entered a fold, move to the beginning, unless in
     // Insert mode or when 'foldopen' contains "all": it will open
     // in a moment.
     if (n > 0 || !((State & MODE_INSERT) || (fdo_flags & kOptFdoFlagAll))) {
       hasFolding(wp, lnum, &lnum, NULL);
     }
   }
   lnum = MAX(lnum, 1);
 } else {
   lnum -= n;
 }

 wp->w_cursor.lnum = lnum;
}

/// @param upd_topline  When true: update topline
int cursor_up(linenr_T n, bool upd_topline)
{
 // This fails if the cursor is already in the first line.
 if (n > 0 && curwin->w_cursor.lnum <= 1) {
   return FAIL;
 }
 cursor_up_inner(curwin, n, false);

 // try to advance to the column we want to be at
 coladvance(curwin, curwin->w_curswant);

 if (upd_topline) {
   update_topline(curwin);  // make sure curwin->w_topline is valid
 }

 return OK;
}

/// Move the cursor down "n" lines in window "wp". Takes care of closed folds.
/// Skips over concealed lines when "skip_conceal" is true.
void cursor_down_inner(win_T *wp, int n, bool skip_conceal)
{
 linenr_T lnum = wp->w_cursor.lnum;
 linenr_T line_count = wp->w_buffer->b_ml.ml_line_count;

 if (lnum + n >= line_count) {
   lnum = line_count;
 } else if (win_lines_concealed(wp)) {
   linenr_T last;

   // count each sequence of folded lines as one logical line
   while (n--) {
     if (hasFoldingWin(wp, lnum, NULL, &last, true, NULL)) {
       lnum = last + 1;
     } else {
       lnum++;
     }
     if (lnum >= line_count) {
       break;
     }
     n += skip_conceal && decor_conceal_line(wp, lnum - 1, true);
   }
   lnum = MIN(lnum, line_count);
 } else {
   lnum += (linenr_T)n;
 }

 wp->w_cursor.lnum = lnum;
}

/// @param upd_topline  When true: update topline
int cursor_down(int n, bool upd_topline)
{
 linenr_T lnum = curwin->w_cursor.lnum;
 // This fails if the cursor is already in the last (folded) line.
 hasFoldingWin(curwin, lnum, NULL, &lnum, true, NULL);
 if (n > 0 && lnum >= curwin->w_buffer->b_ml.ml_line_count) {
   return FAIL;
 }
 cursor_down_inner(curwin, n, false);

 // try to advance to the column we want to be at
 coladvance(curwin, curwin->w_curswant);

 if (upd_topline) {
   update_topline(curwin);           // make sure curwin->w_topline is valid
 }

 return OK;
}

/// Stuff the last inserted text in the read buffer.
/// Last_insert actually is a copy of the redo buffer, so we
/// first have to remove the command.
///
/// @param c       Command character to be inserted
/// @param count   Repeat this many times
/// @param no_esc  Don't add an ESC at the end
int stuff_inserted(int c, int count, int no_esc)
{
 char last = NUL;

 String insert = get_last_insert();  // text to be inserted
 if (insert.data == NULL) {
   emsg(_(e_noinstext));
   return FAIL;
 }

 // may want to stuff the command character, to start Insert mode
 if (c != NUL) {
   stuffcharReadbuff(c);
 }

 if (insert.size > 0) {
   // look for the last ESC in 'insert'
   for (char *p = insert.data + insert.size - 1; p >= insert.data; p--) {
     if (*p == ESC) {
       insert.size = (size_t)(p - insert.data);
       break;
     }
   }
 }

 if (insert.size > 0) {
   char *p = insert.data + insert.size - 1;
   // when the last char is either "0" or "^" it will be quoted if no ESC
   // comes after it OR if it will inserted more than once and "ptr"
   // starts with ^D.  -- Acevedo
   if ((*p == '0' || *p == '^')
       && (no_esc || (*insert.data == Ctrl_D && count > 1))) {
     last = *p;
     insert.size--;
   }
 }

 do {
   stuffReadbuffLen(insert.data, (ptrdiff_t)insert.size);
   // A trailing "0" is inserted as "<C-V>048", "^" as "<C-V>^".
   switch (last) {
   case '0':
     stuffReadbuffLen(S_LEN("\026\060\064\070"));
     break;
   case '^':
     stuffReadbuffLen(S_LEN("\026^"));
     break;
   default:
     break;
   }
 } while (--count > 0);

 // may want to stuff a trailing ESC, to get out of Insert mode
 if (!no_esc) {
   stuffcharReadbuff(ESC);
 }

 return OK;
}

String get_last_insert(void)
 FUNC_ATTR_PURE
{
 return last_insert.data == NULL ? NULL_STRING : (String){
   .data = last_insert.data + last_insert_skip,
   .size = last_insert.size - (size_t)last_insert_skip,
 };
}

// Get last inserted string, and remove trailing <Esc>.
// Returns pointer to allocated memory (must be freed) or NULL.
char *get_last_insert_save(void)
{
 String insert = get_last_insert();

 if (insert.data == NULL) {
   return NULL;
 }

 char *s = xmemdupz(insert.data, insert.size);
 if (insert.size > 0 && s[insert.size - 1] == ESC) {  // remain trailing ESC
   s[--insert.size] = NUL;
 }
 return s;
}

/// Check the word in front of the cursor for an abbreviation.
/// Called when the non-id character "c" has been entered.
/// When an abbreviation is recognized it is removed from the text and
/// the replacement string is inserted in typebuf.tb_buf[], followed by "c".
///
/// @param  c  character
///
/// @return true if the word is a known abbreviation.
static bool echeck_abbr(int c)
 FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
{
 // Don't check for abbreviation in paste mode, when disabled and just
 // after moving around with cursor keys.
 if (p_paste || no_abbr || arrow_used) {
   return false;
 }

 return check_abbr(c, get_cursor_line_ptr(), curwin->w_cursor.col,
                   curwin->w_cursor.lnum == Insstart.lnum ? Insstart.col : 0);
}

// replace-stack functions
//
// When replacing characters, the replaced characters are remembered for each
// new character.  This is used to re-insert the old text when backspacing.
//
// There is a NUL headed list of characters for each character that is
// currently in the file after the insertion point.  When BS is used, one NUL
// headed list is put back for the deleted character.
//
// For a newline, there are two NUL headed lists.  One contains the characters
// that the NL replaced.  The extra one stores the characters after the cursor
// that were deleted (always white space).

/// Push character that is replaced onto the replace stack.
///
/// replace_offset is normally 0, in which case replace_push will add a new
/// character at the end of the stack.  If replace_offset is not 0, that many
/// characters will be left on the stack above the newly inserted character.
///
/// @param str character that is replaced (NUL is none)
/// @param len length of character in bytes
void replace_push(char *str, size_t len)
{
 // TODO(bfredl): replace_offset is suss af, if we don't need it, this
 // function is just kv_concat() :p
 if (kv_size(replace_stack) < (size_t)replace_offset) {  // nothing to do
   return;
 }

 kv_ensure_space(replace_stack, len);

 char *p = replace_stack.items + kv_size(replace_stack) - replace_offset;
 if (replace_offset) {
   memmove(p + len, p, (size_t)replace_offset);
 }
 memcpy(p, str, len);
 kv_size(replace_stack) += len;
}

/// push NUL as separator between entries in the stack
void replace_push_nul(void)
{
 replace_push("", 1);
}

/// Check top of replace stack, pop it if it was NUL
///
/// when a non-NUL byte is found, use mb_replace_pop_ins() to
/// pop one complete multibyte character.
///
/// @return -1 if stack is empty, last byte of char or NUL otherwise
static int replace_pop_if_nul(void)
{
 int ch = (kv_size(replace_stack)) ? (uint8_t)kv_A(replace_stack, kv_size(replace_stack) - 1) : -1;
 if (ch == NUL) {
   kv_size(replace_stack)--;
 }
 return ch;
}

/// Join the top two items on the replace stack.  This removes to "off"'th NUL
/// encountered.
///
/// @param off  offset for which NUL to remove
void replace_join(int off)
{
 for (ssize_t i = (ssize_t)kv_size(replace_stack); --i >= 0;) {
   if (kv_A(replace_stack, i) == NUL && off-- <= 0) {
     kv_size(replace_stack)--;
     memmove(&kv_A(replace_stack, i), &kv_A(replace_stack, i + 1),
             (kv_size(replace_stack) - (size_t)i));
     return;
   }
 }
}

/// Pop bytes from the replace stack until a NUL is found, and insert them
/// before the cursor.  Can only be used in MODE_REPLACE or MODE_VREPLACE state.
static void replace_pop_ins(void)
{
 int oldState = State;

 State = MODE_NORMAL;                       // don't want MODE_REPLACE here
 while ((replace_pop_if_nul()) > 0) {
   mb_replace_pop_ins();
   dec_cursor();
 }
 State = oldState;
}

/// Insert multibyte char popped from the replace stack.
///
/// caller must already have checked the top of the stack is not NUL!!
static void mb_replace_pop_ins(void)
{
 int len = utf_head_off(&kv_A(replace_stack, 0),
                        &kv_A(replace_stack, kv_size(replace_stack) - 1)) + 1;
 kv_size(replace_stack) -= (size_t)len;
 ins_bytes_len(&kv_A(replace_stack, kv_size(replace_stack)), (size_t)len);
}

// Handle doing a BS for one character.
// cc < 0: replace stack empty, just move cursor
// cc == 0: character was inserted, delete it
// cc > 0: character was replaced, put cc (first byte of original char) back
// and check for more characters to be put back
// When "limit_col" is >= 0, don't delete before this column.  Matters when
// using composing characters, use del_char_after_col() instead of del_char().
static void replace_do_bs(int limit_col)
{
 colnr_T start_vcol;
 const int l_State = State;

 int cc = replace_pop_if_nul();
 if (cc > 0) {
   int orig_len = 0;
   int orig_vcols = 0;
   if (l_State & VREPLACE_FLAG) {
     // Get the number of screen cells used by the character we are
     // going to delete.
     getvcol(curwin, &curwin->w_cursor, NULL, &start_vcol, NULL);
     orig_vcols = win_chartabsize(curwin, get_cursor_pos_ptr(), start_vcol);
   }
   del_char_after_col(limit_col);
   if (l_State & VREPLACE_FLAG) {
     orig_len = get_cursor_pos_len();
   }
   replace_pop_ins();

   if (l_State & VREPLACE_FLAG) {
     // Get the number of screen cells used by the inserted characters
     char *p = get_cursor_pos_ptr();
     int ins_len = get_cursor_pos_len() - orig_len;
     int vcol = start_vcol;
     for (int i = 0; i < ins_len; i++) {
       vcol += win_chartabsize(curwin, p + i, vcol);
       i += utfc_ptr2len(p) - 1;
     }
     vcol -= start_vcol;

     // Delete spaces that were inserted after the cursor to keep the
     // text aligned.
     curwin->w_cursor.col += ins_len;
     while (vcol > orig_vcols && gchar_cursor() == ' ') {
       del_char(false);
       orig_vcols++;
     }
     curwin->w_cursor.col -= ins_len;
   }

   // mark the buffer as changed and prepare for displaying
   changed_bytes(curwin->w_cursor.lnum, curwin->w_cursor.col);
 } else if (cc == 0) {
   del_char_after_col(limit_col);
 }
}

static void ins_reg(void)
{
 bool need_redraw = false;
 int literally = 0;
 int vis_active = VIsual_active;

 // If we are going to wait for a character, show a '"'.
 pc_status = PC_STATUS_UNSET;
 if (redrawing() && !char_avail()) {
   // may need to redraw when no more chars available now
   ins_redraw(false);

   edit_putchar('"', true);
   add_to_showcmd_c(Ctrl_R);
 }

 // Don't map the register name. This also prevents the mode message to be
 // deleted when ESC is hit.
 no_mapping++;
 allow_keys++;
 int regname = plain_vgetc();
 LANGMAP_ADJUST(regname, true);
 if (regname == Ctrl_R || regname == Ctrl_O || regname == Ctrl_P) {
   // Get a third key for literal register insertion
   literally = regname;
   add_to_showcmd_c(literally);
   regname = plain_vgetc();
   LANGMAP_ADJUST(regname, true);
 }
 no_mapping--;
 allow_keys--;

 // Don't call u_sync() while typing the expression or giving an error
 // message for it. Only call it explicitly.
 no_u_sync++;
 if (regname == '=') {
   pos_T curpos = curwin->w_cursor;

   // Sync undo when evaluating the expression calls setline() or
   // append(), so that it can be undone separately.
   u_sync_once = 2;

   regname = get_expr_register();

   // Cursor may be moved back a column.
   curwin->w_cursor = curpos;
   check_cursor(curwin);
 }
 if (regname == NUL || !valid_yank_reg(regname, false)) {
   vim_beep(kOptBoFlagRegister);
   need_redraw = true;  // remove the '"'
 } else {
   yankreg_T *reg = get_yank_register(regname, YREG_PASTE);

   if (literally == Ctrl_O || literally == Ctrl_P) {
     // Append the command to the redo buffer.
     AppendCharToRedobuff(Ctrl_R);
     AppendCharToRedobuff(literally);
     AppendCharToRedobuff(regname);

     do_put(regname, NULL, BACKWARD, 1,
            (literally == Ctrl_P ? PUT_FIXINDENT : 0) | PUT_CURSEND);
   } else if (reg->y_size > 1 && is_literal_register(regname)) {
     AppendCharToRedobuff(Ctrl_R);
     AppendCharToRedobuff(regname);
     do_put(regname, NULL, BACKWARD, 1, PUT_CURSEND);
   } else if (insert_reg(regname, NULL, !!literally) == FAIL) {
     vim_beep(kOptBoFlagRegister);
     need_redraw = true;  // remove the '"'
   } else if (stop_insert_mode) {
     // When the '=' register was used and a function was invoked that
     // did ":stopinsert" then stuff_empty() returns false but we won't
     // insert anything, need to remove the '"'
     need_redraw = true;
   }
 }
 no_u_sync--;
 if (u_sync_once == 1) {
   ins_need_undo = true;
 }
 u_sync_once = 0;

 // If the inserted register is empty, we need to remove the '"'. Do this before
 // clearing showcmd, which emits an event that can also update the screen.
 if (need_redraw || stuff_empty()) {
   edit_unputchar();
 }
 clear_showcmd();

 // Disallow starting Visual mode here, would get a weird mode.
 if (!vis_active && VIsual_active) {
   end_visual_mode();
 }
}

// CTRL-G commands in Insert mode.
static void ins_ctrl_g(void)
{
 // Right after CTRL-X the cursor will be after the ruler.
 setcursor();

 // Don't map the second key. This also prevents the mode message to be
 // deleted when ESC is hit.
 no_mapping++;
 allow_keys++;
 int c = plain_vgetc();
 no_mapping--;
 allow_keys--;
 switch (c) {
 // CTRL-G k and CTRL-G <Up>: cursor up to Insstart.col
 case K_UP:
 case Ctrl_K:
 case 'k':
   ins_up(true);
   break;

 // CTRL-G j and CTRL-G <Down>: cursor down to Insstart.col
 case K_DOWN:
 case Ctrl_J:
 case 'j':
   ins_down(true);
   break;

 // CTRL-G u: start new undoable edit
 case 'u':
   u_sync(true);
   ins_need_undo = true;

   // Need to reset Insstart, esp. because a BS that joins
   // a line to the previous one must save for undo.
   update_Insstart_orig = false;
   Insstart = curwin->w_cursor;
   break;

 // CTRL-G U: do not break undo with the next char.
 case 'U':
   // Allow one left/right cursor movement with the next char,
   // without breaking undo.
   dont_sync_undo = kNone;
   break;

 case ESC:
   // Esc after CTRL-G cancels it.
   break;

 // Unknown CTRL-G command, reserved for future expansion.
 default:
   vim_beep(kOptBoFlagCtrlg);
 }
}

// CTRL-^ in Insert mode.
static void ins_ctrl_hat(void)
{
 if (map_to_exists_mode("", MODE_LANGMAP, false)) {
   // ":lmap" mappings exists, Toggle use of ":lmap" mappings.
   if (State & MODE_LANGMAP) {
     curbuf->b_p_iminsert = B_IMODE_NONE;
     State &= ~MODE_LANGMAP;
   } else {
     curbuf->b_p_iminsert = B_IMODE_LMAP;
     State |= MODE_LANGMAP;
   }
 }
 set_iminsert_global(curbuf);
 showmode();
 // Show/unshow value of 'keymap' in status lines.
 status_redraw_curbuf();
}

/// Handle ESC in insert mode.
///
/// @param[in,out]  count    repeat count of the insert command
/// @param          cmdchar  command that started the insert
/// @param          nomove   when true, don't move the cursor
///
/// @return true when leaving insert mode, false when repeating the insert.
static bool ins_esc(int *count, int cmdchar, bool nomove)
 FUNC_ATTR_NONNULL_ARG(1)
{
 static bool disabled_redraw = false;

 check_spell_redraw();

 int temp = curwin->w_cursor.col;
 if (disabled_redraw) {
   RedrawingDisabled--;
   disabled_redraw = false;
 }
 if (!arrow_used) {
   // Don't append the ESC for "r<CR>" and "grx".
   if (cmdchar != 'r' && cmdchar != 'v') {
     AppendToRedobuff(ESC_STR);
   }

   // Repeating insert may take a long time.  Check for
   // interrupt now and then.
   if (*count > 0) {
     line_breakcheck();
     if (got_int) {
       *count = 0;
     }
   }

   if (--*count > 0) {         // repeat what was typed
     // Vi repeats the insert without replacing characters.
     if (vim_strchr(p_cpo, CPO_REPLCNT) != NULL) {
       State &= ~REPLACE_FLAG;
     }

     start_redo_ins();
     if (cmdchar == 'r' || cmdchar == 'v') {
       stuffRedoReadbuff(ESC_STR);  // No ESC in redo buffer
     }
     RedrawingDisabled++;
     disabled_redraw = true;
     // Repeat the insert
     return false;
   }
   stop_insert(&curwin->w_cursor, true, nomove);
   undisplay_dollar();
 }

 if (cmdchar != 'r' && cmdchar != 'v') {
   ins_apply_autocmds(EVENT_INSERTLEAVEPRE);
 }

 // When an autoindent was removed, curswant stays after the
 // indent
 if (restart_edit == NUL && (colnr_T)temp == curwin->w_cursor.col) {
   curwin->w_set_curswant = true;
 }

 // Remember the last Insert position in the '^ mark.
 if ((cmdmod.cmod_flags & CMOD_KEEPJUMPS) == 0) {
   fmarkv_T view = mark_view_make(curwin->w_topline, curwin->w_cursor);
   RESET_FMARK(&curbuf->b_last_insert, curwin->w_cursor, curbuf->b_fnum, view);
 }

 // The cursor should end up on the last inserted character.
 // Don't do it for CTRL-O, unless past the end of the line.
 if (!nomove
     && (curwin->w_cursor.col != 0 || curwin->w_cursor.coladd > 0)
     && (restart_edit == NUL || (gchar_cursor() == NUL && !VIsual_active))
     && !revins_on) {
   if (curwin->w_cursor.coladd > 0 || get_ve_flags(curwin) == kOptVeFlagAll) {
     oneleft();
     if (restart_edit != NUL) {
       curwin->w_cursor.coladd++;
     }
   } else {
     curwin->w_cursor.col--;
     curwin->w_valid &= ~(VALID_WCOL|VALID_VIRTCOL);
     // Correct cursor for multi-byte character.
     mb_adjust_cursor();
   }
 }

 State = MODE_NORMAL;
 may_trigger_modechanged();
 // need to position cursor again when on a TAB and
 // when on a char with inline virtual text
 if (gchar_cursor() == TAB || buf_meta_total(curbuf, kMTMetaInline) > 0) {
   curwin->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL);
 }

 setmouse();
 ui_cursor_shape();            // may show different cursor shape

 // When recording or for CTRL-O, need to display the new mode.
 // Otherwise remove the mode message.
 if (reg_recording != 0 || restart_edit != NUL) {
   showmode();
 } else if (p_smd && (got_int || !skip_showmode())
            && !(p_ch == 0 && !ui_has(kUIMessages))) {
   unshowmode(false);
 }
 // Exit Insert mode
 return true;
}

// Toggle language: revins_on.
// Move to end of reverse inserted text.
static void ins_ctrl_(void)
{
 if (revins_on && revins_chars && revins_scol >= 0) {
   while (gchar_cursor() != NUL && revins_chars--) {
     curwin->w_cursor.col++;
   }
 }
 p_ri = !p_ri;
 revins_on = (State == MODE_INSERT && p_ri);
 if (revins_on) {
   revins_scol = curwin->w_cursor.col;
   revins_legal++;
   revins_chars = 0;
   undisplay_dollar();
 } else {
   revins_scol = -1;
 }
 showmode();
}

/// If 'keymodel' contains "startsel", may start selection.
///
/// @param  c  character to check
//
/// @return true when a CTRL-O and other keys stuffed.
static bool ins_start_select(int c)
 FUNC_ATTR_WARN_UNUSED_RESULT
{
 if (!km_startsel) {
   return false;
 }
 switch (c) {
 case K_KHOME:
 case K_KEND:
 case K_PAGEUP:
 case K_KPAGEUP:
 case K_PAGEDOWN:
 case K_KPAGEDOWN:
   if (!(mod_mask & MOD_MASK_SHIFT)) {
     break;
   }
   FALLTHROUGH;
 case K_S_LEFT:
 case K_S_RIGHT:
 case K_S_UP:
 case K_S_DOWN:
 case K_S_END:
 case K_S_HOME:
   // Start selection right away, the cursor can move with CTRL-O when
   // beyond the end of the line.
   start_selection();

   // Execute the key in (insert) Select mode.
   stuffcharReadbuff(Ctrl_O);
   if (mod_mask) {
     const char buf[] = { (char)K_SPECIAL, (char)KS_MODIFIER,
                          (char)(uint8_t)mod_mask, NUL };
     stuffReadbuffLen(buf, 3);
   }
   stuffcharReadbuff(c);
   return true;
 }
 return false;
}

// <Insert> key in Insert mode: toggle insert/replace mode.
static void ins_insert(int replaceState)
{
 set_vim_var_string(VV_INSERTMODE, ((State & REPLACE_FLAG)
                                    ? "i"
                                    : replaceState == MODE_VREPLACE ? "v" : "r"), 1);
 ins_apply_autocmds(EVENT_INSERTCHANGE);
 if (State & REPLACE_FLAG) {
   State = MODE_INSERT | (State & MODE_LANGMAP);
 } else {
   State = replaceState | (State & MODE_LANGMAP);
 }
 may_trigger_modechanged();
 AppendCharToRedobuff(K_INS);
 showmode();
 ui_cursor_shape();            // may show different cursor shape
}

// Pressed CTRL-O in Insert mode.
static void ins_ctrl_o(void)
{
 restart_VIsual_select = 0;
 if (State & VREPLACE_FLAG) {
   restart_edit = 'V';
 } else if (State & REPLACE_FLAG) {
   restart_edit = 'R';
 } else {
   restart_edit = 'I';
 }
 if (virtual_active(curwin)) {
   ins_at_eol = false;         // cursor always keeps its column
 } else {
   ins_at_eol = (gchar_cursor() == NUL);
 }
}

// If the cursor is on an indent, ^T/^D insert/delete one
// shiftwidth.  Otherwise ^T/^D behave like a "<<" or ">>".
// Always round the indent to 'shiftwidth', this is compatible
// with vi.  But vi only supports ^T and ^D after an
// autoindent, we support it everywhere.
static void ins_shift(int c, int lastc)
{
 if (stop_arrow() == FAIL) {
   return;
 }
 AppendCharToRedobuff(c);

 // 0^D and ^^D: remove all indent.
 if (c == Ctrl_D && (lastc == '0' || lastc == '^')
     && curwin->w_cursor.col > 0) {
   curwin->w_cursor.col--;
   del_char(false);              // delete the '^' or '0'
   // In Replace mode, restore the characters that '^' or '0' replaced.
   if (State & REPLACE_FLAG) {
     replace_pop_ins();
   }
   if (lastc == '^') {
     old_indent = get_indent();        // remember curr. indent
   }
   change_indent(INDENT_SET, 0, true, true);
 } else {
   change_indent(c == Ctrl_D ? INDENT_DEC : INDENT_INC, 0, true, true);
 }

 if (did_ai && *skipwhite(get_cursor_line_ptr()) != NUL) {
   did_ai = false;
 }
 did_si = false;
 can_si = false;
 can_si_back = false;
 can_cindent = false;          // no cindenting after ^D or ^T
}

static void ins_del(void)
{
 if (stop_arrow() == FAIL) {
   return;
 }
 if (gchar_cursor() == NUL) {          // delete newline
   const int temp = curwin->w_cursor.col;
   if (!can_bs(BS_EOL)  // only if "eol" included
       || do_join(2, false, true, false, false) == FAIL) {
     vim_beep(kOptBoFlagBackspace);
   } else {
     curwin->w_cursor.col = temp;
     // Adjust orig_line_count in case more lines have been deleted than
     // have been added. That makes sure, that open_line() later
     // can access all buffer lines correctly
     if (State & VREPLACE_FLAG
         && orig_line_count > curbuf->b_ml.ml_line_count) {
       orig_line_count = curbuf->b_ml.ml_line_count;
     }
   }
 } else if (del_char(false) == FAIL) {  // delete char under cursor
   vim_beep(kOptBoFlagBackspace);
 }
 did_ai = false;
 did_si = false;
 can_si = false;
 can_si_back = false;
 AppendCharToRedobuff(K_DEL);
}

/// Handle Backspace, delete-word and delete-line in Insert mode.
///
/// @param          c                 character that was typed
/// @param          mode              backspace mode to use
/// @param[in,out]  inserted_space_p  whether a space was the last
//                                    character inserted
///
/// @return true when backspace was actually used.
static bool ins_bs(int c, int mode, int *inserted_space_p)
 FUNC_ATTR_NONNULL_ARG(3)
{
 int cc;
 int temp = 0;                     // init for GCC
 bool did_backspace = false;
 bool call_fix_indent = false;

 // can't delete anything in an empty file
 // can't backup past first character in buffer
 // can't backup past starting point unless 'backspace' > 1
 // can backup to a previous line if 'backspace' == 0
 if (buf_is_empty(curbuf)
     || (!revins_on
         && ((curwin->w_cursor.lnum == 1 && curwin->w_cursor.col == 0)
             || (!can_bs(BS_START)
                 && ((arrow_used && !bt_prompt(curbuf))
                     || (curwin->w_cursor.lnum == Insstart_orig.lnum
                         && curwin->w_cursor.col <= Insstart_orig.col)))
             || (!can_bs(BS_INDENT) && !arrow_used && ai_col > 0
                 && curwin->w_cursor.col <= ai_col)
             || (!can_bs(BS_EOL) && curwin->w_cursor.col == 0)))) {
   vim_beep(kOptBoFlagBackspace);
   return false;
 }

 if (stop_arrow() == FAIL) {
   return false;
 }
 bool in_indent = inindent(0);
 if (in_indent) {
   can_cindent = false;
 }
 end_comment_pending = NUL;  // After BS, don't auto-end comment
 if (revins_on) {            // put cursor after last inserted char
   inc_cursor();
 }
 // Virtualedit:
 //    BACKSPACE_CHAR eats a virtual space
 //    BACKSPACE_WORD eats all coladd
 //    BACKSPACE_LINE eats all coladd and keeps going
 if (curwin->w_cursor.coladd > 0) {
   if (mode == BACKSPACE_CHAR) {
     curwin->w_cursor.coladd--;
     return true;
   }
   if (mode == BACKSPACE_WORD) {
     curwin->w_cursor.coladd = 0;
     return true;
   }
   curwin->w_cursor.coladd = 0;
 }

 // Delete newline!
 if (curwin->w_cursor.col == 0) {
   linenr_T lnum = Insstart.lnum;
   if (curwin->w_cursor.lnum == lnum || revins_on) {
     if (u_save((linenr_T)(curwin->w_cursor.lnum - 2),
                (linenr_T)(curwin->w_cursor.lnum + 1)) == FAIL) {
       return false;
     }
     Insstart.lnum--;
     Insstart.col = ml_get_len(Insstart.lnum);
   }
   // In replace mode:
   // cc < 0: NL was inserted, delete it
   // cc >= 0: NL was replaced, put original characters back
   cc = -1;
   if (State & REPLACE_FLAG) {
     cc = replace_pop_if_nul();  // returns -1 if NL was inserted
   }
   // In replace mode, in the line we started replacing, we only move the
   // cursor.
   if ((State & REPLACE_FLAG) && curwin->w_cursor.lnum <= lnum) {
     dec_cursor();
   } else {
     if (!(State & VREPLACE_FLAG)
         || curwin->w_cursor.lnum > orig_line_count) {
       temp = gchar_cursor();          // remember current char
       curwin->w_cursor.lnum--;

       // When "aw" is in 'formatoptions' we must delete the space at
       // the end of the line, otherwise the line will be broken
       // again when auto-formatting.
       if (has_format_option(FO_AUTO)
           && has_format_option(FO_WHITE_PAR)) {
         const char *ptr = ml_get_buf(curbuf, curwin->w_cursor.lnum);
         int len = get_cursor_line_len();
         if (len > 0 && ptr[len - 1] == ' ') {
           char *newp = xmemdupz(ptr, (size_t)(len - 1));

           if (curbuf->b_ml.ml_flags & (ML_LINE_DIRTY | ML_ALLOCATED)) {
             xfree(curbuf->b_ml.ml_line_ptr);
           }
           curbuf->b_ml.ml_line_ptr = newp;
           curbuf->b_ml.ml_line_textlen--;
           curbuf->b_ml.ml_flags |= ML_LINE_DIRTY;
         }
       }

       do_join(2, false, false, false, false);
       if (temp == NUL && gchar_cursor() != NUL) {
         inc_cursor();
       }
     } else {
       dec_cursor();
     }

     // In MODE_REPLACE mode we have to put back the text that was
     // replaced by the NL. On the replace stack is first a
     // NUL-terminated sequence of characters that were deleted and then
     // the characters that NL replaced.
     if (State & REPLACE_FLAG) {
       // Do the next ins_char() in MODE_NORMAL state, to
       // prevent ins_char() from replacing characters and
       // avoiding showmatch().
       int oldState = State;
       State = MODE_NORMAL;
       // restore characters (blanks) deleted after cursor
       while (cc > 0) {
         colnr_T save_col = curwin->w_cursor.col;
         mb_replace_pop_ins();
         curwin->w_cursor.col = save_col;
         cc = replace_pop_if_nul();
       }
       // restore the characters that NL replaced
       replace_pop_ins();
       State = oldState;
     }
   }
   did_ai = false;
 } else {
   // Delete character(s) before the cursor.
   if (revins_on) {            // put cursor on last inserted char
     dec_cursor();
   }
   colnr_T mincol = 0;
   // keep indent
   if (mode == BACKSPACE_LINE
       && (curbuf->b_p_ai || cindent_on())
       && !revins_on) {
     colnr_T save_col = curwin->w_cursor.col;
     beginline(BL_WHITE);
     if (curwin->w_cursor.col < save_col) {
       mincol = curwin->w_cursor.col;
       // should now fix the indent to match with the previous line
       call_fix_indent = true;
     }
     curwin->w_cursor.col = save_col;
   }

   // Handle deleting one 'shiftwidth' or 'softtabstop'.
   if (mode == BACKSPACE_CHAR
       && ((p_sta && in_indent)
           || ((get_sts_value() != 0 || tabstop_count(curbuf->b_p_vsts_array))
               && curwin->w_cursor.col > 0
               && (*(get_cursor_pos_ptr() - 1) == TAB
                   || (*(get_cursor_pos_ptr() - 1) == ' '
                       && (!*inserted_space_p || arrow_used)))))) {
     *inserted_space_p = false;

     bool const use_ts = !curwin->w_p_list || curwin->w_p_lcs_chars.tab1;
     char *const line = get_cursor_line_ptr();
     char *const cursor_ptr = line + curwin->w_cursor.col;

     colnr_T vcol = 0;
     colnr_T space_vcol = 0;
     StrCharInfo sci = utf_ptr2StrCharInfo(line);
     StrCharInfo space_sci = sci;
     bool prev_space = false;

     // Compute virtual column of cursor position, and find the last
     // whitespace before cursor that is preceded by non-whitespace.
     // Use charsize_nowrap() so that virtual text and wrapping are ignored.
     while (sci.ptr < cursor_ptr) {
       bool cur_space = ascii_iswhite(sci.chr.value);
       if (!prev_space && cur_space) {
         space_sci = sci;
         space_vcol = vcol;
       }
       vcol += charsize_nowrap(curbuf, sci.ptr, use_ts, vcol, sci.chr.value);
       sci = utfc_next(sci);
       prev_space = cur_space;
     }

     // Compute the virtual column where we want to be.
     colnr_T want_vcol = vcol > 0 ? vcol - 1 : 0;
     if (p_sta && in_indent) {
       want_vcol -= want_vcol % get_sw_value(curbuf);
     } else {
       want_vcol = tabstop_start(want_vcol, get_sts_value(), curbuf->b_p_vsts_array);
     }

     // Find the position to stop backspacing.
     // Use charsize_nowrap() so that virtual text and wrapping are ignored.
     while (true) {
       int size = charsize_nowrap(curbuf, space_sci.ptr, use_ts, space_vcol, space_sci.chr.value);
       if (space_vcol + size > want_vcol) {
         break;
       }
       space_vcol += size;
       space_sci = utfc_next(space_sci);
     }
     colnr_T const want_col = (int)(space_sci.ptr - line);

     // Delete characters until we are at or before want_col.
     while (curwin->w_cursor.col > want_col) {
       dec_cursor();
       if (State & REPLACE_FLAG) {
         // Don't delete characters before the insert point when in Replace mode.
         if (curwin->w_cursor.lnum != Insstart.lnum
             || curwin->w_cursor.col >= Insstart.col) {
           replace_do_bs(-1);
         }
       } else {
         del_char(false);
       }
     }

     // Insert extra spaces until we are at want_vcol.
     for (; space_vcol < want_vcol; space_vcol++) {
       // Remember the first char we inserted.
       if (curwin->w_cursor.lnum == Insstart_orig.lnum
           && curwin->w_cursor.col < Insstart_orig.col) {
         Insstart_orig.col = curwin->w_cursor.col;
       }

       if (State & VREPLACE_FLAG) {
         ins_char(' ');
       } else {
         ins_str(S_LEN(" "));
         if ((State & REPLACE_FLAG)) {
           replace_push_nul();
         }
       }
     }
   } else {
     // Delete up to starting point, start of line or previous word.

     int cclass = mb_get_class(get_cursor_pos_ptr());
     do {
       if (!revins_on) {   // put cursor on char to be deleted
         dec_cursor();
       }
       cc = gchar_cursor();
       // look multi-byte character class
       int prev_cclass = cclass;
       cclass = mb_get_class(get_cursor_pos_ptr());
       if (mode == BACKSPACE_WORD && !ascii_isspace(cc)) {   // start of word?
         mode = BACKSPACE_WORD_NOT_SPACE;
         temp = vim_iswordc(cc);
       } else if (mode == BACKSPACE_WORD_NOT_SPACE
                  && ((ascii_isspace(cc) || vim_iswordc(cc) != temp)
                      || prev_cclass != cclass)) {   // end of word?
         if (!revins_on) {
           inc_cursor();
         } else if (State & REPLACE_FLAG) {
           dec_cursor();
         }
         break;
       }
       if (State & REPLACE_FLAG) {
         replace_do_bs(-1);
       } else {
         bool has_composing = false;
         if (p_deco) {
           char *p0 = get_cursor_pos_ptr();
           has_composing = utf_composinglike(p0, p0 + utf_ptr2len(p0), NULL);
         }
         del_char(false);
         // If there are combining characters and 'delcombine' is set
         // move the cursor back.  Don't back up before the base character.
         if (has_composing) {
           inc_cursor();
         }
         if (revins_chars) {
           revins_chars--;
           revins_legal++;
         }
         if (revins_on && gchar_cursor() == NUL) {
           break;
         }
       }
       // Just a single backspace?:
       if (mode == BACKSPACE_CHAR) {
         break;
       }
     } while (revins_on
              || (curwin->w_cursor.col > mincol
                  && (can_bs(BS_NOSTOP)
                      || (curwin->w_cursor.lnum != Insstart_orig.lnum
                          || curwin->w_cursor.col != Insstart_orig.col))));
   }
   did_backspace = true;
 }
 did_si = false;
 can_si = false;
 can_si_back = false;
 if (curwin->w_cursor.col <= 1) {
   did_ai = false;
 }

 if (call_fix_indent) {
   fix_indent();
 }

 // It's a little strange to put backspaces into the redo
 // buffer, but it makes auto-indent a lot easier to deal
 // with.
 AppendCharToRedobuff(c);

 // If deleted before the insertion point, adjust it
 if (curwin->w_cursor.lnum == Insstart_orig.lnum
     && curwin->w_cursor.col < Insstart_orig.col) {
   Insstart_orig.col = curwin->w_cursor.col;
 }

 // vi behaviour: the cursor moves backward but the character that
 //               was there remains visible
 // Vim behaviour: the cursor moves backward and the character that
 //                was there is erased from the screen.
 // We can emulate the vi behaviour by pretending there is a dollar
 // displayed even when there isn't.
 //  --pkv Sun Jan 19 01:56:40 EST 2003
 if (vim_strchr(p_cpo, CPO_BACKSPACE) != NULL && dollar_vcol == -1) {
   dollar_vcol = curwin->w_virtcol;
 }

 // When deleting a char the cursor line must never be in a closed fold.
 // E.g., when 'foldmethod' is indent and deleting the first non-white
 // char before a Tab.
 if (did_backspace) {
   foldOpenCursor();
 }
 return did_backspace;
}

static void ins_left(void)
{
 const bool end_change = dont_sync_undo == kFalse;  // end undoable change

 if ((fdo_flags & kOptFdoFlagHor) && KeyTyped) {
   foldOpenCursor();
 }
 undisplay_dollar();
 pos_T tpos = curwin->w_cursor;
 if (oneleft() == OK) {
   start_arrow_with_change(&tpos, end_change);
   if (!end_change) {
     AppendCharToRedobuff(K_LEFT);
   }
   // If exit reversed string, position is fixed
   if (revins_scol != -1 && (int)curwin->w_cursor.col >= revins_scol) {
     revins_legal++;
   }
   revins_chars++;
 } else if (vim_strchr(p_ww, '[') != NULL && curwin->w_cursor.lnum > 1) {
   // if 'whichwrap' set for cursor in insert mode may go to previous line.
   // always break undo when moving upwards/downwards, else undo may break
   start_arrow(&tpos);
   curwin->w_cursor.lnum--;
   coladvance(curwin, MAXCOL);
   curwin->w_set_curswant = true;  // so we stay at the end
 } else {
   vim_beep(kOptBoFlagCursor);
 }
 dont_sync_undo = kFalse;
}

static void ins_home(int c)
{
 if ((fdo_flags & kOptFdoFlagHor) && KeyTyped) {
   foldOpenCursor();
 }
 undisplay_dollar();
 pos_T tpos = curwin->w_cursor;
 if (c == K_C_HOME) {
   curwin->w_cursor.lnum = 1;
 }
 curwin->w_cursor.col = 0;
 curwin->w_cursor.coladd = 0;
 curwin->w_curswant = 0;
 start_arrow(&tpos);
}

static void ins_end(int c)
{
 if ((fdo_flags & kOptFdoFlagHor) && KeyTyped) {
   foldOpenCursor();
 }
 undisplay_dollar();
 pos_T tpos = curwin->w_cursor;
 if (c == K_C_END) {
   curwin->w_cursor.lnum = curbuf->b_ml.ml_line_count;
 }
 coladvance(curwin, MAXCOL);
 curwin->w_curswant = MAXCOL;

 start_arrow(&tpos);
}

static void ins_s_left(void)
{
 const bool end_change = dont_sync_undo == kFalse;  // end undoable change
 if ((fdo_flags & kOptFdoFlagHor) && KeyTyped) {
   foldOpenCursor();
 }
 undisplay_dollar();
 if (curwin->w_cursor.lnum > 1 || curwin->w_cursor.col > 0) {
   start_arrow_with_change(&curwin->w_cursor, end_change);
   if (!end_change) {
     AppendCharToRedobuff(K_S_LEFT);
   }
   bck_word(1, false, false);
   curwin->w_set_curswant = true;
 } else {
   vim_beep(kOptBoFlagCursor);
 }
 dont_sync_undo = kFalse;
}

/// @param end_change      end undoable change
static void ins_right(void)
{
 const bool end_change = dont_sync_undo == kFalse;  // end undoable change
 if ((fdo_flags & kOptFdoFlagHor) && KeyTyped) {
   foldOpenCursor();
 }
 undisplay_dollar();
 if (gchar_cursor() != NUL || virtual_active(curwin)) {
   start_arrow_with_change(&curwin->w_cursor, end_change);
   if (!end_change) {
     AppendCharToRedobuff(K_RIGHT);
   }
   curwin->w_set_curswant = true;
   if (virtual_active(curwin)) {
     oneright();
   } else {
     curwin->w_cursor.col += utfc_ptr2len(get_cursor_pos_ptr());
   }

   revins_legal++;
   if (revins_chars) {
     revins_chars--;
   }
 } else if (vim_strchr(p_ww, ']') != NULL
            && curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count) {
   // if 'whichwrap' set for cursor in insert mode, may move the
   // cursor to the next line
   start_arrow(&curwin->w_cursor);
   curwin->w_set_curswant = true;
   curwin->w_cursor.lnum++;
   curwin->w_cursor.col = 0;
 } else {
   vim_beep(kOptBoFlagCursor);
 }
 dont_sync_undo = kFalse;
}

static void ins_s_right(void)
{
 const bool end_change = dont_sync_undo == kFalse;  // end undoable change
 if ((fdo_flags & kOptFdoFlagHor) && KeyTyped) {
   foldOpenCursor();
 }
 undisplay_dollar();
 if (curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count
     || gchar_cursor() != NUL) {
   start_arrow_with_change(&curwin->w_cursor, end_change);
   if (!end_change) {
     AppendCharToRedobuff(K_S_RIGHT);
   }
   fwd_word(1, false, 0);
   curwin->w_set_curswant = true;
 } else {
   vim_beep(kOptBoFlagCursor);
 }
 dont_sync_undo = kFalse;
}

/// @param startcol  when true move to Insstart.col
static void ins_up(bool startcol)
{
 linenr_T old_topline = curwin->w_topline;
 int old_topfill = curwin->w_topfill;

 undisplay_dollar();
 pos_T tpos = curwin->w_cursor;
 if (cursor_up(1, true) == OK) {
   if (startcol) {
     coladvance(curwin, getvcol_nolist(&Insstart));
   }
   if (old_topline != curwin->w_topline
       || old_topfill != curwin->w_topfill) {
     redraw_later(curwin, UPD_VALID);
   }
   start_arrow(&tpos);
   can_cindent = true;
 } else {
   vim_beep(kOptBoFlagCursor);
 }
}

static void ins_pageup(void)
{
 undisplay_dollar();

 if (mod_mask & MOD_MASK_CTRL) {
   // <C-PageUp>: tab page back
   if (first_tabpage->tp_next != NULL) {
     start_arrow(&curwin->w_cursor);
     goto_tabpage(-1);
   }
   return;
 }

 pos_T tpos = curwin->w_cursor;
 if (pagescroll(BACKWARD, 1, false) == OK) {
   start_arrow(&tpos);
   can_cindent = true;
 } else {
   vim_beep(kOptBoFlagCursor);
 }
}

/// @param startcol  when true move to Insstart.col
static void ins_down(bool startcol)
{
 linenr_T old_topline = curwin->w_topline;
 int old_topfill = curwin->w_topfill;

 undisplay_dollar();
 pos_T tpos = curwin->w_cursor;
 if (cursor_down(1, true) == OK) {
   if (startcol) {
     coladvance(curwin, getvcol_nolist(&Insstart));
   }
   if (old_topline != curwin->w_topline
       || old_topfill != curwin->w_topfill) {
     redraw_later(curwin, UPD_VALID);
   }
   start_arrow(&tpos);
   can_cindent = true;
 } else {
   vim_beep(kOptBoFlagCursor);
 }
}

static void ins_pagedown(void)
{
 undisplay_dollar();

 if (mod_mask & MOD_MASK_CTRL) {
   // <C-PageDown>: tab page forward
   if (first_tabpage->tp_next != NULL) {
     start_arrow(&curwin->w_cursor);
     goto_tabpage(0);
   }
   return;
 }

 pos_T tpos = curwin->w_cursor;
 if (pagescroll(FORWARD, 1, false) == OK) {
   start_arrow(&tpos);
   can_cindent = true;
 } else {
   vim_beep(kOptBoFlagCursor);
 }
}

/// Handle TAB in Insert or Replace mode.
///
/// @return true when the TAB needs to be inserted like a normal character.
static bool ins_tab(void)
 FUNC_ATTR_WARN_UNUSED_RESULT
{
 int temp;

 if (Insstart_blank_vcol == MAXCOL && curwin->w_cursor.lnum == Insstart.lnum) {
   Insstart_blank_vcol = get_nolist_virtcol();
 }
 if (echeck_abbr(TAB + ABBR_OFF)) {
   return false;
 }

 bool ind = inindent(0);
 if (ind) {
   can_cindent = false;
 }

 // When nothing special, insert TAB like a normal character.
 if (!curbuf->b_p_et
     && !(
          p_sta
          && ind
          // These five lines mean 'tabstop' != 'shiftwidth'
          && ((tabstop_count(curbuf->b_p_vts_array) > 1)
              || (tabstop_count(curbuf->b_p_vts_array) == 1
                  && tabstop_first(curbuf->b_p_vts_array)
                  != get_sw_value(curbuf))
              || (tabstop_count(curbuf->b_p_vts_array) == 0
                  && curbuf->b_p_ts != get_sw_value(curbuf))))
     && tabstop_count(curbuf->b_p_vsts_array) == 0 && get_sts_value() == 0) {
   return true;
 }

 if (stop_arrow() == FAIL) {
   return true;
 }

 did_ai = false;
 did_si = false;
 can_si = false;
 can_si_back = false;
 AppendToRedobuff("\t");

 if (p_sta && ind) {  // insert tab in indent, use 'shiftwidth'
   temp = get_sw_value(curbuf);
   temp -= get_nolist_virtcol() % temp;
 } else if (tabstop_count(curbuf->b_p_vsts_array) > 0
            || curbuf->b_p_sts != 0) {
   // use 'softtabstop' when set
   temp = tabstop_padding(get_nolist_virtcol(),
                          get_sts_value(),
                          curbuf->b_p_vsts_array);
 } else {
   // otherwise use 'tabstop'
   temp = tabstop_padding(get_nolist_virtcol(),
                          curbuf->b_p_ts,
                          curbuf->b_p_vts_array);
 }

 // Insert the first space with ins_char().    It will delete one char in
 // replace mode.  Insert the rest with ins_str(); it will not delete any
 // chars.  For MODE_VREPLACE state, we use ins_char() for all characters.
 ins_char(' ');
 while (--temp > 0) {
   if (State & VREPLACE_FLAG) {
     ins_char(' ');
   } else {
     ins_str(S_LEN(" "));
     if (State & REPLACE_FLAG) {            // no char replaced
       replace_push_nul();
     }
   }
 }

 // When 'expandtab' not set: Replace spaces by TABs where possible.
 if (!curbuf->b_p_et && (tabstop_count(curbuf->b_p_vsts_array) > 0
                         || get_sts_value() > 0
                         || (p_sta && ind))) {
   char *ptr;
   char *saved_line = NULL;         // init for GCC
   pos_T pos;
   pos_T *cursor;
   colnr_T want_vcol, vcol;
   int change_col = -1;
   int save_list = curwin->w_p_list;

   // Get the current line.  For MODE_VREPLACE state, don't make real
   // changes yet, just work on a copy of the line.
   if (State & VREPLACE_FLAG) {
     pos = curwin->w_cursor;
     cursor = &pos;
     saved_line = xstrnsave(get_cursor_line_ptr(), (size_t)get_cursor_line_len());
     ptr = saved_line + pos.col;
   } else {
     ptr = get_cursor_pos_ptr();
     cursor = &curwin->w_cursor;
   }

   // When 'L' is not in 'cpoptions' a tab always takes up 'ts' spaces.
   if (vim_strchr(p_cpo, CPO_LISTWM) == NULL) {
     curwin->w_p_list = false;
   }

   // Find first white before the cursor
   pos_T fpos = curwin->w_cursor;
   while (fpos.col > 0 && ascii_iswhite(ptr[-1])) {
     fpos.col--;
     ptr--;
   }

   // In Replace mode, don't change characters before the insert point.
   if ((State & REPLACE_FLAG)
       && fpos.lnum == Insstart.lnum
       && fpos.col < Insstart.col) {
     ptr += Insstart.col - fpos.col;
     fpos.col = Insstart.col;
   }

   // compute virtual column numbers of first white and cursor
   getvcol(curwin, &fpos, &vcol, NULL, NULL);
   getvcol(curwin, cursor, &want_vcol, NULL, NULL);

   char *tab = "\t";
   int32_t tab_v = (uint8_t)(*tab);

   CharsizeArg csarg;
   CSType cstype = init_charsize_arg(&csarg, curwin, 0, tab);

   // Use as many TABs as possible.  Beware of 'breakindent', 'showbreak'
   // and 'linebreak' adding extra virtual columns.
   while (ascii_iswhite(*ptr)) {
     int i = win_charsize(cstype, vcol, tab, tab_v, &csarg).width;
     if (vcol + i > want_vcol) {
       break;
     }
     if (*ptr != TAB) {
       *ptr = TAB;
       if (change_col < 0) {
         change_col = fpos.col;            // Column of first change
         // May have to adjust Insstart
         if (fpos.lnum == Insstart.lnum && fpos.col < Insstart.col) {
           Insstart.col = fpos.col;
         }
       }
     }
     fpos.col++;
     ptr++;
     vcol += i;
   }

   if (change_col >= 0) {
     int repl_off = 0;
     // Skip over the spaces we need.
     cstype = init_charsize_arg(&csarg, curwin, 0, ptr);
     while (vcol < want_vcol && *ptr == ' ') {
       vcol += win_charsize(cstype, vcol, ptr, (uint8_t)(' '), &csarg).width;
       ptr++;
       repl_off++;
     }

     if (vcol > want_vcol) {
       // Must have a char with 'showbreak' just before it.
       ptr--;
       repl_off--;
     }
     fpos.col += repl_off;

     // Delete following spaces.
     int i = cursor->col - fpos.col;
     if (i > 0) {
       if (!(State & VREPLACE_FLAG)) {
         const colnr_T newp_len = curbuf->b_ml.ml_line_textlen - i;
         char *newp = xmalloc((size_t)newp_len);
         ptrdiff_t col = ptr - curbuf->b_ml.ml_line_ptr;
         if (col > 0) {
           memmove(newp, ptr - col, (size_t)col);
         }
         memmove(newp + col, ptr + i, (size_t)(newp_len - col));
         if (curbuf->b_ml.ml_flags & (ML_LINE_DIRTY | ML_ALLOCATED)) {
           xfree(curbuf->b_ml.ml_line_ptr);
         }
         curbuf->b_ml.ml_line_ptr = newp;
         curbuf->b_ml.ml_line_textlen = newp_len;
         curbuf->b_ml.ml_flags = (curbuf->b_ml.ml_flags | ML_LINE_DIRTY) & ~ML_EMPTY;
         inserted_bytes(fpos.lnum, change_col,
                        cursor->col - change_col, fpos.col - change_col);
       } else {
         STRMOVE(ptr, ptr + i);
       }
       // correct replace stack.
       if ((State & REPLACE_FLAG) && !(State & VREPLACE_FLAG)) {
         for (temp = i; --temp >= 0;) {
           replace_join(repl_off);
         }
       }
     }
     cursor->col -= i;

     // In MODE_VREPLACE state, we haven't changed anything yet.  Do it
     // now by backspacing over the changed spacing and then inserting
     // the new spacing.
     if (State & VREPLACE_FLAG) {
       // Backspace from real cursor to change_col
       backspace_until_column(change_col);

       // Insert each char in saved_line from changed_col to
       // ptr-cursor
       ins_bytes_len(saved_line + change_col, (size_t)(cursor->col - change_col));
     }
   }

   if (State & VREPLACE_FLAG) {
     xfree(saved_line);
   }
   curwin->w_p_list = save_list;
 }

 return false;
}

/// Handle CR or NL in insert mode.
///
/// @return false when it can't undo.
bool ins_eol(int c)
{
 if (echeck_abbr(c + ABBR_OFF)) {
   return true;
 }
 if (stop_arrow() == FAIL) {
   return false;
 }
 undisplay_dollar();

 // Strange Vi behaviour: In Replace mode, typing a NL will not delete the
 // character under the cursor.  Only push a NUL on the replace stack,
 // nothing to put back when the NL is deleted.
 if ((State & REPLACE_FLAG) && !(State & VREPLACE_FLAG)) {
   replace_push_nul();
 }

 // In MODE_VREPLACE state, a NL replaces the rest of the line, and starts
 // replacing the next line, so we push all of the characters left on the
 // line onto the replace stack.  This is not done here though, it is done
 // in open_line().

 // Put cursor on NUL if on the last char and coladd is 1 (happens after
 // CTRL-O).
 if (virtual_active(curwin) && curwin->w_cursor.coladd > 0) {
   coladvance(curwin, getviscol());
 }

 // NL in reverse insert will always start in the end of current line.
 if (revins_on) {
   curwin->w_cursor.col += get_cursor_pos_len();
 }

 AppendToRedobuff(NL_STR);
 bool i = open_line(FORWARD,
                    has_format_option(FO_RET_COMS) ? OPENLINE_DO_COM : 0,
                    old_indent, NULL);
 old_indent = 0;
 can_cindent = true;
 // When inserting a line the cursor line must never be in a closed fold.
 foldOpenCursor();

 return i;
}

// Handle digraph in insert mode.
// Returns character still to be inserted, or NUL when nothing remaining to be
// done.
static int ins_digraph(void)
{
 bool did_putchar = false;

 pc_status = PC_STATUS_UNSET;
 if (redrawing() && !char_avail()) {
   // may need to redraw when no more chars available now
   ins_redraw(false);

   edit_putchar('?', true);
   did_putchar = true;
   add_to_showcmd_c(Ctrl_K);
 }

 // don't map the digraph chars. This also prevents the
 // mode message to be deleted when ESC is hit
 no_mapping++;
 allow_keys++;
 int c = plain_vgetc();
 no_mapping--;
 allow_keys--;
 if (did_putchar) {
   // when the line fits in 'columns' the '?' is at the start of the next
   // line and will not be removed by the redraw
   edit_unputchar();
 }

 if (IS_SPECIAL(c) || mod_mask) {          // special key
   clear_showcmd();
   insert_special(c, true, false);
   return NUL;
 }
 if (c != ESC) {
   did_putchar = false;
   if (redrawing() && !char_avail()) {
     // may need to redraw when no more chars available now
     ins_redraw(false);

     if (char2cells(c) == 1) {
       ins_redraw(false);
       edit_putchar(c, true);
       did_putchar = true;
     }
     add_to_showcmd_c(c);
   }
   no_mapping++;
   allow_keys++;
   int cc = plain_vgetc();
   no_mapping--;
   allow_keys--;
   if (did_putchar) {
     // when the line fits in 'columns' the '?' is at the start of the
     // next line and will not be removed by a redraw
     edit_unputchar();
   }
   if (cc != ESC) {
     AppendToRedobuff(CTRL_V_STR);
     c = digraph_get(c, cc, true);
     clear_showcmd();
     return c;
   }
 }
 clear_showcmd();
 return NUL;
}

// Handle CTRL-E and CTRL-Y in Insert mode: copy char from other line.
// Returns the char to be inserted, or NUL if none found.
int ins_copychar(linenr_T lnum)
{
 if (lnum < 1 || lnum > curbuf->b_ml.ml_line_count) {
   vim_beep(kOptBoFlagCopy);
   return NUL;
 }

 // try to advance to the cursor column
 validate_virtcol(curwin);
 int const end_vcol = curwin->w_virtcol;
 char *line = ml_get(lnum);

 CharsizeArg csarg;
 CSType cstype = init_charsize_arg(&csarg, curwin, lnum, line);
 StrCharInfo ci = utf_ptr2StrCharInfo(line);
 int vcol = 0;
 while (vcol < end_vcol && *ci.ptr != NUL) {
   vcol += win_charsize(cstype, vcol, ci.ptr, ci.chr.value, &csarg).width;
   if (vcol > end_vcol) {
     break;
   }
   ci = utfc_next(ci);
 }

 int c = ci.chr.value < 0 ? (uint8_t)(*ci.ptr) : ci.chr.value;
 if (c == NUL) {
   vim_beep(kOptBoFlagCopy);
 }
 return c;
}

// CTRL-Y or CTRL-E typed in Insert mode.
static int ins_ctrl_ey(int tc)
{
 int c = tc;

 if (ctrl_x_mode_scroll()) {
   if (c == Ctrl_Y) {
     scrolldown_clamp();
   } else {
     scrollup_clamp();
   }
   redraw_later(curwin, UPD_VALID);
 } else {
   c = ins_copychar(curwin->w_cursor.lnum + (c == Ctrl_Y ? -1 : 1));
   if (c != NUL) {
     // The character must be taken literally, insert like it
     // was typed after a CTRL-V, and pretend 'textwidth'
     // wasn't set.  Digits, 'o' and 'x' are special after a
     // CTRL-V, don't use it for these.
     if (c < 256 && !isalnum(c)) {
       AppendToRedobuff(CTRL_V_STR);
     }
     OptInt tw_save = curbuf->b_p_tw;
     curbuf->b_p_tw = -1;
     insert_special(c, true, false);
     curbuf->b_p_tw = tw_save;
     revins_chars++;
     revins_legal++;
     c = Ctrl_V;       // pretend CTRL-V is last character
     auto_format(false, true);
   }
 }
 return c;
}

// Get the value that w_virtcol would have when 'list' is off.
// Unless 'cpo' contains the 'L' flag.
colnr_T get_nolist_virtcol(void)
{
 // check validity of cursor in current buffer
 if (curwin->w_buffer == NULL || curwin->w_buffer->b_ml.ml_mfp == NULL
     || curwin->w_cursor.lnum > curwin->w_buffer->b_ml.ml_line_count) {
   return 0;
 }
 if (curwin->w_p_list && vim_strchr(p_cpo, CPO_LISTWM) == NULL) {
   return getvcol_nolist(&curwin->w_cursor);
 }
 validate_virtcol(curwin);
 return curwin->w_virtcol;
}

// Handle the InsertCharPre autocommand.
// "c" is the character that was typed.
// Return a pointer to allocated memory with the replacement string.
// Return NULL to continue inserting "c".
static char *do_insert_char_pre(int c)
{
 char buf[MB_MAXBYTES + 1];
 const int save_State = State;

 if (c == Ctrl_RSB) {
   return NULL;
 }

 // Return quickly when there is nothing to do.
 if (!has_event(EVENT_INSERTCHARPRE)) {
   return NULL;
 }
 size_t buflen = (size_t)utf_char2bytes(c, buf);
 buf[buflen] = NUL;

 // Lock the text to avoid weird things from happening.
 textlock++;
 set_vim_var_string(VV_CHAR, buf, (ptrdiff_t)buflen);  // set v:char

 char *res = NULL;
 if (ins_apply_autocmds(EVENT_INSERTCHARPRE)) {
   // Get the value of v:char.  It may be empty or more than one
   // character.  Only use it when changed, otherwise continue with the
   // original character to avoid breaking autoindent.
   if (strcmp(buf, get_vim_var_str(VV_CHAR)) != 0) {
     res = xstrdup(get_vim_var_str(VV_CHAR));
   }
 }

 set_vim_var_string(VV_CHAR, NULL, -1);
 textlock--;

 // Restore the State, it may have been changed.
 State = save_State;

 return res;
}

bool get_can_cindent(void)
{
 return can_cindent;
}

void set_can_cindent(bool val)
{
 can_cindent = val;
}

/// Trigger "event" and take care of fixing undo.
int ins_apply_autocmds(event_T event)
{
 varnumber_T tick = buf_get_changedtick(curbuf);

 int r = apply_autocmds(event, NULL, NULL, false, curbuf);

 // If u_savesub() was called then we are not prepared to start
 // a new line.  Call u_save() with no contents to fix that.
 // Except when leaving Insert mode.
 if (event != EVENT_INSERTLEAVE && tick != buf_get_changedtick(curbuf)) {
   u_save(curwin->w_cursor.lnum, (linenr_T)(curwin->w_cursor.lnum + 1));
 }

 return r;
}