did_set_string_option(
    int		opt_idx,		// index in options[] table
    char_u	**varp,			// pointer to the option variable
    int		new_value_alloced,	// new value was allocated
    char_u	*oldval,		// previous value of the option
    char	*errbuf,		// buffer for errors, or NULL
    int		opt_flags,		// OPT_LOCAL and/or OPT_GLOBAL
    int		*value_checked)		// value was checked to be save, no
					// need to set P_INSECURE
{
    char	*errmsg = NULL;
    char_u	*s, *p;
    int		did_chartab = FALSE;
    char_u	**gvarp;
    long_u	free_oldval = (get_option_flags(opt_idx) & P_ALLOCED);
#ifdef FEAT_GUI
    // set when changing an option that only requires a redraw in the GUI
    int		redraw_gui_only = FALSE;
#endif
    int		value_changed = FALSE;
#if defined(FEAT_VTP) && defined(FEAT_TERMGUICOLORS)
    int		did_swaptcap = FALSE;
#endif

    // Get the global option to compare with, otherwise we would have to check
    // two values for all local options.
    gvarp = (char_u **)get_option_varp_scope(opt_idx, OPT_GLOBAL);

    // Disallow changing some options from secure mode
    if ((secure
#ifdef HAVE_SANDBOX
		|| sandbox != 0
#endif
		) && (get_option_flags(opt_idx) & P_SECURE))
	errmsg = e_secure;

    // Check for a "normal" directory or file name in some options.  Disallow a
    // path separator (slash and/or backslash), wildcards and characters that
    // are often illegal in a file name. Be more permissive if "secure" is off.
    else if (((get_option_flags(opt_idx) & P_NFNAME)
		    && vim_strpbrk(*varp, (char_u *)(secure
			    ? "/\\*?[|;&<>\r\n" : "/\\*?[<>\r\n")) != NULL)
	  || ((get_option_flags(opt_idx) & P_NDNAME)
		    && vim_strpbrk(*varp, (char_u *)"*?[|;&<>\r\n") != NULL))
	errmsg = e_invarg;

    // 'term'
    else if (varp == &T_NAME)
    {
	if (T_NAME[0] == NUL)
	    errmsg = N_("E529: Cannot set 'term' to empty string");
#ifdef FEAT_GUI
	else if (gui.in_use)
	    errmsg = N_("E530: Cannot change term in GUI");
	else if (term_is_gui(T_NAME))
	    errmsg = N_("E531: Use \":gui\" to start the GUI");
#endif
	else if (set_termname(T_NAME) == FAIL)
	    errmsg = N_("E522: Not found in termcap");
	else
	{
	    // Screen colors may have changed.
	    redraw_later_clear();

	    // Both 'term' and 'ttytype' point to T_NAME, only set the
	    // P_ALLOCED flag on 'term'.
	    opt_idx = findoption((char_u *)"term");
	    free_oldval = (get_option_flags(opt_idx) & P_ALLOCED);
	}
    }

    // 'backupcopy'
    else if (gvarp == &p_bkc)
    {
	char_u		*bkc = p_bkc;
	unsigned int	*flags = &bkc_flags;

	if (opt_flags & OPT_LOCAL)
	{
	    bkc = curbuf->b_p_bkc;
	    flags = &curbuf->b_bkc_flags;
	}

	if ((opt_flags & OPT_LOCAL) && *bkc == NUL)
	    // make the local value empty: use the global value
	    *flags = 0;
	else
	{
	    if (opt_strings_flags(bkc, p_bkc_values, flags, TRUE) != OK)
		errmsg = e_invarg;
	    if ((((int)*flags & BKC_AUTO) != 0)
		    + (((int)*flags & BKC_YES) != 0)
		    + (((int)*flags & BKC_NO) != 0) != 1)
	    {
		// Must have exactly one of "auto", "yes"  and "no".
		(void)opt_strings_flags(oldval, p_bkc_values, flags, TRUE);
		errmsg = e_invarg;
	    }
	}
    }

    // 'backupext' and 'patchmode'
    else if (varp == &p_bex || varp == &p_pm)
    {
	if (STRCMP(*p_bex == '.' ? p_bex + 1 : p_bex,
		     *p_pm == '.' ? p_pm + 1 : p_pm) == 0)
	    errmsg = N_("E589: 'backupext' and 'patchmode' are equal");
    }
#ifdef FEAT_LINEBREAK
    // 'breakindentopt'
    else if (varp == &curwin->w_p_briopt)
    {
	if (briopt_check(curwin) == FAIL)
	    errmsg = e_invarg;
    }
#endif

    // 'isident', 'iskeyword', 'isprint or 'isfname' option: refill g_chartab[]
    // If the new option is invalid, use old value.  'lisp' option: refill
    // g_chartab[] for '-' char
    else if (  varp == &p_isi
	    || varp == &(curbuf->b_p_isk)
	    || varp == &p_isp
	    || varp == &p_isf)
    {
	if (init_chartab() == FAIL)
	{
	    did_chartab = TRUE;	    // need to restore it below
	    errmsg = e_invarg;	    // error in value
	}
    }

    // 'helpfile'
    else if (varp == &p_hf)
    {
	// May compute new values for $VIM and $VIMRUNTIME
	if (didset_vim)
	{
	    vim_setenv((char_u *)"VIM", (char_u *)"");
	    didset_vim = FALSE;
	}
	if (didset_vimruntime)
	{
	    vim_setenv((char_u *)"VIMRUNTIME", (char_u *)"");
	    didset_vimruntime = FALSE;
	}
    }

#ifdef FEAT_SYN_HL
    // 'cursorlineopt'
    else if (varp == &curwin->w_p_culopt
				  || gvarp == &curwin->w_allbuf_opt.wo_culopt)
    {
	if (**varp == NUL || fill_culopt_flags(*varp, curwin) != OK)
	    errmsg = e_invarg;
    }

    // 'colorcolumn'
    else if (varp == &curwin->w_p_cc)
	errmsg = check_colorcolumn(curwin);
#endif

#ifdef FEAT_MULTI_LANG
    // 'helplang'
    else if (varp == &p_hlg)
    {
	// Check for "", "ab", "ab,cd", etc.
	for (s = p_hlg; *s != NUL; s += 3)
	{
	    if (s[1] == NUL || ((s[2] != ',' || s[3] == NUL) && s[2] != NUL))
	    {
		errmsg = e_invarg;
		break;
	    }
	    if (s[2] == NUL)
		break;
	}
    }
#endif

    // 'highlight'
    else if (varp == &p_hl)
    {
	if (highlight_changed() == FAIL)
	    errmsg = e_invarg;	// invalid flags
    }

    // 'nrformats'
    else if (gvarp == &p_nf)
    {
	if (check_opt_strings(*varp, p_nf_values, TRUE) != OK)
	    errmsg = e_invarg;
    }

#ifdef FEAT_SESSION
    // 'sessionoptions'
    else if (varp == &p_ssop)
    {
	if (opt_strings_flags(p_ssop, p_ssop_values, &ssop_flags, TRUE) != OK)
	    errmsg = e_invarg;
	if ((ssop_flags & SSOP_CURDIR) && (ssop_flags & SSOP_SESDIR))
	{
	    // Don't allow both "sesdir" and "curdir".
	    (void)opt_strings_flags(oldval, p_ssop_values, &ssop_flags, TRUE);
	    errmsg = e_invarg;
	}
    }
    // 'viewoptions'
    else if (varp == &p_vop)
    {
	if (opt_strings_flags(p_vop, p_ssop_values, &vop_flags, TRUE) != OK)
	    errmsg = e_invarg;
    }
#endif

    // 'scrollopt'
    else if (varp == &p_sbo)
    {
	if (check_opt_strings(p_sbo, p_scbopt_values, TRUE) != OK)
	    errmsg = e_invarg;
    }

    // 'ambiwidth'
    else if (varp == &p_ambw || varp == &p_emoji)
    {
	if (check_opt_strings(p_ambw, p_ambw_values, FALSE) != OK)
	    errmsg = e_invarg;
	else if (set_chars_option(curwin, &p_fcs) != NULL)
	    errmsg = _("E835: Conflicts with value of 'fillchars'");
	else
	{
	    tabpage_T	*tp;
	    win_T	*wp;

	    FOR_ALL_TAB_WINDOWS(tp, wp)
	    {
		if (set_chars_option(wp, &wp->w_p_lcs) != NULL)
		{
		    errmsg = _("E834: Conflicts with value of 'listchars'");
		    goto ambw_end;
		}
	    }
	}
ambw_end:
	{}
    }

    // 'background'
    else if (varp == &p_bg)
    {
	if (check_opt_strings(p_bg, p_bg_values, FALSE) == OK)
	{
#ifdef FEAT_EVAL
	    int dark = (*p_bg == 'd');
#endif

	    init_highlight(FALSE, FALSE);

#ifdef FEAT_EVAL
	    if (dark != (*p_bg == 'd')
			  && get_var_value((char_u *)"g:colors_name") != NULL)
	    {
		// The color scheme must have set 'background' back to another
		// value, that's not what we want here.  Disable the color
		// scheme and set the colors again.
		do_unlet((char_u *)"g:colors_name", TRUE);
		free_string_option(p_bg);
		p_bg = vim_strsave((char_u *)(dark ? "dark" : "light"));
		check_string_option(&p_bg);
		init_highlight(FALSE, FALSE);
	    }
#endif
#ifdef FEAT_TERMINAL
	    term_update_colors_all();
#endif
	}
	else
	    errmsg = e_invarg;
    }

    // 'wildmode'
    else if (varp == &p_wim)
    {
	if (check_opt_wim() == FAIL)
	    errmsg = e_invarg;
    }

    // 'wildoptions'
    else if (varp == &p_wop)
    {
	if (check_opt_strings(p_wop, p_wop_values, TRUE) != OK)
	    errmsg = e_invarg;
    }

#ifdef FEAT_WAK
    // 'winaltkeys'
    else if (varp == &p_wak)
    {
	if (*p_wak == NUL
		|| check_opt_strings(p_wak, p_wak_values, FALSE) != OK)
	    errmsg = e_invarg;
# ifdef FEAT_MENU
#  ifdef FEAT_GUI_MOTIF
	else if (gui.in_use)
	    gui_motif_set_mnemonics(p_wak[0] == 'y' || p_wak[0] == 'm');
#  else
#   ifdef FEAT_GUI_GTK
	else if (gui.in_use)
	    gui_gtk_set_mnemonics(p_wak[0] == 'y' || p_wak[0] == 'm');
#   endif
#  endif
# endif
    }
#endif

    // 'eventignore'
    else if (varp == &p_ei)
    {
	if (check_ei() == FAIL)
	    errmsg = e_invarg;
    }

    // 'encoding', 'fileencoding', 'termencoding' and 'makeencoding'
    else if (varp == &p_enc || gvarp == &p_fenc || varp == &p_tenc
							   || gvarp == &p_menc)
    {
	if (gvarp == &p_fenc)
	{
	    if (!curbuf->b_p_ma && opt_flags != OPT_GLOBAL)
		errmsg = e_cannot_make_changes_modifiable_is_off;
	    else if (vim_strchr(*varp, ',') != NULL)
		// No comma allowed in 'fileencoding'; catches confusing it
		// with 'fileencodings'.
		errmsg = e_invarg;
	    else
	    {
#ifdef FEAT_TITLE
		// May show a "+" in the title now.
		redraw_titles();
#endif
		// Add 'fileencoding' to the swap file.
		ml_setflags(curbuf);
	    }
	}
	if (errmsg == NULL)
	{
	    // canonize the value, so that STRCMP() can be used on it
	    p = enc_canonize(*varp);
	    if (p != NULL)
	    {
		vim_free(*varp);
		*varp = p;
	    }
	    if (varp == &p_enc)
	    {
		errmsg = mb_init();
#ifdef FEAT_TITLE
		redraw_titles();
#endif
	    }
	}

#if defined(FEAT_GUI_GTK)
	if (errmsg == NULL && varp == &p_tenc && gui.in_use)
	{
	    // GTK+ 2 uses only a single encoding, and that is UTF-8.
	    if (STRCMP(p_tenc, "utf-8") != 0)
		errmsg = N_("E617: Cannot be changed in the GTK+ 2 GUI");
	}
#endif

	if (errmsg == NULL)
	{
#ifdef FEAT_KEYMAP
	    // When 'keymap' is used and 'encoding' changes, reload the keymap
	    // (with another encoding).
	    if (varp == &p_enc && *curbuf->b_p_keymap != NUL)
		(void)keymap_init();
#endif

	    // When 'termencoding' is not empty and 'encoding' changes or when
	    // 'termencoding' changes, need to setup for keyboard input and
	    // display output conversion.
	    if (((varp == &p_enc && *p_tenc != NUL) || varp == &p_tenc))
	    {
		if (convert_setup(&input_conv, p_tenc, p_enc) == FAIL
			|| convert_setup(&output_conv, p_enc, p_tenc) == FAIL)
		{
		    semsg(_("E950: Cannot convert between %s and %s"),
			    p_tenc, p_enc);
		    errmsg = e_invarg;
		}
	    }

#if defined(MSWIN)
	    // $HOME may have characters in active code page.
	    if (varp == &p_enc)
		init_homedir();
#endif
	}
    }

#if defined(FEAT_POSTSCRIPT)
    else if (varp == &p_penc)
    {
	// Canonize printencoding if VIM standard one
	p = enc_canonize(p_penc);
	if (p != NULL)
	{
	    vim_free(p_penc);
	    p_penc = p;
	}
	else
	{
	    // Ensure lower case and '-' for '_'
	    for (s = p_penc; *s != NUL; s++)
	    {
		if (*s == '_')
		    *s = '-';
		else
		    *s = TOLOWER_ASC(*s);
	    }
	}
    }
#endif

#if defined(FEAT_XIM) && defined(FEAT_GUI_GTK)
    else if (varp == &p_imak)
    {
	if (!im_xim_isvalid_imactivate())
	    errmsg = e_invarg;
    }
#endif

#ifdef FEAT_KEYMAP
    else if (varp == &curbuf->b_p_keymap)
    {
	if (!valid_filetype(*varp))
	    errmsg = e_invarg;
	else
	{
	    int	    secure_save = secure;

	    // Reset the secure flag, since the value of 'keymap' has
	    // been checked to be safe.
	    secure = 0;

	    // load or unload key mapping tables
	    errmsg = keymap_init();

	    secure = secure_save;

	    // Since we check the value, there is no need to set P_INSECURE,
	    // even when the value comes from a modeline.
	    *value_checked = TRUE;
	}

	if (errmsg == NULL)
	{
	    if (*curbuf->b_p_keymap != NUL)
	    {
		// Installed a new keymap, switch on using it.
		curbuf->b_p_iminsert = B_IMODE_LMAP;
		if (curbuf->b_p_imsearch != B_IMODE_USE_INSERT)
		    curbuf->b_p_imsearch = B_IMODE_LMAP;
	    }
	    else
	    {
		// Cleared the keymap, may reset 'iminsert' and 'imsearch'.
		if (curbuf->b_p_iminsert == B_IMODE_LMAP)
		    curbuf->b_p_iminsert = B_IMODE_NONE;
		if (curbuf->b_p_imsearch == B_IMODE_LMAP)
		    curbuf->b_p_imsearch = B_IMODE_USE_INSERT;
	    }
	    if ((opt_flags & OPT_LOCAL) == 0)
	    {
		set_iminsert_global();
		set_imsearch_global();
	    }
	    status_redraw_curbuf();
	}
    }
#endif

    // 'fileformat'
    else if (gvarp == &p_ff)
    {
	if (!curbuf->b_p_ma && !(opt_flags & OPT_GLOBAL))
	    errmsg = e_cannot_make_changes_modifiable_is_off;
	else if (check_opt_strings(*varp, p_ff_values, FALSE) != OK)
	    errmsg = e_invarg;
	else
	{
	    // may also change 'textmode'
	    if (get_fileformat(curbuf) == EOL_DOS)
		curbuf->b_p_tx = TRUE;
	    else
		curbuf->b_p_tx = FALSE;
#ifdef FEAT_TITLE
	    redraw_titles();
#endif
	    // update flag in swap file
	    ml_setflags(curbuf);
	    // Redraw needed when switching to/from "mac": a CR in the text
	    // will be displayed differently.
	    if (get_fileformat(curbuf) == EOL_MAC || *oldval == 'm')
		redraw_curbuf_later(NOT_VALID);
	}
    }

    // 'fileformats'
    else if (varp == &p_ffs)
    {
	if (check_opt_strings(p_ffs, p_ff_values, TRUE) != OK)
	    errmsg = e_invarg;
	else
	{
	    // also change 'textauto'
	    if (*p_ffs == NUL)
		p_ta = FALSE;
	    else
		p_ta = TRUE;
	}
    }

#if defined(FEAT_CRYPT)
    // 'cryptkey'
    else if (gvarp == &p_key)
    {
	// Make sure the ":set" command doesn't show the new value in the
	// history.
	remove_key_from_history();

	if (STRCMP(curbuf->b_p_key, oldval) != 0)
	    // Need to update the swapfile.
	{
	    ml_set_crypt_key(curbuf, oldval,
			      *curbuf->b_p_cm == NUL ? p_cm : curbuf->b_p_cm);
	    changed_internal();
	}
    }

    else if (gvarp == &p_cm)
    {
	if (opt_flags & OPT_LOCAL)
	    p = curbuf->b_p_cm;
	else
	    p = p_cm;
	if (check_opt_strings(p, p_cm_values, TRUE) != OK)
	    errmsg = e_invarg;
	else if (crypt_self_test() == FAIL)
	    errmsg = e_invarg;
	else
	{
	    // When setting the global value to empty, make it "zip".
	    if (*p_cm == NUL)
	    {
		if (new_value_alloced)
		    free_string_option(p_cm);
		p_cm = vim_strsave((char_u *)"zip");
		new_value_alloced = TRUE;
	    }
	    // When using ":set cm=name" the local value is going to be empty.
	    // Do that here, otherwise the crypt functions will still use the
	    // local value.
	    if ((opt_flags & (OPT_LOCAL | OPT_GLOBAL)) == 0)
	    {
		free_string_option(curbuf->b_p_cm);
		curbuf->b_p_cm = empty_option;
	    }

	    // Need to update the swapfile when the effective method changed.
	    // Set "s" to the effective old value, "p" to the effective new
	    // method and compare.
	    if ((opt_flags & OPT_LOCAL) && *oldval == NUL)
		s = p_cm;  // was previously using the global value
	    else
		s = oldval;
	    if (*curbuf->b_p_cm == NUL)
		p = p_cm;  // is now using the global value
	    else
		p = curbuf->b_p_cm;
	    if (STRCMP(s, p) != 0)
		ml_set_crypt_key(curbuf, curbuf->b_p_key, s);

	    // If the global value changes need to update the swapfile for all
	    // buffers using that value.
	    if ((opt_flags & OPT_GLOBAL) && STRCMP(p_cm, oldval) != 0)
	    {
		buf_T	*buf;

		FOR_ALL_BUFFERS(buf)
		    if (buf != curbuf && *buf->b_p_cm == NUL)
			ml_set_crypt_key(buf, buf->b_p_key, oldval);
	    }
	}
    }
#endif

    // 'matchpairs'
    else if (gvarp == &p_mps)
    {
	if (has_mbyte)
	{
	    for (p = *varp; *p != NUL; ++p)
	    {
		int x2 = -1;
		int x3 = -1;

		if (*p != NUL)
		    p += mb_ptr2len(p);
		if (*p != NUL)
		    x2 = *p++;
		if (*p != NUL)
		{
		    x3 = mb_ptr2char(p);
		    p += mb_ptr2len(p);
		}
		if (x2 != ':' || x3 == -1 || (*p != NUL && *p != ','))
		{
		    errmsg = e_invarg;
		    break;
		}
		if (*p == NUL)
		    break;
	    }
	}
	else
	{
	    // Check for "x:y,x:y"
	    for (p = *varp; *p != NUL; p += 4)
	    {
		if (p[1] != ':' || p[2] == NUL || (p[3] != NUL && p[3] != ','))
		{
		    errmsg = e_invarg;
		    break;
		}
		if (p[3] == NUL)
		    break;
	    }
	}
    }

    // 'comments'
    else if (gvarp == &p_com)
    {
	for (s = *varp; *s; )
	{
	    while (*s && *s != ':')
	    {
		if (vim_strchr((char_u *)COM_ALL, *s) == NULL
					     && !VIM_ISDIGIT(*s) && *s != '-')
		{
		    errmsg = illegal_char(errbuf, *s);
		    break;
		}
		++s;
	    }
	    if (*s++ == NUL)
		errmsg = N_("E524: Missing colon");
	    else if (*s == ',' || *s == NUL)
		errmsg = N_("E525: Zero length string");
	    if (errmsg != NULL)
		break;
	    while (*s && *s != ',')
	    {
		if (*s == '\\' && s[1] != NUL)
		    ++s;
		++s;
	    }
	    s = skip_to_option_part(s);
	}
    }

    // global 'listchars'
    else if (varp == &p_lcs)
    {
	errmsg = set_chars_option(curwin, varp);
	if (errmsg == NULL)
	{
	    tabpage_T	*tp;
	    win_T		*wp;

	    // The current window is set to use the global 'listchars' value.
	    // So clear the window-local value.
	    if (!(opt_flags & OPT_GLOBAL))
		clear_string_option(&curwin->w_p_lcs);
	    FOR_ALL_TAB_WINDOWS(tp, wp)
	    {
		errmsg = set_chars_option(wp, &wp->w_p_lcs);
		if (errmsg)
		    break;
	    }
	    redraw_all_later(NOT_VALID);
	}
    }

    // local 'listchars'
    else if (varp == &curwin->w_p_lcs)
	errmsg = set_chars_option(curwin, varp);

    // 'fillchars'
    else if (varp == &p_fcs)
    {
	errmsg = set_chars_option(curwin, varp);
    }

#ifdef FEAT_CMDWIN
    // 'cedit'
    else if (varp == &p_cedit)
    {
	errmsg = check_cedit();
    }
#endif

    // 'verbosefile'
    else if (varp == &p_vfile)
    {
	verbose_stop();
	if (*p_vfile != NUL && verbose_open() == FAIL)
	    errmsg = e_invarg;
    }

#ifdef FEAT_VIMINFO
    // 'viminfo'
    else if (varp == &p_viminfo)
    {
	for (s = p_viminfo; *s;)
	{
	    // Check it's a valid character
	    if (vim_strchr((char_u *)"!\"%'/:<@cfhnrs", *s) == NULL)
	    {
		errmsg = illegal_char(errbuf, *s);
		break;
	    }
	    if (*s == 'n')	// name is always last one
		break;
	    else if (*s == 'r') // skip until next ','
	    {
		while (*++s && *s != ',')
		    ;
	    }
	    else if (*s == '%')
	    {
		// optional number
		while (vim_isdigit(*++s))
		    ;
	    }
	    else if (*s == '!' || *s == 'h' || *s == 'c')
		++s;		// no extra chars
	    else		// must have a number
	    {
		while (vim_isdigit(*++s))
		    ;

		if (!VIM_ISDIGIT(*(s - 1)))
		{
		    if (errbuf != NULL)
		    {
			sprintf(errbuf, _("E526: Missing number after <%s>"),
						    transchar_byte(*(s - 1)));
			errmsg = errbuf;
		    }
		    else
			errmsg = "";
		    break;
		}
	    }
	    if (*s == ',')
		++s;
	    else if (*s)
	    {
		if (errbuf != NULL)
		    errmsg = N_("E527: Missing comma");
		else
		    errmsg = "";
		break;
	    }
	}
	if (*p_viminfo && errmsg == NULL && get_viminfo_parameter('\'') < 0)
	    errmsg = N_("E528: Must specify a ' value");
    }
#endif // FEAT_VIMINFO

    // terminal options
    else if (istermoption_idx(opt_idx) && full_screen)
    {
	// ":set t_Co=0" and ":set t_Co=1" do ":set t_Co="
	if (varp == &T_CCO)
	{
	    int colors = atoi((char *)T_CCO);

	    // Only reinitialize colors if t_Co value has really changed to
	    // avoid expensive reload of colorscheme if t_Co is set to the
	    // same value multiple times.
	    if (colors != t_colors)
	    {
		t_colors = colors;
		if (t_colors <= 1)
		{
		    if (new_value_alloced)
			vim_free(T_CCO);
		    T_CCO = empty_option;
		}
#if defined(FEAT_VTP) && defined(FEAT_TERMGUICOLORS)
		if (is_term_win32())
		{
		    swap_tcap();
		    did_swaptcap = TRUE;
		}
#endif
		// We now have a different color setup, initialize it again.
		init_highlight(TRUE, FALSE);
	    }
	}
	ttest(FALSE);
	if (varp == &T_ME)
	{
	    out_str(T_ME);
	    redraw_later(CLEAR);
#if defined(MSWIN) && (!defined(FEAT_GUI_MSWIN) || defined(VIMDLL))
	    // Since t_me has been set, this probably means that the user
	    // wants to use this as default colors.  Need to reset default
	    // background/foreground colors.
# ifdef VIMDLL
	    if (!gui.in_use && !gui.starting)
# endif
		mch_set_normal_colors();
#endif
	}
	if (varp == &T_BE && termcap_active)
	{
#ifdef FEAT_JOB_CHANNEL
	    ch_log_output = TRUE;
#endif
	    if (*T_BE == NUL)
		// When clearing t_BE we assume the user no longer wants
		// bracketed paste, thus disable it by writing t_BD.
		out_str(T_BD);
	    else
		out_str(T_BE);
	}
    }

#ifdef FEAT_LINEBREAK
    // 'showbreak'
    else if (gvarp == &p_sbr)
    {
	for (s = *varp; *s; )
	{
	    if (ptr2cells(s) != 1)
		errmsg = N_("E595: 'showbreak' contains unprintable or wide character");
	    MB_PTR_ADV(s);
	}
    }
#endif

#ifdef FEAT_GUI
    // 'guifont'
    else if (varp == &p_guifont)
    {
	if (gui.in_use)
	{
	    p = p_guifont;
# if defined(FEAT_GUI_GTK)
	    // Put up a font dialog and let the user select a new value.
	    // If this is cancelled go back to the old value but don't
	    // give an error message.
	    if (STRCMP(p, "*") == 0)
	    {
		p = gui_mch_font_dialog(oldval);

		if (new_value_alloced)
		    free_string_option(p_guifont);

		p_guifont = (p != NULL) ? p : vim_strsave(oldval);
		new_value_alloced = TRUE;
	    }
# endif
	    if (p != NULL && gui_init_font(p_guifont, FALSE) != OK)
	    {
# if defined(FEAT_GUI_MSWIN) || defined(FEAT_GUI_PHOTON)
		if (STRCMP(p_guifont, "*") == 0)
		{
		    // Dialog was cancelled: Keep the old value without giving
		    // an error message.
		    if (new_value_alloced)
			free_string_option(p_guifont);
		    p_guifont = vim_strsave(oldval);
		    new_value_alloced = TRUE;
		}
		else
# endif
		    errmsg = N_("E596: Invalid font(s)");
	    }
	}
	redraw_gui_only = TRUE;
    }
# ifdef FEAT_XFONTSET
    else if (varp == &p_guifontset)
    {
	if (STRCMP(p_guifontset, "*") == 0)
	    errmsg = N_("E597: can't select fontset");
	else if (gui.in_use && gui_init_font(p_guifontset, TRUE) != OK)
	    errmsg = N_("E598: Invalid fontset");
	redraw_gui_only = TRUE;
    }
# endif
    else if (varp == &p_guifontwide)
    {
	if (STRCMP(p_guifontwide, "*") == 0)
	    errmsg = N_("E533: can't select wide font");
	else if (gui_get_wide_font() == FAIL)
	    errmsg = N_("E534: Invalid wide font");
	redraw_gui_only = TRUE;
    }
#endif

#ifdef CURSOR_SHAPE
    // 'guicursor'
    else if (varp == &p_guicursor)
	errmsg = parse_shape_opt(SHAPE_CURSOR);
#endif

#ifdef FEAT_MOUSESHAPE
    // 'mouseshape'
    else if (varp == &p_mouseshape)
    {
	errmsg = parse_shape_opt(SHAPE_MOUSE);
	update_mouseshape(-1);
    }
#endif

#ifdef FEAT_PRINTER
    else if (varp == &p_popt)
	errmsg = parse_printoptions();
# if defined(FEAT_POSTSCRIPT)
    else if (varp == &p_pmfn)
	errmsg = parse_printmbfont();
# endif
#endif

#ifdef FEAT_LANGMAP
    // 'langmap'
    else if (varp == &p_langmap)
	langmap_set();
#endif

#ifdef FEAT_LINEBREAK
    // 'breakat'
    else if (varp == &p_breakat)
	fill_breakat_flags();
#endif

#ifdef FEAT_TITLE
    // 'titlestring' and 'iconstring'
    else if (varp == &p_titlestring || varp == &p_iconstring)
    {
# ifdef FEAT_STL_OPT
	int	flagval = (varp == &p_titlestring) ? STL_IN_TITLE : STL_IN_ICON;

	// NULL => statusline syntax
	if (vim_strchr(*varp, '%') && check_stl_option(*varp) == NULL)
	    stl_syntax |= flagval;
	else
	    stl_syntax &= ~flagval;
# endif
	did_set_title();
    }
#endif

#ifdef FEAT_GUI
    // 'guioptions'
    else if (varp == &p_go)
    {
	gui_init_which_components(oldval);
	redraw_gui_only = TRUE;
    }
#endif

#if defined(FEAT_GUI_TABLINE)
    // 'guitablabel'
    else if (varp == &p_gtl)
    {
	redraw_tabline = TRUE;
	redraw_gui_only = TRUE;
    }
    // 'guitabtooltip'
    else if (varp == &p_gtt)
    {
	redraw_gui_only = TRUE;
    }
#endif

#if defined(UNIX) || defined(VMS)
    // 'ttymouse'
    else if (varp == &p_ttym)
    {
	// Switch the mouse off before changing the escape sequences used for
	// that.
	mch_setmouse(FALSE);
	if (opt_strings_flags(p_ttym, p_ttym_values, &ttym_flags, FALSE) != OK)
	    errmsg = e_invarg;
	else
	    check_mouse_termcode();
	if (termcap_active)
	    setmouse();		// may switch it on again
    }
#endif

    // 'selection'
    else if (varp == &p_sel)
    {
	if (*p_sel == NUL
		|| check_opt_strings(p_sel, p_sel_values, FALSE) != OK)
	    errmsg = e_invarg;
    }

    // 'selectmode'
    else if (varp == &p_slm)
    {
	if (check_opt_strings(p_slm, p_slm_values, TRUE) != OK)
	    errmsg = e_invarg;
    }

#ifdef FEAT_BROWSE
    // 'browsedir'
    else if (varp == &p_bsdir)
    {
	if (check_opt_strings(p_bsdir, p_bsdir_values, FALSE) != OK
		&& !mch_isdir(p_bsdir))
	    errmsg = e_invarg;
    }
#endif

    // 'keymodel'
    else if (varp == &p_km)
    {
	if (check_opt_strings(p_km, p_km_values, TRUE) != OK)
	    errmsg = e_invarg;
	else
	{
	    km_stopsel = (vim_strchr(p_km, 'o') != NULL);
	    km_startsel = (vim_strchr(p_km, 'a') != NULL);
	}
    }

    // 'mousemodel'
    else if (varp == &p_mousem)
    {
	if (check_opt_strings(p_mousem, p_mousem_values, FALSE) != OK)
	    errmsg = e_invarg;
#if defined(FEAT_GUI_MOTIF) && defined(FEAT_MENU) && (XmVersion <= 1002)
	else if (*p_mousem != *oldval)
	    // Changed from "extend" to "popup" or "popup_setpos" or vv: need
	    // to create or delete the popup menus.
	    gui_motif_update_mousemodel(root_menu);
#endif
    }

    // 'switchbuf'
    else if (varp == &p_swb)
    {
	if (opt_strings_flags(p_swb, p_swb_values, &swb_flags, TRUE) != OK)
	    errmsg = e_invarg;
    }

    // 'debug'
    else if (varp == &p_debug)
    {
	if (check_opt_strings(p_debug, p_debug_values, TRUE) != OK)
	    errmsg = e_invarg;
    }

    // 'display'
    else if (varp == &p_dy)
    {
	if (opt_strings_flags(p_dy, p_dy_values, &dy_flags, TRUE) != OK)
	    errmsg = e_invarg;
	else
	    (void)init_chartab();

    }

    // 'eadirection'
    else if (varp == &p_ead)
    {
	if (check_opt_strings(p_ead, p_ead_values, FALSE) != OK)
	    errmsg = e_invarg;
    }

#ifdef FEAT_CLIPBOARD
    // 'clipboard'
    else if (varp == &p_cb)
	errmsg = check_clipboard_option();
#endif

#ifdef FEAT_SPELL
    // When 'spelllang' or 'spellfile' is set and there is a window for this
    // buffer in which 'spell' is set load the wordlists.
    else if (varp == &(curwin->w_s->b_p_spl)
	    || varp == &(curwin->w_s->b_p_spf))
    {
	int	is_spellfile = varp == &(curwin->w_s->b_p_spf);

	if ((is_spellfile && !valid_spellfile(*varp))
	    || (!is_spellfile && !valid_spelllang(*varp)))
	    errmsg = e_invarg;
	else
	    errmsg = did_set_spell_option(is_spellfile);
    }
    // When 'spellcapcheck' is set compile the regexp program.
    else if (varp == &(curwin->w_s->b_p_spc))
    {
	errmsg = compile_cap_prog(curwin->w_s);
    }
    // 'spelloptions'
    else if (varp == &(curwin->w_s->b_p_spo))
    {
	if (**varp != NUL && STRCMP("camel", *varp) != 0)
	    errmsg = e_invarg;
    }
    // 'spellsuggest'
    else if (varp == &p_sps)
    {
	if (spell_check_sps() != OK)
	    errmsg = e_invarg;
    }
    // 'mkspellmem'
    else if (varp == &p_msm)
    {
	if (spell_check_msm() != OK)
	    errmsg = e_invarg;
    }
#endif

    // When 'bufhidden' is set, check for valid value.
    else if (gvarp == &p_bh)
    {
	if (check_opt_strings(curbuf->b_p_bh, p_bufhidden_values, FALSE) != OK)
	    errmsg = e_invarg;
    }

    // When 'buftype' is set, check for valid value.
    else if (gvarp == &p_bt)
    {
	if (check_opt_strings(curbuf->b_p_bt, p_buftype_values, FALSE) != OK)
	    errmsg = e_invarg;
	else
	{
	    if (curwin->w_status_height)
	    {
		curwin->w_redr_status = TRUE;
		redraw_later(VALID);
	    }
	    curbuf->b_help = (curbuf->b_p_bt[0] == 'h');
#ifdef FEAT_TITLE
	    redraw_titles();
#endif
	}
    }

#ifdef FEAT_STL_OPT
    // 'statusline' or 'rulerformat'
    else if (gvarp == &p_stl || varp == &p_ruf)
    {
	int wid;

	if (varp == &p_ruf)	// reset ru_wid first
	    ru_wid = 0;
	s = *varp;
	if (varp == &p_ruf && *s == '%')
	{
	    // set ru_wid if 'ruf' starts with "%99("
	    if (*++s == '-')	// ignore a '-'
		s++;
	    wid = getdigits(&s);
	    if (wid && *s == '(' && (errmsg = check_stl_option(p_ruf)) == NULL)
		ru_wid = wid;
	    else
		errmsg = check_stl_option(p_ruf);
	}
	// check 'statusline' only if it doesn't start with "%!"
	else if (varp == &p_ruf || s[0] != '%' || s[1] != '!')
	    errmsg = check_stl_option(s);
	if (varp == &p_ruf && errmsg == NULL)
	    comp_col();
    }
#endif

    // check if it is a valid value for 'complete' -- Acevedo
    else if (gvarp == &p_cpt)
    {
	for (s = *varp; *s;)
	{
	    while (*s == ',' || *s == ' ')
		s++;
	    if (!*s)
		break;
	    if (vim_strchr((char_u *)".wbuksid]tU", *s) == NULL)
	    {
		errmsg = illegal_char(errbuf, *s);
		break;
	    }
	    if (*++s != NUL && *s != ',' && *s != ' ')
	    {
		if (s[-1] == 'k' || s[-1] == 's')
		{
		    // skip optional filename after 'k' and 's'
		    while (*s && *s != ',' && *s != ' ')
		    {
			if (*s == '\\' && s[1] != NUL)
			    ++s;
			++s;
		    }
		}
		else
		{
		    if (errbuf != NULL)
		    {
			sprintf((char *)errbuf,
				     _("E535: Illegal character after <%c>"),
				     *--s);
			errmsg = errbuf;
		    }
		    else
			errmsg = "";
		    break;
		}
	    }
	}
    }

    // 'completeopt'
    else if (varp == &p_cot)
    {
	if (check_opt_strings(p_cot, p_cot_values, TRUE) != OK)
	    errmsg = e_invarg;
	else
	    completeopt_was_set();
    }

#ifdef BACKSLASH_IN_FILENAME
    // 'completeslash'
    else if (gvarp == &p_csl)
    {
	if (check_opt_strings(p_csl, p_csl_values, FALSE) != OK
		|| check_opt_strings(curbuf->b_p_csl, p_csl_values, FALSE) != OK)
	    errmsg = e_invarg;
    }
#endif

#ifdef FEAT_SIGNS
    // 'signcolumn'
    else if (varp == &curwin->w_p_scl)
    {
	if (check_opt_strings(*varp, p_scl_values, FALSE) != OK)
	    errmsg = e_invarg;
	// When changing the 'signcolumn' to or from 'number', recompute the
	// width of the number column if 'number' or 'relativenumber' is set.
	if (((*oldval == 'n' && *(oldval + 1) == 'u')
		|| (*curwin->w_p_scl == 'n' && *(curwin->w_p_scl + 1) =='u'))
		&& (curwin->w_p_nu || curwin->w_p_rnu))
	    curwin->w_nrwidth_line_count = 0;
    }
#endif


#if defined(FEAT_TOOLBAR) && !defined(FEAT_GUI_MSWIN)
    // 'toolbar'
    else if (varp == &p_toolbar)
    {
	if (opt_strings_flags(p_toolbar, p_toolbar_values,
			      &toolbar_flags, TRUE) != OK)
	    errmsg = e_invarg;
	else
	{
	    out_flush();
	    gui_mch_show_toolbar((toolbar_flags &
				  (TOOLBAR_TEXT | TOOLBAR_ICONS)) != 0);
	}
    }
#endif

#if defined(FEAT_TOOLBAR) && defined(FEAT_GUI_GTK)
    // 'toolbariconsize': GTK+ 2 only
    else if (varp == &p_tbis)
    {
	if (opt_strings_flags(p_tbis, p_tbis_values, &tbis_flags, FALSE) != OK)
	    errmsg = e_invarg;
	else
	{
	    out_flush();
	    gui_mch_show_toolbar((toolbar_flags &
				  (TOOLBAR_TEXT | TOOLBAR_ICONS)) != 0);
	}
    }
#endif

    // 'pastetoggle': translate key codes like in a mapping
    else if (varp == &p_pt)
    {
	if (*p_pt)
	{
	    (void)replace_termcodes(p_pt, &p,
				      REPTERM_FROM_PART | REPTERM_DO_LT, NULL);
	    if (p != NULL)
	    {
		if (new_value_alloced)
		    free_string_option(p_pt);
		p_pt = p;
		new_value_alloced = TRUE;
	    }
	}
    }

    // 'backspace'
    else if (varp == &p_bs)
    {
	if (VIM_ISDIGIT(*p_bs))
	{
	    if (*p_bs > '3' || p_bs[1] != NUL)
		errmsg = e_invarg;
	}
	else if (check_opt_strings(p_bs, p_bs_values, TRUE) != OK)
	    errmsg = e_invarg;
    }
    else if (varp == &p_bo)
    {
	if (opt_strings_flags(p_bo, p_bo_values, &bo_flags, TRUE) != OK)
	    errmsg = e_invarg;
    }

    // 'tagcase'
    else if (gvarp == &p_tc)
    {
	unsigned int	*flags;

	if (opt_flags & OPT_LOCAL)
	{
	    p = curbuf->b_p_tc;
	    flags = &curbuf->b_tc_flags;
	}
	else
	{
	    p = p_tc;
	    flags = &tc_flags;
	}

	if ((opt_flags & OPT_LOCAL) && *p == NUL)
	    // make the local value empty: use the global value
	    *flags = 0;
	else if (*p == NUL
		|| opt_strings_flags(p, p_tc_values, flags, FALSE) != OK)
	    errmsg = e_invarg;
    }

    // 'casemap'
    else if (varp == &p_cmp)
    {
	if (opt_strings_flags(p_cmp, p_cmp_values, &cmp_flags, TRUE) != OK)
	    errmsg = e_invarg;
    }

#ifdef FEAT_DIFF
    // 'diffopt'
    else if (varp == &p_dip)
    {
	if (diffopt_changed() == FAIL)
	    errmsg = e_invarg;
    }
#endif

#ifdef FEAT_FOLDING
    // 'foldmethod'
    else if (gvarp == &curwin->w_allbuf_opt.wo_fdm)
    {
	if (check_opt_strings(*varp, p_fdm_values, FALSE) != OK
		|| *curwin->w_p_fdm == NUL)
	    errmsg = e_invarg;
	else
	{
	    foldUpdateAll(curwin);
	    if (foldmethodIsDiff(curwin))
		newFoldLevel();
	}
    }
# ifdef FEAT_EVAL
    // 'foldexpr'
    else if (varp == &curwin->w_p_fde)
    {
	if (foldmethodIsExpr(curwin))
	    foldUpdateAll(curwin);
    }
# endif
    // 'foldmarker'
    else if (gvarp == &curwin->w_allbuf_opt.wo_fmr)
    {
	p = vim_strchr(*varp, ',');
	if (p == NULL)
	    errmsg = N_("E536: comma required");
	else if (p == *varp || p[1] == NUL)
	    errmsg = e_invarg;
	else if (foldmethodIsMarker(curwin))
	    foldUpdateAll(curwin);
    }
    // 'commentstring'
    else if (gvarp == &p_cms)
    {
	if (**varp != NUL && strstr((char *)*varp, "%s") == NULL)
	    errmsg = N_("E537: 'commentstring' must be empty or contain %s");
    }
    // 'foldopen'
    else if (varp == &p_fdo)
    {
	if (opt_strings_flags(p_fdo, p_fdo_values, &fdo_flags, TRUE) != OK)
	    errmsg = e_invarg;
    }
    // 'foldclose'
    else if (varp == &p_fcl)
    {
	if (check_opt_strings(p_fcl, p_fcl_values, TRUE) != OK)
	    errmsg = e_invarg;
    }
    // 'foldignore'
    else if (gvarp == &curwin->w_allbuf_opt.wo_fdi)
    {
	if (foldmethodIsIndent(curwin))
	    foldUpdateAll(curwin);
    }
#endif

    // 'virtualedit'
    else if (gvarp == &p_ve)
    {
	char_u		*ve = p_ve;
	unsigned int	*flags = &ve_flags;

	if (opt_flags & OPT_LOCAL)
	{
	    ve = curwin->w_p_ve;
	    flags = &curwin->w_ve_flags;
	}

	if ((opt_flags & OPT_LOCAL) && *ve == NUL)
	    // make the local value empty: use the global value
	    *flags = 0;
	else
	{
	    if (opt_strings_flags(ve, p_ve_values, flags, TRUE) != OK)
		errmsg = e_invarg;
	    else if (STRCMP(p_ve, oldval) != 0)
	    {
		// Recompute cursor position in case the new 've' setting
		// changes something.
		validate_virtcol();
		coladvance(curwin->w_virtcol);
	    }
	}
    }

#if defined(FEAT_CSCOPE) && defined(FEAT_QUICKFIX)
    else if (varp == &p_csqf)
    {
	if (p_csqf != NULL)
	{
	    p = p_csqf;
	    while (*p != NUL)
	    {
		if (vim_strchr((char_u *)CSQF_CMDS, *p) == NULL
			|| p[1] == NUL
			|| vim_strchr((char_u *)CSQF_FLAGS, p[1]) == NULL
			|| (p[2] != NUL && p[2] != ','))
		{
		    errmsg = e_invarg;
		    break;
		}
		else if (p[2] == NUL)
		    break;
		else
		    p += 3;
	    }
	}
    }
#endif

#ifdef FEAT_CINDENT
    // 'cinoptions'
    else if (gvarp == &p_cino)
    {
	// TODO: recognize errors
	parse_cino(curbuf);
    }
#endif

#if defined(FEAT_RENDER_OPTIONS)
    // 'renderoptions'
    else if (varp == &p_rop)
    {
	if (!gui_mch_set_rendering_options(p_rop))
	    errmsg = e_invarg;
    }
#endif

    else if (gvarp == &p_ft)
    {
	if (!valid_filetype(*varp))
	    errmsg = e_invarg;
	else
	{
	    value_changed = STRCMP(oldval, *varp) != 0;

	    // Since we check the value, there is no need to set P_INSECURE,
	    // even when the value comes from a modeline.
	    *value_checked = TRUE;
	}
    }

#ifdef FEAT_SYN_HL
    else if (gvarp == &p_syn)
    {
	if (!valid_filetype(*varp))
	    errmsg = e_invarg;
	else
	{
	    value_changed = STRCMP(oldval, *varp) != 0;

	    // Since we check the value, there is no need to set P_INSECURE,
	    // even when the value comes from a modeline.
	    *value_checked = TRUE;
	}
    }
#endif

#ifdef FEAT_TERMINAL
    // 'termwinkey'
    else if (varp == &curwin->w_p_twk)
    {
	if (*curwin->w_p_twk != NUL
				  && string_to_key(curwin->w_p_twk, TRUE) == 0)
	    errmsg = e_invarg;
    }
    // 'termwinsize'
    else if (varp == &curwin->w_p_tws)
    {
	if (*curwin->w_p_tws != NUL)
	{
	    p = skipdigits(curwin->w_p_tws);
	    if (p == curwin->w_p_tws
		    || (*p != 'x' && *p != '*')
		    || *skipdigits(p + 1) != NUL)
		errmsg = e_invarg;
	}
    }
    // 'wincolor'
    else if (varp == &curwin->w_p_wcr)
    {
	if (curwin->w_buffer->b_term != NULL)
	    term_update_colors(curwin->w_buffer->b_term);
    }
# if defined(MSWIN)
    // 'termwintype'
    else if (varp == &p_twt)
    {
	if (check_opt_strings(*varp, p_twt_values, FALSE) != OK)
	    errmsg = e_invarg;
    }
# endif
#endif

#ifdef FEAT_VARTABS
    // 'varsofttabstop'
    else if (varp == &(curbuf->b_p_vsts))
    {
	char_u *cp;

	if (!(*varp)[0] || ((*varp)[0] == '0' && !(*varp)[1]))
	{
	    if (curbuf->b_p_vsts_array)
	    {
		vim_free(curbuf->b_p_vsts_array);
		curbuf->b_p_vsts_array = 0;
	    }
	}
	else
	{
	    for (cp = *varp; *cp; ++cp)
	    {
		if (vim_isdigit(*cp))
		    continue;
		if (*cp == ',' && cp > *varp && *(cp-1) != ',')
		    continue;
		errmsg = e_invarg;
		break;
	    }
	    if (errmsg == NULL)
	    {
		int *oldarray = curbuf->b_p_vsts_array;
		if (tabstop_set(*varp, &(curbuf->b_p_vsts_array)) == OK)
		{
		    if (oldarray)
			vim_free(oldarray);
		}
		else
		    errmsg = e_invarg;
	    }
	}
    }

    // 'vartabstop'
    else if (varp == &(curbuf->b_p_vts))
    {
	char_u *cp;

	if (!(*varp)[0] || ((*varp)[0] == '0' && !(*varp)[1]))
	{
	    if (curbuf->b_p_vts_array)
	    {
		vim_free(curbuf->b_p_vts_array);
		curbuf->b_p_vts_array = NULL;
	    }
	}
	else
	{
	    for (cp = *varp; *cp; ++cp)
	    {
		if (vim_isdigit(*cp))
		    continue;
		if (*cp == ',' && cp > *varp && *(cp-1) != ',')
		    continue;
		errmsg = e_invarg;
		break;
	    }
	    if (errmsg == NULL)
	    {
		int *oldarray = curbuf->b_p_vts_array;

		if (tabstop_set(*varp, &(curbuf->b_p_vts_array)) == OK)
		{
		    vim_free(oldarray);
#ifdef FEAT_FOLDING
		    if (foldmethodIsIndent(curwin))
			foldUpdateAll(curwin);
#endif
		}
		else
		    errmsg = e_invarg;
	    }
	}
    }
#endif

#ifdef FEAT_PROP_POPUP
    // 'previewpopup'
    else if (varp == &p_pvp)
    {
	if (parse_previewpopup(NULL) == FAIL)
	    errmsg = e_invarg;
    }
# ifdef FEAT_QUICKFIX
    // 'completepopup'
    else if (varp == &p_cpp)
    {
	if (parse_completepopup(NULL) == FAIL)
	    errmsg = e_invarg;
	else
	    popup_close_info();
    }
# endif
#endif

#ifdef FEAT_QUICKFIX
    else if (varp == &p_qftf)
    {
	if (qf_process_qftf_option() == FALSE)
	    errmsg = e_invarg;
    }
#endif

    // Options that are a list of flags.
    else
    {
	p = NULL;
	if (varp == &p_ww) // 'whichwrap'
	    p = (char_u *)WW_ALL;
	if (varp == &p_shm) // 'shortmess'
	    p = (char_u *)SHM_ALL;
	else if (varp == &(p_cpo)) // 'cpoptions'
	    p = (char_u *)CPO_ALL;
	else if (varp == &(curbuf->b_p_fo)) // 'formatoptions'
	    p = (char_u *)FO_ALL;
#ifdef FEAT_CONCEAL
	else if (varp == &curwin->w_p_cocu) // 'concealcursor'
	    p = (char_u *)COCU_ALL;
#endif
	else if (varp == &p_mouse) // 'mouse'
	{
	    p = (char_u *)MOUSE_ALL;
	}
#if defined(FEAT_GUI)
	else if (varp == &p_go) // 'guioptions'
	    p = (char_u *)GO_ALL;
#endif
	if (p != NULL)
	{
	    for (s = *varp; *s; ++s)
		if (vim_strchr(p, *s) == NULL)
		{
		    errmsg = illegal_char(errbuf, *s);
		    break;
		}
	}
    }

    // If error detected, restore the previous value.
    if (errmsg != NULL)
    {
	if (new_value_alloced)
	    free_string_option(*varp);
	*varp = oldval;
	// When resetting some values, need to act on it.
	if (did_chartab)
	    (void)init_chartab();
	if (varp == &p_hl)
	    (void)highlight_changed();
    }
    else
    {
#ifdef FEAT_EVAL
	// Remember where the option was set.
	set_option_sctx_idx(opt_idx, opt_flags, current_sctx);
#endif
	// Free string options that are in allocated memory.
	// Use "free_oldval", because recursiveness may change the flags under
	// our fingers (esp. init_highlight()).
	if (free_oldval)
	    free_string_option(oldval);
	if (new_value_alloced)
	    set_option_flag(opt_idx, P_ALLOCED);
	else
	    clear_option_flag(opt_idx, P_ALLOCED);

	if ((opt_flags & (OPT_LOCAL | OPT_GLOBAL)) == 0
		&& is_global_local_option(opt_idx))
	{
	    // global option with local value set to use global value; free
	    // the local value and make it empty
	    p = get_option_varp_scope(opt_idx, OPT_LOCAL);
	    free_string_option(*(char_u **)p);
	    *(char_u **)p = empty_option;
	}

	// May set global value for local option.
	else if (!(opt_flags & OPT_LOCAL) && opt_flags != OPT_GLOBAL)
	    set_string_option_global(opt_idx, varp);

	// Trigger the autocommand only after setting the flags.
#ifdef FEAT_SYN_HL
	// When 'syntax' is set, load the syntax of that name
	if (varp == &(curbuf->b_p_syn))
	{
	    static int syn_recursive = 0;

	    ++syn_recursive;
	    // Only pass TRUE for "force" when the value changed or not used
	    // recursively, to avoid endless recurrence.
	    apply_autocmds(EVENT_SYNTAX, curbuf->b_p_syn, curbuf->b_fname,
		    value_changed || syn_recursive == 1, curbuf);
	    curbuf->b_flags |= BF_SYN_SET;
	    --syn_recursive;
	}
#endif
	else if (varp == &(curbuf->b_p_ft))
	{
	    // 'filetype' is set, trigger the FileType autocommand.
	    // Skip this when called from a modeline and the filetype was
	    // already set to this value.
	    if (!(opt_flags & OPT_MODELINE) || value_changed)
	    {
		static int  ft_recursive = 0;
		int	    secure_save = secure;

		// Reset the secure flag, since the value of 'filetype' has
		// been checked to be safe.
		secure = 0;

		++ft_recursive;
		did_filetype = TRUE;
		// Only pass TRUE for "force" when the value changed or not
		// used recursively, to avoid endless recurrence.
		apply_autocmds(EVENT_FILETYPE, curbuf->b_p_ft, curbuf->b_fname,
				   value_changed || ft_recursive == 1, curbuf);
		--ft_recursive;
		// Just in case the old "curbuf" is now invalid.
		if (varp != &(curbuf->b_p_ft))
		    varp = NULL;

		secure = secure_save;
	    }
	}
#ifdef FEAT_SPELL
	if (varp == &(curwin->w_s->b_p_spl))
	{
	    char_u	fname[200];
	    char_u	*q = curwin->w_s->b_p_spl;

	    // Skip the first name if it is "cjk".
	    if (STRNCMP(q, "cjk,", 4) == 0)
		q += 4;

	    // Source the spell/LANG.vim in 'runtimepath'.
	    // They could set 'spellcapcheck' depending on the language.
	    // Use the first name in 'spelllang' up to '_region' or
	    // '.encoding'.
	    for (p = q; *p != NUL; ++p)
		if (!ASCII_ISALNUM(*p) && *p != '-')
		    break;
	    if (p > q)
	    {
		vim_snprintf((char *)fname, 200, "spell/%.*s.vim",
							      (int)(p - q), q);
		source_runtime(fname, DIP_ALL);
	    }
	}
#endif
    }

    if (varp == &p_mouse)
    {
	if (*p_mouse == NUL)
	    mch_setmouse(FALSE);    // switch mouse off
	else
	    setmouse();		    // in case 'mouse' changed
    }

#if defined(FEAT_LUA) || defined(PROTO)
    if (varp == &p_rtp)
	update_package_paths_in_lua();
#endif

    if (curwin->w_curswant != MAXCOL
		   && (get_option_flags(opt_idx) & (P_CURSWANT | P_RALL)) != 0)
	curwin->w_set_curswant = TRUE;

    if ((opt_flags & OPT_NO_REDRAW) == 0)
    {
#ifdef FEAT_GUI
	// check redraw when it's not a GUI option or the GUI is active.
	if (!redraw_gui_only || gui.in_use)
#endif
	    check_redraw(get_option_flags(opt_idx));
    }

#if defined(FEAT_VTP) && defined(FEAT_TERMGUICOLORS)
    if (did_swaptcap)
    {
	set_termname((char_u *)"win32");
	init_highlight(TRUE, FALSE);
    }
#endif

    return errmsg;
}