keyboard.c

/* Keyboard and mouse input; editor command loop.
   Copyright (C) 1985, 1986, 1987, 1988, 1989, 1993, 1994, 1995,
                 1996, 1997, 1999, 2000, 2001, 2002, 2003, 2004,
                 2005, 2006 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.  */

#include <config.h>
#include <signal.h>
#include <stdio.h>
#include "termchar.h"
#include "termopts.h"
#include "lisp.h"
#include "termhooks.h"
#include "macros.h"
#include "keyboard.h"
#include "frame.h"
#include "window.h"
#include "commands.h"
#include "buffer.h"
#include "charset.h"
#include "disptab.h"
#include "dispextern.h"
#include "syntax.h"
#include "intervals.h"
#include "keymap.h"
#include "blockinput.h"
#include "puresize.h"
#include "systime.h"
#include "atimer.h"
#include <setjmp.h>
#include <errno.h>

#ifdef HAVE_GTK_AND_PTHREAD
#include <pthread.h>
#endif
#ifdef MSDOS
#include "msdos.h"
#include <time.h>
#else /* not MSDOS */
#ifndef VMS
#include <sys/ioctl.h>
#endif
#endif /* not MSDOS */

#include "syssignal.h"
#include "systty.h"

#include <sys/types.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif

/* This is to get the definitions of the XK_ symbols.  */
#ifdef HAVE_X_WINDOWS
#include "xterm.h"
#endif

#ifdef HAVE_NTGUI
#include "w32term.h"
#endif /* HAVE_NTGUI */

#ifdef MAC_OS
#include "macterm.h"
#endif

#ifndef USE_CRT_DLL
extern int errno;
#endif

/* Variables for blockinput.h: */

/* Non-zero if interrupt input is blocked right now.  */
int interrupt_input_blocked;

/* Nonzero means an input interrupt has arrived
   during the current critical section.  */
int interrupt_input_pending;


/* File descriptor to use for input.  */
extern int input_fd;

#ifdef HAVE_WINDOW_SYSTEM
/* Make all keyboard buffers much bigger when using X windows.  */
#ifdef MAC_OS8
/* But not too big (local data > 32K error) if on Mac OS Classic.  */
#define KBD_BUFFER_SIZE 512
#else
#define KBD_BUFFER_SIZE 4096
#endif
#else	/* No X-windows, character input */
#define KBD_BUFFER_SIZE 4096
#endif	/* No X-windows */

#define abs(x)		((x) >= 0 ? (x) : -(x))

/* Following definition copied from eval.c */

struct backtrace
  {
    struct backtrace *next;
    Lisp_Object *function;
    Lisp_Object *args;	/* Points to vector of args. */
    int nargs;		/* length of vector.  If nargs is UNEVALLED,
			   args points to slot holding list of
			   unevalled args */
    char evalargs;
    /* Nonzero means call value of debugger when done with this operation. */
    char debug_on_exit;
  };

#ifdef MULTI_KBOARD
KBOARD *initial_kboard;
KBOARD *current_kboard;
KBOARD *all_kboards;
int single_kboard;
#else
KBOARD the_only_kboard;
#endif

/* Non-nil disable property on a command means
   do not execute it; call disabled-command-function's value instead.  */
Lisp_Object Qdisabled, Qdisabled_command_function;

#define NUM_RECENT_KEYS (100)
int recent_keys_index;	/* Index for storing next element into recent_keys */
int total_keys;		/* Total number of elements stored into recent_keys */
Lisp_Object recent_keys; /* A vector, holding the last 100 keystrokes */

/* Vector holding the key sequence that invoked the current command.
   It is reused for each command, and it may be longer than the current
   sequence; this_command_key_count indicates how many elements
   actually mean something.
   It's easier to staticpro a single Lisp_Object than an array.  */
Lisp_Object this_command_keys;
int this_command_key_count;

/* 1 after calling Freset_this_command_lengths.
   Usually it is 0.  */
int this_command_key_count_reset;

/* This vector is used as a buffer to record the events that were actually read
   by read_key_sequence.  */
Lisp_Object raw_keybuf;
int raw_keybuf_count;

#define GROW_RAW_KEYBUF							\
 if (raw_keybuf_count == XVECTOR (raw_keybuf)->size)			\
  {									\
    int newsize = 2 * XVECTOR (raw_keybuf)->size;			\
    Lisp_Object new;							\
    new = Fmake_vector (make_number (newsize), Qnil);			\
    bcopy (XVECTOR (raw_keybuf)->contents, XVECTOR (new)->contents,	\
	   raw_keybuf_count * sizeof (Lisp_Object));			\
    raw_keybuf = new;							\
  }

/* Number of elements of this_command_keys
   that precede this key sequence.  */
int this_single_command_key_start;

/* Record values of this_command_key_count and echo_length ()
   before this command was read.  */
static int before_command_key_count;
static int before_command_echo_length;

extern int minbuf_level;

extern int message_enable_multibyte;

extern struct backtrace *backtrace_list;

/* If non-nil, the function that implements the display of help.
   It's called with one argument, the help string to display.  */

Lisp_Object Vshow_help_function;

/* If a string, the message displayed before displaying a help-echo
   in the echo area.  */

Lisp_Object Vpre_help_message;

/* Nonzero means do menu prompting.  */

static int menu_prompting;

/* Character to see next line of menu prompt.  */

static Lisp_Object menu_prompt_more_char;

/* For longjmp to where kbd input is being done.  */

static jmp_buf getcjmp;

/* True while doing kbd input.  */
int waiting_for_input;

/* True while displaying for echoing.   Delays C-g throwing.  */

int echoing;

/* Non-null means we can start echoing at the next input pause even
   though there is something in the echo area.  */

static struct kboard *ok_to_echo_at_next_pause;

/* The kboard last echoing, or null for none.  Reset to 0 in
   cancel_echoing.  If non-null, and a current echo area message
   exists, and echo_message_buffer is eq to the current message
   buffer, we know that the message comes from echo_kboard.  */

struct kboard *echo_kboard;

/* The buffer used for echoing.  Set in echo_now, reset in
   cancel_echoing.  */

Lisp_Object echo_message_buffer;

/* Nonzero means disregard local maps for the menu bar.  */
static int inhibit_local_menu_bar_menus;

/* Nonzero means C-g should cause immediate error-signal.  */
int immediate_quit;

/* The user's ERASE setting.  */
Lisp_Object Vtty_erase_char;

/* Character to recognize as the help char.  */
Lisp_Object Vhelp_char;

/* List of other event types to recognize as meaning "help".  */
Lisp_Object Vhelp_event_list;

/* Form to execute when help char is typed.  */
Lisp_Object Vhelp_form;

/* Command to run when the help character follows a prefix key.  */
Lisp_Object Vprefix_help_command;

/* List of items that should move to the end of the menu bar.  */
Lisp_Object Vmenu_bar_final_items;

/* Non-nil means show the equivalent key-binding for
   any M-x command that has one.
   The value can be a length of time to show the message for.
   If the value is non-nil and not a number, we wait 2 seconds.  */
Lisp_Object Vsuggest_key_bindings;

/* How long to display an echo-area message when the minibuffer is active.
   If the value is not a number, such messages don't time out.  */
Lisp_Object Vminibuffer_message_timeout;

/* Character that causes a quit.  Normally C-g.

   If we are running on an ordinary terminal, this must be an ordinary
   ASCII char, since we want to make it our interrupt character.

   If we are not running on an ordinary terminal, it still needs to be
   an ordinary ASCII char.  This character needs to be recognized in
   the input interrupt handler.  At this point, the keystroke is
   represented as a struct input_event, while the desired quit
   character is specified as a lispy event.  The mapping from struct
   input_events to lispy events cannot run in an interrupt handler,
   and the reverse mapping is difficult for anything but ASCII
   keystrokes.

   FOR THESE ELABORATE AND UNSATISFYING REASONS, quit_char must be an
   ASCII character.  */
int quit_char;

extern Lisp_Object current_global_map;
extern int minibuf_level;

/* If non-nil, this is a map that overrides all other local maps.  */
Lisp_Object Voverriding_local_map;

/* If non-nil, Voverriding_local_map applies to the menu bar.  */
Lisp_Object Voverriding_local_map_menu_flag;

/* Keymap that defines special misc events that should
   be processed immediately at a low level.  */
Lisp_Object Vspecial_event_map;

/* Current depth in recursive edits.  */
int command_loop_level;

/* Total number of times command_loop has read a key sequence.  */
EMACS_INT num_input_keys;

/* Last input character read as a command.  */
Lisp_Object last_command_char;

/* Last input character read as a command, not counting menus
   reached by the mouse.  */
Lisp_Object last_nonmenu_event;

/* Last input character read for any purpose.  */
Lisp_Object last_input_char;

/* If not Qnil, a list of objects to be read as subsequent command input.  */
Lisp_Object Vunread_command_events;

/* If not Qnil, a list of objects to be read as subsequent command input
   including input method processing.  */
Lisp_Object Vunread_input_method_events;

/* If not Qnil, a list of objects to be read as subsequent command input
   but NOT including input method processing.  */
Lisp_Object Vunread_post_input_method_events;

/* If not -1, an event to be read as subsequent command input.  */
EMACS_INT unread_command_char;

/* If not Qnil, this is a switch-frame event which we decided to put
   off until the end of a key sequence.  This should be read as the
   next command input, after any unread_command_events.

   read_key_sequence uses this to delay switch-frame events until the
   end of the key sequence; Fread_char uses it to put off switch-frame
   events until a non-ASCII event is acceptable as input.  */
Lisp_Object unread_switch_frame;

/* A mask of extra modifier bits to put into every keyboard char.  */
EMACS_INT extra_keyboard_modifiers;

/* Char to use as prefix when a meta character is typed in.
   This is bound on entry to minibuffer in case ESC is changed there.  */

Lisp_Object meta_prefix_char;

/* Last size recorded for a current buffer which is not a minibuffer.  */
static int last_non_minibuf_size;

/* Number of idle seconds before an auto-save and garbage collection.  */
static Lisp_Object Vauto_save_timeout;

/* Total number of times read_char has returned.  */
int num_input_events;

/* Total number of times read_char has returned, outside of macros.  */
EMACS_INT num_nonmacro_input_events;

/* Auto-save automatically when this many characters have been typed
   since the last time.  */

static EMACS_INT auto_save_interval;

/* Value of num_nonmacro_input_events as of last auto save.  */

int last_auto_save;

/* The command being executed by the command loop.
   Commands may set this, and the value set will be copied into
   current_kboard->Vlast_command instead of the actual command.  */
Lisp_Object Vthis_command;

/* This is like Vthis_command, except that commands never set it.  */
Lisp_Object real_this_command;

/* If the lookup of the command returns a binding, the original
   command is stored in this-original-command.  It is nil otherwise.  */
Lisp_Object Vthis_original_command;

/* The value of point when the last command was started.  */
int last_point_position;

/* The buffer that was current when the last command was started.  */
Lisp_Object last_point_position_buffer;

/* The window that was selected when the last command was started.  */
Lisp_Object last_point_position_window;

/* The frame in which the last input event occurred, or Qmacro if the
   last event came from a macro.  We use this to determine when to
   generate switch-frame events.  This may be cleared by functions
   like Fselect_frame, to make sure that a switch-frame event is
   generated by the next character.  */
Lisp_Object internal_last_event_frame;

/* A user-visible version of the above, intended to allow users to
   figure out where the last event came from, if the event doesn't
   carry that information itself (i.e. if it was a character).  */
Lisp_Object Vlast_event_frame;

/* The timestamp of the last input event we received from the X server.
   X Windows wants this for selection ownership.  */
unsigned long last_event_timestamp;

Lisp_Object Qself_insert_command;
Lisp_Object Qforward_char;
Lisp_Object Qbackward_char;
Lisp_Object Qundefined;
Lisp_Object Qtimer_event_handler;

/* read_key_sequence stores here the command definition of the
   key sequence that it reads.  */
Lisp_Object read_key_sequence_cmd;

/* Echo unfinished commands after this many seconds of pause.  */
Lisp_Object Vecho_keystrokes;

/* Form to evaluate (if non-nil) when Emacs is started.  */
Lisp_Object Vtop_level;

/* User-supplied table to translate input characters.  */
Lisp_Object Vkeyboard_translate_table;

/* Keymap mapping ASCII function key sequences onto their preferred forms.  */
extern Lisp_Object Vfunction_key_map;

/* Another keymap that maps key sequences into key sequences.
   This one takes precedence over ordinary definitions.  */
extern Lisp_Object Vkey_translation_map;

/* If non-nil, this implements the current input method.  */
Lisp_Object Vinput_method_function;
Lisp_Object Qinput_method_function;

/* When we call Vinput_method_function,
   this holds the echo area message that was just erased.  */
Lisp_Object Vinput_method_previous_message;

/* Non-nil means deactivate the mark at end of this command.  */
Lisp_Object Vdeactivate_mark;

/* Menu bar specified in Lucid Emacs fashion.  */

Lisp_Object Vlucid_menu_bar_dirty_flag;
Lisp_Object Qrecompute_lucid_menubar, Qactivate_menubar_hook;

Lisp_Object Qecho_area_clear_hook;

/* Hooks to run before and after each command.  */
Lisp_Object Qpre_command_hook, Vpre_command_hook;
Lisp_Object Qpost_command_hook, Vpost_command_hook;
Lisp_Object Qcommand_hook_internal, Vcommand_hook_internal;

/* List of deferred actions to be performed at a later time.
   The precise format isn't relevant here; we just check whether it is nil.  */
Lisp_Object Vdeferred_action_list;

/* Function to call to handle deferred actions, when there are any.  */
Lisp_Object Vdeferred_action_function;
Lisp_Object Qdeferred_action_function;

Lisp_Object Qinput_method_exit_on_first_char;
Lisp_Object Qinput_method_use_echo_area;

/* File in which we write all commands we read.  */
FILE *dribble;

/* Nonzero if input is available.  */
int input_pending;

/* 1 if should obey 0200 bit in input chars as "Meta", 2 if should
   keep 0200 bit in input chars.  0 to ignore the 0200 bit.  */

int meta_key;

extern char *pending_malloc_warning;

/* Circular buffer for pre-read keyboard input.  */

static struct input_event kbd_buffer[KBD_BUFFER_SIZE];

/* Pointer to next available character in kbd_buffer.
   If kbd_fetch_ptr == kbd_store_ptr, the buffer is empty.
   This may be kbd_buffer + KBD_BUFFER_SIZE, meaning that the
   next available char is in kbd_buffer[0].  */
static struct input_event *kbd_fetch_ptr;

/* Pointer to next place to store character in kbd_buffer.  This
   may be kbd_buffer + KBD_BUFFER_SIZE, meaning that the next
   character should go in kbd_buffer[0].  */
static struct input_event * volatile kbd_store_ptr;

/* The above pair of variables forms a "queue empty" flag.  When we
   enqueue a non-hook event, we increment kbd_store_ptr.  When we
   dequeue a non-hook event, we increment kbd_fetch_ptr.  We say that
   there is input available iff the two pointers are not equal.

   Why not just have a flag set and cleared by the enqueuing and
   dequeuing functions?  Such a flag could be screwed up by interrupts
   at inopportune times.  */

/* If this flag is non-nil, we check mouse_moved to see when the
   mouse moves, and motion events will appear in the input stream.
   Otherwise, mouse motion is ignored.  */
Lisp_Object do_mouse_tracking;

/* Symbols to head events.  */
Lisp_Object Qmouse_movement;
Lisp_Object Qscroll_bar_movement;
Lisp_Object Qswitch_frame;
Lisp_Object Qdelete_frame;
Lisp_Object Qiconify_frame;
Lisp_Object Qmake_frame_visible;
Lisp_Object Qselect_window;
Lisp_Object Qhelp_echo;

#ifdef HAVE_MOUSE
Lisp_Object Qmouse_fixup_help_message;
#endif

/* Symbols to denote kinds of events.  */
Lisp_Object Qfunction_key;
Lisp_Object Qmouse_click;
#if defined (WINDOWSNT) || defined (MAC_OS)
Lisp_Object Qlanguage_change;
#endif
Lisp_Object Qdrag_n_drop;
Lisp_Object Qsave_session;
#ifdef MAC_OS
Lisp_Object Qmac_apple_event;
#endif

/* Lisp_Object Qmouse_movement; - also an event header */

/* Properties of event headers.  */
Lisp_Object Qevent_kind;
Lisp_Object Qevent_symbol_elements;

/* menu item parts */
Lisp_Object Qmenu_alias;
Lisp_Object Qmenu_enable;
Lisp_Object QCenable, QCvisible, QChelp, QCfilter, QCkeys, QCkey_sequence;
Lisp_Object QCbutton, QCtoggle, QCradio;
extern Lisp_Object Vdefine_key_rebound_commands;
extern Lisp_Object Qmenu_item;

/* An event header symbol HEAD may have a property named
   Qevent_symbol_element_mask, which is of the form (BASE MODIFIERS);
   BASE is the base, unmodified version of HEAD, and MODIFIERS is the
   mask of modifiers applied to it.  If present, this is used to help
   speed up parse_modifiers.  */
Lisp_Object Qevent_symbol_element_mask;

/* An unmodified event header BASE may have a property named
   Qmodifier_cache, which is an alist mapping modifier masks onto
   modified versions of BASE.  If present, this helps speed up
   apply_modifiers.  */
Lisp_Object Qmodifier_cache;

/* Symbols to use for parts of windows.  */
Lisp_Object Qmode_line;
Lisp_Object Qvertical_line;
Lisp_Object Qvertical_scroll_bar;
Lisp_Object Qmenu_bar;
extern Lisp_Object Qleft_margin, Qright_margin;
extern Lisp_Object Qleft_fringe, Qright_fringe;
extern Lisp_Object QCmap;

Lisp_Object recursive_edit_unwind (), command_loop ();
Lisp_Object Fthis_command_keys ();
Lisp_Object Qextended_command_history;
EMACS_TIME timer_check ();

extern Lisp_Object Vhistory_length, Vtranslation_table_for_input;

extern char *x_get_keysym_name ();

static void record_menu_key ();
static int echo_length ();

Lisp_Object Qpolling_period;

/* List of absolute timers.  Appears in order of next scheduled event.  */
Lisp_Object Vtimer_list;

/* List of idle time timers.  Appears in order of next scheduled event.  */
Lisp_Object Vtimer_idle_list;

/* Incremented whenever a timer is run.  */
int timers_run;

extern Lisp_Object Vprint_level, Vprint_length;

/* Address (if not 0) of EMACS_TIME to zero out if a SIGIO interrupt
   happens.  */
EMACS_TIME *input_available_clear_time;

/* Nonzero means use SIGIO interrupts; zero means use CBREAK mode.
   Default is 1 if INTERRUPT_INPUT is defined.  */
int interrupt_input;

/* Nonzero while interrupts are temporarily deferred during redisplay.  */
int interrupts_deferred;

/* Nonzero means use ^S/^Q for flow control.  */
int flow_control;

/* Allow m- file to inhibit use of FIONREAD.  */
#ifdef BROKEN_FIONREAD
#undef FIONREAD
#endif

/* We are unable to use interrupts if FIONREAD is not available,
   so flush SIGIO so we won't try.  */
#if !defined (FIONREAD)
#ifdef SIGIO
#undef SIGIO
#endif
#endif

/* If we support a window system, turn on the code to poll periodically
   to detect C-g.  It isn't actually used when doing interrupt input.  */
#if defined(HAVE_WINDOW_SYSTEM) && !defined(USE_ASYNC_EVENTS)
#define POLL_FOR_INPUT
#endif

/* After a command is executed, if point is moved into a region that
   has specific properties (e.g. composition, display), we adjust
   point to the boundary of the region.  But, if a command sets this
   variable to non-nil, we suppress this point adjustment.  This
   variable is set to nil before reading a command.  */

Lisp_Object Vdisable_point_adjustment;

/* If non-nil, always disable point adjustment.  */

Lisp_Object Vglobal_disable_point_adjustment;

/* The time when Emacs started being idle.  */

static EMACS_TIME timer_idleness_start_time;

/* After Emacs stops being idle, this saves the last value
   of timer_idleness_start_time from when it was idle.  */

static EMACS_TIME timer_last_idleness_start_time;


/* Global variable declarations.  */

/* Flags for readable_events.  */
#define READABLE_EVENTS_DO_TIMERS_NOW		(1 << 0)
#define READABLE_EVENTS_FILTER_EVENTS		(1 << 1)
#define READABLE_EVENTS_IGNORE_SQUEEZABLES	(1 << 2)

/* Function for init_keyboard to call with no args (if nonzero).  */
void (*keyboard_init_hook) ();

static int read_avail_input P_ ((int));
static void get_input_pending P_ ((int *, int));
static int readable_events P_ ((int));
static Lisp_Object read_char_x_menu_prompt P_ ((int, Lisp_Object *,
						Lisp_Object, int *));
static Lisp_Object read_char_x_menu_prompt ();
static Lisp_Object read_char_minibuf_menu_prompt P_ ((int, int,
						      Lisp_Object *));
static Lisp_Object make_lispy_event P_ ((struct input_event *));
#ifdef HAVE_MOUSE
static Lisp_Object make_lispy_movement P_ ((struct frame *, Lisp_Object,
					    enum scroll_bar_part,
					    Lisp_Object, Lisp_Object,
					    unsigned long));
#endif
static Lisp_Object modify_event_symbol P_ ((int, unsigned, Lisp_Object,
					    Lisp_Object, char **,
					    Lisp_Object *, unsigned));
static Lisp_Object make_lispy_switch_frame P_ ((Lisp_Object));
static int parse_solitary_modifier P_ ((Lisp_Object));
static int parse_solitary_modifier ();
static void save_getcjmp P_ ((jmp_buf));
static void save_getcjmp ();
static void restore_getcjmp P_ ((jmp_buf));
static Lisp_Object apply_modifiers P_ ((int, Lisp_Object));
static void clear_event P_ ((struct input_event *));
static void any_kboard_state P_ ((void));
static SIGTYPE interrupt_signal P_ ((int signalnum));
static void timer_start_idle P_ ((void));
static void timer_stop_idle P_ ((void));
static void timer_resume_idle P_ ((void));

/* Nonzero means don't try to suspend even if the operating system seems
   to support it.  */
static int cannot_suspend;

extern Lisp_Object Qidentity, Qonly;

/* Install the string STR as the beginning of the string of echoing,
   so that it serves as a prompt for the next character.
   Also start echoing.  */

void
echo_prompt (str)
     Lisp_Object str;
{
  current_kboard->echo_string = str;
  current_kboard->echo_after_prompt = SCHARS (str);
  echo_now ();
}

/* Add C to the echo string, if echoing is going on.
   C can be a character, which is printed prettily ("M-C-x" and all that
   jazz), or a symbol, whose name is printed.  */

void
echo_char (c)
     Lisp_Object c;
{
  if (current_kboard->immediate_echo)
    {
      int size = KEY_DESCRIPTION_SIZE + 100;
      char *buffer = (char *) alloca (size);
      char *ptr = buffer;
      Lisp_Object echo_string;

      echo_string = current_kboard->echo_string;

      /* If someone has passed us a composite event, use its head symbol.  */
      c = EVENT_HEAD (c);

      if (INTEGERP (c))
	{
	  ptr = push_key_description (XINT (c), ptr, 1);
	}
      else if (SYMBOLP (c))
	{
	  Lisp_Object name = SYMBOL_NAME (c);
	  int nbytes = SBYTES (name);

	  if (size - (ptr - buffer) < nbytes)
	    {
	      int offset = ptr - buffer;
	      size = max (2 * size, size + nbytes);
	      buffer = (char *) alloca (size);
	      ptr = buffer + offset;
	    }

	  ptr += copy_text (SDATA (name), ptr, nbytes,
			    STRING_MULTIBYTE (name), 1);
	}

      if ((NILP (echo_string) || SCHARS (echo_string) == 0)
	  && help_char_p (c))
	{
	  const char *text = " (Type ? for further options)";
	  int len = strlen (text);

	  if (size - (ptr - buffer) < len)
	    {
	      int offset = ptr - buffer;
	      size += len;
	      buffer = (char *) alloca (size);
	      ptr = buffer + offset;
	    }

	  bcopy (text, ptr, len);
	  ptr += len;
	}

      /* Replace a dash from echo_dash with a space, otherwise
	 add a space at the end as a separator between keys.  */
      if (STRINGP (echo_string)
	  && SCHARS (echo_string) > 1)
	{
	  Lisp_Object last_char, prev_char, idx;

	  idx = make_number (SCHARS (echo_string) - 2);
	  prev_char = Faref (echo_string, idx);

	  idx = make_number (SCHARS (echo_string) - 1);
	  last_char = Faref (echo_string, idx);

	  /* We test PREV_CHAR to make sure this isn't the echoing
	     of a minus-sign.  */
	  if (XINT (last_char) == '-' && XINT (prev_char) != ' ')
	    Faset (echo_string, idx, make_number (' '));
	  else
	    echo_string = concat2 (echo_string, build_string (" "));
	}
      else if (STRINGP (echo_string))
	echo_string = concat2 (echo_string, build_string (" "));

      current_kboard->echo_string
	= concat2 (echo_string, make_string (buffer, ptr - buffer));

      echo_now ();
    }
}

/* Temporarily add a dash to the end of the echo string if it's not
   empty, so that it serves as a mini-prompt for the very next character.  */

void
echo_dash ()
{
  /* Do nothing if not echoing at all.  */
  if (NILP (current_kboard->echo_string))
    return;

  if (!current_kboard->immediate_echo
      && SCHARS (current_kboard->echo_string) == 0)
    return;

  /* Do nothing if we just printed a prompt.  */
  if (current_kboard->echo_after_prompt
      == SCHARS (current_kboard->echo_string))
    return;

  /* Do nothing if we have already put a dash at the end.  */
  if (SCHARS (current_kboard->echo_string) > 1)
    {
      Lisp_Object last_char, prev_char, idx;

      idx = make_number (SCHARS (current_kboard->echo_string) - 2);
      prev_char = Faref (current_kboard->echo_string, idx);

      idx = make_number (SCHARS (current_kboard->echo_string) - 1);
      last_char = Faref (current_kboard->echo_string, idx);

      if (XINT (last_char) == '-' && XINT (prev_char) != ' ')
	return;
    }

  /* Put a dash at the end of the buffer temporarily,
     but make it go away when the next character is added.  */
  current_kboard->echo_string = concat2 (current_kboard->echo_string,
					 build_string ("-"));
  echo_now ();
}

/* Display the current echo string, and begin echoing if not already
   doing so.  */

void
echo_now ()
{
  if (!current_kboard->immediate_echo)
    {
      int i;
      current_kboard->immediate_echo = 1;

      for (i = 0; i < this_command_key_count; i++)
	{
	  Lisp_Object c;

	  /* Set before_command_echo_length to the value that would
	     have been saved before the start of this subcommand in
	     command_loop_1, if we had already been echoing then.  */
	  if (i == this_single_command_key_start)
	    before_command_echo_length = echo_length ();

	  c = XVECTOR (this_command_keys)->contents[i];
	  if (! (EVENT_HAS_PARAMETERS (c)
		 && EQ (EVENT_HEAD_KIND (EVENT_HEAD (c)), Qmouse_movement)))
	    echo_char (c);
	}

      /* Set before_command_echo_length to the value that would
	 have been saved before the start of this subcommand in
	 command_loop_1, if we had already been echoing then.  */
      if (this_command_key_count == this_single_command_key_start)
	before_command_echo_length = echo_length ();

      /* Put a dash at the end to invite the user to type more.  */
      echo_dash ();
    }

  echoing = 1;
  message3_nolog (current_kboard->echo_string,
		  SBYTES (current_kboard->echo_string),
		  STRING_MULTIBYTE (current_kboard->echo_string));
  echoing = 0;

  /* Record in what buffer we echoed, and from which kboard.  */
  echo_message_buffer = echo_area_buffer[0];
  echo_kboard = current_kboard;

  if (waiting_for_input && !NILP (Vquit_flag))
    quit_throw_to_read_char ();
}

/* Turn off echoing, for the start of a new command.  */

void
cancel_echoing ()
{
  current_kboard->immediate_echo = 0;
  current_kboard->echo_after_prompt = -1;
  current_kboard->echo_string = Qnil;
  ok_to_echo_at_next_pause = NULL;
  echo_kboard = NULL;
  echo_message_buffer = Qnil;
}

/* Return the length of the current echo string.  */

static int
echo_length ()
{
  return (STRINGP (current_kboard->echo_string)
	  ? SCHARS (current_kboard->echo_string)
	  : 0);
}

/* Truncate the current echo message to its first LEN chars.
   This and echo_char get used by read_key_sequence when the user
   switches frames while entering a key sequence.  */

static void
echo_truncate (nchars)
     int nchars;
{
  if (STRINGP (current_kboard->echo_string))
    current_kboard->echo_string
      = Fsubstring (current_kboard->echo_string,
		    make_number (0), make_number (nchars));
  truncate_echo_area (nchars);
}


/* Functions for manipulating this_command_keys.  */
static void
add_command_key (key)
     Lisp_Object key;
{
#if 0 /* Not needed after we made Freset_this_command_lengths
	 do the job immediately.  */
  /* If reset-this-command-length was called recently, obey it now.
     See the doc string of that function for an explanation of why.  */
  if (before_command_restore_flag)
    {
      this_command_key_count = before_command_key_count_1;
      if (this_command_key_count < this_single_command_key_start)
	this_single_command_key_start = this_command_key_count;
      echo_truncate (before_command_echo_length_1);
      before_command_restore_flag = 0;
    }
#endif

  if (this_command_key_count >= ASIZE (this_command_keys))
    this_command_keys = larger_vector (this_command_keys,
				       2 * ASIZE (this_command_keys),
				       Qnil);

  AREF (this_command_keys, this_command_key_count) = key;
  ++this_command_key_count;
}


Lisp_Object
recursive_edit_1 ()
{
  int count = SPECPDL_INDEX ();
  Lisp_Object val;

  if (command_loop_level > 0)
    {
      specbind (Qstandard_output, Qt);
      specbind (Qstandard_input, Qt);
    }

#ifdef HAVE_X_WINDOWS
  /* The command loop has started an hourglass timer, so we have to
     cancel it here, otherwise it will fire because the recursive edit
     can take some time.  Do not check for display_hourglass_p here,
     because it could already be nil.  */
    cancel_hourglass ();
#endif

  /* This function may have been called from a debugger called from
     within redisplay, for instance by Edebugging a function called
     from fontification-functions.  We want to allow redisplay in
     the debugging session.

     The recursive edit is left with a `(throw exit ...)'.  The `exit'
     tag is not caught anywhere in redisplay, i.e. when we leave the
     recursive edit, the original redisplay leading to the recursive
     edit will be unwound.  The outcome should therefore be safe.  */
  specbind (Qinhibit_redisplay, Qnil);
  redisplaying_p = 0;