xterm.c

/* X Communication module for terminals which understand the X protocol.
   Copyright (C) 1989, 93, 94, 95, 1996 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., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Xt features made by Fred Pierresteguy.  */

/* On 4.3 these lose if they come after xterm.h.  */
/* On HP-UX 8.0 signal.h loses if it comes after config.h.  */
/* Putting these at the beginning seems to be standard for other .c files.  */
#include <signal.h>

#include <config.h>

#include <stdio.h>

/* Need syssignal.h for various externs and definitions that may be required
   by some configurations for calls to signal later in this source file.  */
#include "syssignal.h"

#ifdef HAVE_X_WINDOWS

#include "lisp.h"
#include "blockinput.h"

/* This may include sys/types.h, and that somehow loses
   if this is not done before the other system files.  */
#include "xterm.h"
#include <X11/cursorfont.h>

#ifndef USG
/* Load sys/types.h if not already loaded.
   In some systems loading it twice is suicidal.  */
#ifndef makedev
#include <sys/types.h>
#endif /* makedev */
#endif /* USG */

#ifdef BSD_SYSTEM
#include <sys/ioctl.h>
#endif /* ! defined (BSD_SYSTEM) */

#include "systty.h"
#include "systime.h"

#ifndef INCLUDED_FCNTL
#include <fcntl.h>
#endif
#include <ctype.h>
#include <errno.h>
#include <setjmp.h>
#include <sys/stat.h>
/* Caused redefinition of DBL_DIG on Netbsd; seems not to be needed.  */
/* #include <sys/param.h>  */

#include "frame.h"
#include "dispextern.h"
#include "termhooks.h"
#include "termopts.h"
#include "termchar.h"
#if 0
#include "sink.h"
#include "sinkmask.h"
#endif /* ! 0 */
#include "gnu.h"
#include "disptab.h"
#include "buffer.h"
#include "window.h"
#include "keyboard.h"
#include "intervals.h"

#ifdef USE_X_TOOLKIT
#include <X11/Shell.h>
#endif

#ifdef USE_X_TOOLKIT
extern void free_frame_menubar ();
extern FRAME_PTR x_menubar_window_to_frame ();
#if (XtSpecificationRelease >= 5) && !defined(NO_EDITRES)
#define HACK_EDITRES
extern void _XEditResCheckMessages ();
#endif /* not NO_EDITRES */
#endif /* USE_X_TOOLKIT */

#ifndef USE_X_TOOLKIT
#define x_any_window_to_frame x_window_to_frame
#define x_top_window_to_frame x_window_to_frame
#endif

#ifdef USE_X_TOOLKIT
#include "widget.h"
#ifndef XtNinitialState
#define XtNinitialState "initialState"
#endif
#endif

#ifdef HAVE_SETLOCALE
/* So we can do setlocale.  */
#include <locale.h>
#endif

#ifdef SOLARIS2
/* memmove will be defined as a macro in Xfuncs.h unless
   <string.h> is included beforehand.  The declaration for memmove in
   <string.h> will cause a syntax error when Xfuncs.h later includes it.  */
#include <string.h>
#endif

#ifndef min
#define min(a,b) ((a)<(b) ? (a) : (b))
#endif
#ifndef max
#define max(a,b) ((a)>(b) ? (a) : (b))
#endif

/* This is a chain of structures for all the X displays currently in use.  */
struct x_display_info *x_display_list;

/* This is a list of cons cells, each of the form (NAME . FONT-LIST-CACHE),
   one for each element of x_display_list and in the same order.
   NAME is the name of the frame.
   FONT-LIST-CACHE records previous values returned by x-list-fonts.  */
Lisp_Object x_display_name_list;

/* Frame being updated by update_frame.  This is declared in term.c.
   This is set by update_begin and looked at by all the
   XT functions.  It is zero while not inside an update.
   In that case, the XT functions assume that `selected_frame'
   is the frame to apply to.  */
extern struct frame *updating_frame;

extern waiting_for_input;

/* This is a frame waiting to be autoraised, within XTread_socket.  */
struct frame *pending_autoraise_frame;

#ifdef USE_X_TOOLKIT
/* The application context for Xt use.  */
XtAppContext Xt_app_con;

static String Xt_default_resources[] =
{
  0
};
#endif

/* During an update, maximum vpos for ins/del line operations to affect.  */

static int flexlines;

/* During an update, nonzero if chars output now should be highlighted.  */

static int highlight;

/* Nominal cursor position -- where to draw output.
   During an update, these are different from the cursor-box position.  */

static int curs_x;
static int curs_y;

/* Mouse movement.

   Formerly, we used PointerMotionHintMask (in STANDARD_EVENT_MASK)
   so that we would have to call XQueryPointer after each MotionNotify
   event to ask for another such event.  However, this made mouse tracking
   slow, and there was a bug that made it eventually stop.

   Simply asking for MotionNotify all the time seems to work better.

   In order to avoid asking for motion events and then throwing most
   of them away or busy-polling the server for mouse positions, we ask
   the server for pointer motion hints.  This means that we get only
   one event per group of mouse movements.  "Groups" are delimited by
   other kinds of events (focus changes and button clicks, for
   example), or by XQueryPointer calls; when one of these happens, we
   get another MotionNotify event the next time the mouse moves.  This
   is at least as efficient as getting motion events when mouse
   tracking is on, and I suspect only negligibly worse when tracking
   is off.  */

/* Where the mouse was last time we reported a mouse event.  */
static FRAME_PTR last_mouse_frame;
static XRectangle last_mouse_glyph;

static Lisp_Object last_mouse_press_frame;

/* The scroll bar in which the last X motion event occurred.

   If the last X motion event occurred in a scroll bar, we set this
   so XTmouse_position can know whether to report a scroll bar motion or
   an ordinary motion.

   If the last X motion event didn't occur in a scroll bar, we set this
   to Qnil, to tell XTmouse_position to return an ordinary motion event.  */
static Lisp_Object last_mouse_scroll_bar;

/* This is a hack.  We would really prefer that XTmouse_position would
   return the time associated with the position it returns, but there
   doesn't seem to be any way to wrest the timestamp from the server
   along with the position query.  So, we just keep track of the time
   of the last movement we received, and return that in hopes that
   it's somewhat accurate.  */
static Time last_mouse_movement_time;

/* Incremented by XTread_socket whenever it really tries to read events.  */
#ifdef __STDC__
static int volatile input_signal_count;
#else
static int input_signal_count;
#endif

/* Used locally within XTread_socket.  */
static int x_noop_count;

/* Initial values of argv and argc.  */
extern char **initial_argv;
extern int initial_argc;

extern Lisp_Object Vcommand_line_args, Vsystem_name;

/* Tells if a window manager is present or not. */

extern Lisp_Object Vx_no_window_manager;

extern Lisp_Object Qface, Qmouse_face;

extern int errno;

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

static Lisp_Object Qvendor_specific_keysyms;

extern XrmDatabase x_load_resources ();

extern Lisp_Object x_icon_type ();

void x_delete_display ();

static void redraw_previous_char ();
static void redraw_following_char ();
static unsigned int x_x_to_emacs_modifiers ();

static int fast_find_position ();
static void note_mouse_highlight ();
static void clear_mouse_face ();
static void show_mouse_face ();
static void do_line_dance ();

static int XTcursor_to ();
static int XTclear_end_of_line ();
static int x_io_error_quitter ();
void x_catch_errors ();
void x_uncatch_errors ();

#if 0
/* This is a function useful for recording debugging information
   about the sequence of occurrences in this file.  */

struct record 
{
  char *locus;
  int type;
};

struct record event_record[100];

int event_record_index;

record_event (locus, type)
     char *locus;
     int type;
{
  if (event_record_index == sizeof (event_record) / sizeof (struct record))
    event_record_index = 0;

  event_record[event_record_index].locus = locus;
  event_record[event_record_index].type = type;
  event_record_index++;
}

#endif /* 0 */

/* Return the struct x_display_info corresponding to DPY.  */

struct x_display_info *
x_display_info_for_display (dpy)
     Display *dpy;
{
  struct x_display_info *dpyinfo;

  for (dpyinfo = x_display_list; dpyinfo; dpyinfo = dpyinfo->next)
    if (dpyinfo->display == dpy)
      return dpyinfo;

  return 0;
}

/* Starting and ending updates.

   These hooks are called by update_frame at the beginning and end
   of a frame update.  We record in `updating_frame' the identity
   of the frame being updated, so that the XT... functions do not
   need to take a frame as argument.  Most of the XT... functions
   should never be called except during an update, the only exceptions
   being XTcursor_to, XTwrite_glyphs and XTreassert_line_highlight.  */

static
XTupdate_begin (f)
     struct frame *f;
{
  int mask;

  if (f == 0)
    abort ();

  flexlines = f->height;
  highlight = 0;

  BLOCK_INPUT;

  curs_x = FRAME_CURSOR_X (f);
  curs_y = FRAME_CURSOR_Y (f);

  if (f == FRAME_X_DISPLAY_INFO (f)->mouse_face_mouse_frame)
    {
      /* Don't do highlighting for mouse motion during the update.  */
      FRAME_X_DISPLAY_INFO (f)->mouse_face_defer = 1;

      /* If the frame needs to be redrawn,
	 simply forget about any prior mouse highlighting.  */
      if (FRAME_GARBAGED_P (f))
	FRAME_X_DISPLAY_INFO (f)->mouse_face_window = Qnil;

      if (!NILP (FRAME_X_DISPLAY_INFO (f)->mouse_face_window))
	{
	  int firstline, lastline, i;
	  struct window *w = XWINDOW (FRAME_X_DISPLAY_INFO (f)->mouse_face_window);

	  /* Find the first, and the last+1, lines affected by redisplay.  */
	  for (firstline = 0; firstline < f->height; firstline++)
	    if (FRAME_DESIRED_GLYPHS (f)->enable[firstline])
	      break;

	  lastline = f->height;
	  for (i = f->height - 1; i >= 0; i--)
	    {
	      if (FRAME_DESIRED_GLYPHS (f)->enable[i])
		break;
	      else
		lastline = i;
	    }

	  /* Can we tell that this update does not affect the window
	     where the mouse highlight is?  If so, no need to turn off.
	     Likewise, don't do anything if the frame is garbaged;
	     in that case, the FRAME_CURRENT_GLYPHS that we would use
	     are all wrong, and we will redisplay that line anyway.  */
	  if (! (firstline > (XFASTINT (w->top) + window_internal_height (w))
		 || lastline < XFASTINT (w->top)))
	    clear_mouse_face (FRAME_X_DISPLAY_INFO (f));
	}
    }

  UNBLOCK_INPUT;
}

static
XTupdate_end (f)
     struct frame *f;
{
  int mask;

  BLOCK_INPUT;

  do_line_dance ();
  x_display_cursor (f, 1, curs_x, curs_y);

  FRAME_X_DISPLAY_INFO (f)->mouse_face_defer = 0;
#if 0
  /* This fails in the case of having updated only the echo area
     if we have switched buffers.  In that case, FRAME_CURRENT_GLYPHS
     has no relation to the current contents, and its charstarts
     have no relation to the contents of the window-buffer.
  I don't know a clean way to check
     for that case.  window_end_valid isn't set up yet.  */
  if (f == FRAME_X_DISPLAY_INFO (f)->mouse_face_mouse_frame)
    note_mouse_highlight (f, FRAME_X_DISPLAY_INFO (f)->mouse_face_mouse_x,
			  FRAME_X_DISPLAY_INFO (f)->mouse_face_mouse_y);
#endif

  XFlush (FRAME_X_DISPLAY (f));
  UNBLOCK_INPUT;
}

/* This is called after a redisplay on frame F.  */

static
XTframe_up_to_date (f)
     FRAME_PTR f;
{
  BLOCK_INPUT;
  if (FRAME_X_DISPLAY_INFO (f)->mouse_face_deferred_gc
      || f == FRAME_X_DISPLAY_INFO (f)->mouse_face_mouse_frame)
    {
      note_mouse_highlight (FRAME_X_DISPLAY_INFO (f)->mouse_face_mouse_frame,
			    FRAME_X_DISPLAY_INFO (f)->mouse_face_mouse_x,
			    FRAME_X_DISPLAY_INFO (f)->mouse_face_mouse_y);
      FRAME_X_DISPLAY_INFO (f)->mouse_face_deferred_gc = 0;
    }
  UNBLOCK_INPUT;
}

/* External interface to control of standout mode.
   Call this when about to modify line at position VPOS
   and not change whether it is highlighted.  */

XTreassert_line_highlight (new, vpos)
     int new, vpos;
{
  highlight = new;
}

/* Call this when about to modify line at position VPOS
   and change whether it is highlighted.  */

static
XTchange_line_highlight (new_highlight, vpos, first_unused_hpos)
     int new_highlight, vpos, first_unused_hpos;
{
  highlight = new_highlight;
  XTcursor_to (vpos, 0);
  XTclear_end_of_line (FRAME_WINDOW_WIDTH (updating_frame));
}

/* This is used when starting Emacs and when restarting after suspend.
   When starting Emacs, no X window is mapped.  And nothing must be done
   to Emacs's own window if it is suspended (though that rarely happens).  */

static
XTset_terminal_modes ()
{
}

/* This is called when exiting or suspending Emacs.
   Exiting will make the X-windows go away, and suspending
   requires no action.  */

static
XTreset_terminal_modes ()
{
/*  XTclear_frame ();  */
}

/* Set the nominal cursor position of the frame.
   This is where display update commands will take effect.
   This does not affect the place where the cursor-box is displayed.  */

static int
XTcursor_to (row, col)
     register int row, col;
{
  int mask;
  int orow = row;

  curs_x = col;
  curs_y = row;

  if (updating_frame == 0)
    {
      BLOCK_INPUT;
      x_display_cursor (selected_frame, 1, curs_x, curs_y);
      XFlush (FRAME_X_DISPLAY (selected_frame));
      UNBLOCK_INPUT;
    }
}

/* Display a sequence of N glyphs found at GP.
   WINDOW is the x-window to output to.  LEFT and TOP are starting coords.
   HL is 1 if this text is highlighted, 2 if the cursor is on it,
   3 if should appear in its mouse-face.
   JUST_FOREGROUND if 1 means draw only the foreground;
   don't alter the background.

   FONT is the default font to use (for glyphs whose font-code is 0).

   Since the display generation code is responsible for calling
   compute_char_face and compute_glyph_face on everything it puts in
   the display structure, we can assume that the face code on each
   glyph is a valid index into FRAME_COMPUTED_FACES (f), and the one
   to which we can actually apply intern_face.
   Call this function with input blocked.  */

#if 1
/* This is the multi-face code.  */

static void
dumpglyphs (f, left, top, gp, n, hl, just_foreground)
     struct frame *f;
     int left, top;
     register GLYPH *gp; /* Points to first GLYPH. */
     register int n;  /* Number of glyphs to display. */
     int hl;
     int just_foreground;
{
  /* Holds characters to be displayed. */
  char *buf = (char *) alloca (FRAME_WINDOW_WIDTH (f) * sizeof (*buf));
  register char *cp;		/* Steps through buf[]. */
  register int tlen = GLYPH_TABLE_LENGTH;
  register Lisp_Object *tbase = GLYPH_TABLE_BASE;
  Window window = FRAME_X_WINDOW (f);
  int orig_left = left;

  while (n > 0)
    {
      /* Get the face-code of the next GLYPH.  */
      int cf, len;
      GLYPH g = *gp;

      GLYPH_FOLLOW_ALIASES (tbase, tlen, g);
      cf = FAST_GLYPH_FACE (g);

      /* Find the run of consecutive glyphs with the same face-code.
	 Extract their character codes into BUF.  */
      cp = buf;
      while (n > 0)
	{
	  g = *gp;
	  GLYPH_FOLLOW_ALIASES (tbase, tlen, g);
	  if (FAST_GLYPH_FACE (g) != cf)
	    break;

	  *cp++ = FAST_GLYPH_CHAR (g);
	  --n;
	  ++gp;
	}

      /* LEN gets the length of the run.  */
      len = cp - buf;

      /* Now output this run of chars, with the font and pixel values
	 determined by the face code CF.  */
      {
	struct face *face = FRAME_DEFAULT_FACE (f);
	XFontStruct *font = FACE_FONT (face);
	GC gc = FACE_GC (face);
	int stippled = 0;

	/* HL = 3 means use a mouse face previously chosen.  */
	if (hl == 3)
	  cf = FRAME_X_DISPLAY_INFO (f)->mouse_face_face_id;

	/* First look at the face of the text itself.  */
	if (cf != 0)
	  {
	    /* It's possible for the display table to specify
	       a face code that is out of range.  Use 0 in that case.  */
	    if (cf < 0 || cf >= FRAME_N_COMPUTED_FACES (f)
		|| FRAME_COMPUTED_FACES (f) [cf] == 0)
	      cf = 0;

	    if (cf == 1)
	      face = FRAME_MODE_LINE_FACE (f);
	    else
	      face = intern_face (f, FRAME_COMPUTED_FACES (f) [cf]);
	    font = FACE_FONT (face);
	    gc = FACE_GC (face);
	    if (FACE_STIPPLE (face))
	      stippled = 1;
	  }

	/* Then comes the distinction between modeline and normal text.  */
	else if (hl == 0)
	  ;
	else if (hl == 1)
	  {
	    face = FRAME_MODE_LINE_FACE (f);
	    font = FACE_FONT (face);
	    gc   = FACE_GC   (face);
	    if (FACE_STIPPLE (face))
	      stippled = 1;
	  }

#define FACE_DEFAULT (~0)

	/* Now override that if the cursor's on this character.  */
	if (hl == 2)
	  {
	    /* The cursor overrides stippling.  */
	    stippled = 0;

	    if ((!face->font
		 || face->font == (XFontStruct *) FACE_DEFAULT
		 || face->font == f->output_data.x->font)
		&& face->background == f->output_data.x->background_pixel
		&& face->foreground == f->output_data.x->foreground_pixel)
	      {
		gc = f->output_data.x->cursor_gc;
	      }
	    /* Cursor on non-default face: must merge.  */
	    else
	      {
		XGCValues xgcv;
		unsigned long mask;

		xgcv.background = f->output_data.x->cursor_pixel;
		xgcv.foreground = face->background;
		/* If the glyph would be invisible,
		   try a different foreground.  */
		if (xgcv.foreground == xgcv.background)
		  xgcv.foreground = face->foreground;
		if (xgcv.foreground == xgcv.background)
		  xgcv.foreground = f->output_data.x->cursor_foreground_pixel;
		if (xgcv.foreground == xgcv.background)
		  xgcv.foreground = face->foreground;
		/* Make sure the cursor is distinct from text in this face.  */
		if (xgcv.background == face->background
		    && xgcv.foreground == face->foreground)
		  {
		    xgcv.background = face->foreground;
		    xgcv.foreground = face->background;
		  }
		xgcv.font = face->font->fid;
		xgcv.graphics_exposures = 0;
		mask = GCForeground | GCBackground | GCFont | GCGraphicsExposures;
		if (FRAME_X_DISPLAY_INFO (f)->scratch_cursor_gc)
		  XChangeGC (FRAME_X_DISPLAY (f),
			     FRAME_X_DISPLAY_INFO (f)->scratch_cursor_gc,
			     mask, &xgcv);
		else
		  FRAME_X_DISPLAY_INFO (f)->scratch_cursor_gc
		    = XCreateGC (FRAME_X_DISPLAY (f), window, mask, &xgcv);
		gc = FRAME_X_DISPLAY_INFO (f)->scratch_cursor_gc;
#if 0
/* If this code is restored, it must also reset to the default stipple
   if necessary. */
		if (face->stipple && face->stipple != FACE_DEFAULT)
		  XSetStipple (FRAME_X_DISPLAY (f), gc, face->stipple);
#endif
	      }
	  }

	if (font == (XFontStruct *) FACE_DEFAULT)
	  font = f->output_data.x->font;

	if (just_foreground)
	  XDrawString (FRAME_X_DISPLAY (f), window, gc,
		       left, top + FONT_BASE (font), buf, len);
	else
	  {
	    if (stippled)
	      {
		/* Turn stipple on.  */
		XSetFillStyle (FRAME_X_DISPLAY (f), gc, FillOpaqueStippled);

		/* Draw stipple on background.  */
		XFillRectangle (FRAME_X_DISPLAY (f), window, gc,
				left, top,
				FONT_WIDTH (font) * len,
				FONT_HEIGHT (font));

		/* Turn stipple off.  */
		XSetFillStyle (FRAME_X_DISPLAY (f), gc, FillSolid);

		/* Draw the text, solidly, onto the stipple pattern.  */
		XDrawString (FRAME_X_DISPLAY (f), window, gc,
			     left, top + FONT_BASE (font), buf, len);
	      }
	    else
	      XDrawImageString (FRAME_X_DISPLAY (f), window, gc,
				left, top + FONT_BASE (font), buf, len);

	    /* Clear the rest of the line's height.  */
	    if (f->output_data.x->line_height != FONT_HEIGHT (font))
	      XClearArea (FRAME_X_DISPLAY (f), window, left,
			  top + FONT_HEIGHT (font),
			  FONT_WIDTH (font) * len,
			  /* This is how many pixels of height
			     we have to clear.  */
			  f->output_data.x->line_height - FONT_HEIGHT (font),
			  False);
	  }

#if 0 /* Doesn't work, because it uses FRAME_CURRENT_GLYPHS,
	 which often is not up to date yet.  */
	if (!just_foreground)
	  {
	    if (left == orig_left)
	      redraw_previous_char (f, PIXEL_TO_CHAR_COL (f, left),
				    PIXEL_TO_CHAR_ROW (f, top), hl == 1);
	    if (n == 0)
	      redraw_following_char (f, PIXEL_TO_CHAR_COL (f, left + len * FONT_WIDTH (font)),
				     PIXEL_TO_CHAR_ROW (f, top), hl == 1);
	  }
#endif

	/* We should probably check for XA_UNDERLINE_POSITION and
	   XA_UNDERLINE_THICKNESS properties on the font, but let's
	   just get the thing working, and come back to that.  */
	{
	  int underline_position = 1;

	  if (font->descent <= underline_position)
	    underline_position = font->descent - 1;

	  if (face->underline)
	    XFillRectangle (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
			    FACE_GC (face),
			    left, (top
				   + FONT_BASE (font)
				   + underline_position),
			    len * FONT_WIDTH (font), 1);
	}

	left += len * FONT_WIDTH (font);
      }
    }
}
#endif /* 1 */

#if 0
/* This is the old single-face code.  */

static void
dumpglyphs (f, left, top, gp, n, hl, font)
     struct frame *f;
     int left, top;
     register GLYPH *gp; /* Points to first GLYPH. */
     register int n;  /* Number of glyphs to display. */
     int hl;
     XFontStruct *font;
{
  register int len;
  Window window = FRAME_X_WINDOW (f);
  GC drawing_gc =   (hl == 2 ? f->output_data.x->cursor_gc
		             : (hl ? f->output_data.x->reverse_gc
				   : f->output_data.x->normal_gc));

  if (sizeof (GLYPH) == sizeof (XChar2b))
    XDrawImageString16 (FRAME_X_DISPLAY (f), window, drawing_gc,
			left, top + FONT_BASE (font), (XChar2b *) gp, n);
  else if (sizeof (GLYPH) == sizeof (unsigned char))
    XDrawImageString (FRAME_X_DISPLAY (f), window, drawing_gc,
		      left, top + FONT_BASE (font), (char *) gp, n);
  else
    /* What size of glyph ARE you using?  And does X have a function to
       draw them?  */
    abort ();
}
#endif

/* Output some text at the nominal frame cursor position.
   Advance the cursor over the text.
   Output LEN glyphs at START.

   `highlight', set up by XTreassert_line_highlight or XTchange_line_highlight,
   controls the pixel values used for foreground and background.  */

static
XTwrite_glyphs (start, len)
     register GLYPH *start;
     int len;
{
  register int temp_length;
  int mask;
  struct frame *f;

  BLOCK_INPUT;

  do_line_dance ();
  f = updating_frame;
  if (f == 0)
    {
      f = selected_frame;
      /* If not within an update,
	 output at the frame's visible cursor.  */
      curs_x = f->cursor_x;
      curs_y = f->cursor_y;
    }

  dumpglyphs (f,
	      CHAR_TO_PIXEL_COL (f, curs_x),
	      CHAR_TO_PIXEL_ROW (f, curs_y),
	      start, len, highlight, 0);

  /* If we drew on top of the cursor, note that it is turned off.  */
  if (curs_y == f->phys_cursor_y
      && curs_x <= f->phys_cursor_x
      && curs_x + len > f->phys_cursor_x)
    f->phys_cursor_on = 0;

  if (updating_frame == 0)
    x_display_cursor (f, 1, FRAME_CURSOR_X (f) + len, FRAME_CURSOR_Y (f));
  else
    curs_x += len;

  UNBLOCK_INPUT;
}

/* Clear to the end of the line.
   Erase the current text line from the nominal cursor position (inclusive)
   to column FIRST_UNUSED (exclusive).  The idea is that everything
   from FIRST_UNUSED onward is already erased.  */

static
XTclear_end_of_line (first_unused)
     register int first_unused;
{
  struct frame *f = updating_frame;
  int mask;

  if (f == 0)
    abort ();

  if (curs_y < 0 || curs_y >= f->height)
    return;
  if (first_unused <= 0)
    return;

  if (first_unused >= FRAME_WINDOW_WIDTH (f))
    first_unused = FRAME_WINDOW_WIDTH (f);

  first_unused += FRAME_LEFT_SCROLL_BAR_WIDTH (f);

  BLOCK_INPUT;

  do_line_dance ();

  /* Notice if the cursor will be cleared by this operation.  */
  if (curs_y == f->phys_cursor_y
      && curs_x <= f->phys_cursor_x
      && f->phys_cursor_x < first_unused)
    f->phys_cursor_on = 0;

  XClearArea (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
	      CHAR_TO_PIXEL_COL (f, curs_x),
	      CHAR_TO_PIXEL_ROW (f, curs_y),
	      FONT_WIDTH (f->output_data.x->font) * (first_unused - curs_x),
	      f->output_data.x->line_height, False);
#if 0
  redraw_previous_char (f, curs_x, curs_y, highlight);
#endif

  UNBLOCK_INPUT;
}

static
XTclear_frame ()
{
  int mask;
  struct frame *f = updating_frame;

  if (f == 0)
    f = selected_frame;

  f->phys_cursor_on = 0;	/* Cursor not visible.  */
  curs_x = 0;			/* Nominal cursor position is top left.  */
  curs_y = 0;

  BLOCK_INPUT;

  XClearWindow (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f));

  /* We have to clear the scroll bars, too.  If we have changed
     colors or something like that, then they should be notified.  */
  x_scroll_bar_clear (f);

  XFlush (FRAME_X_DISPLAY (f));
  UNBLOCK_INPUT;
}

#if 0
/* This currently does not work because FRAME_CURRENT_GLYPHS doesn't
   always contain the right glyphs to use.

   It also needs to be changed to look at the details of the font and
   see whether there is really overlap, and do nothing when there is
   not.  This can use font_char_overlap_left and font_char_overlap_right,
   but just how to use them is not clear.  */

/* Erase the character (if any) at the position just before X, Y in frame F,
   then redraw it and the character before it.
   This is necessary when we erase starting at X,
   in case the character after X overlaps into the one before X.
   Call this function with input blocked.  */

static void
redraw_previous_char (f, x, y, highlight_flag)
     FRAME_PTR f;
     int x, y;
     int highlight_flag;
{
  /* Erase the character before the new ones, in case
     what was here before overlaps it.
     Reoutput that character, and the previous character
     (in case the previous character overlaps it).  */
  if (x > 0)
    {
      int start_x = x - 2;
      if (start_x < 0)
	start_x = 0;
      XClearArea (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
		  CHAR_TO_PIXEL_COL (f, x - 1),
		  CHAR_TO_PIXEL_ROW (f, y),
		  FONT_WIDTH (f->output_data.x->font),
		  f->output_data.x->line_height, False);

      dumpglyphs (f, CHAR_TO_PIXEL_COL (f, start_x),
		  CHAR_TO_PIXEL_ROW (f, y),
		  &FRAME_CURRENT_GLYPHS (f)->glyphs[y][start_x],
		  x - start_x, highlight_flag, 1);
    }
}

/* Erase the character (if any) at the position X, Y in frame F,
   then redraw it and the character after it.
   This is necessary when we erase endng at X,
   in case the character after X overlaps into the one before X.
   Call this function with input blocked.  */

static void
redraw_following_char (f, x, y, highlight_flag)
     FRAME_PTR f;
     int x, y;
     int highlight_flag;
{
  int limit = FRAME_CURRENT_GLYPHS (f)->used[y];
  /* Erase the character after the new ones, in case
     what was here before overlaps it.
     Reoutput that character, and the following character
     (in case the following character overlaps it).  */
  if (x < limit
      && FRAME_CURRENT_GLYPHS (f)->glyphs[y][x] != SPACEGLYPH)
    {
      int end_x = x + 2;
      if (end_x > limit)
	end_x = limit;
      XClearArea (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
		  CHAR_TO_PIXEL_COL (f, x),
		  CHAR_TO_PIXEL_ROW (f, y),
		  FONT_WIDTH (f->output_data.x->font),
		  f->output_data.x->line_height, False);

      dumpglyphs (f, CHAR_TO_PIXEL_COL (f, x),
		  CHAR_TO_PIXEL_ROW (f, y),
		  &FRAME_CURRENT_GLYPHS (f)->glyphs[y][x],
		  end_x - x, highlight_flag, 1);
    }
}
#endif /* 0 */

#if 0 /* Not in use yet */

/* Return 1 if character C in font F extends past its left edge.  */

static int
font_char_overlap_left (font, c)
     XFontStruct *font;
     int c;
{
  XCharStruct *s;

  /* Find the bounding-box info for C.  */
  if (font->per_char == 0)
    s = &font->max_bounds;
  else
    {
      int rowlen = font->max_char_or_byte2 - font->min_char_or_byte2 + 1;
      int row, within;

      /* Decode char into row number (byte 1) and code within row (byte 2).  */
      row = c >> 8;
      within = c & 0177;
      if (!(within >= font->min_char_or_byte2
	    && within <= font->max_char_or_byte2
	    && row >= font->min_byte1
	    && row <= font->max_byte1))
	{
	  /* If char is out of range, try the font's default char instead.  */
	  c = font->default_char;
	  row = c >> (BITS_PER_INT - 8);
	  within = c & 0177;
	}
      if (!(within >= font->min_char_or_byte2
	    && within <= font->max_char_or_byte2
	    && row >= font->min_byte1
	    && row <= font->max_byte1))
	/* Still out of range means this char does not overlap.  */
	return 0;
      else
	/* We found the info for this char.  */
	s = (font->per_char + (within - font->min_char_or_byte2)
	     + row * rowlen);
    }

  return (s && s->lbearing < 0);
}