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/* Updating of data structures for redisplay.
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   Copyright (C) 1985, 86, 87, 88, 93, 94, 95, 97, 98, 1999
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       Free Software Foundation, Inc.
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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
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the Free Software Foundation; either version 2, or (at your option)
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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
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */
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#include <config.h>
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#include <signal.h>
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#include <stdio.h>
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#include <ctype.h>

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#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

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#include "lisp.h"
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#include "termchar.h"
#include "termopts.h"
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#include "termhooks.h"
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/* cm.h must come after dispextern.h on Windows.  */
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#include "dispextern.h"
#include "cm.h"
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#include "buffer.h"
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#include "charset.h"
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#include "keyboard.h"
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#include "frame.h"
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#include "window.h"
#include "commands.h"
#include "disptab.h"
#include "indent.h"
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#include "intervals.h"
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#include "blockinput.h"
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#include "process.h"
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/* I don't know why DEC Alpha OSF1 fail to compile this file if we
   include the following file.  */
/* #include "systty.h" */
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#include "syssignal.h"
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#ifdef HAVE_X_WINDOWS
#include "xterm.h"
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#endif /* HAVE_X_WINDOWS */
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#ifdef HAVE_NTGUI
#include "w32term.h"
#endif /* HAVE_NTGUI */

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/* Include systime.h after xterm.h to avoid double inclusion of time.h.  */
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#include "systime.h"
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#include <errno.h>

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/* To get the prototype for `sleep'.  */

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

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#define max(a, b) ((a) > (b) ? (a) : (b))
#define min(a, b) ((a) < (b) ? (a) : (b))

/* Get number of chars of output now in the buffer of a stdio stream.
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   This ought to be built in in stdio, but it isn't.  Some s- files
   override this because their stdio internals differ.  */

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#ifdef __GNU_LIBRARY__
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/* The s- file might have overridden the definition with one that
   works for the system's C library.  But we are using the GNU C
   library, so this is the right definition for every system.  */

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#ifdef GNU_LIBRARY_PENDING_OUTPUT_COUNT
#define PENDING_OUTPUT_COUNT GNU_LIBRARY_PENDING_OUTPUT_COUNT
#else
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#undef	PENDING_OUTPUT_COUNT
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#define	PENDING_OUTPUT_COUNT(FILE) ((FILE)->__bufp - (FILE)->__buffer)
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#endif
#else /* not __GNU_LIBRARY__ */
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#if !defined (PENDING_OUTPUT_COUNT) && HAVE_STDIO_EXT_H && HAVE___FPENDING
#include <stdio_ext.h>
#define PENDING_OUTPUT_COUNT(FILE) __fpending (FILE)
#endif
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#ifndef PENDING_OUTPUT_COUNT
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#define PENDING_OUTPUT_COUNT(FILE) ((FILE)->_ptr - (FILE)->_base)
#endif
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#endif /* not __GNU_LIBRARY__ */

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#if defined (LINUX) && defined (HAVE_LIBNCURSES)
#include <term.h>		/* for tgetent */
#endif
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/* Structure to pass dimensions around.  Used for character bounding
   boxes, glyph matrix dimensions and alike.  */

struct dim
{
  int width;
  int height;
};


/* Function prototypes.  */

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static void redraw_overlapping_rows P_ ((struct window *, int));
static void redraw_overlapped_rows P_ ((struct window *, int));
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static int count_blanks P_ ((struct glyph *, int));
static int count_match P_ ((struct glyph *, struct glyph *,
			    struct glyph *, struct glyph *));
static unsigned line_draw_cost P_ ((struct glyph_matrix *, int));
static void update_frame_line P_ ((struct frame *, int));
static struct dim allocate_matrices_for_frame_redisplay
     P_ ((Lisp_Object, int, int, struct dim, int, int *));
static void allocate_matrices_for_window_redisplay P_ ((struct window *,
							struct dim));
static int realloc_glyph_pool P_ ((struct glyph_pool *, struct dim));
static void adjust_frame_glyphs P_ ((struct frame *));
struct glyph_matrix *new_glyph_matrix P_ ((struct glyph_pool *));
static void free_glyph_matrix P_ ((struct glyph_matrix *));
static void adjust_glyph_matrix P_ ((struct window *, struct glyph_matrix *,
				     int, int, struct dim));
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static void change_frame_size_1 P_ ((struct frame *, int, int, int, int, int));
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static void swap_glyph_pointers P_ ((struct glyph_row *, struct glyph_row *));
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#ifdef GLYPH_DEBUG
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static int glyph_row_slice_p P_ ((struct glyph_row *, struct glyph_row *));
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#endif
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static void fill_up_frame_row_with_spaces P_ ((struct glyph_row *, int));
static void build_frame_matrix_from_window_tree P_ ((struct glyph_matrix *,
						     struct window *));
static void build_frame_matrix_from_leaf_window P_ ((struct glyph_matrix *,
						     struct window *));
static struct glyph_pool *new_glyph_pool P_ ((void));
static void free_glyph_pool P_ ((struct glyph_pool *));
static void adjust_frame_glyphs_initially P_ ((void));
static void adjust_frame_message_buffer P_ ((struct frame *));
static void adjust_decode_mode_spec_buffer P_ ((struct frame *));
static void fill_up_glyph_row_with_spaces P_ ((struct glyph_row *));
static void build_frame_matrix P_ ((struct frame *));
void clear_current_matrices P_ ((struct frame *));
void scroll_glyph_matrix_range P_ ((struct glyph_matrix *, int, int,
				    int, int));
static void clear_window_matrices P_ ((struct window *, int));
static void fill_up_glyph_row_area_with_spaces P_ ((struct glyph_row *, int));
static int scrolling_window P_ ((struct window *, int));
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static int update_window_line P_ ((struct window *, int, int *));
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static void update_marginal_area P_ ((struct window *, int, int));
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static int update_text_area P_ ((struct window *, int));
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static void make_current P_ ((struct glyph_matrix *, struct glyph_matrix *,
			      int));
static void mirror_make_current P_ ((struct window *, int));
void check_window_matrix_pointers P_ ((struct window *));
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#if GLYPH_DEBUG
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static void check_matrix_pointers P_ ((struct glyph_matrix *,
				       struct glyph_matrix *));
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#endif
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static void mirror_line_dance P_ ((struct window *, int, int, int *, char *));
static int update_window_tree P_ ((struct window *, int));
static int update_window P_ ((struct window *, int));
static int update_frame_1 P_ ((struct frame *, int, int));
static void set_window_cursor_after_update P_ ((struct window *));
static int row_equal_p P_ ((struct window *, struct glyph_row *,
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			    struct glyph_row *, int));
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static void adjust_frame_glyphs_for_window_redisplay P_ ((struct frame *));
static void adjust_frame_glyphs_for_frame_redisplay P_ ((struct frame *));
static void reverse_rows P_ ((struct glyph_matrix *, int, int));
static int margin_glyphs_to_reserve P_ ((struct window *, int, Lisp_Object));
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static void sync_window_with_frame_matrix_rows P_ ((struct window *));
struct window *frame_row_to_window P_ ((struct window *, int));
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/* Non-zero means don't pause redisplay for pending input.  (This is
   for debugging and for a future implementation of EDT-like
   scrolling.  */
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int redisplay_dont_pause;
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/* Nonzero upon entry to redisplay means do not assume anything about
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   current contents of actual terminal frame; clear and redraw it.  */
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int frame_garbaged;
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/* Nonzero means last display completed.  Zero means it was preempted.  */
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int display_completed;

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/* Lisp variable visible-bell; enables use of screen-flash instead of
   audible bell.  */
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int visible_bell;

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/* Invert the color of the whole frame, at a low level.  */
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int inverse_video;

/* Line speed of the terminal.  */

int baud_rate;

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/* Either nil or a symbol naming the window system under which Emacs
   is running.  */
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Lisp_Object Vwindow_system;

/* Version number of X windows: 10, 11 or nil.  */
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Lisp_Object Vwindow_system_version;

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/* Vector of glyph definitions.  Indexed by glyph number, the contents
   are a string which is how to output the glyph.
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   If Vglyph_table is nil, a glyph is output by using its low 8 bits
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   as a character code.

   This is an obsolete feature that is no longer used.  The variable
   is retained for compatibility.  */
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Lisp_Object Vglyph_table;

/* Display table to use for vectors that don't specify their own.  */

Lisp_Object Vstandard_display_table;

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/* Nonzero means reading single-character input with prompt so put
   cursor on mini-buffer after the prompt.  positive means at end of
   text in echo area; negative means at beginning of line.  */

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int cursor_in_echo_area;
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Lisp_Object Qdisplay_table, Qredisplay_dont_pause;
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/* The currently selected frame.  In a single-frame version, this
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   variable always equals the_only_frame.  */
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Lisp_Object selected_frame;
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/* A frame which is not just a mini-buffer, or 0 if there are no such
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   frames.  This is usually the most recent such frame that was
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   selected.  In a single-frame version, this variable always holds
   the address of the_only_frame.  */
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struct frame *last_nonminibuf_frame;
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/* Stdio stream being used for copy of all output.  */
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FILE *termscript;
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/* Structure for info on cursor positioning.  */
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struct cm Wcm;
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/* 1 means SIGWINCH happened when not safe.  */
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int delayed_size_change;
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/* 1 means glyph initialization has been completed at startup.  */
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static int glyphs_initialized_initially_p;
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/* Updated window if != 0.  Set by update_window.  */
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struct window *updated_window;
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/* Glyph row updated in update_window_line, and area that is updated.  */
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struct glyph_row *updated_row;
int updated_area;
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/* A glyph for a space.  */
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struct glyph space_glyph;
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/* Non-zero means update has been performed directly, so that there's
   no need for redisplay_internal to do much work.  Set by
   direct_output_for_insert.  */
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int redisplay_performed_directly_p;
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/* Counts of allocated structures.  These counts serve to diagnose
   memory leaks and double frees.  */
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int glyph_matrix_count;
int glyph_pool_count;
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/* If non-null, the frame whose frame matrices are manipulated.  If
   null, window matrices are worked on.  */
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static struct frame *frame_matrix_frame;
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/* Current interface for window-based redisplay.  Set from init_xterm.
   A null value means we are not using window-based redisplay.  */
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struct redisplay_interface *rif;
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/* Non-zero means that fonts have been loaded since the last glyph
   matrix adjustments.  Redisplay must stop, and glyph matrices must
   be adjusted when this flag becomes non-zero during display.  The
   reason fonts can be loaded so late is that fonts of fontsets are
   loaded on demand.  */
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int fonts_changed_p;
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/* Convert vpos and hpos from frame to window and vice versa. 
   This may only be used for terminal frames.  */
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#if GLYPH_DEBUG
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static int window_to_frame_vpos P_ ((struct window *, int));
static int window_to_frame_hpos P_ ((struct window *, int));
#define WINDOW_TO_FRAME_VPOS(W, VPOS) window_to_frame_vpos ((W), (VPOS))
#define WINDOW_TO_FRAME_HPOS(W, HPOS) window_to_frame_hpos ((W), (HPOS))
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#else /* GLYPH_DEBUG == 0 */
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#define WINDOW_TO_FRAME_VPOS(W, VPOS) ((VPOS) + XFASTINT ((W)->top))
#define WINDOW_TO_FRAME_HPOS(W, HPOS) ((HPOS) + XFASTINT ((W)->left))
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#endif /* GLYPH_DEBUG == 0 */
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/* Like bcopy except never gets confused by overlap.  Let this be the
   first function defined in this file, or change emacs.c where the
   address of this function is used.  */
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void
safe_bcopy (from, to, size)
     char *from, *to;
     int size;
{
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  if (size <= 0 || from == to)
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    return;

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  /* If the source and destination don't overlap, then bcopy can
     handle it.  If they do overlap, but the destination is lower in
     memory than the source, we'll assume bcopy can handle that.  */
  if (to < from || from + size <= to)
    bcopy (from, to, size);

  /* Otherwise, we'll copy from the end.  */
  else
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    {
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      register char *endf = from + size;
      register char *endt = to + size;
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      /* If TO - FROM is large, then we should break the copy into
	 nonoverlapping chunks of TO - FROM bytes each.  However, if
	 TO - FROM is small, then the bcopy function call overhead
	 makes this not worth it.  The crossover point could be about
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	 anywhere.  Since I don't think the obvious copy loop is too
	 bad, I'm trying to err in its favor.  */
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      if (to - from < 64)
	{
	  do
	    *--endt = *--endf;
	  while (endf != from);
	}
      else
	{
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	  for (;;)
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	    {
	      endt -= (to - from);
	      endf -= (to - from);

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	      if (endt < to)
		break;

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	      bcopy (endf, endt, to - from);
	    }
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	  /* If SIZE wasn't a multiple of TO - FROM, there will be a
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	     little left over.  The amount left over is (endt + (to -
	     from)) - to, which is endt - from.  */
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	  bcopy (from, to, endt - from);
	}
    }
}     


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/***********************************************************************
			    Glyph Matrices
 ***********************************************************************/

/* Allocate and return a glyph_matrix structure.  POOL is the glyph
   pool from which memory for the matrix should be allocated, or null
   for window-based redisplay where no glyph pools are used.  The
   member `pool' of the glyph matrix structure returned is set to
   POOL, the structure is otherwise zeroed.  */

struct glyph_matrix *
new_glyph_matrix (pool)
     struct glyph_pool *pool;
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{
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  struct glyph_matrix *result;

  /* Allocate and clear.  */
  result = (struct glyph_matrix *) xmalloc (sizeof *result);
  bzero (result, sizeof *result);
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  /* Increment number of allocated matrices.  This count is used
     to detect memory leaks.  */
  ++glyph_matrix_count;
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  /* Set pool and return.  */
  result->pool = pool;
  return result;
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}


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/* Free glyph matrix MATRIX.  Passing in a null MATRIX is allowed.

   The global counter glyph_matrix_count is decremented when a matrix
   is freed.  If the count gets negative, more structures were freed
   than allocated, i.e. one matrix was freed more than once or a bogus
   pointer was passed to this function.
 
   If MATRIX->pool is null, this means that the matrix manages its own
   glyph memory---this is done for matrices on X frames.  Freeing the
   matrix also frees the glyph memory in this case.  */

static void
free_glyph_matrix (matrix)
     struct glyph_matrix *matrix;
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{
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  if (matrix)
    {
      int i;

      /* Detect the case that more matrices are freed than were
	 allocated.  */
      if (--glyph_matrix_count < 0)
	abort ();

      /* Free glyph memory if MATRIX owns it.  */
      if (matrix->pool == NULL)
	for (i = 0; i < matrix->rows_allocated; ++i)
	  xfree (matrix->rows[i].glyphs[LEFT_MARGIN_AREA]);
      
      /* Free row structures and the matrix itself.  */
      xfree (matrix->rows);
      xfree (matrix);
    }
}
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/* Return the number of glyphs to reserve for a marginal area of
   window W.  TOTAL_GLYPHS is the number of glyphs in a complete
   display line of window W.  MARGIN gives the width of the marginal
   area in canonical character units.  MARGIN should be an integer
   or a float.  */

static int
margin_glyphs_to_reserve (w, total_glyphs, margin)
     struct window *w;
     int total_glyphs;
     Lisp_Object margin;
{
  int n;
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  if (NUMBERP (margin))
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    {
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      int width = XFASTINT (w->width);
      double d = max (0, XFLOATINT (margin));
      d = min (width / 2 - 1, d);
      n = (int) ((double) total_glyphs / width * d);
    }
  else
    n = 0;

  return n;
}

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/* Adjust glyph matrix MATRIX on window W or on a frame to changed
   window sizes.
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   W is null if the function is called for a frame glyph matrix.
   Otherwise it is the window MATRIX is a member of.  X and Y are the
   indices of the first column and row of MATRIX within the frame
   matrix, if such a matrix exists.  They are zero for purely
   window-based redisplay.  DIM is the needed size of the matrix.
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   In window-based redisplay, where no frame matrices exist, glyph
   matrices manage their own glyph storage.  Otherwise, they allocate
   storage from a common frame glyph pool which can be found in
   MATRIX->pool.
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   The reason for this memory management strategy is to avoid complete
   frame redraws if possible.  When we allocate from a common pool, a
   change of the location or size of a sub-matrix within the pool
   requires a complete redisplay of the frame because we cannot easily
   make sure that the current matrices of all windows still agree with
   what is displayed on the screen.  While this is usually fast, it
   leads to screen flickering.  */
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static void
adjust_glyph_matrix (w, matrix, x, y, dim)
     struct window *w;
     struct glyph_matrix *matrix;
     int x, y;
     struct dim dim;
{
  int i;
  int new_rows;
  int marginal_areas_changed_p = 0;
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  int header_line_changed_p = 0;
  int header_line_p = 0;
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  int left = -1, right = -1;
  int window_x, window_y, window_width, window_height;

  /* See if W had a top line that has disappeared now, or vice versa.  */
  if (w)
    {
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      header_line_p = WINDOW_WANTS_HEADER_LINE_P (w);
      header_line_changed_p = header_line_p != matrix->header_line_p;
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    }
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  matrix->header_line_p = header_line_p;
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  /* Do nothing if MATRIX' size, position, vscroll, and marginal areas
     haven't changed.  This optimization is important because preserving
     the matrix means preventing redisplay.  */
  if (matrix->pool == NULL)
    {
      window_box (w, -1, &window_x, &window_y, &window_width, &window_height);
      left = margin_glyphs_to_reserve (w, dim.width, w->left_margin_width);
      right = margin_glyphs_to_reserve (w, dim.width, w->right_margin_width);
      xassert (left >= 0 && right >= 0);
      marginal_areas_changed_p = (left != matrix->left_margin_glyphs
				  || right != matrix->right_margin_glyphs);

      if (!marginal_areas_changed_p
	  && !fonts_changed_p
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	  && !header_line_changed_p
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	  && matrix->window_top_y == XFASTINT (w->top)
	  && matrix->window_height == window_height
	  && matrix->window_vscroll == w->vscroll
	  && matrix->window_width == window_width)
	return;
    }
  
  /* Enlarge MATRIX->rows if necessary.  New rows are cleared.  */
  if (matrix->rows_allocated < dim.height)
    {
      int size = dim.height * sizeof (struct glyph_row);
      new_rows = dim.height - matrix->rows_allocated;
      matrix->rows = (struct glyph_row *) xrealloc (matrix->rows, size);
      bzero (matrix->rows + matrix->rows_allocated,
	     new_rows * sizeof *matrix->rows);
      matrix->rows_allocated = dim.height;
    }
  else
    new_rows = 0;
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  /* If POOL is not null, MATRIX is a frame matrix or a window matrix
     on a frame not using window-based redisplay.  Set up pointers for
     each row into the glyph pool.  */
  if (matrix->pool)
    {
      xassert (matrix->pool->glyphs);
      
      if (w)
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	{
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	  left = margin_glyphs_to_reserve (w, dim.width,
					   w->left_margin_width);
	  right = margin_glyphs_to_reserve (w, dim.width,
					    w->right_margin_width);
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	}
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      else
	left = right = 0;
      
      for (i = 0; i < dim.height; ++i)
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	{
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	  struct glyph_row *row = &matrix->rows[i];
	  
	  row->glyphs[LEFT_MARGIN_AREA] 
	    = (matrix->pool->glyphs
	       + (y + i) * matrix->pool->ncolumns
	       + x);
	  
	  if (w == NULL
	      || row == matrix->rows + dim.height - 1
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	      || (row == matrix->rows && matrix->header_line_p))
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	    {
	      row->glyphs[TEXT_AREA]
		= row->glyphs[LEFT_MARGIN_AREA];
	      row->glyphs[RIGHT_MARGIN_AREA]
		= row->glyphs[TEXT_AREA] + dim.width;
	      row->glyphs[LAST_AREA]
		= row->glyphs[RIGHT_MARGIN_AREA];
	    }
	  else
	    {
	      row->glyphs[TEXT_AREA]
		= row->glyphs[LEFT_MARGIN_AREA] + left;
	      row->glyphs[RIGHT_MARGIN_AREA]
		= row->glyphs[TEXT_AREA] + dim.width - left - right;
	      row->glyphs[LAST_AREA]
		= row->glyphs[LEFT_MARGIN_AREA] + dim.width;
	    }
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	}
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      matrix->left_margin_glyphs = left;
      matrix->right_margin_glyphs = right;
    }
  else
    {
      /* If MATRIX->pool is null, MATRIX is responsible for managing
	 its own memory.  Allocate glyph memory from the heap.  */
      if (dim.width > matrix->matrix_w
	  || new_rows
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	  || header_line_changed_p
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	  || marginal_areas_changed_p)
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	{
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	  struct glyph_row *row = matrix->rows;
	  struct glyph_row *end = row + matrix->rows_allocated;
	  
	  while (row < end)
	    {
	      row->glyphs[LEFT_MARGIN_AREA]
		= (struct glyph *) xrealloc (row->glyphs[LEFT_MARGIN_AREA],
					     (dim.width
					      * sizeof (struct glyph)));
	      
	      /* The mode line never has marginal areas.  */
	      if (row == matrix->rows + dim.height - 1
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		  || (row == matrix->rows && matrix->header_line_p))
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		{
		  row->glyphs[TEXT_AREA]
		    = row->glyphs[LEFT_MARGIN_AREA];
		  row->glyphs[RIGHT_MARGIN_AREA]
		    = row->glyphs[TEXT_AREA] + dim.width;
		  row->glyphs[LAST_AREA]
		    = row->glyphs[RIGHT_MARGIN_AREA];
		}
	      else
		{
		  row->glyphs[TEXT_AREA]
		    = row->glyphs[LEFT_MARGIN_AREA] + left;
		  row->glyphs[RIGHT_MARGIN_AREA]
		    = row->glyphs[TEXT_AREA] + dim.width - left - right;
		  row->glyphs[LAST_AREA]
		    = row->glyphs[LEFT_MARGIN_AREA] + dim.width;
		}
	      ++row;
	    }
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	}

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      xassert (left >= 0 && right >= 0);
      matrix->left_margin_glyphs = left;
      matrix->right_margin_glyphs = right;
    }
  
  /* Number of rows to be used by MATRIX.  */
  matrix->nrows = dim.height;
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  xassert (matrix->nrows >= 0);
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  /* Mark rows in a current matrix of a window as not having valid
     contents.  It's important to not do this for desired matrices.
     When Emacs starts, it may already be building desired matrices
     when this function runs.  */
  if (w && matrix == w->current_matrix)
    {
      /* Optimize the case that only the height has changed (C-x 2,
         upper window).  Invalidate all rows that are no longer part
         of the window.  */
      if (!marginal_areas_changed_p
	  && matrix->window_top_y == XFASTINT (w->top)
	  && matrix->window_width == window_width)
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	{
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	  i = 0;
	  while (matrix->rows[i].enabled_p
		 && (MATRIX_ROW_BOTTOM_Y (matrix->rows + i)
		     < matrix->window_height))
	    ++i;

	  /* Window end is invalid, if inside of the rows that
	     are invalidated.  */
	  if (INTEGERP (w->window_end_vpos)
	      && XFASTINT (w->window_end_vpos) >= i)
	    w->window_end_valid = Qnil;
	  
	  while (i < matrix->nrows)
	    matrix->rows[i++].enabled_p = 0;
	}
      else
	{
	  for (i = 0; i < matrix->nrows; ++i)
	    matrix->rows[i].enabled_p = 0;
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	}
    }
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  /* Remember last values to be able to optimize frame redraws.  */
  matrix->matrix_x = x;
  matrix->matrix_y = y;
  matrix->matrix_w = dim.width;
  matrix->matrix_h = dim.height;

  /* Record the top y location and height of W at the time the matrix
     was last adjusted.  This is used to optimize redisplay above.  */
  if (w)
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    {
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      matrix->window_top_y = XFASTINT (w->top);
      matrix->window_height = window_height;
      matrix->window_width = window_width;
      matrix->window_vscroll = w->vscroll;
    }
}
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/* Reverse the contents of rows in MATRIX between START and END.  The
   contents of the row at END - 1 end up at START, END - 2 at START +
   1 etc.  This is part of the implementation of rotate_matrix (see
   below).  */
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static void
reverse_rows (matrix, start, end)
     struct glyph_matrix *matrix;
     int start, end;
{
  int i, j;
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  for (i = start, j = end - 1; i < j; ++i, --j)
    {
      /* Non-ISO HP/UX compiler doesn't like auto struct
	 initialization.  */
      struct glyph_row temp;
      temp = matrix->rows[i];
      matrix->rows[i] = matrix->rows[j];
      matrix->rows[j] = temp;
    }
}
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/* Rotate the contents of rows in MATRIX in the range FIRST .. LAST -
   1 by BY positions.  BY < 0 means rotate left, i.e. towards lower
   indices.  (Note: this does not copy glyphs, only glyph pointers in
   row structures are moved around).
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   The algorithm used for rotating the vector was, I believe, first
   described by Kernighan.  See the vector R as consisting of two
   sub-vectors AB, where A has length BY for BY >= 0.  The result
   after rotating is then BA.  Reverse both sub-vectors to get ArBr
   and reverse the result to get (ArBr)r which is BA.  Similar for
   rotating right.  */

void
rotate_matrix (matrix, first, last, by)
     struct glyph_matrix *matrix;
     int first, last, by;
{
  if (by < 0)
    {
      /* Up (rotate left, i.e. towards lower indices).  */
      by = -by;
      reverse_rows (matrix, first, first + by);
      reverse_rows (matrix, first + by, last);
      reverse_rows (matrix, first, last);
    }
  else if (by > 0)
    {
      /* Down (rotate right, i.e. towards higher indices).  */
      reverse_rows (matrix, last - by, last);
      reverse_rows (matrix, first, last - by);
      reverse_rows (matrix, first, last);
    }
}


/* Increment buffer positions in glyph rows of MATRIX.  Do it for rows
   with indices START <= index < END.  Increment positions by DELTA/
   DELTA_BYTES.  */

void
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increment_matrix_positions (matrix, start, end, delta, delta_bytes)
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     struct glyph_matrix *matrix;
     int start, end, delta, delta_bytes;
{
  /* Check that START and END are reasonable values.  */
  xassert (start >= 0 && start <= matrix->nrows);
  xassert (end >= 0 && end <= matrix->nrows);
  xassert (start <= end);

  for (; start < end; ++start)
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    increment_row_positions (matrix->rows + start, delta, delta_bytes);
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}


/* Enable a range of rows in glyph matrix MATRIX.  START and END are
   the row indices of the first and last + 1 row to enable.  If
   ENABLED_P is non-zero, enabled_p flags in rows will be set to 1.  */

void
enable_glyph_matrix_rows (matrix, start, end, enabled_p)
     struct glyph_matrix *matrix;
     int start, end;
     int enabled_p;
{
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  xassert (start <= end);
  xassert (start >= 0 && start < matrix->nrows);
  xassert (end >= 0 && end <= matrix->nrows);
  
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  for (; start < end; ++start)
    matrix->rows[start].enabled_p = enabled_p != 0;
}


/* Clear MATRIX.

   This empties all rows in MATRIX by setting the enabled_p flag for
   all rows of the matrix to zero.  The function prepare_desired_row
   will eventually really clear a row when it sees one with a zero
   enabled_p flag.

   Resets update hints to defaults value.  The only update hint
   currently present is the flag MATRIX->no_scrolling_p.  */

void
clear_glyph_matrix (matrix)
     struct glyph_matrix *matrix;
{
  if (matrix)
    {
      enable_glyph_matrix_rows (matrix, 0, matrix->nrows, 0);
      matrix->no_scrolling_p = 0;
    }
}
  

/* Shift part of the glyph matrix MATRIX of window W up or down.
   Increment y-positions in glyph rows between START and END by DY,
   and recompute their visible height.  */

void
shift_glyph_matrix (w, matrix, start, end, dy)
     struct window *w;
     struct glyph_matrix *matrix;
     int start, end, dy;
{
  int min_y, max_y;
  
  xassert (start <= end);
  xassert (start >= 0 && start < matrix->nrows);
  xassert (end >= 0 && end <= matrix->nrows);
  
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  min_y = WINDOW_DISPLAY_HEADER_LINE_HEIGHT (w);
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  max_y = WINDOW_DISPLAY_HEIGHT_NO_MODE_LINE (w);
  
  for (; start < end; ++start)
    {
      struct glyph_row *row = &matrix->rows[start];
      
      row->y += dy;
      
      if (row->y < min_y)
	row->visible_height = row->height - (min_y - row->y);
      else if (row->y + row->height > max_y)
	row->visible_height = row->height - (row->y + row->height - max_y);
      else
	row->visible_height = row->height;
    }
}


/* Mark all rows in current matrices of frame F as invalid.  Marking
   invalid is done by setting enabled_p to zero for all rows in a
   current matrix.  */

void
clear_current_matrices (f)
     register struct frame *f;
{
  /* Clear frame current matrix, if we have one.  */
  if (f->current_matrix)
    clear_glyph_matrix (f->current_matrix);

  /* Clear the matrix of the menu bar window, if such a window exists.
     The menu bar window is currently used to display menus on X when
     no toolkit support is compiled in.  */
  if (WINDOWP (f->menu_bar_window))
    clear_glyph_matrix (XWINDOW (f->menu_bar_window)->current_matrix);

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  /* Clear the matrix of the tool-bar window, if any.  */
  if (WINDOWP (f->tool_bar_window))
    clear_glyph_matrix (XWINDOW (f->tool_bar_window)->current_matrix);
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  /* Clear current window matrices.  */
  xassert (WINDOWP (FRAME_ROOT_WINDOW (f)));
  clear_window_matrices (XWINDOW (FRAME_ROOT_WINDOW (f)), 0);
}


/* Clear out all display lines of F for a coming redisplay.  */

void
clear_desired_matrices (f)
     register struct frame *f;
{
  if (f->desired_matrix)
    clear_glyph_matrix (f->desired_matrix);
  
  if (WINDOWP (f->menu_bar_window))
    clear_glyph_matrix (XWINDOW (f->menu_bar_window)->desired_matrix);

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  if (WINDOWP (f->tool_bar_window))
    clear_glyph_matrix (XWINDOW (f->tool_bar_window)->desired_matrix);
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  /* Do it for window matrices.  */
  xassert (WINDOWP (FRAME_ROOT_WINDOW (f)));
  clear_window_matrices (XWINDOW (FRAME_ROOT_WINDOW (f)), 1);
}


/* Clear matrices in window tree rooted in W.  If DESIRED_P is
   non-zero clear desired matrices, otherwise clear current matrices.  */

static void
clear_window_matrices (w, desired_p)
     struct window *w;
     int desired_p;
{
  while (w)
    {
      if (!NILP (w->hchild))
	{
	  xassert (WINDOWP (w->hchild));
	  clear_window_matrices (XWINDOW (w->hchild), desired_p);
	}
      else if (!NILP (w->vchild))
	{
	  xassert (WINDOWP (w->vchild));
	  clear_window_matrices (XWINDOW (w->vchild), desired_p);
	}
      else
	{
	  if (desired_p)
	    clear_glyph_matrix (w->desired_matrix);
	  else
	    {
	      clear_glyph_matrix (w->current_matrix);
	      w->window_end_valid = Qnil;
	    }
	}

      w = NILP (w->next) ? 0 : XWINDOW (w->next);
    }
}



/***********************************************************************
			      Glyph Rows

      See dispextern.h for an overall explanation of glyph rows.
 ***********************************************************************/

/* Clear glyph row ROW.  Do it in a way that makes it robust against
   changes in the glyph_row structure, i.e. addition or removal of
   structure members.  */

void
clear_glyph_row (row)
     struct glyph_row *row;
{
  struct glyph *p[1 + LAST_AREA];
  static struct glyph_row null_row;

  /* Save pointers.  */
  p[LEFT_MARGIN_AREA] = row->glyphs[LEFT_MARGIN_AREA];
  p[TEXT_AREA] = row->glyphs[TEXT_AREA];
  p[RIGHT_MARGIN_AREA] = row->glyphs[RIGHT_MARGIN_AREA];
  p[LAST_AREA] = row->glyphs[LAST_AREA];

  /* Clear.  */
  *row = null_row;

  /* Restore pointers.  */
  row->glyphs[LEFT_MARGIN_AREA] = p[LEFT_MARGIN_AREA];
  row->glyphs[TEXT_AREA] = p[TEXT_AREA];
  row->glyphs[RIGHT_MARGIN_AREA] = p[RIGHT_MARGIN_AREA];
  row->glyphs[LAST_AREA] = p[LAST_AREA];
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#if 0 /* At some point, some bit-fields of struct glyph were not set,
	 which made glyphs unequal when compared with GLYPH_EQUAL_P.
	 Redisplay outputs such glyphs, and flickering effects were
	 the result.  This also depended on the contents of memory
	 returned by xmalloc.  If flickering happens again, activate
	 the code below If the flickering is gone with that, chances
	 are that the flickering has the same reason as here.  */
  bzero (p[0], (char *) p[LAST_AREA] - (char *) p[0]);
#endif
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}


/* Make ROW an empty, enabled row of canonical character height,
   in window W starting at y-position Y.  */

void
blank_row (w, row, y)
     struct window *w;
     struct glyph_row *row;
     int y;
{
  int min_y, max_y;
  
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  min_y = WINDOW_DISPLAY_HEADER_LINE_HEIGHT (w);
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  max_y = WINDOW_DISPLAY_HEIGHT_NO_MODE_LINE (w);
  
  clear_glyph_row (row);
  row->y = y;
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  row->ascent = row->phys_ascent = 0;
  row->height = row->phys_height = CANON_Y_UNIT (XFRAME (w->frame));
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  if (row->y < min_y)
    row->visible_height = row->height - (min_y - row->y);
  else if (row->y + row->height > max_y)
    row->visible_height = row->height - (row->y + row->height - max_y);
  else
    row->visible_height = row->height;

  row->enabled_p = 1;
}


/* Increment buffer positions in glyph row ROW.  DELTA and DELTA_BYTES
   are the amounts by which to change positions.  Note that the first
   glyph of the text area of a row can have a buffer position even if
   the used count of the text area is zero.  Such rows display line
   ends.  */

void
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increment_row_positions (row, delta, delta_bytes)
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     struct glyph_row *row;
     int delta, delta_bytes;
{
  int area, i;

  /* Increment start and end positions.  */
  MATRIX_ROW_START_CHARPOS (row) += delta;
  MATRIX_ROW_START_BYTEPOS (row) += delta_bytes;
  MATRIX_ROW_END_CHARPOS (row) += delta;
  MATRIX_ROW_END_BYTEPOS (row) += delta_bytes;

  /* Increment positions in glyphs.  */
  for (area = 0; area < LAST_AREA; ++area)
    for (i = 0; i < row->used[area]; ++i)
      if (BUFFERP (row->glyphs[area][i].object)
	  && row->glyphs[area][i].charpos > 0)
	row->glyphs[area][i].charpos += delta;

  /* Capture the case of rows displaying a line end.  */
  if (row->used[TEXT_AREA] == 0
      && MATRIX_ROW_DISPLAYS_TEXT_P (row))
    row->glyphs[TEXT_AREA]->charpos += delta;
}


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#if 0
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/* Swap glyphs between two glyph rows A and B.  This exchanges glyph
   contents, i.e. glyph structure contents are exchanged between A and
   B without changing glyph pointers in A and B.  */

static void
swap_glyphs_in_rows (a, b)
     struct glyph_row *a, *b;
{
  int area;

  for (area = 0; area < LAST_AREA; ++area)
    {
      /* Number of glyphs to swap.  */
      int max_used = max (a->used[area], b->used[area]);

      /* Start of glyphs in area of row A.  */
      struct glyph *glyph_a = a->glyphs[area];

      /* End + 1 of glyphs in area of row A.  */
      struct glyph *glyph_a_end = a->glyphs[max_used];

      /* Start of glyphs in area of row B.  */
      struct glyph *glyph_b = b->glyphs[area];

      while (glyph_a < glyph_a_end)
	{
	  /* Non-ISO HP/UX compiler doesn't like auto struct
             initialization.  */
	  struct glyph temp;
	  temp = *glyph_a;
	  *glyph_a = *glyph_b;
	  *glyph_b = temp;
	  ++glyph_a;
	  ++glyph_b;
	}
    }
}

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#endif /* 0 */
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/* Exchange pointers to glyph memory between glyph rows A and B.  */

static INLINE void
swap_glyph_pointers (a, b)
     struct glyph_row *a, *b;
{
  int i;
  for (i = 0; i < LAST_AREA + 1; ++i)
    {
      struct glyph *temp = a->glyphs[i];
      a->glyphs[i] = b->glyphs[i];
      b->glyphs[i] = temp;
    }
}


/* Copy glyph row structure FROM to glyph row structure TO, except
   that glyph pointers in the structures are left unchanged.  */

INLINE void
copy_row_except_pointers (to, from)
     struct glyph_row *to, *from;
{
  struct glyph *pointers[1 + LAST_AREA];

  /* Save glyph pointers of TO.  */
  bcopy (to->glyphs, pointers, sizeof to->glyphs);

  /* Do a structure assignment.  */
  *to = *from;

  /* Restore original pointers of TO.  */
  bcopy (pointers, to->glyphs, sizeof to->glyphs);
}


/* Copy contents of glyph row FROM to glyph row TO.  Glyph pointers in
   TO and FROM are left unchanged.  Glyph contents are copied from the
   glyph memory of FROM to the glyph memory of TO.  Increment buffer
   positions in row TO by DELTA/ DELTA_BYTES.  */

void
copy_glyph_row_contents (to, from, delta, delta_bytes)
     struct glyph_row *to, *from;
     int delta, delta_bytes;
{
  int area;

  /* This is like a structure assignment TO = FROM, except that
     glyph pointers in the rows are left unchanged.  */
  copy_row_except_pointers (to, from);

  /* Copy glyphs from FROM to TO.  */
  for (area = 0; area < LAST_AREA; ++area)
    if (from->used[area])
      bcopy (from->glyphs[area], to->glyphs[area], 
	     from->used[area] * sizeof (struct glyph));

  /* Increment buffer positions in TO by DELTA.  */
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  increment_row_positions (to, delta, delta_bytes);
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}


/* Assign glyph row FROM to glyph row TO.  This works like a structure
   assignment TO = FROM, except that glyph pointers are not copied but
   exchanged between TO and FROM.  Pointers must be exchanged to avoid
   a memory leak.  */

static INLINE void
assign_row (to, from)
     struct glyph_row *to, *from;
{
  swap_glyph_pointers (to, from);
  copy_row_except_pointers (to, from);
}


/* Test whether the glyph memory of the glyph row WINDOW_ROW, which is
   a row in a window matrix, is a slice of the glyph memory of the
   glyph row FRAME_ROW which is a row in a frame glyph matrix.  Value
   is non-zero if the glyph memory of WINDOW_ROW is part of the glyph
   memory of FRAME_ROW.  */

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#ifdef GLYPH_DEBUG

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static int
glyph_row_slice_p (window_row, frame_row)
     struct glyph_row *window_row, *frame_row;
{
  struct glyph *window_glyph_start = window_row->glyphs[0];
  struct glyph *frame_glyph_start = frame_row->glyphs[0];
  struct glyph *frame_glyph_end = frame_row->glyphs[LAST_AREA];

  return (frame_glyph_start <= window_glyph_start
	  && window_glyph_start < frame_glyph_end);
}

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#endif /* GLYPH_DEBUG */
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#if 0

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/* Find the row in the window glyph matrix WINDOW_MATRIX being a slice
   of ROW in the frame matrix FRAME_MATRIX.  Value is null if no row
   in WINDOW_MATRIX is found satisfying the condition.  */

static struct glyph_row *
find_glyph_row_slice (window_matrix, frame_matrix, row)
     struct glyph_matrix *window_matrix, *frame_matrix;
     int row;
{
  int i;

  xassert (row >= 0 && row < frame_matrix->nrows);

  for (i = 0; i < window_matrix->nrows; ++i)
    if (glyph_row_slice_p (window_matrix->rows + i,
			   frame_matrix->rows + row))
      break;

  return i < window_matrix->nrows ? window_matrix->rows + i : 0;
}

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#endif /* 0 */
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/* Prepare ROW for display.  Desired rows are cleared lazily,
   i.e. they are only marked as to be cleared by setting their
   enabled_p flag to zero.  When a row is to be displayed, a prior
   call to this function really clears it.  */

void
prepare_desired_row (row)
     struct glyph_row *row;
{
  if (!row->enabled_p)
    {
      clear_glyph_row (row);
      row->enabled_p = 1;
    }
}


/* Return a hash code for glyph row ROW.  */

int
line_hash_code (row)
     struct glyph_row *row;
{
  int hash = 0;
  
  if (row->enabled_p)
    {
      if (row->inverse_p)
        {
          /* Give all highlighted lines the same hash code
	     so as to encourage scrolling to leave them in place.  */
          hash = -1;
        }
      else
        {
          struct glyph *glyph = row->glyphs[TEXT_AREA];