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/* Display generation from window structure and buffer text.
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   Copyright (C) 1985, 86, 87, 88, 93, 94, 95, 97, 98, 99
   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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/* New redisplay written by Gerd Moellmann <gerd@gnu.org>.

   Redisplay.

   Emacs separates the task of updating the display from code
   modifying global state, e.g. buffer text.  This way functions
   operating on buffers don't also have to be concerned with updating
   the display.

   Updating the display is triggered by the Lisp interpreter when it
   decides it's time to do it.  This is done either automatically for
   you as part of the interpreter's command loop or as the result of
   calling Lisp functions like `sit-for'.  The C function `redisplay'
   in xdisp.c is the only entry into the inner redisplay code.  (Or,
   let's say almost---see the the description of direct update
   operations, below.).

   The following diagram shows how redisplay code is invoked.  As you
   can see, Lisp calls redisplay and vice versa.  Under window systems
   like X, some portions of the redisplay code are also called
   asynchronously during mouse movement or expose events.  It is very
   important that these code parts do NOT use the C library (malloc,
   free) because many C libraries under Unix are not reentrant.  They
   may also NOT call functions of the Lisp interpreter which could
   change the interpreter's state.  If you don't follow these rules,
   you will encounter bugs which are very hard to explain.

	     (Direct functions, see below)
             direct_output_for_insert, 
             direct_forward_char (dispnew.c)
   	  +---------------------------------+
          |                                 |
	  |                                 V
   +--------------+   redisplay()   +----------------+
   | Lisp machine |---------------->| Redisplay code |<--+
   +--------------+   (xdisp.c)     +----------------+   |
	  ^				     |		 |
	  +----------------------------------+           |
	    Don't use this path when called		 |
	    asynchronously!				 |
                                                         |
                           expose_window (asynchronous)  |
                                                         |
			           X expose events  -----+

   What does redisplay?  Obviously, it has to figure out somehow what
   has been changed since the last time the display has been updated,
   and to make these changes visible.  Preferably it would do that in
   a moderately intelligent way, i.e. fast.

   Changes in buffer text can be deduced from window and buffer
   structures, and from some global variables like `beg_unchanged' and
   `end_unchanged'.  The contents of the display are additionally
   recorded in a `glyph matrix', a two-dimensional matrix of glyph
   structures.  Each row in such a matrix corresponds to a line on the
   display, and each glyph in a row corresponds to a column displaying
   a character, an image, or what else.  This matrix is called the
   `current glyph matrix' or `current matrix' in redisplay
   terminology.

   For buffer parts that have been changed since the last update, a
   second glyph matrix is constructed, the so called `desired glyph
   matrix' or short `desired matrix'.  Current and desired matrix are
   then compared to find a cheap way to update the display, e.g. by
   reusing part of the display by scrolling lines.


   Direct operations.

   You will find a lot of of redisplay optimizations when you start
   looking at the innards of redisplay.  The overall goal of all these
   optimizations is to make redisplay fast because it is done
   frequently.

   Two optimizations are not found in xdisp.c.  These are the direct
   operations mentioned above.  As the name suggests they follow a
   different principle than the rest of redisplay.  Instead of
   building a desired matrix and then comparing it with the current
   display, they perform their actions directly on the display and on
   the current matrix.

   One direct operation updates the display after one character has
   been entered.  The other one moves the cursor by one position
   forward or backward.  You find these functions under the names
   `direct_output_for_insert' and `direct_output_forward_char' in
   dispnew.c.

   
   Desired matrices.

   Desired matrices are always built per Emacs window.  The function
   `display_line' is the central function to look at if you are
   interested.  It constructs one row in a desired matrix given an
   iterator structure containing both a buffer position and a
   description of the environment in which the text is to be
   displayed.  But this is too early, read on.

   Characters and pixmaps displayed for a range of buffer text depend
   on various settings of buffers and windows, on overlays and text
   properties, on display tables, on selective display.  The good news
   is that all this hairy stuff is hidden behind a small set of
   interface functions taking a iterator structure (struct it)
   argument.

   Iteration over things to be be displayed is then simple.  It is
   started by initializing an iterator with a call to init_iterator
   (or init_string_iterator for that matter).  Calls to
   get_next_display_element fill the iterator structure with relevant
   information about the next thing to display.  Calls to
   set_iterator_to_next move the iterator to the next thing.

   Besides this, an iterator also contains information about the
   display environment in which glyphs for display elements are to be
   produced.  It has fields for the width and height of the display,
   the information whether long lines are truncated or continued, a
   current X and Y position, and lots of other stuff you can better
   see in dispextern.h.

   Glyphs in a desired matrix are normally constructed in a loop
   calling get_next_display_element and then produce_glyphs.  The call
   to produce_glyphs will fill the iterator structure with pixel
   information about the element being displayed and at the same time
   produce glyphs for it.  If the display element fits on the line
   being displayed, set_iterator_to_next is called next, otherwise the
   glyphs produced are discarded.


   Frame matrices.

   That just couldn't be all, could it?  What about terminal types not
   supporting operations on sub-windows of the screen?  To update the
   display on such a terminal, window-based glyph matrices are not
   well suited.  To be able to reuse part of the display (scrolling
   lines up and down), we must instead have a view of the whole
   screen.  This is what `frame matrices' are for.  They are a trick.

   Frames on terminals like above have a glyph pool.  Windows on such
   a frame sub-allocate their glyph memory from their frame's glyph
   pool.  The frame itself is given its own glyph matrices.  By
   coincidence---or maybe something else---rows in window glyph
   matrices are slices of corresponding rows in frame matrices.  Thus
   writing to window matrices implicitly updates a frame matrix which
   provides us with the view of the whole screen that we originally
   wanted to have without having to move many bytes around.  To be
   honest, there is a little bit more done, but not much more.  If you
   plan to extend that code, take a look at dispnew.c.  The function
   build_frame_matrix is a good starting point.  */
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#include <config.h>
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#include <stdio.h>
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#ifdef STDC_HEADERS
#include <stdlib.h>
#endif
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#include "lisp.h"
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#include "frame.h"
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#include "window.h"
#include "termchar.h"
#include "dispextern.h"
#include "buffer.h"
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#include "charset.h"
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#include "indent.h"
#include "commands.h"
#include "macros.h"
#include "disptab.h"
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#include "termhooks.h"
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#include "intervals.h"
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#include "keyboard.h"
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#include "coding.h"
#include "process.h"
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#include "region-cache.h"

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#ifdef HAVE_X_WINDOWS
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#include "xterm.h"
#endif
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#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

#define INFINITY 10000000

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#if defined (USE_X_TOOLKIT) || defined (HAVE_NTGUI)
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extern void set_frame_menubar ();
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extern int pending_menu_activation;
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#endif

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extern int interrupt_input;
extern int command_loop_level;

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extern int minibuffer_auto_raise;

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extern Lisp_Object Qface;

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extern Lisp_Object Voverriding_local_map;
extern Lisp_Object Voverriding_local_map_menu_flag;
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extern Lisp_Object Qmenu_item;
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Lisp_Object Qoverriding_local_map, Qoverriding_terminal_local_map;
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Lisp_Object Qwindow_scroll_functions, Vwindow_scroll_functions;
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Lisp_Object Qredisplay_end_trigger_functions;
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Lisp_Object Qinhibit_point_motion_hooks;
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Lisp_Object QCeval, Qwhen, QCfile;
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Lisp_Object Qfontified;

/* Functions called to fontify regions of text.  */

Lisp_Object Vfontification_functions;
Lisp_Object Qfontification_functions;

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/* Non-zero means draw tool bar buttons raised when the mouse moves
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   over them.  */

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int auto_raise_tool_bar_buttons_p;
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/* Margin around tool bar buttons in pixels.  */
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int tool_bar_button_margin;
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/* Thickness of shadow to draw around tool bar buttons.  */
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int tool_bar_button_relief;
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/* Non-zero means automatically resize tool-bars so that all tool-bar
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   items are visible, and no blank lines remain.  */

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int auto_resize_tool_bars_p;
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/* Non-nil means don't actually do any redisplay.  */

Lisp_Object Vinhibit_redisplay, Qinhibit_redisplay;

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/* Names of text properties relevant for redisplay.  */

Lisp_Object Qdisplay, Qrelative_width, Qwidth, Qalign_to;
extern Lisp_Object Qface, Qinvisible, Qimage;

/* Symbols used in text property values.  */

Lisp_Object Qspace, QCalign_to, QCrelative_width, QCrelative_height;
Lisp_Object Qleft_margin, Qright_margin, Qspace_width, Qheight, Qraise;
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Lisp_Object Qmargin;
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/* Non-nil means highlight trailing whitespace.  */
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Lisp_Object Vshow_trailing_whitespace;
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/* Name of the face used to highlight trailing whitespace.  */

Lisp_Object Qtrailing_whitespace;

/* The symbol `image' which is the car of the lists used to represent
   images in Lisp.  */

Lisp_Object Qimage;

/* Non-zero means print newline to stdout before next mini-buffer
   message.  */
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int noninteractive_need_newline;

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/* Non-zero means print newline to message log before next message.  */
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static int message_log_need_newline;
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/* The buffer position of the first character appearing entirely or
   partially on the line of the selected window which contains the
   cursor; <= 0 if not known.  Set by set_cursor_from_row, used for
   redisplay optimization in redisplay_internal.  */
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static struct text_pos this_line_start_pos;
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/* Number of characters past the end of the line above, including the
   terminating newline.  */

static struct text_pos this_line_end_pos;

/* The vertical positions and the height of this line.  */
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static int this_line_vpos;
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static int this_line_y;
static int this_line_pixel_height;

/* X position at which this display line starts.  Usually zero;
   negative if first character is partially visible.  */

static int this_line_start_x;
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/* Buffer that this_line_.* variables are referring to.  */
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static struct buffer *this_line_buffer;

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/* Nonzero means truncate lines in all windows less wide than the
   frame.  */
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int truncate_partial_width_windows;

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/* A flag to control how to display unibyte 8-bit character.  */
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int unibyte_display_via_language_environment;
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/* Nonzero means we have more than one non-mini-buffer-only frame.
   Not guaranteed to be accurate except while parsing
   frame-title-format.  */
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int multiple_frames;

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Lisp_Object Vglobal_mode_string;

/* Marker for where to display an arrow on top of the buffer text.  */
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Lisp_Object Voverlay_arrow_position;

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/* String to display for the arrow.  Only used on terminal frames.  */

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Lisp_Object Voverlay_arrow_string;

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/* Values of those variables at last redisplay.  However, if
   Voverlay_arrow_position is a marker, last_arrow_position is its
   numerical position.  */

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static Lisp_Object last_arrow_position, last_arrow_string;

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/* Like mode-line-format, but for the title bar on a visible frame.  */

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Lisp_Object Vframe_title_format;

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/* Like mode-line-format, but for the title bar on an iconified frame.  */

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Lisp_Object Vicon_title_format;

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/* List of functions to call when a window's size changes.  These
   functions get one arg, a frame on which one or more windows' sizes
   have changed.  */
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static Lisp_Object Vwindow_size_change_functions;

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Lisp_Object Qmenu_bar_update_hook;

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/* Nonzero if overlay arrow has been displayed once in this window.  */

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static int overlay_arrow_seen;
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/* Nonzero means highlight the region even in nonselected windows.  */

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int highlight_nonselected_windows;

/* If cursor motion alone moves point off frame, try scrolling this
   many lines up or down if that will bring it back.  */

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static int scroll_step;
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/* Non-0 means scroll just far enough to bring point back on the
   screen, when appropriate.  */

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static int scroll_conservatively;

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/* Recenter the window whenever point gets within this many lines of
   the top or bottom of the window.  This value is translated into a
   pixel value by multiplying it with CANON_Y_UNIT, which means that
   there is really a fixed pixel height scroll margin.  */

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int scroll_margin;

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/* Number of windows showing the buffer of the selected window (or
   another buffer with the same base buffer).  keyboard.c refers to
   this.  */
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int buffer_shared;

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/* Vector containing glyphs for an ellipsis `...'.  */
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static Lisp_Object default_invis_vector[3];
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/* Nonzero means display mode line highlighted.  */
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int mode_line_inverse_video;

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/* Prompt to display in front of the mini-buffer contents.  */

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Lisp_Object minibuf_prompt;
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/* Width of current mini-buffer prompt.  Only set after display_line
   of the line that contains the prompt.  */

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int minibuf_prompt_width;
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int minibuf_prompt_pixel_width;

/* This is the window where the echo area message was displayed.  It
   is always a mini-buffer window, but it may not be the same window
   currently active as a mini-buffer.  */

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Lisp_Object echo_area_window;

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/* List of pairs (MESSAGE . MULTIBYTE).  The function save_message
   pushes the current message and the value of
   message_enable_multibyte on the stack, the function restore_message
   pops the stack and displays MESSAGE again.  */

Lisp_Object Vmessage_stack;

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/* Nonzero means multibyte characters were enabled when the echo area
   message was specified.  */
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int message_enable_multibyte;

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/* True if we should redraw the mode lines on the next redisplay.  */

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int update_mode_lines;

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/* Nonzero if window sizes or contents have changed since last
   redisplay that finished */

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int windows_or_buffers_changed;

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/* Nonzero after display_mode_line if %l was used and it displayed a
   line number.  */

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int line_number_displayed;

/* Maximum buffer size for which to display line numbers.  */
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static int line_number_display_limit;
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/* line width to consider when repostioning for line number display */

static int line_number_display_limit_width;

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/* Number of lines to keep in the message log buffer.  t means
   infinite.  nil means don't log at all.  */

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Lisp_Object Vmessage_log_max;
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/* Current, index 0, and last displayed echo area message.  Either
   buffers from echo_buffers, or nil to indicate no message.  */

Lisp_Object echo_area_buffer[2];

/* The buffers referenced from echo_area_buffer.  */

static Lisp_Object echo_buffer[2];

/* A vector saved used in with_area_buffer to reduce consing.  */

static Lisp_Object Vwith_echo_area_save_vector;

/* Non-zero means display_echo_area should display the last echo area
   message again.  Set by redisplay_preserve_echo_area.  */

static int display_last_displayed_message_p;

/* Nonzero if echo area is being used by print; zero if being used by
   message.  */

int message_buf_print;

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/* Maximum height for resizing mini-windows.  Either a float
   specifying a fraction of the available height, or an integer
   specifying a number of lines.  */
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static Lisp_Object Vmax_mini_window_height;

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/* A scratch glyph row with contents used for generating truncation
   glyphs.  Also used in direct_output_for_insert.  */
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#define MAX_SCRATCH_GLYPHS 100
struct glyph_row scratch_glyph_row;
static struct glyph scratch_glyphs[MAX_SCRATCH_GLYPHS];
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/* Ascent and height of the last line processed by move_it_to.  */

static int last_max_ascent, last_height;

/* The maximum distance to look ahead for text properties.  Values
   that are too small let us call compute_char_face and similar 
   functions too often which is expensive.  Values that are too large
   let us call compute_char_face and alike too often because we
   might not be interested in text properties that far away.  */

#define TEXT_PROP_DISTANCE_LIMIT 100

/* Non-zero means print traces of redisplay if compiled with
   GLYPH_DEBUG != 0.  */

#if GLYPH_DEBUG
int trace_redisplay_p;
#endif

/* Value returned from text property handlers (see below).  */

enum prop_handled
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{
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  HANDLED_NORMALLY,
  HANDLED_RECOMPUTE_PROPS,
  HANDLED_OVERLAY_STRING_CONSUMED,
  HANDLED_RETURN
};
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/* A description of text properties that redisplay is interested
   in.  */
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struct props
{
  /* The name of the property.  */
  Lisp_Object *name;
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  /* A unique index for the property.  */
  enum prop_idx idx;

  /* A handler function called to set up iterator IT from the property
     at IT's current position.  Value is used to steer handle_stop.  */
  enum prop_handled (*handler) P_ ((struct it *it));
};

static enum prop_handled handle_face_prop P_ ((struct it *));
static enum prop_handled handle_invisible_prop P_ ((struct it *));
static enum prop_handled handle_display_prop P_ ((struct it *));
static enum prop_handled handle_overlay_change P_ ((struct it *));
static enum prop_handled handle_fontified_prop P_ ((struct it *));

/* Properties handled by iterators.  */

static struct props it_props[] =
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{
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  {&Qfontified,		FONTIFIED_PROP_IDX,	handle_fontified_prop},
  /* Handle `face' before `display' because some sub-properties of
     `display' need to know the face.  */
  {&Qface,		FACE_PROP_IDX,		handle_face_prop},
  {&Qdisplay,		DISPLAY_PROP_IDX,	handle_display_prop},
  {&Qinvisible,		INVISIBLE_PROP_IDX,	handle_invisible_prop},
  {NULL,		0,			NULL}
};
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/* Value is the position described by X.  If X is a marker, value is
   the marker_position of X.  Otherwise, value is X.  */
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#define COERCE_MARKER(X) (MARKERP ((X)) ? Fmarker_position (X) : (X))
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/* Enumeration returned by some move_it_.* functions internally.  */
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enum move_it_result
{
  /* Not used.  Undefined value.  */
  MOVE_UNDEFINED,
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  /* Move ended at the requested buffer position or ZV.  */
  MOVE_POS_MATCH_OR_ZV,
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  /* Move ended at the requested X pixel position.  */
  MOVE_X_REACHED,
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  /* Move within a line ended at the end of a line that must be
     continued.  */
  MOVE_LINE_CONTINUED,
  
  /* Move within a line ended at the end of a line that would
     be displayed truncated.  */
  MOVE_LINE_TRUNCATED,
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  /* Move within a line ended at a line end.  */
  MOVE_NEWLINE_OR_CR
};
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/* Function prototypes.  */

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static struct glyph_row *row_containing_pos P_ ((struct window *, int,
						 struct glyph_row *,
						 struct glyph_row *));
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static Lisp_Object unwind_with_echo_area_buffer P_ ((Lisp_Object));
static Lisp_Object with_echo_area_buffer_unwind_data P_ ((struct window *));
static void clear_garbaged_frames P_ ((void));
static int current_message_1 P_ ((Lisp_Object *));
static int truncate_message_1 P_ ((int));
static int set_message_1 P_ ((char *s, Lisp_Object, int, int));
static int display_echo_area P_ ((struct window *));
static int display_echo_area_1 P_ ((struct window *));
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static Lisp_Object unwind_redisplay P_ ((Lisp_Object));
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static int string_char_and_length P_ ((unsigned char *, int, int *));
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static struct text_pos display_prop_end P_ ((struct it *, Lisp_Object,
					     struct text_pos));
static int compute_window_start_on_continuation_line P_ ((struct window *));
static Lisp_Object eval_handler P_ ((Lisp_Object));
static Lisp_Object eval_form P_ ((Lisp_Object));
static void insert_left_trunc_glyphs P_ ((struct it *));
static struct glyph_row *get_overlay_arrow_glyph_row P_ ((struct window *));
static void extend_face_to_end_of_line P_ ((struct it *));
static void append_space P_ ((struct it *, int));
static void make_cursor_line_fully_visible P_ ((struct window *));
static int try_scrolling P_ ((Lisp_Object, int, int, int, int));
static int trailing_whitespace_p P_ ((int));
static int message_log_check_duplicate P_ ((int, int, int, int));
int invisible_p P_ ((Lisp_Object, Lisp_Object));
int invisible_ellipsis_p P_ ((Lisp_Object, Lisp_Object));
static void push_it P_ ((struct it *));
static void pop_it P_ ((struct it *));
static void sync_frame_with_window_matrix_rows P_ ((struct window *));
static void redisplay_internal P_ ((int));
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static int echo_area_display P_ ((int));
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static void redisplay_windows P_ ((Lisp_Object));
static void redisplay_window P_ ((Lisp_Object, int));
static void update_menu_bar P_ ((struct frame *, int));
static int try_window_reusing_current_matrix P_ ((struct window *));
static int try_window_id P_ ((struct window *));
static int display_line P_ ((struct it *));
static void display_mode_lines P_ ((struct window *));
static void display_mode_line P_ ((struct window *, enum face_id,
				   Lisp_Object));
static int display_mode_element P_ ((struct it *, int, int, int, Lisp_Object));
static char *decode_mode_spec P_ ((struct window *, char, int, int));
static void display_menu_bar P_ ((struct window *));
static int display_count_lines P_ ((int, int, int, int, int *));
static int display_string P_ ((unsigned char *, Lisp_Object, Lisp_Object,
			       int, int, struct it *, int, int, int, int));
static void compute_line_metrics P_ ((struct it *));
static void run_redisplay_end_trigger_hook P_ ((struct it *));
static int get_overlay_strings P_ ((struct it *));
static void next_overlay_string P_ ((struct it *));
void set_iterator_to_next P_ ((struct it *));
static void reseat P_ ((struct it *, struct text_pos, int));
static void reseat_1 P_ ((struct it *, struct text_pos, int));
static void back_to_previous_visible_line_start P_ ((struct it *));
static void reseat_at_previous_visible_line_start P_ ((struct it *));
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static void reseat_at_next_visible_line_start P_ ((struct it *, int));
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static int next_element_from_display_vector P_ ((struct it *));
static int next_element_from_string P_ ((struct it *));
static int next_element_from_c_string P_ ((struct it *));
static int next_element_from_buffer P_ ((struct it *));
static int next_element_from_image P_ ((struct it *));
static int next_element_from_stretch P_ ((struct it *));
static void load_overlay_strings P_ ((struct it *));
static void init_from_display_pos P_ ((struct it *, struct window *,
				       struct display_pos *));
static void reseat_to_string P_ ((struct it *, unsigned char *,
				  Lisp_Object, int, int, int, int));
static int charset_at_position P_ ((struct text_pos));
static enum move_it_result move_it_in_display_line_to P_ ((struct it *,
							   int, int, int));
void move_it_vertically_backward P_ ((struct it *, int));
static void init_to_row_start P_ ((struct it *, struct window *,
				   struct glyph_row *));
static void init_to_row_end P_ ((struct it *, struct window *,
				 struct glyph_row *));
static void back_to_previous_line_start P_ ((struct it *));
static void forward_to_next_line_start P_ ((struct it *));
static struct text_pos string_pos_nchars_ahead P_ ((struct text_pos,
						    Lisp_Object, int));
static struct text_pos string_pos P_ ((int, Lisp_Object));
static struct text_pos c_string_pos P_ ((int, unsigned char *, int));
static int number_of_chars P_ ((unsigned char *, int));
static void compute_stop_pos P_ ((struct it *));
static void compute_string_pos P_ ((struct text_pos *, struct text_pos,
				    Lisp_Object));
static int face_before_or_after_it_pos P_ ((struct it *, int));
static int next_overlay_change P_ ((int));
static int handle_single_display_prop P_ ((struct it *, Lisp_Object,
					   Lisp_Object, struct text_pos *));

#define face_before_it_pos(IT) face_before_or_after_it_pos ((IT), 1)
#define face_after_it_pos(IT)  face_before_or_after_it_pos ((IT), 0)
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#ifdef HAVE_WINDOW_SYSTEM
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static void update_tool_bar P_ ((struct frame *, int));
static void build_desired_tool_bar_string P_ ((struct frame *f));
static int redisplay_tool_bar P_ ((struct frame *));
static void display_tool_bar_line P_ ((struct it *));
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#endif /* HAVE_WINDOW_SYSTEM */
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/***********************************************************************
		      Window display dimensions
 ***********************************************************************/
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/* Return the window-relative maximum y + 1 for glyph rows displaying
   text in window W.  This is the height of W minus the height of a
   mode line, if any.  */

INLINE int
window_text_bottom_y (w)
     struct window *w;
{
  struct frame *f = XFRAME (w->frame);
  int height = XFASTINT (w->height) * CANON_Y_UNIT (f);
  
  if (WINDOW_WANTS_MODELINE_P (w))
    height -= CURRENT_MODE_LINE_HEIGHT (w);
  return height;
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}

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/* Return the pixel width of display area AREA of window W.  AREA < 0
   means return the total width of W, not including bitmap areas to
   the left and right of the window.  */
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INLINE int
window_box_width (w, area)
     struct window *w;
     int area;
{
  struct frame *f = XFRAME (w->frame);
  int width = XFASTINT (w->width);
  
  if (!w->pseudo_window_p)
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    {
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      width -= FRAME_SCROLL_BAR_WIDTH (f) + FRAME_FLAGS_AREA_COLS (f);
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      if (area == TEXT_AREA)
	{
	  if (INTEGERP (w->left_margin_width))
	    width -= XFASTINT (w->left_margin_width);
	  if (INTEGERP (w->right_margin_width))
	    width -= XFASTINT (w->right_margin_width);
	}
      else if (area == LEFT_MARGIN_AREA)
	width = (INTEGERP (w->left_margin_width)
		 ? XFASTINT (w->left_margin_width) : 0);
      else if (area == RIGHT_MARGIN_AREA)
	width = (INTEGERP (w->right_margin_width)
		 ? XFASTINT (w->right_margin_width) : 0);
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    }
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  return width * CANON_X_UNIT (f);
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}
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/* Return the pixel height of the display area of window W, not
   including mode lines of W, if any..  */
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INLINE int
window_box_height (w)
     struct window *w;
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{
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  struct frame *f = XFRAME (w->frame);
  int height = XFASTINT (w->height) * CANON_Y_UNIT (f);
  
  if (WINDOW_WANTS_MODELINE_P (w))
    height -= CURRENT_MODE_LINE_HEIGHT (w);

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  if (WINDOW_WANTS_HEADER_LINE_P (w))
    height -= CURRENT_HEADER_LINE_HEIGHT (w);
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  return height;
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}


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/* Return the frame-relative coordinate of the left edge of display
   area AREA of window W.  AREA < 0 means return the left edge of the
   whole window, to the right of any bitmap area at the left side of
   W.  */
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INLINE int
window_box_left (w, area)
     struct window *w;
     int area;
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{
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  struct frame *f = XFRAME (w->frame);
  int x = FRAME_INTERNAL_BORDER_WIDTH_SAFE (f);
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  if (!w->pseudo_window_p)
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    {
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      x += (WINDOW_LEFT_MARGIN (w) * CANON_X_UNIT (f)
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	    + FRAME_LEFT_FLAGS_AREA_WIDTH (f));
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      if (area == TEXT_AREA)
	x += window_box_width (w, LEFT_MARGIN_AREA);
      else if (area == RIGHT_MARGIN_AREA)
	x += (window_box_width (w, LEFT_MARGIN_AREA)
	      + window_box_width (w, TEXT_AREA));
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    }
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  return x;
}     
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/* Return the frame-relative coordinate of the right edge of display
   area AREA of window W.  AREA < 0 means return the left edge of the
   whole window, to the left of any bitmap area at the right side of
   W.  */
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INLINE int
window_box_right (w, area)
     struct window *w;
     int area;
{
  return window_box_left (w, area) + window_box_width (w, area);
}     
     

/* Get the bounding box of the display area AREA of window W, without
   mode lines, in frame-relative coordinates.  AREA < 0 means the
   whole window, not including bitmap areas to the left and right of
   the window.  Return in *BOX_X and *BOX_Y the frame-relative pixel
   coordinates of the upper-left corner of the box.  Return in
   *BOX_WIDTH, and *BOX_HEIGHT the pixel width and height of the box.  */

INLINE void
window_box (w, area, box_x, box_y, box_width, box_height)
     struct window *w;
     int area;
     int *box_x, *box_y, *box_width, *box_height;
{
  struct frame *f = XFRAME (w->frame);
  
  *box_width = window_box_width (w, area);
  *box_height = window_box_height (w);
  *box_x = window_box_left (w, area);
  *box_y = (FRAME_INTERNAL_BORDER_WIDTH_SAFE (f)
	    + XFASTINT (w->top) * CANON_Y_UNIT (f));
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  if (WINDOW_WANTS_HEADER_LINE_P (w))
    *box_y += CURRENT_HEADER_LINE_HEIGHT (w);
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}
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/* Get the bounding box of the display area AREA of window W, without
   mode lines.  AREA < 0 means the whole window, not including bitmap
   areas to the left and right of the window.  Return in *TOP_LEFT_X
   and TOP_LEFT_Y the frame-relative pixel coordinates of the
   upper-left corner of the box.  Return in *BOTTOM_RIGHT_X, and
   *BOTTOM_RIGHT_Y the coordinates of the bottom-right corner of the
   box.  */
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INLINE void
window_box_edges (w, area, top_left_x, top_left_y,
		  bottom_right_x, bottom_right_y)
     struct window *w;
     int area;
     int *top_left_x, *top_left_y, *bottom_right_x, *bottom_right_y;
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{
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  window_box (w, area, top_left_x, top_left_y, bottom_right_x,
	      bottom_right_y);
  *bottom_right_x += *top_left_x;
  *bottom_right_y += *top_left_y;
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}

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/***********************************************************************
			      Utilities
 ***********************************************************************/

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/* Return the next character from STR which is MAXLEN bytes long.
   Return in *LEN the length of the character.  This is like
   STRING_CHAR_AND_LENGTH but never returns an invalid character.  If
   we find one, we return a `?', but with the length of the illegal
   character.  */

static INLINE int
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string_char_and_length (str, maxlen, len)
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     unsigned char *str;
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     int maxlen, *len;
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{
  int c;

  c = STRING_CHAR_AND_LENGTH (str, maxlen, *len);
  if (!CHAR_VALID_P (c, 1))
    /* We may not change the length here because other places in Emacs
       don't use this function, i.e. they silently accept illegal
       characters.  */
    c = '?';

  return c;
}



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/* Given a position POS containing a valid character and byte position
   in STRING, return the position NCHARS ahead (NCHARS >= 0).  */

static struct text_pos
string_pos_nchars_ahead (pos, string, nchars)
     struct text_pos pos;
     Lisp_Object string;
     int nchars;
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{
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  xassert (STRINGP (string) && nchars >= 0);

  if (STRING_MULTIBYTE (string))
    {
      int rest = STRING_BYTES (XSTRING (string)) - BYTEPOS (pos);
      unsigned char *p = XSTRING (string)->data + BYTEPOS (pos);
      int len;

      while (nchars--)
	{
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	  string_char_and_length (p, rest, &len);
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	  p += len, rest -= len;
	  xassert (rest >= 0);
	  CHARPOS (pos) += 1;
	  BYTEPOS (pos) += len;
	}
    }
  else
    SET_TEXT_POS (pos, CHARPOS (pos) + nchars, BYTEPOS (pos) + nchars);

  return pos;
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}


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/* Value is the text position, i.e. character and byte position,
   for character position CHARPOS in STRING.  */

static INLINE struct text_pos
string_pos (charpos, string)
     int charpos;
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     Lisp_Object string;
{
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  struct text_pos pos;
  xassert (STRINGP (string));
  xassert (charpos >= 0);
  SET_TEXT_POS (pos, charpos, string_char_to_byte (string, charpos));
  return pos;
}


/* Value is a text position, i.e. character and byte position, for
   character position CHARPOS in C string S.  MULTIBYTE_P non-zero
   means recognize multibyte characters.  */

static struct text_pos
c_string_pos (charpos, s, multibyte_p)
     int charpos;
     unsigned char *s;
     int multibyte_p;
{
  struct text_pos pos;

  xassert (s != NULL);
  xassert (charpos >= 0);

  if (multibyte_p)
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    {
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      int rest = strlen (s), len;

      SET_TEXT_POS (pos, 0, 0);
      while (charpos--)
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	{
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	  string_char_and_length (s, rest, &len);
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	  s += len, rest -= len;
	  xassert (rest >= 0);
	  CHARPOS (pos) += 1;
	  BYTEPOS (pos) += len;
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	}
    }
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  else
    SET_TEXT_POS (pos, charpos, charpos);
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  return pos;
}
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/* Value is the number of characters in C string S.  MULTIBYTE_P
   non-zero means recognize multibyte characters.  */
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static int
number_of_chars (s, multibyte_p)
     unsigned char *s;
     int multibyte_p;
{
  int nchars;
  
  if (multibyte_p)
    {
      int rest = strlen (s), len;
      unsigned char *p = (unsigned char *) s;
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      for (nchars = 0; rest > 0; ++nchars)
	{
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	  string_char_and_length (p, rest, &len);
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	  rest -= len, p += len;
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	}
    }
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  else
    nchars = strlen (s);

  return nchars;
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}

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/* Compute byte position NEWPOS->bytepos corresponding to
   NEWPOS->charpos.  POS is a known position in string STRING.
   NEWPOS->charpos must be >= POS.charpos.  */
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static void
compute_string_pos (newpos, pos, string)
     struct text_pos *newpos, pos;
     Lisp_Object string;
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{
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  xassert (STRINGP (string));
  xassert (CHARPOS (*newpos) >= CHARPOS (pos));
  
  if (STRING_MULTIBYTE (string))
    *newpos = string_pos_nchars_ahead (pos, CHARPOS (*newpos) - CHARPOS (pos),
				       string);
  else
    BYTEPOS (*newpos) = CHARPOS (*newpos);
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}

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/* Return the charset of the character at position POS in
   current_buffer.  */
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static int
charset_at_position (pos)
     struct text_pos pos;
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{
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  int c, multibyte_p;
  unsigned char *p = BYTE_POS_ADDR (BYTEPOS (pos));

  multibyte_p = !NILP (current_buffer->enable_multibyte_characters);
  if (multibyte_p)
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    {
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      int maxlen = ((BYTEPOS (pos) >= GPT_BYTE ? ZV_BYTE : GPT_BYTE)
		    - BYTEPOS (pos));
      int len;
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      c = string_char_and_length (p, maxlen, &len);
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    }
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  else
    c = *p;

  return CHAR_CHARSET (c);
}



/***********************************************************************
			Lisp form evaluation
 ***********************************************************************/

/* Error handler for eval_form.  */

static Lisp_Object
eval_handler (arg)
     Lisp_Object arg;
{
  return Qnil;
}


/* Evaluate SEXPR and return the result, or nil if something went
   wrong.  */

static Lisp_Object
eval_form (sexpr)
     Lisp_Object sexpr;
{
  int count = specpdl_ptr - specpdl;
  Lisp_Object val;
  specbind (Qinhibit_redisplay, Qt);
  val = internal_condition_case_1 (Feval, sexpr, Qerror, eval_handler);
  return unbind_to (count, val);
}



/***********************************************************************
			      Debugging
 ***********************************************************************/

#if 0

/* Define CHECK_IT to perform sanity checks on iterators.
   This is for debugging.  It is too slow to do unconditionally.  */

static void
check_it (it)
     struct it *it;
{
  if (it->method == next_element_from_string)
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    {
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      xassert (STRINGP (it->string));
      xassert (IT_STRING_CHARPOS (*it) >= 0);
    }
  else if (it->method == next_element_from_buffer)
    {
      /* Check that character and byte positions agree.  */
      xassert (IT_CHARPOS (*it) == BYTE_TO_CHAR (IT_BYTEPOS (*it)));
    }
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  if (it->dpvec)
    xassert (it->current.dpvec_index >= 0);
  else
    xassert (it->current.dpvec_index < 0);
}
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#define CHECK_IT(IT)	check_it ((IT))

#else /* not 0 */

#define CHECK_IT(IT)	(void) 0

#endif /* not 0 */


#if GLYPH_DEBUG

/* Check that the window end of window W is what we expect it
   to be---the last row in the current matrix displaying text.  */

static void
check_window_end (w)
     struct window *w;
{
  if (!MINI_WINDOW_P (w)
      && !NILP (w->window_end_valid))
    {
      struct glyph_row *row;
      xassert ((row = MATRIX_ROW (w->current_matrix,
				  XFASTINT (w->window_end_vpos)),
		!row->enabled_p
		|| MATRIX_ROW_DISPLAYS_TEXT_P (row)
		|| MATRIX_ROW_VPOS (row, w->current_matrix) == 0));
    }
}

#define CHECK_WINDOW_END(W)	check_window_end ((W))

#else /* not GLYPH_DEBUG */

#define CHECK_WINDOW_END(W)	(void) 0

#endif /* not GLYPH_DEBUG */



/***********************************************************************
		       Iterator initialization
 ***********************************************************************/

/* Initialize IT for displaying current_buffer in window W, starting
   at character position CHARPOS.  CHARPOS < 0 means that no buffer
   position is specified which is useful when the iterator is assigned
   a position later.  BYTEPOS is the byte position corresponding to
   CHARPOS.  BYTEPOS <= 0 means compute it from CHARPOS.

   If ROW is not null, calls to produce_glyphs with IT as parameter
   will produce glyphs in that row.

   BASE_FACE_ID is the id of a base face to use.  It must be one of
   DEFAULT_FACE_ID for normal text, MODE_LINE_FACE_ID or
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   HEADER_LINE_FACE_ID for displaying mode lines, or TOOL_BAR_FACE_ID for
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   displaying the tool-bar.
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   If ROW is null and BASE_FACE_ID is equal to MODE_LINE_FACE_ID or
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   HEADER_LINE_FACE_ID, the iterator will be initialized to use the
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   corresponding mode line glyph row of the desired matrix of W.  */

void
init_iterator (it, w, charpos, bytepos, row, base_face_id)
     struct it *it;
     struct window *w;
     int charpos, bytepos;
     struct glyph_row *row;
     enum face_id base_face_id;
{
  int highlight_region_p;

  /* Some precondition checks.  */
  xassert (w != NULL && it != NULL);
  xassert (charpos < 0 || (charpos > 0 && charpos <= ZV));

  /* If face attributes have been changed since the last redisplay,
     free realized faces now because they depend on face definitions
     that might have changed.  */
  if (face_change_count)
    {
      face_change_count = 0;
      free_all_realized_faces (Qnil);
    }

  /* Use one of the mode line rows of W's desired matrix if
     appropriate.  */
  if (row == NULL)
    {
      if (base_face_id == MODE_LINE_FACE_ID)
	row = MATRIX_MODE_LINE_ROW (w->desired_matrix);
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      else if (base_face_id == HEADER_LINE_FACE_ID)
	row = MATRIX_HEADER_LINE_ROW (w->desired_matrix);
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    }
  
  /* Clear IT.  */
  bzero (it, sizeof *it);
  it->current.overlay_string_index = -1;
  it->current.dpvec_index = -1;
  it->charset = CHARSET_ASCII;
  it->base_face_id = base_face_id;

  /* The window in which we iterate over current_buffer:  */
  XSETWINDOW (it->window, w);
  it->w = w;
  it->f = XFRAME (w->frame);

  /* If realized faces have been removed, e.g. because of face
     attribute changes of named faces, recompute them.  */
  if (FRAME_FACE_CACHE (it->f)->used == 0)
    recompute_basic_faces (it->f);

  /* Current value of the `space-width', and 'height' properties.  */
  it->space_width = Qnil;
  it->font_height = Qnil;
  
  /* Are control characters displayed as `^C'?  */
  it->ctl_arrow_p = !NILP (current_buffer->ctl_arrow);

  /* -1 means everything between a CR and the following line end
     is invisible.  >0 means lines indented more than this value are
     invisible.  */
  it->selective = (INTEGERP (current_buffer->selective_display)
		   ? XFASTINT (current_buffer->selective_display)
		   : (!NILP (current_buffer->selective_display) 
		      ? -1 : 0));
  it->selective_display_ellipsis_p
    = !NILP (current_buffer->selective_display_ellipses);

  /* Display table to use.  */
  it->dp = window_display_table (w);

  /* Are multibyte characters enabled in current_buffer?  */
  it->multibyte_p = !NILP (current_buffer->enable_multibyte_characters);

  /* Non-zero if we should highlight the region.  */
  highlight_region_p
    = (!NILP (Vtransient_mark_mode) 
       && !NILP (current_buffer->mark_active)
       && XMARKER (current_buffer->mark)->buffer != 0);

  /* Set IT->region_beg_charpos and IT->region_end_charpos to the
     start and end of a visible region in window IT->w.  Set both to
     -1 to indicate no region.  */
  if (highlight_region_p
      /* Maybe highlight only in selected window.  */
      && (/* Either show region everywhere.  */ 
	  highlight_nonselected_windows
	  /* Or show region in the selected window.  */
	  || w == XWINDOW (selected_window)
	  /* Or show the region if we are in the mini-buffer and W is
	     the window the mini-buffer refers to.  */
	  || (MINI_WINDOW_P (XWINDOW (selected_window))
	      && w == XWINDOW (Vminibuf_scroll_window))))
    {
      int charpos = marker_position (current_buffer->mark);
      it->region_beg_charpos = min (PT, charpos);
      it->region_end_charpos = max (PT, charpos);
    }
  else
    it->region_beg_charpos = it->region_end_charpos = -1;

  /* Get the position at which the redisplay_end_trigger hook should
     be run, if it is to be run at all.  */
  if (MARKERP (w->redisplay_end_trigger)
      && XMARKER (w->redisplay_end_trigger)->buffer != 0)
    it->redisplay_end_trigger_charpos
      = marker_position (w->redisplay_end_trigger);
  else if (INTEGERP (w->redisplay_end_trigger))
    it->redisplay_end_trigger_charpos = XINT (w->redisplay_end_trigger);

  /* Correct bogus values of tab_width.  */
  it->tab_width = XINT (current_buffer->tab_width);
  if (it->tab_width <= 0 || it->tab_width > 1000)
    it->tab_width = 8;

  /* Are lines in the display truncated?  */
  it->truncate_lines_p
    = (base_face_id != DEFAULT_FACE_ID
       || XINT (it->w->hscroll)
       || (truncate_partial_width_windows
	   && !WINDOW_FULL_WIDTH_P (it->w))
       || !NILP (current_buffer->truncate_lines));

  /* Get dimensions of truncation and continuation glyphs.  These are
     displayed as bitmaps under X, so we don't need them for such
     frames.  */
  if (!FRAME_WINDOW_P (it->f))
    {
      if (it->truncate_lines_p)
	{
	  /* We will need the truncation glyph.  */
	  xassert (it->glyph_row == NULL);
	  produce_special_glyphs (it, IT_TRUNCATION);
	  it->truncation_pixel_width = it->pixel_width;
	}
      else
	{
	  /* We will need the continuation glyph.  */
	  xassert (it->glyph_row == NULL);
	  produce_special_glyphs (it, IT_CONTINUATION);
	  it->continuation_pixel_width = it->pixel_width;
	}

      /* Reset these values to zero becaue the produce_special_glyphs
	 above has changed them.  */
      it->pixel_width = it->ascent = it->descent = 0;
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      it->phys_ascent = it->phys_descent = 0;
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    }

  /* Set this after getting the dimensions of truncation and
     continuation glyphs, so that we don't produce glyphs when calling
     produce_special_glyphs, above.  */
  it->glyph_row = row;
  it->area = TEXT_AREA;

  /* Get the dimensions of the display area.  The display area
     consists of the visible window area plus a horizontally scrolled
     part to the left of the window.  All x-values are relative to the
     start of this total display area.  */
  if (base_face_id != DEFAULT_FACE_ID)
    {
      /* Mode lines, menu bar in terminal frames.  */
      it->first_visible_x = 0;
      it->last_visible_x = XFASTINT (w->width) * CANON_X_UNIT (it->f);
    }
  else
    {
      it->first_visible_x
	= XFASTINT (it->w->hscroll) * CANON_X_UNIT (it->f);
      it->last_visible_x = (it->first_visible_x
			    + window_box_width (w, TEXT_AREA));

      /* If we truncate lines, leave room for the truncator glyph(s) at
	 the right margin.  Otherwise, leave room for the continuation
	 glyph(s).  Truncation and continuation glyphs are not inserted
	 for window-based redisplay.  */
      if (!FRAME_WINDOW_P (it->f))
	{
	  if (it->truncate_lines_p)
	    it->last_visible_x -= it->truncation_pixel_width;
	  else
	    it->last_visible_x -= it->continuation_pixel_width;
	}

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      it->header_line_p = WINDOW_WANTS_HEADER_LINE_P (w);
      it->current_y = WINDOW_DISPLAY_HEADER_LINE_HEIGHT (w) + w->vscroll;
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    }

  /* Leave room for a border glyph.  */
  if (!FRAME_WINDOW_P (it->f)
      && !WINDOW_RIGHTMOST_P (it->w))
    it->last_visible_x -= 1;

  it->last_visible_y = window_text_bottom_y (w);

  /* For mode lines and alike, arrange for the first glyph having a
     left box line if the face specifies a box.  */
  if (base_face_id != DEFAULT_FACE_ID)
    {
      struct face *face;
      
      it->face_id = base_face_id;

      /* If we have a boxed mode line, make the first character appear
	 with a left box line.  */
      face = FACE_FROM_ID (it->f, base_face_id);
      if (face->box != FACE_NO_BOX)
	it->start_of_box_run_p = 1;
    }

  /* If a buffer position was specified, set the iterator there,
     getting overlays and face properties from that position.  */
  if (charpos > 0)
    {
      it->end_charpos = ZV;
      it->face_id = -1;
      IT_CHARPOS (*it) = charpos;
      
      /* Compute byte position if not specified.  */
      if (bytepos <= 0)
	IT_BYTEPOS (*it) = CHAR_TO_BYTE (charpos);
      else
	IT_BYTEPOS (*it) = bytepos;

      /* Compute faces etc.  */
      reseat (it, it->current.pos, 1);
    }
  
  CHECK_IT (it);
}


/* Initialize IT for the display of window W with window start POS.  */

void
start_display (it, w, pos)
     struct it *it;
     struct window *w;
     struct text_pos pos;
{
  int start_at_line_beg_p;
  struct glyph_row *row;
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  int first_vpos = WINDOW_WANTS_HEADER_LINE_P (w) ? 1 : 0;
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