window.c

/* Window creation, deletion and examination for GNU Emacs.
   Does not include redisplay.
   Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1996, 1997, 1998, 2000,
                 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.

This file is part of GNU Emacs.

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

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

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

#include <config.h>
#include "lisp.h"
#include "buffer.h"
#include "keyboard.h"
#include "keymap.h"
#include "frame.h"
#include "window.h"
#include "commands.h"
#include "indent.h"
#include "termchar.h"
#include "disptab.h"
#include "dispextern.h"
#include "blockinput.h"
#include "intervals.h"

#ifdef HAVE_X_WINDOWS
#include "xterm.h"
#endif	/* HAVE_X_WINDOWS */
#ifdef WINDOWSNT
#include "w32term.h"
#endif
#ifdef MSDOS
#include "msdos.h"
#endif
#ifdef MAC_OS
#include "macterm.h"
#endif


Lisp_Object Qwindowp, Qwindow_live_p, Qwindow_configuration_p;
Lisp_Object Qscroll_up, Qscroll_down;
Lisp_Object Qwindow_size_fixed;
extern Lisp_Object Qleft_margin, Qright_margin;

static int displayed_window_lines P_ ((struct window *));
static struct window *decode_window P_ ((Lisp_Object));
static int count_windows P_ ((struct window *));
static int get_leaf_windows P_ ((struct window *, struct window **, int));
static void window_scroll P_ ((Lisp_Object, int, int, int));
static void window_scroll_pixel_based P_ ((Lisp_Object, int, int, int));
static void window_scroll_line_based P_ ((Lisp_Object, int, int, int));
static int window_min_size_1 P_ ((struct window *, int));
static int window_min_size P_ ((struct window *, int, int, int *));
static void size_window P_ ((Lisp_Object, int, int, int));
static int freeze_window_start P_ ((struct window *, void *));
static int window_fixed_size_p P_ ((struct window *, int, int));
static void enlarge_window P_ ((Lisp_Object, int, int));
static Lisp_Object window_list P_ ((void));
static int add_window_to_list P_ ((struct window *, void *));
static int candidate_window_p P_ ((Lisp_Object, Lisp_Object, Lisp_Object,
				   Lisp_Object));
static Lisp_Object next_window P_ ((Lisp_Object, Lisp_Object,
				    Lisp_Object, int));
static void decode_next_window_args P_ ((Lisp_Object *, Lisp_Object *,
					 Lisp_Object *));
static int foreach_window_1 P_ ((struct window *,
				 int (* fn) (struct window *, void *),
				 void *));
static Lisp_Object window_list_1 P_ ((Lisp_Object, Lisp_Object, Lisp_Object));

/* This is the window in which the terminal's cursor should
   be left when nothing is being done with it.  This must
   always be a leaf window, and its buffer is selected by
   the top level editing loop at the end of each command.

   This value is always the same as
   FRAME_SELECTED_WINDOW (selected_frame).  */

Lisp_Object selected_window;

/* A list of all windows for use by next_window and Fwindow_list.
   Functions creating or deleting windows should invalidate this cache
   by setting it to nil.  */

Lisp_Object Vwindow_list;

/* The mini-buffer window of the selected frame.
   Note that you cannot test for mini-bufferness of an arbitrary window
   by comparing against this; but you can test for mini-bufferness of
   the selected window.  */

Lisp_Object minibuf_window;

/* Non-nil means it is the window whose mode line should be
   shown as the selected window when the minibuffer is selected.  */

Lisp_Object minibuf_selected_window;

/* Non-nil means it is the window for C-M-v to scroll
   when the mini-buffer is selected.  */

Lisp_Object Vminibuf_scroll_window;

/* Non-nil means this is the buffer whose window C-M-v should scroll.  */

Lisp_Object Vother_window_scroll_buffer;

/* Non-nil means it's function to call to display temp buffers.  */

Lisp_Object Vtemp_buffer_show_function;

/* Non-zero means line and page scrolling on tall lines (with images)
   does partial scrolling by modifying window-vscroll.  */

int auto_window_vscroll_p;

/* Non-zero means to use mode-line-inactive face in all windows but the
   selected-window and the minibuffer-scroll-window when the
   minibuffer is active.  */
int mode_line_in_non_selected_windows;

/* If a window gets smaller than either of these, it is removed. */

EMACS_INT window_min_height;
EMACS_INT window_min_width;

/* Nonzero implies Fdisplay_buffer should create windows. */

int pop_up_windows;

/* Nonzero implies make new frames for Fdisplay_buffer.  */

int pop_up_frames;

/* Nonzero means reuse existing frames for displaying buffers.  */

int display_buffer_reuse_frames;

/* Non-nil means use this function instead of default */

Lisp_Object Vpop_up_frame_function;

/* Function to call to handle Fdisplay_buffer.  */

Lisp_Object Vdisplay_buffer_function;

/* Non-nil means that Fdisplay_buffer should even the heights of windows.  */

Lisp_Object Veven_window_heights;

/* List of buffer *names* for buffers that should have their own frames.  */

Lisp_Object Vspecial_display_buffer_names;

/* List of regexps for buffer names that should have their own frames.  */

Lisp_Object Vspecial_display_regexps;

/* Function to pop up a special frame.  */

Lisp_Object Vspecial_display_function;

/* List of buffer *names* for buffers to appear in selected window.  */

Lisp_Object Vsame_window_buffer_names;

/* List of regexps for buffer names to appear in selected window.  */

Lisp_Object Vsame_window_regexps;

/* Hook run at end of temp_output_buffer_show.  */

Lisp_Object Qtemp_buffer_show_hook;

/* Fdisplay_buffer always splits the largest window
   if that window is more than this high.  */

EMACS_INT split_height_threshold;

/* Number of lines of continuity in scrolling by screenfuls.  */

EMACS_INT next_screen_context_lines;

/* Incremented for each window created.  */

static int sequence_number;

/* Nonzero after init_window_once has finished.  */

static int window_initialized;

/* Hook to run when window config changes.  */

Lisp_Object Qwindow_configuration_change_hook;
Lisp_Object Vwindow_configuration_change_hook;

/* Non-nil means scroll commands try to put point
   at the same screen height as previously.  */

Lisp_Object Vscroll_preserve_screen_position;

/* Incremented by 1 whenever a window is deleted.  */

int window_deletion_count;

/* Used by the function window_scroll_pixel_based */

static int window_scroll_pixel_based_preserve_y;

#if 0 /* This isn't used anywhere.  */
/* Nonzero means we can split a frame even if it is "unsplittable".  */
static int inhibit_frame_unsplittable;
#endif /* 0 */

extern EMACS_INT scroll_margin;

extern Lisp_Object Qwindow_scroll_functions, Vwindow_scroll_functions;

DEFUN ("windowp", Fwindowp, Swindowp, 1, 1, 0,
       doc: /* Returns t if OBJECT is a window.  */)
     (object)
     Lisp_Object object;
{
  return WINDOWP (object) ? Qt : Qnil;
}

DEFUN ("window-live-p", Fwindow_live_p, Swindow_live_p, 1, 1, 0,
       doc: /* Returns t if OBJECT is a window which is currently visible.  */)
     (object)
     Lisp_Object object;
{
  return WINDOW_LIVE_P (object) ? Qt : Qnil;
}

Lisp_Object
make_window ()
{
  Lisp_Object val;
  register struct window *p;

  p = allocate_window ();
  ++sequence_number;
  XSETFASTINT (p->sequence_number, sequence_number);
  XSETFASTINT (p->left_col, 0);
  XSETFASTINT (p->top_line, 0);
  XSETFASTINT (p->total_lines, 0);
  XSETFASTINT (p->total_cols, 0);
  XSETFASTINT (p->hscroll, 0);
  XSETFASTINT (p->min_hscroll, 0);
  p->orig_top_line = p->orig_total_lines = Qnil;
  p->start = Fmake_marker ();
  p->pointm = Fmake_marker ();
  XSETFASTINT (p->use_time, 0);
  p->frame = Qnil;
  p->display_table = Qnil;
  p->dedicated = Qnil;
  p->pseudo_window_p = 0;
  bzero (&p->cursor, sizeof (p->cursor));
  bzero (&p->last_cursor, sizeof (p->last_cursor));
  bzero (&p->phys_cursor, sizeof (p->phys_cursor));
  p->desired_matrix = p->current_matrix = 0;
  p->nrows_scale_factor = p->ncols_scale_factor = 1;
  p->phys_cursor_type = -1;
  p->phys_cursor_width = -1;
  p->must_be_updated_p = 0;
  XSETFASTINT (p->window_end_vpos, 0);
  XSETFASTINT (p->window_end_pos, 0);
  p->window_end_valid = Qnil;
  p->vscroll = 0;
  XSETWINDOW (val, p);
  XSETFASTINT (p->last_point, 0);
  p->frozen_window_start_p = 0;
  p->last_cursor_off_p = p->cursor_off_p = 0;
  p->left_margin_cols = Qnil;
  p->right_margin_cols = Qnil;
  p->left_fringe_width = Qnil;
  p->right_fringe_width = Qnil;
  p->fringes_outside_margins = Qnil;
  p->scroll_bar_width = Qnil;
  p->vertical_scroll_bar_type = Qt;

  Vwindow_list = Qnil;
  return val;
}

DEFUN ("selected-window", Fselected_window, Sselected_window, 0, 0, 0,
       doc: /* Return the window that the cursor now appears in and commands apply to.  */)
     ()
{
  return selected_window;
}

DEFUN ("minibuffer-window", Fminibuffer_window, Sminibuffer_window, 0, 1, 0,
       doc: /* Return the window used now for minibuffers.
If the optional argument FRAME is specified, return the minibuffer window
used by that frame.  */)
     (frame)
    Lisp_Object frame;
{
  if (NILP (frame))
    frame = selected_frame;
  CHECK_LIVE_FRAME (frame);
  return FRAME_MINIBUF_WINDOW (XFRAME (frame));
}

DEFUN ("window-minibuffer-p", Fwindow_minibuffer_p, Swindow_minibuffer_p, 0, 1, 0,
       doc: /* Returns non-nil if WINDOW is a minibuffer window.
WINDOW defaults to the selected window.  */)
     (window)
     Lisp_Object window;
{
  struct window *w = decode_window (window);
  return MINI_WINDOW_P (w) ? Qt : Qnil;
}


DEFUN ("pos-visible-in-window-p", Fpos_visible_in_window_p,
       Spos_visible_in_window_p, 0, 3, 0,
       doc: /* Return non-nil if position POS is currently on the frame in WINDOW.
Return nil if that position is scrolled vertically out of view.
If a character is only partially visible, nil is returned, unless the
optional argument PARTIALLY is non-nil.
If POS is only out of view because of horizontal scrolling, return non-nil.
POS defaults to point in WINDOW; WINDOW defaults to the selected window.

If POS is visible, return t if PARTIALLY is nil; if PARTIALLY is non-nil,
return value is a list (X Y PARTIAL) where X and Y are the pixel coordinates
relative to the top left corner of the window. PARTIAL is nil if the character
after POS is fully visible; otherwise it is a cons (RTOP . RBOT) where RTOP
and RBOT are the number of pixels invisible at the top and bottom of the row.  */)
     (pos, window, partially)
     Lisp_Object pos, window, partially;
{
  register struct window *w;
  register int posint;
  register struct buffer *buf;
  struct text_pos top;
  Lisp_Object in_window = Qnil;
  int rtop, rbot, fully_p = 1;
  int x, y;

  w = decode_window (window);
  buf = XBUFFER (w->buffer);
  SET_TEXT_POS_FROM_MARKER (top, w->start);

  if (!NILP (pos))
    {
      CHECK_NUMBER_COERCE_MARKER (pos);
      posint = XINT (pos);
    }
  else if (w == XWINDOW (selected_window))
    posint = PT;
  else
    posint = XMARKER (w->pointm)->charpos;

  /* If position is above window start or outside buffer boundaries,
     or if window start is out of range, position is not visible.  */
  if (posint >= CHARPOS (top)
      && posint <= BUF_ZV (buf)
      && CHARPOS (top) >= BUF_BEGV (buf)
      && CHARPOS (top) <= BUF_ZV (buf)
      && pos_visible_p (w, posint, &x, &y, &rtop, &rbot, NILP (partially))
      && (fully_p = !rtop && !rbot, (!NILP (partially) || fully_p)))
    in_window = Qt;

  if (!NILP (in_window) && !NILP (partially))
    in_window = Fcons (make_number (x),
		       Fcons (make_number (y),
			      Fcons ((fully_p ? Qnil
				     : Fcons (make_number (rtop),
					      make_number (rbot))),
				     Qnil)));
  return in_window;
}


static struct window *
decode_window (window)
     register Lisp_Object window;
{
  if (NILP (window))
    return XWINDOW (selected_window);

  CHECK_LIVE_WINDOW (window);
  return XWINDOW (window);
}

static struct window *
decode_any_window (window)
     register Lisp_Object window;
{
  if (NILP (window))
    return XWINDOW (selected_window);

  CHECK_WINDOW (window);
  return XWINDOW (window);
}

DEFUN ("window-buffer", Fwindow_buffer, Swindow_buffer, 0, 1, 0,
       doc: /* Return the buffer that WINDOW is displaying.
WINDOW defaults to the selected window.  */)
     (window)
     Lisp_Object window;
{
  return decode_window (window)->buffer;
}

DEFUN ("window-height", Fwindow_height, Swindow_height, 0, 1, 0,
       doc: /* Return the number of lines in WINDOW (including its mode line).  */)
     (window)
     Lisp_Object window;
{
  return decode_any_window (window)->total_lines;
}

DEFUN ("window-width", Fwindow_width, Swindow_width, 0, 1, 0,
       doc: /* Return the number of display columns in WINDOW.
This is the width that is usable columns available for text in WINDOW.
If you want to find out how many columns WINDOW takes up,
use  (let ((edges (window-edges))) (- (nth 2 edges) (nth 0 edges))).  */)
     (window)
     Lisp_Object window;
{
  return make_number (window_box_text_cols (decode_any_window (window)));
}

DEFUN ("window-hscroll", Fwindow_hscroll, Swindow_hscroll, 0, 1, 0,
       doc: /* Return the number of columns by which WINDOW is scrolled from left margin.  */)
     (window)
     Lisp_Object window;
{
  return decode_window (window)->hscroll;
}

DEFUN ("set-window-hscroll", Fset_window_hscroll, Sset_window_hscroll, 2, 2, 0,
       doc: /* Set number of columns WINDOW is scrolled from left margin to NCOL.
Return NCOL.  NCOL should be zero or positive.

Note that if `automatic-hscrolling' is non-nil, you cannot scroll the
window so that the location of point becomes invisible.  */)
     (window, ncol)
     Lisp_Object window, ncol;
{
  struct window *w = decode_window (window);
  int hscroll;

  CHECK_NUMBER (ncol);
  hscroll = max (0, XINT (ncol));

  /* Prevent redisplay shortcuts when changing the hscroll.  */
  if (XINT (w->hscroll) != hscroll)
    XBUFFER (w->buffer)->prevent_redisplay_optimizations_p = 1;

  w->hscroll = make_number (hscroll);
  return ncol;
}

DEFUN ("window-redisplay-end-trigger", Fwindow_redisplay_end_trigger,
       Swindow_redisplay_end_trigger, 0, 1, 0,
       doc: /* Return WINDOW's redisplay end trigger value.
See `set-window-redisplay-end-trigger' for more information.  */)
     (window)
     Lisp_Object window;
{
  return decode_window (window)->redisplay_end_trigger;
}

DEFUN ("set-window-redisplay-end-trigger", Fset_window_redisplay_end_trigger,
       Sset_window_redisplay_end_trigger, 2, 2, 0,
       doc: /* Set WINDOW's redisplay end trigger value to VALUE.
VALUE should be a buffer position (typically a marker) or nil.
If it is a buffer position, then if redisplay in WINDOW reaches a position
beyond VALUE, the functions in `redisplay-end-trigger-functions' are called
with two arguments: WINDOW, and the end trigger value.
Afterwards the end-trigger value is reset to nil.  */)
     (window, value)
     register Lisp_Object window, value;
{
  register struct window *w;

  w = decode_window (window);
  w->redisplay_end_trigger = value;
  return value;
}

DEFUN ("window-edges", Fwindow_edges, Swindow_edges, 0, 1, 0,
       doc: /* Return a list of the edge coordinates of WINDOW.
\(LEFT TOP RIGHT BOTTOM), all relative to 0, 0 at top left corner of frame.
RIGHT is one more than the rightmost column occupied by WINDOW,
and BOTTOM is one more than the bottommost row occupied by WINDOW.
The edges include the space used by the window's scroll bar,
display margins, fringes, header line, and mode line, if it has them.
To get the edges of the actual text area, use `window-inside-edges'.  */)
     (window)
     Lisp_Object window;
{
  register struct window *w = decode_any_window (window);

  return Fcons (make_number (WINDOW_LEFT_EDGE_COL (w)),
	 Fcons (make_number (WINDOW_TOP_EDGE_LINE (w)),
	 Fcons (make_number (WINDOW_RIGHT_EDGE_COL (w)),
	 Fcons (make_number (WINDOW_BOTTOM_EDGE_LINE (w)),
		Qnil))));
}

DEFUN ("window-pixel-edges", Fwindow_pixel_edges, Swindow_pixel_edges, 0, 1, 0,
       doc: /* Return a list of the edge pixel coordinates of WINDOW.
\(LEFT TOP RIGHT BOTTOM), all relative to 0, 0 at top left corner of frame.
RIGHT is one more than the rightmost x position occupied by WINDOW,
and BOTTOM is one more than the bottommost y position occupied by WINDOW.
The pixel edges include the space used by the window's scroll bar,
display margins, fringes, header line, and mode line, if it has them.
To get the edges of the actual text area, use `window-inside-pixel-edges'.  */)
     (window)
     Lisp_Object window;
{
  register struct window *w = decode_any_window (window);

  return Fcons (make_number (WINDOW_LEFT_EDGE_X (w)),
	 Fcons (make_number (WINDOW_TOP_EDGE_Y (w)),
	 Fcons (make_number (WINDOW_RIGHT_EDGE_X (w)),
	 Fcons (make_number (WINDOW_BOTTOM_EDGE_Y (w)),
		Qnil))));
}

DEFUN ("window-inside-edges", Fwindow_inside_edges, Swindow_inside_edges, 0, 1, 0,
       doc: /* Return a list of the edge coordinates of WINDOW.
\(LEFT TOP RIGHT BOTTOM), all relative to 0, 0 at top left corner of frame.
RIGHT is one more than the rightmost column used by text in WINDOW,
and BOTTOM is one more than the bottommost row used by text in WINDOW.
The inside edges do not include the space used by the window's scroll bar,
display margins, fringes, header line, and/or mode line.  */)
     (window)
     Lisp_Object window;
{
  register struct window *w = decode_any_window (window);

  return list4 (make_number (WINDOW_BOX_LEFT_EDGE_COL (w)
			     + WINDOW_LEFT_MARGIN_COLS (w)
			     + WINDOW_LEFT_FRINGE_COLS (w)),
		make_number (WINDOW_TOP_EDGE_LINE (w)
			     + WINDOW_HEADER_LINE_LINES (w)),
		make_number (WINDOW_BOX_RIGHT_EDGE_COL (w)
			     - WINDOW_RIGHT_MARGIN_COLS (w)
			     - WINDOW_RIGHT_FRINGE_COLS (w)),
		make_number (WINDOW_BOTTOM_EDGE_LINE (w)
			     - WINDOW_MODE_LINE_LINES (w)));
}

DEFUN ("window-inside-pixel-edges", Fwindow_inside_pixel_edges, Swindow_inside_pixel_edges, 0, 1, 0,
       doc: /* Return a list of the edge pixel coordinates of WINDOW.
\(LEFT TOP RIGHT BOTTOM), all relative to 0, 0 at top left corner of frame.
RIGHT is one more than the rightmost x position used by text in WINDOW,
and BOTTOM is one more than the bottommost y position used by text in WINDOW.
The inside edges do not include the space used by the window's scroll bar,
display margins, fringes, header line, and/or mode line.  */)
     (window)
     Lisp_Object window;
{
  register struct window *w = decode_any_window (window);

  return list4 (make_number (WINDOW_BOX_LEFT_EDGE_X (w)
			     + WINDOW_LEFT_MARGIN_WIDTH (w)
			     + WINDOW_LEFT_FRINGE_WIDTH (w)),
		make_number (WINDOW_TOP_EDGE_Y (w)
			     + WINDOW_HEADER_LINE_HEIGHT (w)),
		make_number (WINDOW_BOX_RIGHT_EDGE_X (w)
			     - WINDOW_RIGHT_MARGIN_WIDTH (w)
			     - WINDOW_RIGHT_FRINGE_WIDTH (w)),
		make_number (WINDOW_BOTTOM_EDGE_Y (w)
			     - WINDOW_MODE_LINE_HEIGHT (w)));
}

/* Test if the character at column *X, row *Y is within window W.
   If it is not, return ON_NOTHING;
   if it is in the window's text area,
      set *x and *y to its location relative to the upper left corner
         of the window, and
      return ON_TEXT;
   if it is on the window's modeline, return ON_MODE_LINE;
   if it is on the border between the window and its right sibling,
      return ON_VERTICAL_BORDER.
   if it is on a scroll bar,
      return ON_SCROLL_BAR.
   if it is on the window's top line, return ON_HEADER_LINE;
   if it is in left or right fringe of the window,
      return ON_LEFT_FRINGE or ON_RIGHT_FRINGE, and convert *X and *Y
      to window-relative coordinates;
   if it is in the marginal area to the left/right of the window,
      return ON_LEFT_MARGIN or ON_RIGHT_MARGIN, and convert *X and *Y
      to window-relative coordinates.

   X and Y are frame relative pixel coordinates.  */

static enum window_part
coordinates_in_window (w, x, y)
     register struct window *w;
     register int *x, *y;
{
  struct frame *f = XFRAME (WINDOW_FRAME (w));
  int left_x, right_x, top_y, bottom_y;
  enum window_part part;
  int ux = FRAME_COLUMN_WIDTH (f);
  int x0 = WINDOW_LEFT_EDGE_X (w);
  int x1 = WINDOW_RIGHT_EDGE_X (w);
  /* The width of the area where the vertical line can be dragged.
     (Between mode lines for instance.  */
  int grabbable_width = ux;
  int lmargin_width, rmargin_width, text_left, text_right;

  /* In what's below, we subtract 1 when computing right_x because we
     want the rightmost pixel, which is given by left_pixel+width-1.  */
  if (w->pseudo_window_p)
    {
      left_x = 0;
      right_x = WINDOW_TOTAL_WIDTH (w) - 1;
      top_y = WINDOW_TOP_EDGE_Y (w);
      bottom_y = WINDOW_BOTTOM_EDGE_Y (w);
    }
  else
    {
      left_x = WINDOW_BOX_LEFT_EDGE_X (w);
      right_x = WINDOW_BOX_RIGHT_EDGE_X (w) - 1;
      top_y = WINDOW_TOP_EDGE_Y (w);
      bottom_y = WINDOW_BOTTOM_EDGE_Y (w);
    }

  /* Outside any interesting row?  */
  if (*y < top_y || *y >= bottom_y)
    return ON_NOTHING;

  /* On the mode line or header line?  If it's near the start of
     the mode or header line of window that's has a horizontal
     sibling, say it's on the vertical line.  That's to be able
     to resize windows horizontally in case we're using toolkit
     scroll bars.  */

  if (WINDOW_WANTS_MODELINE_P (w)
      && *y >= bottom_y - CURRENT_MODE_LINE_HEIGHT (w))
    {
      part = ON_MODE_LINE;

    header_vertical_border_check:
      /* We're somewhere on the mode line.  We consider the place
	 between mode lines of horizontally adjacent mode lines
	 as the vertical border.    If scroll bars on the left,
	 return the right window.  */
      if (WINDOW_HAS_VERTICAL_SCROLL_BAR_ON_LEFT (w)
	  || WINDOW_RIGHTMOST_P (w))
	{
	  if (!WINDOW_LEFTMOST_P (w) && abs (*x - x0) < grabbable_width)
	    {
	      *x = max (0, *x - x0);
	      *y -= top_y;
	      return ON_VERTICAL_BORDER;
	    }
	}
      else
	{
	  if (abs (*x - x1) < grabbable_width)
	    {
	      *x = min (x1, *x) - x0;
	      *y -= top_y;
	      return ON_VERTICAL_BORDER;
	    }
	}

      if (*x < x0 || *x >= x1)
	return ON_NOTHING;

      /* Convert X and Y to window relative coordinates.
	 Mode line starts at left edge of window.  */
      *x -= x0;
      *y -= top_y;
      return part;
    }

  if (WINDOW_WANTS_HEADER_LINE_P (w)
      && *y < top_y + CURRENT_HEADER_LINE_HEIGHT (w))
    {
      part = ON_HEADER_LINE;
      goto header_vertical_border_check;
    }

  if (*x < x0 || *x >= x1)
    return ON_NOTHING;

  /* Outside any interesting column?  */
  if (*x < left_x || *x > right_x)
    {
      *y -= top_y;
      return ON_SCROLL_BAR;
    }

  lmargin_width = window_box_width (w, LEFT_MARGIN_AREA);
  rmargin_width = window_box_width (w, RIGHT_MARGIN_AREA);

  text_left = window_box_left (w, TEXT_AREA);
  text_right = text_left + window_box_width (w, TEXT_AREA);

  if (FRAME_WINDOW_P (f))
    {
      if (!w->pseudo_window_p
	  && !WINDOW_HAS_VERTICAL_SCROLL_BAR (w)
	  && !WINDOW_RIGHTMOST_P (w)
	  && (abs (*x - right_x) < grabbable_width))
	{
	  *x = min (right_x, *x) - left_x;
	  *y -= top_y;
	  return ON_VERTICAL_BORDER;
	}
    }
  else
    {
      /* Need to say "*x > right_x" rather than >=, since on character
	 terminals, the vertical line's x coordinate is right_x.  */
      if (!w->pseudo_window_p
	  && !WINDOW_RIGHTMOST_P (w)
	  && *x > right_x - ux)
	{
	  /* On the border on the right side of the window?  Assume that
	     this area begins at RIGHT_X minus a canonical char width.  */
	  *x = min (right_x, *x) - left_x;
	  *y -= top_y;
	  return ON_VERTICAL_BORDER;
	}
    }

  if (*x < text_left)
    {
      if (lmargin_width > 0
	  && (WINDOW_HAS_FRINGES_OUTSIDE_MARGINS (w)
	      ? (*x >= left_x + WINDOW_LEFT_FRINGE_WIDTH (w))
	      : (*x < left_x + lmargin_width)))
	{
	  *x -= left_x;
	  if (WINDOW_HAS_FRINGES_OUTSIDE_MARGINS (w))
	    *x -= WINDOW_LEFT_FRINGE_WIDTH (w);
	  *y -= top_y;
	  return ON_LEFT_MARGIN;
	}

      /* Convert X and Y to window-relative pixel coordinates.  */
      *x -= left_x;
      *y -= top_y;
      return ON_LEFT_FRINGE;
    }

  if (*x >= text_right)
    {
      if (rmargin_width > 0
	  && (WINDOW_HAS_FRINGES_OUTSIDE_MARGINS (w)
	      ? (*x < right_x - WINDOW_RIGHT_FRINGE_WIDTH (w))
	      : (*x >= right_x - rmargin_width)))
	{
	  *x -= right_x - rmargin_width;
	  if (WINDOW_HAS_FRINGES_OUTSIDE_MARGINS (w))
	    *x += WINDOW_RIGHT_FRINGE_WIDTH (w);
	  *y -= top_y;
	  return ON_RIGHT_MARGIN;
	}

      /* Convert X and Y to window-relative pixel coordinates.  */
      *x -= left_x + WINDOW_LEFT_FRINGE_WIDTH (w);
      *y -= top_y;
      return ON_RIGHT_FRINGE;
    }

  /* Everything special ruled out - must be on text area */
  *x -= text_left;
  *y -= top_y;
  return ON_TEXT;
}


DEFUN ("coordinates-in-window-p", Fcoordinates_in_window_p,
       Scoordinates_in_window_p, 2, 2, 0,
       doc: /* Return non-nil if COORDINATES are in WINDOW.
COORDINATES is a cons of the form (X . Y), X and Y being distances
measured in characters from the upper-left corner of the frame.
\(0 .  0) denotes the character in the upper left corner of the
frame.
If COORDINATES are in the text portion of WINDOW,
   the coordinates relative to the window are returned.
If they are in the mode line of WINDOW, `mode-line' is returned.
If they are in the top mode line of WINDOW, `header-line' is returned.
If they are in the left fringe of WINDOW, `left-fringe' is returned.
If they are in the right fringe of WINDOW, `right-fringe' is returned.
If they are on the border between WINDOW and its right sibling,
  `vertical-line' is returned.
If they are in the windows's left or right marginal areas, `left-margin'\n\
  or `right-margin' is returned.  */)
     (coordinates, window)
     register Lisp_Object coordinates, window;
{
  struct window *w;
  struct frame *f;
  int x, y;
  Lisp_Object lx, ly;

  CHECK_WINDOW (window);
  w = XWINDOW (window);
  f = XFRAME (w->frame);
  CHECK_CONS (coordinates);
  lx = Fcar (coordinates);
  ly = Fcdr (coordinates);
  CHECK_NUMBER_OR_FLOAT (lx);
  CHECK_NUMBER_OR_FLOAT (ly);
  x = FRAME_PIXEL_X_FROM_CANON_X (f, lx) + FRAME_INTERNAL_BORDER_WIDTH (f);
  y = FRAME_PIXEL_Y_FROM_CANON_Y (f, ly) + FRAME_INTERNAL_BORDER_WIDTH (f);

  switch (coordinates_in_window (w, &x, &y))
    {
    case ON_NOTHING:
      return Qnil;

    case ON_TEXT:
      /* X and Y are now window relative pixel coordinates.  Convert
	 them to canonical char units before returning them.  */
      return Fcons (FRAME_CANON_X_FROM_PIXEL_X (f, x),
		    FRAME_CANON_Y_FROM_PIXEL_Y (f, y));

    case ON_MODE_LINE:
      return Qmode_line;

    case ON_VERTICAL_BORDER:
      return Qvertical_line;

    case ON_HEADER_LINE:
      return Qheader_line;

    case ON_LEFT_FRINGE:
      return Qleft_fringe;

    case ON_RIGHT_FRINGE:
      return Qright_fringe;

    case ON_LEFT_MARGIN:
      return Qleft_margin;

    case ON_RIGHT_MARGIN:
      return Qright_margin;

    case ON_SCROLL_BAR:
      /* Historically we are supposed to return nil in this case.  */
      return Qnil;

    default:
      abort ();
    }
}


/* Callback for foreach_window, used in window_from_coordinates.
   Check if window W contains coordinates specified by USER_DATA which
   is actually a pointer to a struct check_window_data CW.

   Check if window W contains coordinates *CW->x and *CW->y.  If it
   does, return W in *CW->window, as Lisp_Object, and return in
   *CW->part the part of the window under coordinates *X,*Y.  Return
   zero from this function to stop iterating over windows.  */

struct check_window_data
{
  Lisp_Object *window;
  int *x, *y;
  enum window_part *part;
};

static int
check_window_containing (w, user_data)
     struct window *w;
     void *user_data;
{
  struct check_window_data *cw = (struct check_window_data *) user_data;
  enum window_part found;
  int continue_p = 1;

  found = coordinates_in_window (w, cw->x, cw->y);
  if (found != ON_NOTHING)
    {
      *cw->part = found;
      XSETWINDOW (*cw->window, w);
      continue_p = 0;
    }

  return continue_p;
}


/* Find the window containing frame-relative pixel position X/Y and
   return it as a Lisp_Object.

   If X, Y is on one of the window's special `window_part' elements,
   set *PART to the id of that element, and return X and Y converted
   to window relative coordinates in WX and WY.

   If there is no window under X, Y return nil and leave *PART
   unmodified.  TOOL_BAR_P non-zero means detect tool-bar windows.

   This function was previously implemented with a loop cycling over
   windows with Fnext_window, and starting with the frame's selected
   window.  It turned out that this doesn't work with an
   implementation of next_window using Vwindow_list, because
   FRAME_SELECTED_WINDOW (F) is not always contained in the window
   tree of F when this function is called asynchronously from
   note_mouse_highlight.  The original loop didn't terminate in this
   case.  */

Lisp_Object
window_from_coordinates (f, x, y, part, wx, wy, tool_bar_p)
     struct frame *f;
     int x, y;
     enum window_part *part;
     int *wx, *wy;
     int tool_bar_p;
{
  Lisp_Object window;
  struct check_window_data cw;
  enum window_part dummy;

  if (part == 0)
    part = &dummy;

  window = Qnil;
  cw.window = &window, cw.x = &x, cw.y = &y; cw.part = part;
  foreach_window (f, check_window_containing, &cw);

  /* If not found above, see if it's in the tool bar window, if a tool
     bar exists.  */
  if (NILP (window)
      && tool_bar_p
      && WINDOWP (f->tool_bar_window)
      && WINDOW_TOTAL_LINES (XWINDOW (f->tool_bar_window)) > 0
      && (coordinates_in_window (XWINDOW (f->tool_bar_window), &x, &y)
	  != ON_NOTHING))
    {
      *part = ON_TEXT;
      window = f->tool_bar_window;
    }

  if (wx) *wx = x;
  if (wy) *wy = y;

  return window;
}

DEFUN ("window-at", Fwindow_at, Swindow_at, 2, 3, 0,
       doc: /* Return window containing coordinates X and Y on FRAME.
If omitted, FRAME defaults to the currently selected frame.
The top left corner of the frame is considered to be row 0,
column 0.  */)
     (x, y, frame)
     Lisp_Object x, y, frame;
{
  struct frame *f;

  if (NILP (frame))
    frame = selected_frame;
  CHECK_LIVE_FRAME (frame);
  f = XFRAME (frame);

  /* Check that arguments are integers or floats.  */
  CHECK_NUMBER_OR_FLOAT (x);
  CHECK_NUMBER_OR_FLOAT (y);

  return window_from_coordinates (f,
				  (FRAME_PIXEL_X_FROM_CANON_X (f, x)
				   + FRAME_INTERNAL_BORDER_WIDTH (f)),
				  (FRAME_PIXEL_Y_FROM_CANON_Y (f, y)
				   + FRAME_INTERNAL_BORDER_WIDTH (f)),
				  0, 0, 0, 0);
}

DEFUN ("window-point", Fwindow_point, Swindow_point, 0, 1, 0,