xterm.c

/* X Communication module for terminals which understand the X protocol.

Copyright (C) 1989, 1993-2013 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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.  */

/* New display code by Gerd Moellmann <gerd@gnu.org>.  */
/* Xt features made by Fred Pierresteguy.  */

#include <config.h>
#include <stdio.h>

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

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

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

#include <sys/ioctl.h>

#include "systime.h"

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

#include "charset.h"
#include "character.h"
#include "coding.h"
#include "frame.h"
#include "dispextern.h"
#include "fontset.h"
#include "termhooks.h"
#include "termopts.h"
#include "termchar.h"
#include "emacs-icon.h"
#include "disptab.h"
#include "buffer.h"
#include "window.h"
#include "keyboard.h"
#include "intervals.h"
#include "process.h"
#include "atimer.h"
#include "keymap.h"
#include "font.h"
#include "xsettings.h"
#include "xgselect.h"
#include "sysselect.h"

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

#include <unistd.h>

#ifdef USE_GTK
#include "gtkutil.h"
#ifdef HAVE_GTK3
#include <X11/Xproto.h>
#endif
#endif

#if defined (USE_LUCID) || defined (USE_MOTIF)
#include "../lwlib/xlwmenu.h"
#endif

#ifdef USE_X_TOOLKIT
#if !defined (NO_EDITRES)
#define HACK_EDITRES
extern void _XEditResCheckMessages (Widget, XtPointer, XEvent *, Boolean *);
#endif /* not NO_EDITRES */

/* Include toolkit specific headers for the scroll bar widget.  */

#ifdef USE_TOOLKIT_SCROLL_BARS
#if defined USE_MOTIF
#include <Xm/Xm.h>		/* For LESSTIF_VERSION */
#include <Xm/ScrollBar.h>
#else /* !USE_MOTIF i.e. use Xaw */

#ifdef HAVE_XAW3D
#include <X11/Xaw3d/Simple.h>
#include <X11/Xaw3d/Scrollbar.h>
#include <X11/Xaw3d/ThreeD.h>
#else /* !HAVE_XAW3D */
#include <X11/Xaw/Simple.h>
#include <X11/Xaw/Scrollbar.h>
#endif /* !HAVE_XAW3D */
#ifndef XtNpickTop
#define XtNpickTop "pickTop"
#endif /* !XtNpickTop */
#endif /* !USE_MOTIF */
#endif /* USE_TOOLKIT_SCROLL_BARS */

#endif /* USE_X_TOOLKIT */

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

#include "bitmaps/gray.xbm"

#ifdef HAVE_XKB
#include <X11/XKBlib.h>
#endif

/* Default to using XIM if available.  */
#ifdef USE_XIM
int use_xim = 1;
#else
int use_xim = 0;  /* configure --without-xim */
#endif

/* Non-zero means that a HELP_EVENT has been generated since Emacs
   start.  */

static bool any_help_event_p;

/* This is a chain of structures for all the X displays currently in
   use.  */

struct x_display_info *x_display_list;

#ifdef USE_X_TOOLKIT

/* The application context for Xt use.  */
XtAppContext Xt_app_con;
static String Xt_default_resources[] = {0};

/* Non-zero means user is interacting with a toolkit scroll bar.  */
static bool toolkit_scroll_bar_interaction;

#endif /* USE_X_TOOLKIT */

/* Non-zero timeout value means ignore next mouse click if it arrives
   before that timeout elapses (i.e. as part of the same sequence of
   events resulting from clicking on a frame to select it).  */

static Time ignore_next_mouse_click_timeout;

/* Used locally within XTread_socket.  */

static int x_noop_count;

static Lisp_Object Qalt, Qhyper, Qmeta, Qsuper, Qmodifier_value;

static Lisp_Object Qvendor_specific_keysyms;
static Lisp_Object Qlatin_1;

#ifdef USE_GTK
/* The name of the Emacs icon file.  */
static Lisp_Object xg_default_icon_file;

/* Used in gtkutil.c.  */
Lisp_Object Qx_gtk_map_stock;
#endif

/* Some functions take this as char *, not const char *.  */
static char emacs_class[] = EMACS_CLASS;

enum xembed_info
  {
    XEMBED_MAPPED = 1 << 0
  };

enum xembed_message
  {
    XEMBED_EMBEDDED_NOTIFY        = 0,
    XEMBED_WINDOW_ACTIVATE        = 1,
    XEMBED_WINDOW_DEACTIVATE      = 2,
    XEMBED_REQUEST_FOCUS          = 3,
    XEMBED_FOCUS_IN               = 4,
    XEMBED_FOCUS_OUT              = 5,
    XEMBED_FOCUS_NEXT             = 6,
    XEMBED_FOCUS_PREV             = 7,

    XEMBED_MODALITY_ON            = 10,
    XEMBED_MODALITY_OFF           = 11,
    XEMBED_REGISTER_ACCELERATOR   = 12,
    XEMBED_UNREGISTER_ACCELERATOR = 13,
    XEMBED_ACTIVATE_ACCELERATOR   = 14
  };

static bool x_alloc_nearest_color_1 (Display *, Colormap, XColor *);
static void x_set_window_size_1 (struct frame *, int, int, int, bool);
static void x_raise_frame (struct frame *);
static void x_lower_frame (struct frame *);
static const XColor *x_color_cells (Display *, int *);
static int x_io_error_quitter (Display *);
static struct terminal *x_create_terminal (struct x_display_info *);
void x_delete_terminal (struct terminal *);
static void x_update_end (struct frame *);
static void XTframe_up_to_date (struct frame *);
static void x_clear_frame (struct frame *);
static _Noreturn void x_ins_del_lines (struct frame *, int, int);
static void frame_highlight (struct frame *);
static void frame_unhighlight (struct frame *);
static void x_new_focus_frame (struct x_display_info *, struct frame *);
static void  x_focus_changed (int, int, struct x_display_info *,
                              struct frame *, struct input_event *);
static void XTframe_rehighlight (struct frame *);
static void x_frame_rehighlight (struct x_display_info *);
static void x_draw_hollow_cursor (struct window *, struct glyph_row *);
static void x_draw_bar_cursor (struct window *, struct glyph_row *, int,
                               enum text_cursor_kinds);

static void x_clip_to_row (struct window *, struct glyph_row *,
			   enum glyph_row_area, GC);
static void x_flush (struct frame *f);
static void x_update_begin (struct frame *);
static void x_update_window_begin (struct window *);
static struct scroll_bar *x_window_to_scroll_bar (Display *, Window);
static void x_scroll_bar_report_motion (struct frame **, Lisp_Object *,
                                        enum scroll_bar_part *,
                                        Lisp_Object *, Lisp_Object *,
                                        Time *);
static int x_handle_net_wm_state (struct frame *, const XPropertyEvent *);
static void x_check_fullscreen (struct frame *);
static void x_check_expected_move (struct frame *, int, int);
static void x_sync_with_move (struct frame *, int, int, int);
static int handle_one_xevent (struct x_display_info *,
			      const XEvent *, int *,
			      struct input_event *);
#if ! (defined USE_X_TOOLKIT || defined USE_MOTIF)
static int x_dispatch_event (XEvent *, Display *);
#endif
/* Don't declare this _Noreturn because we want no
   interference with debugging failing X calls.  */
static void x_connection_closed (Display *, const char *);
static void x_wm_set_window_state (struct frame *, int);
static void x_wm_set_icon_pixmap (struct frame *, ptrdiff_t);
static void x_initialize (void);


/* Flush display of frame F.  */

static void
x_flush (struct frame *f)
{
  eassert (f && FRAME_X_P (f));
  /* Don't call XFlush when it is not safe to redisplay; the X
     connection may be broken.  */
  if (!NILP (Vinhibit_redisplay))
    return;

  block_input ();
  XFlush (FRAME_X_DISPLAY (f));
  unblock_input ();
}


/* Remove calls to XFlush by defining XFlush to an empty replacement.
   Calls to XFlush should be unnecessary because the X output buffer
   is flushed automatically as needed by calls to XPending,
   XNextEvent, or XWindowEvent according to the XFlush man page.
   XTread_socket calls XPending.  Removing XFlush improves
   performance.  */

#define XFlush(DISPLAY)	(void) 0

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

#if 0

/* This is a function useful for recording debugging information about
   the sequence of occurrences in this file.  */

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

struct record event_record[100];

int event_record_index;

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

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

#endif /* 0 */



/* Return the struct x_display_info corresponding to DPY.  */

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

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

  return 0;
}

static Window
x_find_topmost_parent (struct frame *f)
{
  struct x_output *x = f->output_data.x;
  Window win = None, wi = x->parent_desc;
  Display *dpy = FRAME_X_DISPLAY (f);

  while (wi != FRAME_DISPLAY_INFO (f)->root_window)
    {
      Window root;
      Window *children;
      unsigned int nchildren;

      win = wi;
      XQueryTree (dpy, win, &root, &wi, &children, &nchildren);
      XFree (children);
    }

  return win;
}

#define OPAQUE  0xffffffff

void
x_set_frame_alpha (struct frame *f)
{
  struct x_display_info *dpyinfo = FRAME_DISPLAY_INFO (f);
  Display *dpy = FRAME_X_DISPLAY (f);
  Window win = FRAME_OUTER_WINDOW (f);
  double alpha = 1.0;
  double alpha_min = 1.0;
  unsigned long opac;
  Window parent;

  if (dpyinfo->x_highlight_frame == f)
    alpha = f->alpha[0];
  else
    alpha = f->alpha[1];

  if (FLOATP (Vframe_alpha_lower_limit))
    alpha_min = XFLOAT_DATA (Vframe_alpha_lower_limit);
  else if (INTEGERP (Vframe_alpha_lower_limit))
    alpha_min = (XINT (Vframe_alpha_lower_limit)) / 100.0;

  if (alpha < 0.0)
    return;
  else if (alpha > 1.0)
    alpha = 1.0;
  else if (0.0 <= alpha && alpha < alpha_min && alpha_min <= 1.0)
    alpha = alpha_min;

  opac = alpha * OPAQUE;

  x_catch_errors (dpy);

  /* If there is a parent from the window manager, put the property there
     also, to work around broken window managers that fail to do that.
     Do this unconditionally as this function is called on reparent when
     alpha has not changed on the frame.  */

  parent = x_find_topmost_parent (f);
  if (parent != None)
    XChangeProperty (dpy, parent, dpyinfo->Xatom_net_wm_window_opacity,
                     XA_CARDINAL, 32, PropModeReplace,
                     (unsigned char *) &opac, 1L);

  /* return unless necessary */
  {
    unsigned char *data;
    Atom actual;
    int rc, format;
    unsigned long n, left;

    rc = XGetWindowProperty (dpy, win, dpyinfo->Xatom_net_wm_window_opacity,
			     0L, 1L, False, XA_CARDINAL,
			     &actual, &format, &n, &left,
			     &data);

    if (rc == Success && actual != None)
      {
        unsigned long value = *(unsigned long *)data;
	XFree (data);
	if (value == opac)
	  {
	    x_uncatch_errors ();
	    return;
	  }
      }
  }

  XChangeProperty (dpy, win, dpyinfo->Xatom_net_wm_window_opacity,
		   XA_CARDINAL, 32, PropModeReplace,
		   (unsigned char *) &opac, 1L);
  x_uncatch_errors ();
}

int
x_display_pixel_height (struct x_display_info *dpyinfo)
{
  return HeightOfScreen (dpyinfo->screen);
}

int
x_display_pixel_width (struct x_display_info *dpyinfo)
{
  return WidthOfScreen (dpyinfo->screen);
}


/***********************************************************************
		    Starting and ending an update
 ***********************************************************************/

/* Start an update of frame F.  This function is installed as a hook
   for update_begin, i.e. it is called when update_begin is called.
   This function is called prior to calls to x_update_window_begin for
   each window being updated.  Currently, there is nothing to do here
   because all interesting stuff is done on a window basis.  */

static void
x_update_begin (struct frame *f)
{
  /* Nothing to do.  */
}


/* Start update of window W.  */

static void
x_update_window_begin (struct window *w)
{
  struct frame *f = XFRAME (WINDOW_FRAME (w));
  Mouse_HLInfo *hlinfo = MOUSE_HL_INFO (f);

  w->output_cursor = w->cursor;

  block_input ();

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

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

  unblock_input ();
}


/* Draw a vertical window border from (x,y0) to (x,y1)  */

static void
x_draw_vertical_window_border (struct window *w, int x, int y0, int y1)
{
  struct frame *f = XFRAME (WINDOW_FRAME (w));
  struct face *face;

  face = FACE_FROM_ID (f, VERTICAL_BORDER_FACE_ID);
  if (face)
    XSetForeground (FRAME_X_DISPLAY (f), f->output_data.x->normal_gc,
		    face->foreground);

  XDrawLine (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
	     f->output_data.x->normal_gc, x, y0, x, y1);
}

/* Draw a window divider from (x0,y0) to (x1,y1)  */

static void
x_draw_window_divider (struct window *w, int x0, int x1, int y0, int y1)
{
  struct frame *f = XFRAME (WINDOW_FRAME (w));
  struct face *face;

  face = FACE_FROM_ID (f, WINDOW_DIVIDER_FACE_ID);
  if (face)
    XSetForeground (FRAME_X_DISPLAY (f), f->output_data.x->normal_gc,
		    face->foreground);

  XFillRectangle (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
		  f->output_data.x->normal_gc, x0, y0, x1 - x0, y1 - y0);
}

/* End update of window W.

   Draw vertical borders between horizontally adjacent windows, and
   display W's cursor if CURSOR_ON_P is non-zero.

   MOUSE_FACE_OVERWRITTEN_P non-zero means that some row containing
   glyphs in mouse-face were overwritten.  In that case we have to
   make sure that the mouse-highlight is properly redrawn.

   W may be a menu bar pseudo-window in case we don't have X toolkit
   support.  Such windows don't have a cursor, so don't display it
   here.  */

static void
x_update_window_end (struct window *w, bool cursor_on_p,
		     bool mouse_face_overwritten_p)
{
  if (!w->pseudo_window_p)
    {
      block_input ();

      if (cursor_on_p)
	display_and_set_cursor (w, 1,
				w->output_cursor.hpos, w->output_cursor.vpos,
				w->output_cursor.x, w->output_cursor.y);

      if (draw_window_fringes (w, 1))
	{
	  if (WINDOW_RIGHT_DIVIDER_WIDTH (w))
	    x_draw_right_divider (w);
	  else
	    x_draw_vertical_border (w);
	}

      unblock_input ();
    }

  /* If a row with mouse-face was overwritten, arrange for
     XTframe_up_to_date to redisplay the mouse highlight.  */
  if (mouse_face_overwritten_p)
    reset_mouse_highlight (MOUSE_HL_INFO (XFRAME (w->frame)));
}


/* End update of frame F.  This function is installed as a hook in
   update_end.  */

static void
x_update_end (struct frame *f)
{
  /* Mouse highlight may be displayed again.  */
  MOUSE_HL_INFO (f)->mouse_face_defer = 0;

#ifndef XFlush
  block_input ();
  XFlush (FRAME_X_DISPLAY (f));
  unblock_input ();
#endif
}


/* This function is called from various places in xdisp.c
   whenever a complete update has been performed.  */

static void
XTframe_up_to_date (struct frame *f)
{
  if (FRAME_X_P (f))
    FRAME_MOUSE_UPDATE (f);
}


/* Draw truncation mark bitmaps, continuation mark bitmaps, overlay
   arrow bitmaps, or clear the fringes if no bitmaps are required
   before DESIRED_ROW is made current.  This function is called from
   update_window_line only if it is known that there are differences
   between bitmaps to be drawn between current row and DESIRED_ROW.  */

static void
x_after_update_window_line (struct window *w, struct glyph_row *desired_row)
{
  struct frame *f;
  int width, height;

  eassert (w);

  if (!desired_row->mode_line_p && !w->pseudo_window_p)
    desired_row->redraw_fringe_bitmaps_p = 1;

  /* When a window has disappeared, make sure that no rest of
     full-width rows stays visible in the internal border.  Could
     check here if updated window is the leftmost/rightmost window,
     but I guess it's not worth doing since vertically split windows
     are almost never used, internal border is rarely set, and the
     overhead is very small.  */
  if (windows_or_buffers_changed
      && desired_row->full_width_p
      && (f = XFRAME (w->frame),
	  width = FRAME_INTERNAL_BORDER_WIDTH (f),
	  width != 0)
      && (height = desired_row->visible_height,
	  height > 0))
    {
      int y = WINDOW_TO_FRAME_PIXEL_Y (w, max (0, desired_row->y));

      block_input ();
      x_clear_area (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
		    0, y, width, height);
      x_clear_area (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
		    FRAME_PIXEL_WIDTH (f) - width,
		    y, width, height);
      unblock_input ();
    }
}

static void
x_draw_fringe_bitmap (struct window *w, struct glyph_row *row, struct draw_fringe_bitmap_params *p)
{
  struct frame *f = XFRAME (WINDOW_FRAME (w));
  Display *display = FRAME_X_DISPLAY (f);
  Window window = FRAME_X_WINDOW (f);
  GC gc = f->output_data.x->normal_gc;
  struct face *face = p->face;

  /* Must clip because of partially visible lines.  */
  x_clip_to_row (w, row, ANY_AREA, gc);

  if (p->bx >= 0 && !p->overlay_p)
    {
      /* In case the same realized face is used for fringes and
	 for something displayed in the text (e.g. face `region' on
	 mono-displays, the fill style may have been changed to
	 FillSolid in x_draw_glyph_string_background.  */
      if (face->stipple)
	XSetFillStyle (display, face->gc, FillOpaqueStippled);
      else
	XSetForeground (display, face->gc, face->background);

      XFillRectangle (display, window, face->gc,
		      p->bx, p->by, p->nx, p->ny);

      if (!face->stipple)
	XSetForeground (display, face->gc, face->foreground);
    }

  if (p->which)
    {
      char *bits;
      Pixmap pixmap, clipmask = (Pixmap) 0;
      int depth = DefaultDepthOfScreen (FRAME_X_SCREEN (f));
      XGCValues gcv;

      if (p->wd > 8)
	bits = (char *) (p->bits + p->dh);
      else
	bits = (char *) p->bits + p->dh;

      /* Draw the bitmap.  I believe these small pixmaps can be cached
	 by the server.  */
      pixmap = XCreatePixmapFromBitmapData (display, window, bits, p->wd, p->h,
					    (p->cursor_p
					     ? (p->overlay_p ? face->background
						: f->output_data.x->cursor_pixel)
					     : face->foreground),
					    face->background, depth);

      if (p->overlay_p)
	{
	  clipmask = XCreatePixmapFromBitmapData (display,
						  FRAME_DISPLAY_INFO (f)->root_window,
						  bits, p->wd, p->h,
						  1, 0, 1);
	  gcv.clip_mask = clipmask;
	  gcv.clip_x_origin = p->x;
	  gcv.clip_y_origin = p->y;
	  XChangeGC (display, gc, GCClipMask | GCClipXOrigin | GCClipYOrigin, &gcv);
	}

      XCopyArea (display, pixmap, window, gc, 0, 0,
		 p->wd, p->h, p->x, p->y);
      XFreePixmap (display, pixmap);

      if (p->overlay_p)
	{
	  gcv.clip_mask = (Pixmap) 0;
	  XChangeGC (display, gc, GCClipMask, &gcv);
	  XFreePixmap (display, clipmask);
	}
    }

  XSetClipMask (display, gc, None);
}

/***********************************************************************
			    Glyph display
 ***********************************************************************/



static void x_set_glyph_string_clipping (struct glyph_string *);
static void x_set_glyph_string_gc (struct glyph_string *);
static void x_draw_glyph_string_foreground (struct glyph_string *);
static void x_draw_composite_glyph_string_foreground (struct glyph_string *);
static void x_draw_glyph_string_box (struct glyph_string *);
static void x_draw_glyph_string  (struct glyph_string *);
static _Noreturn void x_delete_glyphs (struct frame *, int);
static void x_compute_glyph_string_overhangs (struct glyph_string *);
static void x_set_cursor_gc (struct glyph_string *);
static void x_set_mode_line_face_gc (struct glyph_string *);
static void x_set_mouse_face_gc (struct glyph_string *);
static bool x_alloc_lighter_color (struct frame *, Display *, Colormap,
				   unsigned long *, double, int);
static void x_setup_relief_color (struct frame *, struct relief *,
                                  double, int, unsigned long);
static void x_setup_relief_colors (struct glyph_string *);
static void x_draw_image_glyph_string (struct glyph_string *);
static void x_draw_image_relief (struct glyph_string *);
static void x_draw_image_foreground (struct glyph_string *);
static void x_draw_image_foreground_1 (struct glyph_string *, Pixmap);
static void x_clear_glyph_string_rect (struct glyph_string *, int,
                                       int, int, int);
static void x_draw_relief_rect (struct frame *, int, int, int, int,
                                int, int, int, int, int, int,
                                XRectangle *);
static void x_draw_box_rect (struct glyph_string *, int, int, int, int,
                             int, int, int, XRectangle *);
static void x_scroll_bar_clear (struct frame *);

#ifdef GLYPH_DEBUG
static void x_check_font (struct frame *, struct font *);
#endif


/* Set S->gc to a suitable GC for drawing glyph string S in cursor
   face.  */

static void
x_set_cursor_gc (struct glyph_string *s)
{
  if (s->font == FRAME_FONT (s->f)
      && s->face->background == FRAME_BACKGROUND_PIXEL (s->f)
      && s->face->foreground == FRAME_FOREGROUND_PIXEL (s->f)
      && !s->cmp)
    s->gc = s->f->output_data.x->cursor_gc;
  else
    {
      /* Cursor on non-default face: must merge.  */
      XGCValues xgcv;
      unsigned long mask;

      xgcv.background = s->f->output_data.x->cursor_pixel;
      xgcv.foreground = s->face->background;

      /* If the glyph would be invisible, try a different foreground.  */
      if (xgcv.foreground == xgcv.background)
	xgcv.foreground = s->face->foreground;
      if (xgcv.foreground == xgcv.background)
	xgcv.foreground = s->f->output_data.x->cursor_foreground_pixel;
      if (xgcv.foreground == xgcv.background)
	xgcv.foreground = s->face->foreground;

      /* Make sure the cursor is distinct from text in this face.  */
      if (xgcv.background == s->face->background
	  && xgcv.foreground == s->face->foreground)
	{
	  xgcv.background = s->face->foreground;
	  xgcv.foreground = s->face->background;
	}

      IF_DEBUG (x_check_font (s->f, s->font));
      xgcv.graphics_exposures = False;
      mask = GCForeground | GCBackground | GCGraphicsExposures;

      if (FRAME_DISPLAY_INFO (s->f)->scratch_cursor_gc)
	XChangeGC (s->display, FRAME_DISPLAY_INFO (s->f)->scratch_cursor_gc,
		   mask, &xgcv);
      else
	FRAME_DISPLAY_INFO (s->f)->scratch_cursor_gc
	  = XCreateGC (s->display, s->window, mask, &xgcv);

      s->gc = FRAME_DISPLAY_INFO (s->f)->scratch_cursor_gc;
    }
}


/* Set up S->gc of glyph string S for drawing text in mouse face.  */

static void
x_set_mouse_face_gc (struct glyph_string *s)
{
  int face_id;
  struct face *face;

  /* What face has to be used last for the mouse face?  */
  face_id = MOUSE_HL_INFO (s->f)->mouse_face_face_id;
  face = FACE_FROM_ID (s->f, face_id);
  if (face == NULL)
    face = FACE_FROM_ID (s->f, MOUSE_FACE_ID);

  if (s->first_glyph->type == CHAR_GLYPH)
    face_id = FACE_FOR_CHAR (s->f, face, s->first_glyph->u.ch, -1, Qnil);
  else
    face_id = FACE_FOR_CHAR (s->f, face, 0, -1, Qnil);
  s->face = FACE_FROM_ID (s->f, face_id);
  PREPARE_FACE_FOR_DISPLAY (s->f, s->face);

  if (s->font == s->face->font)
    s->gc = s->face->gc;
  else
    {
      /* Otherwise construct scratch_cursor_gc with values from FACE
	 except for FONT.  */
      XGCValues xgcv;
      unsigned long mask;

      xgcv.background = s->face->background;
      xgcv.foreground = s->face->foreground;
      xgcv.graphics_exposures = False;
      mask = GCForeground | GCBackground | GCGraphicsExposures;

      if (FRAME_DISPLAY_INFO (s->f)->scratch_cursor_gc)
	XChangeGC (s->display, FRAME_DISPLAY_INFO (s->f)->scratch_cursor_gc,
		   mask, &xgcv);
      else
	FRAME_DISPLAY_INFO (s->f)->scratch_cursor_gc
	  = XCreateGC (s->display, s->window, mask, &xgcv);

      s->gc = FRAME_DISPLAY_INFO (s->f)->scratch_cursor_gc;

    }
  eassert (s->gc != 0);
}


/* Set S->gc of glyph string S to a GC suitable for drawing a mode line.
   Faces to use in the mode line have already been computed when the
   matrix was built, so there isn't much to do, here.  */

static void
x_set_mode_line_face_gc (struct glyph_string *s)
{
  s->gc = s->face->gc;
}


/* Set S->gc of glyph string S for drawing that glyph string.  Set
   S->stippled_p to a non-zero value if the face of S has a stipple
   pattern.  */

static void
x_set_glyph_string_gc (struct glyph_string *s)
{
  PREPARE_FACE_FOR_DISPLAY (s->f, s->face);

  if (s->hl == DRAW_NORMAL_TEXT)
    {
      s->gc = s->face->gc;
      s->stippled_p = s->face->stipple != 0;
    }
  else if (s->hl == DRAW_INVERSE_VIDEO)
    {
      x_set_mode_line_face_gc (s);
      s->stippled_p = s->face->stipple != 0;
    }
  else if (s->hl == DRAW_CURSOR)
    {
      x_set_cursor_gc (s);
      s->stippled_p = 0;
    }
  else if (s->hl == DRAW_MOUSE_FACE)
    {
      x_set_mouse_face_gc (s);
      s->stippled_p = s->face->stipple != 0;
    }
  else if (s->hl == DRAW_IMAGE_RAISED
	   || s->hl == DRAW_IMAGE_SUNKEN)
    {
      s->gc = s->face->gc;
      s->stippled_p = s->face->stipple != 0;
    }
  else
    {
      s->gc = s->face->gc;
      s->stippled_p = s->face->stipple != 0;
    }

  /* GC must have been set.  */
  eassert (s->gc != 0);
}


/* Set clipping for output of glyph string S.  S may be part of a mode
   line or menu if we don't have X toolkit support.  */

static void
x_set_glyph_string_clipping (struct glyph_string *s)
{
  XRectangle *r = s->clip;
  int n = get_glyph_string_clip_rects (s, r, 2);

  if (n > 0)
    XSetClipRectangles (s->display, s->gc, 0, 0, r, n, Unsorted);
  s->num_clips = n;
}


/* Set SRC's clipping for output of glyph string DST.  This is called
   when we are drawing DST's left_overhang or right_overhang only in
   the area of SRC.  */

static void
x_set_glyph_string_clipping_exactly (struct glyph_string *src, struct glyph_string *dst)
{
  XRectangle r;

  r.x = src->x;
  r.width = src->width;
  r.y = src->y;
  r.height = src->height;
  dst->clip[0] = r;
  dst->num_clips = 1;
  XSetClipRectangles (dst->display, dst->gc, 0, 0, &r, 1, Unsorted);
}


/* RIF:
   Compute left and right overhang of glyph string S.  */

static void
x_compute_glyph_string_overhangs (struct glyph_string *s)
{
  if (s->cmp == NULL
      && (s->first_glyph->type == CHAR_GLYPH
	  || s->first_glyph->type == COMPOSITE_GLYPH))
    {
      struct font_metrics metrics;

      if (s->first_glyph->type == CHAR_GLYPH)
	{
	  unsigned *code = alloca (sizeof (unsigned) * s->nchars);
	  struct font *font = s->font;
	  int i;

	  for (i = 0; i < s->nchars; i++)
	    code[i] = (s->char2b[i].byte1 << 8) | s->char2b[i].byte2;
	  font->driver->text_extents (font, code, s->nchars, &metrics);
	}
      else
	{
	  Lisp_Object gstring = composition_gstring_from_id (s->cmp_id);

	  composition_gstring_width (gstring, s->cmp_from, s->cmp_to, &metrics);
	}
      s->right_overhang = (metrics.rbearing > metrics.width
			   ? metrics.rbearing - metrics.width : 0);
      s->left_overhang = metrics.lbearing < 0 ? - metrics.lbearing : 0;
    }
  else if (s->cmp)
    {
      s->right_overhang = s->cmp->rbearing - s->cmp->pixel_width;
      s->left_overhang = - s->cmp->lbearing;
    }
}


/* Fill rectangle X, Y, W, H with background color of glyph string S.  */

static void
x_clear_glyph_string_rect (struct glyph_string *s, int x, int y, int w, int h)