Adjust further in response to jan.h.d's comments.

[bpt/emacs.git] / src / xselect.c

/* X Selection processing for Emacs.
   Copyright (C) 1993-1997, 2000-2011 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/>.  */


/* Rewritten by jwz */

#include <config.h>
#include <limits.h>
#include <stdio.h>      /* termhooks.h needs this */
#include <setjmp.h>

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#include <unistd.h>

#include "lisp.h"
#include "xterm.h"	/* for all of the X includes */
#include "dispextern.h"	/* frame.h seems to want this */
#include "frame.h"	/* Need this to get the X window of selected_frame */
#include "blockinput.h"
#include "buffer.h"
#include "process.h"
#include "termhooks.h"
#include "keyboard.h"
#include "character.h"

#include <X11/Xproto.h>

struct prop_location;
struct selection_data;

static Lisp_Object x_atom_to_symbol (Display *dpy, Atom atom);
static Atom symbol_to_x_atom (struct x_display_info *, Lisp_Object);
static void x_own_selection (Lisp_Object, Lisp_Object, Lisp_Object);
static Lisp_Object x_get_local_selection (Lisp_Object, Lisp_Object, int,
					  struct x_display_info *);
static void x_decline_selection_request (struct input_event *);
static Lisp_Object x_selection_request_lisp_error (Lisp_Object);
static Lisp_Object queue_selection_requests_unwind (Lisp_Object);
static Lisp_Object x_catch_errors_unwind (Lisp_Object);
static void x_reply_selection_request (struct input_event *, struct x_display_info *);
static int x_convert_selection (struct input_event *, Lisp_Object, Lisp_Object,
				Atom, int, struct x_display_info *);
static int waiting_for_other_props_on_window (Display *, Window);
static struct prop_location *expect_property_change (Display *, Window,
                                                     Atom, int);
static void unexpect_property_change (struct prop_location *);
static Lisp_Object wait_for_property_change_unwind (Lisp_Object);
static void wait_for_property_change (struct prop_location *);
static Lisp_Object x_get_foreign_selection (Lisp_Object, Lisp_Object,
					    Lisp_Object, Lisp_Object);
static Lisp_Object x_get_window_property_as_lisp_data (Display *,
                                                       Window, Atom,
                                                       Lisp_Object, Atom);
static Lisp_Object selection_data_to_lisp_data (Display *,
						const unsigned char *,
						ptrdiff_t, Atom, int);
static void lisp_data_to_selection_data (Display *, Lisp_Object,
                                         unsigned char **, Atom *,
					 ptrdiff_t *, int *, int *);
static Lisp_Object clean_local_selection_data (Lisp_Object);

/* Printing traces to stderr.  */

#ifdef TRACE_SELECTION
#define TRACE0(fmt) \
  fprintf (stderr, "%d: " fmt "\n", getpid ())
#define TRACE1(fmt, a0) \
  fprintf (stderr, "%d: " fmt "\n", getpid (), a0)
#define TRACE2(fmt, a0, a1) \
  fprintf (stderr, "%d: " fmt "\n", getpid (), a0, a1)
#define TRACE3(fmt, a0, a1, a2) \
  fprintf (stderr, "%d: " fmt "\n", getpid (), a0, a1, a2)
#else
#define TRACE0(fmt)		(void) 0
#define TRACE1(fmt, a0)		(void) 0
#define TRACE2(fmt, a0, a1)	(void) 0
#endif


static Lisp_Object QSECONDARY, QSTRING, QINTEGER, QCLIPBOARD, QTIMESTAMP,
  QTEXT, QDELETE, QMULTIPLE, QINCR, QEMACS_TMP, QTARGETS, QATOM, QNULL,
  QATOM_PAIR, QCLIPBOARD_MANAGER, QSAVE_TARGETS;

static Lisp_Object QCOMPOUND_TEXT;	/* This is a type of selection.  */
static Lisp_Object QUTF8_STRING;	/* This is a type of selection.  */

static Lisp_Object Qcompound_text_with_extensions;

static Lisp_Object Qforeign_selection;
static Lisp_Object Qx_lost_selection_functions, Qx_sent_selection_functions;

/* Bytes needed to represent 'long' data.  This is as per libX11; it
   is not necessarily sizeof (long).  */
#define X_LONG_SIZE 4

/* Extreme 'short' and 'long' values suitable for libX11.  */
#define X_SHRT_MAX 0x7fff
#define X_SHRT_MIN (-1 - X_SHRT_MAX)
#define X_LONG_MAX 0x7fffffff
#define X_LONG_MIN (-1 - X_LONG_MAX)

/* If this is a smaller number than the max-request-size of the display,
   emacs will use INCR selection transfer when the selection is larger
   than this.  The max-request-size is usually around 64k, so if you want
   emacs to use incremental selection transfers when the selection is
   smaller than that, set this.  I added this mostly for debugging the
   incremental transfer stuff, but it might improve server performance.

   This value cannot exceed INT_MAX / max (X_LONG_SIZE, sizeof (long))
   because it is multiplied by X_LONG_SIZE and by sizeof (long) in
   subscript calculations.  Similarly for PTRDIFF_MAX - 1 or SIZE_MAX
   - 1 in place of INT_MAX.  */
#define MAX_SELECTION_QUANTUM						\
  ((int) min (0xFFFFFF, (min (INT_MAX, min (PTRDIFF_MAX, SIZE_MAX) - 1)	\
			 / max (X_LONG_SIZE, sizeof (long)))))

static int
selection_quantum (Display *display)
{
  long mrs = XMaxRequestSize (display);
  return (mrs < MAX_SELECTION_QUANTUM / X_LONG_SIZE + 25
	  ? (mrs - 25) * X_LONG_SIZE
	  : MAX_SELECTION_QUANTUM);
}

#define LOCAL_SELECTION(selection_symbol,dpyinfo)			\
  assq_no_quit (selection_symbol, dpyinfo->terminal->Vselection_alist)

\f
/* Define a queue to save up SELECTION_REQUEST_EVENT events for later
   handling.  */

struct selection_event_queue
  {
    struct input_event event;
    struct selection_event_queue *next;
  };

static struct selection_event_queue *selection_queue;

/* Nonzero means queue up SELECTION_REQUEST_EVENT events.  */

static int x_queue_selection_requests;

/* Queue up an SELECTION_REQUEST_EVENT *EVENT, to be processed later.  */

static void
x_queue_event (struct input_event *event)
{
  struct selection_event_queue *queue_tmp;

  /* Don't queue repeated requests.
     This only happens for large requests which uses the incremental protocol.  */
  for (queue_tmp = selection_queue; queue_tmp; queue_tmp = queue_tmp->next)
    {
      if (!memcmp (&queue_tmp->event, event, sizeof (*event)))
	{
	  TRACE1 ("DECLINE DUP SELECTION EVENT %p", queue_tmp);
	  x_decline_selection_request (event);
	  return;
	}
    }

  queue_tmp
    = (struct selection_event_queue *) xmalloc (sizeof (struct selection_event_queue));

  if (queue_tmp != NULL)
    {
      TRACE1 ("QUEUE SELECTION EVENT %p", queue_tmp);
      queue_tmp->event = *event;
      queue_tmp->next = selection_queue;
      selection_queue = queue_tmp;
    }
}

/* Start queuing SELECTION_REQUEST_EVENT events.  */

static void
x_start_queuing_selection_requests (void)
{
  if (x_queue_selection_requests)
    abort ();

  x_queue_selection_requests++;
  TRACE1 ("x_start_queuing_selection_requests %d", x_queue_selection_requests);
}

/* Stop queuing SELECTION_REQUEST_EVENT events.  */

static void
x_stop_queuing_selection_requests (void)
{
  TRACE1 ("x_stop_queuing_selection_requests %d", x_queue_selection_requests);
  --x_queue_selection_requests;

  /* Take all the queued events and put them back
     so that they get processed afresh.  */

  while (selection_queue != NULL)
    {
      struct selection_event_queue *queue_tmp = selection_queue;
      TRACE1 ("RESTORE SELECTION EVENT %p", queue_tmp);
      kbd_buffer_unget_event (&queue_tmp->event);
      selection_queue = queue_tmp->next;
      xfree ((char *)queue_tmp);
    }
}
\f

/* This converts a Lisp symbol to a server Atom, avoiding a server
   roundtrip whenever possible.  */

static Atom
symbol_to_x_atom (struct x_display_info *dpyinfo, Lisp_Object sym)
{
  Atom val;
  if (NILP (sym))	    return 0;
  if (EQ (sym, QPRIMARY))   return XA_PRIMARY;
  if (EQ (sym, QSECONDARY)) return XA_SECONDARY;
  if (EQ (sym, QSTRING))    return XA_STRING;
  if (EQ (sym, QINTEGER))   return XA_INTEGER;
  if (EQ (sym, QATOM))	    return XA_ATOM;
  if (EQ (sym, QCLIPBOARD)) return dpyinfo->Xatom_CLIPBOARD;
  if (EQ (sym, QTIMESTAMP)) return dpyinfo->Xatom_TIMESTAMP;
  if (EQ (sym, QTEXT))	    return dpyinfo->Xatom_TEXT;
  if (EQ (sym, QCOMPOUND_TEXT)) return dpyinfo->Xatom_COMPOUND_TEXT;
  if (EQ (sym, QUTF8_STRING)) return dpyinfo->Xatom_UTF8_STRING;
  if (EQ (sym, QDELETE))    return dpyinfo->Xatom_DELETE;
  if (EQ (sym, QMULTIPLE))  return dpyinfo->Xatom_MULTIPLE;
  if (EQ (sym, QINCR))	    return dpyinfo->Xatom_INCR;
  if (EQ (sym, QEMACS_TMP)) return dpyinfo->Xatom_EMACS_TMP;
  if (EQ (sym, QTARGETS))   return dpyinfo->Xatom_TARGETS;
  if (EQ (sym, QNULL))	    return dpyinfo->Xatom_NULL;
  if (!SYMBOLP (sym)) abort ();

  TRACE1 (" XInternAtom %s", SSDATA (SYMBOL_NAME (sym)));
  BLOCK_INPUT;
  val = XInternAtom (dpyinfo->display, SSDATA (SYMBOL_NAME (sym)), False);
  UNBLOCK_INPUT;
  return val;
}


/* This converts a server Atom to a Lisp symbol, avoiding server roundtrips
   and calls to intern whenever possible.  */

static Lisp_Object
x_atom_to_symbol (Display *dpy, Atom atom)
{
  struct x_display_info *dpyinfo;
  char *str;
  Lisp_Object val;

  if (! atom)
    return Qnil;

  switch (atom)
    {
    case XA_PRIMARY:
      return QPRIMARY;
    case XA_SECONDARY:
      return QSECONDARY;
    case XA_STRING:
      return QSTRING;
    case XA_INTEGER:
      return QINTEGER;
    case XA_ATOM:
      return QATOM;
    }

  dpyinfo = x_display_info_for_display (dpy);
  if (dpyinfo == NULL)
    return Qnil;
  if (atom == dpyinfo->Xatom_CLIPBOARD)
    return QCLIPBOARD;
  if (atom == dpyinfo->Xatom_TIMESTAMP)
    return QTIMESTAMP;
  if (atom == dpyinfo->Xatom_TEXT)
    return QTEXT;
  if (atom == dpyinfo->Xatom_COMPOUND_TEXT)
    return QCOMPOUND_TEXT;
  if (atom == dpyinfo->Xatom_UTF8_STRING)
    return QUTF8_STRING;
  if (atom == dpyinfo->Xatom_DELETE)
    return QDELETE;
  if (atom == dpyinfo->Xatom_MULTIPLE)
    return QMULTIPLE;
  if (atom == dpyinfo->Xatom_INCR)
    return QINCR;
  if (atom == dpyinfo->Xatom_EMACS_TMP)
    return QEMACS_TMP;
  if (atom == dpyinfo->Xatom_TARGETS)
    return QTARGETS;
  if (atom == dpyinfo->Xatom_NULL)
    return QNULL;

  BLOCK_INPUT;
  str = XGetAtomName (dpy, atom);
  UNBLOCK_INPUT;
  TRACE1 ("XGetAtomName --> %s", str);
  if (! str) return Qnil;
  val = intern (str);
  BLOCK_INPUT;
  /* This was allocated by Xlib, so use XFree.  */
  XFree (str);
  UNBLOCK_INPUT;
  return val;
}
\f
/* Do protocol to assert ourself as a selection owner.
   FRAME shall be the owner; it must be a valid X frame.
   Update the Vselection_alist so that we can reply to later requests for
   our selection.  */

static void
x_own_selection (Lisp_Object selection_name, Lisp_Object selection_value,
		 Lisp_Object frame)
{
  struct frame *f = XFRAME (frame);
  Window selecting_window = FRAME_X_WINDOW (f);
  struct x_display_info *dpyinfo = FRAME_X_DISPLAY_INFO (f);
  Display *display = dpyinfo->display;
  Time timestamp = last_event_timestamp;
  Atom selection_atom = symbol_to_x_atom (dpyinfo, selection_name);

  BLOCK_INPUT;
  x_catch_errors (display);
  XSetSelectionOwner (display, selection_atom, selecting_window, timestamp);
  x_check_errors (display, "Can't set selection: %s");
  x_uncatch_errors ();
  UNBLOCK_INPUT;

  /* Now update the local cache */
  {
    Lisp_Object selection_data;
    Lisp_Object prev_value;

    selection_data = list4 (selection_name, selection_value,
			    INTEGER_TO_CONS (timestamp), frame);
    prev_value = LOCAL_SELECTION (selection_name, dpyinfo);

    dpyinfo->terminal->Vselection_alist
      = Fcons (selection_data, dpyinfo->terminal->Vselection_alist);

    /* If we already owned the selection, remove the old selection
       data.  Don't use Fdelq as that may QUIT.  */
    if (!NILP (prev_value))
      {
	/* We know it's not the CAR, so it's easy.  */
	Lisp_Object rest = dpyinfo->terminal->Vselection_alist;
	for (; CONSP (rest); rest = XCDR (rest))
	  if (EQ (prev_value, Fcar (XCDR (rest))))
	    {
	      XSETCDR (rest, XCDR (XCDR (rest)));
	      break;
	    }
      }
  }
}
\f
/* Given a selection-name and desired type, look up our local copy of
   the selection value and convert it to the type.
   The value is nil or a string.
   This function is used both for remote requests (LOCAL_REQUEST is zero)
   and for local x-get-selection-internal (LOCAL_REQUEST is nonzero).

   This calls random Lisp code, and may signal or gc.  */

static Lisp_Object
x_get_local_selection (Lisp_Object selection_symbol, Lisp_Object target_type,
		       int local_request, struct x_display_info *dpyinfo)
{
  Lisp_Object local_value;
  Lisp_Object handler_fn, value, check;
  int count;

  local_value = LOCAL_SELECTION (selection_symbol, dpyinfo);

  if (NILP (local_value)) return Qnil;

  /* TIMESTAMP is a special case.  */
  if (EQ (target_type, QTIMESTAMP))
    {
      handler_fn = Qnil;
      value = XCAR (XCDR (XCDR (local_value)));
    }
  else
    {
      /* Don't allow a quit within the converter.
	 When the user types C-g, he would be surprised
	 if by luck it came during a converter.  */
      count = SPECPDL_INDEX ();
      specbind (Qinhibit_quit, Qt);

      CHECK_SYMBOL (target_type);
      handler_fn = Fcdr (Fassq (target_type, Vselection_converter_alist));
      /* gcpro is not needed here since nothing but HANDLER_FN
	 is live, and that ought to be a symbol.  */

      if (!NILP (handler_fn))
	value = call3 (handler_fn,
		       selection_symbol, (local_request ? Qnil : target_type),
		       XCAR (XCDR (local_value)));
      else
	value = Qnil;
      unbind_to (count, Qnil);
    }

  /* Make sure this value is of a type that we could transmit
     to another X client.  */

  check = value;
  if (CONSP (value)
      && SYMBOLP (XCAR (value)))
    check = XCDR (value);

  if (STRINGP (check)
      || VECTORP (check)
      || SYMBOLP (check)
      || INTEGERP (check)
      || NILP (value))
    return value;
  /* Check for a value that CONS_TO_INTEGER could handle.  */
  else if (CONSP (check)
	   && INTEGERP (XCAR (check))
	   && (INTEGERP (XCDR (check))
	       ||
	       (CONSP (XCDR (check))
		&& INTEGERP (XCAR (XCDR (check)))
		&& NILP (XCDR (XCDR (check))))))
    return value;

  signal_error ("Invalid data returned by selection-conversion function",
		list2 (handler_fn, value));
}
\f
/* Subroutines of x_reply_selection_request.  */

/* Send a SelectionNotify event to the requestor with property=None,
   meaning we were unable to do what they wanted.  */

static void
x_decline_selection_request (struct input_event *event)
{
  XEvent reply_base;
  XSelectionEvent *reply = &(reply_base.xselection);

  reply->type = SelectionNotify;
  reply->display = SELECTION_EVENT_DISPLAY (event);
  reply->requestor = SELECTION_EVENT_REQUESTOR (event);
  reply->selection = SELECTION_EVENT_SELECTION (event);
  reply->time = SELECTION_EVENT_TIME (event);
  reply->target = SELECTION_EVENT_TARGET (event);
  reply->property = None;

  /* The reason for the error may be that the receiver has
     died in the meantime.  Handle that case.  */
  BLOCK_INPUT;
  x_catch_errors (reply->display);
  XSendEvent (reply->display, reply->requestor, False, 0L, &reply_base);
  XFlush (reply->display);
  x_uncatch_errors ();
  UNBLOCK_INPUT;
}

/* This is the selection request currently being processed.
   It is set to zero when the request is fully processed.  */
static struct input_event *x_selection_current_request;

/* Display info in x_selection_request.  */

static struct x_display_info *selection_request_dpyinfo;

/* Raw selection data, for sending to a requestor window.  */

struct selection_data
{
  unsigned char *data;
  ptrdiff_t size;
  int format;
  Atom type;
  int nofree;
  Atom property;
  /* This can be set to non-NULL during x_reply_selection_request, if
     the selection is waiting for an INCR transfer to complete.  Don't
     free these; that's done by unexpect_property_change.  */
  struct prop_location *wait_object;
  struct selection_data *next;
};

/* Linked list of the above (in support of MULTIPLE targets).  */

static struct selection_data *converted_selections;

/* "Data" to send a requestor for a failed MULTIPLE subtarget.  */
static Atom conversion_fail_tag;

/* Used as an unwind-protect clause so that, if a selection-converter signals
   an error, we tell the requester that we were unable to do what they wanted
   before we throw to top-level or go into the debugger or whatever.  */

static Lisp_Object
x_selection_request_lisp_error (Lisp_Object ignore)
{
  struct selection_data *cs, *next;

  for (cs = converted_selections; cs; cs = next)
    {
      next = cs->next;
      if (cs->nofree == 0 && cs->data)
	xfree (cs->data);
      xfree (cs);
    }
  converted_selections = NULL;

  if (x_selection_current_request != 0
      && selection_request_dpyinfo->display)
    x_decline_selection_request (x_selection_current_request);
  return Qnil;
}

static Lisp_Object
x_catch_errors_unwind (Lisp_Object dummy)
{
  BLOCK_INPUT;
  x_uncatch_errors ();
  UNBLOCK_INPUT;
  return Qnil;
}
\f

/* This stuff is so that INCR selections are reentrant (that is, so we can
   be servicing multiple INCR selection requests simultaneously.)  I haven't
   actually tested that yet.  */

/* Keep a list of the property changes that are awaited.  */

struct prop_location
{
  int identifier;
  Display *display;
  Window window;
  Atom property;
  int desired_state;
  int arrived;
  struct prop_location *next;
};

static struct prop_location *expect_property_change (Display *display, Window window, Atom property, int state);
static void wait_for_property_change (struct prop_location *location);
static void unexpect_property_change (struct prop_location *location);
static int waiting_for_other_props_on_window (Display *display, Window window);

static int prop_location_identifier;

static Lisp_Object property_change_reply;

static struct prop_location *property_change_reply_object;

static struct prop_location *property_change_wait_list;

static Lisp_Object
queue_selection_requests_unwind (Lisp_Object tem)
{
  x_stop_queuing_selection_requests ();
  return Qnil;
}

\f
/* Send the reply to a selection request event EVENT.  */

#ifdef TRACE_SELECTION
static int x_reply_selection_request_cnt;
#endif  /* TRACE_SELECTION */

static void
x_reply_selection_request (struct input_event *event, struct x_display_info *dpyinfo)
{
  XEvent reply_base;
  XSelectionEvent *reply = &(reply_base.xselection);
  Display *display = SELECTION_EVENT_DISPLAY (event);
  Window window = SELECTION_EVENT_REQUESTOR (event);
  ptrdiff_t bytes_remaining;
  int max_bytes = selection_quantum (display);
  int count = SPECPDL_INDEX ();
  struct selection_data *cs;

  reply->type = SelectionNotify;
  reply->display = display;
  reply->requestor = window;
  reply->selection = SELECTION_EVENT_SELECTION (event);
  reply->time = SELECTION_EVENT_TIME (event);
  reply->target = SELECTION_EVENT_TARGET (event);
  reply->property = SELECTION_EVENT_PROPERTY (event);
  if (reply->property == None)
    reply->property = reply->target;

  BLOCK_INPUT;
  /* The protected block contains wait_for_property_change, which can
     run random lisp code (process handlers) or signal.  Therefore, we
     put the x_uncatch_errors call in an unwind.  */
  record_unwind_protect (x_catch_errors_unwind, Qnil);
  x_catch_errors (display);

  /* Loop over converted selections, storing them in the requested
     properties.  If data is large, only store the first N bytes
     (section 2.7.2 of ICCCM).  Note that we store the data for a
     MULTIPLE request in the opposite order; the ICCM says only that
     the conversion itself must be done in the same order. */
  for (cs = converted_selections; cs; cs = cs->next)
    {
      if (cs->property == None)
	continue;

      bytes_remaining = cs->size;
      bytes_remaining *= cs->format >> 3;
      if (bytes_remaining <= max_bytes)
	{
	  /* Send all the data at once, with minimal handshaking.  */
	  TRACE1 ("Sending all %"pD"d bytes", bytes_remaining);
	  XChangeProperty (display, window, cs->property,
			   cs->type, cs->format, PropModeReplace,
			   cs->data, cs->size);
	}
      else
	{
	  /* Send an INCR tag to initiate incremental transfer.  */
	  long value[1];

	  TRACE2 ("Start sending %"pD"d bytes incrementally (%s)",
		  bytes_remaining, XGetAtomName (display, cs->property));
	  cs->wait_object
	    = expect_property_change (display, window, cs->property,
				      PropertyDelete);

	  /* XChangeProperty expects an array of long even if long is
	     more than 32 bits.  */
	  value[0] = min (bytes_remaining, X_LONG_MAX);
	  XChangeProperty (display, window, cs->property,
			   dpyinfo->Xatom_INCR, 32, PropModeReplace,
			   (unsigned char *) value, 1);
	  XSelectInput (display, window, PropertyChangeMask);
	}
    }

  /* Now issue the SelectionNotify event.  */
  XSendEvent (display, window, False, 0L, &reply_base);
  XFlush (display);

#ifdef TRACE_SELECTION
  {
    char *sel = XGetAtomName (display, reply->selection);
    char *tgt = XGetAtomName (display, reply->target);
    TRACE3 ("Sent SelectionNotify: %s, target %s (%d)",
	    sel, tgt, ++x_reply_selection_request_cnt);
    if (sel) XFree (sel);
    if (tgt) XFree (tgt);
  }
#endif /* TRACE_SELECTION */

  /* Finish sending the rest of each of the INCR values.  This should
     be improved; there's a chance of deadlock if more than one
     subtarget in a MULTIPLE selection requires an INCR transfer, and
     the requestor and Emacs loop waiting on different transfers.  */
  for (cs = converted_selections; cs; cs = cs->next)
    if (cs->wait_object)
      {
	int format_bytes = cs->format / 8;
	int had_errors = x_had_errors_p (display);
	UNBLOCK_INPUT;

	bytes_remaining = cs->size;
	bytes_remaining *= format_bytes;

	/* Wait for the requester to ack by deleting the property.
	   This can run Lisp code (process handlers) or signal.  */
	if (! had_errors)
	  {
	    TRACE1 ("Waiting for ACK (deletion of %s)",
		    XGetAtomName (display, cs->property));
	    wait_for_property_change (cs->wait_object);
	  }
	else
	  unexpect_property_change (cs->wait_object);

	while (bytes_remaining)
	  {
	    int i = ((bytes_remaining < max_bytes)
		     ? bytes_remaining
		     : max_bytes) / format_bytes;
	    BLOCK_INPUT;

	    cs->wait_object
	      = expect_property_change (display, window, cs->property,
					PropertyDelete);

	    TRACE1 ("Sending increment of %d elements", i);
	    TRACE1 ("Set %s to increment data",
		    XGetAtomName (display, cs->property));

	    /* Append the next chunk of data to the property.  */
	    XChangeProperty (display, window, cs->property,
			     cs->type, cs->format, PropModeAppend,
			     cs->data, i);
	    bytes_remaining -= i * format_bytes;
	    cs->data += i * ((cs->format == 32) ? sizeof (long)
			     : format_bytes);
	    XFlush (display);
	    had_errors = x_had_errors_p (display);
	    UNBLOCK_INPUT;

	    if (had_errors) break;

	    /* Wait for the requester to ack this chunk by deleting
	       the property.  This can run Lisp code or signal.  */
	    TRACE1 ("Waiting for increment ACK (deletion of %s)",
		    XGetAtomName (display, cs->property));
	    wait_for_property_change (cs->wait_object);
	  }

	/* Now write a zero-length chunk to the property to tell the
	   requester that we're done.  */
	BLOCK_INPUT;
	if (! waiting_for_other_props_on_window (display, window))
	  XSelectInput (display, window, 0L);

	TRACE1 ("Set %s to a 0-length chunk to indicate EOF",
		XGetAtomName (display, cs->property));
	XChangeProperty (display, window, cs->property,
			 cs->type, cs->format, PropModeReplace,
			 cs->data, 0);
	TRACE0 ("Done sending incrementally");
      }

  /* rms, 2003-01-03: I think I have fixed this bug.  */
  /* The window we're communicating with may have been deleted
     in the meantime (that's a real situation from a bug report).
     In this case, there may be events in the event queue still
     refering to the deleted window, and we'll get a BadWindow error
     in XTread_socket when processing the events.  I don't have
     an idea how to fix that.  gerd, 2001-01-98.   */
  /* 2004-09-10: XSync and UNBLOCK so that possible protocol errors are
     delivered before uncatch errors.  */
  XSync (display, False);
  UNBLOCK_INPUT;

  /* GTK queues events in addition to the queue in Xlib.  So we
     UNBLOCK to enter the event loop and get possible errors delivered,
     and then BLOCK again because x_uncatch_errors requires it.  */
  BLOCK_INPUT;
  /* This calls x_uncatch_errors.  */
  unbind_to (count, Qnil);
  UNBLOCK_INPUT;
}
\f
/* Handle a SelectionRequest event EVENT.
   This is called from keyboard.c when such an event is found in the queue.  */

static void
x_handle_selection_request (struct input_event *event)
{
  struct gcpro gcpro1, gcpro2;
  Time local_selection_time;

  Display *display = SELECTION_EVENT_DISPLAY (event);
  struct x_display_info *dpyinfo = x_display_info_for_display (display);
  Atom selection = SELECTION_EVENT_SELECTION (event);
  Lisp_Object selection_symbol = x_atom_to_symbol (display, selection);
  Atom target = SELECTION_EVENT_TARGET (event);
  Lisp_Object target_symbol = x_atom_to_symbol (display, target);
  Atom property = SELECTION_EVENT_PROPERTY (event);
  Lisp_Object local_selection_data;
  int success = 0;
  int count = SPECPDL_INDEX ();
  GCPRO2 (local_selection_data, target_symbol);

  if (!dpyinfo) goto DONE;

  local_selection_data = LOCAL_SELECTION (selection_symbol, dpyinfo);

  /* Decline if we don't own any selections.  */
  if (NILP (local_selection_data)) goto DONE;

  /* Decline requests issued prior to our acquiring the selection.  */
  CONS_TO_INTEGER (XCAR (XCDR (XCDR (local_selection_data))),
		   Time, local_selection_time);
  if (SELECTION_EVENT_TIME (event) != CurrentTime
      && local_selection_time > SELECTION_EVENT_TIME (event))
    goto DONE;

  x_selection_current_request = event;
  selection_request_dpyinfo = dpyinfo;
  record_unwind_protect (x_selection_request_lisp_error, Qnil);

  /* We might be able to handle nested x_handle_selection_requests,
     but this is difficult to test, and seems unimportant.  */
  x_start_queuing_selection_requests ();
  record_unwind_protect (queue_selection_requests_unwind, Qnil);

  TRACE2 ("x_handle_selection_request: selection=%s, target=%s",
	  SDATA (SYMBOL_NAME (selection_symbol)),
	  SDATA (SYMBOL_NAME (target_symbol)));

  if (EQ (target_symbol, QMULTIPLE))
    {
      /* For MULTIPLE targets, the event property names a list of atom
	 pairs; the first atom names a target and the second names a
	 non-None property.  */
      Window requestor = SELECTION_EVENT_REQUESTOR (event);
      Lisp_Object multprop;
      ptrdiff_t j, nselections;

      if (property == None) goto DONE;
      multprop
	= x_get_window_property_as_lisp_data (display, requestor, property,
					      QMULTIPLE, selection);

      if (!VECTORP (multprop) || ASIZE (multprop) % 2)
	goto DONE;

      nselections = ASIZE (multprop) / 2;
      /* Perform conversions.  This can signal.  */
      for (j = 0; j < nselections; j++)
	{
	  Lisp_Object subtarget = AREF (multprop, 2*j);
	  Atom subproperty = symbol_to_x_atom (dpyinfo,
					       AREF (multprop, 2*j+1));

	  if (subproperty != None)
	    x_convert_selection (event, selection_symbol, subtarget,
				 subproperty, 1, dpyinfo);
	}
      success = 1;
    }
  else
    {
      if (property == None)
	property = SELECTION_EVENT_TARGET (event);
      success = x_convert_selection (event, selection_symbol,
				     target_symbol, property,
				     0, dpyinfo);
    }

 DONE:

  if (success)
    x_reply_selection_request (event, dpyinfo);
  else
    x_decline_selection_request (event);
  x_selection_current_request = 0;

  /* Run the `x-sent-selection-functions' abnormal hook.  */
  if (!NILP (Vx_sent_selection_functions)
      && !EQ (Vx_sent_selection_functions, Qunbound))
    {
      Lisp_Object args[4];
      args[0] = Qx_sent_selection_functions;
      args[1] = selection_symbol;
      args[2] = target_symbol;
      args[3] = success ? Qt : Qnil;
      Frun_hook_with_args (4, args);
    }

  unbind_to (count, Qnil);
  UNGCPRO;
}

/* Perform the requested selection conversion, and write the data to
   the converted_selections linked list, where it can be accessed by
   x_reply_selection_request.  If FOR_MULTIPLE is non-zero, write out
   the data even if conversion fails, using conversion_fail_tag.

   Return 0 if the selection failed to convert, 1 otherwise.  */

static int
x_convert_selection (struct input_event *event, Lisp_Object selection_symbol,
		     Lisp_Object target_symbol, Atom property,
		     int for_multiple, struct x_display_info *dpyinfo)
{
  struct gcpro gcpro1;
  Lisp_Object lisp_selection;
  struct selection_data *cs;
  GCPRO1 (lisp_selection);

  lisp_selection
    = x_get_local_selection (selection_symbol, target_symbol,
			     0, dpyinfo);

  /* A nil return value means we can't perform the conversion.  */
  if (NILP (lisp_selection)
      || (CONSP (lisp_selection) && NILP (XCDR (lisp_selection))))
    {
      if (for_multiple)
	{
	  cs = xmalloc (sizeof (struct selection_data));
	  cs->data = (unsigned char *) &conversion_fail_tag;
	  cs->size = 1;
	  cs->format = 32;
	  cs->type = XA_ATOM;
	  cs->nofree = 1;
	  cs->property = property;
	  cs->wait_object = NULL;
	  cs->next = converted_selections;
	  converted_selections = cs;
	}

      UNGCPRO;
      return 0;
    }

  /* Otherwise, record the converted selection to binary.  */
  cs = xmalloc (sizeof (struct selection_data));
  cs->nofree = 1;
  cs->property = property;
  cs->wait_object = NULL;
  cs->next = converted_selections;
  converted_selections = cs;
  lisp_data_to_selection_data (SELECTION_EVENT_DISPLAY (event),
			       lisp_selection,
			       &(cs->data), &(cs->type),
			       &(cs->size), &(cs->format),
			       &(cs->nofree));
  UNGCPRO;
  return 1;
}
\f
/* Handle a SelectionClear event EVENT, which indicates that some
   client cleared out our previously asserted selection.
   This is called from keyboard.c when such an event is found in the queue.  */

static void
x_handle_selection_clear (struct input_event *event)
{
  Display *display = SELECTION_EVENT_DISPLAY (event);
  Atom selection = SELECTION_EVENT_SELECTION (event);
  Time changed_owner_time = SELECTION_EVENT_TIME (event);

  Lisp_Object selection_symbol, local_selection_data;
  Time local_selection_time;
  struct x_display_info *dpyinfo = x_display_info_for_display (display);
  Lisp_Object Vselection_alist;

  TRACE0 ("x_handle_selection_clear");

  if (!dpyinfo) return;

  selection_symbol = x_atom_to_symbol (display, selection);
  local_selection_data = LOCAL_SELECTION (selection_symbol, dpyinfo);

  /* Well, we already believe that we don't own it, so that's just fine.  */
  if (NILP (local_selection_data)) return;

  CONS_TO_INTEGER (XCAR (XCDR (XCDR (local_selection_data))),
		   Time, local_selection_time);

  /* We have reasserted the selection since this SelectionClear was
     generated, so we can disregard it.  */
  if (changed_owner_time != CurrentTime
      && local_selection_time > changed_owner_time)
    return;

  /* Otherwise, really clear.  Don't use Fdelq as that may QUIT;.  */
  Vselection_alist = dpyinfo->terminal->Vselection_alist;
  if (EQ (local_selection_data, CAR (Vselection_alist)))
    Vselection_alist = XCDR (Vselection_alist);
  else
    {
      Lisp_Object rest;
      for (rest = Vselection_alist; CONSP (rest); rest = XCDR (rest))
	if (EQ (local_selection_data, CAR (XCDR (rest))))
	  {
	    XSETCDR (rest, XCDR (XCDR (rest)));
	    break;
	  }
    }
  dpyinfo->terminal->Vselection_alist = Vselection_alist;

  /* Run the `x-lost-selection-functions' abnormal hook.  */
  {
    Lisp_Object args[2];
    args[0] = Qx_lost_selection_functions;
    args[1] = selection_symbol;
    Frun_hook_with_args (2, args);
  }

  prepare_menu_bars ();
  redisplay_preserve_echo_area (20);
}

void
x_handle_selection_event (struct input_event *event)
{
  TRACE0 ("x_handle_selection_event");
  if (event->kind != SELECTION_REQUEST_EVENT)
    x_handle_selection_clear (event);
  else if (x_queue_selection_requests)
    x_queue_event (event);
  else
    x_handle_selection_request (event);
}


/* Clear all selections that were made from frame F.
   We do this when about to delete a frame.  */

void
x_clear_frame_selections (FRAME_PTR f)
{
  Lisp_Object frame;
  Lisp_Object rest;
  struct x_display_info *dpyinfo = FRAME_X_DISPLAY_INFO (f);
  struct terminal *t = dpyinfo->terminal;

  XSETFRAME (frame, f);

  /* Delete elements from the beginning of Vselection_alist.  */
  while (CONSP (t->Vselection_alist)
	 && EQ (frame, XCAR (XCDR (XCDR (XCDR (XCAR (t->Vselection_alist)))))))
    {
      /* Run the `x-lost-selection-functions' abnormal hook.  */
      Lisp_Object args[2];
      args[0] = Qx_lost_selection_functions;
      args[1] = Fcar (Fcar (t->Vselection_alist));
      Frun_hook_with_args (2, args);

      t->Vselection_alist = XCDR (t->Vselection_alist);
    }

  /* Delete elements after the beginning of Vselection_alist.  */
  for (rest = t->Vselection_alist; CONSP (rest); rest = XCDR (rest))
    if (CONSP (XCDR (rest))
	&& EQ (frame, XCAR (XCDR (XCDR (XCDR (XCAR (XCDR (rest))))))))
      {
	Lisp_Object args[2];
	args[0] = Qx_lost_selection_functions;
	args[1] = XCAR (XCAR (XCDR (rest)));
	Frun_hook_with_args (2, args);
	XSETCDR (rest, XCDR (XCDR (rest)));
	break;
      }
}
\f
/* Nonzero if any properties for DISPLAY and WINDOW
   are on the list of what we are waiting for.  */

static int
waiting_for_other_props_on_window (Display *display, Window window)
{
  struct prop_location *rest = property_change_wait_list;
  while (rest)
    if (rest->display == display && rest->window == window)
      return 1;
    else
      rest = rest->next;
  return 0;
}

/* Add an entry to the list of property changes we are waiting for.
   DISPLAY, WINDOW, PROPERTY, STATE describe what we will wait for.
   The return value is a number that uniquely identifies
   this awaited property change.  */

static struct prop_location *
expect_property_change (Display *display, Window window, Atom property, int state)
{
  struct prop_location *pl = (struct prop_location *) xmalloc (sizeof *pl);
  pl->identifier = ++prop_location_identifier;
  pl->display = display;
  pl->window = window;
  pl->property = property;
  pl->desired_state = state;
  pl->next = property_change_wait_list;
  pl->arrived = 0;
  property_change_wait_list = pl;
  return pl;
}

/* Delete an entry from the list of property changes we are waiting for.
   IDENTIFIER is the number that uniquely identifies the entry.  */

static void
unexpect_property_change (struct prop_location *location)
{
  struct prop_location *prev = 0, *rest = property_change_wait_list;
  while (rest)
    {
      if (rest == location)
	{
	  if (prev)
	    prev->next = rest->next;
	  else
	    property_change_wait_list = rest->next;
	  xfree (rest);
	  return;
	}
      prev = rest;
      rest = rest->next;
    }
}

/* Remove the property change expectation element for IDENTIFIER.  */

static Lisp_Object
wait_for_property_change_unwind (Lisp_Object loc)
{
  struct prop_location *location = XSAVE_VALUE (loc)->pointer;

  unexpect_property_change (location);
  if (location == property_change_reply_object)
    property_change_reply_object = 0;
  return Qnil;
}

/* Actually wait for a property change.
   IDENTIFIER should be the value that expect_property_change returned.  */

static void
wait_for_property_change (struct prop_location *location)
{
  int secs, usecs;
  int count = SPECPDL_INDEX ();

  if (property_change_reply_object)
    abort ();

  /* Make sure to do unexpect_property_change if we quit or err.  */
  record_unwind_protect (wait_for_property_change_unwind,
			 make_save_value (location, 0));

  XSETCAR (property_change_reply, Qnil);
  property_change_reply_object = location;

  /* If the event we are waiting for arrives beyond here, it will set
     property_change_reply, because property_change_reply_object says so.  */
  if (! location->arrived)
    {
      secs = x_selection_timeout / 1000;
      usecs = (x_selection_timeout % 1000) * 1000;
      TRACE2 ("  Waiting %d secs, %d usecs", secs, usecs);
      wait_reading_process_output (secs, usecs, 0, 0,
				   property_change_reply, NULL, 0);

      if (NILP (XCAR (property_change_reply)))
	{
	  TRACE0 ("  Timed out");
	  error ("Timed out waiting for property-notify event");
	}
    }

  unbind_to (count, Qnil);
}

/* Called from XTread_socket in response to a PropertyNotify event.  */

void
x_handle_property_notify (XPropertyEvent *event)
{
  struct prop_location *rest;

  for (rest = property_change_wait_list; rest; rest = rest->next)
    {
      if (!rest->arrived
	  && rest->property == event->atom
	  && rest->window == event->window
	  && rest->display == event->display
	  && rest->desired_state == event->state)
	{
	  TRACE2 ("Expected %s of property %s",
		  (event->state == PropertyDelete ? "deletion" : "change"),
		  XGetAtomName (event->display, event->atom));

	  rest->arrived = 1;

	  /* If this is the one wait_for_property_change is waiting for,
	     tell it to wake up.  */
	  if (rest == property_change_reply_object)
	    XSETCAR (property_change_reply, Qt);

	  return;
	}
    }
}


\f
/* Variables for communication with x_handle_selection_notify.  */
static Atom reading_which_selection;
static Lisp_Object reading_selection_reply;
static Window reading_selection_window;

/* Do protocol to read selection-data from the server.
   Converts this to Lisp data and returns it.
   FRAME is the frame whose X window shall request the selection.  */

static Lisp_Object
x_get_foreign_selection (Lisp_Object selection_symbol, Lisp_Object target_type,
			 Lisp_Object time_stamp, Lisp_Object frame)
{
  struct frame *f = XFRAME (frame);
  struct x_display_info *dpyinfo = FRAME_X_DISPLAY_INFO (f);
  Display *display = dpyinfo->display;
  Window requestor_window = FRAME_X_WINDOW (f);
  Time requestor_time = last_event_timestamp;
  Atom target_property = dpyinfo->Xatom_EMACS_TMP;
  Atom selection_atom = symbol_to_x_atom (dpyinfo, selection_symbol);
  Atom type_atom = (CONSP (target_type)
		    ? symbol_to_x_atom (dpyinfo, XCAR (target_type))
		    : symbol_to_x_atom (dpyinfo, target_type));
  int secs, usecs;

  if (!FRAME_LIVE_P (f))
    return Qnil;

  if (! NILP (time_stamp))
    CONS_TO_INTEGER (time_stamp, Time, requestor_time);

  BLOCK_INPUT;
  TRACE2 ("Get selection %s, type %s",
	  XGetAtomName (display, type_atom),
	  XGetAtomName (display, target_property));

  x_catch_errors (display);
  XConvertSelection (display, selection_atom, type_atom, target_property,
		     requestor_window, requestor_time);
  x_check_errors (display, "Can't convert selection: %s");
  x_uncatch_errors ();

  /* Prepare to block until the reply has been read.  */
  reading_selection_window = requestor_window;
  reading_which_selection = selection_atom;
  XSETCAR (reading_selection_reply, Qnil);

  /* It should not be necessary to stop handling selection requests
     during this time.  In fact, the SAVE_TARGETS mechanism requires
     us to handle a clipboard manager's requests before it returns
     SelectionNotify. */
#if 0
  x_start_queuing_selection_requests ();
  record_unwind_protect (queue_selection_requests_unwind, Qnil);
#endif

  UNBLOCK_INPUT;

  /* This allows quits.  Also, don't wait forever.  */
  secs = x_selection_timeout / 1000;
  usecs = (x_selection_timeout % 1000) * 1000;
  TRACE1 ("  Start waiting %d secs for SelectionNotify", secs);
  wait_reading_process_output (secs, usecs, 0, 0,
			       reading_selection_reply, NULL, 0);
  TRACE1 ("  Got event = %d", !NILP (XCAR (reading_selection_reply)));

  if (NILP (XCAR (reading_selection_reply)))
    error ("Timed out waiting for reply from selection owner");
  if (EQ (XCAR (reading_selection_reply), Qlambda))
    return Qnil;

  /* Otherwise, the selection is waiting for us on the requested property.  */
  return
    x_get_window_property_as_lisp_data (display, requestor_window,
					target_property, target_type,
					selection_atom);
}
\f
/* Subroutines of x_get_window_property_as_lisp_data */

/* Use xfree, not XFree, to free the data obtained with this function.  */

static void
x_get_window_property (Display *display, Window window, Atom property,
		       unsigned char **data_ret, ptrdiff_t *bytes_ret,
		       Atom *actual_type_ret, int *actual_format_ret,
		       unsigned long *actual_size_ret, int delete_p)
{
  ptrdiff_t total_size;
  unsigned long bytes_remaining;
  ptrdiff_t offset = 0;
  unsigned char *data = 0;
  unsigned char *tmp_data = 0;
  int result;
  int buffer_size = selection_quantum (display);

  /* Wide enough to avoid overflow in expressions using it.  */
  ptrdiff_t x_long_size = X_LONG_SIZE;

  /* Maximum value for TOTAL_SIZE.  It cannot exceed PTRDIFF_MAX - 1
     and SIZE_MAX - 1, for an extra byte at the end.  And it cannot
     exceed LONG_MAX * X_LONG_SIZE, for XGetWindowProperty.  */
  ptrdiff_t total_size_max =
    ((min (PTRDIFF_MAX, SIZE_MAX) - 1) / x_long_size < LONG_MAX
     ? min (PTRDIFF_MAX, SIZE_MAX) - 1
     : LONG_MAX * x_long_size);

  BLOCK_INPUT;

  /* First probe the thing to find out how big it is.  */
  result = XGetWindowProperty (display, window, property,
			       0L, 0L, False, AnyPropertyType,
			       actual_type_ret, actual_format_ret,
			       actual_size_ret,
			       &bytes_remaining, &tmp_data);
  if (result != Success)
    goto done;

  /* This was allocated by Xlib, so use XFree.  */
  XFree ((char *) tmp_data);

  if (*actual_type_ret == None || *actual_format_ret == 0)
    goto done;

  if (total_size_max < bytes_remaining)
    goto size_overflow;
  total_size = bytes_remaining;
  data = malloc (total_size + 1);
  if (! data)
    goto memory_exhausted;

  /* Now read, until we've gotten it all.  */
  while (bytes_remaining)
    {
      ptrdiff_t bytes_gotten;
      int bytes_per_item;
      result
	= XGetWindowProperty (display, window, property,
			      offset / X_LONG_SIZE,
			      buffer_size / X_LONG_SIZE,
			      False,
			      AnyPropertyType,
			      actual_type_ret, actual_format_ret,
			      actual_size_ret, &bytes_remaining, &tmp_data);

      /* If this doesn't return Success at this point, it means that
	 some clod deleted the selection while we were in the midst of
	 reading it.  Deal with that, I guess.... */
      if (result != Success)
	break;

      bytes_per_item = *actual_format_ret >> 3;
      xassert (*actual_size_ret <= buffer_size / bytes_per_item);

      /* The man page for XGetWindowProperty says:
         "If the returned format is 32, the returned data is represented
          as a long array and should be cast to that type to obtain the
          elements."
         This applies even if long is more than 32 bits, the X library
         converts from 32 bit elements received from the X server to long
         and passes the long array to us.  Thus, for that case memcpy can not
         be used.  We convert to a 32 bit type here, because so much code
         assume on that.

         The bytes and offsets passed to XGetWindowProperty refers to the
         property and those are indeed in 32 bit quantities if format is 32.  */

      bytes_gotten = *actual_size_ret;
      bytes_gotten *= bytes_per_item;

      TRACE2 ("Read %"pD"d bytes from property %s",
	      bytes_gotten, XGetAtomName (display, property));

      if (total_size - offset < bytes_gotten)
	{
	  unsigned char *data1;
	  ptrdiff_t remaining_lim = total_size_max - offset - bytes_gotten;
	  if (remaining_lim < 0 || remaining_lim < bytes_remaining)
	    goto size_overflow;
	  total_size = offset + bytes_gotten + bytes_remaining;
	  data1 = realloc (data, total_size + 1);
	  if (! data1)
	    goto memory_exhausted;
	  data = data1;
	}

      if (32 < BITS_PER_LONG && *actual_format_ret == 32)
        {
          unsigned long i;
	  int  *idata = (int *) (data + offset);
          long *ldata = (long *) tmp_data;

          for (i = 0; i < *actual_size_ret; ++i)
	    idata[i] = ldata[i];
        }
      else
	memcpy (data + offset, tmp_data, bytes_gotten);

      offset += bytes_gotten;

      /* This was allocated by Xlib, so use XFree.  */
      XFree ((char *) tmp_data);
    }

  XFlush (display);
  data[offset] = '\0';

 done:
  UNBLOCK_INPUT;
  *data_ret = data;
  *bytes_ret = offset;
  return;

 size_overflow:
  free (data);
  UNBLOCK_INPUT;
  memory_full (SIZE_MAX);

 memory_exhausted:
  free (data);
  UNBLOCK_INPUT;
  memory_full (total_size + 1);
}
\f
/* Use xfree, not XFree, to free the data obtained with this function.  */

static void
receive_incremental_selection (Display *display, Window window, Atom property,
			       Lisp_Object target_type,
			       unsigned int min_size_bytes,
			       unsigned char **data_ret,
			       ptrdiff_t *size_bytes_ret,
			       Atom *type_ret, int *format_ret,
			       unsigned long *size_ret)
{
  ptrdiff_t offset = 0;
  struct prop_location *wait_object;
  if (min (PTRDIFF_MAX, SIZE_MAX) < min_size_bytes)
    memory_full (SIZE_MAX);
  *data_ret = (unsigned char *) xmalloc (min_size_bytes);
  *size_bytes_ret = min_size_bytes;

  TRACE1 ("Read %u bytes incrementally", min_size_bytes);

  /* At this point, we have read an INCR property.
     Delete the property to ack it.
     (But first, prepare to receive the next event in this handshake.)

     Now, we must loop, waiting for the sending window to put a value on
     that property, then reading the property, then deleting it to ack.
     We are done when the sender places a property of length 0.
   */
  BLOCK_INPUT;
  XSelectInput (display, window, STANDARD_EVENT_SET | PropertyChangeMask);
  TRACE1 ("  Delete property %s",
	  SDATA (SYMBOL_NAME (x_atom_to_symbol (display, property))));
  XDeleteProperty (display, window, property);
  TRACE1 ("  Expect new value of property %s",
	  SDATA (SYMBOL_NAME (x_atom_to_symbol (display, property))));
  wait_object = expect_property_change (display, window, property,
					PropertyNewValue);
  XFlush (display);
  UNBLOCK_INPUT;

  while (1)
    {
      unsigned char *tmp_data;
      ptrdiff_t tmp_size_bytes;

      TRACE0 ("  Wait for property change");
      wait_for_property_change (wait_object);

      /* expect it again immediately, because x_get_window_property may
	 .. no it won't, I don't get it.
	 .. Ok, I get it now, the Xt code that implements INCR is broken. */
      TRACE0 ("  Get property value");
      x_get_window_property (display, window, property,
			     &tmp_data, &tmp_size_bytes,
			     type_ret, format_ret, size_ret, 1);

      TRACE1 ("  Read increment of %"pD"d bytes", tmp_size_bytes);

      if (tmp_size_bytes == 0) /* we're done */
	{
	  TRACE0 ("Done reading incrementally");

	  if (! waiting_for_other_props_on_window (display, window))
	    XSelectInput (display, window, STANDARD_EVENT_SET);
	  /* Use xfree, not XFree, because x_get_window_property
	     calls xmalloc itself.  */
	  xfree (tmp_data);
	  break;
	}

      BLOCK_INPUT;
      TRACE1 ("  ACK by deleting property %s",
	      XGetAtomName (display, property));
      XDeleteProperty (display, window, property);
      wait_object = expect_property_change (display, window, property,
					    PropertyNewValue);
      XFlush (display);
      UNBLOCK_INPUT;

      if (*size_bytes_ret - offset < tmp_size_bytes)
	*data_ret = xpalloc (*data_ret, size_bytes_ret,
			     tmp_size_bytes - (*size_bytes_ret - offset),
			     -1, 1);

      memcpy ((*data_ret) + offset, tmp_data, tmp_size_bytes);
      offset += tmp_size_bytes;

      /* Use xfree, not XFree, because x_get_window_property
	 calls xmalloc itself.  */
      xfree (tmp_data);
    }
}

\f
/* Fetch a value from property PROPERTY of X window WINDOW on display
   DISPLAY.  TARGET_TYPE and SELECTION_ATOM are used in error message
   if this fails.  */

static Lisp_Object
x_get_window_property_as_lisp_data (Display *display, Window window,
				    Atom property,
				    Lisp_Object target_type,
				    Atom selection_atom)
{
  Atom actual_type;
  int actual_format;
  unsigned long actual_size;
  unsigned char *data = 0;
  ptrdiff_t bytes = 0;
  Lisp_Object val;
  struct x_display_info *dpyinfo = x_display_info_for_display (display);

  TRACE0 ("Reading selection data");

  x_get_window_property (display, window, property, &data, &bytes,
			 &actual_type, &actual_format, &actual_size, 1);
  if (! data)
    {
      int there_is_a_selection_owner;
      BLOCK_INPUT;
      there_is_a_selection_owner
	= XGetSelectionOwner (display, selection_atom);
      UNBLOCK_INPUT;
      if (there_is_a_selection_owner)
	signal_error ("Selection owner couldn't convert",
		      actual_type
		      ? list2 (target_type,
			       x_atom_to_symbol (display, actual_type))
		      : target_type);
      else
	signal_error ("No selection",
		      x_atom_to_symbol (display, selection_atom));
    }

  if (actual_type == dpyinfo->Xatom_INCR)
    {
      /* That wasn't really the data, just the beginning.  */

      unsigned int min_size_bytes = * ((unsigned int *) data);
      BLOCK_INPUT;
      /* Use xfree, not XFree, because x_get_window_property
	 calls xmalloc itself.  */
      xfree ((char *) data);
      UNBLOCK_INPUT;
      receive_incremental_selection (display, window, property, target_type,
				     min_size_bytes, &data, &bytes,
				     &actual_type, &actual_format,
				     &actual_size);
    }

  BLOCK_INPUT;
  TRACE1 ("  Delete property %s", XGetAtomName (display, property));
  XDeleteProperty (display, window, property);
  XFlush (display);
  UNBLOCK_INPUT;

  /* It's been read.  Now convert it to a lisp object in some semi-rational
     manner.  */
  val = selection_data_to_lisp_data (display, data, bytes,
				     actual_type, actual_format);

  /* Use xfree, not XFree, because x_get_window_property
     calls xmalloc itself.  */
  xfree ((char *) data);
  return val;
}
\f
/* These functions convert from the selection data read from the server into
   something that we can use from Lisp, and vice versa.

	Type:	Format:	Size:		Lisp Type:
	-----	-------	-----		-----------
	*	8	*		String
	ATOM	32	1		Symbol
	ATOM	32	> 1		Vector of Symbols
	*	16	1		Integer
	*	16	> 1		Vector of Integers
	*	32	1		if <=16 bits: Integer
					if > 16 bits: Cons of top16, bot16
	*	32	> 1		Vector of the above

   When converting a Lisp number to C, it is assumed to be of format 16 if
   it is an integer, and of format 32 if it is a cons of two integers.

   When converting a vector of numbers from Lisp to C, it is assumed to be
   of format 16 if every element in the vector is an integer, and is assumed
   to be of format 32 if any element is a cons of two integers.

   When converting an object to C, it may be of the form (SYMBOL . <data>)
   where SYMBOL is what we should claim that the type is.  Format and
   representation are as above.

   Important: When format is 32, data should contain an array of int,
   not an array of long as the X library returns.  This makes a difference
   when sizeof(long) != sizeof(int).  */



static Lisp_Object
selection_data_to_lisp_data (Display *display, const unsigned char *data,
			     ptrdiff_t size, Atom type, int format)
{
  struct x_display_info *dpyinfo = x_display_info_for_display (display);

  if (type == dpyinfo->Xatom_NULL)
    return QNULL;

  /* Convert any 8-bit data to a string, for compactness.  */
  else if (format == 8)
    {
      Lisp_Object str, lispy_type;

      str = make_unibyte_string ((char *) data, size);
      /* Indicate that this string is from foreign selection by a text
	 property `foreign-selection' so that the caller of
	 x-get-selection-internal (usually x-get-selection) can know
	 that the string must be decode.  */
      if (type == dpyinfo->Xatom_COMPOUND_TEXT)
	lispy_type = QCOMPOUND_TEXT;
      else if (type == dpyinfo->Xatom_UTF8_STRING)
	lispy_type = QUTF8_STRING;
      else
	lispy_type = QSTRING;
      Fput_text_property (make_number (0), make_number (size),
			  Qforeign_selection, lispy_type, str);
      return str;
    }
  /* Convert a single atom to a Lisp_Symbol.  Convert a set of atoms to
     a vector of symbols.  */
  else if (type == XA_ATOM
	   /* Treat ATOM_PAIR type similar to list of atoms.  */
	   || type == dpyinfo->Xatom_ATOM_PAIR)
    {
      ptrdiff_t i;
      /* On a 64 bit machine sizeof(Atom) == sizeof(long) == 8.
         But the callers of these function has made sure the data for
         format == 32 is an array of int.  Thus, use int instead
         of Atom.  */
      int *idata = (int *) data;

      if (size == sizeof (int))
	return x_atom_to_symbol (display, (Atom) idata[0]);
      else
	{
	  Lisp_Object v = Fmake_vector (make_number (size / sizeof (int)),
					make_number (0));
	  for (i = 0; i < size / sizeof (int); i++)
	    Faset (v, make_number (i),
                   x_atom_to_symbol (display, (Atom) idata[i]));
	  return v;
	}
    }

  /* Convert a single 16-bit number or a small 32-bit number to a Lisp_Int.
     If the number is 32 bits and won't fit in a Lisp_Int,
     convert it to a cons of integers, 16 bits in each half.
   */
  else if (format == 32 && size == sizeof (int))
    return INTEGER_TO_CONS (((unsigned int *) data) [0]);
  else if (format == 16 && size == sizeof (short))
    return make_number (((unsigned short *) data) [0]);

  /* Convert any other kind of data to a vector of numbers, represented
     as above (as an integer, or a cons of two 16 bit integers.)
   */
  else if (format == 16)
    {
      ptrdiff_t i;
      Lisp_Object v;
      v = Fmake_vector (make_number (size / 2), make_number (0));
      for (i = 0; i < size / 2; i++)
	{
	  EMACS_INT j = ((unsigned short *) data) [i];
	  Faset (v, make_number (i), make_number (j));
	}
      return v;
    }
  else
    {
      ptrdiff_t i;
      Lisp_Object v = Fmake_vector (make_number (size / X_LONG_SIZE),
				    make_number (0));
      for (i = 0; i < size / X_LONG_SIZE; i++)
	{
	  unsigned int j = ((unsigned int *) data) [i];
	  Faset (v, make_number (i), INTEGER_TO_CONS (j));
	}
      return v;
    }
}


/* Use xfree, not XFree, to free the data obtained with this function.  */

static void
lisp_data_to_selection_data (Display *display, Lisp_Object obj,
			     unsigned char **data_ret, Atom *type_ret,
			     ptrdiff_t *size_ret,
			     int *format_ret, int *nofree_ret)
{
  Lisp_Object type = Qnil;
  struct x_display_info *dpyinfo = x_display_info_for_display (display);

  *nofree_ret = 0;

  if (CONSP (obj) && SYMBOLP (XCAR (obj)))
    {
      type = XCAR (obj);
      obj = XCDR (obj);
      if (CONSP (obj) && NILP (XCDR (obj)))
	obj = XCAR (obj);
    }

  if (EQ (obj, QNULL) || (EQ (type, QNULL)))
    {				/* This is not the same as declining */
      *format_ret = 32;
      *size_ret = 0;
      *data_ret = 0;
      type = QNULL;
    }
  else if (STRINGP (obj))
    {
      if (SCHARS (obj) < SBYTES (obj))
	/* OBJ is a multibyte string containing a non-ASCII char.  */
	signal_error ("Non-ASCII string must be encoded in advance", obj);
      if (NILP (type))
	type = QSTRING;
      *format_ret = 8;
      *size_ret = SBYTES (obj);
      *data_ret = SDATA (obj);
      *nofree_ret = 1;
    }
  else if (SYMBOLP (obj))
    {
      *data_ret = (unsigned char *) xmalloc (sizeof (Atom) + 1);
      *format_ret = 32;
      *size_ret = 1;
      (*data_ret) [sizeof (Atom)] = 0;
      (*(Atom **) data_ret) [0] = symbol_to_x_atom (dpyinfo, obj);
      if (NILP (type)) type = QATOM;
    }
  else if (RANGED_INTEGERP (X_SHRT_MIN, obj, X_SHRT_MAX))
    {
      *data_ret = (unsigned char *) xmalloc (sizeof (short) + 1);
      *format_ret = 16;
      *size_ret = 1;
      (*data_ret) [sizeof (short)] = 0;
      (*(short **) data_ret) [0] = XINT (obj);
      if (NILP (type)) type = QINTEGER;
    }
  else if (INTEGERP (obj)
	   || (CONSP (obj) && INTEGERP (XCAR (obj))
	       && (INTEGERP (XCDR (obj))
		   || (CONSP (XCDR (obj))
		       && INTEGERP (XCAR (XCDR (obj)))))))
    {
      *data_ret = (unsigned char *) xmalloc (sizeof (long) + 1);
      *format_ret = 32;
      *size_ret = 1;
      (*data_ret) [sizeof (long)] = 0;
      (*(long **) data_ret) [0] = cons_to_signed (obj, X_LONG_MIN, X_LONG_MAX);
      if (NILP (type)) type = QINTEGER;
    }
  else if (VECTORP (obj))
    {
      /* Lisp_Vectors may represent a set of ATOMs;
	 a set of 16 or 32 bit INTEGERs;
	 or a set of ATOM_PAIRs (represented as [[A1 A2] [A3 A4] ...]
       */
      ptrdiff_t i;
      ptrdiff_t size = ASIZE (obj);

      if (SYMBOLP (XVECTOR (obj)->contents [0]))
	/* This vector is an ATOM set */
	{
	  if (NILP (type)) type = QATOM;
	  for (i = 0; i < size; i++)
	    if (!SYMBOLP (XVECTOR (obj)->contents [i]))
	      signal_error ("All elements of selection vector must have same type", obj);

	  *data_ret = xnmalloc (size, sizeof (Atom));
	  *format_ret = 32;
	  *size_ret = size;
	  for (i = 0; i < size; i++)
	    (*(Atom **) data_ret) [i]
	      = symbol_to_x_atom (dpyinfo, XVECTOR (obj)->contents [i]);
	}
      else
	/* This vector is an INTEGER set, or something like it */
	{
	  int format = 16;
	  int data_size = sizeof (short);
	  if (NILP (type)) type = QINTEGER;
	  for (i = 0; i < size; i++)
	    {
	      intmax_t v = cons_to_signed (XVECTOR (obj)->contents[i],
					   X_LONG_MIN, X_LONG_MAX);
	      if (X_SHRT_MIN <= v && v <= X_SHRT_MAX)
		{
		  /* Use sizeof (long) even if it is more than 32 bits.
		     See comment in x_get_window_property and
		     x_fill_property_data.  */
		  data_size = sizeof (long);
		  format = 32;
		}
	    }
	  *data_ret = xnmalloc (size, data_size);
	  *format_ret = format;
	  *size_ret = size;
	  for (i = 0; i < size; i++)
	    {
	      long v = cons_to_signed (XVECTOR (obj)->contents[i],
				       X_LONG_MIN, X_LONG_MAX);
	      if (format == 32)
		(*((long **) data_ret)) [i] = v;
	      else
		(*((short **) data_ret)) [i] = v;
	    }
	}
    }
  else
    signal_error (/* Qselection_error */ "Unrecognized selection data", obj);

  *type_ret = symbol_to_x_atom (dpyinfo, type);
}

static Lisp_Object
clean_local_selection_data (Lisp_Object obj)
{
  if (CONSP (obj)
      && INTEGERP (XCAR (obj))
      && CONSP (XCDR (obj))
      && INTEGERP (XCAR (XCDR (obj)))
      && NILP (XCDR (XCDR (obj))))
    obj = Fcons (XCAR (obj), XCDR (obj));

  if (CONSP (obj)
      && INTEGERP (XCAR (obj))
      && INTEGERP (XCDR (obj)))
    {
      if (XINT (XCAR (obj)) == 0)
	return XCDR (obj);
      if (XINT (XCAR (obj)) == -1)
	return make_number (- XINT (XCDR (obj)));
    }
  if (VECTORP (obj))
    {
      ptrdiff_t i;
      ptrdiff_t size = ASIZE (obj);
      Lisp_Object copy;
      if (size == 1)
	return clean_local_selection_data (XVECTOR (obj)->contents [0]);
      copy = Fmake_vector (make_number (size), Qnil);
      for (i = 0; i < size; i++)
	XVECTOR (copy)->contents [i]
	  = clean_local_selection_data (XVECTOR (obj)->contents [i]);
      return copy;
    }
  return obj;
}
\f
/* Called from XTread_socket to handle SelectionNotify events.
   If it's the selection we are waiting for, stop waiting
   by setting the car of reading_selection_reply to non-nil.
   We store t there if the reply is successful, lambda if not.  */

void
x_handle_selection_notify (XSelectionEvent *event)
{
  if (event->requestor != reading_selection_window)
    return;
  if (event->selection != reading_which_selection)
    return;

  TRACE0 ("Received SelectionNotify");
  XSETCAR (reading_selection_reply,
	   (event->property != 0 ? Qt : Qlambda));
}

\f
/* From a Lisp_Object, return a suitable frame for selection
   operations.  OBJECT may be a frame, a terminal object, or nil
   (which stands for the selected frame--or, if that is not an X
   frame, the first X display on the list).  If no suitable frame can
   be found, return NULL.  */

static struct frame *
frame_for_x_selection (Lisp_Object object)
{
  Lisp_Object tail;
  struct frame *f;

  if (NILP (object))
    {
      f = XFRAME (selected_frame);
      if (FRAME_X_P (f) && FRAME_LIVE_P (f))
	return f;

      for (tail = Vframe_list; CONSP (tail); tail = XCDR (tail))
	{
	  f = XFRAME (XCAR (tail));
	  if (FRAME_X_P (f) && FRAME_LIVE_P (f))
	    return f;
	}
    }
  else if (TERMINALP (object))
    {
      struct terminal *t = get_terminal (object, 1);
      if (t->type == output_x_window)
	{
	  for (tail = Vframe_list; CONSP (tail); tail = XCDR (tail))
	    {
	      f = XFRAME (XCAR (tail));
	      if (FRAME_LIVE_P (f) && f->terminal == t)
		return f;
	    }
	}
    }
  else if (FRAMEP (object))
    {
      f = XFRAME (object);
      if (FRAME_X_P (f) && FRAME_LIVE_P (f))
	return f;
    }

  return NULL;
}


DEFUN ("x-own-selection-internal", Fx_own_selection_internal,
       Sx_own_selection_internal, 2, 3, 0,
       doc: /* Assert an X selection of type SELECTION and value VALUE.
SELECTION is a symbol, typically `PRIMARY', `SECONDARY', or `CLIPBOARD'.
\(Those are literal upper-case symbol names, since that's what X expects.)
VALUE is typically a string, or a cons of two markers, but may be
anything that the functions on `selection-converter-alist' know about.

FRAME should be a frame that should own the selection.  If omitted or
nil, it defaults to the selected frame.  */)
  (Lisp_Object selection, Lisp_Object value, Lisp_Object frame)
{
  if (NILP (frame)) frame = selected_frame;
  if (!FRAME_LIVE_P (XFRAME (frame)) || !FRAME_X_P (XFRAME (frame)))
    error ("X selection unavailable for this frame");

  CHECK_SYMBOL (selection);
  if (NILP (value)) error ("VALUE may not be nil");
  x_own_selection (selection, value, frame);
  return value;
}


/* Request the selection value from the owner.  If we are the owner,
   simply return our selection value.  If we are not the owner, this
   will block until all of the data has arrived.  */

DEFUN ("x-get-selection-internal", Fx_get_selection_internal,
       Sx_get_selection_internal, 2, 4, 0,
       doc: /* Return text selected from some X window.
SELECTION is a symbol, typically `PRIMARY', `SECONDARY', or `CLIPBOARD'.
\(Those are literal upper-case symbol names, since that's what X expects.)
TYPE is the type of data desired, typically `STRING'.
TIME_STAMP is the time to use in the XConvertSelection call for foreign
selections.  If omitted, defaults to the time for the last event.

TERMINAL should be a terminal object or a frame specifying the X
server to query.  If omitted or nil, that stands for the selected
frame's display, or the first available X display.  */)
  (Lisp_Object selection_symbol, Lisp_Object target_type,
   Lisp_Object time_stamp, Lisp_Object terminal)
{
  Lisp_Object val = Qnil;
  struct gcpro gcpro1, gcpro2;
  struct frame *f = frame_for_x_selection (terminal);
  GCPRO2 (target_type, val); /* we store newly consed data into these */

  CHECK_SYMBOL (selection_symbol);
  CHECK_SYMBOL (target_type);
  if (EQ (target_type, QMULTIPLE))
    error ("Retrieving MULTIPLE selections is currently unimplemented");
  if (!f)
    error ("X selection unavailable for this frame");

  val = x_get_local_selection (selection_symbol, target_type, 1,
			       FRAME_X_DISPLAY_INFO (f));

  if (NILP (val) && FRAME_LIVE_P (f))
    {
      Lisp_Object frame;
      XSETFRAME (frame, f);
      RETURN_UNGCPRO (x_get_foreign_selection (selection_symbol, target_type,
					       time_stamp, frame));
    }

  if (CONSP (val) && SYMBOLP (XCAR (val)))
    {
      val = XCDR (val);
      if (CONSP (val) && NILP (XCDR (val)))
	val = XCAR (val);
    }
  RETURN_UNGCPRO (clean_local_selection_data (val));
}

DEFUN ("x-disown-selection-internal", Fx_disown_selection_internal,
       Sx_disown_selection_internal, 1, 3, 0,
       doc: /* If we own the selection SELECTION, disown it.
Disowning it means there is no such selection.

TERMINAL should be a terminal object or a frame specifying the X
server to query.  If omitted or nil, that stands for the selected
frame's display, or the first available X display.  */)
  (Lisp_Object selection, Lisp_Object time_object, Lisp_Object terminal)
{
  Time timestamp;
  Atom selection_atom;
  union {
    struct selection_input_event sie;
    struct input_event ie;
  } event;
  struct frame *f = frame_for_x_selection (terminal);
  struct x_display_info *dpyinfo;

  if (!f)
    return Qnil;

  dpyinfo = FRAME_X_DISPLAY_INFO (f);
  CHECK_SYMBOL (selection);

  /* Don't disown the selection when we're not the owner.  */
  if (NILP (LOCAL_SELECTION (selection, dpyinfo)))
    return Qnil;

  selection_atom = symbol_to_x_atom (dpyinfo, selection);

  BLOCK_INPUT;
  if (NILP (time_object))
    timestamp = last_event_timestamp;
  else
    CONS_TO_INTEGER (time_object, Time, timestamp);
  XSetSelectionOwner (dpyinfo->display, selection_atom, None, timestamp);
  UNBLOCK_INPUT;

  /* It doesn't seem to be guaranteed that a SelectionClear event will be
     generated for a window which owns the selection when that window sets
     the selection owner to None.  The NCD server does, the MIT Sun4 server
     doesn't.  So we synthesize one; this means we might get two, but
     that's ok, because the second one won't have any effect.  */
  SELECTION_EVENT_DISPLAY (&event.sie) = dpyinfo->display;
  SELECTION_EVENT_SELECTION (&event.sie) = selection_atom;
  SELECTION_EVENT_TIME (&event.sie) = timestamp;
  x_handle_selection_clear (&event.ie);

  return Qt;
}

DEFUN ("x-selection-owner-p", Fx_selection_owner_p, Sx_selection_owner_p,
       0, 2, 0,
       doc: /* Whether the current Emacs process owns the given X Selection.
The arg should be the name of the selection in question, typically one of
the symbols `PRIMARY', `SECONDARY', or `CLIPBOARD'.
\(Those are literal upper-case symbol names, since that's what X expects.)
For convenience, the symbol nil is the same as `PRIMARY',
and t is the same as `SECONDARY'.

TERMINAL should be a terminal object or a frame specifying the X
server to query.  If omitted or nil, that stands for the selected
frame's display, or the first available X display.  */)
  (Lisp_Object selection, Lisp_Object terminal)
{
  struct frame *f = frame_for_x_selection (terminal);

  CHECK_SYMBOL (selection);
  if (EQ (selection, Qnil)) selection = QPRIMARY;
  if (EQ (selection, Qt)) selection = QSECONDARY;

  if (f && !NILP (LOCAL_SELECTION (selection, FRAME_X_DISPLAY_INFO (f))))
    return Qt;
  else
    return Qnil;
}

DEFUN ("x-selection-exists-p", Fx_selection_exists_p, Sx_selection_exists_p,
       0, 2, 0,
       doc: /* Whether there is an owner for the given X selection.
SELECTION should be the name of the selection in question, typically
one of the symbols `PRIMARY', `SECONDARY', or `CLIPBOARD'.  (X expects
these literal upper-case names.)  The symbol nil is the same as
`PRIMARY', and t is the same as `SECONDARY'.

TERMINAL should be a terminal object or a frame specifying the X
server to query.  If omitted or nil, that stands for the selected
frame's display, or the first available X display.  */)
  (Lisp_Object selection, Lisp_Object terminal)
{
  Window owner;
  Atom atom;
  struct frame *f = frame_for_x_selection (terminal);
  struct x_display_info *dpyinfo;

  CHECK_SYMBOL (selection);
  if (EQ (selection, Qnil)) selection = QPRIMARY;
  if (EQ (selection, Qt)) selection = QSECONDARY;

  if (!f)
    return Qnil;

  dpyinfo = FRAME_X_DISPLAY_INFO (f);

  if (!NILP (LOCAL_SELECTION (selection, dpyinfo)))
    return Qt;

  atom = symbol_to_x_atom (dpyinfo, selection);
  if (atom == 0) return Qnil;
  BLOCK_INPUT;
  owner = XGetSelectionOwner (dpyinfo->display, atom);
  UNBLOCK_INPUT;
  return (owner ? Qt : Qnil);
}

\f
/* Send clipboard manager a SAVE_TARGETS request with a UTF8_STRING
   property (http://www.freedesktop.org/wiki/ClipboardManager).  */

static Lisp_Object
x_clipboard_manager_save (Lisp_Object frame)
{
  struct frame *f = XFRAME (frame);
  struct x_display_info *dpyinfo = FRAME_X_DISPLAY_INFO (f);
  Atom data = dpyinfo->Xatom_UTF8_STRING;

  XChangeProperty (FRAME_X_DISPLAY (f), FRAME_X_WINDOW (f),
		   dpyinfo->Xatom_EMACS_TMP,
		   dpyinfo->Xatom_ATOM, 32, PropModeReplace,
		   (unsigned char *) &data, 1);
  x_get_foreign_selection (QCLIPBOARD_MANAGER, QSAVE_TARGETS,
			   Qnil, frame);
  return Qt;
}

/* Error handler for x_clipboard_manager_save_frame.  */

static Lisp_Object
x_clipboard_manager_error_1 (Lisp_Object err)
{
  Lisp_Object args[2];
  args[0] = build_string ("X clipboard manager error: %s\n\
If the problem persists, set `x-select-enable-clipboard-manager' to nil.");
  args[1] = CAR (CDR (err));
  Fmessage (2, args);
  return Qnil;
}

/* Error handler for x_clipboard_manager_save_all.  */

static Lisp_Object
x_clipboard_manager_error_2 (Lisp_Object err)
{
  fprintf (stderr, "Error saving to X clipboard manager.\n\
If the problem persists, set `x-select-enable-clipboard-manager' \
to nil.\n");
  return Qnil;
}

/* Called from delete_frame: save any clipboard owned by FRAME to the
   clipboard manager.  Do nothing if FRAME does not own the clipboard,
   or if no clipboard manager is present.  */

void
x_clipboard_manager_save_frame (Lisp_Object frame)
{
  struct frame *f;

  if (!NILP (Vx_select_enable_clipboard_manager)
      && FRAMEP (frame)
      && (f = XFRAME (frame), FRAME_X_P (f))
      && FRAME_LIVE_P (f))
    {
      struct x_display_info *dpyinfo = FRAME_X_DISPLAY_INFO (f);
      Lisp_Object local_selection
	= LOCAL_SELECTION (QCLIPBOARD, dpyinfo);

      if (!NILP (local_selection)
	  && EQ (frame, XCAR (XCDR (XCDR (XCDR (local_selection)))))
	  && XGetSelectionOwner (dpyinfo->display,
				 dpyinfo->Xatom_CLIPBOARD_MANAGER))
	internal_condition_case_1 (x_clipboard_manager_save, frame, Qt,
				   x_clipboard_manager_error_1);
    }
}

/* Called from Fkill_emacs: save any clipboard owned by FRAME to the
   clipboard manager.  Do nothing if FRAME does not own the clipboard,
   or if no clipboard manager is present.  */

void
x_clipboard_manager_save_all (void)
{
  /* Loop through all X displays, saving owned clipboards.  */
  struct x_display_info *dpyinfo;
  Lisp_Object local_selection, local_frame;

  if (NILP (Vx_select_enable_clipboard_manager))
    return;

  for (dpyinfo = x_display_list; dpyinfo; dpyinfo = dpyinfo->next)
    {
      local_selection = LOCAL_SELECTION (QCLIPBOARD, dpyinfo);
      if (NILP (local_selection)
	  || !XGetSelectionOwner (dpyinfo->display,
				  dpyinfo->Xatom_CLIPBOARD_MANAGER))
	continue;

      local_frame = XCAR (XCDR (XCDR (XCDR (local_selection))));
      if (FRAME_LIVE_P (XFRAME (local_frame)))
	internal_condition_case_1 (x_clipboard_manager_save, local_frame,
				   Qt, x_clipboard_manager_error_2);
    }
}

\f
/***********************************************************************
                      Drag and drop support
***********************************************************************/
/* Check that lisp values are of correct type for x_fill_property_data.
   That is, number, string or a cons with two numbers (low and high 16
   bit parts of a 32 bit number).  Return the number of items in DATA,
   or -1 if there is an error.  */

int
x_check_property_data (Lisp_Object data)
{
  Lisp_Object iter;
  int size = 0;

  for (iter = data; CONSP (iter); iter = XCDR (iter))
    {
      Lisp_Object o = XCAR (iter);

      if (! NUMBERP (o) && ! STRINGP (o) && ! CONSP (o))
        return -1;
      else if (CONSP (o) &&
               (! NUMBERP (XCAR (o)) || ! NUMBERP (XCDR (o))))
        return -1;
      if (size == INT_MAX)
	return -1;
      size++;
    }

  return size;
}

/* Convert lisp values to a C array.  Values may be a number, a string
   which is taken as an X atom name and converted to the atom value, or
   a cons containing the two 16 bit parts of a 32 bit number.

   DPY is the display use to look up X atoms.
   DATA is a Lisp list of values to be converted.
   RET is the C array that contains the converted values.  It is assumed
   it is big enough to hold all values.
   FORMAT is 8, 16 or 32 and denotes char/short/long for each C value to
   be stored in RET.  Note that long is used for 32 even if long is more
   than 32 bits (see man pages for XChangeProperty, XGetWindowProperty and
   XClientMessageEvent).  */

void
x_fill_property_data (Display *dpy, Lisp_Object data, void *ret, int format)
{
  long val;
  long  *d32 = (long  *) ret;
  short *d16 = (short *) ret;
  char  *d08 = (char  *) ret;
  Lisp_Object iter;

  for (iter = data; CONSP (iter); iter = XCDR (iter))
    {
      Lisp_Object o = XCAR (iter);

      if (INTEGERP (o) || FLOATP (o) || CONSP (o))
	val = cons_to_signed (o, LONG_MIN, LONG_MAX);
      else if (STRINGP (o))
        {
          BLOCK_INPUT;
          val = (long) XInternAtom (dpy, SSDATA (o), False);
          UNBLOCK_INPUT;
        }
      else
        error ("Wrong type, must be string, number or cons");

      if (format == 8)
	{
	  if (CHAR_MIN <= val && val <= CHAR_MAX)
	    *d08++ = val;
	  else
	    error ("Out of 'char' range");
	}
      else if (format == 16)
	{
	  if (SHRT_MIN <= val && val <= SHRT_MAX)
	    *d16++ = val;
	  else
	    error ("Out of 'short' range");
	}
      else
        *d32++ = val;
    }
}

/* Convert an array of C values to a Lisp list.
   F is the frame to be used to look up X atoms if the TYPE is XA_ATOM.
   DATA is a C array of values to be converted.
   TYPE is the type of the data.  Only XA_ATOM is special, it converts
   each number in DATA to its corresponfing X atom as a symbol.
   FORMAT is 8, 16 or 32 and gives the size in bits for each C value to
   be stored in RET.
   SIZE is the number of elements in DATA.

   Important: When format is 32, data should contain an array of int,
   not an array of long as the X library returns.  This makes a difference
   when sizeof(long) != sizeof(int).

   Also see comment for selection_data_to_lisp_data above.  */

Lisp_Object
x_property_data_to_lisp (struct frame *f, const unsigned char *data,
			 Atom type, int format, long unsigned int size)
{
  ptrdiff_t format_bytes = format >> 3;
  if (PTRDIFF_MAX / format_bytes < size)
    memory_full (SIZE_MAX);
  return selection_data_to_lisp_data (FRAME_X_DISPLAY (f),
				      data, size * format_bytes, type, format);
}

/* Get the mouse position in frame relative coordinates.  */

static void
mouse_position_for_drop (FRAME_PTR f, int *x, int *y)
{
  Window root, dummy_window;
  int dummy;

  BLOCK_INPUT;

  XQueryPointer (FRAME_X_DISPLAY (f),
                 DefaultRootWindow (FRAME_X_DISPLAY (f)),

                 /* The root window which contains the pointer.  */
                 &root,

                 /* Window pointer is on, not used  */
                 &dummy_window,

                 /* The position on that root window.  */
                 x, y,

                 /* x/y in dummy_window coordinates, not used.  */
                 &dummy, &dummy,

                 /* Modifier keys and pointer buttons, about which
                    we don't care.  */
                 (unsigned int *) &dummy);


  /* Absolute to relative.  */
  *x -= f->left_pos + FRAME_OUTER_TO_INNER_DIFF_X (f);
  *y -= f->top_pos + FRAME_OUTER_TO_INNER_DIFF_Y (f);

  UNBLOCK_INPUT;
}

DEFUN ("x-get-atom-name", Fx_get_atom_name,
       Sx_get_atom_name, 1, 2, 0,
       doc: /* Return the X atom name for VALUE as a string.
VALUE may be a number or a cons where the car is the upper 16 bits and
the cdr is the lower 16 bits of a 32 bit value.
Use the display for FRAME or the current frame if FRAME is not given or nil.

If the value is 0 or the atom is not known, return the empty string.  */)
  (Lisp_Object value, Lisp_Object frame)
{
  struct frame *f = check_x_frame (frame);
  char *name = 0;
  char empty[] = "";
  Lisp_Object ret = Qnil;
  Display *dpy = FRAME_X_DISPLAY (f);
  Atom atom;
  int had_errors;

  CONS_TO_INTEGER (value, Atom, atom);

  BLOCK_INPUT;
  x_catch_errors (dpy);
  name = atom ? XGetAtomName (dpy, atom) : empty;
  had_errors = x_had_errors_p (dpy);
  x_uncatch_errors ();

  if (!had_errors)
    ret = build_string (name);

  if (atom && name) XFree (name);
  if (NILP (ret)) ret = empty_unibyte_string;

  UNBLOCK_INPUT;

  return ret;
}

DEFUN ("x-register-dnd-atom", Fx_register_dnd_atom,
       Sx_register_dnd_atom, 1, 2, 0,
       doc: /* Request that dnd events are made for ClientMessages with ATOM.
ATOM can be a symbol or a string.  The ATOM is interned on the display that
FRAME is on.  If FRAME is nil, the selected frame is used.  */)
  (Lisp_Object atom, Lisp_Object frame)
{
  Atom x_atom;
  struct frame *f = check_x_frame (frame);
  ptrdiff_t i;
  struct x_display_info *dpyinfo = FRAME_X_DISPLAY_INFO (f);


  if (SYMBOLP (atom))
    x_atom = symbol_to_x_atom (dpyinfo, atom);
  else if (STRINGP (atom))
    {
      BLOCK_INPUT;
      x_atom = XInternAtom (FRAME_X_DISPLAY (f), SSDATA (atom), False);
      UNBLOCK_INPUT;
    }
  else
    error ("ATOM must be a symbol or a string");

  for (i = 0; i < dpyinfo->x_dnd_atoms_length; ++i)
    if (dpyinfo->x_dnd_atoms[i] == x_atom)
      return Qnil;

  if (dpyinfo->x_dnd_atoms_length == dpyinfo->x_dnd_atoms_size)
    {
      if (min (PTRDIFF_MAX, SIZE_MAX) / sizeof *dpyinfo->x_dnd_atoms / 2
	  < dpyinfo->x_dnd_atoms_size)
	memory_full (SIZE_MAX);
      dpyinfo->x_dnd_atoms = xrealloc (dpyinfo->x_dnd_atoms,
				       (2 * sizeof *dpyinfo->x_dnd_atoms
					* dpyinfo->x_dnd_atoms_size));
      dpyinfo->x_dnd_atoms_size *= 2;
    }

  dpyinfo->x_dnd_atoms[dpyinfo->x_dnd_atoms_length++] = x_atom;
  return Qnil;
}

/* Convert an XClientMessageEvent to a Lisp event of type DRAG_N_DROP_EVENT.  */

int
x_handle_dnd_message (struct frame *f, XClientMessageEvent *event, struct x_display_info *dpyinfo, struct input_event *bufp)
{
  Lisp_Object vec;
  Lisp_Object frame;
  /* format 32 => size 5, format 16 => size 10, format 8 => size 20 */
  unsigned long size = 160/event->format;
  int x, y;
  unsigned char *data = (unsigned char *) event->data.b;
  int idata[5];
  ptrdiff_t i;

  for (i = 0; i < dpyinfo->x_dnd_atoms_length; ++i)
    if (dpyinfo->x_dnd_atoms[i] == event->message_type) break;

  if (i == dpyinfo->x_dnd_atoms_length) return 0;

  XSETFRAME (frame, f);

  /* On a 64 bit machine, the event->data.l array members are 64 bits (long),
     but the x_property_data_to_lisp (or rather selection_data_to_lisp_data)
     function expects them to be of size int (i.e. 32).  So to be able to
     use that function, put the data in the form it expects if format is 32. */

  if (32 < BITS_PER_LONG && event->format == 32)
    {
      for (i = 0; i < 5; ++i) /* There are only 5 longs in a ClientMessage. */
	idata[i] = event->data.l[i];
      data = (unsigned char *) idata;
    }

  vec = Fmake_vector (make_number (4), Qnil);
  ASET (vec, 0, SYMBOL_NAME (x_atom_to_symbol (FRAME_X_DISPLAY (f),
					       event->message_type)));
  ASET (vec, 1, frame);
  ASET (vec, 2, make_number (event->format));
  ASET (vec, 3, x_property_data_to_lisp (f,
					 data,
					 event->message_type,
					 event->format,
					 size));

  mouse_position_for_drop (f, &x, &y);
  bufp->kind = DRAG_N_DROP_EVENT;
  bufp->frame_or_window = frame;
  bufp->timestamp = CurrentTime;
  bufp->x = make_number (x);
  bufp->y = make_number (y);
  bufp->arg = vec;
  bufp->modifiers = 0;

  return 1;
}

DEFUN ("x-send-client-message", Fx_send_client_event,
       Sx_send_client_message, 6, 6, 0,
       doc: /* Send a client message of MESSAGE-TYPE to window DEST on DISPLAY.

For DISPLAY, specify either a frame or a display name (a string).
If DISPLAY is nil, that stands for the selected frame's display.
DEST may be a number, in which case it is a Window id.  The value 0 may
be used to send to the root window of the DISPLAY.
If DEST is a cons, it is converted to a 32 bit number
with the high 16 bits from the car and the lower 16 bit from the cdr.  That
number is then used as a window id.
If DEST is a frame the event is sent to the outer window of that frame.
A value of nil means the currently selected frame.
If DEST is the string "PointerWindow" the event is sent to the window that
contains the pointer.  If DEST is the string "InputFocus" the event is
sent to the window that has the input focus.
FROM is the frame sending the event.  Use nil for currently selected frame.
MESSAGE-TYPE is the name of an Atom as a string.
FORMAT must be one of 8, 16 or 32 and determines the size of the values in
bits.  VALUES is a list of numbers, cons and/or strings containing the values
to send.  If a value is a string, it is converted to an Atom and the value of
the Atom is sent.  If a value is a cons, it is converted to a 32 bit number
with the high 16 bits from the car and the lower 16 bit from the cdr.
If more values than fits into the event is given, the excessive values
are ignored.  */)
  (Lisp_Object display, Lisp_Object dest, Lisp_Object from, Lisp_Object message_type, Lisp_Object format, Lisp_Object values)
{
  struct x_display_info *dpyinfo = check_x_display_info (display);

  CHECK_STRING (message_type);
  x_send_client_event(display, dest, from,
                      XInternAtom (dpyinfo->display,
                                   SSDATA (message_type),
                                   False),
                      format, values);

  return Qnil;
}

void
x_send_client_event (Lisp_Object display, Lisp_Object dest, Lisp_Object from, Atom message_type, Lisp_Object format, Lisp_Object values)
{
  struct x_display_info *dpyinfo = check_x_display_info (display);
  Window wdest;
  XEvent event;
  struct frame *f = check_x_frame (from);
  int to_root;

  CHECK_NUMBER (format);
  CHECK_CONS (values);

  if (x_check_property_data (values) == -1)
    error ("Bad data in VALUES, must be number, cons or string");

  event.xclient.type = ClientMessage;
  event.xclient.format = XFASTINT (format);

  if (event.xclient.format != 8 && event.xclient.format != 16
      && event.xclient.format != 32)
    error ("FORMAT must be one of 8, 16 or 32");

  if (FRAMEP (dest) || NILP (dest))
    {
      struct frame *fdest = check_x_frame (dest);
      wdest = FRAME_OUTER_WINDOW (fdest);
    }
  else if (STRINGP (dest))
    {
      if (strcmp (SSDATA (dest), "PointerWindow") == 0)
        wdest = PointerWindow;
      else if (strcmp (SSDATA (dest), "InputFocus") == 0)
        wdest = InputFocus;
      else
        error ("DEST as a string must be one of PointerWindow or InputFocus");
    }
  else if (INTEGERP (dest) || FLOATP (dest) || CONSP (dest))
    CONS_TO_INTEGER (dest, Window, wdest);
  else
    error ("DEST must be a frame, nil, string, number or cons");

  if (wdest == 0) wdest = dpyinfo->root_window;
  to_root = wdest == dpyinfo->root_window;

  BLOCK_INPUT;

  event.xclient.message_type = message_type;
  event.xclient.display = dpyinfo->display;

  /* Some clients (metacity for example) expects sending window to be here
     when sending to the root window.  */
  event.xclient.window = to_root ? FRAME_OUTER_WINDOW (f) : wdest;


  memset (event.xclient.data.b, 0, sizeof (event.xclient.data.b));
  x_fill_property_data (dpyinfo->display, values, event.xclient.data.b,
                        event.xclient.format);

  /* If event mask is 0 the event is sent to the client that created
     the destination window.  But if we are sending to the root window,
     there is no such client.  Then we set the event mask to 0xffff.  The
     event then goes to clients selecting for events on the root window.  */
  x_catch_errors (dpyinfo->display);
  {
    int propagate = to_root ? False : True;
    unsigned mask = to_root ? 0xffff : 0;
    XSendEvent (dpyinfo->display, wdest, propagate, mask, &event);
    XFlush (dpyinfo->display);
  }
  x_uncatch_errors ();
  UNBLOCK_INPUT;
}

\f
void
syms_of_xselect (void)
{
  defsubr (&Sx_get_selection_internal);
  defsubr (&Sx_own_selection_internal);
  defsubr (&Sx_disown_selection_internal);
  defsubr (&Sx_selection_owner_p);
  defsubr (&Sx_selection_exists_p);

  defsubr (&Sx_get_atom_name);
  defsubr (&Sx_send_client_message);
  defsubr (&Sx_register_dnd_atom);

  reading_selection_reply = Fcons (Qnil, Qnil);
  staticpro (&reading_selection_reply);
  reading_selection_window = 0;
  reading_which_selection = 0;

  property_change_wait_list = 0;
  prop_location_identifier = 0;
  property_change_reply = Fcons (Qnil, Qnil);
  staticpro (&property_change_reply);

  converted_selections = NULL;
  conversion_fail_tag = None;

  DEFVAR_LISP ("selection-converter-alist", Vselection_converter_alist,
	       doc: /* An alist associating X Windows selection-types with functions.
These functions are called to convert the selection, with three args:
the name of the selection (typically `PRIMARY', `SECONDARY', or `CLIPBOARD');
a desired type to which the selection should be converted;
and the local selection value (whatever was given to `x-own-selection').

The function should return the value to send to the X server
\(typically a string).  A return value of nil
means that the conversion could not be done.
A return value which is the symbol `NULL'
means that a side-effect was executed,
and there is no meaningful selection value.  */);
  Vselection_converter_alist = Qnil;

  DEFVAR_LISP ("x-lost-selection-functions", Vx_lost_selection_functions,
	       doc: /* A list of functions to be called when Emacs loses an X selection.
\(This happens when some other X client makes its own selection
or when a Lisp program explicitly clears the selection.)
The functions are called with one argument, the selection type
\(a symbol, typically `PRIMARY', `SECONDARY', or `CLIPBOARD').  */);
  Vx_lost_selection_functions = Qnil;

  DEFVAR_LISP ("x-sent-selection-functions", Vx_sent_selection_functions,
	       doc: /* A list of functions to be called when Emacs answers a selection request.
The functions are called with three arguments:
  - the selection name (typically `PRIMARY', `SECONDARY', or `CLIPBOARD');
  - the selection-type which Emacs was asked to convert the
    selection into before sending (for example, `STRING' or `LENGTH');
  - a flag indicating success or failure for responding to the request.
We might have failed (and declined the request) for any number of reasons,
including being asked for a selection that we no longer own, or being asked
to convert into a type that we don't know about or that is inappropriate.
This hook doesn't let you change the behavior of Emacs's selection replies,
it merely informs you that they have happened.  */);
  Vx_sent_selection_functions = Qnil;

  DEFVAR_LISP ("x-select-enable-clipboard-manager",
	       Vx_select_enable_clipboard_manager,
	       doc: /* Whether to enable X clipboard manager support.
If non-nil, then whenever Emacs is killed or an Emacs frame is deleted
while owning the X clipboard, the clipboard contents are saved to the
clipboard manager if one is present.  */);
  Vx_select_enable_clipboard_manager = Qt;

  DEFVAR_INT ("x-selection-timeout", x_selection_timeout,
	      doc: /* Number of milliseconds to wait for a selection reply.
If the selection owner doesn't reply in this time, we give up.
A value of 0 means wait as long as necessary.  This is initialized from the
\"*selectionTimeout\" resource.  */);
  x_selection_timeout = 0;

  /* QPRIMARY is defined in keyboard.c.  */
  DEFSYM (QSECONDARY, "SECONDARY");
  DEFSYM (QSTRING, "STRING");
  DEFSYM (QINTEGER, "INTEGER");
  DEFSYM (QCLIPBOARD, "CLIPBOARD");
  DEFSYM (QTIMESTAMP, "TIMESTAMP");
  DEFSYM (QTEXT, "TEXT");
  DEFSYM (QCOMPOUND_TEXT, "COMPOUND_TEXT");
  DEFSYM (QUTF8_STRING, "UTF8_STRING");
  DEFSYM (QDELETE, "DELETE");
  DEFSYM (QMULTIPLE, "MULTIPLE");
  DEFSYM (QINCR, "INCR");
  DEFSYM (QEMACS_TMP, "_EMACS_TMP_");
  DEFSYM (QTARGETS, "TARGETS");
  DEFSYM (QATOM, "ATOM");
  DEFSYM (QATOM_PAIR, "ATOM_PAIR");
  DEFSYM (QCLIPBOARD_MANAGER, "CLIPBOARD_MANAGER");
  DEFSYM (QSAVE_TARGETS, "SAVE_TARGETS");
  DEFSYM (QNULL, "NULL");
  DEFSYM (Qcompound_text_with_extensions, "compound-text-with-extensions");
  DEFSYM (Qforeign_selection, "foreign-selection");
  DEFSYM (Qx_lost_selection_functions, "x-lost-selection-functions");
  DEFSYM (Qx_sent_selection_functions, "x-sent-selection-functions");
}