1 /* 16-bit Windows Selection processing for emacs on MS-Windows
  2    Copyright (C) 1996, 1997, 2001, 2002, 2003, 2004,
  3                  2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
  4 
  5 This file is part of GNU Emacs.
  6 
  7 GNU Emacs is free software: you can redistribute it and/or modify
  8 it under the terms of the GNU General Public License as published by
  9 the Free Software Foundation, either version 3 of the License, or
 10 (at your option) any later version.
 11 
 12 GNU Emacs is distributed in the hope that it will be useful,
 13 but WITHOUT ANY WARRANTY; without even the implied warranty of
 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15 GNU General Public License for more details.
 16 
 17 You should have received a copy of the GNU General Public License
 18 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 19 
 20 /* These functions work by using WinOldAp interface.  WinOldAp
 21    (WINOLDAP.MOD) is a Microsoft Windows extension supporting
 22    "old" (character-mode) application access to Dynamic Data Exchange,
 23    menus, and the Windows clipboard.  */
 24 
 25 /* Written by Dale P. Smith <dpsm@en.com>  */
 26 /* Adapted to DJGPP by Eli Zaretskii <eliz@gnu.org>  */
 27 
 28 #ifdef MSDOS
 29 
 30 #include <config.h>
 31 #include <string.h>
 32 #include <dpmi.h>
 33 #include <go32.h>
 34 #include <sys/farptr.h>
 35 #include <setjmp.h>
 36 #include "lisp.h"
 37 #include "dispextern.h" /* frame.h seems to want this */
 38 #include "frame.h"      /* Need this to get the X window of selected_frame */
 39 #include "blockinput.h"
 40 #include "buffer.h"
 41 #include "character.h"
 42 #include "coding.h"
 43 #include "composite.h"
 44 
 45 /* If ever some function outside this file will need to call any
 46    clipboard-related function, the following prototypes and constants
 47    should be put on a header file.  Right now, nobody else uses them.  */
 48 
 49 #define CF_TEXT      0x01
 50 #define CF_BITMAP    0x02
 51 #define CF_METAFILE  0x03
 52 #define CF_SYLK      0x04
 53 #define CF_DIF       0x05
 54 #define CF_TIFF      0x06
 55 #define CF_OEMTEXT   0x07
 56 #define CF_DIBBITMAP 0x08
 57 #define CF_WINWRITE  0x80
 58 #define CF_DSPTEXT   0x81
 59 #define CF_DSPBITMAP 0x82
 60 
 61 unsigned identify_winoldap_version (void);
 62 unsigned open_clipboard (void);
 63 unsigned empty_clipboard (void);
 64 unsigned set_clipboard_data (unsigned, void *, unsigned, int);
 65 unsigned get_clipboard_data_size (unsigned);
 66 unsigned get_clipboard_data (unsigned, void *, unsigned, int);
 67 unsigned close_clipboard (void);
 68 unsigned clipboard_compact (unsigned);
 69 
 70 Lisp_Object QCLIPBOARD, QPRIMARY;
 71 
 72 /* Coding system for communicating with other Windows programs via the
 73    clipboard.  */
 74 static Lisp_Object Vselection_coding_system;
 75 
 76 /* Coding system for the next communicating with other Windows programs.  */
 77 static Lisp_Object Vnext_selection_coding_system;
 78 
 79 /* The segment address and the size of the buffer in low
 80    memory used to move data between us and WinOldAp module.  */
 81 static struct {
 82   unsigned long size;
 83   unsigned short rm_segment;
 84 } clipboard_xfer_buf_info;
 85 
 86 /* The last text we put into the clipboard.  This is used to prevent
 87    passing back our own text from the clipboard, instead of using the
 88    kill ring.  The former is undesirable because the clipboard data
 89    could be MULEtilated by inappropriately chosen
 90    (next-)selection-coding-system.  For this reason, we must store the
 91    text *after* it was encoded/Unix-to-DOS-converted.  */
 92 static unsigned char *last_clipboard_text;
 93 
 94 /* The size of allocated storage for storing the clipboard data.  */
 95 static size_t clipboard_storage_size;
 96 
 97 /* C functions to access the Windows 3.1x clipboard from DOS apps.
 98 
 99    The information was obtained from the Microsoft Knowledge Base,
100    article Q67675 and can be found at:
101    http://www.microsoft.com/kb/developr/win_dk/q67675.htm  */
102 
103 /* See also Ralf Brown's Interrupt List.
104 
105    I also seem to remember reading about this in Dr. Dobbs Journal a
106    while ago, but if you knew my memory...  :-)
107 
108    Dale P. Smith <dpsm@en.com> */
109 
110 /* Return the WinOldAp support version, or 0x1700 if not supported.  */
111 unsigned
112 identify_winoldap_version ()
113 {
114   __dpmi_regs regs;
115 
116   /* Calls Int 2Fh/AX=1700h
117      Return Values   AX == 1700H: Clipboard functions not available
118                         <> 1700H: AL = Major version number
119                                   AH = Minor version number */
120   regs.x.ax = 0x1700;
121   __dpmi_int(0x2f, &regs);
122   return regs.x.ax;
123 }
124 
125 /* Open the clipboard, return non-zero if successfull.  */
126 unsigned
127 open_clipboard ()
128 {
129   __dpmi_regs regs;
130 
131   /* Is WINOLDAP supported?  */
132   /* Kludge alert!!  If WinOldAp is not supported, we return a 0,
133      which is the same as ``Clipboard already open''.  Currently,
134      this is taken as an error by all the functions that use
135      `open_clipboard', but if somebody someday will use that ``open''
136      clipboard, they will have interesting time debugging it...  */
137   if (identify_winoldap_version () == 0x1700)
138     return 0;
139 
140   /* Calls Int 2Fh/AX=1701h
141      Return Values   AX == 0: Clipboard already open
142                         <> 0: Clipboard opened */
143   regs.x.ax = 0x1701;
144   __dpmi_int(0x2f, &regs);
145   return regs.x.ax;
146 }
147 
148 /* Empty clipboard, return non-zero if successfull.  */
149 unsigned
150 empty_clipboard ()
151 {
152   __dpmi_regs regs;
153 
154   /* Calls Int 2Fh/AX=1702h
155      Return Values   AX == 0: Error occurred
156                         <> 0: OK, Clipboard emptied */
157   regs.x.ax = 0x1702;
158   __dpmi_int(0x2f, &regs);
159   return regs.x.ax;
160 }
161 
162 /* Ensure we have a buffer in low memory with enough memory for data
163    of size WANT_SIZE.  Return the linear address of the buffer.  */
164 static unsigned long
165 alloc_xfer_buf (want_size)
166      unsigned want_size;
167 {
168   __dpmi_regs regs;
169 
170   /* If the usual DJGPP transfer buffer is large enough, use that.  */
171   if (want_size <= _go32_info_block.size_of_transfer_buffer)
172     return __tb & 0xfffff;
173 
174   /* Don't even try to allocate more than 1MB of memory: DOS cannot
175      possibly handle that (it will overflow the BX register below).  */
176   if (want_size > 0xfffff)
177     return 0;
178 
179   /* Need size rounded up to the nearest paragraph, and in
180      paragraph units (1 paragraph = 16 bytes).  */
181   clipboard_xfer_buf_info.size = (want_size + 15) >> 4;
182 
183   /* The NT DPMI host crashes us if we free DOS memory via the
184      DPMI service.  Work around by calling DOS allocate/free block.  */
185   regs.h.ah = 0x48;
186   regs.x.bx = clipboard_xfer_buf_info.size;
187   __dpmi_int (0x21, &regs);
188   if (regs.x.flags & 1)
189     {
190       clipboard_xfer_buf_info.size = 0;
191       return 0;
192     }
193 
194   clipboard_xfer_buf_info.rm_segment = regs.x.ax;
195   return (((int)clipboard_xfer_buf_info.rm_segment) << 4) & 0xfffff;
196 }
197 
198 /* Free our clipboard buffer.  We always free it after use, because
199    keeping it leaves less free conventional memory for subprocesses.
200    The clipboard buffer tends to be large in size, because for small
201    clipboard data sizes we use the DJGPP transfer buffer.  */
202 static void
203 free_xfer_buf ()
204 {
205   /* If the size is 0, we used DJGPP transfer buffer, so don't free.  */
206   if (clipboard_xfer_buf_info.size)
207     {
208       __dpmi_regs regs;
209 
210       /* The NT DPMI host crashes us if we free DOS memory via
211          the DPMI service.  Work around by calling DOS free block.  */
212       regs.h.ah = 0x49;
213       regs.x.es = clipboard_xfer_buf_info.rm_segment;
214       __dpmi_int (0x21, &regs);
215       clipboard_xfer_buf_info.size = 0;
216     }
217 }
218 
219 /* Copy data into the clipboard, return zero if successfull.  */
220 unsigned
221 set_clipboard_data (Format, Data, Size, Raw)
222      unsigned Format;
223      void *Data;
224      unsigned Size;
225      int Raw;
226 {
227   __dpmi_regs regs;
228   unsigned truelen;
229   unsigned long xbuf_addr, buf_offset;
230   unsigned char *dp = Data, *dstart = dp;
231 
232   if (Format != CF_OEMTEXT)
233     return 3;
234 
235   /* need to know final size after '\r' chars are inserted (the
236      standard CF_OEMTEXT clipboard format uses CRLF line endings,
237      while Emacs uses just LF internally).  */
238   truelen = Size + 1;           /* +1 for the terminating null */
239 
240   if (!Raw)
241     {
242       /* avoid using strchr because it recomputes the length everytime */
243       while ((dp = memchr (dp, '\n', Size - (dp - dstart))) != 0)
244         {
245           truelen++;
246           dp++;
247         }
248     }
249 
250   if (clipboard_compact (truelen) < truelen)
251     return 1;
252 
253   if ((xbuf_addr = alloc_xfer_buf (truelen)) == 0)
254     return 1;
255 
256   /* Move the buffer into the low memory, convert LF into CR-LF if needed.  */
257   if (Raw)
258     {
259       dosmemput (Data, Size, xbuf_addr);
260 
261       /* Terminate with a null, otherwise Windows does strange things
262          when the text size is an integral multiple of 32 bytes. */
263       _farpokeb (_dos_ds, xbuf_addr + Size, '\0');
264     }
265   else
266     {
267       dp = Data;
268       buf_offset = xbuf_addr;
269       _farsetsel (_dos_ds);
270       while (Size--)
271         {
272           /* Don't allow them to put binary data into the clipboard, since
273              it will cause yanked data to be truncated at the first null.  */
274           if (*dp == '\0')
275             return 2;
276           if (*dp == '\n')
277             _farnspokeb (buf_offset++, '\r');
278           _farnspokeb (buf_offset++, *dp++);
279         }
280 
281       /* Terminate with a null, otherwise Windows does strange things
282          when the text size is an integral multiple of 32 bytes. */
283       _farnspokeb (buf_offset, '\0');
284     }
285 
286   /* Stash away the data we are about to put into the clipboard, so we
287      could later check inside get_clipboard_data whether the clipboard
288      still holds our data.  */
289   if (clipboard_storage_size < truelen)
290     {
291       clipboard_storage_size = truelen + 100;
292       last_clipboard_text =
293         (char *) xrealloc (last_clipboard_text, clipboard_storage_size);
294     }
295   if (last_clipboard_text)
296     dosmemget (xbuf_addr, truelen, last_clipboard_text);
297 
298   /* Calls Int 2Fh/AX=1703h with:
299                      DX = WinOldAp-Supported Clipboard format
300                      ES:BX = Pointer to data
301                      SI:CX = Size of data in bytes
302      Return Values   AX == 0: Error occurred
303                         <> 0: OK.  Data copied into the Clipboard.  */
304   regs.x.ax = 0x1703;
305   regs.x.dx = Format;
306   regs.x.si = truelen >> 16;
307   regs.x.cx = truelen & 0xffff;
308   regs.x.es = xbuf_addr >> 4;
309   regs.x.bx = xbuf_addr & 15;
310   __dpmi_int(0x2f, &regs);
311 
312   free_xfer_buf ();
313 
314   /* If the above failed, invalidate the local copy of the clipboard.  */
315   if (regs.x.ax == 0)
316     *last_clipboard_text = '\0';
317 
318   /* Zero means success, otherwise (1, 2, or 3) it's an error.  */
319   return regs.x.ax > 0 ? 0 : 3;
320 }
321 
322 /* Return the size of the clipboard data of format FORMAT.  */
323 unsigned
324 get_clipboard_data_size (Format)
325      unsigned Format;
326 {
327   __dpmi_regs regs;
328 
329   /* Calls Int 2Fh/AX=1704h with:
330                      DX = WinOldAp-Supported Clipboard format
331      Return Values   DX:AX == Size of the data in bytes, including any
332                               headers.
333                            == 0 If data in this format is not in
334                            the clipboard.  */
335   regs.x.ax = 0x1704;
336   regs.x.dx = Format;
337   __dpmi_int(0x2f, &regs);
338   return ( (((unsigned)regs.x.dx) << 16) | regs.x.ax);
339 }
340 
341 /* Get clipboard data, return its length.
342    Warning: this doesn't check whether DATA has enough space to hold
343    SIZE bytes.  */
344 unsigned
345 get_clipboard_data (Format, Data, Size, Raw)
346      unsigned Format;
347      void *Data;
348      unsigned Size;
349      int Raw;
350 {
351   __dpmi_regs regs;
352   unsigned long xbuf_addr;
353   unsigned char *dp = Data;
354 
355   if (Format != CF_OEMTEXT)
356     return 0;
357 
358   if (Size == 0)
359     return 0;
360 
361   if ((xbuf_addr = alloc_xfer_buf (Size)) == 0)
362     return 0;
363 
364   /* Calls Int 2Fh/AX=1705h with:
365                      DX = WinOldAp-Supported Clipboard format
366                      ES:BX = Pointer to data buffer to hold data
367      Return Values   AX == 0: Error occurred (or data in this format is not
368                               in the clipboard)
369                         <> 0: OK  */
370   regs.x.ax = 0x1705;
371   regs.x.dx = Format;
372   regs.x.es = xbuf_addr >> 4;
373   regs.x.bx = xbuf_addr & 15;
374   __dpmi_int(0x2f, &regs);
375   if (regs.x.ax != 0)
376     {
377       unsigned char null_char = '\0';
378       unsigned long xbuf_beg = xbuf_addr;
379 
380       /* If last_clipboard_text is NULL, we don't want to slow down
381          the next loop by an additional test.  */
382       register unsigned char *lcdp =
383         last_clipboard_text == NULL ? &null_char : last_clipboard_text;
384 
385       /* Copy data from low memory, remove CR
386          characters before LF if needed.  */
387       _farsetsel (_dos_ds);
388       while (Size--)
389         {
390           register unsigned char c = _farnspeekb (xbuf_addr++);
391 
392           if (*lcdp == c)
393             lcdp++;
394 
395           if ((*dp++ = c) == '\r' && !Raw && _farnspeekb (xbuf_addr) == '\n')
396             {
397               dp--;
398               *dp++ = '\n';
399               xbuf_addr++;
400               if (*lcdp == '\n')
401                 lcdp++;
402             }
403           /* Windows reportedly rounds up the size of clipboard data
404              (passed in SIZE) to a multiple of 32, and removes trailing
405              spaces from each line without updating SIZE.  We therefore
406              bail out when we see the first null character.  */
407           else if (c == '\0')
408             break;
409         }
410 
411       /* If the text in clipboard is identical to what we put there
412          last time set_clipboard_data was called, pretend there's no
413          data in the clipboard.  This is so we don't pass our own text
414          from the clipboard (which might be troublesome if the killed
415          text includes null characters).  */
416       if (last_clipboard_text &&
417           xbuf_addr - xbuf_beg == (long)(lcdp - last_clipboard_text))
418         dp = (unsigned char *)Data + 1;
419     }
420 
421   free_xfer_buf ();
422 
423   return (unsigned) (dp - (unsigned char *)Data - 1);
424 }
425 
426 /* Close clipboard, return non-zero if successfull.  */
427 unsigned
428 close_clipboard ()
429 {
430   __dpmi_regs regs;
431 
432   /* Calls Int 2Fh/AX=1708h
433      Return Values   AX == 0: Error occurred
434                         <> 0: OK */
435   regs.x.ax = 0x1708;
436   __dpmi_int(0x2f, &regs);
437   return regs.x.ax;
438 }
439 
440 /* Compact clipboard data so that at least SIZE bytes is available.  */
441 unsigned
442 clipboard_compact (Size)
443      unsigned Size;
444 {
445   __dpmi_regs regs;
446 
447   /* Calls Int 2Fh/AX=1709H with:
448                      SI:CX = Desired memory size in bytes.
449      Return Values   DX:AX == Number of bytes of largest block of free memory.
450                            == 0 if error or no memory  */
451   regs.x.ax = 0x1709;
452   regs.x.si = Size >> 16;
453   regs.x.cx = Size & 0xffff;
454   __dpmi_int(0x2f, &regs);
455   return ((unsigned)regs.x.dx << 16) | regs.x.ax;
456 }
457 
458 static char no_mem_msg[] =
459   "(Not enough DOS memory to put saved text into clipboard.)";
460 static char binary_msg[] =
461   "(Binary characters in saved text; clipboard data not set.)";
462 static char system_error_msg[] =
463   "(Clipboard interface failure; clipboard data not set.)";
464 
465 DEFUN ("w16-set-clipboard-data", Fw16_set_clipboard_data, Sw16_set_clipboard_data, 1, 2, 0,
466        doc: /* This sets the clipboard data to the given text.  */)
467      (string, frame)
468      Lisp_Object string, frame;
469 {
470   unsigned ok = 1, put_status = 0;
471   int nbytes, charset_info, no_crlf_conversion;
472   unsigned char *src, *dst = NULL;
473 
474   CHECK_STRING (string);
475 
476   if (NILP (frame))
477     frame = Fselected_frame ();
478 
479   CHECK_LIVE_FRAME (frame);
480   if ( !FRAME_MSDOS_P (XFRAME (frame)))
481     goto done;
482 
483   BLOCK_INPUT;
484 
485   if (!open_clipboard ())
486     goto error;
487 
488   nbytes = SBYTES (string);
489   src = SDATA (string);
490 
491   /* Do we need to encode this text?  */
492   for (dst = src; dst < src + nbytes; dst++)
493     {
494       if (*dst == '\0' || *dst >= 0x80)
495         break;
496     }
497   if (dst >= src + nbytes)
498     {
499       /* No multibyte characters in text.  We need not encode it, but we
500          will have to convert it to DOS CR-LF style.  */
501       no_crlf_conversion = 0;
502       Vlast_coding_system_used = Qraw_text;
503       dst = NULL;       /* so we don't try to free a random pointer */
504     }
505   else
506     {
507       /* We must encode contents of STRING according to what
508          clipboard-coding-system specifies.  */
509       int bufsize;
510       struct coding_system coding;
511       unsigned char *htext2;
512       Lisp_Object coding_system =
513         NILP (Vnext_selection_coding_system) ?
514         Vselection_coding_system : Vnext_selection_coding_system;
515 
516       setup_coding_system (Fcheck_coding_system (coding_system), &coding);
517       coding.dst_bytes = nbytes * 4;
518       coding.destination = (unsigned char *) xmalloc (coding.dst_bytes);
519       Vnext_selection_coding_system = Qnil;
520       coding.mode |= CODING_MODE_LAST_BLOCK;
521       dst = coding.destination;
522       encode_coding_object (&coding, string, 0, 0,
523                             SCHARS (string), nbytes, Qnil);
524       no_crlf_conversion = 1;
525       nbytes = coding.produced;
526       Vlast_coding_system_used = CODING_ID_NAME (coding.id);
527       src = dst;
528     }
529 
530   ok = empty_clipboard ()
531     && ((put_status
532          = set_clipboard_data (CF_OEMTEXT, src, nbytes, no_crlf_conversion))
533         == 0);
534 
535   if (!no_crlf_conversion)
536   close_clipboard ();
537 
538   if (ok) goto unblock;
539 
540  error:
541 
542   ok = 0;
543 
544  unblock:
545   xfree (dst);
546   UNBLOCK_INPUT;
547 
548   /* Notify user if the text is too large to fit into DOS memory.
549      (This will happen somewhere after 600K bytes (470K in DJGPP v1.x),
550      depending on user system configuration.)  If we just silently
551      fail the function, people might wonder why their text sometimes
552      doesn't make it to the clipboard.  */
553   if (put_status)
554     {
555       switch (put_status)
556         {
557           case 1:
558             message2 (no_mem_msg, sizeof (no_mem_msg) - 1, 0);
559             break;
560           case 2:
561             message2 (binary_msg, sizeof (binary_msg) - 1, 0);
562             break;
563           case 3:
564             message2 (system_error_msg, sizeof (system_error_msg) - 1, 0);
565             break;
566         }
567       sit_for (make_number (2), 0, 2);
568     }
569 
570  done:
571 
572   return (ok && put_status == 0 ? string : Qnil);
573 }
574 
575 DEFUN ("w16-get-clipboard-data", Fw16_get_clipboard_data, Sw16_get_clipboard_data, 0, 1, 0,
576        doc: /* This gets the clipboard data in text format.  */)
577      (frame)
578      Lisp_Object frame;
579 {
580   unsigned data_size, truelen;
581   unsigned char *htext = NULL;
582   Lisp_Object ret = Qnil;
583   int no_crlf_conversion, require_decoding = 0;
584 
585   if (NILP (frame))
586     frame = Fselected_frame ();
587 
588   CHECK_LIVE_FRAME (frame);
589   if ( !FRAME_MSDOS_P (XFRAME (frame)))
590     goto done;
591 
592   BLOCK_INPUT;
593 
594   if (!open_clipboard ())
595     goto unblock;
596 
597   if ((data_size = get_clipboard_data_size (CF_OEMTEXT)) == 0 ||
598       (htext = (unsigned char *)xmalloc (data_size)) == 0)
599     goto closeclip;
600 
601   /* need to know final size after '\r' chars are removed because
602      we can't change the string size manually, and doing an extra
603      copy is silly */
604   if ((truelen = get_clipboard_data (CF_OEMTEXT, htext, data_size, 0)) == 0)
605     goto closeclip;
606 
607   /* Do we need to decode it?  */
608   {
609     /* If the clipboard data contains any 8-bit Latin-1 code, we
610        need to decode it.  */
611     int i;
612 
613     for (i = 0; i < truelen; i++)
614       {
615         if (htext[i] >= 0x80)
616           {
617             require_decoding = 1;
618             break;
619           }
620       }
621   }
622   if (require_decoding)
623     {
624       int bufsize;
625       unsigned char *buf;
626       struct coding_system coding;
627       Lisp_Object coding_system = Vnext_selection_coding_system;
628 
629       truelen = get_clipboard_data (CF_OEMTEXT, htext, data_size, 1);
630       if (NILP (coding_system))
631         coding_system = Vselection_coding_system;
632       setup_coding_system (Fcheck_coding_system (coding_system), &coding);
633       coding.source = htext;
634       coding.mode |= CODING_MODE_LAST_BLOCK;
635       /* We explicitly disable composition handling because selection
636          data should not contain any composition sequence.  */
637       coding.mode &= CODING_ANNOTATION_MASK;
638       decode_coding_object (&coding, Qnil, 0, 0, truelen, truelen, Qt);
639       ret = coding.dst_object;
640       Vlast_coding_system_used = CODING_ID_NAME (coding.id);
641     }
642   else
643     {
644       ret = make_unibyte_string ((char *) htext, truelen);
645       Vlast_coding_system_used = Qraw_text;
646     }
647 
648   xfree (htext);
649   Vnext_selection_coding_system = Qnil;
650 
651  closeclip:
652   close_clipboard ();
653 
654  unblock:
655   UNBLOCK_INPUT;
656 
657  done:
658 
659   return (ret);
660 }
661 
662 /* Support checking for a clipboard selection. */
663 
664 DEFUN ("x-selection-exists-p", Fx_selection_exists_p, Sx_selection_exists_p,
665        0, 1, 0,
666        doc: /* Whether there is an owner for the given X Selection.
667 The arg should be the name of the selection in question, typically one of
668 the symbols `PRIMARY', `SECONDARY', or `CLIPBOARD'.
669 \(Those are literal upper-case symbol names, since that's what X expects.)
670 For convenience, the symbol nil is the same as `PRIMARY',
671 and t is the same as `SECONDARY'.  */)
672      (selection)
673      Lisp_Object selection;
674 {
675   CHECK_SYMBOL (selection);
676 
677   /* Return nil for SECONDARY selection.  For PRIMARY (or nil)
678      selection, check if there is some text on the kill-ring;
679      for CLIPBOARD, check if the clipboard currently has valid
680      text format contents.
681 
682      The test for killed text on the kill-ring emulates the Emacs
683      behavior on X, where killed text is also put into X selection
684      by the X interface code.  (On MSDOS, killed text is only put
685      into the clipboard if we run under Windows, so we cannot check
686      the clipboard alone.)  */
687   if ((EQ (selection, Qnil) || EQ (selection, QPRIMARY))
688       && ! NILP (Fsymbol_value (Fintern_soft (build_string ("kill-ring"),
689                                               Qnil))))
690     return Qt;
691 
692   if (EQ (selection, QCLIPBOARD))
693     {
694       Lisp_Object val = Qnil;
695 
696       if (open_clipboard ())
697         {
698           if (get_clipboard_data_size (CF_OEMTEXT))
699             val = Qt;
700           close_clipboard ();
701         }
702       return val;
703     }
704   return Qnil;
705 }
706 
707 void
708 syms_of_win16select ()
709 {
710   defsubr (&Sw16_set_clipboard_data);
711   defsubr (&Sw16_get_clipboard_data);
712   defsubr (&Sx_selection_exists_p);
713 
714   DEFVAR_LISP ("selection-coding-system", &Vselection_coding_system,
715                doc: /* Coding system for communicating with other X clients.
716 When sending or receiving text via cut_buffer, selection, and clipboard,
717 the text is encoded or decoded by this coding system.
718 The default value is `iso-latin-1-dos'.  */);
719   Vselection_coding_system = intern ("iso-latin-1-dos");
720 
721   DEFVAR_LISP ("next-selection-coding-system", &Vnext_selection_coding_system,
722                doc: /* Coding system for the next communication with other X clients.
723 Usually, `selection-coding-system' is used for communicating with
724 other X clients.  But, if this variable is set, it is used for the
725 next communication only.  After the communication, this variable is
726 set to nil.  */);
727   Vnext_selection_coding_system = Qnil;
728 
729   QPRIMARY   = intern ("PRIMARY");      staticpro (&QPRIMARY);
730   QCLIPBOARD = intern ("CLIPBOARD");    staticpro (&QCLIPBOARD);
731 }
732 
733 #endif /* MSDOS */
734 
735 /* arch-tag: 085a22c8-7324-436e-a6da-102464ce95d8
736    (do not change this comment) */