src/w16select.c

   1 /* 16-bit Windows Selection processing for emacs on MS-Windows
   2
   3 Copyright (C) 1996-1997, 2001-2011  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 <dpmi.h>
  32 #include <go32.h>
  33 #include <sys/farptr.h>
  34 #include <setjmp.h>
  35 #include "lisp.h"
  36 #include "dispextern.h" /* frame.h seems to want this */
  37 #include "frame.h"      /* Need this to get the X window of selected_frame */
  38 #include "blockinput.h"
  39 #include "buffer.h"
  40 #include "character.h"
  41 #include "coding.h"
  42 #include "composite.h"
  43
  44 /* If ever some function outside this file will need to call any
  45    clipboard-related function, the following prototypes and constants
  46    should be put on a header file.  Right now, nobody else uses them.  */
  47
  48 #define CF_TEXT      0x01
  49 #define CF_BITMAP    0x02
  50 #define CF_METAFILE  0x03
  51 #define CF_SYLK      0x04
  52 #define CF_DIF       0x05
  53 #define CF_TIFF      0x06
  54 #define CF_OEMTEXT   0x07
  55 #define CF_DIBBITMAP 0x08
  56 #define CF_WINWRITE  0x80
  57 #define CF_DSPTEXT   0x81
  58 #define CF_DSPBITMAP 0x82
  59
  60 unsigned identify_winoldap_version (void);
  61 unsigned open_clipboard (void);
  62 unsigned empty_clipboard (void);
  63 unsigned set_clipboard_data (unsigned, void *, unsigned, int);
  64 unsigned get_clipboard_data_size (unsigned);
  65 unsigned get_clipboard_data (unsigned, void *, unsigned, int);
  66 unsigned close_clipboard (void);
  67 unsigned clipboard_compact (unsigned);
  68
  69 Lisp_Object QCLIPBOARD, QPRIMARY;
  70
  71 /* The segment address and the size of the buffer in low
  72    memory used to move data between us and WinOldAp module.  */
  73 static struct {
  74   unsigned long size;
  75   unsigned short rm_segment;
  76 } clipboard_xfer_buf_info;
  77
  78 /* The last text we put into the clipboard.  This is used to prevent
  79    passing back our own text from the clipboard, instead of using the
  80    kill ring.  The former is undesirable because the clipboard data
  81    could be MULEtilated by inappropriately chosen
  82    (next-)selection-coding-system.  For this reason, we must store the
  83    text *after* it was encoded/Unix-to-DOS-converted.  */
  84 static unsigned char *last_clipboard_text;
  85
  86 /* The size of allocated storage for storing the clipboard data.  */
  87 static size_t clipboard_storage_size;
  88 \f
  89 /* C functions to access the Windows 3.1x clipboard from DOS apps.
  90
  91    The information was obtained from the Microsoft Knowledge Base,
  92    article Q67675 and can be found at:
  93    http://www.microsoft.com/kb/developr/win_dk/q67675.htm  */
  94
  95 /* See also Ralf Brown's Interrupt List.
  96
  97    I also seem to remember reading about this in Dr. Dobbs Journal a
  98    while ago, but if you knew my memory...  :-)
  99
 100    Dale P. Smith <dpsm@en.com> */
 101
 102 /* Return the WinOldAp support version, or 0x1700 if not supported.  */
 103 unsigned
 104 identify_winoldap_version (void)
 105 {
 106   __dpmi_regs regs;
 107
 108   /* Calls Int 2Fh/AX=1700h
 109      Return Values   AX == 1700H: Clipboard functions not available
 110                         <> 1700H: AL = Major version number
 111                                   AH = Minor version number */
 112   regs.x.ax = 0x1700;
 113   __dpmi_int(0x2f, &regs);
 114   return regs.x.ax;
 115 }
 116
 117 /* Open the clipboard, return non-zero if successfull.  */
 118 unsigned
 119 open_clipboard (void)
 120 {
 121   __dpmi_regs regs;
 122
 123   /* Is WINOLDAP supported?  */
 124   /* Kludge alert!!  If WinOldAp is not supported, we return a 0,
 125      which is the same as ``Clipboard already open''.  Currently,
 126      this is taken as an error by all the functions that use
 127      `open_clipboard', but if somebody someday will use that ``open''
 128      clipboard, they will have interesting time debugging it...  */
 129   if (identify_winoldap_version () == 0x1700)
 130     return 0;
 131
 132   /* Calls Int 2Fh/AX=1701h
 133      Return Values   AX == 0: Clipboard already open
 134                         <> 0: Clipboard opened */
 135   regs.x.ax = 0x1701;
 136   __dpmi_int(0x2f, &regs);
 137   return regs.x.ax;
 138 }
 139
 140 /* Empty clipboard, return non-zero if successfull.  */
 141 unsigned
 142 empty_clipboard (void)
 143 {
 144   __dpmi_regs regs;
 145
 146   /* Calls Int 2Fh/AX=1702h
 147      Return Values   AX == 0: Error occurred
 148                         <> 0: OK, Clipboard emptied */
 149   regs.x.ax = 0x1702;
 150   __dpmi_int(0x2f, &regs);
 151   return regs.x.ax;
 152 }
 153
 154 /* Ensure we have a buffer in low memory with enough memory for data
 155    of size WANT_SIZE.  Return the linear address of the buffer.  */
 156 static unsigned long
 157 alloc_xfer_buf (unsigned want_size)
 158 {
 159   __dpmi_regs regs;
 160
 161   /* If the usual DJGPP transfer buffer is large enough, use that.  */
 162   if (want_size <= _go32_info_block.size_of_transfer_buffer)
 163     return __tb & 0xfffff;
 164
 165   /* Don't even try to allocate more than 1MB of memory: DOS cannot
 166      possibly handle that (it will overflow the BX register below).  */
 167   if (want_size > 0xfffff)
 168     return 0;
 169
 170   /* Need size rounded up to the nearest paragraph, and in
 171      paragraph units (1 paragraph = 16 bytes).  */
 172   clipboard_xfer_buf_info.size = (want_size + 15) >> 4;
 173
 174   /* The NT DPMI host crashes us if we free DOS memory via the
 175      DPMI service.  Work around by calling DOS allocate/free block.  */
 176   regs.h.ah = 0x48;
 177   regs.x.bx = clipboard_xfer_buf_info.size;
 178   __dpmi_int (0x21, &regs);
 179   if (regs.x.flags & 1)
 180     {
 181       clipboard_xfer_buf_info.size = 0;
 182       return 0;
 183     }
 184
 185   clipboard_xfer_buf_info.rm_segment = regs.x.ax;
 186   return (((int)clipboard_xfer_buf_info.rm_segment) << 4) & 0xfffff;
 187 }
 188
 189 /* Free our clipboard buffer.  We always free it after use, because
 190    keeping it leaves less free conventional memory for subprocesses.
 191    The clipboard buffer tends to be large in size, because for small
 192    clipboard data sizes we use the DJGPP transfer buffer.  */
 193 static void
 194 free_xfer_buf (void)
 195 {
 196   /* If the size is 0, we used DJGPP transfer buffer, so don't free.  */
 197   if (clipboard_xfer_buf_info.size)
 198     {
 199       __dpmi_regs regs;
 200
 201       /* The NT DPMI host crashes us if we free DOS memory via
 202          the DPMI service.  Work around by calling DOS free block.  */
 203       regs.h.ah = 0x49;
 204       regs.x.es = clipboard_xfer_buf_info.rm_segment;
 205       __dpmi_int (0x21, &regs);
 206       clipboard_xfer_buf_info.size = 0;
 207     }
 208 }
 209
 210 /* Copy data into the clipboard, return zero if successfull.  */
 211 unsigned
 212 set_clipboard_data (unsigned Format, void *Data, unsigned Size, int Raw)
 213 {
 214   __dpmi_regs regs;
 215   unsigned truelen;
 216   unsigned long xbuf_addr, buf_offset;
 217   unsigned char *dp = Data, *dstart = dp;
 218
 219   if (Format != CF_OEMTEXT)
 220     return 3;
 221
 222   /* need to know final size after '\r' chars are inserted (the
 223      standard CF_OEMTEXT clipboard format uses CRLF line endings,
 224      while Emacs uses just LF internally).  */
 225   truelen = Size + 1;           /* +1 for the terminating null */
 226
 227   if (!Raw)
 228     {
 229       /* avoid using strchr because it recomputes the length everytime */
 230       while ((dp = memchr (dp, '\n', Size - (dp - dstart))) != 0)
 231         {
 232           truelen++;
 233           dp++;
 234         }
 235     }
 236
 237   if (clipboard_compact (truelen) < truelen)
 238     return 1;
 239
 240   if ((xbuf_addr = alloc_xfer_buf (truelen)) == 0)
 241     return 1;
 242
 243   /* Move the buffer into the low memory, convert LF into CR-LF if needed.  */
 244   if (Raw)
 245     {
 246       dosmemput (Data, Size, xbuf_addr);
 247
 248       /* Terminate with a null, otherwise Windows does strange things
 249          when the text size is an integral multiple of 32 bytes. */
 250       _farpokeb (_dos_ds, xbuf_addr + Size, '\0');
 251     }
 252   else
 253     {
 254       dp = Data;
 255       buf_offset = xbuf_addr;
 256       _farsetsel (_dos_ds);
 257       while (Size--)
 258         {
 259           /* Don't allow them to put binary data into the clipboard, since
 260              it will cause yanked data to be truncated at the first null.  */
 261           if (*dp == '\0')
 262             return 2;
 263           if (*dp == '\n')
 264             _farnspokeb (buf_offset++, '\r');
 265           _farnspokeb (buf_offset++, *dp++);
 266         }
 267
 268       /* Terminate with a null, otherwise Windows does strange things
 269          when the text size is an integral multiple of 32 bytes. */
 270       _farnspokeb (buf_offset, '\0');
 271     }
 272
 273   /* Stash away the data we are about to put into the clipboard, so we
 274      could later check inside get_clipboard_data whether the clipboard
 275      still holds our data.  */
 276   if (clipboard_storage_size < truelen)
 277     {
 278       clipboard_storage_size = truelen + 100;
 279       last_clipboard_text =
 280         (char *) xrealloc (last_clipboard_text, clipboard_storage_size);
 281     }
 282   if (last_clipboard_text)
 283     dosmemget (xbuf_addr, truelen, last_clipboard_text);
 284
 285   /* Calls Int 2Fh/AX=1703h with:
 286                      DX = WinOldAp-Supported Clipboard format
 287                      ES:BX = Pointer to data
 288                      SI:CX = Size of data in bytes
 289      Return Values   AX == 0: Error occurred
 290                         <> 0: OK.  Data copied into the Clipboard.  */
 291   regs.x.ax = 0x1703;
 292   regs.x.dx = Format;
 293   regs.x.si = truelen >> 16;
 294   regs.x.cx = truelen & 0xffff;
 295   regs.x.es = xbuf_addr >> 4;
 296   regs.x.bx = xbuf_addr & 15;
 297   __dpmi_int(0x2f, &regs);
 298
 299   free_xfer_buf ();
 300
 301   /* If the above failed, invalidate the local copy of the clipboard.  */
 302   if (regs.x.ax == 0)
 303     *last_clipboard_text = '\0';
 304
 305   /* Zero means success, otherwise (1, 2, or 3) it's an error.  */
 306   return regs.x.ax > 0 ? 0 : 3;
 307 }
 308
 309 /* Return the size of the clipboard data of format FORMAT.  */
 310 unsigned
 311 get_clipboard_data_size (unsigned Format)
 312 {
 313   __dpmi_regs regs;
 314
 315   /* Calls Int 2Fh/AX=1704h with:
 316                      DX = WinOldAp-Supported Clipboard format
 317      Return Values   DX:AX == Size of the data in bytes, including any
 318                               headers.
 319                            == 0 If data in this format is not in
 320                            the clipboard.  */
 321   regs.x.ax = 0x1704;
 322   regs.x.dx = Format;
 323   __dpmi_int(0x2f, &regs);
 324   return ( (((unsigned)regs.x.dx) << 16) | regs.x.ax);
 325 }
 326
 327 /* Get clipboard data, return its length.
 328    Warning: this doesn't check whether DATA has enough space to hold
 329    SIZE bytes.  */
 330 unsigned
 331 get_clipboard_data (unsigned Format, void *Data, unsigned Size, int Raw)
 332 {
 333   __dpmi_regs regs;
 334   unsigned long xbuf_addr;
 335   unsigned char *dp = Data;
 336
 337   if (Format != CF_OEMTEXT)
 338     return 0;
 339
 340   if (Size == 0)
 341     return 0;
 342
 343   if ((xbuf_addr = alloc_xfer_buf (Size)) == 0)
 344     return 0;
 345
 346   /* Calls Int 2Fh/AX=1705h with:
 347                      DX = WinOldAp-Supported Clipboard format
 348                      ES:BX = Pointer to data buffer to hold data
 349      Return Values   AX == 0: Error occurred (or data in this format is not
 350                               in the clipboard)
 351                         <> 0: OK  */
 352   regs.x.ax = 0x1705;
 353   regs.x.dx = Format;
 354   regs.x.es = xbuf_addr >> 4;
 355   regs.x.bx = xbuf_addr & 15;
 356   __dpmi_int(0x2f, &regs);
 357   if (regs.x.ax != 0)
 358     {
 359       unsigned char null_char = '\0';
 360       unsigned long xbuf_beg = xbuf_addr;
 361
 362       /* If last_clipboard_text is NULL, we don't want to slow down
 363          the next loop by an additional test.  */
 364       register unsigned char *lcdp =
 365         last_clipboard_text == NULL ? &null_char : last_clipboard_text;
 366
 367       /* Copy data from low memory, remove CR
 368          characters before LF if needed.  */
 369       _farsetsel (_dos_ds);
 370       while (Size--)
 371         {
 372           register unsigned char c = _farnspeekb (xbuf_addr++);
 373
 374           if (*lcdp == c)
 375             lcdp++;
 376
 377           if ((*dp++ = c) == '\r' && !Raw && _farnspeekb (xbuf_addr) == '\n')
 378             {
 379               dp--;
 380               *dp++ = '\n';
 381               xbuf_addr++;
 382               if (*lcdp == '\n')
 383                 lcdp++;
 384             }
 385           /* Windows reportedly rounds up the size of clipboard data
 386              (passed in SIZE) to a multiple of 32, and removes trailing
 387              spaces from each line without updating SIZE.  We therefore
 388              bail out when we see the first null character.  */
 389           else if (c == '\0')
 390             break;
 391         }
 392
 393       /* If the text in clipboard is identical to what we put there
 394          last time set_clipboard_data was called, pretend there's no
 395          data in the clipboard.  This is so we don't pass our own text
 396          from the clipboard (which might be troublesome if the killed
 397          text includes null characters).  */
 398       if (last_clipboard_text &&
 399           xbuf_addr - xbuf_beg == (long)(lcdp - last_clipboard_text))
 400         dp = (unsigned char *)Data + 1;
 401     }
 402
 403   free_xfer_buf ();
 404
 405   return (unsigned) (dp - (unsigned char *)Data - 1);
 406 }
 407
 408 /* Close clipboard, return non-zero if successfull.  */
 409 unsigned
 410 close_clipboard (void)
 411 {
 412   __dpmi_regs regs;
 413
 414   /* Calls Int 2Fh/AX=1708h
 415      Return Values   AX == 0: Error occurred
 416                         <> 0: OK */
 417   regs.x.ax = 0x1708;
 418   __dpmi_int(0x2f, &regs);
 419   return regs.x.ax;
 420 }
 421
 422 /* Compact clipboard data so that at least SIZE bytes is available.  */
 423 unsigned
 424 clipboard_compact (unsigned Size)
 425 {
 426   __dpmi_regs regs;
 427
 428   /* Calls Int 2Fh/AX=1709H with:
 429                      SI:CX = Desired memory size in bytes.
 430      Return Values   DX:AX == Number of bytes of largest block of free memory.
 431                            == 0 if error or no memory  */
 432   regs.x.ax = 0x1709;
 433   regs.x.si = Size >> 16;
 434   regs.x.cx = Size & 0xffff;
 435   __dpmi_int(0x2f, &regs);
 436   return ((unsigned)regs.x.dx << 16) | regs.x.ax;
 437 }
 438 \f
 439 static char no_mem_msg[] =
 440   "(Not enough DOS memory to put saved text into clipboard.)";
 441 static char binary_msg[] =
 442   "(Binary characters in saved text; clipboard data not set.)";
 443 static char system_error_msg[] =
 444   "(Clipboard interface failure; clipboard data not set.)";
 445
 446 DEFUN ("w16-set-clipboard-data", Fw16_set_clipboard_data, Sw16_set_clipboard_data, 1, 2, 0,
 447        doc: /* This sets the clipboard data to the given text.  */)
 448   (Lisp_Object string, Lisp_Object frame)
 449 {
 450   unsigned ok = 1, put_status = 0;
 451   int nbytes, no_crlf_conversion;
 452   unsigned char *src, *dst = NULL;
 453
 454   CHECK_STRING (string);
 455
 456   if (NILP (frame))
 457     frame = Fselected_frame ();
 458
 459   CHECK_LIVE_FRAME (frame);
 460   if ( !FRAME_MSDOS_P (XFRAME (frame)))
 461     goto done;
 462
 463   BLOCK_INPUT;
 464
 465   if (!open_clipboard ())
 466     goto error;
 467
 468   nbytes = SBYTES (string);
 469   src = SDATA (string);
 470
 471   /* Do we need to encode this text?  */
 472   for (dst = src; dst < src + nbytes; dst++)
 473     {
 474       if (*dst == '\0' || *dst >= 0x80)
 475         break;
 476     }
 477   if (dst >= src + nbytes)
 478     {
 479       /* No multibyte characters in text.  We need not encode it, but we
 480          will have to convert it to DOS CR-LF style.  */
 481       no_crlf_conversion = 0;
 482       Vlast_coding_system_used = Qraw_text;
 483       dst = NULL;       /* so we don't try to free a random pointer */
 484     }
 485   else
 486     {
 487       /* We must encode contents of STRING according to what
 488          clipboard-coding-system specifies.  */
 489       struct coding_system coding;
 490       Lisp_Object coding_system =
 491         NILP (Vnext_selection_coding_system) ?
 492         Vselection_coding_system : Vnext_selection_coding_system;
 493
 494       setup_coding_system (Fcheck_coding_system (coding_system), &coding);
 495       coding.dst_bytes = nbytes * 4;
 496       coding.destination = (unsigned char *) xmalloc (coding.dst_bytes);
 497       Vnext_selection_coding_system = Qnil;
 498       coding.mode |= CODING_MODE_LAST_BLOCK;
 499       dst = coding.destination;
 500       encode_coding_object (&coding, string, 0, 0,
 501                             SCHARS (string), nbytes, Qnil);
 502       no_crlf_conversion = 1;
 503       nbytes = coding.produced;
 504       Vlast_coding_system_used = CODING_ID_NAME (coding.id);
 505       src = dst;
 506     }
 507
 508   ok = empty_clipboard ()
 509     && ((put_status
 510          = set_clipboard_data (CF_OEMTEXT, src, nbytes, no_crlf_conversion))
 511         == 0);
 512
 513   if (!no_crlf_conversion)
 514   close_clipboard ();
 515
 516   if (ok) goto unblock;
 517
 518  error:
 519
 520   ok = 0;
 521
 522  unblock:
 523   xfree (dst);
 524   UNBLOCK_INPUT;
 525
 526   /* Notify user if the text is too large to fit into DOS memory.
 527      (This will happen somewhere after 600K bytes (470K in DJGPP v1.x),
 528      depending on user system configuration.)  If we just silently
 529      fail the function, people might wonder why their text sometimes
 530      doesn't make it to the clipboard.  */
 531   if (put_status)
 532     {
 533       switch (put_status)
 534         {
 535           case 1:
 536             message2 (no_mem_msg, sizeof (no_mem_msg) - 1, 0);
 537             break;
 538           case 2:
 539             message2 (binary_msg, sizeof (binary_msg) - 1, 0);
 540             break;
 541           case 3:
 542             message2 (system_error_msg, sizeof (system_error_msg) - 1, 0);
 543             break;
 544         }
 545       sit_for (make_number (2), 0, 2);
 546     }
 547
 548  done:
 549
 550   return (ok && put_status == 0 ? string : Qnil);
 551 }
 552
 553 DEFUN ("w16-get-clipboard-data", Fw16_get_clipboard_data, Sw16_get_clipboard_data, 0, 1, 0,
 554        doc: /* This gets the clipboard data in text format.  */)
 555   (Lisp_Object frame)
 556 {
 557   unsigned data_size, truelen;
 558   unsigned char *htext = NULL;
 559   Lisp_Object ret = Qnil;
 560   int require_decoding = 0;
 561
 562   if (NILP (frame))
 563     frame = Fselected_frame ();
 564
 565   CHECK_LIVE_FRAME (frame);
 566   if ( !FRAME_MSDOS_P (XFRAME (frame)))
 567     goto done;
 568
 569   BLOCK_INPUT;
 570
 571   if (!open_clipboard ())
 572     goto unblock;
 573
 574   if ((data_size = get_clipboard_data_size (CF_OEMTEXT)) == 0 ||
 575       (htext = (unsigned char *)xmalloc (data_size)) == 0)
 576     goto closeclip;
 577
 578   /* need to know final size after '\r' chars are removed because
 579      we can't change the string size manually, and doing an extra
 580      copy is silly */
 581   if ((truelen = get_clipboard_data (CF_OEMTEXT, htext, data_size, 0)) == 0)
 582     goto closeclip;
 583
 584   /* Do we need to decode it?  */
 585   {
 586     /* If the clipboard data contains any 8-bit Latin-1 code, we
 587        need to decode it.  */
 588     int i;
 589
 590     for (i = 0; i < truelen; i++)
 591       {
 592         if (htext[i] >= 0x80)
 593           {
 594             require_decoding = 1;
 595             break;
 596           }
 597       }
 598   }
 599   if (require_decoding)
 600     {
 601       struct coding_system coding;
 602       Lisp_Object coding_system = Vnext_selection_coding_system;
 603
 604       truelen = get_clipboard_data (CF_OEMTEXT, htext, data_size, 1);
 605       if (NILP (coding_system))
 606         coding_system = Vselection_coding_system;
 607       setup_coding_system (Fcheck_coding_system (coding_system), &coding);
 608       coding.source = htext;
 609       coding.mode |= CODING_MODE_LAST_BLOCK;
 610       /* We explicitly disable composition handling because selection
 611          data should not contain any composition sequence.  */
 612       coding.mode &= CODING_ANNOTATION_MASK;
 613       decode_coding_object (&coding, Qnil, 0, 0, truelen, truelen, Qt);
 614       ret = coding.dst_object;
 615       Vlast_coding_system_used = CODING_ID_NAME (coding.id);
 616     }
 617   else
 618     {
 619       ret = make_unibyte_string ((char *) htext, truelen);
 620       Vlast_coding_system_used = Qraw_text;
 621     }
 622
 623   xfree (htext);
 624   Vnext_selection_coding_system = Qnil;
 625
 626  closeclip:
 627   close_clipboard ();
 628
 629  unblock:
 630   UNBLOCK_INPUT;
 631
 632  done:
 633
 634   return (ret);
 635 }
 636
 637 /* Support checking for a clipboard selection. */
 638
 639 DEFUN ("x-selection-exists-p", Fx_selection_exists_p, Sx_selection_exists_p,
 640        0, 1, 0,
 641        doc: /* Whether there is an owner for the given X Selection.
 642 The arg should be the name of the selection in question, typically one of
 643 the symbols `PRIMARY', `SECONDARY', or `CLIPBOARD'.
 644 \(Those are literal upper-case symbol names, since that's what X expects.)
 645 For convenience, the symbol nil is the same as `PRIMARY',
 646 and t is the same as `SECONDARY'.  */)
 647   (Lisp_Object selection)
 648 {
 649   CHECK_SYMBOL (selection);
 650
 651   /* Return nil for SECONDARY selection.  For PRIMARY (or nil)
 652      selection, check if there is some text on the kill-ring;
 653      for CLIPBOARD, check if the clipboard currently has valid
 654      text format contents.
 655
 656      The test for killed text on the kill-ring emulates the Emacs
 657      behavior on X, where killed text is also put into X selection
 658      by the X interface code.  (On MSDOS, killed text is only put
 659      into the clipboard if we run under Windows, so we cannot check
 660      the clipboard alone.)  */
 661   if ((EQ (selection, Qnil) || EQ (selection, QPRIMARY))
 662       && ! NILP (Fsymbol_value (Fintern_soft (build_string ("kill-ring"),
 663                                               Qnil))))
 664     return Qt;
 665
 666   if (EQ (selection, QCLIPBOARD))
 667     {
 668       Lisp_Object val = Qnil;
 669
 670       if (open_clipboard ())
 671         {
 672           if (get_clipboard_data_size (CF_OEMTEXT))
 673             val = Qt;
 674           close_clipboard ();
 675         }
 676       return val;
 677     }
 678   return Qnil;
 679 }
 680
 681 void
 682 syms_of_win16select (void)
 683 {
 684   defsubr (&Sw16_set_clipboard_data);
 685   defsubr (&Sw16_get_clipboard_data);
 686   defsubr (&Sx_selection_exists_p);
 687
 688   DEFVAR_LISP ("selection-coding-system", Vselection_coding_system,
 689                doc: /* Coding system for communicating with other programs.
 690
 691 For MS-Windows and MS-DOS:
 692 When sending or receiving text via selection and clipboard, the text
 693 is encoded or decoded by this coding system.  The default value is
 694 the current system default encoding on 9x/Me, `utf-16le-dos'
 695 \(Unicode) on NT/W2K/XP, and `iso-latin-1-dos' on MS-DOS.
 696
 697 For X Windows:
 698 When sending text via selection and clipboard, if the target
 699 data-type matches with the type of this coding system, it is used
 700 for encoding the text.  Otherwise (including the case that this
 701 variable is nil), a proper coding system is used as below:
 702
 703 data-type       coding system
 704 ---------       -------------
 705 UTF8_STRING     utf-8
 706 COMPOUND_TEXT   compound-text-with-extensions
 707 STRING          iso-latin-1
 708 C_STRING        no-conversion
 709
 710 When receiving text, if this coding system is non-nil, it is used
 711 for decoding regardless of the data-type.  If this is nil, a
 712 proper coding system is used according to the data-type as above.
 713
 714 See also the documentation of the variable `x-select-request-type' how
 715 to control which data-type to request for receiving text.
 716
 717 The default value is nil.  */);
 718   Vselection_coding_system = intern ("iso-latin-1-dos");
 719
 720   DEFVAR_LISP ("next-selection-coding-system", Vnext_selection_coding_system,
 721                doc: /* Coding system for the next communication with other programs.
 722 Usually, `selection-coding-system' is used for communicating with
 723 other programs (X Windows clients or MS Windows programs).  But, if this
 724 variable is set, it is used for the next communication only.
 725 After the communication, this variable is set to nil.  */);
 726   Vnext_selection_coding_system = Qnil;
 727
 728   QPRIMARY   = intern ("PRIMARY");      staticpro (&QPRIMARY);
 729   QCLIPBOARD = intern ("CLIPBOARD");    staticpro (&QCLIPBOARD);
 730 }
 731
 732 #endif /* MSDOS */
 733