src/w16select.c

   1 /* 16-bit Windows Selection processing for emacs on MS-Windows
   2
   3 Copyright (C) 1996, 1997, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
   4  2008, 2009, 2010  Free Software Foundation, Inc.
   5
   6 This file is part of GNU Emacs.
   7
   8 GNU Emacs is free software: you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation, either version 3 of the License, or
  11 (at your option) any later version.
  12
  13 GNU Emacs is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 /* These functions work by using WinOldAp interface.  WinOldAp
  22    (WINOLDAP.MOD) is a Microsoft Windows extension supporting
  23    "old" (character-mode) application access to Dynamic Data Exchange,
  24    menus, and the Windows clipboard.  */
  25
  26 /* Written by Dale P. Smith <dpsm@en.com>  */
  27 /* Adapted to DJGPP by Eli Zaretskii <eliz@gnu.org>  */
  28
  29 #ifdef MSDOS
  30
  31 #include <config.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 \f
  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 (void)
 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 (void)
 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 (void)
 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 (unsigned want_size)
 166 {
 167   __dpmi_regs regs;
 168
 169   /* If the usual DJGPP transfer buffer is large enough, use that.  */
 170   if (want_size <= _go32_info_block.size_of_transfer_buffer)
 171     return __tb & 0xfffff;
 172
 173   /* Don't even try to allocate more than 1MB of memory: DOS cannot
 174      possibly handle that (it will overflow the BX register below).  */
 175   if (want_size > 0xfffff)
 176     return 0;
 177
 178   /* Need size rounded up to the nearest paragraph, and in
 179      paragraph units (1 paragraph = 16 bytes).  */
 180   clipboard_xfer_buf_info.size = (want_size + 15) >> 4;
 181
 182   /* The NT DPMI host crashes us if we free DOS memory via the
 183      DPMI service.  Work around by calling DOS allocate/free block.  */
 184   regs.h.ah = 0x48;
 185   regs.x.bx = clipboard_xfer_buf_info.size;
 186   __dpmi_int (0x21, &regs);
 187   if (regs.x.flags & 1)
 188     {
 189       clipboard_xfer_buf_info.size = 0;
 190       return 0;
 191     }
 192
 193   clipboard_xfer_buf_info.rm_segment = regs.x.ax;
 194   return (((int)clipboard_xfer_buf_info.rm_segment) << 4) & 0xfffff;
 195 }
 196
 197 /* Free our clipboard buffer.  We always free it after use, because
 198    keeping it leaves less free conventional memory for subprocesses.
 199    The clipboard buffer tends to be large in size, because for small
 200    clipboard data sizes we use the DJGPP transfer buffer.  */
 201 static void
 202 free_xfer_buf (void)
 203 {
 204   /* If the size is 0, we used DJGPP transfer buffer, so don't free.  */
 205   if (clipboard_xfer_buf_info.size)
 206     {
 207       __dpmi_regs regs;
 208
 209       /* The NT DPMI host crashes us if we free DOS memory via
 210          the DPMI service.  Work around by calling DOS free block.  */
 211       regs.h.ah = 0x49;
 212       regs.x.es = clipboard_xfer_buf_info.rm_segment;
 213       __dpmi_int (0x21, &regs);
 214       clipboard_xfer_buf_info.size = 0;
 215     }
 216 }
 217
 218 /* Copy data into the clipboard, return zero if successfull.  */
 219 unsigned
 220 set_clipboard_data (unsigned Format, void *Data, unsigned Size, int Raw)
 221 {
 222   __dpmi_regs regs;
 223   unsigned truelen;
 224   unsigned long xbuf_addr, buf_offset;
 225   unsigned char *dp = Data, *dstart = dp;
 226
 227   if (Format != CF_OEMTEXT)
 228     return 3;
 229
 230   /* need to know final size after '\r' chars are inserted (the
 231      standard CF_OEMTEXT clipboard format uses CRLF line endings,
 232      while Emacs uses just LF internally).  */
 233   truelen = Size + 1;           /* +1 for the terminating null */
 234
 235   if (!Raw)
 236     {
 237       /* avoid using strchr because it recomputes the length everytime */
 238       while ((dp = memchr (dp, '\n', Size - (dp - dstart))) != 0)
 239         {
 240           truelen++;
 241           dp++;
 242         }
 243     }
 244
 245   if (clipboard_compact (truelen) < truelen)
 246     return 1;
 247
 248   if ((xbuf_addr = alloc_xfer_buf (truelen)) == 0)
 249     return 1;
 250
 251   /* Move the buffer into the low memory, convert LF into CR-LF if needed.  */
 252   if (Raw)
 253     {
 254       dosmemput (Data, Size, xbuf_addr);
 255
 256       /* Terminate with a null, otherwise Windows does strange things
 257          when the text size is an integral multiple of 32 bytes. */
 258       _farpokeb (_dos_ds, xbuf_addr + Size, '\0');
 259     }
 260   else
 261     {
 262       dp = Data;
 263       buf_offset = xbuf_addr;
 264       _farsetsel (_dos_ds);
 265       while (Size--)
 266         {
 267           /* Don't allow them to put binary data into the clipboard, since
 268              it will cause yanked data to be truncated at the first null.  */
 269           if (*dp == '\0')
 270             return 2;
 271           if (*dp == '\n')
 272             _farnspokeb (buf_offset++, '\r');
 273           _farnspokeb (buf_offset++, *dp++);
 274         }
 275
 276       /* Terminate with a null, otherwise Windows does strange things
 277          when the text size is an integral multiple of 32 bytes. */
 278       _farnspokeb (buf_offset, '\0');
 279     }
 280
 281   /* Stash away the data we are about to put into the clipboard, so we
 282      could later check inside get_clipboard_data whether the clipboard
 283      still holds our data.  */
 284   if (clipboard_storage_size < truelen)
 285     {
 286       clipboard_storage_size = truelen + 100;
 287       last_clipboard_text =
 288         (char *) xrealloc (last_clipboard_text, clipboard_storage_size);
 289     }
 290   if (last_clipboard_text)
 291     dosmemget (xbuf_addr, truelen, last_clipboard_text);
 292
 293   /* Calls Int 2Fh/AX=1703h with:
 294                      DX = WinOldAp-Supported Clipboard format
 295                      ES:BX = Pointer to data
 296                      SI:CX = Size of data in bytes
 297      Return Values   AX == 0: Error occurred
 298                         <> 0: OK.  Data copied into the Clipboard.  */
 299   regs.x.ax = 0x1703;
 300   regs.x.dx = Format;
 301   regs.x.si = truelen >> 16;
 302   regs.x.cx = truelen & 0xffff;
 303   regs.x.es = xbuf_addr >> 4;
 304   regs.x.bx = xbuf_addr & 15;
 305   __dpmi_int(0x2f, &regs);
 306
 307   free_xfer_buf ();
 308
 309   /* If the above failed, invalidate the local copy of the clipboard.  */
 310   if (regs.x.ax == 0)
 311     *last_clipboard_text = '\0';
 312
 313   /* Zero means success, otherwise (1, 2, or 3) it's an error.  */
 314   return regs.x.ax > 0 ? 0 : 3;
 315 }
 316
 317 /* Return the size of the clipboard data of format FORMAT.  */
 318 unsigned
 319 get_clipboard_data_size (unsigned Format)
 320 {
 321   __dpmi_regs regs;
 322
 323   /* Calls Int 2Fh/AX=1704h with:
 324                      DX = WinOldAp-Supported Clipboard format
 325      Return Values   DX:AX == Size of the data in bytes, including any
 326                               headers.
 327                            == 0 If data in this format is not in
 328                            the clipboard.  */
 329   regs.x.ax = 0x1704;
 330   regs.x.dx = Format;
 331   __dpmi_int(0x2f, &regs);
 332   return ( (((unsigned)regs.x.dx) << 16) | regs.x.ax);
 333 }
 334
 335 /* Get clipboard data, return its length.
 336    Warning: this doesn't check whether DATA has enough space to hold
 337    SIZE bytes.  */
 338 unsigned
 339 get_clipboard_data (unsigned Format, void *Data, unsigned Size, int Raw)
 340 {
 341   __dpmi_regs regs;
 342   unsigned long xbuf_addr;
 343   unsigned char *dp = Data;
 344
 345   if (Format != CF_OEMTEXT)
 346     return 0;
 347
 348   if (Size == 0)
 349     return 0;
 350
 351   if ((xbuf_addr = alloc_xfer_buf (Size)) == 0)
 352     return 0;
 353
 354   /* Calls Int 2Fh/AX=1705h with:
 355                      DX = WinOldAp-Supported Clipboard format
 356                      ES:BX = Pointer to data buffer to hold data
 357      Return Values   AX == 0: Error occurred (or data in this format is not
 358                               in the clipboard)
 359                         <> 0: OK  */
 360   regs.x.ax = 0x1705;
 361   regs.x.dx = Format;
 362   regs.x.es = xbuf_addr >> 4;
 363   regs.x.bx = xbuf_addr & 15;
 364   __dpmi_int(0x2f, &regs);
 365   if (regs.x.ax != 0)
 366     {
 367       unsigned char null_char = '\0';
 368       unsigned long xbuf_beg = xbuf_addr;
 369
 370       /* If last_clipboard_text is NULL, we don't want to slow down
 371          the next loop by an additional test.  */
 372       register unsigned char *lcdp =
 373         last_clipboard_text == NULL ? &null_char : last_clipboard_text;
 374
 375       /* Copy data from low memory, remove CR
 376          characters before LF if needed.  */
 377       _farsetsel (_dos_ds);
 378       while (Size--)
 379         {
 380           register unsigned char c = _farnspeekb (xbuf_addr++);
 381
 382           if (*lcdp == c)
 383             lcdp++;
 384
 385           if ((*dp++ = c) == '\r' && !Raw && _farnspeekb (xbuf_addr) == '\n')
 386             {
 387               dp--;
 388               *dp++ = '\n';
 389               xbuf_addr++;
 390               if (*lcdp == '\n')
 391                 lcdp++;
 392             }
 393           /* Windows reportedly rounds up the size of clipboard data
 394              (passed in SIZE) to a multiple of 32, and removes trailing
 395              spaces from each line without updating SIZE.  We therefore
 396              bail out when we see the first null character.  */
 397           else if (c == '\0')
 398             break;
 399         }
 400
 401       /* If the text in clipboard is identical to what we put there
 402          last time set_clipboard_data was called, pretend there's no
 403          data in the clipboard.  This is so we don't pass our own text
 404          from the clipboard (which might be troublesome if the killed
 405          text includes null characters).  */
 406       if (last_clipboard_text &&
 407           xbuf_addr - xbuf_beg == (long)(lcdp - last_clipboard_text))
 408         dp = (unsigned char *)Data + 1;
 409     }
 410
 411   free_xfer_buf ();
 412
 413   return (unsigned) (dp - (unsigned char *)Data - 1);
 414 }
 415
 416 /* Close clipboard, return non-zero if successfull.  */
 417 unsigned
 418 close_clipboard (void)
 419 {
 420   __dpmi_regs regs;
 421
 422   /* Calls Int 2Fh/AX=1708h
 423      Return Values   AX == 0: Error occurred
 424                         <> 0: OK */
 425   regs.x.ax = 0x1708;
 426   __dpmi_int(0x2f, &regs);
 427   return regs.x.ax;
 428 }
 429
 430 /* Compact clipboard data so that at least SIZE bytes is available.  */
 431 unsigned
 432 clipboard_compact (unsigned Size)
 433 {
 434   __dpmi_regs regs;
 435
 436   /* Calls Int 2Fh/AX=1709H with:
 437                      SI:CX = Desired memory size in bytes.
 438      Return Values   DX:AX == Number of bytes of largest block of free memory.
 439                            == 0 if error or no memory  */
 440   regs.x.ax = 0x1709;
 441   regs.x.si = Size >> 16;
 442   regs.x.cx = Size & 0xffff;
 443   __dpmi_int(0x2f, &regs);
 444   return ((unsigned)regs.x.dx << 16) | regs.x.ax;
 445 }
 446 \f
 447 static char no_mem_msg[] =
 448   "(Not enough DOS memory to put saved text into clipboard.)";
 449 static char binary_msg[] =
 450   "(Binary characters in saved text; clipboard data not set.)";
 451 static char system_error_msg[] =
 452   "(Clipboard interface failure; clipboard data not set.)";
 453
 454 DEFUN ("w16-set-clipboard-data", Fw16_set_clipboard_data, Sw16_set_clipboard_data, 1, 2, 0,
 455        doc: /* This sets the clipboard data to the given text.  */)
 456   (Lisp_Object string, Lisp_Object frame)
 457 {
 458   unsigned ok = 1, put_status = 0;
 459   int nbytes, no_crlf_conversion;
 460   unsigned char *src, *dst = NULL;
 461
 462   CHECK_STRING (string);
 463
 464   if (NILP (frame))
 465     frame = Fselected_frame ();
 466
 467   CHECK_LIVE_FRAME (frame);
 468   if ( !FRAME_MSDOS_P (XFRAME (frame)))
 469     goto done;
 470
 471   BLOCK_INPUT;
 472
 473   if (!open_clipboard ())
 474     goto error;
 475
 476   nbytes = SBYTES (string);
 477   src = SDATA (string);
 478
 479   /* Do we need to encode this text?  */
 480   for (dst = src; dst < src + nbytes; dst++)
 481     {
 482       if (*dst == '\0' || *dst >= 0x80)
 483         break;
 484     }
 485   if (dst >= src + nbytes)
 486     {
 487       /* No multibyte characters in text.  We need not encode it, but we
 488          will have to convert it to DOS CR-LF style.  */
 489       no_crlf_conversion = 0;
 490       Vlast_coding_system_used = Qraw_text;
 491       dst = NULL;       /* so we don't try to free a random pointer */
 492     }
 493   else
 494     {
 495       /* We must encode contents of STRING according to what
 496          clipboard-coding-system specifies.  */
 497       struct coding_system coding;
 498       Lisp_Object coding_system =
 499         NILP (Vnext_selection_coding_system) ?
 500         Vselection_coding_system : Vnext_selection_coding_system;
 501
 502       setup_coding_system (Fcheck_coding_system (coding_system), &coding);
 503       coding.dst_bytes = nbytes * 4;
 504       coding.destination = (unsigned char *) xmalloc (coding.dst_bytes);
 505       Vnext_selection_coding_system = Qnil;
 506       coding.mode |= CODING_MODE_LAST_BLOCK;
 507       dst = coding.destination;
 508       encode_coding_object (&coding, string, 0, 0,
 509                             SCHARS (string), nbytes, Qnil);
 510       no_crlf_conversion = 1;
 511       nbytes = coding.produced;
 512       Vlast_coding_system_used = CODING_ID_NAME (coding.id);
 513       src = dst;
 514     }
 515
 516   ok = empty_clipboard ()
 517     && ((put_status
 518          = set_clipboard_data (CF_OEMTEXT, src, nbytes, no_crlf_conversion))
 519         == 0);
 520
 521   if (!no_crlf_conversion)
 522   close_clipboard ();
 523
 524   if (ok) goto unblock;
 525
 526  error:
 527
 528   ok = 0;
 529
 530  unblock:
 531   xfree (dst);
 532   UNBLOCK_INPUT;
 533
 534   /* Notify user if the text is too large to fit into DOS memory.
 535      (This will happen somewhere after 600K bytes (470K in DJGPP v1.x),
 536      depending on user system configuration.)  If we just silently
 537      fail the function, people might wonder why their text sometimes
 538      doesn't make it to the clipboard.  */
 539   if (put_status)
 540     {
 541       switch (put_status)
 542         {
 543           case 1:
 544             message2 (no_mem_msg, sizeof (no_mem_msg) - 1, 0);
 545             break;
 546           case 2:
 547             message2 (binary_msg, sizeof (binary_msg) - 1, 0);
 548             break;
 549           case 3:
 550             message2 (system_error_msg, sizeof (system_error_msg) - 1, 0);
 551             break;
 552         }
 553       sit_for (make_number (2), 0, 2);
 554     }
 555
 556  done:
 557
 558   return (ok && put_status == 0 ? string : Qnil);
 559 }
 560
 561 DEFUN ("w16-get-clipboard-data", Fw16_get_clipboard_data, Sw16_get_clipboard_data, 0, 1, 0,
 562        doc: /* This gets the clipboard data in text format.  */)
 563   (Lisp_Object frame)
 564 {
 565   unsigned data_size, truelen;
 566   unsigned char *htext = NULL;
 567   Lisp_Object ret = Qnil;
 568   int require_decoding = 0;
 569
 570   if (NILP (frame))
 571     frame = Fselected_frame ();
 572
 573   CHECK_LIVE_FRAME (frame);
 574   if ( !FRAME_MSDOS_P (XFRAME (frame)))
 575     goto done;
 576
 577   BLOCK_INPUT;
 578
 579   if (!open_clipboard ())
 580     goto unblock;
 581
 582   if ((data_size = get_clipboard_data_size (CF_OEMTEXT)) == 0 ||
 583       (htext = (unsigned char *)xmalloc (data_size)) == 0)
 584     goto closeclip;
 585
 586   /* need to know final size after '\r' chars are removed because
 587      we can't change the string size manually, and doing an extra
 588      copy is silly */
 589   if ((truelen = get_clipboard_data (CF_OEMTEXT, htext, data_size, 0)) == 0)
 590     goto closeclip;
 591
 592   /* Do we need to decode it?  */
 593   {
 594     /* If the clipboard data contains any 8-bit Latin-1 code, we
 595        need to decode it.  */
 596     int i;
 597
 598     for (i = 0; i < truelen; i++)
 599       {
 600         if (htext[i] >= 0x80)
 601           {
 602             require_decoding = 1;
 603             break;
 604           }
 605       }
 606   }
 607   if (require_decoding)
 608     {
 609       struct coding_system coding;
 610       Lisp_Object coding_system = Vnext_selection_coding_system;
 611
 612       truelen = get_clipboard_data (CF_OEMTEXT, htext, data_size, 1);
 613       if (NILP (coding_system))
 614         coding_system = Vselection_coding_system;
 615       setup_coding_system (Fcheck_coding_system (coding_system), &coding);
 616       coding.source = htext;
 617       coding.mode |= CODING_MODE_LAST_BLOCK;
 618       /* We explicitly disable composition handling because selection
 619          data should not contain any composition sequence.  */
 620       coding.mode &= CODING_ANNOTATION_MASK;
 621       decode_coding_object (&coding, Qnil, 0, 0, truelen, truelen, Qt);
 622       ret = coding.dst_object;
 623       Vlast_coding_system_used = CODING_ID_NAME (coding.id);
 624     }
 625   else
 626     {
 627       ret = make_unibyte_string ((char *) htext, truelen);
 628       Vlast_coding_system_used = Qraw_text;
 629     }
 630
 631   xfree (htext);
 632   Vnext_selection_coding_system = Qnil;
 633
 634  closeclip:
 635   close_clipboard ();
 636
 637  unblock:
 638   UNBLOCK_INPUT;
 639
 640  done:
 641
 642   return (ret);
 643 }
 644
 645 /* Support checking for a clipboard selection. */
 646
 647 DEFUN ("x-selection-exists-p", Fx_selection_exists_p, Sx_selection_exists_p,
 648        0, 1, 0,
 649        doc: /* Whether there is an owner for the given X Selection.
 650 The arg should be the name of the selection in question, typically one of
 651 the symbols `PRIMARY', `SECONDARY', or `CLIPBOARD'.
 652 \(Those are literal upper-case symbol names, since that's what X expects.)
 653 For convenience, the symbol nil is the same as `PRIMARY',
 654 and t is the same as `SECONDARY'.  */)
 655   (Lisp_Object selection)
 656 {
 657   CHECK_SYMBOL (selection);
 658
 659   /* Return nil for SECONDARY selection.  For PRIMARY (or nil)
 660      selection, check if there is some text on the kill-ring;
 661      for CLIPBOARD, check if the clipboard currently has valid
 662      text format contents.
 663
 664      The test for killed text on the kill-ring emulates the Emacs
 665      behavior on X, where killed text is also put into X selection
 666      by the X interface code.  (On MSDOS, killed text is only put
 667      into the clipboard if we run under Windows, so we cannot check
 668      the clipboard alone.)  */
 669   if ((EQ (selection, Qnil) || EQ (selection, QPRIMARY))
 670       && ! NILP (Fsymbol_value (Fintern_soft (build_string ("kill-ring"),
 671                                               Qnil))))
 672     return Qt;
 673
 674   if (EQ (selection, QCLIPBOARD))
 675     {
 676       Lisp_Object val = Qnil;
 677
 678       if (open_clipboard ())
 679         {
 680           if (get_clipboard_data_size (CF_OEMTEXT))
 681             val = Qt;
 682           close_clipboard ();
 683         }
 684       return val;
 685     }
 686   return Qnil;
 687 }
 688
 689 void
 690 syms_of_win16select (void)
 691 {
 692   defsubr (&Sw16_set_clipboard_data);
 693   defsubr (&Sw16_get_clipboard_data);
 694   defsubr (&Sx_selection_exists_p);
 695
 696   DEFVAR_LISP ("selection-coding-system", &Vselection_coding_system,
 697                doc: /* Coding system for communicating with other programs.
 698
 699 For MS-Windows and MS-DOS:
 700 When sending or receiving text via selection and clipboard, the text
 701 is encoded or decoded by this coding system.  The default value is
 702 the current system default encoding on 9x/Me, `utf-16le-dos'
 703 \(Unicode) on NT/W2K/XP, and `iso-latin-1-dos' on MS-DOS.
 704
 705 For X Windows:
 706 When sending text via selection and clipboard, if the target
 707 data-type matches with the type of this coding system, it is used
 708 for encoding the text.  Otherwise (including the case that this
 709 variable is nil), a proper coding system is used as below:
 710
 711 data-type       coding system
 712 ---------       -------------
 713 UTF8_STRING     utf-8
 714 COMPOUND_TEXT   compound-text-with-extensions
 715 STRING          iso-latin-1
 716 C_STRING        no-conversion
 717
 718 When receiving text, if this coding system is non-nil, it is used
 719 for decoding regardless of the data-type.  If this is nil, a
 720 proper coding system is used according to the data-type as above.
 721
 722 See also the documentation of the variable `x-select-request-type' how
 723 to control which data-type to request for receiving text.
 724
 725 The default value is nil.  */);
 726   Vselection_coding_system = intern ("iso-latin-1-dos");
 727
 728   DEFVAR_LISP ("next-selection-coding-system", &Vnext_selection_coding_system,
 729                doc: /* Coding system for the next communication with other programs.
 730 Usually, `selection-coding-system' is used for communicating with
 731 other programs (X Windows clients or MS Windows programs).  But, if this
 732 variable is set, it is used for the next communication only.
 733 After the communication, this variable is set to nil.  */);
 734   Vnext_selection_coding_system = Qnil;
 735
 736   QPRIMARY   = intern ("PRIMARY");      staticpro (&QPRIMARY);
 737   QCLIPBOARD = intern ("CLIPBOARD");    staticpro (&QCLIPBOARD);
 738 }
 739
 740 #endif /* MSDOS */
 741