src/gtk/clipbrd.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        src/gtk/clipbrd.cpp
   3 // Purpose:     wxClipboard implementation for wxGTK
   4 // Author:      Robert Roebling, Vadim Zeitlin
   5 // Id:          $Id$
   6 // Copyright:   (c) 1998 Robert Roebling
   7 //              (c) 2007 Vadim Zeitlin
   8 // Licence:     wxWindows licence
   9 /////////////////////////////////////////////////////////////////////////////
  10
  11 // ============================================================================
  12 // declarations
  13 // ============================================================================
  14
  15 // ----------------------------------------------------------------------------
  16 // headers
  17 // ----------------------------------------------------------------------------
  18
  19 // For compilers that support precompilation, includes "wx.h".
  20 #include "wx/wxprec.h"
  21
  22 #if wxUSE_CLIPBOARD
  23
  24 #include "wx/clipbrd.h"
  25
  26 #ifndef WX_PRECOMP
  27     #include "wx/log.h"
  28     #include "wx/utils.h"
  29     #include "wx/dataobj.h"
  30 #endif
  31
  32 #include "wx/scopedarray.h"
  33 #include "wx/scopeguard.h"
  34
  35 #include "wx/gtk/private.h"
  36
  37 typedef wxScopedArray<wxDataFormat> wxDataFormatArray;
  38
  39 // ----------------------------------------------------------------------------
  40 // data
  41 // ----------------------------------------------------------------------------
  42
  43 static GdkAtom  g_clipboardAtom   = 0;
  44 static GdkAtom  g_targetsAtom     = 0;
  45 static GdkAtom  g_timestampAtom   = 0;
  46
  47 #if wxUSE_UNICODE
  48 extern GdkAtom g_altTextAtom;
  49 #endif
  50
  51 // the trace mask we use with wxLogTrace() - call
  52 // wxLog::AddTraceMask(TRACE_CLIPBOARD) to enable the trace messages from here
  53 // (there will be a *lot* of them!)
  54 #define TRACE_CLIPBOARD _T("clipboard")
  55
  56 // ----------------------------------------------------------------------------
  57 // wxClipboardSync: used to perform clipboard operations synchronously
  58 // ----------------------------------------------------------------------------
  59
  60 // constructing this object on stack will wait wait until the latest clipboard
  61 // operation is finished on block exit
  62 //
  63 // notice that there can be no more than one such object alive at any moment,
  64 // i.e. reentrancies are not allowed
  65 class wxClipboardSync
  66 {
  67 public:
  68     wxClipboardSync(wxClipboard& clipboard)
  69     {
  70         wxASSERT_MSG( !ms_clipboard, _T("reentrancy in clipboard code") );
  71         ms_clipboard = &clipboard;
  72     }
  73
  74     ~wxClipboardSync()
  75     {
  76         while (ms_clipboard)
  77             wxTheApp->YieldFor(wxEVT_CATEGORY_CLIPBOARD);
  78     }
  79
  80     // this method must be called by GTK+ callbacks to indicate that we got the
  81     // result for our clipboard operation
  82     static void OnDone(wxClipboard * WXUNUSED_UNLESS_DEBUG(clipboard))
  83     {
  84         wxASSERT_MSG( clipboard == ms_clipboard,
  85                         _T("got notification for alien clipboard") );
  86
  87         ms_clipboard = NULL;
  88     }
  89
  90     // this method should be called if it's possible that no async clipboard
  91     // operation is currently in progress (like it can be the case when the
  92     // clipboard is cleared but not because we asked about it), it should only
  93     // be called if such situation is expected -- otherwise call OnDone() which
  94     // would assert in this case
  95     static void OnDoneIfInProgress(wxClipboard *clipboard)
  96     {
  97         if ( ms_clipboard )
  98             OnDone(clipboard);
  99     }
 100
 101 private:
 102     static wxClipboard *ms_clipboard;
 103
 104     DECLARE_NO_COPY_CLASS(wxClipboardSync)
 105 };
 106
 107 wxClipboard *wxClipboardSync::ms_clipboard = NULL;
 108
 109 // ============================================================================
 110 // clipboard callbacks implementation
 111 // ============================================================================
 112
 113 //-----------------------------------------------------------------------------
 114 // "selection_received" for targets
 115 //-----------------------------------------------------------------------------
 116
 117 extern "C" {
 118 static void
 119 targets_selection_received( GtkWidget *WXUNUSED(widget),
 120                             GtkSelectionData *selection_data,
 121                             guint32 WXUNUSED(time),
 122                             wxClipboard *clipboard )
 123 {
 124     if ( !clipboard )
 125         return;
 126
 127     wxON_BLOCK_EXIT1(wxClipboardSync::OnDone, clipboard);
 128
 129     if ( !selection_data || selection_data->length <= 0 )
 130         return;
 131
 132     // make sure we got the data in the correct form
 133     GdkAtom type = selection_data->type;
 134     if ( type != GDK_SELECTION_TYPE_ATOM )
 135     {
 136         if ( strcmp(wxGtkString(gdk_atom_name(type)), "TARGETS") != 0 )
 137         {
 138             wxLogTrace( TRACE_CLIPBOARD,
 139                         _T("got unsupported clipboard target") );
 140
 141             return;
 142         }
 143     }
 144
 145 #ifdef __WXDEBUG__
 146     // it's not really a format, of course, but we can reuse its GetId() method
 147     // to format this atom as string
 148     wxDataFormat clip(selection_data->selection);
 149     wxLogTrace( TRACE_CLIPBOARD,
 150                 wxT("Received available formats for clipboard %s"),
 151                 clip.GetId().c_str() );
 152 #endif // __WXDEBUG__
 153
 154     // the atoms we received, holding a list of targets (= formats)
 155     const GdkAtom * const atoms = (GdkAtom *)selection_data->data;
 156     for ( size_t i = 0; i < selection_data->length/sizeof(GdkAtom); i++ )
 157     {
 158         const wxDataFormat format(atoms[i]);
 159
 160         wxLogTrace(TRACE_CLIPBOARD, wxT("\t%s"), format.GetId().c_str());
 161
 162         if ( clipboard->GTKOnTargetReceived(format) )
 163             return;
 164     }
 165 }
 166 }
 167
 168 bool wxClipboard::GTKOnTargetReceived(const wxDataFormat& format)
 169 {
 170     if ( format != m_targetRequested )
 171         return false;
 172
 173     m_formatSupported = true;
 174     return true;
 175 }
 176
 177 //-----------------------------------------------------------------------------
 178 // "selection_received" for the actual data
 179 //-----------------------------------------------------------------------------
 180
 181 extern "C" {
 182 static void
 183 selection_received( GtkWidget *WXUNUSED(widget),
 184                     GtkSelectionData *selection_data,
 185                     guint32 WXUNUSED(time),
 186                     wxClipboard *clipboard )
 187 {
 188     if ( !clipboard )
 189         return;
 190
 191     wxON_BLOCK_EXIT1(wxClipboardSync::OnDone, clipboard);
 192
 193     if ( !selection_data || selection_data->length <= 0 )
 194         return;
 195
 196     clipboard->GTKOnSelectionReceived(*selection_data);
 197 }
 198 }
 199
 200 //-----------------------------------------------------------------------------
 201 // "selection_clear"
 202 //-----------------------------------------------------------------------------
 203
 204 extern "C" {
 205 static gint
 206 selection_clear_clip( GtkWidget *WXUNUSED(widget), GdkEventSelection *event )
 207 {
 208     wxClipboard * const clipboard = wxTheClipboard;
 209     if ( !clipboard )
 210         return TRUE;
 211
 212     // notice the use of OnDoneIfInProgress() here instead of just OnDone():
 213     // it's perfectly possible that we're receiving this notification from GTK+
 214     // even though we hadn't cleared the clipboard ourselves but because
 215     // another application (or even another window in the same program)
 216     // acquired it
 217     wxON_BLOCK_EXIT1(wxClipboardSync::OnDoneIfInProgress, clipboard);
 218
 219     wxClipboard::Kind kind;
 220     if (event->selection == GDK_SELECTION_PRIMARY)
 221     {
 222         wxLogTrace(TRACE_CLIPBOARD, wxT("Lost primary selection" ));
 223
 224         kind = wxClipboard::Primary;
 225     }
 226     else if (event->selection == g_clipboardAtom)
 227     {
 228         wxLogTrace(TRACE_CLIPBOARD, wxT("Lost clipboard" ));
 229
 230         kind = wxClipboard::Clipboard;
 231     }
 232     else // some other selection, we're not concerned
 233     {
 234         return FALSE;
 235     }
 236
 237     // the clipboard is no longer in our hands, we don't need data any more
 238     clipboard->GTKClearData(kind);
 239
 240     return TRUE;
 241 }
 242 }
 243
 244 //-----------------------------------------------------------------------------
 245 // selection handler for supplying data
 246 //-----------------------------------------------------------------------------
 247
 248 extern "C" {
 249 static void
 250 selection_handler( GtkWidget *WXUNUSED(widget),
 251                    GtkSelectionData *selection_data,
 252                    guint WXUNUSED(info),
 253                    guint WXUNUSED(time),
 254                    gpointer signal_data )
 255 {
 256     wxClipboard * const clipboard = wxTheClipboard;
 257     if ( !clipboard )
 258         return;
 259
 260     wxDataObject * const data = clipboard->GTKGetDataObject();
 261     if ( !data )
 262         return;
 263
 264     // ICCCM says that TIMESTAMP is a required atom.
 265     // In particular, it satisfies Klipper, which polls
 266     // TIMESTAMP to see if the clipboards content has changed.
 267     // It shall return the time which was used to set the data.
 268     if (selection_data->target == g_timestampAtom)
 269     {
 270         guint timestamp = GPOINTER_TO_UINT (signal_data);
 271         gtk_selection_data_set(selection_data,
 272                                GDK_SELECTION_TYPE_INTEGER,
 273                                32,
 274                                (guchar*)&(timestamp),
 275                                sizeof(timestamp));
 276         wxLogTrace(TRACE_CLIPBOARD,
 277                    _T("Clipboard TIMESTAMP requested, returning timestamp=%u"),
 278                    timestamp);
 279         return;
 280     }
 281
 282     wxDataFormat format( selection_data->target );
 283
 284 #ifdef __WXDEBUG__
 285     wxLogTrace(TRACE_CLIPBOARD,
 286                _T("clipboard data in format %s, GtkSelectionData is target=%s type=%s selection=%s timestamp=%u"),
 287                format.GetId().c_str(),
 288                wxString::FromAscii(wxGtkString(gdk_atom_name(selection_data->target))).c_str(),
 289                wxString::FromAscii(wxGtkString(gdk_atom_name(selection_data->type))).c_str(),
 290                wxString::FromAscii(wxGtkString(gdk_atom_name(selection_data->selection))).c_str(),
 291                GPOINTER_TO_UINT( signal_data )
 292                );
 293 #endif // __WXDEBUG__
 294
 295     if ( !data->IsSupportedFormat( format ) )
 296         return;
 297
 298     int size = data->GetDataSize( format );
 299     if ( !size )
 300         return;
 301
 302     wxCharBuffer buf(size - 1); // it adds 1 internally (for NUL)
 303
 304     // text data must be returned in UTF8 if format is wxDF_UNICODETEXT
 305     if ( !data->GetDataHere(format, buf.data()) )
 306         return;
 307
 308     // use UTF8_STRING format if requested in Unicode build but just plain
 309     // STRING one in ANSI or if explicitly asked in Unicode
 310 #if wxUSE_UNICODE
 311     if (format == wxDataFormat(wxDF_UNICODETEXT))
 312     {
 313         gtk_selection_data_set_text(
 314             selection_data,
 315             (const gchar*)buf.data(),
 316             size );
 317     }
 318     else
 319 #endif // wxUSE_UNICODE
 320     {
 321         gtk_selection_data_set(
 322             selection_data,
 323             GDK_SELECTION_TYPE_STRING,
 324             8*sizeof(gchar),
 325             (const guchar*)buf.data(),
 326             size );
 327     }
 328 }
 329 }
 330
 331 void wxClipboard::GTKOnSelectionReceived(const GtkSelectionData& sel)
 332 {
 333     wxCHECK_RET( m_receivedData, _T("should be inside GetData()") );
 334
 335     const wxDataFormat format(sel.target);
 336     wxLogTrace(TRACE_CLIPBOARD, _T("Received selection %s"),
 337                format.GetId().c_str());
 338
 339     if ( !m_receivedData->IsSupportedFormat(format) )
 340         return;
 341
 342     m_receivedData->SetData(format, sel.length, sel.data);
 343     m_formatSupported = true;
 344 }
 345
 346 //-----------------------------------------------------------------------------
 347 // asynchronous "selection_received" for targets
 348 //-----------------------------------------------------------------------------
 349
 350 extern "C" {
 351 static void
 352 async_targets_selection_received( GtkWidget *WXUNUSED(widget),
 353                             GtkSelectionData *selection_data,
 354                             guint32 WXUNUSED(time),
 355                             wxClipboard *clipboard )
 356 {
 357     if ( !clipboard ) // Assert?
 358         return;
 359
 360     if (!clipboard->m_sink)
 361         return;
 362
 363     wxClipboardEvent *event = new wxClipboardEvent(wxEVT_CLIPBOARD_CHANGED);
 364     event->SetEventObject( clipboard );
 365
 366     if ( !selection_data || selection_data->length <= 0 )
 367     {
 368         clipboard->m_sink->QueueEvent( event );
 369         clipboard->m_sink.Release();
 370         return;
 371     }
 372
 373     // make sure we got the data in the correct form
 374     GdkAtom type = selection_data->type;
 375     if ( type != GDK_SELECTION_TYPE_ATOM )
 376     {
 377         if ( strcmp(wxGtkString(gdk_atom_name(type)), "TARGETS") != 0 )
 378         {
 379             wxLogTrace( TRACE_CLIPBOARD,
 380                         _T("got unsupported clipboard target") );
 381
 382             clipboard->m_sink->QueueEvent( event );
 383             clipboard->m_sink.Release();
 384             return;
 385         }
 386     }
 387
 388 #ifdef __WXDEBUG__
 389     // it's not really a format, of course, but we can reuse its GetId() method
 390     // to format this atom as string
 391     wxDataFormat clip(selection_data->selection);
 392     wxLogTrace( TRACE_CLIPBOARD,
 393                 wxT("Received available formats for clipboard %s"),
 394                 clip.GetId().c_str() );
 395 #endif // __WXDEBUG__
 396
 397     // the atoms we received, holding a list of targets (= formats)
 398     const GdkAtom * const atoms = (GdkAtom *)selection_data->data;
 399     for ( size_t i = 0; i < selection_data->length/sizeof(GdkAtom); i++ )
 400     {
 401         const wxDataFormat format(atoms[i]);
 402
 403         wxLogTrace(TRACE_CLIPBOARD, wxT("\t%s"), format.GetId().c_str());
 404
 405         event->AddFormat( format );
 406     }
 407
 408     clipboard->m_sink->QueueEvent( event );
 409     clipboard->m_sink.Release();
 410 }
 411 }
 412
 413 // ============================================================================
 414 // wxClipboard implementation
 415 // ============================================================================
 416
 417 // ----------------------------------------------------------------------------
 418 // wxClipboard ctor/dtor
 419 // ----------------------------------------------------------------------------
 420
 421 IMPLEMENT_DYNAMIC_CLASS(wxClipboard,wxObject)
 422
 423 wxClipboard::wxClipboard()
 424 {
 425     m_open = false;
 426
 427     m_dataPrimary =
 428     m_dataClipboard =
 429     m_receivedData = NULL;
 430
 431     m_formatSupported = false;
 432     m_targetRequested = 0;
 433
 434     // we use m_targetsWidget to query what formats are available
 435     m_targetsWidget = gtk_window_new( GTK_WINDOW_POPUP );
 436     gtk_widget_realize( m_targetsWidget );
 437
 438     g_signal_connect (m_targetsWidget, "selection_received",
 439                       G_CALLBACK (targets_selection_received), this);
 440
 441     // we use m_targetsWidgetAsync to query what formats are available asynchronously
 442     m_targetsWidgetAsync = gtk_window_new( GTK_WINDOW_POPUP );
 443     gtk_widget_realize( m_targetsWidgetAsync );
 444
 445     g_signal_connect (m_targetsWidgetAsync, "selection_received",
 446                       G_CALLBACK (async_targets_selection_received), this);
 447
 448     // we use m_clipboardWidget to get and to offer data
 449     m_clipboardWidget = gtk_window_new( GTK_WINDOW_POPUP );
 450     gtk_widget_realize( m_clipboardWidget );
 451
 452     g_signal_connect (m_clipboardWidget, "selection_received",
 453                       G_CALLBACK (selection_received), this);
 454
 455     g_signal_connect (m_clipboardWidget, "selection_clear_event",
 456                       G_CALLBACK (selection_clear_clip), NULL);
 457
 458     // initialize atoms we use if not done yet
 459     if ( !g_clipboardAtom )
 460         g_clipboardAtom = gdk_atom_intern( "CLIPBOARD", FALSE );
 461     if ( !g_targetsAtom )
 462         g_targetsAtom = gdk_atom_intern ("TARGETS", FALSE);
 463     if ( !g_timestampAtom )
 464         g_timestampAtom = gdk_atom_intern ("TIMESTAMP", FALSE);
 465 }
 466
 467 wxClipboard::~wxClipboard()
 468 {
 469     Clear();
 470
 471     gtk_widget_destroy( m_clipboardWidget );
 472     gtk_widget_destroy( m_targetsWidget );
 473 }
 474
 475 // ----------------------------------------------------------------------------
 476 // wxClipboard helper functions
 477 // ----------------------------------------------------------------------------
 478
 479 GdkAtom wxClipboard::GTKGetClipboardAtom() const
 480 {
 481     return m_usePrimary ? (GdkAtom)GDK_SELECTION_PRIMARY
 482                         : g_clipboardAtom;
 483 }
 484
 485 void wxClipboard::GTKClearData(Kind kind)
 486 {
 487     wxDataObject *&data = Data(kind);
 488     if ( data )
 489     {
 490         delete data;
 491         data = NULL;
 492     }
 493 }
 494
 495 bool wxClipboard::SetSelectionOwner(bool set)
 496 {
 497     bool rc = gtk_selection_owner_set
 498               (
 499                 set ? m_clipboardWidget : NULL,
 500                 GTKGetClipboardAtom(),
 501                 (guint32)GDK_CURRENT_TIME
 502               );
 503
 504     if ( !rc )
 505     {
 506         wxLogTrace(TRACE_CLIPBOARD, _T("Failed to %sset selection owner"),
 507                    set ? _T("") : _T("un"));
 508     }
 509
 510     return rc;
 511 }
 512
 513 void wxClipboard::AddSupportedTarget(GdkAtom atom)
 514 {
 515     gtk_selection_add_target
 516     (
 517         m_clipboardWidget,
 518         GTKGetClipboardAtom(),
 519         atom,
 520         0 // info (same as client data) unused
 521     );
 522 }
 523
 524 bool wxClipboard::IsSupportedAsync(wxEvtHandler *sink)
 525 {
 526     if (m_sink.get())
 527         return false;  // currently busy, come back later
 528
 529     wxCHECK_MSG( sink, false, wxT("no sink given") );
 530
 531     m_sink = sink;
 532     gtk_selection_convert( m_targetsWidgetAsync,
 533                            GTKGetClipboardAtom(),
 534                            g_targetsAtom,
 535                            (guint32) GDK_CURRENT_TIME );
 536
 537     return true;
 538 }
 539
 540 bool wxClipboard::DoIsSupported(const wxDataFormat& format)
 541 {
 542     wxCHECK_MSG( format, false, wxT("invalid clipboard format") );
 543
 544     wxLogTrace(TRACE_CLIPBOARD, wxT("Checking if format %s is available"),
 545                format.GetId().c_str());
 546
 547     // these variables will be used by our GTKOnTargetReceived()
 548     m_targetRequested = format;
 549     m_formatSupported = false;
 550
 551     // block until m_formatSupported is set from targets_selection_received
 552     // callback
 553     {
 554         wxClipboardSync sync(*this);
 555
 556         gtk_selection_convert( m_targetsWidget,
 557                                GTKGetClipboardAtom(),
 558                                g_targetsAtom,
 559                                (guint32) GDK_CURRENT_TIME );
 560     }
 561
 562     return m_formatSupported;
 563 }
 564
 565 // ----------------------------------------------------------------------------
 566 // wxClipboard public API implementation
 567 // ----------------------------------------------------------------------------
 568
 569 void wxClipboard::Clear()
 570 {
 571     if ( gdk_selection_owner_get(GTKGetClipboardAtom()) ==
 572             m_clipboardWidget->window )
 573     {
 574         wxClipboardSync sync(*this);
 575
 576         // this will result in selection_clear_clip callback being called and
 577         // it will free our data
 578         SetSelectionOwner(false);
 579     }
 580
 581     m_targetRequested = 0;
 582     m_formatSupported = false;
 583 }
 584
 585 bool wxClipboard::Open()
 586 {
 587     wxCHECK_MSG( !m_open, false, wxT("clipboard already open") );
 588
 589     m_open = true;
 590
 591     return true;
 592 }
 593
 594 bool wxClipboard::SetData( wxDataObject *data )
 595 {
 596     wxCHECK_MSG( m_open, false, wxT("clipboard not open") );
 597
 598     wxCHECK_MSG( data, false, wxT("data is invalid") );
 599
 600     Clear();
 601
 602     return AddData( data );
 603 }
 604
 605 bool wxClipboard::AddData( wxDataObject *data )
 606 {
 607     wxCHECK_MSG( m_open, false, wxT("clipboard not open") );
 608
 609     wxCHECK_MSG( data, false, wxT("data is invalid") );
 610
 611     // we can only store one wxDataObject so clear the old one
 612     Clear();
 613
 614     Data() = data;
 615
 616     // get formats from wxDataObjects
 617     const size_t count = data->GetFormatCount();
 618     wxDataFormatArray formats(new wxDataFormat[count]);
 619     data->GetAllFormats(formats.get());
 620
 621     // always provide TIMESTAMP as a target, see comments in selection_handler
 622     // for explanation
 623     AddSupportedTarget(g_timestampAtom);
 624
 625     for ( size_t i = 0; i < count; i++ )
 626     {
 627         const wxDataFormat format(formats[i]);
 628
 629         wxLogTrace(TRACE_CLIPBOARD, wxT("Adding support for %s"),
 630                    format.GetId().c_str());
 631
 632         AddSupportedTarget(format);
 633     }
 634
 635     g_signal_connect (m_clipboardWidget, "selection_get",
 636                       G_CALLBACK (selection_handler),
 637                       GUINT_TO_POINTER (gtk_get_current_event_time()) );
 638
 639     // tell the world we offer clipboard data
 640     return SetSelectionOwner();
 641 }
 642
 643 void wxClipboard::Close()
 644 {
 645     wxCHECK_RET( m_open, wxT("clipboard not open") );
 646
 647     m_open = false;
 648 }
 649
 650 bool wxClipboard::IsOpened() const
 651 {
 652     return m_open;
 653 }
 654
 655 bool wxClipboard::IsSupported( const wxDataFormat& format )
 656 {
 657     if ( DoIsSupported(format) )
 658         return true;
 659
 660 #if wxUSE_UNICODE
 661     if ( format == wxDF_UNICODETEXT )
 662     {
 663         // also with plain STRING format
 664         return DoIsSupported(g_altTextAtom);
 665     }
 666 #endif // wxUSE_UNICODE
 667
 668     return false;
 669 }
 670
 671 bool wxClipboard::GetData( wxDataObject& data )
 672 {
 673     wxCHECK_MSG( m_open, false, wxT("clipboard not open") );
 674
 675     // get all supported formats from wxDataObjects
 676     const size_t count = data.GetFormatCount();
 677     wxDataFormatArray formats(new wxDataFormat[count]);
 678     data.GetAllFormats(formats.get());
 679
 680     for ( size_t i = 0; i < count; i++ )
 681     {
 682         const wxDataFormat format(formats[i]);
 683
 684         // is this format supported by clipboard ?
 685         if ( !DoIsSupported(format) )
 686             continue;
 687
 688         wxLogTrace(TRACE_CLIPBOARD, wxT("Requesting format %s"),
 689                    format.GetId().c_str());
 690
 691         // these variables will be used by our GTKOnSelectionReceived()
 692         m_receivedData = &data;
 693         m_formatSupported = false;
 694
 695         {
 696             wxClipboardSync sync(*this);
 697
 698             gtk_selection_convert(m_clipboardWidget,
 699                                   GTKGetClipboardAtom(),
 700                                   format,
 701                                   (guint32) GDK_CURRENT_TIME );
 702         } // wait until we get the results
 703
 704         /*
 705            Normally this is a true error as we checked for the presence of such
 706            data before, but there are applications that may return an empty
 707            string (e.g. Gnumeric-1.6.1 on Linux if an empty cell is copied)
 708            which would produce a false error message here, so we check for the
 709            size of the string first. With ANSI, GetDataSize returns an extra
 710            value (for the closing null?), with unicode, the exact number of
 711            tokens is given (that is more than 1 for non-ASCII characters)
 712            (tested with Gnumeric-1.6.1 and OpenOffice.org-2.0.2)
 713          */
 714 #if wxUSE_UNICODE
 715         if ( format != wxDF_UNICODETEXT || data.GetDataSize(format) > 0 )
 716 #else // !UNICODE
 717         if ( format != wxDF_TEXT || data.GetDataSize(format) > 1 )
 718 #endif // UNICODE / !UNICODE
 719         {
 720             wxCHECK_MSG( m_formatSupported, false,
 721                          wxT("error retrieving data from clipboard") );
 722         }
 723
 724         return true;
 725     }
 726
 727     wxLogTrace(TRACE_CLIPBOARD, wxT("GetData(): format not found"));
 728
 729     return false;
 730 }
 731
 732 #endif // wxUSE_CLIPBOARD