wxWidgets/src/gtk1/dnd.cpp

///////////////////////////////////////////////////////////////////////////////
// Name:        dnd.cpp
// Purpose:     wxDropTarget class
// Author:      Robert Roebling
// Id:          $Id$
// Copyright:   (c) 1998 Robert Roebling
// Licence:     wxWindows licence
///////////////////////////////////////////////////////////////////////////////

#ifdef __GNUG__
#pragma implementation "dnd.h"
#endif

#include "wx/dnd.h"

#if wxUSE_DRAG_AND_DROP

#include "wx/window.h"
#include "wx/app.h"
#include "wx/gdicmn.h"
#include "wx/intl.h"
#include "wx/utils.h"

#include "gdk/gdk.h"
#include "gtk/gtk.h"
#include "gdk/gdkprivate.h"

#include "gtk/gtkdnd.h"
#include "gtk/gtkselection.h"

//-----------------------------------------------------------------------------
// idle system
//-----------------------------------------------------------------------------

extern void wxapp_install_idle_handler();
extern bool g_isIdle;

//-----------------------------------------------------------------------------
// thread system
//-----------------------------------------------------------------------------

#if wxUSE_THREADS
extern void wxapp_install_thread_wakeup();
extern void wxapp_uninstall_thread_wakeup();
#endif

//----------------------------------------------------------------------------
// global data
//----------------------------------------------------------------------------

extern bool g_blockEventsOnDrag;

//----------------------------------------------------------------------------
// standard icons
//----------------------------------------------------------------------------

/* XPM */
static char * gv_xpm[] = {
"40 34 3 1",
"         s None c None",
".        c black",
"X        c white",
"                                        ",
"                                        ",
"                  ......                ",
"                ..XXXXXX..              ",
"               .XXXXXXXXXX.             ",
"              .XXXXXXXXXXXX.            ",
"              .XXXXXXXXXXXX.            ",
"             .XXXXXXXXXXXXXX.           ",
"             .XXX..XXXX..XXX.           ",
"          ....XX....XX....XX.           ",
"         .XXX.XXX..XXXX..XXX....        ",
"        .XXXXXXXXXXXXXXXXXXX.XXX.       ",
"        .XXXXXXXXXXXXXXXXXXXXXXXX.      ",
"        .XXXXXXXXXXXXXXXXXXXXXXXX.      ",
"         ..XXXXXXXXXXXXXXXXXXXXXX.      ",
"           .XXXXXXXXXXXXXXXXXX...       ",
"           ..XXXXXXXXXXXXXXXX.          ",
"            .XXXXXXXXXXXXXXXX.          ",
"            .XXXXXXXXXXXXXXXX.          ",
"            .XXXXXXXXXXXXXXXXX.         ",
"            .XXXXXXXXXXXXXXXXX.         ",
"            .XXXXXXXXXXXXXXXXXX.        ",
"            .XXXXXXXXXXXXXXXXXXX.       ",
"           .XXXXXXXXXXXXXXXXXXXXX.      ",
"           .XXXXXXXXXXXXXX.XXXXXXX.     ",
"          .XXXXXXX.XXXXXXX.XXXXXXX.     ",
"         .XXXXXXXX.XXXXXXX.XXXXXXX.     ",
"         .XXXXXXX...XXXXX...XXXXX.      ",
"         .XXXXXXX.  .....   .....       ",
"         ..XXXX..                       ",
"           ....                         ",
"                                        ",
"                                        ",
"                                        "};

/* XPM */
static char * page_xpm[] = {
/* width height ncolors chars_per_pixel */
"32 32 5 1",
/* colors */
"         s None        c None",
".        c black",
"X        c wheat",
"o        c tan",
"O        c #6699FF",
/* pixels */
"    ...................         ",
"    .XXXXXXXXXXXXXXXXX..        ",
"    .XXXXXXXXXXXXXXXXX.o.       ",
"    .XXXXXXXXXXXXXXXXX.oo.      ",
"    .XXXXXXXXXXXXXXXXX.ooo.     ",
"    .XXXXXXXXXXXXXXXXX.oooo.    ",
"    .XXXXXXXXXXXXXXXXX.......   ",
"    .XXXXXOOOOOOOOOOXXXooooo.   ",
"    .XXXXXXXXXXXXXXXXXXooooo.   ",
"    .XXXXXOOOOOOOOOOXXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXXOOOOOOOOOXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXOOOOOOOOOOXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXOOOOOOOOOOXXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXXOOOOOOOOOXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXOOOOOOOOOOXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXOOOOOOOOOOXXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXOOOOOOOOOOXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXOOOOOOOXXXXXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .XXXXXXXXXXXXXXXXXXXXXXX.   ",
"    .........................   "};



// ----------------------------------------------------------------------------
// "drag_leave"
// ----------------------------------------------------------------------------

static void target_drag_leave( GtkWidget *WXUNUSED(widget),
                               GdkDragContext *context,
                               guint WXUNUSED(time),
                               wxDropTarget *drop_target )
{
    if (g_isIdle) wxapp_install_idle_handler();

    /* inform the wxDropTarget about the current GdkDragContext.
       this is only valid for the duration of this call */
    drop_target->SetDragContext( context );

    /* we don't need return values. this event is just for
       information */
    drop_target->OnLeave();

    /* this has to be done because GDK has no "drag_enter" event */
    drop_target->m_firstMotion = TRUE;

    /* after this, invalidate the drop_target's GdkDragContext */
    drop_target->SetDragContext( (GdkDragContext*) NULL );
}

// ----------------------------------------------------------------------------
// "drag_motion"
// ----------------------------------------------------------------------------

static gboolean target_drag_motion( GtkWidget *WXUNUSED(widget),
                                    GdkDragContext *context,
                                    gint x,
                                    gint y,
                                    guint time,
                                    wxDropTarget *drop_target )
{
    if (g_isIdle) wxapp_install_idle_handler();

    /* Owen Taylor: "if the coordinates not in a drop zone,
       return FALSE, otherwise call gtk_drag_status() and
       return TRUE" */

    /* inform the wxDropTarget about the current GdkDragContext.
       this is only valid for the duration of this call */
    drop_target->SetDragContext( context );

    /* TODO: what should be the default behaviour? Copy or move? */
    wxDragResult result = wxDragMove;

    if (drop_target->m_firstMotion)
    {
        /* the first "drag_motion" event substitutes a "drag_enter" event */
        result = drop_target->OnEnter( x, y, result );
    }
    else
    {
        /* give program a chance to react (i.e. to say no by returning FALSE) */
        result = drop_target->OnDragOver( x, y, result );
    }

    /* we don't yet handle which "actions" (i.e. copy or move)
       the target accepts. so far we simply accept the
       suggested action. TODO. */
    bool ret = result != wxDragNone;
    if (ret)
        gdk_drag_status( context, context->suggested_action, time );

    /* after this, invalidate the drop_target's GdkDragContext */
    drop_target->SetDragContext( (GdkDragContext*) NULL );

    /* this has to be done because GDK has no "drag_enter" event */
    drop_target->m_firstMotion = FALSE;

    return ret;
}

// ----------------------------------------------------------------------------
// "drag_drop"
// ----------------------------------------------------------------------------

static gboolean target_drag_drop( GtkWidget *widget,
                                  GdkDragContext *context,
                                  gint x,
                                  gint y,
                                  guint time,
                                  wxDropTarget *drop_target )
{
    if (g_isIdle) wxapp_install_idle_handler();

    /* Owen Taylor: "if the drop is not in a drop zone,
       return FALSE, otherwise, if you aren't accepting
       the drop, call gtk_drag_finish() with success == FALSE
       otherwise call gtk_drag_data_get()" */

//    printf( "drop.\n" );

    /* this seems to make a difference between not accepting
       due to wrong target area and due to wrong format. let
       us hope that this is not required.. */

    /* inform the wxDropTarget about the current GdkDragContext.
       this is only valid for the duration of this call */
    drop_target->SetDragContext( context );

    /* inform the wxDropTarget about the current drag widget.
       this is only valid for the duration of this call */
    drop_target->SetDragWidget( widget );

    /* inform the wxDropTarget about the current drag time.
       this is only valid for the duration of this call */
    drop_target->SetDragTime( time );

    bool ret = drop_target->OnDrop( x, y );

    if (!ret)
    {
        wxLogDebug( wxT( "Drop target: OnDrop returned TRUE") );
	
        /* cancel the whole thing */
        gtk_drag_finish( context,
                          FALSE,        /* no success */
                          FALSE,        /* don't delete data on dropping side */
                          time );
    }
    else
    {
        wxLogDebug( wxT( "Drop target: OnDrop returned TRUE") );
	
#if wxUSE_THREADS
        /* disable GUI threads */
        wxapp_uninstall_thread_wakeup();
#endif

        GdkAtom format = drop_target->GetMatchingPair();
	wxASSERT( format );
	
        /* this should trigger an "drag_data_received" event */
        gtk_drag_get_data( widget,
                           context,
                           format,
                           time );

#if wxUSE_THREADS
        /* re-enable GUI threads */
        wxapp_install_thread_wakeup();
#endif
    }

    /* after this, invalidate the drop_target's GdkDragContext */
    drop_target->SetDragContext( (GdkDragContext*) NULL );

    /* after this, invalidate the drop_target's drag widget */
    drop_target->SetDragWidget( (GtkWidget*) NULL );

    /* this has to be done because GDK has no "drag_enter" event */
    drop_target->m_firstMotion = TRUE;

    return ret;
}

// ----------------------------------------------------------------------------
// "drag_data_received"
// ----------------------------------------------------------------------------

static void target_drag_data_received( GtkWidget *WXUNUSED(widget),
                                       GdkDragContext *context,
                                       gint x,
                                       gint y,
                                       GtkSelectionData *data,
                                       guint WXUNUSED(info),
                                       guint time,
                                       wxDropTarget *drop_target )
{
    if (g_isIdle) wxapp_install_idle_handler();

    /* Owen Taylor: "call gtk_drag_finish() with
       success == TRUE" */


    if ((data->length <= 0) || (data->format != 8))
    {
        /* negative data length and non 8-bit data format
           qualifies for junk */
        gtk_drag_finish (context, FALSE, FALSE, time);

        return;
    }

    wxLogDebug( wxT( "Drop target: data received event") );
    
    /* inform the wxDropTarget about the current GtkSelectionData.
       this is only valid for the duration of this call */
    drop_target->SetDragData( data );

    if (drop_target->OnData( x, y ))
    {
        wxLogDebug( wxT( "Drop target: OnData returned TRUE") );
	
        /* tell GTK that data transfer was successfull */
        gtk_drag_finish( context, TRUE, FALSE, time );
    }
    else
    {
        wxLogDebug( wxT( "Drop target: OnData returned FALSE") );
	
        /* tell GTK that data transfer was not successfull */
        gtk_drag_finish( context, FALSE, FALSE, time );
    }

    /* after this, invalidate the drop_target's drag data */
    drop_target->SetDragData( (GtkSelectionData*) NULL );
}

//----------------------------------------------------------------------------
// wxDropTarget
//----------------------------------------------------------------------------

wxDropTarget::wxDropTarget( wxDataObject *data ) 
  : wxDropTargetBase( data )
{
    m_firstMotion = TRUE;
    m_dragContext = (GdkDragContext*) NULL;
    m_dragWidget = (GtkWidget*) NULL;
    m_dragData = (GtkSelectionData*) NULL;
    m_dragTime = 0;
}

wxDragResult wxDropTarget::OnDragOver( wxCoord WXUNUSED(x),
                                       wxCoord WXUNUSED(y),
                                       wxDragResult def )
{
    if (!m_dataObject)
        return FALSE;
	
    return (GetMatchingPair() != (GdkAtom) 0) ? def : wxDragNone;
}

bool wxDropTarget::OnDrop( wxCoord WXUNUSED(x), wxCoord WXUNUSED(y) )
{
    if (!m_dataObject)
        return FALSE;
	
    return (GetMatchingPair() != (GdkAtom) 0);
}

bool wxDropTarget::OnData( wxCoord WXUNUSED(x), wxCoord WXUNUSED(y) )
{
    if (!m_dataObject)
        return FALSE;
	
    if (GetMatchingPair() == (GdkAtom) 0)
        return FALSE;
	
    return GetData();
}

GdkAtom wxDropTarget::GetMatchingPair()
{
    if (!m_dataObject) 
        return (GdkAtom) 0;

    if (!m_dragContext) 
        return (GdkAtom) 0;

    GList *child = m_dragContext->targets;
    while (child)
    {
        GdkAtom formatAtom = (GdkAtom) GPOINTER_TO_INT(child->data);
	wxDataFormat format( formatAtom );

#ifdef __WXDEBUG__
        char *name = gdk_atom_name( formatAtom );
        if (name) wxLogDebug( "Drop target: drag has format: %s", name );
#endif
        if (m_dataObject->IsSupportedFormat( format ))
	    return formatAtom;

        child = child->next;
    }

    return (GdkAtom) 0;
}

bool wxDropTarget::GetData()
{
    if (!m_dragData) 
        return FALSE;

    if (!m_dataObject) 
        return FALSE;

    wxDataFormat dragFormat( m_dragData->target );
    
    if (!m_dataObject->IsSupportedFormat( dragFormat ))
        return FALSE;

    if (dragFormat.GetType() == wxDF_TEXT)
    {
        wxTextDataObject *text_object = (wxTextDataObject*)m_dataObject;
        text_object->SetText( (const char*)m_dragData->data );
	return TRUE;
    }

    if (dragFormat.GetType() == wxDF_FILENAME)
    {
        wxFileDataObject *file_object = (wxFileDataObject*)m_dataObject;
        file_object->SetData( 0, (const char*)m_dragData->data );
	return TRUE;
    }

    m_dataObject->SetData( dragFormat, (size_t)m_dragData->length, (const void*)m_dragData->data );

    return TRUE;
}

void wxDropTarget::UnregisterWidget( GtkWidget *widget )
{
    wxCHECK_RET( widget != NULL, wxT("unregister widget is NULL") );

    gtk_drag_dest_unset( widget );

    gtk_signal_disconnect_by_func( GTK_OBJECT(widget),
                      GTK_SIGNAL_FUNC(target_drag_leave), (gpointer) this );

    gtk_signal_disconnect_by_func( GTK_OBJECT(widget),
                      GTK_SIGNAL_FUNC(target_drag_motion), (gpointer) this );

    gtk_signal_disconnect_by_func( GTK_OBJECT(widget),
                      GTK_SIGNAL_FUNC(target_drag_drop), (gpointer) this );

    gtk_signal_disconnect_by_func( GTK_OBJECT(widget),
                      GTK_SIGNAL_FUNC(target_drag_data_received), (gpointer) this );
}

void wxDropTarget::RegisterWidget( GtkWidget *widget )
{
    wxCHECK_RET( widget != NULL, wxT("register widget is NULL") );

    /* gtk_drag_dest_set() determines what default behaviour we'd like
       GTK to supply. we don't want to specify out targets (=formats)
       or actions in advance (i.e. not GTK_DEST_DEFAULT_MOTION and
       not GTK_DEST_DEFAULT_DROP). instead we react individually to
       "drag_motion" and "drag_drop" events. this makes it possible
       to allow dropping on only a small area. we should set
       GTK_DEST_DEFAULT_HIGHLIGHT as this will switch on the nice
       highlighting if dragging over standard controls, but this
       seems to be broken without the other two. */

    gtk_drag_dest_set( widget,
                       (GtkDestDefaults) 0,         /* no default behaviour */
                       (GtkTargetEntry*) NULL,      /* we don't supply any formats here */
                       0,                           /* number of targets = 0 */
                       (GdkDragAction) 0 );         /* we don't supply any actions here */

    gtk_signal_connect( GTK_OBJECT(widget), "drag_leave",
                      GTK_SIGNAL_FUNC(target_drag_leave), (gpointer) this );

    gtk_signal_connect( GTK_OBJECT(widget), "drag_motion",
                      GTK_SIGNAL_FUNC(target_drag_motion), (gpointer) this );

    gtk_signal_connect( GTK_OBJECT(widget), "drag_drop",
                      GTK_SIGNAL_FUNC(target_drag_drop), (gpointer) this );

    gtk_signal_connect( GTK_OBJECT(widget), "drag_data_received",
                      GTK_SIGNAL_FUNC(target_drag_data_received), (gpointer) this );
}

// ----------------------------------------------------------------------------
// wxTextDropTarget
// ----------------------------------------------------------------------------

wxTextDropTarget::wxTextDropTarget()
                : wxDropTarget(new wxTextDataObject)
{
}

bool wxTextDropTarget::OnData(wxCoord x, wxCoord y)
{
    if ( !GetData() )
        return FALSE;

    return OnDropText(x, y, ((wxTextDataObject *)m_dataObject)->GetText());
}

// ----------------------------------------------------------------------------
// wxFileDropTarget
// ----------------------------------------------------------------------------

wxFileDropTarget::wxFileDropTarget()
                : wxDropTarget(new wxFileDataObject)
{
}

bool wxFileDropTarget::OnData(wxCoord x, wxCoord y)
{
    if ( !GetData() )
        return FALSE;

    return OnDropFiles(x, y,
                       ((wxFileDataObject *)m_dataObject)->GetFilenames());
}

//----------------------------------------------------------------------------
// "drag_data_get"
//----------------------------------------------------------------------------

static void
source_drag_data_get  (GtkWidget          *WXUNUSED(widget),
                       GdkDragContext     *context,
                       GtkSelectionData   *selection_data,
                       guint               WXUNUSED(info),
                       guint               WXUNUSED(time),
                       wxDropSource       *drop_source )
{
    if (g_isIdle) wxapp_install_idle_handler();

    wxDataFormat format( selection_data->target );
    
    wxLogDebug( wxT("Drop source: format requested: %s"), format.GetId().c_str() );

    drop_source->m_retValue = wxDragCancel;
    
    wxDataObject *data = drop_source->GetDataObject();
    
    if (!data)
    {
        wxLogDebug( wxT("Drop source: no data object") );
	return;
    }

    if (!data->IsSupportedFormat(format))
    {
        wxLogDebug( wxT("Drop source: unsupported format") );
	return;
    }

    if (data->GetDataSize(format) == 0)
    {
        wxLogDebug( wxT("Drop source: empty data") );
	return;
    }
    
    size_t size = data->GetDataSize(format);

//  printf( "data size: %d.\n", (int)data_size );

    guchar *d = new guchar[size];
    
    if (!data->GetDataHere( format, (void*)d ))
    {
        delete[] d;
	return;
    }

#if wxUSE_THREADS
    /* disable GUI threads */
    wxapp_uninstall_thread_wakeup();
#endif

                gtk_selection_data_set( selection_data,
                                        selection_data->target,
                                        8,   // 8-bit
                                        d,
                                        size );

#if wxUSE_THREADS
    /* enable GUI threads */
    wxapp_install_thread_wakeup();
#endif

    delete[] d;
    
    /* so far only copy, no moves. TODO. */
    drop_source->m_retValue = wxDragCopy;
}

//----------------------------------------------------------------------------
// "drag_data_delete"
//----------------------------------------------------------------------------

static void source_drag_data_delete( GtkWidget          *WXUNUSED(widget),
                                     GdkDragContext     *WXUNUSED(context),
                                     wxDropSource       *drop_source )
{
    if (g_isIdle) wxapp_install_idle_handler();

//  printf( "Delete the data!\n" );

    drop_source->m_retValue = wxDragMove;
}

//----------------------------------------------------------------------------
// "drag_begin"
//----------------------------------------------------------------------------

static void source_drag_begin( GtkWidget          *WXUNUSED(widget),
                               GdkDragContext     *WXUNUSED(context),
                               wxDropSource       *WXUNUSED(drop_source) )
{
    if (g_isIdle) wxapp_install_idle_handler();

//  printf( "drag_begin.\n" );
}

//----------------------------------------------------------------------------
// "drag_end"
//----------------------------------------------------------------------------

static void source_drag_end( GtkWidget          *WXUNUSED(widget),
                             GdkDragContext     *WXUNUSED(context),
                             wxDropSource       *drop_source )
{
    if (g_isIdle) wxapp_install_idle_handler();

//  printf( "drag_end.\n" );

    drop_source->m_waiting = FALSE;
}

//---------------------------------------------------------------------------
// wxDropSource
//---------------------------------------------------------------------------

wxDropSource::wxDropSource( wxWindow *win, const wxIcon &go, const wxIcon &stop )
{
    g_blockEventsOnDrag = TRUE;
    m_waiting = TRUE;

    m_window = win;
    m_widget = win->m_widget;
    if (win->m_wxwindow) m_widget = win->m_wxwindow;

    m_retValue = wxDragCancel;

    m_defaultCursor = wxCursor( wxCURSOR_NO_ENTRY );
    m_goaheadCursor = wxCursor( wxCURSOR_HAND );

    m_goIcon = go;
    if (wxNullIcon == go) m_goIcon = wxIcon( page_xpm );
    m_stopIcon = stop;
    if (wxNullIcon == stop) m_stopIcon = wxIcon( gv_xpm );
}

wxDropSource::wxDropSource( wxDataObject& data, wxWindow *win,
                            const wxIcon &go, const wxIcon &stop )
{
    m_waiting = TRUE;
    
    SetData( data );

    m_window = win;
    m_widget = win->m_widget;
    if (win->m_wxwindow) m_widget = win->m_wxwindow;
    m_retValue = wxDragCancel;

    m_defaultCursor = wxCursor( wxCURSOR_NO_ENTRY );
    m_goaheadCursor = wxCursor( wxCURSOR_HAND );

    m_goIcon = go;
    if (wxNullIcon == go) m_goIcon = wxIcon( page_xpm );
    m_stopIcon = stop;
    if (wxNullIcon == stop) m_stopIcon = wxIcon( gv_xpm );
}

wxDropSource::~wxDropSource()
{
    g_blockEventsOnDrag = FALSE;
}

wxDragResult wxDropSource::DoDragDrop( bool WXUNUSED(bAllowMove) )
{
    wxASSERT_MSG( m_data, wxT("wxDragSource: no data") );

    if (!m_data) 
        return (wxDragResult) wxDragNone;

    if (m_data->GetFormatCount() == 0) 
        return (wxDragResult) wxDragNone;
	
    g_blockEventsOnDrag = TRUE;

    RegisterWindow();

    m_waiting = TRUE;

    GtkTargetList *target_list = gtk_target_list_new( (GtkTargetEntry*) NULL, 0 );
    
    wxDataFormat *array = new wxDataFormat[ m_data->GetFormatCount() ];
    m_data->GetAllFormats( array );
    for (size_t i = 0; i < m_data->GetFormatCount(); i++)
    {
        GdkAtom atom = array[i];
	wxLogDebug( wxT("Supported atom %s"), gdk_atom_name( atom ) );
        gtk_target_list_add( target_list, atom, 0, 0 );
    }
    delete[] array;

    GdkEventMotion event;
    event.window = m_widget->window;
    int x = 0;
    int y = 0;
    GdkModifierType state;
    gdk_window_get_pointer( event.window, &x, &y, &state );
    event.x = x;
    event.y = y;
    event.state = state;
    event.time = GDK_CURRENT_TIME;

    /* GTK wants to know which button was pressed which caused the dragging */
    int button_number = 0;
    if (event.state & GDK_BUTTON1_MASK) button_number = 1;
    else if (event.state & GDK_BUTTON2_MASK) button_number = 2;
    else if (event.state & GDK_BUTTON3_MASK) button_number = 3;

#if wxUSE_THREADS
    /* disable GUI threads */
    wxapp_uninstall_thread_wakeup();
#endif

    /* don't start dragging if no button is down */
    if (button_number)
    {
        GdkDragContext *context = gtk_drag_begin( m_widget,
                                              target_list,
                                              GDK_ACTION_COPY,
                                              button_number,  /* number of mouse button which started drag */
                                              (GdkEvent*) &event );

        wxMask *mask = m_goIcon.GetMask();
        GdkBitmap *bm = (GdkBitmap *) NULL;
        if (mask) bm = mask->GetBitmap();
        GdkPixmap *pm = m_goIcon.GetPixmap();

        gtk_drag_set_icon_pixmap( context,
                                  gtk_widget_get_colormap( m_widget ),
                                  pm,
                                  bm,
                                  0,
                                  0 );

        while (m_waiting) gtk_main_iteration();;
    }

#if wxUSE_THREADS
    /* re-enable GUI threads */
    wxapp_install_thread_wakeup();
#endif

    g_blockEventsOnDrag = FALSE;

    UnregisterWindow();

    return m_retValue;
}

void wxDropSource::RegisterWindow()
{
    if (!m_widget) return;

    gtk_signal_connect( GTK_OBJECT(m_widget), "drag_data_get",
                      GTK_SIGNAL_FUNC (source_drag_data_get), (gpointer) this);
    gtk_signal_connect (GTK_OBJECT(m_widget), "drag_data_delete",
                      GTK_SIGNAL_FUNC (source_drag_data_delete),  (gpointer) this );
    gtk_signal_connect (GTK_OBJECT(m_widget), "drag_begin",
                      GTK_SIGNAL_FUNC (source_drag_begin),  (gpointer) this );
    gtk_signal_connect (GTK_OBJECT(m_widget), "drag_end",
                      GTK_SIGNAL_FUNC (source_drag_end),  (gpointer) this );

}

void wxDropSource::UnregisterWindow()
{
    if (!m_widget) return;

    gtk_signal_disconnect_by_func( GTK_OBJECT(m_widget),
                      GTK_SIGNAL_FUNC(source_drag_data_get), (gpointer) this );
    gtk_signal_disconnect_by_func( GTK_OBJECT(m_widget),
                      GTK_SIGNAL_FUNC(source_drag_data_delete), (gpointer) this );
    gtk_signal_disconnect_by_func( GTK_OBJECT(m_widget),
                      GTK_SIGNAL_FUNC(source_drag_begin), (gpointer) this );
    gtk_signal_disconnect_by_func( GTK_OBJECT(m_widget),
                      GTK_SIGNAL_FUNC(source_drag_end), (gpointer) this );
}

#endif

      // wxUSE_DRAG_AND_DROP