gdkdnd-win32.c

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/* GDK - The GIMP Drawing Kit
 * Copyright (C) 1995-1999 Peter Mattis, Spencer Kimball and Josh MacDonald
 * Copyright (C) 1998-1999 Tor Lillqvist
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/*
 * Modified by the GTK+ Team and others 1997-1999.  See the AUTHORS
 * file for a list of people on the GTK+ Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
 * GTK+ at ftp://ftp.gtk.org/pub/gtk/. 
 */

#include "config.h"

#include <string.h>

/* #define OLE2_DND */

#define INITGUID

#include "gdkdnd.h"
#include "gdkproperty.h"
#include "gdkprivate.h"
#include "gdkwin32.h"

#ifdef OLE2_DND
#include <ole2.h>
#else
#include <objbase.h>
#endif

#include <shlobj.h>
#include <shlguid.h>

#include <gdk/gdk.h>

typedef struct _GdkDragContextPrivate GdkDragContextPrivate;

typedef enum {
   GDK_DRAG_STATUS_DRAG,
   GDK_DRAG_STATUS_MOTION_WAIT,
   GDK_DRAG_STATUS_ACTION_WAIT,
   GDK_DRAG_STATUS_DROP
} GtkDragStatus;

typedef enum {
   GDK_DRAG_SOURCE,
   GDK_DRAG_TARGET
} GdkDragKind;

#ifdef OLE2_DND

#define PRINT_GUID(guid) \
  g_print ("guid = %.08x-%.04x-%.04x-%.02x%.02x-%.02x%.02x%.02x%.02x%.02x%.02x", \
           ((gulong *)  guid)[0], \
           ((gushort *) guid)[2], \
           ((gushort *) guid)[3], \
           ((guchar *)  guid)[8], \
           ((guchar *)  guid)[9], \
           ((guchar *)  guid)[10], \
           ((guchar *)  guid)[11], \
           ((guchar *)  guid)[12], \
           ((guchar *)  guid)[13], \
           ((guchar *)  guid)[14], \
           ((guchar *)  guid)[15]);


#endif                          /* OLE2_DND */

/* Structure that holds information about a drag in progress.
 * this is used on both source and destination sides.
 */
struct _GdkDragContextPrivate {
   GdkDragContext context;

   guint ref_count;

   guint16 last_x;              /* Coordinates from last event */
   guint16 last_y;
   HWND dest_xid;
   guint drag_status;           /* Current status of drag */
};

GdkDragContext *current_dest_drag = NULL;

/* Drag Contexts */

static GList *contexts;

GdkDragContext *gdk_drag_context_new(void)
{
   GdkDragContextPrivate *result;

   result = g_new0(GdkDragContextPrivate, 1);

   result->ref_count = 1;

   contexts = g_list_prepend(contexts, result);

   return (GdkDragContext *) result;
}

void gdk_drag_context_ref(GdkDragContext * context)
{
   g_return_if_fail(context != NULL);

   ((GdkDragContextPrivate *) context)->ref_count++;
}

void gdk_drag_context_unref(GdkDragContext * context)
{
   GdkDragContextPrivate *private = (GdkDragContextPrivate *) context;

   g_return_if_fail(context != NULL);

   private->ref_count--;

   GDK_NOTE(DND, g_print("gdk_drag_context_unref: %d%s\n",
                         private->ref_count,
                         (private->ref_count == 0 ? " freeing" : "")));

   if (private->ref_count == 0) {
      g_dataset_destroy(private);

      g_list_free(context->targets);

      if (context->source_window)
         gdk_window_unref(context->source_window);

      if (context->dest_window)
         gdk_window_unref(context->dest_window);

      contexts = g_list_remove(contexts, private);
      g_free(private);
   }
}

#if 0

static GdkDragContext *gdk_drag_context_find(gboolean is_source,
                                             HWND source_xid,
                                             HWND dest_xid)
{
   GList *tmp_list = contexts;
   GdkDragContext *context;

   while (tmp_list) {
      context = (GdkDragContext *) tmp_list->data;

      if ((!context->is_source == !is_source) &&
          ((source_xid == None) || (context->source_window &&
                                    (GDK_WINDOW_XWINDOW
                                     (context->source_window) ==
                                     source_xid))) && ((dest_xid == None)
                                                       || (context->
                                                           dest_window
                                                           &&
                                                           (GDK_WINDOW_XWINDOW
                                                            (context->
                                                             dest_window)
                                                            == dest_xid))))
         return context;

      tmp_list = tmp_list->next;
   }

   return NULL;
}

#endif

typedef struct {
#ifdef OLE2_DND
   IDropTarget idt;
#endif
   GdkDragContext *context;
} target_drag_context;

typedef struct {
#ifdef OLE2_DND
   IDropSource ids;
#endif
   GdkDragContext *context;
} source_drag_context;

#ifdef OLE2_DND

static ULONG STDMETHODCALLTYPE
m_add_ref_target(IDropTarget __RPC_FAR * This)
{
   target_drag_context *ctx = (target_drag_context *) This;
   GdkDragContextPrivate *private = (GdkDragContextPrivate *) ctx->context;

   GDK_NOTE(DND, g_print("m_add_ref_target\n"));
   gdk_drag_context_ref(ctx->context);

   return private->ref_count;
}

static HRESULT STDMETHODCALLTYPE
m_query_interface_target(IDropTarget __RPC_FAR * This,
                         REFIID riid,
                         void __RPC_FAR * __RPC_FAR * ppvObject)
{
   GDK_NOTE(DND, g_print("m_query_interface_target\n"));

   *ppvObject = NULL;

   PRINT_GUID(riid);

   if (IsEqualGUID(riid, &IID_IUnknown)) {
      g_print("...IUnknown\n");
      m_add_ref_target(This);
      *ppvObject = This;
      return S_OK;
   } else if (IsEqualGUID(riid, &IID_IDropTarget)) {
      g_print("...IDropTarget\n");
      m_add_ref_target(This);
      *ppvObject = This;
      return S_OK;
   } else {
      g_print("...Huh?\n");
      return E_NOINTERFACE;
   }
}

static ULONG STDMETHODCALLTYPE
m_release_target(IDropTarget __RPC_FAR * This)
{
   target_drag_context *ctx = (target_drag_context *) This;
   GdkDragContextPrivate *private = (GdkDragContextPrivate *) ctx->context;

   GDK_NOTE(DND, g_print("m_release_target\n"));
   gdk_drag_context_unref(ctx->context);

   if (private->ref_count == 1) {
      gdk_drag_context_unref(ctx->context);
      return 0;
   } else
      return private->ref_count - 1;
}

static HRESULT STDMETHODCALLTYPE
m_drag_enter(IDropTarget __RPC_FAR * This,
             IDataObject __RPC_FAR * pDataObj,
             DWORD grfKeyState, POINTL pt, DWORD __RPC_FAR * pdwEffect)
{
   GDK_NOTE(DND, g_print("m_drag_enter\n"));
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_drag_over(IDropTarget __RPC_FAR * This,
            DWORD grfKeyState, POINTL pt, DWORD __RPC_FAR * pdwEffect)
{
   GDK_NOTE(DND, g_print("m_drag_over\n"));
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE m_drag_leave(IDropTarget __RPC_FAR * This)
{
   GDK_NOTE(DND, g_print("m_drag_leave\n"));
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_drop(IDropTarget __RPC_FAR * This,
       IDataObject __RPC_FAR * pDataObj,
       DWORD grfKeyState, POINTL pt, DWORD __RPC_FAR * pdwEffect)
{
   GDK_NOTE(DND, g_print("m_drop\n"));
   return E_UNEXPECTED;
}

static ULONG STDMETHODCALLTYPE
m_add_ref_source(IDropSource __RPC_FAR * This)
{
   source_drag_context *ctx = (source_drag_context *) This;
   GdkDragContextPrivate *private = (GdkDragContextPrivate *) ctx->context;

   GDK_NOTE(DND, g_print("m_add_ref_source\n"));
   gdk_drag_context_ref(ctx->context);

   return private->ref_count;
}

static HRESULT STDMETHODCALLTYPE
m_query_interface_source(IDropSource __RPC_FAR * This,
                         REFIID riid,
                         void __RPC_FAR * __RPC_FAR * ppvObject)
{
   GDK_NOTE(DND, g_print("m_query_interface_source\n"));

   *ppvObject = NULL;

   PRINT_GUID(riid);
   if (IsEqualGUID(riid, &IID_IUnknown)) {
      g_print("...IUnknown\n");
      m_add_ref_source(This);
      *ppvObject = This;
      return S_OK;
   } else if (IsEqualGUID(riid, &IID_IDropSource)) {
      g_print("...IDropSource\n");
      m_add_ref_source(This);
      *ppvObject = This;
      return S_OK;
   } else {
      g_print("...Huh?\n");
      return E_NOINTERFACE;
   }
}

static ULONG STDMETHODCALLTYPE
m_release_source(IDropSource __RPC_FAR * This)
{
   source_drag_context *ctx = (source_drag_context *) This;
   GdkDragContextPrivate *private = (GdkDragContextPrivate *) ctx->context;

   GDK_NOTE(DND, g_print("m_release_source\n"));
   gdk_drag_context_unref(ctx->context);

   if (private->ref_count == 1) {
      gdk_drag_context_unref(ctx->context);
      return 0;
   } else
      return private->ref_count - 1;
}

static HRESULT STDMETHODCALLTYPE
m_query_continue_drag(IDropSource __RPC_FAR * This,
                      BOOL fEscapePressed, DWORD grfKeyState)
{
   GDK_NOTE(DND, g_print("m_query_continue_drag\n"));
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_give_feedback(IDropSource __RPC_FAR * This, DWORD dwEffect)
{
   GDK_NOTE(DND, g_print("m_give_feedback\n"));
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_query_interface_object(IDataObject __RPC_FAR * This,
                         REFIID riid,
                         void __RPC_FAR * __RPC_FAR * ppvObject)
{
   return E_UNEXPECTED;
}

static ULONG STDMETHODCALLTYPE
m_add_ref_object(IDataObject __RPC_FAR * This)
{
   return E_UNEXPECTED;
}

static ULONG STDMETHODCALLTYPE
m_release_object(IDataObject __RPC_FAR * This)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_get_data(IDataObject __RPC_FAR * This,
           FORMATETC * pFormatEtc, STGMEDIUM * pMedium)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_get_data_here(IDataObject __RPC_FAR * This,
                FORMATETC * pFormatEtc, STGMEDIUM * pMedium)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_query_get_data(IDataObject __RPC_FAR * This, FORMATETC * pFormatEtc)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_get_canonical_format_etc(IDataObject __RPC_FAR * This,
                           FORMATETC * pFormatEtcIn,
                           FORMATETC * pFormatEtcOut)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_set_data(IDataObject __RPC_FAR * This,
           FORMATETC * pFormatEtc, STGMEDIUM * pMedium, BOOL fRelease)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_enum_format_etc(IDataObject __RPC_FAR * This,
                  DWORD dwDirection, IEnumFORMATETC ** ppEnumFormatEtc)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_d_advise(IDataObject __RPC_FAR * This,
           FORMATETC * pFormatetc,
           DWORD advf, IAdviseSink * pAdvSink, DWORD * pdwConnection)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_d_unadvise(IDataObject __RPC_FAR * This, DWORD dwConnection)
{
   return E_UNEXPECTED;
}

static HRESULT STDMETHODCALLTYPE
m_enum_d_advise(IDataObject __RPC_FAR * This,
                IEnumSTATDATA ** ppenumAdvise)
{
   return E_UNEXPECTED;
}

static IDropTargetVtbl idt_vtbl = {
   m_query_interface_target,
   m_add_ref_target,
   m_release_target,
   m_drag_enter,
   m_drag_over,
   m_drag_leave,
   m_drop
};

static IDropSourceVtbl ids_vtbl = {
   m_query_interface_source,
   m_add_ref_source,
   m_release_source,
   m_query_continue_drag,
   m_give_feedback
};

static IDataObjectVtbl ido_vtbl = {
   m_query_interface_object,
   m_add_ref_object,
   m_release_object,
   m_get_data,
   m_get_data_here,
   m_query_get_data,
   m_get_canonical_format_etc,
   m_set_data,
   m_enum_format_etc,
   m_d_advise,
   m_d_unadvise,
   m_enum_d_advise
};

#endif                          /* OLE2_DND */

static target_drag_context *target_context_new(void)
{
   target_drag_context *result;

   result = g_new0(target_drag_context, 1);

#ifdef OLE2_DND
   result->idt.lpVtbl = &idt_vtbl;
#endif

   result->context = gdk_drag_context_new();

   return result;
}

static source_drag_context *source_context_new(void)
{
   source_drag_context *result;

   result = g_new0(source_drag_context, 1);

#ifdef OLE2_DND
   result->ids.lpVtbl = &ids_vtbl;
#endif

   result->context = gdk_drag_context_new();

   return result;
}

/* From MS Knowledge Base article Q130698 */

/* resolve_link() fills the filename and path buffer
 * with relevant information
 * hWnd         - calling app's window handle.
 *
 * lpszLinkName - name of the link file passed into the function.
 *
 * lpszPath     - the buffer that will receive the file pathname.
 */

static HRESULT
resolve_link(HWND hWnd,
             LPCTSTR lpszLinkName, LPSTR lpszPath, LPSTR lpszDescription)
{
   HRESULT hres;
   IShellLink *psl;
   WIN32_FIND_DATA wfd;

   /* Assume Failure to start with: */
   *lpszPath = 0;
   if (lpszDescription)
      *lpszDescription = 0;

   /* Call CoCreateInstance to obtain the IShellLink interface
    * pointer. This call fails if CoInitialize is not called, so it is
    * assumed that CoInitialize has been called.
    */

   hres = CoCreateInstance(&CLSID_ShellLink,
                           NULL,
                           CLSCTX_INPROC_SERVER,
                           &IID_IShellLink, (LPVOID *) & psl);
   if (SUCCEEDED(hres)) {
      IPersistFile *ppf;

      /* The IShellLink interface supports the IPersistFile
       * interface. Get an interface pointer to it.
       */
      hres = psl->lpVtbl->QueryInterface(psl,
                                         &IID_IPersistFile,
                                         (LPVOID *) & ppf);
      if (SUCCEEDED(hres)) {
         WORD wsz[MAX_PATH];

         /* Convert the given link name string to wide character string. */
         MultiByteToWideChar(CP_ACP, 0, lpszLinkName, -1, wsz, MAX_PATH);
         /* Load the file. */
         hres = ppf->lpVtbl->Load(ppf, wsz, STGM_READ);
         if (SUCCEEDED(hres)) {
            /* Resolve the link by calling the Resolve()
             * interface function.
             */
            hres = psl->lpVtbl->Resolve(psl, hWnd,
                                        SLR_ANY_MATCH | SLR_NO_UI);
            if (SUCCEEDED(hres)) {
               hres = psl->lpVtbl->GetPath(psl, lpszPath,
                                           MAX_PATH,
                                           (WIN32_FIND_DATA *) & wfd, 0);

               if (SUCCEEDED(hres) && lpszDescription != NULL) {
                  hres = psl->lpVtbl->GetDescription(psl,
                                                     lpszDescription,
                                                     MAX_PATH);

                  if (!SUCCEEDED(hres))
                     return FALSE;
               }
            }
         }
         ppf->lpVtbl->Release(ppf);
      }
      psl->lpVtbl->Release(psl);
   }
   return SUCCEEDED(hres);
}

static GdkFilterReturn
gdk_dropfiles_filter(GdkXEvent * xev, GdkEvent * event, gpointer data)
{
   GdkDragContext *context;
   GdkDragContextPrivate *private;
   static GdkAtom text_uri_list_atom = GDK_NONE;
   GString *result;
   MSG *msg = (MSG *) xev;
   HANDLE hdrop;
   POINT pt;
   gint nfiles, i, k;
   guchar fileName[MAX_PATH], linkedFile[MAX_PATH];

   if (text_uri_list_atom == GDK_NONE)
      text_uri_list_atom = gdk_atom_intern("text/uri-list", FALSE);

   if (msg->message == WM_DROPFILES) {
      GDK_NOTE(DND, g_print("WM_DROPFILES: %#x\n", msg->hwnd));

      context = gdk_drag_context_new();
      private = (GdkDragContextPrivate *) context;
      context->protocol = GDK_DRAG_PROTO_WIN32_DROPFILES;
      context->is_source = FALSE;
      context->source_window = gdk_parent_root;
      context->dest_window = event->any.window;
      gdk_window_ref(context->dest_window);
      /* WM_DROPFILES drops are always file names */
      context->targets =
          g_list_append(NULL, GUINT_TO_POINTER(text_uri_list_atom));
      current_dest_drag = context;

      event->dnd.type = GDK_DROP_START;
      event->dnd.context = current_dest_drag;
      gdk_drag_context_ref(current_dest_drag);

      hdrop = (HANDLE) msg->wParam;
      DragQueryPoint(hdrop, &pt);
      ClientToScreen(msg->hwnd, &pt);

      event->dnd.x_root = pt.x;
      event->dnd.y_root = pt.y;
      event->dnd.time = msg->time;

      nfiles = DragQueryFile(hdrop, 0xFFFFFFFF, NULL, 0);

      result = g_string_new(NULL);
      for (i = 0; i < nfiles; i++) {
         g_string_append(result, "file:");
         DragQueryFile(hdrop, i, fileName, MAX_PATH);

         /* Resolve shortcuts */
         if (resolve_link(msg->hwnd, fileName, linkedFile, NULL)) {
            g_string_append(result, linkedFile);
            GDK_NOTE(DND, g_print("...%s link to %s\n",
                                  fileName, linkedFile));
         } else {
            g_string_append(result, fileName);
            GDK_NOTE(DND, g_print("...%s\n", fileName));
         }
         g_string_append(result, "\015\012");
      }
      gdk_sel_prop_store(gdk_parent_root, text_uri_list_atom, 8,
                         result->str, result->len + 1);

      DragFinish(hdrop);

      return GDK_FILTER_TRANSLATE;
   } else
      return GDK_FILTER_CONTINUE;
}

/*************************************************************
 ************************** Public API ***********************
 *************************************************************/

void gdk_dnd_init(void)
{
   HRESULT hres;
#ifdef OLE2_DND
   hres = OleInitialize(NULL);

   if (!SUCCEEDED(hres))
      g_error("OleInitialize failed");
#endif
}

void gdk_win32_dnd_exit(void)
{
#ifdef OLE2_DND
   OleUninitialize();
#endif
}

/* Source side */

static void gdk_drag_do_leave(GdkDragContext * context, guint32 time)
{
   if (context->dest_window) {
      GDK_NOTE(DND, g_print("gdk_drag_do_leave\n"));
      gdk_window_unref(context->dest_window);
      context->dest_window = NULL;
   }
}

GdkDragContext *gdk_drag_begin(GdkWindow * window, GList * targets)
{
   GList *tmp_list;
   source_drag_context *ctx;

   g_return_val_if_fail(window != NULL, NULL);

   GDK_NOTE(DND, g_print("gdk_drag_begin\n"));

   ctx = source_context_new();
   ctx->context->is_source = TRUE;
   ctx->context->source_window = window;
   gdk_window_ref(window);

   tmp_list = g_list_last(targets);
   ctx->context->targets = NULL;
   while (tmp_list) {
      ctx->context->targets = g_list_prepend(ctx->context->targets,
                                             tmp_list->data);
      tmp_list = tmp_list->prev;
   }

   ctx->context->actions = 0;

#if 0
   DoDragDrop(...);
#endif
   return ctx->context;
}

guint32 gdk_drag_get_protocol(guint32 xid, GdkDragProtocol * protocol)
{
   /* This isn't used */
   return 0;
}

void
gdk_drag_find_window(GdkDragContext * context,
                     GdkWindow * drag_window,
                     gint x_root,
                     gint y_root,
                     GdkWindow ** dest_window, GdkDragProtocol * protocol)
{
   GdkDragContextPrivate *private = (GdkDragContextPrivate *) context;
   GdkDrawablePrivate *drag_window_private =
       (GdkDrawablePrivate *) drag_window;
   HWND recipient;
   POINT pt;

   GDK_NOTE(DND, g_print("gdk_drag_find_window: %#x +%d+%d\n",
                         (drag_window ? GDK_DRAWABLE_XID(drag_window) : 0),
                         x_root, y_root));

   pt.x = x_root;
   pt.y = y_root;
   recipient = WindowFromPoint(pt);
   if (recipient == NULL)
      *dest_window = NULL;
   else {
      *dest_window = gdk_window_lookup(recipient);
      if (*dest_window)
         gdk_window_ref(*dest_window);
      *protocol = GDK_DRAG_PROTO_WIN32_DROPFILES;
   }
}

gboolean
gdk_drag_motion(GdkDragContext * context,
                GdkWindow * dest_window,
                GdkDragProtocol protocol,
                gint x_root,
                gint y_root,
                GdkDragAction suggested_action,
                GdkDragAction possible_actions, guint32 time)
{
   return FALSE;
}

void gdk_drag_drop(GdkDragContext * context, guint32 time)
{
   g_return_if_fail(context != NULL);

   g_warning("gdk_drag_drop: not implemented\n");
}

void gdk_drag_abort(GdkDragContext * context, guint32 time)
{
   g_return_if_fail(context != NULL);

   gdk_drag_do_leave(context, time);
}

/* Destination side */

void
gdk_drag_status(GdkDragContext * context,
                GdkDragAction action, guint32 time)
{
   GDK_NOTE(DND, g_print("gdk_drag_status\n"));
}

void gdk_drop_reply(GdkDragContext * context, gboolean ok, guint32 time)
{
}

void
gdk_drop_finish(GdkDragContext * context, gboolean success, guint32 time)
{
}

static GdkFilterReturn
gdk_destroy_filter(GdkXEvent * xev, GdkEvent * event, gpointer data)
{
#ifdef OLE2_DND
   MSG *msg = (MSG *) xev;

   if (msg->message == WM_DESTROY) {
      IDropTarget *idtp = (IDropTarget *) data;

      GDK_NOTE(DND,
               g_print("gdk_destroy_filter: WM_DESTROY: %#x\n",
                       msg->hwnd));
      RevokeDragDrop(msg->hwnd);
      CoLockObjectExternal(idtp, FALSE, TRUE);
   }
#endif
   return GDK_FILTER_CONTINUE;
}

void gdk_window_register_dnd(GdkWindow * window)
{
#ifdef OLE2_DND
   target_drag_context *context;
   HRESULT hres;
#endif

   g_return_if_fail(window != NULL);

   GDK_NOTE(DND, g_print("gdk_window_register_dnd: %#x\n",
                         GDK_DRAWABLE_XID(window)));

   /* We always claim to accept dropped files, but in fact we might not,
    * of course. This function is called in such a way that it cannot know
    * whether the window (widget) in question actually accepts files
    * (in gtk, data of type text/uri-list) or not.
    */
   gdk_window_add_filter(window, gdk_dropfiles_filter, NULL);
   DragAcceptFiles(GDK_DRAWABLE_XID(window), TRUE);

#ifdef OLE2_DND
   /* Register for OLE2 d&d */
   context = target_context_new();
   hres = CoLockObjectExternal((IUnknown *) & context->idt, TRUE, FALSE);
   if (!SUCCEEDED(hres))
      OTHER_API_FAILED("CoLockObjectExternal");
   else {
      hres = RegisterDragDrop(GDK_DRAWABLE_XID(window), &context->idt);
      if (hres == DRAGDROP_E_ALREADYREGISTERED) {
         g_print("DRAGDROP_E_ALREADYREGISTERED\n");
         CoLockObjectExternal((IUnknown *) & context->idt, FALSE, FALSE);
      } else if (!SUCCEEDED(hres))
         OTHER_API_FAILED("RegisterDragDrop");
      else {
         gdk_window_add_filter(window, gdk_destroy_filter, &context->idt);
      }
   }
#endif
}

/*************************************************************
 * gdk_drag_get_selection:
 *     Returns the selection atom for the current source window
 *   arguments:
 *
 *   results:
 *************************************************************/

GdkAtom gdk_drag_get_selection(GdkDragContext * context)
{
   if (context->protocol == GDK_DRAG_PROTO_WIN32_DROPFILES)
      return gdk_win32_dropfiles_atom;
   else if (context->protocol == GDK_DRAG_PROTO_OLE2)
      return gdk_ole2_dnd_atom;
   else
      return GDK_NONE;
}

---