(From update of attachment 403730)
>diff --git a/widget/src/gtk2/nsDragService.cpp b/widget/src/gtk2/nsDragService.cpp
>--- a/widget/src/gtk2/nsDragService.cpp
>+++ b/widget/src/gtk2/nsDragService.cpp
>@@ -53,26 +53,31 @@
> #include "nsNetUtil.h"
> #include "prlog.h"
> #include "nsVoidArray.h"
> #include "nsPrimitiveHelpers.h"
> #include "prtime.h"
> #include "prthread.h"
> #include <gtk/gtkinvisible.h>
> #include <gdk/gdkx.h>
>+#include <unistd.h>
> #include "nsCRT.h"
> 
> #include "gfxASurface.h"
> #include "gfxXlibSurface.h"
> #include "gfxContext.h"
> #include "nsImageToPixbuf.h"
> #include "nsIPresShell.h"
> #include "nsPresContext.h"
> #include "nsIDocument.h"
> #include "nsISelection.h"
>+#include "nsDirectoryService.h"
>+#include "nsDirectoryServiceDefs.h"
>+#include "nsEscape.h"
>+#include "nsString.h"
> 
> // This sets how opaque the drag image is
> #define DRAG_IMAGE_ALPHA_LEVEL 0.5
> 
> // These values are copied from GtkDragResult (rather than using GtkDragResult
> // directly) so that this code can be compiled against versions of GTK+ that
> // do not have GtkDragResult.
> // GtkDragResult is available from GTK+ version 2.12.
>@@ -141,16 +146,19 @@ nsDragService::nsDragService()
>     PR_LOG(sDragLm, PR_LOG_DEBUG, ("nsDragService::nsDragService"));
>     mTargetWidget = 0;
>     mTargetDragContext = 0;
>     mTargetTime = 0;
>     mCanDrop = PR_FALSE;
>     mTargetDragDataReceived = PR_FALSE;
>     mTargetDragData = 0;
>     mTargetDragDataLen = 0;
>+    mTempFileCreated = PR_FALSE;
>+    mTimer = do_CreateInstance("@mozilla.org/timer;1");
>+
> }
> 
> nsDragService::~nsDragService()
> {
>     PR_LOG(sDragLm, PR_LOG_DEBUG, ("nsDragService::~nsDragService"));
> }
> 
> NS_IMPL_ISUPPORTS_INHERITED2(nsDragService, nsBaseDragService,
>@@ -173,16 +181,36 @@ nsDragService::Observe(nsISupports *aSub
>   } else {
>     NS_NOTREACHED("unexpected topic");
>     return NS_ERROR_UNEXPECTED;
>   }
> 
>   return NS_OK;
> }
> 
>+// nsITimer
>+
>+NS_IMETHODIMP
>+nsDragService::Notify(nsITimer *timer)
>+{
>+  // We can not delete the temporary files immediately after the
>+  // drag has finished, because the target application might have not
>+  // copied the temporary file yet. Instead we collect all temporary
>+  // files in mTemporaryFiles array and remove them here in the timer event.
>+  PRUint32 count = mTemporaryFiles.Count();
>+
>+  while (count > 0) {
>+    --count;
>+    mTemporaryFiles[count]->Remove(PR_TRUE);
>+  }
>+  mTemporaryFiles.Clear();
>+
>+  return NS_OK;
>+}
>+
> // nsIDragService
> 
> NS_IMETHODIMP
> nsDragService::InvokeDragSession(nsIDOMNode *aDOMNode,
>                                  nsISupportsArray * aArrayTransferables,
>                                  nsIScriptableRegion * aRegion,
>                                  PRUint32 aActionType)
> {
>@@ -321,16 +349,18 @@ nsDragService::SetAlphaPixmap(gfxASurfac
>     gdk_pixmap_unref(pixmap);
>     return PR_TRUE;
> }
> 
> NS_IMETHODIMP
> nsDragService::StartDragSession()
> {
>     PR_LOG(sDragLm, PR_LOG_DEBUG, ("nsDragService::StartDragSession"));
>+    mTempFileCreated = false;
>+
>     return nsBaseDragService::StartDragSession();
> }
>  
> NS_IMETHODIMP
> nsDragService::EndDragSession(PRBool aDoneDrag)
> {
>     PR_LOG(sDragLm, PR_LOG_DEBUG, ("nsDragService::EndDragSession %d",
>                                    aDoneDrag));
>@@ -439,16 +469,59 @@ nsDragService::GetNumDropItems(PRUint32 
>             *aNumItems = CountTextUriListItems(data, mTargetDragDataLen);
>         } else
>             *aNumItems = 1;
>     }
>     PR_LOG(sDragLm, PR_LOG_DEBUG, ("%d items", *aNumItems));
>     return NS_OK;
> }
> 
>+nsresult GetDownloadDetails(nsITransferable * aTransferable, nsIURI **aSourceURI, nsAString &aFilename)
>+{
>+  *aSourceURI = nsnull;
>+
>+  NS_ENSURE_TRUE(aTransferable, NS_ERROR_FAILURE);
>+
>+  // get the URI from the kFilePromiseURLMime flavor
>+  nsCOMPtr<nsISupports> urlPrimitive;
>+  PRUint32 dataSize = 0;
>+  aTransferable->GetTransferData(kFilePromiseURLMime, getter_AddRefs(urlPrimitive), &dataSize);
>+  nsCOMPtr<nsISupportsString> srcUrlPrimitive = do_QueryInterface(urlPrimitive);
>+  NS_ENSURE_TRUE(srcUrlPrimitive, NS_ERROR_FAILURE);
>+
>+  nsAutoString srcUri;
>+  srcUrlPrimitive->GetData(srcUri);
>+  if (srcUri.IsEmpty())
>+    return NS_ERROR_FAILURE;
>+  nsCOMPtr<nsIURI> sourceURI;
>+  NS_NewURI(getter_AddRefs(sourceURI), srcUri);
>+
>+  nsAutoString srcFileName;
>+  nsCOMPtr<nsISupports> fileNamePrimitive;
>+  aTransferable->GetTransferData(kFilePromiseDestFilename, getter_AddRefs(fileNamePrimitive), &dataSize);
>+  nsCOMPtr<nsISupportsString> srcFileNamePrimitive = do_QueryInterface(fileNamePrimitive);
>+  if (srcFileNamePrimitive) {
>+    srcFileNamePrimitive->GetData(srcFileName);
>+  } else {
>+    nsCOMPtr<nsIURL> sourceURL = do_QueryInterface(sourceURI);
>+    if (!sourceURL)
>+      return NS_ERROR_FAILURE;
>+
>+    nsCAutoString urlFileName;
>+    sourceURL->GetFileName(urlFileName);
>+    NS_UnescapeURL(urlFileName);
>+    CopyUTF8toUTF16(urlFileName, srcFileName);
>+  }
>+  if (srcFileName.IsEmpty())
>+    return NS_ERROR_FAILURE;
>+
>+  sourceURI.swap(*aSourceURI);
>+  aFilename = srcFileName;
>+  return NS_OK;
>+}
> 
> NS_IMETHODIMP
> nsDragService::GetData(nsITransferable * aTransferable,
>                        PRUint32 aItemIndex)
> {
>     PR_LOG(sDragLm, PR_LOG_DEBUG, ("nsDragService::GetData %d", aItemIndex));
> 
>     // make sure that we have a transferable
>@@ -1063,16 +1136,17 @@ nsDragService::GetSourceList(void)
>                             listTarget->target = g_strdup(gTextUriListType);
>                             listTarget->flags = 0;
>                             /* Bug 331198 */
>                             listTarget->info = NS_PTR_TO_UINT32(listAtom);
>                             PR_LOG(sDragLm, PR_LOG_DEBUG,
>                                    ("automatically adding target %s with \
>                                    id %ld\n", listTarget->target, listAtom));
>                             targetArray.AppendElement(listTarget);
>+                            break;
>                         }
>                     }
>                 } // foreach flavor in item
>             } // if valid flavor list
>         } // if item is a transferable
>     } else if (numDragItems == 1) {
>         nsCOMPtr<nsISupports> genericItem;
>         mSourceDataItems->GetElementAt(0, getter_AddRefs(genericItem));
>@@ -1138,16 +1212,28 @@ nsDragService::GetSourceList(void)
>                             urlTarget->flags = 0;
>                             /* Bug 331198 */
>                             urlTarget->info = NS_PTR_TO_UINT32(urlAtom);
>                             PR_LOG(sDragLm, PR_LOG_DEBUG,
>                                    ("automatically adding target %s with \
>                                    id %ld\n", urlTarget->target, urlAtom));
>                             targetArray.AppendElement(urlTarget);
>                         }
>+                        // check if application/x-moz-file-promise url is supported.
>+                        // If so, advertise text/uri-list.
>+                        if (strcmp(flavorStr, kFilePromiseURLMime) == 0) {
>+                            GdkAtom urlAtom = gdk_atom_intern(gTextUriListType, FALSE);
>+                            GtkTargetEntry *urlTarget =
>+                             (GtkTargetEntry *)g_malloc(sizeof(GtkTargetEntry));
>+                            urlTarget->target = g_strdup(gTextUriListType);
>+                            urlTarget->flags = 0;
>+                            /* Bug 331198 */
>+                            urlTarget->info = NS_PTR_TO_UINT32(urlAtom);
>+                            targetArray.AppendElement(urlTarget);
>+                        }
>                     }
>                 } // foreach flavor in item
>             } // if valid flavor list
>         } // if item is a transferable
>     } // if it is a single item drag
> 
>     // get all the elements that we created.
>     targetCount = targetArray.Count();
>@@ -1235,16 +1321,18 @@ nsDragService::SourceEndDragSession(GdkD
>         do_QueryInterface(mDataTransfer);
> 
>     if (dataTransfer) {
>         dataTransfer->SetDropEffectInt(dropEffect);
>     }
> 
>     // Inform the drag session that we're ending the drag.
>     EndDragSession(PR_TRUE);
>+
>+    mTempFileCreated = PR_FALSE;
> }
> 
> static void
> CreateUriList(nsISupportsArray *items, gchar **text, gint *length)
> {
>     PRUint32 i, count;
>     GString *uriList = g_string_new(NULL);
> 
>@@ -1301,16 +1389,128 @@ CreateUriList(nsISupportsArray *items, g
>             }
>         }
>     }
>     *text = uriList->str;
>     *length = uriList->len + 1;
>     g_string_free(uriList, FALSE); // don't free the data
> }
> 
>+PRBool
>+nsDragService::CreateTempFile(nsITransferable *aItem, GtkSelectionData *aSelectionData)
>+{
>+    nsCOMPtr<nsIFile> tmpDir;
>+    nsresult rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(tmpDir));
>+
>+    if (NS_FAILED(rv)) {
>+        PR_LOG(sDragLm, PR_LOG_DEBUG, ("Failed to get temp directory\n"));
>+        return rv;
>+    }
>+
>+    nsCOMPtr<nsIInputStream> inputStream;
>+    nsCOMPtr<nsIChannel> channel;
>+
>+    // extract the file name and source uri of the promise-file data
>+    nsAutoString wideFileName;
>+    nsCOMPtr<nsIURI> sourceURI;
>+    rv = GetDownloadDetails(aItem, getter_AddRefs(sourceURI), wideFileName);
>+    if (NS_FAILED(rv)) {
>+        PR_LOG(sDragLm, PR_LOG_DEBUG, ("Failed to extract file name and source uri from download url\n"));
>+        return rv;
>+    }
>+
>+    // create and open channel for source uri
>+    rv = NS_NewChannel(getter_AddRefs(channel), sourceURI);
>+    if (NS_FAILED(rv)) {
>+        PR_LOG(sDragLm, PR_LOG_DEBUG, ("Failed to create new channel for source uri\n"));
>+        return rv;
>+    }
>+
>+    rv = channel->Open(getter_AddRefs(inputStream));
>+    if (NS_FAILED(rv)) {
>+        PR_LOG(sDragLm, PR_LOG_DEBUG, ("Failed to open channel for source uri\n"));
>+        return rv;
>+    }
>+
>+    // build the file:///tmp/dnd_file URL
>+    tmpDir->Append(NS_LITERAL_STRING("dnd_file"));
>+    tmpDir->CreateUnique(nsIFile::DIRECTORY_TYPE, 0700);
>+
>+    // store a copy of that temporary directory so we can
>+    // clean them up when nsDragService is destructed
>+    nsCOMPtr<nsIFile> tempFile;
>+    tmpDir->Clone(getter_AddRefs(tempFile));
>+
>+    mTemporaryFiles.AppendObject(tempFile);
>+
>+    mTimer->Cancel();
>+    mTimer->InitWithCallback(static_cast<nsITimerCallback*>(this), 
>+                             NS_DND_TIMEOUT,
>+                             nsITimer::TYPE_ONE_SHOT);
>+
>+    // extend file:///tmp/dnd_file/<filename> URL
>+    tmpDir->Append(wideFileName);
>+
>+    nsCOMPtr<nsIOutputStream> outputStream;
>+    rv = NS_NewLocalFileOutputStream(getter_AddRefs(outputStream), tmpDir);
>+    if (NS_FAILED(rv)) {
>+        PR_LOG(sDragLm, PR_LOG_DEBUG, ("Failed to open output stream for temporary file\n"));
>+        return rv;
>+    }
>+    mTempFileCreated = PR_TRUE;
>+
>+    char buffer[512];
>+    PRUint32 readCount = 0;
>+    PRUint32 writeCount = 0;
>+    while (1) {
>+        rv = inputStream->Read(buffer, sizeof(buffer), &readCount);
>+        if (NS_FAILED(rv)) {
>+            PR_LOG(sDragLm, PR_LOG_DEBUG, ("Failed to read data from source uri\n"));
>+            return rv;
>+        }
>+
>+        if (readCount == 0)
>+            break;
>+
>+        rv = outputStream->Write(buffer, readCount, &writeCount);
>+        if (NS_FAILED(rv)) {
>+            PR_LOG(sDragLm, PR_LOG_DEBUG, ("Failed to write data to temporary file\n"));
>+            return rv;
>+        }
>+    }
>+
>+    outputStream->Close();
>+    inputStream->Close();
>+
>+    nsCOMPtr<nsIURI> uri;
>+    rv = NS_NewFileURI(getter_AddRefs(uri), tmpDir);
>+    if (NS_SUCCEEDED(rv)) {
>+        nsCOMPtr<nsIURL> fileURL(do_QueryInterface(uri));
>+        if (fileURL) {
>+            // according to XDG spec, text/uri-list urls need a hostname set
>+            char hostname[255];
>+            gethostname(hostname, sizeof(hostname));
>+
>+            nsCAutoString hostnameStr;
>+            hostnameStr.AssignASCII(hostname);
>+
>+            fileURL->SetHost(hostnameStr);
>+
>+            nsCAutoString urltext;
>+            rv = fileURL->GetSpec(urltext);
>+            if (NS_SUCCEEDED(rv)) {
>+                // store url of temporary file
>+                mTempFileUrl.AssignASCII(urltext.get());
>+                return NS_OK;
>+            }
>+        }
>+    }
>+
>+    return NS_ERROR_FAILURE;
>+}
> 
> void
> nsDragService::SourceDataGet(GtkWidget        *aWidget,
>                              GdkDragContext   *aContext,
>                              GtkSelectionData *aSelectionData,
>                              guint             aInfo,
>                              guint32           aTime)
> {
>@@ -1357,16 +1557,63 @@ nsDragService::SourceDataGet(GtkWidget  
>         // plain text.
>         else if (strcmp(mimeFlavor, gTextUriListType) == 0) {
>             actualFlavor = gTextUriListType;
>             needToDoConversionToPlainText = PR_TRUE;
>         }
>         else
>             actualFlavor = mimeFlavor;
> 
>+        // The desktop or file manager expects for drags of promise-file data the
>+        // text/uri-list flavor set to a temporary file that contains the
>+        // promise-file data.
>+        // We open a stream on the <protocol>:// url here and save the content
>+        // to file:///tmp/dnd_file/<filename> and pass this url
>+        // as text/uri-list flavor.
>+        if (strcmp(mimeFlavor, gTextUriListType) == 0) {
>+            PRUint32 i, count;
>+            mSourceDataItems->Count(&count);
>+
>+            // check whether transferable contains FilePromiseUrl flavor...
>+            PRBool foundFilePromiseFlavor = PR_FALSE;
>+            for (i = 0; i < count; i++) {
>+                nsCOMPtr<nsISupports> genericItem;
>+                mSourceDataItems->GetElementAt(i, getter_AddRefs(genericItem));
>+                nsCOMPtr<nsITransferable> item;
>+                item = do_QueryInterface(genericItem);
>+
>+                PRUint32 tmpDataLen = 0;
>+                nsresult rv;
>+                nsCOMPtr<nsISupports> data;
>+                rv = item->GetTransferData(kFilePromiseURLMime,
>+                                           getter_AddRefs(data),
>+                                           &tmpDataLen);
>+                if (NS_SUCCEEDED(rv)) {
>+                    foundFilePromiseFlavor = PR_TRUE;
>+                    break;
>+                }
>+            }
>+
>+            // ... if so, create a temporary file and pass its url as text/uri-list flavor
>+            if (foundFilePromiseFlavor == PR_TRUE) {
>+                if (!mTempFileCreated) {
>+                    nsresult rv;
>+                    rv = CreateTempFile(item, aSelectionData);
>+                    if (NS_FAILED(rv))
>+                        return;
>+                }
>+
>+                NS_ConvertUTF16toUTF8 tempFileUrl(mTempFileUrl);
>+                gtk_selection_data_set(aSelectionData,
>+                                       aSelectionData->target,
>+                                       8, (guchar*)tempFileUrl.get(), tempFileUrl.Length());
>+                return;
>+            }
>+        }
>+
>         PRUint32 tmpDataLen = 0;
>         void    *tmpData = NULL;
>         nsresult rv;
>         nsCOMPtr<nsISupports> data;
>         rv = item->GetTransferData(actualFlavor,
>                                    getter_AddRefs(data),
>                                    &tmpDataLen);
>         if (NS_SUCCEEDED(rv)) {
>diff --git a/widget/src/gtk2/nsDragService.h b/widget/src/gtk2/nsDragService.h
>--- a/widget/src/gtk2/nsDragService.h
>+++ b/widget/src/gtk2/nsDragService.h
>@@ -37,36 +37,40 @@
>  * the terms of any one of the MPL, the GPL or the LGPL.
>  *
>  * ***** END LICENSE BLOCK ***** */
> 
> #ifndef nsDragService_h__
> #define nsDragService_h__
> 
> #include "nsBaseDragService.h"
>+#include "nsCOMArray.h"
> #include "nsIDragSessionGTK.h"
> #include "nsIObserver.h"
>+#include "nsITimer.h"
> #include <gtk/gtk.h>
> 
> 
> /**
>  * Native GTK DragService wrapper
>  */
> 
> class nsDragService : public nsBaseDragService,
>                       public nsIDragSessionGTK,
>+                      public nsITimerCallback,
>                       public nsIObserver
> {
> public:
>     nsDragService();
>     virtual ~nsDragService();
> 
>     NS_DECL_ISUPPORTS_INHERITED
> 
>     NS_DECL_NSIOBSERVER
>+    NS_DECL_NSITIMERCALLBACK
> 
>     // nsIDragService
>     NS_IMETHOD InvokeDragSession (nsIDOMNode *aDOMNode,
>                                   nsISupportsArray * anArrayTransferables,
>                                   nsIScriptableRegion * aRegion,
>                                   PRUint32 aActionType);
>     NS_IMETHOD StartDragSession();
>     NS_IMETHOD EndDragSession(PRBool aDoneDrag);
>@@ -146,12 +150,25 @@ private:
>     // attempts to create a semi-transparent drag image. Returns TRUE if
>     // successful, FALSE if not
>     PRBool SetAlphaPixmap(gfxASurface    *aPixbuf,
>                           GdkDragContext *aContext,
>                           PRInt32         aXOffset,
>                           PRInt32         aYOffset,
>                           const nsRect&   dragRect);
> 
>+    PRBool CreateTempFile(nsITransferable *aItem, GtkSelectionData *aSelectionData);
>+
>+    // stores whether a temporary file has been created for the
>+    // current drag session
>+    PRBool              mTempFileCreated;
>+
>+    nsString            mTempFileUrl;
>+
>+    // stores all temporary files
>+    nsCOMArray<nsIFile> mTemporaryFiles;
>+
>+    // timer to trigger deletion of temporary files
>+    nsCOMPtr<nsITimer>  mTimer;
> };
> 
> #endif // nsDragService_h__
>