widget/gtk/nsDragService.cpp
author Lee Salzman <lsalzman@mozilla.com>
Sat, 28 Jan 2023 11:24:54 +0000
changeset 650885 f4f63f0138feb7535fa58c3f77fd8a51361371d8
parent 646579 a3fb01c6e76a9f4545290c6c7caf5f3ec056575d
permissions -rw-r--r--
Bug 1812970 - Avoid using Skia's deprecated clip ops. r=jrmuizel Skia upstream removed deprecated clip ops that could be used to replace the clipping stack and bypass clips. We shouldn't really need to do this anymore, as we can work around it just using public APIs. The only SkCanvas operation that allows us to bypass clipping is writePixels, which still allows us to implement CopySurface/putImageData. Other instances where we were using the replace op for DrawTargetWebgl layering support can just be worked around by creating a separate DrawTargetSkia pointing to the same pixel data, but on which no clipping or transforms are applied so that we can freely do drawing operations on it to the base layer pixel data regardless of any user-applied clipping. Differential Revision: https://phabricator.services.mozilla.com/D168039

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=4 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsDragService.h"
#include "nsArrayUtils.h"
#include "nsIObserverService.h"
#include "nsWidgetsCID.h"
#include "nsWindow.h"
#include "nsSystemInfo.h"
#include "nsXPCOM.h"
#include "nsICookieJarSettings.h"
#include "nsISupportsPrimitives.h"
#include "nsIIOService.h"
#include "nsIFileURL.h"
#include "nsNetUtil.h"
#include "mozilla/Logging.h"
#include "nsTArray.h"
#include "nsPrimitiveHelpers.h"
#include "prtime.h"
#include "prthread.h"
#include <dlfcn.h>
#include <gtk/gtk.h>
#include "nsCRT.h"
#include "mozilla/BasicEvents.h"
#include "mozilla/Services.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/PresShell.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/WidgetUtilsGtk.h"
#include "GRefPtr.h"
#include "nsAppShell.h"

#ifdef MOZ_X11
#  include "gfxXlibSurface.h"
#endif
#include "gfxContext.h"
#include "nsImageToPixbuf.h"
#include "nsPresContext.h"
#include "nsIContent.h"
#include "mozilla/dom/Document.h"
#include "nsViewManager.h"
#include "nsIFrame.h"
#include "nsGtkUtils.h"
#include "nsGtkKeyUtils.h"
#include "mozilla/gfx/2D.h"
#include "gfxPlatform.h"
#include "ScreenHelperGTK.h"
#include "nsArrayUtils.h"
#include "nsStringStream.h"
#include "nsDirectoryService.h"
#include "nsDirectoryServiceDefs.h"
#include "nsEscape.h"
#include "nsString.h"

using namespace mozilla;
using namespace mozilla::gfx;

//  The maximum time to wait for a "drag_received" arrived in microseconds.
#define NS_DND_TIMEOUT 1000000

//  The maximum time to wait before temporary files resulting
//  from drag'n'drop events will be removed in miliseconds.
//  It's set to 5 min as the file has to be present some time after drop
//  event to give target application time to get the data.
//  (A target application can throw a dialog to ask user what to do with
//  the data and will access the tmp file after user action.)
#define NS_DND_TMP_CLEANUP_TIMEOUT (1000 * 60 * 5)

#define NS_SYSTEMINFO_CONTRACTID "@mozilla.org/system-info;1"

// This sets how opaque the drag image is
#define DRAG_IMAGE_ALPHA_LEVEL 0.5

#ifdef MOZ_LOGGING
extern mozilla::LazyLogModule gWidgetDragLog;
#  define LOGDRAGSERVICE(str, ...)                    \
    MOZ_LOG(gWidgetDragLog, mozilla::LogLevel::Debug, \
            ("[Depth %d]: " str, GetLoopDepth(), ##__VA_ARGS__))
#  define LOGDRAGSERVICESTATIC(str, ...) \
    MOZ_LOG(gWidgetDragLog, mozilla::LogLevel::Debug, (str, ##__VA_ARGS__))
#else
#  define LOGDRAGSERVICE(...)
#endif

// Helper class to block native events processing.
class MOZ_STACK_CLASS AutoSuspendNativeEvents {
 public:
  AutoSuspendNativeEvents() {
    mAppShell = do_GetService(NS_APPSHELL_CID);
    mAppShell->SuspendNative();
  }
  ~AutoSuspendNativeEvents() { mAppShell->ResumeNative(); }

 private:
  nsCOMPtr<nsIAppShell> mAppShell;
};

// data used for synthetic periodic motion events sent to the source widget
// grabbing real events for the drag.
static guint sMotionEventTimerID;

static GdkEvent* sMotionEvent;
static GUniquePtr<GdkEvent> TakeMotionEvent() {
  GUniquePtr<GdkEvent> event(sMotionEvent);
  sMotionEvent = nullptr;
  return event;
}
static void SetMotionEvent(GUniquePtr<GdkEvent> aEvent) {
  TakeMotionEvent();
  sMotionEvent = aEvent.release();
}

static GtkWidget* sGrabWidget;

static constexpr nsLiteralString kDisallowedExportedSchemes[] = {
    u"about"_ns,      u"blob"_ns,     u"chrome"_ns,      u"imap"_ns,
    u"javascript"_ns, u"mailbox"_ns,  u"moz-anno"_ns,    u"news"_ns,
    u"page-icon"_ns,  u"resource"_ns, u"view-source"_ns, u"moz-extension"_ns,
};

// _NETSCAPE_URL is similar to text/uri-list type.
// Format is UTF8: URL + "\n" + title.
// While text/uri-list tells target application to fetch, copy and store data
// from URL, _NETSCAPE_URL suggest to create a link to the target.
// Also _NETSCAPE_URL points to only one item while text/uri-list can point to
// multiple ones.
static const char gMozUrlType[] = "_NETSCAPE_URL";
static const char gMimeListType[] = "application/x-moz-internal-item-list";
static const char gTextUriListType[] = "text/uri-list";
static const char gTextPlainUTF8Type[] = "text/plain;charset=utf-8";
static const char gXdndDirectSaveType[] = "XdndDirectSave0";
static const char gTabDropType[] = "application/x-moz-tabbrowser-tab";

// See https://docs.gtk.org/gtk3/enum.DragResult.html
static const char kGtkDragResults[][100]{
    "GTK_DRAG_RESULT_SUCCESS",        "GTK_DRAG_RESULT_NO_TARGET",
    "GTK_DRAG_RESULT_USER_CANCELLED", "GTK_DRAG_RESULT_TIMEOUT_EXPIRED",
    "GTK_DRAG_RESULT_GRAB_BROKEN",    "GTK_DRAG_RESULT_ERROR"};

static void invisibleSourceDragBegin(GtkWidget* aWidget,
                                     GdkDragContext* aContext, gpointer aData);

static void invisibleSourceDragEnd(GtkWidget* aWidget, GdkDragContext* aContext,
                                   gpointer aData);

static gboolean invisibleSourceDragFailed(GtkWidget* aWidget,
                                          GdkDragContext* aContext,
                                          gint aResult, gpointer aData);

static void invisibleSourceDragDataGet(GtkWidget* aWidget,
                                       GdkDragContext* aContext,
                                       GtkSelectionData* aSelectionData,
                                       guint aInfo, guint32 aTime,
                                       gpointer aData);

nsDragService::nsDragService()
    : mScheduledTask(eDragTaskNone),
      mTaskSource(0),
      mScheduledTaskIsRunning(false),
      mCachedDragContext() {
  // We have to destroy the hidden widget before the event loop stops
  // running.
  nsCOMPtr<nsIObserverService> obsServ =
      mozilla::services::GetObserverService();
  obsServ->AddObserver(this, "quit-application", false);

  // our hidden source widget
  // Using an offscreen window works around bug 983843.
  mHiddenWidget = gtk_offscreen_window_new();
  // make sure that the widget is realized so that
  // we can use it as a drag source.
  gtk_widget_realize(mHiddenWidget);
  // hook up our internal signals so that we can get some feedback
  // from our drag source
  g_signal_connect(mHiddenWidget, "drag_begin",
                   G_CALLBACK(invisibleSourceDragBegin), this);
  g_signal_connect(mHiddenWidget, "drag_data_get",
                   G_CALLBACK(invisibleSourceDragDataGet), this);
  g_signal_connect(mHiddenWidget, "drag_end",
                   G_CALLBACK(invisibleSourceDragEnd), this);
  // drag-failed is available from GTK+ version 2.12
  guint dragFailedID =
      g_signal_lookup("drag-failed", G_TYPE_FROM_INSTANCE(mHiddenWidget));
  if (dragFailedID) {
    g_signal_connect_closure_by_id(
        mHiddenWidget, dragFailedID, 0,
        g_cclosure_new(G_CALLBACK(invisibleSourceDragFailed), this, nullptr),
        FALSE);
  }

  // set up our logging module
  mCanDrop = false;
  mTargetDragDataReceived = false;
  mTargetDragData = 0;
  mTargetDragDataLen = 0;
  mTempFileTimerID = 0;
  mEventLoopDepth = 0;
  LOGDRAGSERVICE("nsDragService::nsDragService");
}

nsDragService::~nsDragService() {
  LOGDRAGSERVICE("nsDragService::~nsDragService");
  if (mTaskSource) g_source_remove(mTaskSource);
  if (mTempFileTimerID) {
    g_source_remove(mTempFileTimerID);
    RemoveTempFiles();
  }
}

NS_IMPL_ISUPPORTS_INHERITED(nsDragService, nsBaseDragService, nsIObserver)

mozilla::StaticRefPtr<nsDragService> sDragServiceInstance;
/* static */
already_AddRefed<nsDragService> nsDragService::GetInstance() {
  if (gfxPlatform::IsHeadless()) {
    return nullptr;
  }
  if (!sDragServiceInstance) {
    sDragServiceInstance = new nsDragService();
    ClearOnShutdown(&sDragServiceInstance);
  }

  RefPtr<nsDragService> service = sDragServiceInstance.get();
  return service.forget();
}

// nsIObserver

NS_IMETHODIMP
nsDragService::Observe(nsISupports* aSubject, const char* aTopic,
                       const char16_t* aData) {
  if (!nsCRT::strcmp(aTopic, "quit-application")) {
    LOGDRAGSERVICE("nsDragService::Observe(\"quit-application\")");
    if (mHiddenWidget) {
      gtk_widget_destroy(mHiddenWidget);
      mHiddenWidget = 0;
    }
    TargetResetData();
  } else {
    MOZ_ASSERT_UNREACHABLE("unexpected topic");
    return NS_ERROR_UNEXPECTED;
  }

  return NS_OK;
}

// Support for periodic drag events

// http://www.whatwg.org/specs/web-apps/current-work/multipage/dnd.html#drag-and-drop-processing-model
// and the Xdnd protocol both recommend that drag events are sent periodically,
// but GTK does not normally provide this.
//
// Here GTK is periodically stimulated by copies of the most recent mouse
// motion events so as to send drag position messages to the destination when
// appropriate (after it has received a status event from the previous
// message).
//
// (If events were sent only on the destination side then the destination
// would have no message to which it could reply with a drag status.  Without
// sending a drag status to the source, the destination would not be able to
// change its feedback re whether it could accept the drop, and so the
// source's behavior on drop will not be consistent.)

static gboolean DispatchMotionEventCopy(gpointer aData) {
  // Clear the timer id before OnSourceGrabEventAfter is called during event
  // dispatch.
  sMotionEventTimerID = 0;

  GUniquePtr<GdkEvent> event = TakeMotionEvent();
  // If there is no longer a grab on the widget, then the drag is over and
  // there is no need to continue drag motion.
  if (gtk_widget_has_grab(sGrabWidget)) {
    gtk_propagate_event(sGrabWidget, event.get());
  }

  // Cancel this timer;
  // We've already started another if the motion event was dispatched.
  return FALSE;
}

static void OnSourceGrabEventAfter(GtkWidget* widget, GdkEvent* event,
                                   gpointer user_data) {
  // If there is no longer a grab on the widget, then the drag motion is
  // over (though the data may not be fetched yet).
  if (!gtk_widget_has_grab(sGrabWidget)) return;

  if (event->type == GDK_MOTION_NOTIFY) {
    SetMotionEvent(GUniquePtr<GdkEvent>(gdk_event_copy(event)));

    // Update the cursor position.  The last of these recorded gets used for
    // the eDragEnd event.
    nsDragService* dragService = static_cast<nsDragService*>(user_data);
    gint scale = mozilla::widget::ScreenHelperGTK::GetGTKMonitorScaleFactor();
    auto p = LayoutDeviceIntPoint::Round(event->motion.x_root * scale,
                                         event->motion.y_root * scale);
    dragService->SetDragEndPoint(p);
  } else if (sMotionEvent &&
             (event->type == GDK_KEY_PRESS || event->type == GDK_KEY_RELEASE)) {
    // Update modifier state from key events.
    sMotionEvent->motion.state = event->key.state;
  } else {
    return;
  }

  if (sMotionEventTimerID) {
    g_source_remove(sMotionEventTimerID);
  }

  // G_PRIORITY_DEFAULT_IDLE is lower priority than GDK's redraw idle source
  // and lower than GTK's idle source that sends drag position messages after
  // motion-notify signals.
  //
  // http://www.whatwg.org/specs/web-apps/current-work/multipage/dnd.html#drag-and-drop-processing-model
  // recommends an interval of 350ms +/- 200ms.
  sMotionEventTimerID = g_timeout_add_full(
      G_PRIORITY_DEFAULT_IDLE, 350, DispatchMotionEventCopy, nullptr, nullptr);
}

static GtkWindow* GetGtkWindow(dom::Document* aDocument) {
  if (!aDocument) return nullptr;

  PresShell* presShell = aDocument->GetPresShell();
  if (!presShell) {
    return nullptr;
  }

  RefPtr<nsViewManager> vm = presShell->GetViewManager();
  if (!vm) return nullptr;

  nsCOMPtr<nsIWidget> widget = vm->GetRootWidget();
  if (!widget) return nullptr;

  GtkWidget* gtkWidget = static_cast<nsWindow*>(widget.get())->GetGtkWidget();
  if (!gtkWidget) return nullptr;

  GtkWidget* toplevel = nullptr;
  toplevel = gtk_widget_get_toplevel(gtkWidget);
  if (!GTK_IS_WINDOW(toplevel)) return nullptr;

  return GTK_WINDOW(toplevel);
}

// nsIDragService

NS_IMETHODIMP
nsDragService::InvokeDragSession(
    nsINode* aDOMNode, nsIPrincipal* aPrincipal, nsIContentSecurityPolicy* aCsp,
    nsICookieJarSettings* aCookieJarSettings, nsIArray* aArrayTransferables,
    uint32_t aActionType,
    nsContentPolicyType aContentPolicyType = nsIContentPolicy::TYPE_OTHER) {
  LOGDRAGSERVICE("nsDragService::InvokeDragSession");

  // If the previous source drag has not yet completed, signal handlers need
  // to be removed from sGrabWidget and dragend needs to be dispatched to
  // the source node, but we can't call EndDragSession yet because we don't
  // know whether or not the drag succeeded.
  if (mSourceNode) return NS_ERROR_NOT_AVAILABLE;

  return nsBaseDragService::InvokeDragSession(
      aDOMNode, aPrincipal, aCsp, aCookieJarSettings, aArrayTransferables,
      aActionType, aContentPolicyType);
}

// nsBaseDragService
nsresult nsDragService::InvokeDragSessionImpl(
    nsIArray* aArrayTransferables, const Maybe<CSSIntRegion>& aRegion,
    uint32_t aActionType) {
  // make sure that we have an array of transferables to use
  if (!aArrayTransferables) return NS_ERROR_INVALID_ARG;
  // set our reference to the transferables.  this will also addref
  // the transferables since we're going to hang onto this beyond the
  // length of this call
  mSourceDataItems = aArrayTransferables;

  LOGDRAGSERVICE("nsDragService::InvokeDragSessionImpl");

  // get the list of items we offer for drags
  GtkTargetList* sourceList = GetSourceList();

  if (!sourceList) return NS_OK;

  // save our action type
  GdkDragAction action = GDK_ACTION_DEFAULT;

  if (aActionType & DRAGDROP_ACTION_COPY)
    action = (GdkDragAction)(action | GDK_ACTION_COPY);
  if (aActionType & DRAGDROP_ACTION_MOVE)
    action = (GdkDragAction)(action | GDK_ACTION_MOVE);
  if (aActionType & DRAGDROP_ACTION_LINK)
    action = (GdkDragAction)(action | GDK_ACTION_LINK);

  GdkEvent* existingEvent = widget::GetLastMousePressEvent();
  GdkEvent fakeEvent;
  if (!existingEvent) {
    // Create a fake event for the drag so we can pass the time (so to speak).
    // If we don't do this, then, when the timestamp for the pending button
    // release event is used for the ungrab, the ungrab can fail due to the
    // timestamp being _earlier_ than CurrentTime.
    memset(&fakeEvent, 0, sizeof(GdkEvent));
    fakeEvent.type = GDK_BUTTON_PRESS;
    fakeEvent.button.window = gtk_widget_get_window(mHiddenWidget);
    fakeEvent.button.time = nsWindow::GetLastUserInputTime();
    fakeEvent.button.device = widget::GdkGetPointer();
  }

  // Put the drag widget in the window group of the source node so that the
  // gtk_grab_add during gtk_drag_begin is effective.
  // gtk_window_get_group(nullptr) returns the default window group.
  GtkWindowGroup* window_group =
      gtk_window_get_group(GetGtkWindow(mSourceDocument));
  gtk_window_group_add_window(window_group, GTK_WINDOW(mHiddenWidget));

  // start our drag.
  GdkDragContext* context = gtk_drag_begin_with_coordinates(
      mHiddenWidget, sourceList, action, 1,
      existingEvent ? existingEvent : &fakeEvent, -1, -1);

  if (widget::GdkIsWaylandDisplay() || widget::IsXWaylandProtocol()) {
    GdkDevice* device = gdk_drag_context_get_device(context);
    GdkWindow* gdkWindow =
        gdk_device_get_window_at_position(device, nullptr, nullptr);
    mSourceWindow = nsWindow::GetWindow(gdkWindow);
    if (mSourceWindow) {
      mSourceWindow->SetDragSource(context);
    }
  }

  LOGDRAGSERVICE("  GdkDragContext [%p] nsWindow [%p]", context,
                 mSourceWindow.get());

  nsresult rv;
  if (context) {
    StartDragSession();

    // GTK uses another hidden window for receiving mouse events.
    sGrabWidget = gtk_window_group_get_current_grab(window_group);
    if (sGrabWidget) {
      g_object_ref(sGrabWidget);
      // Only motion and key events are required but connect to
      // "event-after" as this is never blocked by other handlers.
      g_signal_connect(sGrabWidget, "event-after",
                       G_CALLBACK(OnSourceGrabEventAfter), this);
    }
    // We don't have a drag end point yet.
    mEndDragPoint = LayoutDeviceIntPoint(-1, -1);
    rv = NS_OK;
  } else {
    rv = NS_ERROR_FAILURE;
  }

  gtk_target_list_unref(sourceList);

  return rv;
}

bool nsDragService::SetAlphaPixmap(SourceSurface* aSurface,
                                   GdkDragContext* aContext, int32_t aXOffset,
                                   int32_t aYOffset,
                                   const LayoutDeviceIntRect& dragRect) {
  GdkScreen* screen = gtk_widget_get_screen(mHiddenWidget);

  // Transparent drag icons need, like a lot of transparency-related things,
  // a compositing X window manager
  if (!gdk_screen_is_composited(screen)) {
    return false;
  }

#ifdef cairo_image_surface_create
#  error "Looks like we're including Mozilla's cairo instead of system cairo"
#endif

  // TODO: grab X11 pixmap or image data instead of expensive readback.
  cairo_surface_t* surf = cairo_image_surface_create(
      CAIRO_FORMAT_ARGB32, dragRect.width, dragRect.height);
  if (!surf) return false;

  RefPtr<DrawTarget> dt = gfxPlatform::CreateDrawTargetForData(
      cairo_image_surface_get_data(surf),
      nsIntSize(dragRect.width, dragRect.height),
      cairo_image_surface_get_stride(surf), SurfaceFormat::B8G8R8A8);
  if (!dt) return false;

  dt->ClearRect(Rect(0, 0, dragRect.width, dragRect.height));
  dt->DrawSurface(
      aSurface, Rect(0, 0, dragRect.width, dragRect.height),
      Rect(0, 0, dragRect.width, dragRect.height), DrawSurfaceOptions(),
      DrawOptions(DRAG_IMAGE_ALPHA_LEVEL, CompositionOp::OP_SOURCE));

  cairo_surface_mark_dirty(surf);
  cairo_surface_set_device_offset(surf, -aXOffset, -aYOffset);

  // Ensure that the surface is drawn at the correct scale on HiDPI displays.
  static auto sCairoSurfaceSetDeviceScalePtr =
      (void (*)(cairo_surface_t*, double, double))dlsym(
          RTLD_DEFAULT, "cairo_surface_set_device_scale");
  if (sCairoSurfaceSetDeviceScalePtr) {
    gint scale = mozilla::widget::ScreenHelperGTK::GetGTKMonitorScaleFactor();
    sCairoSurfaceSetDeviceScalePtr(surf, scale, scale);
  }

  gtk_drag_set_icon_surface(aContext, surf);
  cairo_surface_destroy(surf);
  return true;
}

NS_IMETHODIMP
nsDragService::StartDragSession() {
  LOGDRAGSERVICE("nsDragService::StartDragSession");
  mTempFileUrls.Clear();
  return nsBaseDragService::StartDragSession();
}

bool nsDragService::RemoveTempFiles() {
  LOGDRAGSERVICE("nsDragService::RemoveTempFiles");

  // 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. The Qt toolkit does not provide a
  // way to mark a drop as finished in an asynchronous way, so most
  // Qt based applications do send the dnd_finished signal before they
  // have actually accessed the data from the temporary file.
  // (https://bugreports.qt.io/browse/QTBUG-5441)
  //
  // To work also with these applications we collect all temporary
  // files in mTemporaryFiles array and remove them here in the timer event.
  auto files = std::move(mTemporaryFiles);
  for (nsIFile* file : files) {
#ifdef MOZ_LOGGING
    if (MOZ_LOG_TEST(gWidgetDragLog, LogLevel::Debug)) {
      nsAutoCString path;
      if (NS_SUCCEEDED(file->GetNativePath(path))) {
        LOGDRAGSERVICE("  removing %s", path.get());
      }
    }
#endif
    file->Remove(/* recursive = */ true);
  }
  MOZ_ASSERT(mTemporaryFiles.IsEmpty());
  mTempFileTimerID = 0;
  // Return false to remove the timer added by g_timeout_add_full().
  return false;
}

gboolean nsDragService::TaskRemoveTempFiles(gpointer data) {
  RefPtr<nsDragService> dragService = static_cast<nsDragService*>(data);
  return dragService->RemoveTempFiles();
}

NS_IMETHODIMP
nsDragService::EndDragSession(bool aDoneDrag, uint32_t aKeyModifiers) {
  LOGDRAGSERVICE("nsDragService::EndDragSession(%p) %d",
                 mTargetDragContext.get(), aDoneDrag);

  if (sGrabWidget) {
    g_signal_handlers_disconnect_by_func(
        sGrabWidget, FuncToGpointer(OnSourceGrabEventAfter), this);
    g_object_unref(sGrabWidget);
    sGrabWidget = nullptr;

    if (sMotionEventTimerID) {
      g_source_remove(sMotionEventTimerID);
      sMotionEventTimerID = 0;
    }
    if (sMotionEvent) {
      TakeMotionEvent();
    }
  }

  // unset our drag action
  SetDragAction(DRAGDROP_ACTION_NONE);

  // start timer to remove temporary files
  if (mTemporaryFiles.Count() > 0 && !mTempFileTimerID) {
    LOGDRAGSERVICE("  queue removing of temporary files");
    // |this| won't be used after nsDragService delete because the timer is
    // removed in the nsDragService destructor.
    mTempFileTimerID =
        g_timeout_add(NS_DND_TMP_CLEANUP_TIMEOUT, TaskRemoveTempFiles, this);
    mTempFileUrls.Clear();
  }

  // We're done with the drag context.
  if (mSourceWindow) {
    mSourceWindow->SetDragSource(nullptr);
    mSourceWindow = nullptr;
  }
  mTargetDragContextForRemote = nullptr;
  mTargetWindow = nullptr;
  mPendingWindow = nullptr;
  mCachedDragContext = 0;

  return nsBaseDragService::EndDragSession(aDoneDrag, aKeyModifiers);
}

// nsIDragSession
NS_IMETHODIMP
nsDragService::SetCanDrop(bool aCanDrop) {
  LOGDRAGSERVICE("nsDragService::SetCanDrop %d", aCanDrop);
  mCanDrop = aCanDrop;
  return NS_OK;
}

NS_IMETHODIMP
nsDragService::GetCanDrop(bool* aCanDrop) {
  LOGDRAGSERVICE("nsDragService::GetCanDrop");
  *aCanDrop = mCanDrop;
  return NS_OK;
}

static void UTF16ToNewUTF8(const char16_t* aUTF16, uint32_t aUTF16Len,
                           char** aUTF8, uint32_t* aUTF8Len) {
  nsDependentSubstring utf16(aUTF16, aUTF16Len);
  *aUTF8 = ToNewUTF8String(utf16, aUTF8Len);
}

static void UTF8ToNewUTF16(const char* aUTF8, uint32_t aUTF8Len,
                           char16_t** aUTF16, uint32_t* aUTF16Len) {
  nsDependentCSubstring utf8(aUTF8, aUTF8Len);
  *aUTF16 = UTF8ToNewUnicode(utf8, aUTF16Len);
}

// count the number of URIs in some text/uri-list format data.
static uint32_t CountTextUriListItems(const char* data, uint32_t datalen) {
  const char* p = data;
  const char* endPtr = p + datalen;
  uint32_t count = 0;

  while (p < endPtr) {
    // skip whitespace (if any)
    while (p < endPtr && *p != '\0' && isspace(*p)) p++;
    // if we aren't at the end of the line ...
    if (p != endPtr && *p != '\0' && *p != '\n' && *p != '\r') count++;
    // skip to the end of the line
    while (p < endPtr && *p != '\0' && *p != '\n') p++;
    p++;  // skip the actual newline as well.
  }
  return count;
}

// extract an item from text/uri-list formatted data and convert it to
// unicode.
static void GetTextUriListItem(const char* data, uint32_t datalen,
                               uint32_t aItemIndex, char16_t** convertedText,
                               uint32_t* convertedTextLen) {
  const char* p = data;
  const char* endPtr = p + datalen;
  unsigned int count = 0;

  *convertedText = nullptr;
  while (p < endPtr) {
    // skip whitespace (if any)
    while (p < endPtr && *p != '\0' && isspace(*p)) p++;
    // if we aren't at the end of the line, we have a url
    if (p != endPtr && *p != '\0' && *p != '\n' && *p != '\r') count++;
    // this is the item we are after ...
    if (aItemIndex + 1 == count) {
      const char* q = p;
      while (q < endPtr && *q != '\0' && *q != '\n' && *q != '\r') q++;
      UTF8ToNewUTF16(p, q - p, convertedText, convertedTextLen);
      break;
    }
    // skip to the end of the line
    while (p < endPtr && *p != '\0' && *p != '\n') p++;
    p++;  // skip the actual newline as well.
  }

  // didn't find the desired item, so just pass the whole lot
  if (!*convertedText) {
    UTF8ToNewUTF16(data, datalen, convertedText, convertedTextLen);
  }
}

// Spins event loop, called from JS.
// Can lead to another round of drag_motion events.
NS_IMETHODIMP
nsDragService::GetNumDropItems(uint32_t* aNumItems) {
  LOGDRAGSERVICE("nsDragService::GetNumDropItems");

  if (!mTargetWidget) {
    LOGDRAGSERVICE(
        "*** warning: GetNumDropItems \
               called without a valid target widget!\n");
    *aNumItems = 0;
    return NS_OK;
  }

  bool isList = IsTargetContextList();
  if (isList) {
    if (!mSourceDataItems) {
      *aNumItems = 0;
      return NS_OK;
    }
    mSourceDataItems->GetLength(aNumItems);
  } else {
    GdkAtom gdkFlavor = gdk_atom_intern(gTextUriListType, FALSE);
    if (!gdkFlavor) {
      *aNumItems = 0;
      return NS_OK;
    }

    nsTArray<nsCString> dragFlavors;
    GetDragFlavors(dragFlavors);
    GetTargetDragData(gdkFlavor, dragFlavors);

    if (mTargetDragData) {
      const char* data = reinterpret_cast<char*>(mTargetDragData);
      *aNumItems = CountTextUriListItems(data, mTargetDragDataLen);
    } else
      *aNumItems = 1;
  }
  LOGDRAGSERVICE("  NumOfDropItems %d", *aNumItems);
  return NS_OK;
}

void nsDragService::GetDragFlavors(nsTArray<nsCString>& aFlavors) {
  for (GList* tmp = gdk_drag_context_list_targets(mTargetDragContext); tmp;
       tmp = tmp->next) {
    GdkAtom atom = GDK_POINTER_TO_ATOM(tmp->data);
    GUniquePtr<gchar> name(gdk_atom_name(atom));
    if (!name) {
      continue;
    }
    aFlavors.AppendElement(nsCString(name.get()));
  }
}

// Spins event loop, called from JS.
// Can lead to another round of drag_motion events.
NS_IMETHODIMP
nsDragService::GetData(nsITransferable* aTransferable, uint32_t aItemIndex) {
  LOGDRAGSERVICE("nsDragService::GetData(), index %d", aItemIndex);

  // make sure that we have a transferable
  if (!aTransferable) {
    return NS_ERROR_INVALID_ARG;
  }

  if (!mTargetWidget) {
    LOGDRAGSERVICE(
        "*** failed: GetData called without a valid target widget!\n");
    return NS_ERROR_FAILURE;
  }

  // get flavor list that includes all acceptable flavors (including
  // ones obtained through conversion).
  nsTArray<nsCString> flavors;
  nsresult rv = aTransferable->FlavorsTransferableCanImport(flavors);
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  failed to get flavors, quit.");
    return rv;
  }

  // check to see if this is an internal list
  bool isList = IsTargetContextList();

  if (isList) {
    LOGDRAGSERVICE("  Process as a list...");
    // find a matching flavor
    for (uint32_t i = 0; i < flavors.Length(); ++i) {
      nsCString& flavorStr = flavors[i];
      LOGDRAGSERVICE("  [%d] flavor is %s\n", i, flavorStr.get());
      // get the item with the right index
      nsCOMPtr<nsITransferable> item =
          do_QueryElementAt(mSourceDataItems, aItemIndex);
      if (!item) continue;

      nsCOMPtr<nsISupports> data;
      LOGDRAGSERVICE("  trying to get transfer data for %s\n", flavorStr.get());
      rv = item->GetTransferData(flavorStr.get(), getter_AddRefs(data));
      if (NS_FAILED(rv)) {
        LOGDRAGSERVICE("  failed.\n");
        continue;
      }
      rv = aTransferable->SetTransferData(flavorStr.get(), data);
      if (NS_FAILED(rv)) {
        LOGDRAGSERVICE("  fail to set transfer data into transferable!\n");
        continue;
      }
      LOGDRAGSERVICE("  succeeded\n");
      // ok, we got the data
      return NS_OK;
    }
    // if we got this far, we failed
    LOGDRAGSERVICE("  failed to match flavors\n");
    return NS_ERROR_FAILURE;
  }

  nsTArray<nsCString> dragFlavors;
  GetDragFlavors(dragFlavors);

  // Now walk down the list of flavors. When we find one that is
  // actually present, copy out the data into the transferable in that
  // format. SetTransferData() implicitly handles conversions.
  for (uint32_t i = 0; i < flavors.Length(); ++i) {
    nsCString& flavorStr = flavors[i];
    GdkAtom gdkFlavor = gdk_atom_intern(flavorStr.get(), FALSE);
    LOGDRAGSERVICE("  we're getting data %s (gdk flavor %p)\n", flavorStr.get(),
                   gdkFlavor);
    bool dataFound = false;
    if (gdkFlavor) {
      GetTargetDragData(gdkFlavor, dragFlavors);
    }
    if (mTargetDragData) {
      LOGDRAGSERVICE("  dataFound = true\n");
      dataFound = true;
    } else {
      LOGDRAGSERVICE("  dataFound = false, try conversions\n");

      // Dragging and dropping from the file manager would cause us
      // to parse the source text as a nsIFile URL.
      if (flavorStr.EqualsLiteral(kFileMime)) {
        LOGDRAGSERVICE("  conversion %s => %s", kFileMime, gTextUriListType);
        gdkFlavor = gdk_atom_intern(gTextUriListType, FALSE);
        GetTargetDragData(gdkFlavor, dragFlavors);
        if (mTargetDragData) {
          const char* text = static_cast<char*>(mTargetDragData);
          char16_t* convertedText = nullptr;
          uint32_t convertedTextLen = 0;

          GetTextUriListItem(text, mTargetDragDataLen, aItemIndex,
                             &convertedText, &convertedTextLen);

          if (convertedText) {
            nsCOMPtr<nsIIOService> ioService = do_GetIOService(&rv);
            nsCOMPtr<nsIURI> fileURI;
            rv = ioService->NewURI(NS_ConvertUTF16toUTF8(convertedText),
                                   nullptr, nullptr, getter_AddRefs(fileURI));
            if (NS_SUCCEEDED(rv)) {
              nsCOMPtr<nsIFileURL> fileURL = do_QueryInterface(fileURI, &rv);
              if (NS_SUCCEEDED(rv)) {
                nsCOMPtr<nsIFile> file;
                rv = fileURL->GetFile(getter_AddRefs(file));
                if (NS_SUCCEEDED(rv)) {
                  // The common wrapping code at the end of
                  // this function assumes the data is text
                  // and calls text-specific operations.
                  // Make a secret hideout here for nsIFile
                  // objects and return early.
                  LOGDRAGSERVICE("  set as file %s",
                                 NS_ConvertUTF16toUTF8(convertedText).get());
                  aTransferable->SetTransferData(flavorStr.get(), file);
                  g_free(convertedText);
                  return NS_OK;
                }
              }
            }
            g_free(convertedText);
          }
          continue;
        }
      }

      // if we are looking for text/unicode and we fail to find it
      // on the clipboard first, try again with text/plain. If that
      // is present, convert it to unicode.
      if (flavorStr.EqualsLiteral(kUnicodeMime)) {
        LOGDRAGSERVICE("  conversion %s => %s", kUnicodeMime,
                       gTextPlainUTF8Type);
        gdkFlavor = gdk_atom_intern(gTextPlainUTF8Type, FALSE);
        GetTargetDragData(gdkFlavor, dragFlavors);
        if (mTargetDragData) {
          const char* castedText = reinterpret_cast<char*>(mTargetDragData);
          char16_t* convertedText = nullptr;
          NS_ConvertUTF8toUTF16 ucs2string(castedText, mTargetDragDataLen);
          convertedText = ToNewUnicode(ucs2string, mozilla::fallible);
          if (convertedText) {
            // out with the old, in with the new
            g_free(mTargetDragData);
            mTargetDragData = convertedText;
            mTargetDragDataLen = ucs2string.Length() * 2;
            dataFound = true;
          }  // if plain text data on clipboard
        } else {
          LOGDRAGSERVICE("  conversion %s => %s", kUnicodeMime, kTextMime);
          gdkFlavor = gdk_atom_intern(kTextMime, FALSE);
          GetTargetDragData(gdkFlavor, dragFlavors);
          if (mTargetDragData) {
            const char* castedText = reinterpret_cast<char*>(mTargetDragData);
            char16_t* convertedText = nullptr;
            uint32_t convertedTextLen = 0;
            UTF8ToNewUTF16(castedText, mTargetDragDataLen, &convertedText,
                           &convertedTextLen);
            if (convertedText) {
              // out with the old, in with the new
              g_free(mTargetDragData);
              mTargetDragData = convertedText;
              mTargetDragDataLen = convertedTextLen * 2;
              dataFound = true;
            }  // if plain text data on clipboard
          }    // if plain text flavor present
        }      // if plain text charset=utf-8 flavor present
      }        // if looking for text/unicode

      // if we are looking for text/x-moz-url and we failed to find
      // it on the clipboard, try again with text/uri-list, and then
      // _NETSCAPE_URL
      if (flavorStr.EqualsLiteral(kURLMime)) {
        LOGDRAGSERVICE("  conversion %s => %s", kURLMime, gTextUriListType);
        gdkFlavor = gdk_atom_intern(gTextUriListType, FALSE);
        GetTargetDragData(gdkFlavor, dragFlavors);
        if (mTargetDragData) {
          const char* data = reinterpret_cast<char*>(mTargetDragData);
          char16_t* convertedText = nullptr;
          uint32_t convertedTextLen = 0;

          GetTextUriListItem(data, mTargetDragDataLen, aItemIndex,
                             &convertedText, &convertedTextLen);

          if (convertedText) {
            // out with the old, in with the new
            g_free(mTargetDragData);
            mTargetDragData = convertedText;
            mTargetDragDataLen = convertedTextLen * 2;
            dataFound = true;
          }
        }
        if (!dataFound) {
          LOGDRAGSERVICE("  conversion %s => %s", kURLMime, gMozUrlType);
          gdkFlavor = gdk_atom_intern(gMozUrlType, FALSE);
          GetTargetDragData(gdkFlavor, dragFlavors);
          if (mTargetDragData) {
            const char* castedText = reinterpret_cast<char*>(mTargetDragData);
            char16_t* convertedText = nullptr;
            uint32_t convertedTextLen = 0;
            UTF8ToNewUTF16(castedText, mTargetDragDataLen, &convertedText,
                           &convertedTextLen);
            if (convertedText) {
              // out with the old, in with the new
              g_free(mTargetDragData);
              mTargetDragData = convertedText;
              mTargetDragDataLen = convertedTextLen * 2;
              dataFound = true;
            }
          }
        }
      }

    }  // else we try one last ditch effort to find our data

    if (dataFound) {
      LOGDRAGSERVICE("  actual data found %s\n",
                     GUniquePtr<gchar>(gdk_atom_name(gdkFlavor)).get());

      if (flavorStr.EqualsLiteral(kJPEGImageMime) ||
          flavorStr.EqualsLiteral(kJPGImageMime) ||
          flavorStr.EqualsLiteral(kPNGImageMime) ||
          flavorStr.EqualsLiteral(kGIFImageMime)) {
        LOGDRAGSERVICE("  saving as image %s\n", flavorStr.get());

        nsCOMPtr<nsIInputStream> byteStream;
        NS_NewByteInputStream(getter_AddRefs(byteStream),
                              Span((char*)mTargetDragData, mTargetDragDataLen),
                              NS_ASSIGNMENT_COPY);
        aTransferable->SetTransferData(flavorStr.get(), byteStream);
        continue;
      }

      if (!flavorStr.EqualsLiteral(kCustomTypesMime)) {
        // the DOM only wants LF, so convert from MacOS line endings
        // to DOM line endings.
        nsLinebreakHelpers::ConvertPlatformToDOMLinebreaks(
            flavorStr, &mTargetDragData,
            reinterpret_cast<int*>(&mTargetDragDataLen));
      }

      // put it into the transferable.
      nsCOMPtr<nsISupports> genericDataWrapper;
      nsPrimitiveHelpers::CreatePrimitiveForData(
          flavorStr, mTargetDragData, mTargetDragDataLen,
          getter_AddRefs(genericDataWrapper));
      aTransferable->SetTransferData(flavorStr.get(), genericDataWrapper);
      // we found one, get out of this loop!
      break;
    }
  }

  return NS_OK;
}

NS_IMETHODIMP
nsDragService::IsDataFlavorSupported(const char* aDataFlavor, bool* _retval) {
  LOGDRAGSERVICE("nsDragService::IsDataFlavorSupported(%p) %s",
                 mTargetDragContext.get(), aDataFlavor);
  if (!_retval) {
    return NS_ERROR_INVALID_ARG;
  }

  // set this to no by default
  *_retval = false;

  // check to make sure that we have a drag object set, here
  if (!mTargetWidget) {
    LOGDRAGSERVICE(
        "*** warning: IsDataFlavorSupported called without a valid target "
        "widget!\n");
    return NS_OK;
  }

  // check to see if the target context is a list.
  bool isList = IsTargetContextList();
  // if it is, just look in the internal data since we are the source
  // for it.
  if (isList) {
    LOGDRAGSERVICE("  It's a list");
    uint32_t numDragItems = 0;
    // if we don't have mDataItems we didn't start this drag so it's
    // an external client trying to fool us.
    if (!mSourceDataItems) {
      LOGDRAGSERVICE("  quit");
      return NS_OK;
    }
    mSourceDataItems->GetLength(&numDragItems);
    LOGDRAGSERVICE("  drag items %d", numDragItems);
    for (uint32_t itemIndex = 0; itemIndex < numDragItems; ++itemIndex) {
      nsCOMPtr<nsITransferable> currItem =
          do_QueryElementAt(mSourceDataItems, itemIndex);
      if (currItem) {
        nsTArray<nsCString> flavors;
        currItem->FlavorsTransferableCanExport(flavors);
        for (uint32_t i = 0; i < flavors.Length(); ++i) {
          LOGDRAGSERVICE("  checking %s against %s\n", flavors[i].get(),
                         aDataFlavor);
          if (flavors[i].Equals(aDataFlavor)) {
            LOGDRAGSERVICE("  found.\n");
            *_retval = true;
          }
        }
      }
    }
    return NS_OK;
  }

  // check the target context vs. this flavor, one at a time
  GList* tmp = nullptr;
  if (mTargetDragContext) {
    tmp = gdk_drag_context_list_targets(mTargetDragContext);
  }

  for (; tmp; tmp = tmp->next) {
    /* Bug 331198 */
    GdkAtom atom = GDK_POINTER_TO_ATOM(tmp->data);
    GUniquePtr<gchar> name(gdk_atom_name(atom));
    if (!name) {
      continue;
    }

    if (strcmp(name.get(), aDataFlavor) == 0) {
      *_retval = true;
    }
    // check for automatic text/uri-list -> text/x-moz-url mapping
    else if (strcmp(name.get(), gTextUriListType) == 0 &&
             (strcmp(aDataFlavor, kURLMime) == 0 ||
              strcmp(aDataFlavor, kFileMime) == 0)) {
      *_retval = true;
    }
    // check for automatic _NETSCAPE_URL -> text/x-moz-url mapping
    else if (strcmp(name.get(), gMozUrlType) == 0 &&
             (strcmp(aDataFlavor, kURLMime) == 0)) {
      *_retval = true;
    }
    // check for auto text/plain -> text/unicode mapping
    else if (strcmp(name.get(), kTextMime) == 0 &&
             (strcmp(aDataFlavor, kUnicodeMime) == 0)) {
      *_retval = true;
    }

    if (*_retval) {
      LOGDRAGSERVICE("  supported, with converting %s => %s", name.get(),
                     aDataFlavor);
    }
  }

  if (!*_retval) {
    LOGDRAGSERVICE("  %s is not supported", aDataFlavor);
  }

  return NS_OK;
}

void nsDragService::ReplyToDragMotion(GdkDragContext* aDragContext,
                                      guint aTime) {
  LOGDRAGSERVICE("nsDragService::ReplyToDragMotion(%p) can drop %d",
                 aDragContext, mCanDrop);

  GdkDragAction action = (GdkDragAction)0;
  if (mCanDrop) {
    // notify the dragger if we can drop
    switch (mDragAction) {
      case DRAGDROP_ACTION_COPY:
        LOGDRAGSERVICE("  set explicit action copy");
        action = GDK_ACTION_COPY;
        break;
      case DRAGDROP_ACTION_LINK:
        LOGDRAGSERVICE("  set explicit action link");
        action = GDK_ACTION_LINK;
        break;
      case DRAGDROP_ACTION_NONE:
        LOGDRAGSERVICE("  set explicit action none");
        action = (GdkDragAction)0;
        break;
      default:
        LOGDRAGSERVICE("  set explicit action move");
        action = GDK_ACTION_MOVE;
        break;
    }
  } else {
    LOGDRAGSERVICE("  mCanDrop is false, disable drop");
  }

  // gdk_drag_status() is a kind of red herring here.
  // It does not control final D&D operation type (copy/move) but controls
  // drop/no-drop D&D state and default cursor type (copy/move).

  // Actual D&D operation is determined by mDragAction which is set by
  // SetDragAction() from UpdateDragAction() or gecko/layout.

  // State passed to gdk_drag_status() sets default D&D cursor type
  // which can be switched by key control (CTRL/SHIFT).
  // If user changes D&D cursor (and D&D operation) we're notified by
  // gdk_drag_context_get_selected_action() and update mDragAction.

  // But if we pass mDragAction back to gdk_drag_status() the D&D operation
  // becames locked and won't be returned when D&D modifiers (CTRL/SHIFT)
  // are released.

  // This gdk_drag_context_get_selected_action() -> gdk_drag_status() ->
  // gdk_drag_context_get_selected_action() cycle happens on Wayland.
  if (widget::GdkIsWaylandDisplay() && action == GDK_ACTION_COPY) {
    LOGDRAGSERVICE("  Wayland: switch copy to move");
    action = GDK_ACTION_MOVE;
  }

  LOGDRAGSERVICE("  gdk_drag_status() action %d", action);
  gdk_drag_status(aDragContext, action, aTime);
}

void nsDragService::EnsureCachedDataValidForContext(
    GdkDragContext* aDragContext) {
  if (mCachedDragContext != (uintptr_t)aDragContext) {
    mCachedData.Clear();
    mCachedDragContext = (uintptr_t)aDragContext;
  }
}

void nsDragService::TargetDataReceived(GtkWidget* aWidget,
                                       GdkDragContext* aContext, gint aX,
                                       gint aY,
                                       GtkSelectionData* aSelectionData,
                                       guint aInfo, guint32 aTime) {
  LOGDRAGSERVICE("nsDragService::TargetDataReceived(%p)", aContext);
  TargetResetData();

  EnsureCachedDataValidForContext(aContext);

  mTargetDragDataReceived = true;
  gint len = gtk_selection_data_get_length(aSelectionData);
  const guchar* data = gtk_selection_data_get_data(aSelectionData);

  GdkAtom target = gtk_selection_data_get_target(aSelectionData);
  GUniquePtr<gchar> name(gdk_atom_name(target));
  nsDependentCString flavor(name.get());

  LOGDRAGSERVICE("  got data, MIME %s", flavor.get());

  if (len > 0 && data) {
    mTargetDragDataLen = len;
    mTargetDragData = g_malloc(mTargetDragDataLen);
    memcpy(mTargetDragData, data, mTargetDragDataLen);

    LOGDRAGSERVICE("  got data, len = %d", mTargetDragDataLen);

    nsTArray<uint8_t> copy;
    if (!copy.SetLength(len, fallible)) {
      return;
    }
    memcpy(copy.Elements(), data, len);

    mCachedData.InsertOrUpdate(flavor, std::move(copy));
  } else {
    LOGDRAGSERVICE("Failed to get data. selection data len was %d\n",
                   mTargetDragDataLen);
    mCachedData.InsertOrUpdate(flavor, nsTArray<uint8_t>());
  }
}

bool nsDragService::IsTargetContextList(void) {
  bool retval = false;

  // gMimeListType drags only work for drags within a single process. The
  // gtk_drag_get_source_widget() function will return nullptr if the source
  // of the drag is another app, so we use it to check if a gMimeListType
  // drop will work or not.
  if (mTargetDragContext &&
      gtk_drag_get_source_widget(mTargetDragContext) == nullptr) {
    return retval;
  }

  GList* tmp = nullptr;
  if (mTargetDragContext) {
    tmp = gdk_drag_context_list_targets(mTargetDragContext);
  }

  // walk the list of context targets and see if one of them is a list
  // of items.
  for (; tmp; tmp = tmp->next) {
    /* Bug 331198 */
    GdkAtom atom = GDK_POINTER_TO_ATOM(tmp->data);
    GUniquePtr<gchar> name(gdk_atom_name(atom));
    if (name && !strcmp(name.get(), gMimeListType)) {
      return true;
    }
  }

  return retval;
}

// Spins event loop, called from eDragTaskMotion handler by
// DispatchMotionEvents().
// Can lead to another round of drag_motion events.
void nsDragService::GetTargetDragData(GdkAtom aFlavor,
                                      nsTArray<nsCString>& aDropFlavors) {
  LOGDRAGSERVICE("nsDragService::GetTargetDragData(%p) '%s'\n",
                 mTargetDragContext.get(),
                 GUniquePtr<gchar>(gdk_atom_name(aFlavor)).get());

  // reset our target data areas
  TargetResetData();

  GUniquePtr<gchar> name(gdk_atom_name(aFlavor));
  nsDependentCString flavor(name.get());

  // Return early when requested MIME is not offered by D&D.
  if (!aDropFlavors.Contains(flavor)) {
    LOGDRAGSERVICE("  %s is missing", flavor.get());
    return;
  }

  if (mTargetDragContext) {
    // We keep a copy of the requested data with the same life-time
    // as mTargetDragContext.
    // Especially with multiple items the same data is requested
    // very often.
    EnsureCachedDataValidForContext(mTargetDragContext);
    if (auto cached = mCachedData.Lookup(flavor)) {
      mTargetDragDataLen = cached->Length();
      LOGDRAGSERVICE("  using cached data for %s, length is %d", flavor.get(),
                     mTargetDragDataLen);

      if (mTargetDragDataLen) {
        mTargetDragData = g_malloc(mTargetDragDataLen);
        memcpy(mTargetDragData, cached->Elements(), mTargetDragDataLen);
      }

      mTargetDragDataReceived = true;
      LOGDRAGSERVICE("  %s found in cache", flavor.get());
      return;
    }

    gtk_drag_get_data(mTargetWidget, mTargetDragContext, aFlavor, mTargetTime);

    LOGDRAGSERVICE("  about to start inner iteration.");
    gtk_main_iteration();

    PRTime entryTime = PR_Now();
    while (!mTargetDragDataReceived && mDoingDrag) {
      // check the number of iterations
      LOGDRAGSERVICE("  doing iteration...\n");
      PR_Sleep(PR_MillisecondsToInterval(10)); /* sleep for 10 ms/iteration */
      if (PR_Now() - entryTime > NS_DND_TIMEOUT) {
        LOGDRAGSERVICE("  failed to get D&D data in time!\n");
        break;
      }
      gtk_main_iteration();
    }
  }

#ifdef MOZ_LOGGING
  if (mTargetDragDataLen && mTargetDragData) {
    LOGDRAGSERVICE("  %s got from system", flavor.get());
  } else {
    LOGDRAGSERVICE("  %s failed to get from system", flavor.get());
  }
#endif
}

void nsDragService::TargetResetData(void) {
  mTargetDragDataReceived = false;
  // make sure to free old data if we have to
  g_free(mTargetDragData);
  mTargetDragData = 0;
  mTargetDragDataLen = 0;
}

static void TargetArrayAddTarget(nsTArray<GtkTargetEntry*>& aTargetArray,
                                 const char* aTarget) {
  GtkTargetEntry* target = (GtkTargetEntry*)g_malloc(sizeof(GtkTargetEntry));
  target->target = g_strdup(aTarget);
  target->flags = 0;
  aTargetArray.AppendElement(target);
  LOGDRAGSERVICESTATIC("adding target %s\n", aTarget);
}

static bool CanExportAsURLTarget(const char16_t* aURLData, uint32_t aURLLen) {
  for (const nsLiteralString& disallowed : kDisallowedExportedSchemes) {
    auto len = disallowed.AsString().Length();
    if (len < aURLLen) {
      if (!memcmp(disallowed.get(), aURLData,
                  /* len is char16_t char count */ len * 2)) {
        LOGDRAGSERVICESTATIC("rejected URL scheme %s\n",
                             NS_ConvertUTF16toUTF8(disallowed).get());
        return false;
      }
    }
  }
  return true;
}

GtkTargetList* nsDragService::GetSourceList(void) {
  if (!mSourceDataItems) {
    return nullptr;
  }

  nsTArray<GtkTargetEntry*> targetArray;
  GtkTargetEntry* targets;
  GtkTargetList* targetList = 0;
  uint32_t targetCount = 0;
  unsigned int numDragItems = 0;

  mSourceDataItems->GetLength(&numDragItems);
  LOGDRAGSERVICE("  numDragItems = %d", numDragItems);

  // Check to see if we're dragging > 1 item.
  if (numDragItems > 1) {
    // as the Xdnd protocol only supports a single item (or is it just
    // gtk's implementation?), we don't advertise all flavours listed
    // in the nsITransferable.

    // the application/x-moz-internal-item-list format, which preserves
    // all information for drags within the same mozilla instance.
    TargetArrayAddTarget(targetArray, gMimeListType);

    // check what flavours are supported so we can decide what other
    // targets to advertise.
    nsCOMPtr<nsITransferable> currItem = do_QueryElementAt(mSourceDataItems, 0);

    if (currItem) {
      nsTArray<nsCString> flavors;
      currItem->FlavorsTransferableCanExport(flavors);
      for (uint32_t i = 0; i < flavors.Length(); ++i) {
        // check if text/x-moz-url is supported.
        // If so, advertise
        // text/uri-list.
        if (flavors[i].EqualsLiteral(kURLMime)) {
          TargetArrayAddTarget(targetArray, gTextUriListType);
          break;
        }
      }
    }  // if item is a transferable
  } else if (numDragItems == 1) {
    nsCOMPtr<nsITransferable> currItem = do_QueryElementAt(mSourceDataItems, 0);
    if (currItem) {
      nsTArray<nsCString> flavors;
      currItem->FlavorsTransferableCanExport(flavors);
      for (uint32_t i = 0; i < flavors.Length(); ++i) {
        nsCString& flavorStr = flavors[i];

        TargetArrayAddTarget(targetArray, flavorStr.get());

        // If there is a file, add the text/uri-list type.
        if (flavorStr.EqualsLiteral(kFileMime)) {
          TargetArrayAddTarget(targetArray, gTextUriListType);
        }
        // Check to see if this is text/unicode.
        // If it is, add text/plain
        // since we automatically support text/plain
        // if we support text/unicode.
        else if (flavorStr.EqualsLiteral(kUnicodeMime)) {
          TargetArrayAddTarget(targetArray, gTextPlainUTF8Type);
          TargetArrayAddTarget(targetArray, kTextMime);
        }
        // Check to see if this is the x-moz-url type.
        // If it is, add _NETSCAPE_URL
        // this is a type used by everybody.
        else if (flavorStr.EqualsLiteral(kURLMime)) {
          nsCOMPtr<nsISupports> data;
          if (NS_SUCCEEDED(currItem->GetTransferData(flavorStr.get(),
                                                     getter_AddRefs(data)))) {
            void* tmpData = nullptr;
            uint32_t tmpDataLen = 0;
            nsPrimitiveHelpers::CreateDataFromPrimitive(
                nsDependentCString(flavorStr.get()), data, &tmpData,
                &tmpDataLen);
            if (tmpData) {
              if (CanExportAsURLTarget(reinterpret_cast<char16_t*>(tmpData),
                                       tmpDataLen / 2)) {
                TargetArrayAddTarget(targetArray, gMozUrlType);
              }
              free(tmpData);
            }
          }
        }
        // check if application/x-moz-file-promise url is supported.
        // If so, advertise text/uri-list.
        else if (flavorStr.EqualsLiteral(kFilePromiseURLMime)) {
          TargetArrayAddTarget(targetArray, gTextUriListType);
        }
        // XdndDirectSave, use on X.org only.
        else if (widget::GdkIsX11Display() && !widget::IsXWaylandProtocol() &&
                 flavorStr.EqualsLiteral(kFilePromiseMime)) {
          TargetArrayAddTarget(targetArray, gXdndDirectSaveType);
        }
        // kNativeImageMime
        else if (flavorStr.EqualsLiteral(kNativeImageMime)) {
          TargetArrayAddTarget(targetArray, kPNGImageMime);
          TargetArrayAddTarget(targetArray, kJPEGImageMime);
          TargetArrayAddTarget(targetArray, kJPGImageMime);
          TargetArrayAddTarget(targetArray, kGIFImageMime);
        }
      }
    }
  }

  // get all the elements that we created.
  targetCount = targetArray.Length();
  if (targetCount) {
    // allocate space to create the list of valid targets
    targets = (GtkTargetEntry*)g_malloc(sizeof(GtkTargetEntry) * targetCount);
    uint32_t targetIndex;
    for (targetIndex = 0; targetIndex < targetCount; ++targetIndex) {
      GtkTargetEntry* disEntry = targetArray.ElementAt(targetIndex);
      // this is a string reference but it will be freed later.
      targets[targetIndex].target = disEntry->target;
      targets[targetIndex].flags = disEntry->flags;
      targets[targetIndex].info = 0;
    }
    targetList = gtk_target_list_new(targets, targetCount);
    // clean up the target list
    for (uint32_t cleanIndex = 0; cleanIndex < targetCount; ++cleanIndex) {
      GtkTargetEntry* thisTarget = targetArray.ElementAt(cleanIndex);
      g_free(thisTarget->target);
      g_free(thisTarget);
    }
    g_free(targets);
  } else {
    // We need to create a dummy target list to be able initialize dnd.
    targetList = gtk_target_list_new(nullptr, 0);
  }
  return targetList;
}

void nsDragService::SourceEndDragSession(GdkDragContext* aContext,
                                         gint aResult) {
  LOGDRAGSERVICE("SourceEndDragSession(%p) result %s\n", aContext,
                 kGtkDragResults[aResult]);

  // this just releases the list of data items that we provide
  mSourceDataItems = nullptr;

  // Remove this property, if it exists, to satisfy the Direct Save Protocol.
  GdkAtom property = gdk_atom_intern(gXdndDirectSaveType, FALSE);
  gdk_property_delete(gdk_drag_context_get_source_window(aContext), property);

  if (!mDoingDrag || mScheduledTask == eDragTaskSourceEnd)
    // EndDragSession() was already called on drop
    // or SourceEndDragSession on drag-failed
    return;

  if (mEndDragPoint.x < 0) {
    // We don't have a drag end point, so guess
    gint x, y;
    GdkDisplay* display = gdk_display_get_default();
    GdkScreen* screen = gdk_display_get_default_screen(display);
    GtkWindow* window = GetGtkWindow(mSourceDocument);
    GdkWindow* gdkWindow = window ? gtk_widget_get_window(GTK_WIDGET(window))
                                  : gdk_screen_get_root_window(screen);
    gdk_window_get_device_position(
        gdkWindow, gdk_drag_context_get_device(aContext), &x, &y, nullptr);
    gint scale = gdk_window_get_scale_factor(gdkWindow);
    SetDragEndPoint(LayoutDeviceIntPoint(x * scale, y * scale));
    LOGDRAGSERVICE("  guess drag end point %d %d\n", x * scale, y * scale);
  }

  // Either the drag was aborted or the drop occurred outside the app.
  // The dropEffect of mDataTransfer is not updated for motion outside the
  // app, but is needed for the dragend event, so set it now.

  uint32_t dropEffect;

  if (aResult == GTK_DRAG_RESULT_SUCCESS) {
    LOGDRAGSERVICE("  drop is accepted");
    // With GTK+ versions 2.10.x and prior the drag may have been
    // cancelled (but no drag-failed signal would have been sent).
    // aContext->dest_window will be non-nullptr only if the drop was
    // sent.
    GdkDragAction action = gdk_drag_context_get_dest_window(aContext)
                               ? gdk_drag_context_get_actions(aContext)
                               : (GdkDragAction)0;

    // Only one bit of action should be set, but, just in case someone
    // does something funny, erring away from MOVE, and not recording
    // unusual action combinations as NONE.
    if (!action) {
      LOGDRAGSERVICE("  drop action is none");
      dropEffect = DRAGDROP_ACTION_NONE;
    } else if (action & GDK_ACTION_COPY) {
      LOGDRAGSERVICE("  drop action is copy");
      dropEffect = DRAGDROP_ACTION_COPY;
    } else if (action & GDK_ACTION_LINK) {
      LOGDRAGSERVICE("  drop action is link");
      dropEffect = DRAGDROP_ACTION_LINK;
    } else if (action & GDK_ACTION_MOVE) {
      LOGDRAGSERVICE("  drop action is move");
      dropEffect = DRAGDROP_ACTION_MOVE;
    } else {
      LOGDRAGSERVICE("  drop action is copy");
      dropEffect = DRAGDROP_ACTION_COPY;
    }
  } else {
    LOGDRAGSERVICE("  drop action is none");
    dropEffect = DRAGDROP_ACTION_NONE;
    if (aResult != GTK_DRAG_RESULT_NO_TARGET) {
      LOGDRAGSERVICE("  drop is user chancelled\n");
      mUserCancelled = true;
    }
  }

  if (mDataTransfer) {
    mDataTransfer->SetDropEffectInt(dropEffect);
  }

  // Schedule the appropriate drag end dom events.
  Schedule(eDragTaskSourceEnd, nullptr, nullptr, LayoutDeviceIntPoint(), 0);
}

static nsresult GetDownloadDetails(nsITransferable* aTransferable,
                                   nsIURI** aSourceURI, nsAString& aFilename) {
  *aSourceURI = nullptr;
  MOZ_ASSERT(aTransferable != nullptr, "aTransferable must not be null");

  // get the URI from the kFilePromiseURLMime flavor
  nsCOMPtr<nsISupports> urlPrimitive;
  nsresult rv = aTransferable->GetTransferData(kFilePromiseURLMime,
                                               getter_AddRefs(urlPrimitive));
  if (NS_FAILED(rv)) {
    return NS_ERROR_FAILURE;
  }
  nsCOMPtr<nsISupportsString> srcUrlPrimitive = do_QueryInterface(urlPrimitive);
  if (!srcUrlPrimitive) {
    return 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;
  rv = aTransferable->GetTransferData(kFilePromiseDestFilename,
                                      getter_AddRefs(fileNamePrimitive));
  if (NS_FAILED(rv)) {
    return NS_ERROR_FAILURE;
  }
  nsCOMPtr<nsISupportsString> srcFileNamePrimitive =
      do_QueryInterface(fileNamePrimitive);
  if (srcFileNamePrimitive) {
    srcFileNamePrimitive->GetData(srcFileName);
  } else {
    nsCOMPtr<nsIURL> sourceURL = do_QueryInterface(sourceURI);
    if (!sourceURL) {
      return NS_ERROR_FAILURE;
    }
    nsAutoCString 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;
}

// See nsContentAreaDragDropDataProvider::GetFlavorData() for reference.
nsresult nsDragService::CreateTempFile(nsITransferable* aItem,
                                       nsACString& aURI) {
  LOGDRAGSERVICE("nsDragService::CreateTempFile()");

  nsCOMPtr<nsIFile> tmpDir;
  nsresult rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(tmpDir));
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  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)) {
    LOGDRAGSERVICE(
        "  Failed to extract file name and source uri from download url");
    return rv;
  }

  // Check if the file is already stored at /tmp.
  // It happens when drop destination is changed and SourceDataGet() is caled
  // more than once.
  nsAutoCString fileName;
  CopyUTF16toUTF8(wideFileName, fileName);
  auto fileLen = fileName.Length();
  for (const auto& url : mTempFileUrls) {
    auto URLLen = url.Length();
    if (URLLen > fileLen &&
        fileName.Equals(nsDependentCString(url, URLLen - fileLen))) {
      aURI = url;
      LOGDRAGSERVICE("  recycle file %s", PromiseFlatCString(aURI).get());
      return NS_OK;
    }
  }

  // create and open channel for source uri
  nsCOMPtr<nsIPrincipal> principal = aItem->GetRequestingPrincipal();
  nsContentPolicyType contentPolicyType = aItem->GetContentPolicyType();
  nsCOMPtr<nsICookieJarSettings> cookieJarSettings =
      aItem->GetCookieJarSettings();
  rv = NS_NewChannel(getter_AddRefs(channel), sourceURI, principal,
                     nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
                     contentPolicyType, cookieJarSettings);
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  Failed to create new channel for source uri");
    return rv;
  }

  rv = channel->Open(getter_AddRefs(inputStream));
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  Failed to open channel for source uri");
    return rv;
  }

  // build the file:///tmp/dnd_file URL
  tmpDir->Append(NS_LITERAL_STRING_FROM_CSTRING("dnd_file"));
  rv = tmpDir->CreateUnique(nsIFile::DIRECTORY_TYPE, 0700);
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  Failed create tmp dir");
    return rv;
  }

  // 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);
  if (mTempFileTimerID) {
    g_source_remove(mTempFileTimerID);
    mTempFileTimerID = 0;
  }

  // extend file:///tmp/dnd_file/<filename> URL
  tmpDir->Append(wideFileName);

  nsCOMPtr<nsIOutputStream> outputStream;
  rv = NS_NewLocalFileOutputStream(getter_AddRefs(outputStream), tmpDir);
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  Failed to open output stream for temporary file");
    return rv;
  }

  char buffer[8192];
  uint32_t readCount = 0;
  uint32_t writeCount = 0;
  while (1) {
    rv = inputStream->Read(buffer, sizeof(buffer), &readCount);
    if (NS_FAILED(rv)) {
      LOGDRAGSERVICE("  Failed to read data from source uri");
      return rv;
    }

    if (readCount == 0) break;

    rv = outputStream->Write(buffer, readCount, &writeCount);
    if (NS_FAILED(rv)) {
      LOGDRAGSERVICE("  Failed to write data to temporary file");
      return rv;
    }
  }

  inputStream->Close();
  rv = outputStream->Close();
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  Failed to write data to temporary file");
    return rv;
  }

  nsCOMPtr<nsIURI> uri;
  rv = NS_NewFileURI(getter_AddRefs(uri), tmpDir);
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  Failed to get file URI");
    return rv;
  }
  nsCOMPtr<nsIURL> fileURL(do_QueryInterface(uri));
  if (!fileURL) {
    LOGDRAGSERVICE("  Failed to query file interface");
    return NS_ERROR_FAILURE;
  }
  rv = fileURL->GetSpec(aURI);
  if (NS_FAILED(rv)) {
    LOGDRAGSERVICE("  Failed to get filepath");
    return rv;
  }

  // store url of temporary file
  mTempFileUrls.AppendElement()->Assign(aURI);
  LOGDRAGSERVICE("  storing tmp file as %s", PromiseFlatCString(aURI).get());
  return NS_OK;
}

bool nsDragService::SourceDataAppendURLFileItem(nsACString& aURI,
                                                nsITransferable* aItem) {
  // If there is a file available, create a URI from the file.
  nsCOMPtr<nsISupports> data;
  nsresult rv = aItem->GetTransferData(kFileMime, getter_AddRefs(data));
  NS_ENSURE_SUCCESS(rv, false);
  if (nsCOMPtr<nsIFile> file = do_QueryInterface(data)) {
    nsCOMPtr<nsIURI> fileURI;
    NS_NewFileURI(getter_AddRefs(fileURI), file);
    if (fileURI) {
      fileURI->GetSpec(aURI);
      return true;
    }
  }
  return false;
}

bool nsDragService::SourceDataAppendURLItem(nsITransferable* aItem,
                                            bool aExternalDrop,
                                            nsACString& aURI) {
  nsCOMPtr<nsISupports> data;
  nsresult rv = aItem->GetTransferData(kURLMime, getter_AddRefs(data));
  if (NS_FAILED(rv)) {
    return SourceDataAppendURLFileItem(aURI, aItem);
  }

  nsCOMPtr<nsISupportsString> string = do_QueryInterface(data);
  if (!string) {
    return false;
  }

  nsAutoString text;
  string->GetData(text);
  if (!aExternalDrop || CanExportAsURLTarget(text.get(), text.Length())) {
    AppendUTF16toUTF8(text, aURI);
    return true;
  }

  // We're dropping to another application and the URL can't be exported
  // as it's internal one (mailbox:// etc.)
  // Try to get file target directly.
  if (SourceDataAppendURLFileItem(aURI, aItem)) {
    return true;
  }

  // We can't get the file directly so try to download it and save to tmp.
  // 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.

  // check whether transferable contains FilePromiseUrl flavor...
  nsCOMPtr<nsISupports> promiseData;
  rv = aItem->GetTransferData(kFilePromiseURLMime, getter_AddRefs(promiseData));
  NS_ENSURE_SUCCESS(rv, false);

  // ... if so, create a temporary file and pass its url
  return NS_SUCCEEDED(CreateTempFile(aItem, aURI));
}

void nsDragService::SourceDataGetUriList(GdkDragContext* aContext,
                                         GtkSelectionData* aSelectionData,
                                         uint32_t aDragItems) {
  // Check if we're transfering data to another application.
  // gdk_drag_context_get_dest_window() on X11 returns GdkWindow even for
  // different application so use nsWindow::GetWindow() to check if that's
  // our window.
  const bool isExternalDrop =
      widget::GdkIsX11Display()
          ? !nsWindow::GetWindow(gdk_drag_context_get_dest_window(aContext))
          : !gdk_drag_context_get_dest_window(aContext);

  LOGDRAGSERVICE("nsDragService::SourceDataGetUriLists() len %d external %d",
                 aDragItems, isExternalDrop);

  // Disable processing of native events until we store all files to /tmp.
  // Otherwise user can quit drop before we have all files saved
  // and that cancels whole D&D.
  AutoSuspendNativeEvents suspend;

  nsAutoCString uriList;
  for (uint32_t i = 0; i < aDragItems; i++) {
    nsCOMPtr<nsITransferable> item = do_QueryElementAt(mSourceDataItems, i);
    if (!item) {
      continue;
    }
    nsAutoCString uri;
    if (!SourceDataAppendURLItem(item, isExternalDrop, uri)) {
      continue;
    }
    // text/x-moz-url is of form url + "\n" + title.
    // We just want the url.
    int32_t separatorPos = uri.FindChar(u'\n');
    if (separatorPos >= 0) {
      uri.Truncate(separatorPos);
    }
    uriList.Append(uri);
    uriList.AppendLiteral("\r\n");
  }

  LOGDRAGSERVICE("URI list\n%s", uriList.get());
  GdkAtom target = gtk_selection_data_get_target(aSelectionData);
  gtk_selection_data_set(aSelectionData, target, 8, (guchar*)uriList.get(),
                         uriList.Length());
}

void nsDragService::SourceDataGetImage(nsITransferable* aItem,
                                       GtkSelectionData* aSelectionData) {
  LOGDRAGSERVICE("nsDragService::SourceDataGetImage()");

  nsresult rv;
  nsCOMPtr<nsISupports> data;
  rv = aItem->GetTransferData(kNativeImageMime, getter_AddRefs(data));
  NS_ENSURE_SUCCESS_VOID(rv);

  LOGDRAGSERVICE("  posting image\n");
  nsCOMPtr<imgIContainer> image = do_QueryInterface(data);
  if (!image) {
    LOGDRAGSERVICE("  do_QueryInterface failed\n");
    return;
  }
  RefPtr<GdkPixbuf> pixbuf = nsImageToPixbuf::ImageToPixbuf(image);
  if (!pixbuf) {
    LOGDRAGSERVICE("  ImageToPixbuf failed\n");
    return;
  }
  gtk_selection_data_set_pixbuf(aSelectionData, pixbuf);
  LOGDRAGSERVICE("  image data set\n");
  return;
}

void nsDragService::SourceDataGetXDND(nsITransferable* aItem,
                                      GdkDragContext* aContext,
                                      GtkSelectionData* aSelectionData) {
  LOGDRAGSERVICE("nsDragService::SourceDataGetXDND");

  // Indicate failure by default.
  GdkAtom target = gtk_selection_data_get_target(aSelectionData);
  gtk_selection_data_set(aSelectionData, target, 8, (guchar*)"E", 1);

  GdkAtom property = gdk_atom_intern(gXdndDirectSaveType, FALSE);
  GdkAtom type = gdk_atom_intern(kTextMime, FALSE);

  GdkWindow* srcWindow = gdk_drag_context_get_source_window(aContext);
  if (!srcWindow) {
    LOGDRAGSERVICE("  failed to get source GdkWindow!");
    return;
  }

  // Ensure null termination.
  nsAutoCString data;
  {
    GUniquePtr<guchar> gdata;
    gint length = 0;
    if (!gdk_property_get(srcWindow, property, type, 0, INT32_MAX, FALSE,
                          nullptr, nullptr, &length, getter_Transfers(gdata))) {
      LOGDRAGSERVICE("  failed to get gXdndDirectSaveType GdkWindow property.");
      return;
    }
    data.Assign(nsDependentCSubstring((const char*)gdata.get(), length));
  }

  GUniquePtr<char> hostname;
  GUniquePtr<char> fullpath(
      g_filename_from_uri(data.get(), getter_Transfers(hostname), nullptr));
  if (!fullpath) {
    LOGDRAGSERVICE("  failed to get file from uri.");
    return;
  }

  // If there is no hostname in the URI, NULL will be stored.
  // We should not accept uris with from a different host.
  if (hostname) {
    nsCOMPtr<nsIPropertyBag2> infoService =
        do_GetService(NS_SYSTEMINFO_CONTRACTID);
    if (!infoService) {
      return;
    }
    nsAutoCString host;
    if (NS_SUCCEEDED(infoService->GetPropertyAsACString(u"host"_ns, host))) {
      if (!host.Equals(hostname.get())) {
        LOGDRAGSERVICE("  ignored drag because of different host.");
        // Special error code "F" for this case.
        gtk_selection_data_set(aSelectionData, target, 8, (guchar*)"F", 1);
        return;
      }
    }
  }

  LOGDRAGSERVICE("  XdndDirectSave filepath is %s", fullpath.get());

  nsCOMPtr<nsIFile> file;
  if (NS_FAILED(NS_NewNativeLocalFile(nsDependentCString(fullpath.get()), false,
                                      getter_AddRefs(file)))) {
    LOGDRAGSERVICE("  failed to get local file");
    return;
  }

  // We have to split the path into a directory and filename,
  // because our internal file-promise API is based on these.
  nsCOMPtr<nsIFile> directory;
  file->GetParent(getter_AddRefs(directory));

  aItem->SetTransferData(kFilePromiseDirectoryMime, directory);

  nsCOMPtr<nsISupportsString> filenamePrimitive =
      do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID);
  if (!filenamePrimitive) {
    return;
  }

  nsAutoString leafName;
  file->GetLeafName(leafName);
  filenamePrimitive->SetData(leafName);

  aItem->SetTransferData(kFilePromiseDestFilename, filenamePrimitive);

  nsCOMPtr<nsISupports> promiseData;
  nsresult rv =
      aItem->GetTransferData(kFilePromiseMime, getter_AddRefs(promiseData));
  NS_ENSURE_SUCCESS_VOID(rv);

  // Indicate success.
  gtk_selection_data_set(aSelectionData, target, 8, (guchar*)"S", 1);
  return;
}

bool nsDragService::SourceDataGetText(nsITransferable* aItem,
                                      const nsACString& aMIMEType,
                                      bool aNeedToDoConversionToPlainText,
                                      GtkSelectionData* aSelectionData) {
  LOGDRAGSERVICE("nsDragService::SourceDataGetPlain()");

  nsresult rv;
  nsCOMPtr<nsISupports> data;
  rv = aItem->GetTransferData(PromiseFlatCString(aMIMEType).get(),
                              getter_AddRefs(data));
  NS_ENSURE_SUCCESS(rv, false);

  void* tmpData = nullptr;
  uint32_t tmpDataLen = 0;

  nsPrimitiveHelpers::CreateDataFromPrimitive(aMIMEType, data, &tmpData,
                                              &tmpDataLen);
  // if required, do the extra work to convert unicode to plain
  // text and replace the output values with the plain text.
  if (aNeedToDoConversionToPlainText) {
    char* plainTextData = nullptr;
    char16_t* castedUnicode = reinterpret_cast<char16_t*>(tmpData);
    uint32_t plainTextLen = 0;
    UTF16ToNewUTF8(castedUnicode, tmpDataLen / 2, &plainTextData,
                   &plainTextLen);
    if (tmpData) {
      // this was not allocated using glib
      free(tmpData);
      tmpData = plainTextData;
      tmpDataLen = plainTextLen;
    }
  }
  if (tmpData) {
    // this copies the data
    GdkAtom target = gtk_selection_data_get_target(aSelectionData);
    gtk_selection_data_set(aSelectionData, target, 8, (guchar*)tmpData,
                           tmpDataLen);
    // this wasn't allocated with glib
    free(tmpData);
  }

  return true;
}

// We're asked to get data from mSourceDataItems and pass it to
// GtkSelectionData (Gtk D&D interface).
// We need to check mSourceDataItems data type and try to convert it
// to data type accepted by Gtk.
void nsDragService::SourceDataGet(GtkWidget* aWidget, GdkDragContext* aContext,
                                  GtkSelectionData* aSelectionData,
                                  guint32 aTime) {
  LOGDRAGSERVICE("nsDragService::SourceDataGet(%p)", aContext);

  GdkAtom target = gtk_selection_data_get_target(aSelectionData);
  GUniquePtr<gchar> requestedTypeName(gdk_atom_name(target));
  if (!requestedTypeName) {
    LOGDRAGSERVICE("  failed to get atom name.\n");
    return;
  }

  LOGDRAGSERVICE("  Gtk asks us for %s data type\n", requestedTypeName.get());
  // check to make sure that we have data items to return.
  if (!mSourceDataItems) {
    LOGDRAGSERVICE("  Failed to get our data items\n");
    return;
  }

  uint32_t dragItems;
  mSourceDataItems->GetLength(&dragItems);
  LOGDRAGSERVICE("  source data items %d", dragItems);

  nsDependentCString mimeFlavor(requestedTypeName.get());
  if (mimeFlavor.EqualsLiteral(gTextUriListType)) {
    SourceDataGetUriList(aContext, aSelectionData, dragItems);
    return;
  }

#ifdef MOZ_LOGGING
  if (dragItems > 1) {
    LOGDRAGSERVICE(
        "  There are %d data items but we're asked for %s MIME type. Only "
        "first data element can be transfered!",
        dragItems, mimeFlavor.get());
  }
#endif

  nsCOMPtr<nsITransferable> item = do_QueryElementAt(mSourceDataItems, 0);
  if (!item) {
    LOGDRAGSERVICE("  Failed to get SourceDataItems!");
    return;
  }

  if (mimeFlavor.EqualsLiteral(kTextMime) ||
      mimeFlavor.EqualsLiteral(gTextPlainUTF8Type)) {
    SourceDataGetText(item, nsDependentCString(kUnicodeMime),
                      /* aNeedToDoConversionToPlainText */ true,
                      aSelectionData);
    // no fallback for text mime types
    return;
  }
  // Someone is asking for the special Direct Save Protocol type.
  else if (mimeFlavor.EqualsLiteral(gXdndDirectSaveType)) {
    SourceDataGetXDND(item, aContext, aSelectionData);
    // no fallback for XDND mime types
    return;
  } else if (mimeFlavor.EqualsLiteral(kPNGImageMime) ||
             mimeFlavor.EqualsLiteral(kJPEGImageMime) ||
             mimeFlavor.EqualsLiteral(kJPGImageMime) ||
             mimeFlavor.EqualsLiteral(kGIFImageMime)) {
    // no fallback for image mime types
    SourceDataGetImage(item, aSelectionData);
    return;
  } else if (mimeFlavor.EqualsLiteral(gMozUrlType)) {
    // Someone was asking for _NETSCAPE_URL. We need to get it from
    // transferable as x-moz-url and convert it to plain text.
    // No need to check
    if (SourceDataGetText(item, nsDependentCString(kURLMime),
                          /* aNeedToDoConversionToPlainText */ true,
                          aSelectionData)) {
      return;
    }
  }
  // Just try to get and set whatever we're asked for.
  SourceDataGetText(item, mimeFlavor,
                    /* aNeedToDoConversionToPlainText */ false, aSelectionData);
}

void nsDragService::SourceBeginDrag(GdkDragContext* aContext) {
  LOGDRAGSERVICE("nsDragService::SourceBeginDrag(%p)\n", aContext);

  nsCOMPtr<nsITransferable> transferable =
      do_QueryElementAt(mSourceDataItems, 0);
  if (!transferable) return;

  nsTArray<nsCString> flavors;
  nsresult rv = transferable->FlavorsTransferableCanImport(flavors);
  NS_ENSURE_SUCCESS(rv, );

  for (uint32_t i = 0; i < flavors.Length(); ++i) {
    if (flavors[i].EqualsLiteral(kFilePromiseDestFilename)) {
      nsCOMPtr<nsISupports> data;
      rv = transferable->GetTransferData(kFilePromiseDestFilename,
                                         getter_AddRefs(data));
      if (NS_FAILED(rv)) {
        LOGDRAGSERVICE("  transferable doesn't contain '%s",
                       kFilePromiseDestFilename);
        return;
      }

      nsCOMPtr<nsISupportsString> fileName = do_QueryInterface(data);
      if (!fileName) {
        LOGDRAGSERVICE("  failed to get file name");
        return;
      }

      nsAutoString fileNameStr;
      fileName->GetData(fileNameStr);

      nsCString fileNameCStr;
      CopyUTF16toUTF8(fileNameStr, fileNameCStr);

      GdkAtom property = gdk_atom_intern(gXdndDirectSaveType, FALSE);
      GdkAtom type = gdk_atom_intern(kTextMime, FALSE);

      gdk_property_change(gdk_drag_context_get_source_window(aContext),
                          property, type, 8, GDK_PROP_MODE_REPLACE,
                          (const guchar*)fileNameCStr.get(),
                          fileNameCStr.Length());
      break;
    }
  }
}

void nsDragService::SetDragIcon(GdkDragContext* aContext) {
  if (!mHasImage && !mSelection) return;

  LOGDRAGSERVICE("nsDragService::SetDragIcon(%p)", aContext);

  LayoutDeviceIntRect dragRect;
  nsPresContext* pc;
  RefPtr<SourceSurface> surface;
  DrawDrag(mSourceNode, mRegion, mScreenPosition, &dragRect, &surface, &pc);
  if (!pc) {
    LOGDRAGSERVICE("  PresContext is missing!");
    return;
  }

  const auto screenPoint =
      LayoutDeviceIntPoint::Round(mScreenPosition * pc->CSSToDevPixelScale());
  int32_t offsetX = screenPoint.x - dragRect.x;
  int32_t offsetY = screenPoint.y - dragRect.y;

  // If a popup is set as the drag image, use its widget. Otherwise, use
  // the surface that DrawDrag created.
  //
  // XXX: Disable drag popups on GTK 3.19.4 and above: see bug 1264454.
  //      Fix this once a new GTK version ships that does not destroy our
  //      widget in gtk_drag_set_icon_widget.
  //      This is fixed in GTK 3.24
  //      by
  //      https://gitlab.gnome.org/GNOME/gtk/-/commit/c27c4e2048acb630feb24c31288f802345e99f4c
  bool gtk_drag_set_icon_widget_is_working =
      gtk_check_version(3, 19, 4) != nullptr ||
      gtk_check_version(3, 24, 0) == nullptr;
  if (mDragPopup && gtk_drag_set_icon_widget_is_working) {
    GtkWidget* gtkWidget = nullptr;
    nsIFrame* frame = mDragPopup->GetPrimaryFrame();
    if (frame) {
      // DrawDrag ensured that this is a popup frame.
      nsCOMPtr<nsIWidget> widget = frame->GetNearestWidget();
      if (widget) {
        gtkWidget = (GtkWidget*)widget->GetNativeData(NS_NATIVE_SHELLWIDGET);
        if (gtkWidget) {
          // When mDragPopup has a parent it's already attached to D&D context.
          // That may happens when D&D operation is aborted but not finished
          // on Gtk side yet so let's remove it now.
          if (GtkWidget* parent = gtk_widget_get_parent(gtkWidget)) {
            gtk_container_remove(GTK_CONTAINER(parent), gtkWidget);
          }
          LOGDRAGSERVICE("  set drag popup [%p]", widget.get());
          OpenDragPopup();
          gtk_drag_set_icon_widget(aContext, gtkWidget, offsetX, offsetY);
          return;
        } else {
          LOGDRAGSERVICE("  NS_NATIVE_SHELLWIDGET is missing!");
        }
      } else {
        LOGDRAGSERVICE("  NearestWidget is missing!");
      }
    } else {
      LOGDRAGSERVICE("  PrimaryFrame is missing!");
    }
  }

  if (surface) {
    LOGDRAGSERVICE("  We have a surface");
    if (!SetAlphaPixmap(surface, aContext, offsetX, offsetY, dragRect)) {
      RefPtr<GdkPixbuf> dragPixbuf = nsImageToPixbuf::SourceSurfaceToPixbuf(
          surface, dragRect.width, dragRect.height);
      if (dragPixbuf) {
        LOGDRAGSERVICE("  set drag pixbuf");
        gtk_drag_set_icon_pixbuf(aContext, dragPixbuf, offsetX, offsetY);
      } else {
        LOGDRAGSERVICE("  SourceSurfaceToPixbuf failed!");
      }
    }
  } else {
    LOGDRAGSERVICE("  Surface is missing!");
  }
}

static void invisibleSourceDragBegin(GtkWidget* aWidget,
                                     GdkDragContext* aContext, gpointer aData) {
  LOGDRAGSERVICESTATIC("invisibleSourceDragBegin (%p)", aContext);
  nsDragService* dragService = (nsDragService*)aData;

  dragService->SourceBeginDrag(aContext);
  dragService->SetDragIcon(aContext);
}

static void invisibleSourceDragDataGet(GtkWidget* aWidget,
                                       GdkDragContext* aContext,
                                       GtkSelectionData* aSelectionData,
                                       guint aInfo, guint32 aTime,
                                       gpointer aData) {
  LOGDRAGSERVICESTATIC("invisibleSourceDragDataGet (%p)", aContext);
  nsDragService* dragService = (nsDragService*)aData;
  dragService->SourceDataGet(aWidget, aContext, aSelectionData, aTime);
}

static gboolean invisibleSourceDragFailed(GtkWidget* aWidget,
                                          GdkDragContext* aContext,
                                          gint aResult, gpointer aData) {
#ifdef MOZ_WAYLAND
  // Wayland and X11 uses different drag results here. When drag target is
  // missing X11 passes GDK_DRAG_CANCEL_NO_TARGET
  // (from gdk_dnd_handle_button_event()/gdkdnd-x11.c)
  // as backend X11 has info about other application windows.
  // Wayland does not have such info so it always passes
  // GDK_DRAG_CANCEL_ERROR error code
  // (see data_source_cancelled/gdkselection-wayland.c).
  // Bug 1527976
  if (widget::GdkIsWaylandDisplay() && aResult == GTK_DRAG_RESULT_ERROR) {
    for (GList* tmp = gdk_drag_context_list_targets(aContext); tmp;
         tmp = tmp->next) {
      GdkAtom atom = GDK_POINTER_TO_ATOM(tmp->data);
      GUniquePtr<gchar> name(gdk_atom_name(atom));
      if (name && !strcmp(name.get(), gTabDropType)) {
        aResult = GTK_DRAG_RESULT_NO_TARGET;
        LOGDRAGSERVICESTATIC("invisibleSourceDragFailed(%p): Wayland tab drop",
                             aContext);
        break;
      }
    }
  }
#endif
  LOGDRAGSERVICESTATIC("invisibleSourceDragFailed(%p) %s", aContext,
                       kGtkDragResults[aResult]);
  nsDragService* dragService = (nsDragService*)aData;
  // End the drag session now (rather than waiting for the drag-end signal)
  // so that operations performed on dropEffect == none can start immediately
  // rather than waiting for the drag-failed animation to finish.
  dragService->SourceEndDragSession(aContext, aResult);

  // We should return TRUE to disable the drag-failed animation iff the
  // source performed an operation when dropEffect was none, but the handler
  // of the dragend DOM event doesn't provide this information.
  return FALSE;
}

static void invisibleSourceDragEnd(GtkWidget* aWidget, GdkDragContext* aContext,
                                   gpointer aData) {
  LOGDRAGSERVICESTATIC("invisibleSourceDragEnd(%p)", aContext);
  nsDragService* dragService = (nsDragService*)aData;

  // The drag has ended.  Release the hostages!
  dragService->SourceEndDragSession(aContext, GTK_DRAG_RESULT_SUCCESS);
}

// The following methods handle responding to GTK drag signals and
// tracking state between these signals.
//
// In general, GTK does not expect us to run the event loop while handling its
// drag signals, however our drag event handlers may run the
// event loop, most often to fetch information about the drag data.
//
// GTK, for example, uses the return value from drag-motion signals to
// determine whether drag-leave signals should be sent.  If an event loop is
// run during drag-motion the XdndLeave message can get processed but when GTK
// receives the message it does not yet know that it needs to send the
// drag-leave signal to our widget.
//
// After a drag-drop signal, we need to reply with gtk_drag_finish().
// However, gtk_drag_finish should happen after the drag-drop signal handler
// returns so that when the Motif drag protocol is used, the
// XmTRANSFER_SUCCESS during gtk_drag_finish is sent after the XmDROP_START
// reply sent on return from the drag-drop signal handler.
//
// Similarly drag-end for a successful drag and drag-failed are not good
// times to run a nested event loop as gtk_drag_drop_finished() and
// gtk_drag_source_info_destroy() don't gtk_drag_clear_source_info() or remove
// drop_timeout until after at least the first of these signals is sent.
// Processing other events (e.g. a slow GDK_DROP_FINISHED reply, or the drop
// timeout) could cause gtk_drag_drop_finished to be called again with the
// same GtkDragSourceInfo, which won't like being destroyed twice.
//
// Therefore we reply to the signals immediately and schedule a task to
// dispatch the Gecko events, which may run the event loop.
//
// Action in response to drag-leave signals is also delayed until the event
// loop runs again so that we find out whether a drag-drop signal follows.
//
// A single task is scheduled to manage responses to all three GTK signals.
// If further signals are received while the task is scheduled, the scheduled
// response is updated, sometimes effectively compressing successive signals.
//
// No Gecko drag events are dispatched (during nested event loops) while other
// Gecko drag events are in flight.  This helps event handlers that may not
// expect nested events, while accessing an event's dataTransfer for example.

gboolean nsDragService::ScheduleMotionEvent(nsWindow* aWindow,
                                            GdkDragContext* aDragContext,
                                            LayoutDeviceIntPoint aWindowPoint,
                                            guint aTime) {
  if (aDragContext && mScheduledTask == eDragTaskMotion) {
    // The drag source has sent another motion message before we've
    // replied to the previous.  That shouldn't happen with Xdnd.  The
    // spec for Motif drags is less clear, but we'll just update the
    // scheduled task with the new position reply only to the most
    // recent message.
    NS_WARNING("Drag Motion message received before previous reply was sent");
  }

  // Returning TRUE means we'll reply with a status message, unless we first
  // get a leave.
  return Schedule(eDragTaskMotion, aWindow, aDragContext, aWindowPoint, aTime);
}

void nsDragService::ScheduleLeaveEvent() {
  // We don't know at this stage whether a drop signal will immediately
  // follow.  If the drop signal gets sent it will happen before we return
  // to the main loop and the scheduled leave task will be replaced.
  if (!Schedule(eDragTaskLeave, nullptr, nullptr, LayoutDeviceIntPoint(), 0)) {
    NS_WARNING("Drag leave after drop");
  }
}

gboolean nsDragService::ScheduleDropEvent(nsWindow* aWindow,
                                          GdkDragContext* aDragContext,
                                          LayoutDeviceIntPoint aWindowPoint,
                                          guint aTime) {
  if (!Schedule(eDragTaskDrop, aWindow, aDragContext, aWindowPoint, aTime)) {
    NS_WARNING("Additional drag drop ignored");
    return FALSE;
  }

  SetDragEndPoint(aWindowPoint);

  // We'll reply with gtk_drag_finish().
  return TRUE;
}

#ifdef MOZ_LOGGING
const char* nsDragService::GetDragServiceTaskName(DragTask aTask) {
  static const char* taskNames[] = {"eDragTaskNone", "eDragTaskMotion",
                                    "eDragTaskLeave", "eDragTaskDrop",
                                    "eDragTaskSourceEnd"};
  MOZ_ASSERT(size_t(aTask) < ArrayLength(taskNames));
  return taskNames[aTask];
}
#endif

gboolean nsDragService::Schedule(DragTask aTask, nsWindow* aWindow,
                                 GdkDragContext* aDragContext,
                                 LayoutDeviceIntPoint aWindowPoint,
                                 guint aTime) {
  // If there is an existing leave or motion task scheduled, then that
  // will be replaced.  When the new task is run, it will dispatch
  // any necessary leave or motion events.

  // If aTask is eDragTaskSourceEnd, then it will replace even a scheduled
  // drop event (which could happen if the drop event has not been processed
  // within the allowed time).  Otherwise, if we haven't yet run a scheduled
  // drop or end task, just say that we are not ready to receive another
  // drop.
  LOGDRAGSERVICE("nsDragService::Schedule(%p) task %s window %p\n",
                 aDragContext, GetDragServiceTaskName(aTask), aWindow);

  if (mScheduledTask == eDragTaskSourceEnd ||
      (mScheduledTask == eDragTaskDrop && aTask != eDragTaskSourceEnd)) {
    LOGDRAGSERVICE("   task does not fit recent task %s, quit!\n",
                   GetDragServiceTaskName(mScheduledTask));
    return FALSE;
  }

  mScheduledTask = aTask;
  mPendingWindow = aWindow;
  mPendingDragContext = aDragContext;
  mPendingWindowPoint = aWindowPoint;
  mPendingTime = aTime;

  if (!mTaskSource) {
    // High priority is used here because we want to process motion events
    // right after drag_motion event handler which is called by Gtk.
    // An ideal scenario is to call TaskDispatchCallback() directly here
    // but we can't do that. TaskDispatchCallback() spins gtk event loop
    // while nsDragService::Schedule() is already called from event loop
    // (by drag_motion* gtk_widget events) so that direct call will cause
    // nested recursion.
    mTaskSource = g_timeout_add_full(G_PRIORITY_HIGH, 0, TaskDispatchCallback,
                                     this, nullptr);
  }

  // We need to reply to drag_motion event on Wayland immediately,
  // see Bug 1730203.
  if (widget::GdkIsWaylandDisplay() && mScheduledTask == eDragTaskMotion) {
    UpdateDragAction(aDragContext);
    ReplyToDragMotion(aDragContext, aTime);
  }

  return TRUE;
}

gboolean nsDragService::TaskDispatchCallback(gpointer data) {
  RefPtr<nsDragService> dragService = static_cast<nsDragService*>(data);
  AutoEventLoop loop(dragService);
  return dragService->RunScheduledTask();
}

gboolean nsDragService::RunScheduledTask() {
  LOGDRAGSERVICE(
      "nsDragService::RunScheduledTask() task %s mTargetWindow %p "
      "mPendingWindow %p\n",
      GetDragServiceTaskName(mScheduledTask), mTargetWindow.get(),
      mPendingWindow.get());

  // Don't run RunScheduledTask() twice. As we use it in main thread only
  // we don't need to be thread safe here.
  if (mScheduledTaskIsRunning) {
    LOGDRAGSERVICE("  sheduled task is already running, quit.");
    return FALSE;
  }
  AutoRestore<bool> guard(mScheduledTaskIsRunning);
  mScheduledTaskIsRunning = true;

  if (mTargetWindow && mTargetWindow != mPendingWindow) {
    LOGDRAGSERVICE("  dispatch eDragExit (%p)\n", mTargetWindow.get());
    mTargetWindow->DispatchDragEvent(eDragExit, mTargetWindowPoint, 0);

    if (!mSourceNode) {
      // The drag that was initiated in a different app. End the drag
      // session, since we're done with it for now (until the user drags
      // back into this app).
      EndDragSession(false, GetCurrentModifiers());
    }
  }

  // It is possible that the pending state has been updated during dispatch
  // of the leave event.  That's fine.

  // Now we collect the pending state because, from this point on, we want
  // to use the same state for all events dispatched.  All state is updated
  // so that when other tasks are scheduled during dispatch here, this
  // task is considered to have already been run.
  bool positionHasChanged = mPendingWindow != mTargetWindow ||
                            mPendingWindowPoint != mTargetWindowPoint;
  DragTask task = mScheduledTask;
  mScheduledTask = eDragTaskNone;
  mTargetWindow = std::move(mPendingWindow);
  mTargetWindowPoint = mPendingWindowPoint;

  if (task == eDragTaskLeave || task == eDragTaskSourceEnd) {
    LOGDRAGSERVICE("  quit, selected task %s\n", GetDragServiceTaskName(task));
    if (task == eDragTaskSourceEnd) {
      // Dispatch drag end events.
      EndDragSession(true, GetCurrentModifiers());
    }

    // Nothing more to do
    // Returning false removes the task source from the event loop.
    mTaskSource = 0;
    return FALSE;
  }

  // This may be the start of a destination drag session.
  StartDragSession();

  // mTargetWidget may be nullptr if the window has been destroyed.
  // (The leave event is not scheduled if a drop task is still scheduled.)
  // We still reply appropriately to indicate that the drop will or didn't
  // succeeed.
  mTargetWidget = mTargetWindow ? mTargetWindow->GetGtkWidget() : nullptr;
  LOGDRAGSERVICE("  start drag session mTargetWindow %p mTargetWidget %p\n",
                 mTargetWindow.get(), mTargetWidget.get());
  LOGDRAGSERVICE("  mPendingDragContext %p => mTargetDragContext %p\n",
                 mPendingDragContext.get(), mTargetDragContext.get());
  mTargetDragContext = std::move(mPendingDragContext);
  mTargetTime = mPendingTime;

  // http://www.whatwg.org/specs/web-apps/current-work/multipage/dnd.html#drag-and-drop-processing-model
  // (as at 27 December 2010) indicates that a "drop" event should only be
  // fired (at the current target element) if the current drag operation is
  // not none.  The current drag operation will only be set to a non-none
  // value during a "dragover" event.
  //
  // If the user has ended the drag before any dragover events have been
  // sent, then the spec recommends skipping the drop (because the current
  // drag operation is none).  However, here we assume that, by releasing
  // the mouse button, the user has indicated that they want to drop, so we
  // proceed with the drop where possible.
  //
  // In order to make the events appear to content in the same way as if the
  // spec is being followed we make sure to dispatch a "dragover" event with
  // appropriate coordinates and check canDrop before the "drop" event.
  //
  // When the Xdnd protocol is used for source/destination communication (as
  // should be the case with GTK source applications) a dragover event
  // should have already been sent during the drag-motion signal, which
  // would have already been received because XdndDrop messages do not
  // contain a position.  However, we can't assume the same when the Motif
  // protocol is used.
  if (task == eDragTaskMotion || positionHasChanged) {
    LOGDRAGSERVICE("  process motion event\n");
    UpdateDragAction();
    TakeDragEventDispatchedToChildProcess();  // Clear the old value.
    DispatchMotionEvents();
    if (task == eDragTaskMotion) {
      if (TakeDragEventDispatchedToChildProcess()) {
        mTargetDragContextForRemote = mTargetDragContext;
      } else {
        // Reply to tell the source whether we can drop and what
        // action would be taken.
        ReplyToDragMotion();
      }
    }
  }

  if (task == eDragTaskDrop) {
    LOGDRAGSERVICE("  process drop task\n");
    gboolean success = DispatchDropEvent();

    // Perhaps we should set the del parameter to TRUE when the drag
    // action is move, but we don't know whether the data was successfully
    // transferred.
    if (mTargetDragContext) {
      LOGDRAGSERVICE("  drag finished\n");
      gtk_drag_finish(mTargetDragContext, success,
                      /* del = */ FALSE, mTargetTime);
    }
    // Make sure to end the drag session. If this drag started in a
    // different app, we won't get a drag_end signal to end it from.
    EndDragSession(true, GetCurrentModifiers());
  }

  // We're done with the drag context.
  LOGDRAGSERVICE("  clear mTargetWindow mTargetWidget and other data\n");
  mTargetWidget = nullptr;
  mTargetDragContext = nullptr;

  // If we got another drag signal while running the sheduled task, that
  // must have happened while running a nested event loop.  Leave the task
  // source on the event loop.
  if (mScheduledTask != eDragTaskNone) return TRUE;

  // We have no task scheduled.
  // Returning false removes the task source from the event loop.
  LOGDRAGSERVICE("  remove task source\n");
  mTaskSource = 0;
  return FALSE;
}

// This will update the drag action based on the information in the
// drag context.  Gtk gets this from a combination of the key settings
// and what the source is offering.

void nsDragService::UpdateDragAction(GdkDragContext* aDragContext) {
  // This doesn't look right.  dragSession.dragAction is used by
  // nsContentUtils::SetDataTransferInEvent() to set the initial
  // dataTransfer.dropEffect, so GdkDragContext::suggested_action would be
  // more appropriate.  GdkDragContext::actions should be used to set
  // dataTransfer.effectAllowed, which doesn't currently happen with
  // external sources.
  LOGDRAGSERVICE("nsDragService::UpdateDragAction(%p)", aDragContext);

  // default is to do nothing
  int action = nsIDragService::DRAGDROP_ACTION_NONE;
  GdkDragAction gdkAction = GDK_ACTION_DEFAULT;
  if (aDragContext) {
    gdkAction = gdk_drag_context_get_actions(aDragContext);
    LOGDRAGSERVICE("  gdk_drag_context_get_actions() returns 0x%X", gdkAction);

    // When D&D modifiers (CTRL/SHIFT) are involved,
    // gdk_drag_context_get_actions() on X11 returns selected action but
    // Wayland returns all allowed actions.

    // So we need to call gdk_drag_context_get_selected_action() on Wayland
    // to get potential D&D modifier.
    // gdk_drag_context_get_selected_action() is also affected by
    // gdk_drag_status(), see nsDragService::ReplyToDragMotion().
    if (widget::GdkIsWaylandDisplay()) {
      GdkDragAction gdkActionSelected =
          gdk_drag_context_get_selected_action(aDragContext);
      LOGDRAGSERVICE("  gdk_drag_context_get_selected_action() returns 0x%X",
                     gdkActionSelected);
      if (gdkActionSelected) {
        gdkAction = gdkActionSelected;
      }
    }
  }

  // set the default just in case nothing matches below
  if (gdkAction & GDK_ACTION_DEFAULT) {
    LOGDRAGSERVICE("  set default move");
    action = nsIDragService::DRAGDROP_ACTION_MOVE;
  }
  // first check to see if move is set
  if (gdkAction & GDK_ACTION_MOVE) {
    LOGDRAGSERVICE("  set explicit move");
    action = nsIDragService::DRAGDROP_ACTION_MOVE;
  } else if (gdkAction & GDK_ACTION_LINK) {
    // then fall to the others
    LOGDRAGSERVICE("  set explicit link");
    action = nsIDragService::DRAGDROP_ACTION_LINK;
  } else if (gdkAction & GDK_ACTION_COPY) {
    // copy is ctrl
    LOGDRAGSERVICE("  set explicit copy");
    action = nsIDragService::DRAGDROP_ACTION_COPY;
  }

  // update the drag information
  SetDragAction(action);
}

void nsDragService::UpdateDragAction() { UpdateDragAction(mTargetDragContext); }

NS_IMETHODIMP
nsDragService::UpdateDragEffect() {
  LOGDRAGSERVICE("nsDragService::UpdateDragEffect() from e10s child process");
  if (mTargetDragContextForRemote) {
    ReplyToDragMotion(mTargetDragContextForRemote, mTargetTime);
    mTargetDragContextForRemote = nullptr;
  }
  return NS_OK;
}

void nsDragService::ReplyToDragMotion() {
  if (mTargetDragContext) {
    ReplyToDragMotion(mTargetDragContext, mTargetTime);
  }
}

void nsDragService::DispatchMotionEvents() {
  FireDragEventAtSource(eDrag, GetCurrentModifiers());
  if (mTargetWindow) {
    mTargetWindow->DispatchDragEvent(eDragOver, mTargetWindowPoint,
                                     mTargetTime);
  }
}

// Returns true if the drop was successful
gboolean nsDragService::DispatchDropEvent() {
  // We need to check IsDestroyed here because the nsRefPtr
  // only protects this from being deleted, it does NOT protect
  // against nsView::~nsView() calling Destroy() on it, bug 378273.
  if (!mTargetWindow || mTargetWindow->IsDestroyed()) {
    return FALSE;
  }

  EventMessage msg = mCanDrop ? eDrop : eDragExit;

  mTargetWindow->DispatchDragEvent(msg, mTargetWindowPoint, mTargetTime);

  return mCanDrop;
}

/* static */
uint32_t nsDragService::GetCurrentModifiers() {
  return mozilla::widget::KeymapWrapper::ComputeCurrentKeyModifiers();
}

#undef LOGDRAGSERVICE