/*
 * Copyright © 2011 Kristian Høgsberg
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

/* The file is based on src/data-device.c from Weston */

#include "config.h"

#include "wayland/meta-wayland-data-device.h"

#include <gio/gunixoutputstream.h>
#include <glib-unix.h>
#include <glib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "compositor/meta-dnd-actor-private.h"
#include "core/meta-selection-private.h"
#include "meta/meta-selection-source-memory.h"
#include "wayland/meta-selection-source-wayland-private.h"
#include "wayland/meta-wayland-dnd-surface.h"
#include "wayland/meta-wayland-pointer.h"
#include "wayland/meta-wayland-private.h"
#include "wayland/meta-wayland-seat.h"

#define ROOTWINDOW_DROP_MIME "application/x-rootwindow-drop"

static void unset_selection_source (MetaWaylandDataDevice *data_device,
                                    MetaSelectionType      selection_type);

static void
drag_grab_data_source_destroyed (gpointer data, GObject *where_the_object_was);

static struct wl_resource * create_and_send_clipboard_offer (MetaWaylandDataDevice *data_device,
                                                             struct wl_resource    *target);

static MetaDisplay *
display_from_data_device (MetaWaylandDataDevice *data_device)
{
  MetaWaylandCompositor *compositor =
    meta_wayland_seat_get_compositor (data_device->seat);
  MetaContext *context = meta_wayland_compositor_get_context (compositor);

  return meta_context_get_display (context);
}

static void
move_resources (struct wl_list *destination,
                struct wl_list *source)
{
  wl_list_insert_list (destination, source);
  wl_list_init (source);
}

static void
move_resources_for_client (struct wl_list   *destination,
			   struct wl_list   *source,
			   struct wl_client *client)
{
  struct wl_resource *resource, *tmp;
  wl_resource_for_each_safe (resource, tmp, source)
    {
      if (wl_resource_get_client (resource) == client)
        {
          wl_list_remove (wl_resource_get_link (resource));
          wl_list_insert (destination, wl_resource_get_link (resource));
        }
    }
}

static void
unbind_resource (struct wl_resource *resource)
{
  wl_list_remove (wl_resource_get_link (resource));
}

static void
default_destructor (struct wl_client   *client,
                    struct wl_resource *resource)
{
  wl_resource_destroy (resource);
}

static struct wl_resource *
create_and_send_dnd_offer (MetaWaylandDataSource *source,
                           struct wl_resource *target)
{
  MetaWaylandCompositor *compositor;
  MetaWaylandDataOffer *offer;
  struct wl_array *mime_types;
  struct wl_resource *resource;
  char **p;

  compositor = meta_wayland_data_source_get_compositor (source);
  offer = meta_wayland_data_offer_new (compositor,
                                       META_SELECTION_DND,
                                       source, target);
  resource = meta_wayland_data_offer_get_resource (offer);

  wl_data_device_send_data_offer (target, resource);

  mime_types = meta_wayland_data_source_get_mime_types (source);

  wl_array_for_each (p, mime_types)
    wl_data_offer_send_offer (resource, *p);

  meta_wayland_data_offer_update_action (offer);
  meta_wayland_data_source_set_current_offer (source, offer);

  return resource;
}

struct _MetaWaylandDragGrab {
  MetaWaylandPointerGrab  generic;

  MetaWaylandKeyboardGrab keyboard_grab;

  MetaWaylandSeat        *seat;
  struct wl_client       *drag_client;

  MetaWaylandSurface     *drag_focus;
  gulong                  drag_focus_destroy_handler_id;
  struct wl_resource     *drag_focus_data_device;
  struct wl_listener      drag_focus_listener;

  MetaWaylandSurface     *drag_surface;
  struct wl_listener      drag_icon_listener;

  MetaWaylandDataSource  *drag_data_source;

  ClutterActor           *feedback_actor;

  MetaWaylandSurface     *drag_origin;
  struct wl_listener      drag_origin_listener;

  int                     drag_start_x, drag_start_y;
  ClutterModifierType     buttons;

  guint                   need_initial_focus : 1;
};

static void
set_selection_source (MetaWaylandDataDevice *data_device,
                      MetaSelectionType      selection_type,
                      MetaSelectionSource   *selection_source)

{
  MetaDisplay *display = display_from_data_device (data_device);

  meta_selection_set_owner (meta_display_get_selection (display),
                            selection_type, selection_source);
  g_set_object (&data_device->owners[selection_type], selection_source);
}

static void
unset_selection_source (MetaWaylandDataDevice *data_device,
                        MetaSelectionType      selection_type)
{
  MetaDisplay *display = display_from_data_device (data_device);

  if (!data_device->owners[selection_type])
    return;

  meta_selection_unset_owner (meta_display_get_selection (display),
                              selection_type,
                              data_device->owners[selection_type]);
  g_clear_object (&data_device->owners[selection_type]);
}

static void
destroy_drag_focus (struct wl_listener *listener,
                    void               *data)
{
  MetaWaylandDragGrab *grab = wl_container_of (listener, grab, drag_focus_listener);

  grab->drag_focus_data_device = NULL;
  wl_list_remove (&grab->drag_focus_listener.link);

  g_clear_signal_handler (&grab->drag_focus_destroy_handler_id,
                          grab->drag_focus);
  grab->drag_focus = NULL;
}

static void
on_drag_focus_destroyed (MetaWaylandSurface  *surface,
                         MetaWaylandDragGrab *grab)
{
  meta_wayland_surface_drag_dest_focus_out (grab->drag_focus);
  grab->drag_focus = NULL;
}

static void
meta_wayland_drag_grab_set_source (MetaWaylandDragGrab   *drag_grab,
                                   MetaWaylandDataSource *source)
{
  if (drag_grab->drag_data_source)
    g_object_weak_unref (G_OBJECT (drag_grab->drag_data_source),
                         drag_grab_data_source_destroyed,
                         drag_grab);

  drag_grab->drag_data_source = source;

  if (source)
    g_object_weak_ref (G_OBJECT (source),
                       drag_grab_data_source_destroyed,
                       drag_grab);
}

static void
meta_wayland_drag_source_fake_acceptance (MetaWaylandDataSource *source,
                                          const gchar           *mimetype)
{
  uint32_t actions, user_action, action = 0;

  meta_wayland_data_source_get_actions (source, &actions);
  user_action = meta_wayland_data_source_get_user_action (source);

  /* Pick a suitable action */
  if ((user_action & actions) != 0)
    action = user_action;
  else if (actions != 0)
    action = 1 << (ffs (actions) - 1);

  /* Bail out if there is none, source didn't cooperate */
  if (action == 0)
    return;

  meta_wayland_data_source_target (source, mimetype);
  meta_wayland_data_source_set_current_action (source, action);
  meta_wayland_data_source_set_has_target (source, TRUE);
}

void
meta_wayland_drag_grab_set_focus (MetaWaylandDragGrab *drag_grab,
                                  MetaWaylandSurface  *surface)
{
  MetaWaylandSeat *seat = drag_grab->seat;
  MetaWaylandDataSource *source = drag_grab->drag_data_source;
  struct wl_client *client;
  struct wl_resource *data_device_resource, *offer = NULL;

  if (!drag_grab->need_initial_focus &&
      drag_grab->drag_focus == surface)
    return;

  drag_grab->need_initial_focus = FALSE;

  if (drag_grab->drag_focus)
    {
      meta_wayland_surface_drag_dest_focus_out (drag_grab->drag_focus);
      g_clear_signal_handler (&drag_grab->drag_focus_destroy_handler_id,
                              drag_grab->drag_focus);
      drag_grab->drag_focus = NULL;
    }

  if (source)
    meta_wayland_data_source_set_current_offer (source, NULL);

  if (!surface && source &&
      meta_wayland_data_source_has_mime_type (source, ROOTWINDOW_DROP_MIME))
    meta_wayland_drag_source_fake_acceptance (source, ROOTWINDOW_DROP_MIME);
  else if (source)
    meta_wayland_data_source_target (source, NULL);

  if (!surface)
    return;

  if (!source &&
      wl_resource_get_client (surface->resource) != drag_grab->drag_client)
    return;

  client = wl_resource_get_client (surface->resource);

  data_device_resource = wl_resource_find_for_client (&seat->data_device.resource_list, client);
  if (!data_device_resource)
    {
      data_device_resource =
        wl_resource_find_for_client (&seat->data_device.focus_resource_list,
                                     client);
    }

  if (source && data_device_resource)
    offer = create_and_send_dnd_offer (source, data_device_resource);

  drag_grab->drag_focus = surface;
  drag_grab->drag_focus_destroy_handler_id =
    g_signal_connect (surface, "destroy",
                      G_CALLBACK (on_drag_focus_destroyed),
                      drag_grab);
  drag_grab->drag_focus_data_device = data_device_resource;

  meta_wayland_surface_drag_dest_focus_in (drag_grab->drag_focus,
                                           offer ? wl_resource_get_user_data (offer) : NULL);
}

MetaWaylandSurface *
meta_wayland_drag_grab_get_focus (MetaWaylandDragGrab *drag_grab)
{
  return drag_grab->drag_focus;
}

void
meta_wayland_drag_grab_update_feedback_actor (MetaWaylandDragGrab *drag_grab,
                                              const ClutterEvent  *event)
{
  meta_feedback_actor_update (META_FEEDBACK_ACTOR (drag_grab->feedback_actor),
                              event);
}

static void
drag_grab_focus (MetaWaylandPointerGrab *grab,
                 MetaWaylandSurface     *surface)
{
  MetaWaylandDragGrab *drag_grab = (MetaWaylandDragGrab*) grab;

  meta_wayland_drag_grab_set_focus (drag_grab, surface);
}

static void
data_source_update_user_dnd_action (MetaWaylandDataSource *source,
                                    ClutterModifierType    modifiers)
{
  enum wl_data_device_manager_dnd_action user_dnd_action = 0;

  if (modifiers & CLUTTER_SHIFT_MASK)
    user_dnd_action = WL_DATA_DEVICE_MANAGER_DND_ACTION_MOVE;
  else if (modifiers & CLUTTER_CONTROL_MASK)
    user_dnd_action = WL_DATA_DEVICE_MANAGER_DND_ACTION_COPY;
  else if (modifiers & (CLUTTER_MOD1_MASK | CLUTTER_BUTTON2_MASK))
    user_dnd_action = WL_DATA_DEVICE_MANAGER_DND_ACTION_ASK;

  meta_wayland_data_source_set_user_action (source, user_dnd_action);
}

static void
drag_grab_motion (MetaWaylandPointerGrab *grab,
		  const ClutterEvent     *event)
{
  MetaWaylandDragGrab *drag_grab = (MetaWaylandDragGrab*) grab;
  graphene_point_t point;
  uint32_t time_ms;

  if (drag_grab->drag_focus)
    {
      clutter_event_get_coords (event, &point.x, &point.y);
      time_ms = clutter_event_get_time (event);
      meta_wayland_surface_drag_dest_motion (drag_grab->drag_focus,
                                             point.x, point.y, time_ms);
    }

  if (drag_grab->drag_surface)
    meta_feedback_actor_update (META_FEEDBACK_ACTOR (drag_grab->feedback_actor),
                                event);
}

static void
data_device_end_drag_grab (MetaWaylandDragGrab *drag_grab)
{
  MetaWaylandDataDevice *data_device = &drag_grab->seat->data_device;

  meta_wayland_drag_grab_set_source (drag_grab, NULL);
  meta_wayland_drag_grab_set_focus (drag_grab, NULL);

  if (drag_grab->drag_origin)
    {
      drag_grab->drag_origin = NULL;
      wl_list_remove (&drag_grab->drag_origin_listener.link);
    }

  if (drag_grab->drag_surface)
    {
      drag_grab->drag_surface = NULL;
      wl_list_remove (&drag_grab->drag_icon_listener.link);
    }

  if (drag_grab->feedback_actor)
    {
      clutter_actor_remove_all_children (drag_grab->feedback_actor);
      clutter_actor_destroy (drag_grab->feedback_actor);
    }

  drag_grab->seat->data_device.current_grab = NULL;

  /* There might be other grabs created in result to DnD actions like popups
   * on "ask" actions, we must not reset those, only our own.
   */
  if (drag_grab->generic.pointer->grab == (MetaWaylandPointerGrab *) drag_grab)
    {
      MetaDisplay *display = display_from_data_device (data_device);

      meta_wayland_pointer_end_grab (drag_grab->generic.pointer);
      meta_wayland_keyboard_end_grab (drag_grab->keyboard_grab.keyboard);
      meta_display_sync_wayland_input_focus (display);
    }

  g_free (drag_grab);
}

static gboolean
on_fake_read_hup (GIOChannel   *channel,
                  GIOCondition  condition,
                  gpointer      data)
{
  MetaWaylandDataSource *source = data;

  meta_wayland_data_source_notify_finish (source);
  g_io_channel_shutdown (channel, FALSE, NULL);
  g_io_channel_unref (channel);

  return G_SOURCE_REMOVE;
}

static void
meta_wayland_data_source_fake_read (MetaWaylandDataSource *source,
                                    const gchar           *mimetype)
{
  GIOChannel *channel;
  int p[2];

  if (!g_unix_open_pipe (p, FD_CLOEXEC, NULL))
    {
      meta_wayland_data_source_notify_finish (source);
      return;
    }

  if (!g_unix_set_fd_nonblocking (p[0], TRUE, NULL) ||
      !g_unix_set_fd_nonblocking (p[1], TRUE, NULL))
    {
      meta_wayland_data_source_notify_finish (source);
      close (p[0]);
      close (p[1]);
      return;
    }

  meta_wayland_data_source_send (source, mimetype, p[1]);
  close (p[1]);
  channel = g_io_channel_unix_new (p[0]);
  g_io_channel_set_close_on_unref (channel, TRUE);
  g_io_add_watch (channel, G_IO_HUP, on_fake_read_hup, source);
}

static void
drag_grab_button (MetaWaylandPointerGrab *grab,
                  const ClutterEvent     *event)
{
  MetaWaylandDragGrab *drag_grab = (MetaWaylandDragGrab*) grab;
  MetaWaylandSeat *seat = drag_grab->seat;
  ClutterEventType event_type = clutter_event_type (event);

  if (drag_grab->generic.pointer->grab_button ==
      clutter_event_get_button (event) &&
      event_type == CLUTTER_BUTTON_RELEASE)
    {
      MetaWaylandDataSource *source = drag_grab->drag_data_source;
      gboolean success;

      if (drag_grab->drag_focus && source &&
          meta_wayland_data_source_has_target (source) &&
          meta_wayland_data_source_get_current_action (source))
        {
          meta_wayland_surface_drag_dest_drop (drag_grab->drag_focus);
          meta_wayland_data_source_notify_drop_performed (source);

          meta_wayland_data_source_update_in_ask (source);
          success = TRUE;
        }
      else if (!drag_grab->drag_focus && source &&
               meta_wayland_data_source_has_target (source) &&
               meta_wayland_data_source_get_current_action (source) &&
               meta_wayland_data_source_has_mime_type (source,
                                                       ROOTWINDOW_DROP_MIME))
        {
          /* Perform a fake read, that will lead to notify_finish() being called */
          meta_wayland_data_source_fake_read (source, ROOTWINDOW_DROP_MIME);
          success = TRUE;
        }
      else
        {
          if (source)
            meta_wayland_data_source_set_current_offer (source, NULL);
          meta_wayland_data_device_set_dnd_source (&seat->data_device, NULL);
          unset_selection_source (&seat->data_device, META_SELECTION_DND);
          success = FALSE;
        }

      /* Finish drag and let actor self-destruct */
      meta_dnd_actor_drag_finish (META_DND_ACTOR (drag_grab->feedback_actor),
                                  success);
      drag_grab->feedback_actor = NULL;
    }

  if (seat->pointer->button_count == 0 &&
      event_type == CLUTTER_BUTTON_RELEASE)
    data_device_end_drag_grab (drag_grab);
}

static const MetaWaylandPointerGrabInterface drag_grab_interface = {
  drag_grab_focus,
  drag_grab_motion,
  drag_grab_button,
};

static gboolean
keyboard_drag_grab_key (MetaWaylandKeyboardGrab *grab,
                        const ClutterEvent      *event)
{
  if (clutter_event_get_key_symbol (event) == CLUTTER_KEY_Escape)
    {
      MetaWaylandDragGrab *drag_grab;

      drag_grab = wl_container_of (grab, drag_grab, keyboard_grab);
      meta_wayland_data_device_set_dnd_source (&drag_grab->seat->data_device,
                                               NULL);
      unset_selection_source (&drag_grab->seat->data_device, META_SELECTION_DND);
      meta_wayland_data_source_set_current_offer (drag_grab->drag_data_source,
                                                  NULL);
      meta_dnd_actor_drag_finish (META_DND_ACTOR (drag_grab->feedback_actor),
                                  FALSE);
      drag_grab->feedback_actor = NULL;
      data_device_end_drag_grab (drag_grab);

      return TRUE;
    }

  return FALSE;
}

static void
keyboard_drag_grab_modifiers (MetaWaylandKeyboardGrab *grab,
                              ClutterModifierType      modifiers)
{
  MetaWaylandDragGrab *drag_grab;

  drag_grab = wl_container_of (grab, drag_grab, keyboard_grab);

  /* The modifiers here just contain keyboard modifiers, mix it with the
   * mouse button modifiers we got when starting the drag operation.
   */
  modifiers |= drag_grab->buttons;

  if (drag_grab->drag_data_source)
    {
      data_source_update_user_dnd_action (drag_grab->drag_data_source, modifiers);

      if (drag_grab->drag_focus)
        meta_wayland_surface_drag_dest_update (drag_grab->drag_focus);
    }
}

static const MetaWaylandKeyboardGrabInterface keyboard_drag_grab_interface = {
  keyboard_drag_grab_key,
  keyboard_drag_grab_modifiers
};

static void
destroy_data_device_origin (struct wl_listener *listener,
                            void               *data)
{
  MetaWaylandDragGrab *drag_grab =
    wl_container_of (listener, drag_grab, drag_origin_listener);

  drag_grab->drag_origin = NULL;
  meta_wayland_data_device_set_dnd_source (&drag_grab->seat->data_device, NULL);
  unset_selection_source (&drag_grab->seat->data_device, META_SELECTION_DND);
  meta_wayland_data_source_set_current_offer (drag_grab->drag_data_source, NULL);
  data_device_end_drag_grab (drag_grab);
}

static void
drag_grab_data_source_destroyed (gpointer  data,
                                 GObject  *where_the_object_was)
{
  MetaWaylandDragGrab *drag_grab = data;

  drag_grab->drag_data_source = NULL;
  data_device_end_drag_grab (drag_grab);
}

static void
destroy_data_device_icon (struct wl_listener *listener,
                          void               *data)
{
  MetaWaylandDragGrab *drag_grab =
    wl_container_of (listener, drag_grab, drag_icon_listener);

  drag_grab->drag_surface = NULL;
  wl_list_remove (&drag_grab->drag_icon_listener.link);

  if (drag_grab->feedback_actor)
    clutter_actor_remove_all_children (drag_grab->feedback_actor);
}

void
meta_wayland_data_device_start_drag (MetaWaylandDataDevice                 *data_device,
                                     struct wl_client                      *client,
                                     const MetaWaylandPointerGrabInterface *funcs,
                                     MetaWaylandSurface                    *surface,
                                     MetaWaylandDataSource                 *source,
                                     MetaWaylandSurface                    *icon_surface)
{
  MetaWaylandSeat *seat = wl_container_of (data_device, seat, data_device);
  MetaWaylandDragGrab *drag_grab;
  graphene_point_t pos, surface_pos;
  ClutterModifierType modifiers;
  MetaSurfaceActor *surface_actor;

  data_device->current_grab = drag_grab = g_new0 (MetaWaylandDragGrab, 1);

  drag_grab->generic.interface = funcs;
  drag_grab->generic.pointer = seat->pointer;

  drag_grab->keyboard_grab.interface = &keyboard_drag_grab_interface;
  drag_grab->keyboard_grab.keyboard = seat->keyboard;

  drag_grab->drag_client = client;
  drag_grab->seat = seat;

  drag_grab->drag_origin = surface;
  drag_grab->drag_origin_listener.notify = destroy_data_device_origin;
  wl_resource_add_destroy_listener (surface->resource,
                                    &drag_grab->drag_origin_listener);

  surface_actor = meta_wayland_surface_get_actor (surface);

  clutter_actor_transform_stage_point (CLUTTER_ACTOR (surface_actor),
                                       seat->pointer->grab_x,
                                       seat->pointer->grab_y,
                                       &surface_pos.x, &surface_pos.y);
  drag_grab->drag_start_x = surface_pos.x;
  drag_grab->drag_start_y = surface_pos.y;

  drag_grab->need_initial_focus = TRUE;

  clutter_seat_query_state (clutter_input_device_get_seat (seat->pointer->device),
                            seat->pointer->device, NULL, NULL, &modifiers);
  drag_grab->buttons = modifiers &
    (CLUTTER_BUTTON1_MASK | CLUTTER_BUTTON2_MASK | CLUTTER_BUTTON3_MASK |
     CLUTTER_BUTTON4_MASK | CLUTTER_BUTTON5_MASK);

  meta_wayland_drag_grab_set_source (drag_grab, source);
  meta_wayland_data_device_set_dnd_source (data_device,
                                           drag_grab->drag_data_source);
  data_source_update_user_dnd_action (source, modifiers);

  if (icon_surface)
    {
      MetaDisplay *display = display_from_data_device (data_device);
      MetaCompositor *compositor = meta_display_get_compositor (display);
      ClutterActor *drag_surface_actor;

      drag_grab->drag_surface = icon_surface;

      drag_grab->drag_icon_listener.notify = destroy_data_device_icon;
      wl_resource_add_destroy_listener (icon_surface->resource,
                                        &drag_grab->drag_icon_listener);

      drag_surface_actor =
        CLUTTER_ACTOR (meta_wayland_surface_get_actor (drag_grab->drag_surface));

      drag_grab->feedback_actor =
        meta_dnd_actor_new (compositor,
                            CLUTTER_ACTOR (surface_actor),
                            drag_grab->drag_start_x,
                            drag_grab->drag_start_y);
      meta_feedback_actor_set_anchor (META_FEEDBACK_ACTOR (drag_grab->feedback_actor),
                                      0, 0);
      clutter_actor_add_child (drag_grab->feedback_actor, drag_surface_actor);

      clutter_seat_query_state (clutter_input_device_get_seat (seat->pointer->device),
                                seat->pointer->device, NULL, &pos, NULL);
      meta_feedback_actor_set_position (META_FEEDBACK_ACTOR (drag_grab->feedback_actor),
                                        pos.x, pos.y);
    }

  meta_wayland_pointer_start_grab (seat->pointer,
                                   (MetaWaylandPointerGrab*) drag_grab);
  meta_wayland_data_source_set_seat (source, seat);
}

void
meta_wayland_data_device_end_drag (MetaWaylandDataDevice *data_device)
{
  if (data_device->current_grab)
    data_device_end_drag_grab (data_device->current_grab);
}

static void
data_device_start_drag (struct wl_client  *client,
                        struct wl_resource *resource,
                        struct wl_resource *source_resource,
                        struct wl_resource *origin_resource,
                        struct wl_resource *icon_resource,
                        uint32_t            serial)
{
  MetaWaylandDataDevice *data_device = wl_resource_get_user_data (resource);
  MetaWaylandSeat *seat = wl_container_of (data_device, seat, data_device);
  MetaWaylandSurface *surface = NULL, *icon_surface = NULL;
  MetaWaylandDataSource *drag_source = NULL;
  MetaSelectionSource *selection_source;

  if (origin_resource)
    surface = wl_resource_get_user_data (origin_resource);

  if (!surface)
    return;

  if (seat->pointer->button_count == 0 ||
      seat->pointer->grab_serial != serial ||
      !seat->pointer->focus_surface ||
      seat->pointer->focus_surface != surface)
    return;

  /* FIXME: Check that the data source type array isn't empty. */

  if (data_device->current_grab ||
      seat->pointer->grab != &seat->pointer->default_grab)
    return;

  if (icon_resource)
    icon_surface = wl_resource_get_user_data (icon_resource);
  if (source_resource)
    drag_source = wl_resource_get_user_data (source_resource);

  if (icon_resource &&
      !meta_wayland_surface_assign_role (icon_surface,
                                         META_TYPE_WAYLAND_SURFACE_ROLE_DND,
                                         NULL))
    {
      wl_resource_post_error (resource, WL_DATA_DEVICE_ERROR_ROLE,
                              "wl_surface@%d already has a different role",
                              wl_resource_get_id (icon_resource));
      return;
    }

  selection_source = meta_selection_source_wayland_new (drag_source);
  set_selection_source (data_device, META_SELECTION_DND,
                        selection_source);
  g_object_unref (selection_source);

  meta_wayland_pointer_set_focus (seat->pointer, NULL);
  meta_wayland_data_device_start_drag (data_device, client,
                                       &drag_grab_interface,
                                       surface, drag_source, icon_surface);

  if (meta_wayland_seat_has_keyboard (seat))
    meta_wayland_keyboard_start_grab (seat->keyboard,
                                      &seat->data_device.current_grab->keyboard_grab);
}

static void
selection_data_source_destroyed (gpointer data, GObject *object_was_here)
{
  MetaWaylandDataDevice *data_device = data;

  data_device->selection_data_source = NULL;
  unset_selection_source (data_device, META_SELECTION_CLIPBOARD);
}

static void
meta_wayland_drag_dest_focus_in (MetaWaylandDataDevice *data_device,
                                 MetaWaylandSurface    *surface,
                                 MetaWaylandDataOffer  *offer)
{
  MetaWaylandDragGrab *grab = data_device->current_grab;
  MetaWaylandDataSource *source;
  struct wl_display *display;
  struct wl_client *client;
  struct wl_resource *resource;
  uint32_t source_actions;
  wl_fixed_t sx, sy;

  if (!grab->drag_focus_data_device)
    return;

  client = wl_resource_get_client (surface->resource);
  display = wl_client_get_display (client);

  grab->drag_focus_listener.notify = destroy_drag_focus;
  wl_resource_add_destroy_listener (grab->drag_focus_data_device,
                                    &grab->drag_focus_listener);

  resource = meta_wayland_data_offer_get_resource (offer);

  if (wl_resource_get_version (resource) >=
      WL_DATA_OFFER_SOURCE_ACTIONS_SINCE_VERSION)
    {
      source = meta_wayland_data_offer_get_source (offer);
      meta_wayland_data_source_get_actions (source, &source_actions);
      wl_data_offer_send_source_actions (resource, source_actions);
    }

  meta_wayland_pointer_get_relative_coordinates (grab->generic.pointer,
                                                 surface, &sx, &sy);
  wl_data_device_send_enter (grab->drag_focus_data_device,
                             wl_display_next_serial (display),
                             surface->resource, sx, sy, resource);
}

static void
meta_wayland_drag_dest_focus_out (MetaWaylandDataDevice *data_device,
                                  MetaWaylandSurface    *surface)
{
  MetaWaylandDragGrab *grab = data_device->current_grab;

  if (!grab->drag_focus_data_device)
    return;

  wl_data_device_send_leave (grab->drag_focus_data_device);
  wl_list_remove (&grab->drag_focus_listener.link);
  grab->drag_focus_data_device = NULL;
}

static void
meta_wayland_drag_dest_motion (MetaWaylandDataDevice *data_device,
                               MetaWaylandSurface    *surface,
                               float                  x,
                               float                  y,
                               uint32_t               time_ms)
{
  MetaWaylandDragGrab *grab = data_device->current_grab;
  wl_fixed_t sx, sy;

  if (!grab->drag_focus_data_device)
    return;

  meta_wayland_pointer_get_relative_coordinates (grab->generic.pointer,
                                                 grab->drag_focus,
                                                 &sx, &sy);
  wl_data_device_send_motion (grab->drag_focus_data_device,
                              time_ms,
                              sx, sy);
}

static void
meta_wayland_drag_dest_drop (MetaWaylandDataDevice *data_device,
                             MetaWaylandSurface    *surface)
{
  MetaWaylandDragGrab *grab = data_device->current_grab;

  if (!grab->drag_focus_data_device)
    return;

  wl_data_device_send_drop (grab->drag_focus_data_device);
}

static void
meta_wayland_drag_dest_update (MetaWaylandDataDevice *data_device,
                               MetaWaylandSurface    *surface)
{
}

static const MetaWaylandDragDestFuncs meta_wayland_drag_dest_funcs = {
  meta_wayland_drag_dest_focus_in,
  meta_wayland_drag_dest_focus_out,
  meta_wayland_drag_dest_motion,
  meta_wayland_drag_dest_drop,
  meta_wayland_drag_dest_update
};

const MetaWaylandDragDestFuncs *
meta_wayland_data_device_get_drag_dest_funcs (void)
{
  return &meta_wayland_drag_dest_funcs;
}

static void
dnd_data_source_destroyed (gpointer  data,
                           GObject  *object_was_here)
{
  MetaWaylandDataDevice *data_device = data;

  data_device->dnd_data_source = NULL;
  unset_selection_source (data_device, META_SELECTION_DND);
}

void
meta_wayland_data_device_set_dnd_source (MetaWaylandDataDevice *data_device,
                                         MetaWaylandDataSource *source)
{
  if (data_device->dnd_data_source == source)
    return;

  if (data_device->dnd_data_source)
    {
      g_object_weak_unref (G_OBJECT (data_device->dnd_data_source),
                           dnd_data_source_destroyed,
                           data_device);
    }

  data_device->dnd_data_source = source;

  if (source)
    {
      g_object_weak_ref (G_OBJECT (source),
                         dnd_data_source_destroyed,
                         data_device);
    }
}

void
meta_wayland_data_device_set_selection (MetaWaylandDataDevice *data_device,
                                        MetaWaylandDataSource *source,
                                        uint32_t               serial)
{
  MetaWaylandSeat *seat = wl_container_of (data_device, seat, data_device);
  MetaSelectionSource *selection_source;

  if (data_device->selection_data_source &&
      data_device->selection_serial - serial < UINT32_MAX / 2)
    return;

  if (data_device->selection_data_source)
    {
      g_object_weak_unref (G_OBJECT (data_device->selection_data_source),
                           selection_data_source_destroyed,
                           data_device);
      data_device->selection_data_source = NULL;
    }

  data_device->selection_data_source = source;
  data_device->selection_serial = serial;

  if (source)
    {
      meta_wayland_data_source_set_seat (source, seat);
      g_object_weak_ref (G_OBJECT (source),
                         selection_data_source_destroyed,
                         data_device);

      selection_source = meta_selection_source_wayland_new (source);
    }
  else
    {
      selection_source = g_object_new (META_TYPE_SELECTION_SOURCE_MEMORY, NULL);
    }

  set_selection_source (data_device, META_SELECTION_CLIPBOARD,
                        selection_source);
  g_object_unref (selection_source);
}

static void
data_device_set_selection (struct wl_client   *client,
                           struct wl_resource *resource,
                           struct wl_resource *source_resource,
                           uint32_t            serial)
{
  MetaWaylandDataDevice *data_device = wl_resource_get_user_data (resource);
  MetaWaylandSeat *seat = wl_container_of (data_device, seat, data_device);
  MetaWaylandDataSource *source;

  if (source_resource)
    source = wl_resource_get_user_data (source_resource);
  else
    source = NULL;

  if (source)
    {
      if (meta_wayland_data_source_get_actions (source, NULL))
        {
          wl_resource_post_error(source_resource,
                                 WL_DATA_SOURCE_ERROR_INVALID_SOURCE,
                                 "cannot set drag-and-drop source as selection");
          return;
        }
    }

  if (wl_resource_get_client (resource) !=
      meta_wayland_keyboard_get_focus_client (seat->keyboard))
    {
      if (source)
        meta_wayland_data_source_cancel (source);
      return;
    }

  /* FIXME: Store serial and check against incoming serial here. */
  meta_wayland_data_device_set_selection (data_device, source, serial);
}

static const struct wl_data_device_interface data_device_interface = {
  data_device_start_drag,
  data_device_set_selection,
  default_destructor,
};

static void
create_data_source (struct wl_client   *client,
                    struct wl_resource *resource,
                    uint32_t            id)
{
  MetaWaylandCompositor *compositor = wl_resource_get_user_data (resource);
  struct wl_resource *source_resource;

  source_resource = wl_resource_create (client, &wl_data_source_interface,
                                        wl_resource_get_version (resource), id);
  meta_wayland_data_source_new (compositor, source_resource);
}

static void
owner_changed_cb (MetaSelection         *selection,
                  MetaSelectionType      selection_type,
                  MetaSelectionSource   *new_owner,
                  MetaWaylandDataDevice *data_device)
{
  MetaDisplay *display = meta_selection_get_display (selection);
  MetaContext *context = meta_display_get_context (display);
  MetaWaylandCompositor *compositor =
    meta_context_get_wayland_compositor (context);
  MetaWaylandSeat *seat = compositor->seat;
  struct wl_resource *data_device_resource;
  struct wl_client *focus_client;

  focus_client = meta_wayland_keyboard_get_focus_client (seat->keyboard);
  if (!focus_client)
    return;

  if (selection_type == META_SELECTION_CLIPBOARD)
    {
      wl_resource_for_each (data_device_resource,
                            &data_device->focus_resource_list)
        {
          struct wl_resource *offer = NULL;

          if (new_owner)
            {
              offer = create_and_send_clipboard_offer (data_device,
                                                       data_device_resource);
            }

          wl_data_device_send_selection (data_device_resource, offer);
        }
    }
}

static void
ensure_owners_changed_handler_connected (MetaWaylandDataDevice *data_device)
{
  MetaDisplay *display;

  if (data_device->selection_owner_signal_id != 0)
    return;

  display = display_from_data_device (data_device);
  data_device->selection_owner_signal_id =
    g_signal_connect (meta_display_get_selection (display),
                      "owner-changed",
                      G_CALLBACK (owner_changed_cb), data_device);
}

static void
get_data_device (struct wl_client   *client,
                 struct wl_resource *manager_resource,
                 uint32_t            id,
                 struct wl_resource *seat_resource)
{
  MetaWaylandSeat *seat = wl_resource_get_user_data (seat_resource);
  struct wl_resource *cr;
  struct wl_resource *data_device_resource;

  cr = wl_resource_create (client, &wl_data_device_interface,
                           wl_resource_get_version (manager_resource), id);
  wl_resource_set_implementation (cr, &data_device_interface,
                                  &seat->data_device, unbind_resource);

  data_device_resource =
    wl_resource_find_for_client (&seat->data_device.resource_list, client);
  if (data_device_resource)
    {
      wl_list_remove (wl_resource_get_link (data_device_resource));
      wl_list_init (wl_resource_get_link (data_device_resource));
    }

  wl_list_insert (&seat->data_device.resource_list, wl_resource_get_link (cr));

  ensure_owners_changed_handler_connected (&seat->data_device);
}

static const struct wl_data_device_manager_interface manager_interface = {
  create_data_source,
  get_data_device
};

static void
bind_manager (struct wl_client *client,
              void             *data,
              uint32_t          version,
              uint32_t          id)
{
  MetaWaylandCompositor *compositor = data;
  struct wl_resource *resource;

  resource = wl_resource_create (client, &wl_data_device_manager_interface,
                                 version, id);
  wl_resource_set_implementation (resource, &manager_interface,
                                  compositor, NULL);
}

void
meta_wayland_data_device_manager_init (MetaWaylandCompositor *compositor)
{
  if (wl_global_create (compositor->wayland_display,
			&wl_data_device_manager_interface,
			META_WL_DATA_DEVICE_MANAGER_VERSION,
			compositor, bind_manager) == NULL)
    g_error ("Could not create data_device");
}

void
meta_wayland_data_device_init (MetaWaylandDataDevice *data_device,
                               MetaWaylandSeat       *seat)
{
  data_device->seat = seat;
  wl_list_init (&data_device->resource_list);
  wl_list_init (&data_device->focus_resource_list);
}

MetaWaylandSeat *
meta_wayland_data_device_get_seat (MetaWaylandDataDevice *data_device)
{
  return data_device->seat;
}

static struct wl_resource *
create_and_send_clipboard_offer (MetaWaylandDataDevice *data_device,
                                 struct wl_resource    *target)
{
  MetaWaylandDataOffer *offer;
  MetaWaylandCompositor *compositor =
    meta_wayland_seat_get_compositor (data_device->seat);
  MetaContext *context = meta_wayland_compositor_get_context (compositor);
  MetaDisplay *display = meta_context_get_display (context);
  struct wl_resource *resource;
  GList *mimetypes, *l;

  mimetypes = meta_selection_get_mimetypes (meta_display_get_selection (display),
                                            META_SELECTION_CLIPBOARD);
  if (!mimetypes)
    return NULL;

  offer = meta_wayland_data_offer_new (compositor,
                                       META_SELECTION_CLIPBOARD,
                                       NULL, target);
  resource = meta_wayland_data_offer_get_resource (offer);

  wl_data_device_send_data_offer (target, resource);

  for (l = mimetypes; l; l = l->next)
    wl_data_offer_send_offer (resource, l->data);

  g_list_free_full (mimetypes, g_free);

  return resource;
}

void
meta_wayland_data_device_set_keyboard_focus (MetaWaylandDataDevice *data_device)
{
  MetaWaylandSeat *seat = wl_container_of (data_device, seat, data_device);
  struct wl_client *focus_client;
  struct wl_resource *data_device_resource;

  focus_client = meta_wayland_keyboard_get_focus_client (seat->keyboard);

  if (focus_client == data_device->focus_client)
    return;

  data_device->focus_client = focus_client;
  move_resources (&data_device->resource_list,
                  &data_device->focus_resource_list);

  if (!focus_client)
    return;

  move_resources_for_client (&data_device->focus_resource_list,
                             &data_device->resource_list,
                             focus_client);

  wl_resource_for_each (data_device_resource, &data_device->focus_resource_list)
    {
      struct wl_resource *offer;

      offer = create_and_send_clipboard_offer (data_device,
                                               data_device_resource);
      wl_data_device_send_selection (data_device_resource, offer);
    }
}

MetaWaylandDragGrab *
meta_wayland_data_device_get_current_grab (MetaWaylandDataDevice *data_device)
{
  return data_device->current_grab;
}

void
meta_wayland_data_device_unset_dnd_selection (MetaWaylandDataDevice *data_device)
{
  unset_selection_source (data_device, META_SELECTION_DND);
}
