[gtk+/gtk-3-16] wayland: Create internal GdkWindow to be set as the DnD source

[Matthias Clasen <matthiasc src gnome org>]

commit 77c5cef932a3004f8615e73a60c7796d57d84351
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Apr 7 16:23:38 2015 +0200

    wayland: Create internal GdkWindow to be set as the DnD source
    
    During drag operations from another client, we currently set no window as
    the DnD source. There's paths in upper layers though that rely on it being
    set, just that we don't trigger these yet.

 gdk/wayland/gdkdevice-wayland.c |   31 +++++++++++++++++++++++++++++--
 1 files changed, 29 insertions(+), 2 deletions(-)
---
diff --git a/gdk/wayland/gdkdevice-wayland.c b/gdk/wayland/gdkdevice-wayland.c
index a22351b..0708372 100644
--- a/gdk/wayland/gdkdevice-wayland.c
+++ b/gdk/wayland/gdkdevice-wayland.c
@@ -95,6 +95,9 @@ struct _GdkWaylandDeviceData
   struct wl_surface *pointer_surface;
   guint current_output_scale;
   GSList *pointer_surface_outputs;
+
+  /* Source/dest for non-local dnd */
+  GdkWindow *foreign_dnd_window;
 };
 
 struct _GdkWaylandDevice
@@ -623,8 +626,10 @@ data_device_enter (void                  *data,
 
   dnd_owner = gdk_selection_owner_get_for_display (device->display, gdk_drag_get_selection 
(device->drop_context));
 
-  if (dnd_owner)
-    _gdk_wayland_drag_context_set_source_window (device->drop_context, dnd_owner);
+  if (!dnd_owner)
+    dnd_owner = device->foreign_dnd_window;
+
+  _gdk_wayland_drag_context_set_source_window (device->drop_context, dnd_owner);
 
   _gdk_wayland_drag_context_set_dest_window (device->drop_context,
                                              dest_window, serial);
@@ -1838,6 +1843,26 @@ static const struct wl_surface_listener pointer_surface_listener = {
   pointer_surface_leave
 };
 
+static GdkWindow *
+create_foreign_dnd_window (GdkDisplay *display)
+{
+  GdkWindowAttr attrs;
+  GdkScreen *screen;
+  guint mask;
+
+  screen = gdk_display_get_default_screen (display);
+
+  attrs.x = attrs.y = 0;
+  attrs.width = attrs.height = 1;
+  attrs.wclass = GDK_INPUT_OUTPUT;
+  attrs.window_type = GDK_WINDOW_TEMP;
+  attrs.visual = gdk_screen_get_system_visual (screen);
+
+  mask = GDK_WA_X | GDK_WA_Y | GDK_WA_VISUAL;
+
+  return gdk_window_new (gdk_screen_get_root_window (screen), &attrs, mask);
+}
+
 void
 _gdk_wayland_device_manager_add_seat (GdkDeviceManager *device_manager,
                                       guint32           id,
@@ -1857,6 +1882,7 @@ _gdk_wayland_device_manager_add_seat (GdkDeviceManager *device_manager,
   device->device_manager = device_manager;
   device->touches = g_hash_table_new_full (NULL, NULL, NULL,
                                            (GDestroyNotify) g_free);
+  device->foreign_dnd_window = create_foreign_dnd_window (display);
   device->wl_seat = wl_seat;
 
   wl_seat_add_listener (device->wl_seat, &seat_listener, device);
@@ -1898,6 +1924,7 @@ _gdk_wayland_device_manager_remove_seat (GdkDeviceManager *manager,
           /* FIXME: destroy data_device */
           g_clear_object (&device->keyboard_settings);
           g_hash_table_destroy (device->touches);
+          gdk_window_destroy (device->foreign_dnd_window);
           g_free (device);
 
           break;