[mutter] wayland: Keep track of the origin surface and drag point on DnD

[Jasper St. Pierre <jstpierre src gnome org>]

commit 0510c3a62149d5897c9f04f67614cce4d65153af
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Sep 30 17:01:43 2014 +0200

    wayland: Keep track of the origin surface and drag point on DnD
    
    Keeping track of the surface will be necessary in case it is destroyed
    during DnD, and the coordinates will be useful when figuring out the
    snap back coordinates.

 src/wayland/meta-wayland-data-device.c |   48 +++++++++++++++++++++++++++++--
 1 files changed, 44 insertions(+), 4 deletions(-)
---
diff --git a/src/wayland/meta-wayland-data-device.c b/src/wayland/meta-wayland-data-device.c
index ed2e4f8..ffa8d7d 100644
--- a/src/wayland/meta-wayland-data-device.c
+++ b/src/wayland/meta-wayland-data-device.c
@@ -177,6 +177,11 @@ struct _MetaWaylandDragGrab {
 
   MetaWaylandDataSource  *drag_data_source;
   struct wl_listener      drag_data_source_listener;
+
+  MetaWaylandSurface     *drag_origin;
+  struct wl_listener      drag_origin_listener;
+
+  int                     drag_start_x, drag_start_y;
 };
 
 static void
@@ -262,6 +267,12 @@ drag_grab_motion (MetaWaylandPointerGrab *grab,
 static void
 data_device_end_drag_grab (MetaWaylandDragGrab *drag_grab)
 {
+  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;
@@ -304,6 +315,16 @@ static const MetaWaylandPointerGrabInterface drag_grab_interface = {
 };
 
 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;
+  data_device_end_drag_grab (drag_grab);
+}
+
+static void
 destroy_data_device_source (struct wl_listener *listener, void *data)
 {
   MetaWaylandDragGrab *drag_grab =
@@ -331,12 +352,20 @@ data_device_start_drag (struct wl_client *client,
 {
   MetaWaylandDataDevice *data_device = wl_resource_get_user_data (resource);
   MetaWaylandSeat *seat = wl_container_of (data_device, seat, data_device);
+  MetaWaylandSurface *surface = NULL;
   MetaWaylandDragGrab *drag_grab;
+  ClutterPoint pos;
 
-  if ((seat->pointer.button_count == 0 ||
-       seat->pointer.grab_serial != serial ||
-       !seat->pointer.focus_surface ||
-       seat->pointer.focus_surface != wl_resource_get_user_data (origin_resource)))
+  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. */
@@ -353,6 +382,17 @@ data_device_start_drag (struct wl_client *client,
   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 (origin_resource,
+                                    &drag_grab->drag_origin_listener);
+
+  clutter_input_device_get_coords (seat->pointer.device, NULL, &pos);
+  clutter_actor_transform_stage_point (CLUTTER_ACTOR (meta_surface_actor_get_texture 
(surface->surface_actor)),
+                                       pos.x, pos.y, &pos.x, &pos.y);
+  drag_grab->drag_start_x = pos.x;
+  drag_grab->drag_start_y = pos.y;
+
   if (source_resource)
     {
       drag_grab->drag_data_source = wl_resource_get_user_data (source_resource);