compositor: send error for surface role resets

With the more accurate definition of wl_surface roles in Wayland,
enforce the restriction: a role is always set permanently, and
attempting to change it is a protocol error.

This patch is based on Jasper's patch:
http://lists.freedesktop.org/archives/wayland-devel/2014-August/016811.html

The difference in this patch compared to his are:

- send role errors on the interface whose request triggers it, not on
  wl_surface

- an interface could have several requests assigning different roles,
  cannot use wl_interface as the unique key; use an arbitary string
  instead

- ensure in window-manager.c that create_shell_surface() ->
  create_common_surface() is never called with surface->configure set,
  to avoid compositor abort

- use wl_resource_post_no_memory() where appropriate instead of
  hand-rolling it with wl_resource_post_error()

Ideally we would not add weston_surface::role_name field, but use
weston_surface::configure. At the moment this is not possible though,
because at least shell.c uses several different roles with the same
configure function. Drag'n'drop uses two configure functions for the
same role. The configure hook is also reset in several places,
which is not good for role tracking.

This patch overlooks the wl_surface roles assigned in privileged
extensions: screensaver, panel, background, lock, input panel.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Jasper St. Pierre <jstpierre@mecheye.net>

1 files changed, 6 insertions, 5 deletions

diff --git a/src/data-device.c b/src/data-device.c
index 75fc60cb..a8ab4e8c 100644
--- a/src/data-device.c
+++ b/src/data-device.c
@@ -666,11 +666,12 @@ data_device_start_drag(struct wl_client *client, struct wl_resource *resource,
 		source = wl_resource_get_user_data(source_resource);
 	if (icon_resource)
 		icon = wl_resource_get_user_data(icon_resource);
-	if (icon && icon->configure) {
-		wl_resource_post_error(icon_resource,
-				       WL_DISPLAY_ERROR_INVALID_OBJECT,
-				       "surface->configure already set");
-		return;
+
+	if (icon) {
+		if (weston_surface_set_role(icon, "wl_data_device-icon",
+					    resource,
+					    WL_DATA_DEVICE_ERROR_ROLE) < 0)
+			return;
 	}
 
 	if (is_pointer_grab)