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>

desktop-shell/shell.c

@@ -3463,10 +3463,7 @@ create_common_surface(struct shell_client *owner, void *shell,
 {
 	struct shell_surface *shsurf;
 
-	if (surface->configure) {
-		weston_log("surface->configure already set\n");
-		return NULL;
-	}
+	assert(surface->configure == NULL);
 
 	shsurf = calloc(1, sizeof *shsurf);
 	if (!shsurf) {
@@ -3579,18 +3576,13 @@ shell_get_shell_surface(struct wl_client *client,
 	struct desktop_shell *shell = sc->shell;
 	struct shell_surface *shsurf;
 
-	if (get_shell_surface(surface)) {
-		wl_resource_post_error(surface_resource,
-				       WL_DISPLAY_ERROR_INVALID_OBJECT,
-				       "desktop_shell::get_shell_surface already requested");
+	if (weston_surface_set_role(surface, "wl_shell_surface",
+				    resource, WL_SHELL_ERROR_ROLE) < 0)
 		return;
-	}
 
 	shsurf = create_common_surface(sc, shell, surface, &shell_client);
 	if (!shsurf) {
-		wl_resource_post_error(surface_resource,
-				       WL_DISPLAY_ERROR_INVALID_OBJECT,
-				       "surface->configure already set");
+		wl_resource_post_no_memory(surface_resource);
 		return;
 	}
 
@@ -3899,18 +3891,13 @@ xdg_get_xdg_surface(struct wl_client *client,
 	struct desktop_shell *shell = sc->shell;
 	struct shell_surface *shsurf;
 
-	if (get_shell_surface(surface)) {
-		wl_resource_post_error(surface_resource,
-				       WL_DISPLAY_ERROR_INVALID_OBJECT,
-				       "xdg_shell::get_xdg_surface already requested");
+	if (weston_surface_set_role(surface, "xdg_surface",
+				    resource, XDG_SHELL_ERROR_ROLE) < 0)
 		return;
-	}
 
 	shsurf = create_xdg_surface(sc, shell, surface, &xdg_client);
 	if (!shsurf) {
-		wl_resource_post_error(surface_resource,
-				       WL_DISPLAY_ERROR_INVALID_OBJECT,
-				       "surface->configure already set");
+		wl_resource_post_no_memory(surface_resource);
 		return;
 	}
 
@@ -3997,12 +3984,9 @@ xdg_get_xdg_popup(struct wl_client *client,
 	struct weston_surface *parent;
 	struct shell_seat *seat;
 
-	if (get_shell_surface(surface)) {
-		wl_resource_post_error(surface_resource,
-				       WL_DISPLAY_ERROR_INVALID_OBJECT,
-				       "xdg_shell::get_xdg_popup already requested");
+	if (weston_surface_set_role(surface, "xdg_popup",
+				    resource, XDG_SHELL_ERROR_ROLE) < 0)
 		return;
-	}
 
 	if (!parent_resource) {
 		wl_resource_post_error(surface_resource,
@@ -4017,9 +4001,7 @@ xdg_get_xdg_popup(struct wl_client *client,
 	shsurf = create_xdg_popup(sc, shell, surface, &xdg_popup_client,
 				  parent, seat, serial, x, y);
 	if (!shsurf) {
-		wl_resource_post_error(surface_resource,
-				       WL_DISPLAY_ERROR_INVALID_OBJECT,
-				       "surface->configure already set");
+		wl_resource_post_no_memory(surface_resource);
 		return;
 	}
 

src/compositor.c

@@ -2764,6 +2764,31 @@ weston_surface_get_main_surface(struct weston_surface *surface)
 	return surface;
 }
 
+WL_EXPORT int
+weston_surface_set_role(struct weston_surface *surface,
+			const char *role_name,
+			struct wl_resource *error_resource,
+			uint32_t error_code)
+{
+	assert(role_name);
+
+	if (surface->role_name == NULL ||
+	    surface->role_name == role_name ||
+	    strcmp(surface->role_name, role_name) == 0) {
+		surface->role_name = role_name;
+
+		return 0;
+	}
+
+	wl_resource_post_error(error_resource, error_code,
+			       "Cannot assign role %s to wl_surface@%d,"
+			       " already has role %s\n",
+			       role_name,
+			       wl_resource_get_id(surface->resource),
+			       surface->role_name);
+	return -1;
+}
+
 static void
 subsurface_set_position(struct wl_client *client,
 			struct wl_resource *resource, int32_t x, int32_t y)
@@ -3099,13 +3124,9 @@ subcompositor_get_subsurface(struct wl_client *client,
 		return;
 	}
 
-	if (surface->configure) {
-		wl_resource_post_error(resource,
-			WL_SUBCOMPOSITOR_ERROR_BAD_SURFACE,
-			"%s%d: wl_surface@%d already has a role",
-			where, id, wl_resource_get_id(surface_resource));
+	if (weston_surface_set_role(surface, "wl_subsurface", resource,
+				    WL_SUBCOMPOSITOR_ERROR_BAD_SURFACE) < 0)
 		return;
-	}
 
 	if (weston_surface_get_main_surface(parent) == surface) {
 		wl_resource_post_error(resource,

src/compositor.h

@@ -908,6 +908,15 @@ struct weston_surface {
 	 */
 	struct wl_list subsurface_list; /* weston_subsurface::parent_link */
 	struct wl_list subsurface_list_pending; /* ...::parent_link_pending */
+
+	/*
+	 * For tracking protocol role assignments. Different roles may
+	 * have the same configure hook, e.g. in shell.c. Configure hook
+	 * may get reset, this will not.
+	 * XXX: map configure functions 1:1 to roles, and never reset it,
+	 * and replace role_name with configure.
+	 */
+	const char *role_name;
 };
 
 struct weston_subsurface {
@@ -1231,6 +1240,12 @@ weston_surface_unmap(struct weston_surface *surface);
 struct weston_surface *
 weston_surface_get_main_surface(struct weston_surface *surface);
 
+int
+weston_surface_set_role(struct weston_surface *surface,
+			const char *role_name,
+			struct wl_resource *error_resource,
+			uint32_t error_code);
+
 struct weston_buffer *
 weston_buffer_from_resource(struct wl_resource *resource);
 

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)

src/input.c

@@ -1640,14 +1640,11 @@ pointer_set_cursor(struct wl_client *client, struct wl_resource *resource,
 	if (pointer->focus_serial - serial > UINT32_MAX / 2)
 		return;
 
-	if (surface && pointer->sprite && surface != pointer->sprite->surface) {
-		if (surface->configure) {
-			wl_resource_post_error(surface->resource,
-					       WL_DISPLAY_ERROR_INVALID_OBJECT,
-					       "surface->configure already "
-					       "set");
+	if (surface) {
+		if (weston_surface_set_role(surface, "wl_pointer-cursor",
+					    resource,
+					    WL_POINTER_ERROR_ROLE) < 0)
 			return;
-		}
 	}
 
 	if (pointer->sprite)

xwayland/window-manager.c

@@ -2303,6 +2303,13 @@ xserver_map_shell_surface(struct weston_wm_window *window,
 	if (!shell_interface->get_primary_view)
 		return;
 
+	if (window->surface->configure) {
+		weston_log("warning, unexpected in %s: "
+			   "surface's configure hook is already set.\n",
+			   __func__);
+		return;
+	}
+
 	window->shsurf = 
 		shell_interface->create_shell_surface(shell_interface->shell,
 						      window->surface,