Fix background extensions

Thanks @Cloudef, it works great

include/extensions.h

@@ -2,10 +2,11 @@
 #define _SWAY_EXTENSIONS_H
 
 #include "list.h"
+#include "wlc/wlc-wayland.h"
 
 struct background_config {
         wlc_handle output;
-        wlc_handle surface;
+        wlc_resource surface;
 };
 
 struct desktop_shell_state {

sway/extensions.c

@@ -7,16 +7,15 @@
 struct desktop_shell_state desktop_shell;
 
 static void set_background(struct wl_client *client, struct wl_resource *resource,
-		struct wl_resource *_output, struct wl_resource *_surface) {
+		struct wl_resource *_output, struct wl_resource *surface) {
 	wlc_handle output = wlc_handle_from_wl_output_resource(_output);
-	wlc_handle surface = wlc_handle_from_wl_surface_resource(_surface);
+	if (!output) {
-	sway_log(L_DEBUG, "Setting surface %d as background for output %d", (int)surface, (int)output);
-	if (!output || !surface) {
 		return;
 	}
+	sway_log(L_DEBUG, "Setting surface %p as background for output %d", surface, (int)output);
 	struct background_config *config = malloc(sizeof(struct background_config));
 	config->output = output;
-	config->surface = surface;
+	config->surface = wlc_resource_from_wl_surface_resource(surface);
 	list_add(desktop_shell.backgrounds, config);
 }
 

sway/handlers.c

@@ -70,7 +70,6 @@ static void handle_output_pre_render(wlc_handle output) {
 	for (i = 0; i < desktop_shell.backgrounds->length; ++i) {
 		struct background_config *config = desktop_shell.backgrounds->items[i];
 		if (config->output == output) {
-			sway_log(L_DEBUG, "Rendering background surface %d", (int)config->surface);
 			wlc_surface_render(config->surface, &(struct wlc_geometry){ wlc_origin_zero, *wlc_output_get_resolution(output) });
 			break;
 		}