[server] Add quint32 Resource::id() const

Wrapper for wl_resource_get_id.

src/wayland/server/resource.cpp

@@ -100,5 +100,13 @@ wl_resource *Resource::parentResource() const
     return d->parentResource;
 }
 
+quint32 Resource::id() const
+{
+    if (!d->resource) {
+        return 0;
+    }
+    return wl_resource_get_id(d->resource);
+}
+
 }
 }

src/wayland/server/resource.h

@@ -46,6 +46,13 @@ public:
     ClientConnection *client();
     Global *global();
     wl_resource *parentResource() const;
+    /**
+     * @returns The id of this Resource if it is created, otherwise @c 0.
+     *
+     * This is a convenient wrapper for wl_resource_get_id.
+     * @since 5.3
+     **/
+    quint32 id() const;
 
 protected:
     class Private;