render: impl Node for RenderGraph in prep for sub-graphs

lyra-game/src/render/graph/mod.rs

@@ -242,9 +242,9 @@ impl RenderGraph {
                             .as_compute_pipeline_descriptor()
                             .expect("got render pipeline descriptor in a compute pass"),
                     )),
-                    NodeType::Presenter | NodeType::Node => {
+                    NodeType::Presenter | NodeType::Node | NodeType::Graph => {
                         panic!("Present or Node RenderGraph passes should not have a pipeline descriptor!");
-                    }
+                    },
                 };
 
                 drop(desc);
@@ -466,3 +466,23 @@ impl RenderGraph {
         }
     }
 }
+
+impl Node for RenderGraph {
+    fn desc<'a, 'b>(&'a mut self, graph: &'b mut RenderGraph) -> NodeDesc {
+        // TODO: how would bind groups be shared between sub-graphs?
+        NodeDesc::new(NodeType::Graph, None, vec![])
+    }
+
+    fn prepare(&mut self, world: &mut World, _: &mut RenderGraphContext) {
+        self.prepare(world);
+    }
+
+    fn execute(
+        &mut self,
+        _: &mut RenderGraph,
+        _: &NodeDesc,
+        _: &mut RenderGraphContext,
+    ) {
+        self.render();
+    }
+}

lyra-game/src/render/graph/node.rs

@@ -18,6 +18,8 @@ pub enum NodeType {
     Render,
     /// A node that presents render results to a render target.
     Presenter,
+    /// A node that represents a sub-graph.
+    Graph,
 }
 
 impl NodeType {
@@ -28,6 +30,7 @@ impl NodeType {
             NodeType::Compute => true,
             NodeType::Render => true,
             NodeType::Presenter => false,
+            NodeType::Graph => false,
         }
     }
 }