1 files changed, 98 insertions, 0 deletions
diff --git a/source/blender/functions/FN_lazy_function_graph_executor.hh b/source/blender/functions/FN_lazy_function_graph_executor.hh
new file mode 100644
index 00000000000..a6ae5cac967
--- /dev/null
+++ b/source/blender/functions/FN_lazy_function_graph_executor.hh
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+/** \file
+ * \ingroup fn
+ *
+ * This file provides means to create a #LazyFunction from #Graph (which could then e.g. be used in
+ * another #Graph again).
+ */
+
+#include "BLI_vector.hh"
+#include "BLI_vector_set.hh"
+
+#include "FN_lazy_function_graph.hh"
+
+namespace blender::fn::lazy_function {
+
+/**
+ * Can be implemented to log values produced during graph evaluation.
+ */
+class GraphExecutorLogger {
+ public:
+  virtual ~GraphExecutorLogger() = default;
+
+  virtual void log_socket_value(const Socket &socket,
+                                GPointer value,
+                                const Context &context) const;
+
+  virtual void log_before_node_execute(const FunctionNode &node,
+                                       const Params &params,
+                                       const Context &context) const;
+
+  virtual void log_after_node_execute(const FunctionNode &node,
+                                      const Params &params,
+                                      const Context &context) const;
+
+  virtual void dump_when_outputs_are_missing(const FunctionNode &node,
+                                             Span<const OutputSocket *> missing_sockets,
+                                             const Context &context) const;
+  virtual void dump_when_input_is_set_twice(const InputSocket &target_socket,
+                                            const OutputSocket &from_socket,
+                                            const Context &context) const;
+};
+
+/**
+ * Has to be implemented when some of the nodes in the graph may have side effects. The
+ * #GraphExecutor has to know about that to make sure that these nodes will be executed even though
+ * their outputs are not needed.
+ */
+class GraphExecutorSideEffectProvider {
+ public:
+  virtual ~GraphExecutorSideEffectProvider() = default;
+  virtual Vector<const FunctionNode *> get_nodes_with_side_effects(const Context &context) const;
+};
+
+class GraphExecutor : public LazyFunction {
+ public:
+  using Logger = GraphExecutorLogger;
+  using SideEffectProvider = GraphExecutorSideEffectProvider;
+
+ private:
+  /**
+   * The graph that is evaluated.
+   */
+  const Graph &graph_;
+  /**
+   * Input and output sockets of the entire graph.
+   */
+  VectorSet<const OutputSocket *> graph_inputs_;
+  VectorSet<const InputSocket *> graph_outputs_;
+  /**
+   * Optional logger for events that happen during execution.
+   */
+  const Logger *logger_;
+  /**
+   * Optional side effect provider. It knows which nodes have side effects based on the context
+   * during evaluation.
+   */
+  const SideEffectProvider *side_effect_provider_;
+
+  friend class Executor;
+
+ public:
+  GraphExecutor(const Graph &graph,
+                Span<const OutputSocket *> graph_inputs,
+                Span<const InputSocket *> graph_outputs,
+                const Logger *logger,
+                const SideEffectProvider *side_effect_provider);
+
+  void *init_storage(LinearAllocator<> &allocator) const override;
+  void destruct_storage(void *storage) const override;
+
+ private:
+  void execute_impl(Params &params, const Context &context) const override;
+};
+
+}  // namespace blender::fn::lazy_function