Nodes: add separately allocated run-time data for bNodeTree

`bNodeTree` has a lot of run-time embedded in it currently. Having a separately
allocated run-time struct has some benefits:
* Run-time data is not stored in files.
* Makes it easy to use c++ types as run-time data.
* More clear distinction between what data only exists at run-time and which doesn't.

This commit doesn't move all run-time data to the new struct yet, only the data where
I know for sure how it is used. The remaining data can be moved separately.

Differential Revision: https://developer.blender.org/D15033

1 files changed, 40 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_node_runtime.hh b/source/blender/blenkernel/BKE_node_runtime.hh
new file mode 100644
index 00000000000..c9c4577a2d4
--- /dev/null
+++ b/source/blender/blenkernel/BKE_node_runtime.hh
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+#include <memory>
+
+#include "BLI_sys_types.h"
+#include "BLI_utility_mixins.hh"
+
+namespace blender::nodes {
+struct FieldInferencingInterface;
+}
+
+namespace blender::bke {
+
+class bNodeTreeRuntime : NonCopyable, NonMovable {
+ public:
+  /**
+   * Keeps track of what changed in the node tree until the next update.
+   * Should not be changed directly, instead use the functions in `BKE_node_tree_update.h`.
+   * #eNodeTreeChangedFlag.
+   */
+  uint32_t changed_flag = 0;
+  /**
+   * A hash of the topology of the node tree leading up to the outputs. This is used to determine
+   * of the node tree changed in a way that requires updating geometry nodes or shaders.
+   */
+  uint32_t output_topology_hash = 0;
+
+  /**
+   * Used to cache run-time information of the node tree.
+   * #eNodeTreeRuntimeFlag.
+   */
+  uint8_t runtime_flag = 0;
+
+  /** Information about how inputs and outputs of the node group interact with fields. */
+  std::unique_ptr<nodes::FieldInferencingInterface> field_inferencing_interface;
+};
+
+}  // namespace blender::bke