Nodes: cache node declaration on node

Previously, it was necessary to rebuild the node declaration
every time it was used. Now it is cached per node for easy
and fast access.

For more details on what this is, look at the comment in
`DNA_node_types.h`.

Differential Revision: https://developer.blender.org/D12471

1 files changed, 30 insertions, 0 deletions

diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index 82eabf6995c..c4cbc71762c 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -216,6 +216,16 @@ typedef enum eNodeSocketFlag {
   SOCK_HIDE_LABEL = (1 << 12),
 } eNodeSocketFlag;
 
+/** Workaround to forward-declare C++ type in C header. */
+#ifdef __cplusplus
+namespace blender::nodes {
+class NodeDeclaration;
+}
+using NodeDeclarationHandle = blender::nodes::NodeDeclaration;
+#else
+typedef struct NodeDeclarationHandle NodeDeclarationHandle;
+#endif
+
 /* TODO: Limit data in bNode to what we want to see saved. */
 typedef struct bNode {
   struct bNode *next, *prev, *new_node;
@@ -315,6 +325,26 @@ typedef struct bNode {
    * needs to be a float to feed GPU_uniform.
    */
   float sss_id;
+
+  /**
+   * Describes the desired interface of the node. This is run-time data only.
+   * The actual interface of the node may deviate from the declaration temporarily.
+   * It's possible to sync the actual state of the node to the desired state. Currently, this is
+   * only done when a node is created or loaded.
+   *
+   * In the future, we may want to keep more data only in the declaration, so that it does not have
+   * to be synced to other places that are stored in files. That especially applies to data that
+   * can't be edited by users directly (e.g. min/max values of sockets, tooltips, ...).
+   *
+   * The declaration of a node can be recreated at any time when it is used. Caching it here is
+   * just a bit more efficient when it is used a lot. To make sure that the cache is up-to-date,
+   * call #nodeDeclarationEnsure before using it.
+   *
+   * Currently, the declaration is the same for every node of the same type. Going forward, that is
+   * intended to change though. Especially when nodes become more dynamic with respect to how many
+   * sockets they have.
+   */
+  NodeDeclarationHandle *declaration;
 } bNode;
 
 /* node->flag */