Node panels: New DNA and C++ API for node group interfaces.

Part 1/3 of #109135, #110272

Adds a new DNA structure for defining node group interfaces without
using `bNodeSocket` and with additional node UI item types.

Node group interfaces are organized as a hierarchy of "items", which
can be sockets or panels. Panels can contain both sockets and other
panels (although nested panels beyond the root panel may be disabled to
avoid complexity on the user level).

Sockets can be added to the interface in any order, not just the
conventional outputs..inputs order. Sockets can be marked as both input
and output, generating 2 sockets on node instances.

The C++ API in the DNA struct allows manipulating the interface
declaration by adding and removing items, moving them inside the
interface or into a different panel.

@@ -0,0 +32,4 @@
+
+}  // namespace blender::bke
+
+inline bNodeTreeInterfaceItem *bNodeTreeInterface::active_item()

@@ -0,0 +83,4 @@
+  bool match = false;
+  switch (item.item_type) {
+    case NODE_INTERFACE_SOCKET: {
+      match |= std::is_same<T, bNodeTreeInterfaceSocket>::value;

@@ -0,0 +273,4 @@
+
+#endif
+
+#ifdef __cplusplus

@@ -0,0 +52,4 @@
+/** \name ID user increment in socket data
+ * \{ */
+
+[[maybe_unused]] static void socket_data_id_user_increment(bNodeSocketValueObject &data)

@@ -0,0 +508,4 @@
+      BLI_assert(src_socket.socket_type != nullptr);
+
+      dst_socket.name = BLI_strdup(src_socket.name);
+      dst_socket.description = src_socket.description ? BLI_strdup(src_socket.description) :

@@ -0,0 +1016,4 @@
+  if (include_self && fn(this->item) == false) {
+    return;
+  }
+  stack.push(items());

@@ -0,0 +1099,4 @@
+  new_socket->uid = uid;
+  new_socket->item.item_type = NODE_INTERFACE_SOCKET;
+  new_socket->name = BLI_strdup(name.data());
+  new_socket->description = description.data() ? BLI_strdup(description.data()) : nullptr;

@@ -0,0 +35,4 @@
+struct uiLayout;
+
+/** Type of interface item. */
+typedef enum eNodeTreeInterfaceItemType {

@@ -0,0 +70,4 @@
+  char *default_attribute_name;
+
+  /* Unique id for constructing socket identifiers. */
+  int uid;

@@ -0,0 +72,4 @@
+  /* Unique id for constructing socket identifiers. */
+  int uid;
+  char _pad[4];
+  /* String identifier for backwards compatibility, not used for new sockets. */

@@ -0,0 +73,4 @@
+  int uid;
+  char _pad[4];
+  /* String identifier for backwards compatibility, not used for new sockets. */
+  char *uid_compat;

@@ -0,0 +75,4 @@
+  /* String identifier for backwards compatibility, not used for new sockets. */
+  char *uid_compat;
+
+  void *socket_data;

@@ -0,0 +77,4 @@
+
+  void *socket_data;
+
+  IDProperty *prop;

@@ -0,0 +84,4 @@
+  bNodeSocketType *socket_typeinfo() const;
+  blender::ColorGeometry4f socket_color() const;
+
+  bool set_socket_type(const char *new_socket_type);

@@ -0,0 +86,4 @@
+
+  bool set_socket_type(const char *new_socket_type);
+
+  void init_from_socket_instance(const bNodeSocket *socket);

@@ -0,0 +93,4 @@
+typedef struct bNodeTreeInterfacePanel {
+  bNodeTreeInterfaceItem item;
+
+  char *name;

@@ -0,0 +115,4 @@
+  /**
+   * Check if the item is a direct child of the panel.
+   */
+  bool contains_item(const bNodeTreeInterfaceItem &item) const;

@@ -0,0 +121,4 @@
+   * Search for an item in the interface.
+   * \return True if the item was found.
+   */
+  bool find_item(const bNodeTreeInterfaceItem &item) const;

@@ -0,0 +136,4 @@
+   * \param r_parent: Parent containing the item.
+   * \return True if the item was found in any panel.
+   */
+  bool find_item_parent(const bNodeTreeInterfaceItem &item, bNodeTreeInterfacePanel *&r_parent);

@@ -0,0 +138,4 @@
+   */
+  bool find_item_parent(const bNodeTreeInterfaceItem &item, bNodeTreeInterfacePanel *&r_parent);
+
+  void copy_items(blender::Span<const bNodeTreeInterfaceItem *> items_src, int flag);

@@ -0,0 +141,4 @@
+  void copy_items(blender::Span<const bNodeTreeInterfaceItem *> items_src, int flag);
+  void clear_items(bool do_id_user);
+
+  void add_item(bNodeTreeInterfaceItem &item);

@@ -0,0 +151,4 @@
+   * \note: The items are visited in drawing order from top to bottom.
+   *
+   * \param fn: Function to execute for each item, iterations stops if false is returned.
+   * \param include_root: Include the panel itself in the iteration.

@@ -0,0 +156,4 @@
+  void foreach_item(blender::FunctionRef<bool(bNodeTreeInterfaceItem &item)> fn,
+                    bool include_self = false);
+  /**
+   * Apply a function to every item in the panel, including child panels.

@@ -0,0 +170,4 @@
+typedef struct bNodeTreeInterface {
+  bNodeTreeInterfacePanel root_panel;
+
+  int active_index;

@@ -0,0 +174,4 @@
+  int next_uid;
+
+#ifdef __cplusplus
+  void copy_data(const bNodeTreeInterface &src, int flag);

@@ -0,0 +175,4 @@
+
+#ifdef __cplusplus
+  void copy_data(const bNodeTreeInterface &src, int flag);
+  void free_data();

@@ -0,0 +697,4 @@
+  return nodeSocketTypeFind(socket_type);
+}
+
+blender::ColorGeometry4f bNodeTreeInterfaceSocket::socket_color() const

@@ -0,0 +9,4 @@
+
+#include "BKE_node.h"
+
+#ifdef __cplusplus

@@ -0,0 +22,4 @@
+namespace blender::bke {
+
+/* Runtime topology cache for linear access to items. */
+typedef struct bNodeTreeInterfaceCache {

@@ -0,0 +183,4 @@
+}
+
+}  // namespace blender::bke::node_interface
+

@@ -0,0 +40,4 @@
+    return nullptr;
+  }
+  /* For builtin socket types only the base type is supported. */
+  if (blender::bke::nodeIsStaticSocketType(typeinfo)) {

@@ -0,0 +43,4 @@
+  if (blender::bke::nodeIsStaticSocketType(typeinfo)) {
+    return nodeStaticSocketType(typeinfo->type, PROP_NONE);
+  }
+  else {

@@ -0,0 +127,4 @@
+{
+  data.value = false;
+}
+template<> void socket_data_init_impl(bNodeSocketValueRotation & /*data*/) {}

@@ -0,0 +330,4 @@
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Read ID pointer data

@@ -0,0 +810,4 @@
+  bool found = false;
+  /* Have to capture item address here instead of just a reference,
+   * otherwise pointer comparison will not work. */
+  this->foreach_item([&item, &index, &found](const bNodeTreeInterfaceItem &titem) {