API for manipulating items in the simulation zone output node.

This involves a bad level call, but since another editor function
is already used this way it doesn't make things worse.

@@ -572,6 +572,15 @@ class NodeTreeMainUpdater {
         return true;
       }
     }
+    /* Check paired simulation zone nodes. */

@@ -39,6 +39,13 @@ using namespace blender;
 using blender::fn::ValueOrField;
 using blender::nodes::SocketDeclarationPtr;
 
+extern "C" void ED_node_type_draw_color(const char *idname, float *r_color);

@@ -55,2 +59,2 @@
-    if (STREQ(item.name, name)) {
-      return true;
+  for (const NodeSimulationItem &item : Span(args.sim->items, args.sim->items_num)) {
+    if (&item != args.item) {

@@ -27,3 +27,2 @@
           std::unique_ptr<decl::Geometry> decl = std::make_unique<decl::Geometry>();
-          decl->name = item.name;
-          decl->identifier = item.name;
+          decl->name = item.name ? item.name : "";

@@ -195,0 +224,4 @@
+    bl_label = "Add State Item"
+    bl_options = {'REGISTER', 'UNDO'}
+
+    default_socket_type = 'GEOMETRY'

@@ -195,0 +258,4 @@
+
+
+class NODE_OT_simulation_zone_item_move(SimulationZoneOperator, Operator):
+    '''Move a simulation state item up or down in list'''

@@ -28,2 +30,2 @@
-          decl->name = item.name;
-          decl->identifier = item.name;
+          decl->name = item.name ? item.name : "";
+          decl->identifier = buf;

@@ -55,2 +61,2 @@
-    if (STREQ(item.name, name)) {
-      return true;
+  for (const NodeSimulationItem &item : Span(args.sim->items, args.sim->items_num)) {
+    if (&item != args.item) {

@@ -336,2 +322,4 @@
   nodeRegisterType(&ntype);
 }
+
+bNode *NOD_geometry_simulation_output_find_node_by_data(bNodeTree *ntree,

@@ -338,0 +336,4 @@
+bNode *NOD_geometry_simulation_output_find_node_by_item(bNodeTree *ntree,
+                                                        const NodeSimulationItem *item)
+{
+  for (bNode *node : ntree->nodes_by_type("GeometryNodeSimulationOutput")) {

@@ -338,0 +367,4 @@
+bool NOD_geometry_simulation_output_contains_item(NodeGeometrySimulationOutput *sim,
+                                                  const NodeSimulationItem *item)
+{
+  const int index = item - sim->items;

@@ -338,0 +374,4 @@
+NodeSimulationItem *NOD_geometry_simulation_output_get_active_item(
+    NodeGeometrySimulationOutput *sim)
+{
+  if (sim->active_index >= 0 && sim->active_index < sim->items_num) {

@@ -338,0 +392,4 @@
+NodeSimulationItem *NOD_geometry_simulation_output_find_item(NodeGeometrySimulationOutput *sim,
+                                                             const char *name)
+{
+  for (const int i : blender::IndexRange(sim->items_num)) {

@@ -338,0 +414,4 @@
+{
+  NodeSimulationItem *old_items = sim->items;
+  sim->items = MEM_cnew_array<NodeSimulationItem>(sim->items_num + 1, __func__);
+  for (const int i : blender::IndexRange(0, index)) {

@@ -192,6 +193,97 @@ class NODE_OT_add_simulation_zone(NodeAddOperator, Operator):
         return {'FINISHED'}
 
 
+class SimulationZoneOperator():

@@ -195,0 +208,4 @@
+    @classmethod
+    def poll(cls, context):
+        space = context.space_data
+        # needs active node editor and a tree to add nodes to

@@ -195,0 +233,4 @@
+
+        # Remember index to move the item
+        dst_index = min(node.active_index + 1, len(state_items))
+        # Empty name so it is based on the type only

@@ -9790,0 +9973,4 @@
+  RNA_def_struct_ui_text(srna, "State Items", "Collection of simulation state items");
+
+  func = RNA_def_function(srna, "new", "rna_NodeGeometrySimulationOutput_items_new");
+  RNA_def_function_ui_description(func, "Add a state item to this simulation zone");

@@ -26,0 +36,4 @@
+bool NOD_geometry_simulation_output_item_socket_type_supported(eNodeSocketDatatype socket_type);
+
+/** Set a unique item name.
+ * @return True if the unique name differs from the original name.

@@ -338,0 +324,4 @@
+  return blender::Span<NodeSimulationItem>(items, items_num);
+}
+
+blender::MutableSpan<NodeSimulationItem> NodeGeometrySimulationOutput::items_mutable_span()

@@ -338,0 +501,4 @@
+  if (from_index == to_index) {
+    return;
+  }
+  else if (from_index < to_index) {