Geometry Nodes: simplify looping over attributes in geometry set

This adds three new methods:
* `InstancesComponent::foreach_reference_as_geometry(...)`
* `GeometrySet::attribute_foreach(...)`
* `GeometrySet::gather_attributes_for_propagation(...)`

The goal is that these iteration primitives can be used in places
where we use more specialized iterators currently.

Differential Revision: https://developer.blender.org/D12613

1 files changed, 19 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_geometry_set.hh b/source/blender/blenkernel/BKE_geometry_set.hh
index 317d513dae6..a6c77c74b9e 100644
--- a/source/blender/blenkernel/BKE_geometry_set.hh
+++ b/source/blender/blenkernel/BKE_geometry_set.hh
@@ -25,6 +25,7 @@
 
 #include "BLI_float3.hh"
 #include "BLI_float4x4.hh"
+#include "BLI_function_ref.hh"
 #include "BLI_hash.hh"
 #include "BLI_map.hh"
 #include "BLI_set.hh"
@@ -293,6 +294,21 @@ struct GeometrySet {
   bool owns_direct_data() const;
   void ensure_owns_direct_data();
 
+  using AttributeForeachCallback =
+      blender::FunctionRef<void(const blender::bke::AttributeIDRef &attribute_id,
+                                const AttributeMetaData &meta_data,
+                                const GeometryComponent &component)>;
+
+  void attribute_foreach(blender::Span<GeometryComponentType> component_types,
+                         bool include_instances,
+                         AttributeForeachCallback callback) const;
+
+  void gather_attributes_for_propagation(
+      blender::Span<GeometryComponentType> component_types,
+      GeometryComponentType dst_component_type,
+      bool include_instances,
+      blender::Map<blender::bke::AttributeIDRef, AttributeKind> &r_attributes) const;
+
   /* Utility methods for creation. */
   static GeometrySet create_with_mesh(
       Mesh *mesh, GeometryOwnershipType ownership = GeometryOwnershipType::Owned);
@@ -597,6 +613,9 @@ class InstancesComponent : public GeometryComponent {
 
   int attribute_domain_size(const AttributeDomain domain) const final;
 
+  void foreach_referenced_geometry(
+      blender::FunctionRef<void(const GeometrySet &geometry_set)> callback) const;
+
   bool is_empty() const final;
 
   bool owns_direct_data() const override;