Geometry Nodes: add support for eye dropper for object input in modifier

Differential Revision: https://developer.blender.org/D17108

source/blender/makesdna/DNA_ID.h

@@ -104,6 +104,12 @@ typedef struct IDPropertyUIDataString {
 /** For #IDP_UI_DATA_TYPE_ID. */
 typedef struct IDPropertyUIDataID {
   IDPropertyUIData base;
+  /**
+   * #ID_Type. This type type is not enforced. It is just a hint to the ui for what kind of ID is
+   * expected. If this is zero, any id type is expected.
+   */
+  short id_type;
+  char _pad[6];
 } IDPropertyUIDataID;
 
 typedef struct IDPropertyData {

source/blender/makesrna/intern/rna_access.c

@@ -1415,6 +1415,16 @@ int RNA_property_string_maxlength(PropertyRNA *prop)
 
 StructRNA *RNA_property_pointer_type(PointerRNA *ptr, PropertyRNA *prop)
 {
+  if (prop->magic != RNA_MAGIC) {
+    const IDProperty *idprop = (IDProperty *)prop;
+    if (idprop->type == IDP_ID) {
+      const IDPropertyUIDataID *ui_data = (const IDPropertyUIDataID *)idprop->ui_data;
+      if (ui_data) {
+        return ID_code_to_RNA_type(ui_data->id_type);
+      }
+    }
+  }
+
   prop = rna_ensure_property(prop);
 
   if (prop->type == PROP_POINTER) {

source/blender/modifiers/intern/MOD_nodes.cc

@@ -513,7 +513,10 @@ id_property_create_from_socket(const bNodeSocket &socket)
     case SOCK_OBJECT: {
       const bNodeSocketValueObject *value = static_cast<const bNodeSocketValueObject *>(
           socket.default_value);
-      return bke::idprop::create(socket.identifier, reinterpret_cast<ID *>(value->value));
+      auto property = bke::idprop::create(socket.identifier, reinterpret_cast<ID *>(value->value));
+      IDPropertyUIDataID *ui_data = (IDPropertyUIDataID *)IDP_ui_data_ensure(property.get());
+      ui_data->id_type = ID_OB;
+      return property;
     }
     case SOCK_COLLECTION: {
       const bNodeSocketValueCollection *value = static_cast<const bNodeSocketValueCollection *>(