diff -r 7d4e31d295af -r c4dae6fe6d5b src/cx/tree.h
--- a/src/cx/tree.h	Sat Feb 17 20:51:27 2024 +0100
+++ b/src/cx/tree.h	Sun Feb 18 12:24:04 2024 +0100
@@ -46,14 +46,23 @@
 
 /**
  * When entering a node.
+ *
+ * When this is the first sibling, source is the parent, otherwise it is the previous child.
  */
 #define CX_TREE_ITERATOR_ENTER      0x1
 /**
  * When advancing to the next child.
+ *
+ * The visited node is the next child and the source is the previous child.
+ * This pass is triggered after exiting the previous child and before entering the next child.
  */
 #define CX_TREE_ITERATOR_NEXT_CHILD 0x2
 /**
  * When exiting the node.
+ *
+ * The visited node is the node being exited and source is the previously entered node
+ * (usually the last child of the exited node, unless it has no children, in which case it is the node itself).
+ * When advancing to the next child in a list of siblings, the previous child is exited, first.
  */
 #define CX_TREE_ITERATOR_EXIT       0x4
 
@@ -278,8 +287,8 @@
  * @see cxTreeIteratorDispose()
  */
 __attribute__((__nonnull__))
-CxTreeIterator cx_tree_iterate(
-        void const *root,
+CxTreeIterator cx_tree_iterator(
+        void *root,
         int passes,
         ptrdiff_t loc_children,
         ptrdiff_t loc_next