From 90772fbdbb6a19d33b0487db8c4dbffdbd3ba3cf Mon Sep 17 00:00:00 2001
From: Daniel Hammerschmid <daniel.hammerschmid@documatrix.com>
Date: Thu, 12 Mar 2026 15:00:54 +0100
Subject: [PATCH] HPDF_StructureElement_AddChild may now move an element from
 one parent to another

---
 include/hpdf_error.h             |  1 -
 include/hpdf_objects.h           |  5 +++++
 include/hpdf_structure_element.h |  4 ++++
 src/hpdf_array.c                 | 28 ++++++++++++++++++++++++++++
 src/hpdf_structure_element.c     | 25 +++++++++++++++++++++----
 5 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/include/hpdf_error.h b/include/hpdf_error.h
index 7a86b0cd..0ecc14ff 100644
--- a/include/hpdf_error.h
+++ b/include/hpdf_error.h
@@ -146,7 +146,6 @@ extern "C" {
 #define HPDF_NAME_CANNOT_GET_NAMES                0x1084
 #define HPDF_INVALID_ICC_COMPONENT_NUM            0x1085
 #define HPDF_PAGE_INVALID_OPERATOR_STACK          0x1086
-#define HPDF_STRUCTURE_ELEMENT_CANNOT_SET_PARENT  0x1087
 
 /*---------------------------------------------------------------------------*/
 
diff --git a/include/hpdf_objects.h b/include/hpdf_objects.h
index 028d9794..8d7cafc5 100644
--- a/include/hpdf_objects.h
+++ b/include/hpdf_objects.h
@@ -365,6 +365,11 @@ HPDF_Array_Add  (HPDF_Array  array,
                  void        *obj);
 
 
+HPDF_STATUS
+HPDF_Array_Remove  (HPDF_Array  array,
+                    void        *obj);
+
+
 HPDF_STATUS
 HPDF_Array_Insert  (HPDF_Array  array,
                     void        *target,
diff --git a/include/hpdf_structure_element.h b/include/hpdf_structure_element.h
index f8c6a701..e9976d9c 100644
--- a/include/hpdf_structure_element.h
+++ b/include/hpdf_structure_element.h
@@ -43,6 +43,10 @@ HPDF_STATUS
 HPDF_StructureElement_AddChild  (HPDF_StructureElement parent,
                                  HPDF_StructureElement child);
 
+HPDF_STATUS
+HPDF_StructureElement_RemoveChild  (HPDF_StructureElement parent,
+                                    HPDF_StructureElement child);
+
 HPDF_STATUS
 HPDF_StructureElement_AddMarkedContentSequence  (HPDF_StructureElement structure_element,
                                                  HPDF_UINT             mcid,
diff --git a/src/hpdf_array.c b/src/hpdf_array.c
index 14715eae..9f85fa1f 100644
--- a/src/hpdf_array.c
+++ b/src/hpdf_array.c
@@ -225,6 +225,34 @@ HPDF_Array_Add  (HPDF_Array  array,
     return ret;
 }
 
+HPDF_STATUS
+HPDF_Array_Remove  (HPDF_Array  array,
+                    void        *target)
+{
+    HPDF_UINT i;
+
+    for (i = 0; i < array->list->count; i++) {
+        void *ptr = HPDF_List_ItemAt (array->list, i);
+        void *obj_ptr;
+
+        HPDF_Obj_Header *header = (HPDF_Obj_Header *)ptr;
+        if (header->obj_class == HPDF_OCLASS_PROXY)
+            obj_ptr = ((HPDF_Proxy)ptr)->obj;
+        else
+            obj_ptr = ptr;
+
+        if (obj_ptr == target) {
+            HPDF_List_RemoveByIndex (array->list, i);
+
+            if (header->obj_class == HPDF_OCLASS_PROXY)
+                HPDF_Obj_Free (array->mmgr, ptr);
+
+            return HPDF_OK;
+        }
+    }
+
+    return HPDF_ITEM_NOT_FOUND;
+}
 
 HPDF_UINT
 HPDF_Array_Items  (HPDF_Array array)
diff --git a/src/hpdf_structure_element.c b/src/hpdf_structure_element.c
index f2de847b..9e772e90 100644
--- a/src/hpdf_structure_element.c
+++ b/src/hpdf_structure_element.c
@@ -264,8 +264,11 @@ HPDF_StructureElement_AddChild  (HPDF_StructureElement parent,
 
     HPDF_PTRACE((" HPDF_StructureElement_AddChild\n"));
 
-    if (HPDF_Dict_GetItem (child, "P", HPDF_OCLASS_DICT))
-        return HPDF_SetError (parent->error, HPDF_STRUCTURE_ELEMENT_CANNOT_SET_PARENT, 0);
+    if (HPDF_Dict_GetItem (child, "P", HPDF_OCLASS_DICT)) {
+        HPDF_StructureElement old_parent = (HPDF_StructureElement)HPDF_Dict_GetItem (child, "P", HPDF_OCLASS_DICT);
+        if ((ret = HPDF_StructureElement_RemoveChild (old_parent, child)) != HPDF_OK)
+            return ret;
+    }
 
     if ((ret = HPDF_Dict_Add (child, "P", parent)) != HPDF_OK)
         return ret;
@@ -283,6 +286,20 @@ HPDF_StructureElement_AddChild  (HPDF_StructureElement parent,
     return HPDF_Array_Add (children, child);
 }
 
+HPDF_STATUS
+HPDF_StructureElement_RemoveChild  (HPDF_StructureElement parent,
+                                    HPDF_StructureElement child)
+{
+    HPDF_PTRACE((" HPDF_StructureElement_RemoveChild\n"));
+
+    HPDF_Array children = (HPDF_Array)HPDF_Dict_GetItem (parent, "K", HPDF_OCLASS_ARRAY);
+    if (!children) {
+        return HPDF_OK;
+    }
+
+    return HPDF_Array_Remove (children, child);
+}
+
 HPDF_STATUS
 HPDF_StructureElement_AddMarkedContentSequence  (HPDF_StructureElement structure_element,
                                                  HPDF_UINT             mcid,
@@ -292,7 +309,7 @@ HPDF_StructureElement_AddMarkedContentSequence  (HPDF_StructureElement structure
     HPDF_Dict pg;
     HPDF_STATUS ret;
 
-    HPDF_PTRACE((" HPDF_StructureElement_AddChild\n"));
+    HPDF_PTRACE((" HPDF_StructureElement_AddMarkedContentSequence\n"));
 
     pg = (HPDF_Dict)HPDF_Dict_GetItem (structure_element, "Pg", HPDF_OCLASS_DICT);
     if (!pg) {
@@ -343,7 +360,7 @@ HPDF_StructureElement_AddObjectReference (HPDF_StructureElement structure_elemen
     HPDF_Array children;
     HPDF_STATUS ret;
 
-    HPDF_PTRACE((" HPDF_StructureElement_SetObjectReference\n"));
+    HPDF_PTRACE((" HPDF_StructureElement_AddObjectReference\n"));
 
     HPDF_Dict objr = HPDF_Dict_New (structure_element->mmgr);
     if (!objr)