Add some docs that explicitly mentions how we handle cycles in the tree

This was reported for QGraphicsAnchorLayout, but affects all
QGraphicsLayout subclasses. However, since it is not even handled
properly in QGraphicsItem::setParentItem() it should be fine that we
don't try to deal with this issue. Thus, the layouts are "consistent"
with graphics items when it comes to detection of cycles in the tree.

2 files changed, 5 insertions, 0 deletions

diff --git a/src/gui/graphicsview/qgraphicsanchorlayout.cpp b/src/gui/graphicsview/qgraphicsanchorlayout.cpp
index c39e8a6..cb8ccc1 100644
--- a/src/gui/graphicsview/qgraphicsanchorlayout.cpp
+++ b/src/gui/graphicsview/qgraphicsanchorlayout.cpp
@@ -215,6 +215,9 @@ QGraphicsAnchorLayout::~QGraphicsAnchorLayout()
 
     The spacing can also be set manually by using QGraphicsAnchor::setSpacing() method.
 
+    Calling this function where \a firstItem or \a secondItem are ancestors of the layout have
+    undefined behaviour.
+
     \sa addCornerAnchors(), addAnchors()
  */
 QGraphicsAnchor *
diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index 45627f6..1ebee45 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -1511,6 +1511,8 @@ const QGraphicsObject *QGraphicsItem::toGraphicsObject() const
     the parent. You should not \l{QGraphicsScene::addItem()}{add} the
     item to the scene yourself.
 
+    Calling this function on an item that is an ancestor of \a parent have undefined behaviour.
+
     \sa parentItem(), childItems()
 */
 void QGraphicsItem::setParentItem(QGraphicsItem *parent)