more safety, allowing anyone delete a layout or call setParent and have the Right Things(tm) happen without anyone's toes getting blown off in the process.

svn path=/trunk/KDE/kdebase/workspace/libs/plasma/; revision=771851

layouts/layout.cpp

@@ -68,17 +68,24 @@ Layout::Layout(LayoutItem *parent)
     : LayoutItem(),
       d(new Private(parent))
 {
-    if (parent) {
+    setParent(parent);
+}
+
+void Layout::setParent(LayoutItem *parent)
+{
+    d->parent = parent;
+
+    if (parent && parent->layout() != this) {
         parent->setLayout(this);
     }
 }
 
-void Layout::setParent(LayoutItem *parent) {
-    d->parent = parent;
-}
-
 Layout::~Layout()
 {
+    if (d->parent) {
+        d->parent->unsetLayout();
+    }
+
     delete d;
 }
 

layouts/layoutitem.cpp

@@ -90,13 +90,18 @@ void LayoutItem::setLayout(Layout* layout)
     if (d->layout == layout) {
         return;
     }
+
     delete d->layout;
+    d->layout = layout;
 
     if (layout) {
         layout->setParent(this);
     }
+}
 
-    d->layout = layout;
+void LayoutItem::unsetLayout()
+{
+    d->layout = 0;
 }
 
 Layout* LayoutItem::layout() const

layouts/layoutitem.h

@@ -117,12 +117,22 @@ class PLASMA_EXPORT LayoutItem
         virtual QSizeF sizeHint() const = 0;
 
         /**
-         * Sets the layout that will manage children items
+         * Sets the layout that will manage children items. The LayoutItem
+         * takes ownership of the layout from that point forward, unless
+         * unsetLayout() is called.
          *
          * @param layout The Layout that this LayoutItem will be managed by.
          */
         void setLayout(Layout* layout);
 
+        /**
+         * Resets the layout that will manage children items to no layout.
+         * Note that the caller of this method must alert any items managed
+         * by the layout of this change if necessary. Primarily, this should
+         * only be used from the dtors of LayoutItem subclasses.
+         */
+        void unsetLayout();
+
         /**
          * @return the layout this item is currently associated with.
          */