[doc] Fix docs of QLayoutItem::widget()

QWidget does not inherit QLayoutItem (unlike QLayout and QSpacerItem, which do),
so don't claim that in the docs.

Added a note.

Added cross-references between layout(), widget() and spacerItem().

Change-Id: I518b6842ef76fd1b72226b790dab75f429fae556
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Topi Reiniö <topi.reinio@theqtcompany.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/src/widgets/kernel/qlayoutitem.cpp b/src/widgets/kernel/qlayoutitem.cpp
index 03988aab99..41944d63ac 100644
--- a/src/widgets/kernel/qlayoutitem.cpp
+++ b/src/widgets/kernel/qlayoutitem.cpp
@@ -300,6 +300,8 @@ void QLayoutItem::invalidate()
 /*!
     If this item is a QLayout, it is returned as a QLayout; otherwise
     0 is returned. This function provides type-safe casting.
+
+    \sa spacerItem(), widget()
 */
 QLayout * QLayoutItem::layout()
 {
@@ -309,6 +311,8 @@ QLayout * QLayoutItem::layout()
 /*!
     If this item is a QSpacerItem, it is returned as a QSpacerItem;
     otherwise 0 is returned. This function provides type-safe casting.
+
+    \sa layout(), widget()
 */
 QSpacerItem * QLayoutItem::spacerItem()
 {
@@ -339,8 +343,14 @@ QSpacerItem * QSpacerItem::spacerItem()
 */
 
 /*!
-    If this item is a QWidget, it is returned as a QWidget; otherwise
-    0 is returned. This function provides type-safe casting.
+    If this item manages a QWidget, returns that widget. Otherwise,
+    \c nullptr is returned.
+
+    \note While the functions layout() and spacerItem() perform casts, this
+    function returns another object: QLayout and QSpacerItem inherit QLayoutItem,
+    while QWidget does not.
+
+    \sa layout(), spacerItem()
 */
 QWidget * QLayoutItem::widget()
 {