Introduce QGraphicsLayoutItem::isEmpty()

This change does basically two things:
* Renames QGraphicsGridLayoutEngineItem::isIgnored() to
  QGraphicsGridLayoutEngineItem::isEmpty() to be consistent with
  QLayoutItem::isEmpty()

* Creates a new public API function QGraphicsLayoutItem::isEmpty() so
  that there is a public method of overriding the behavior.

Change-Id: I771a8fb429f9764a75e220f0ff9d07f578f981d3
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/widgets/graphicsview/qgraphicslayoutitem.cpp b/src/widgets/graphicsview/qgraphicslayoutitem.cpp
index 8694dcb36b..2c484321e4 100644
--- a/src/widgets/graphicsview/qgraphicslayoutitem.cpp
+++ b/src/widgets/graphicsview/qgraphicslayoutitem.cpp
@@ -45,6 +45,7 @@
 #include "qgraphicslayoutitem_p.h"
 #include "qwidget.h"
 #include "qgraphicswidget.h"
+#include "qgraphicsitem_p.h"
 
 #include <QtDebug>
 
@@ -826,6 +827,22 @@ void QGraphicsLayoutItem::updateGeometry()
 }
 
 /*!
+ * returns \c true if this item is empty, i.e whether it has no content and
+ * should not occupy any space.
+ *
+ * The default implementation returns true if the item has been hidden unless
+ * its size policy has retainSizeWhenHidden set to \c true
+ */
+bool QGraphicsLayoutItem::isEmpty() const
+{
+    bool isHidden = false;
+    if (QGraphicsItem *item = graphicsItem())
+        isHidden = QGraphicsItemPrivate::get(item)->explicitlyHidden;
+
+    return isHidden && !sizePolicy().retainSizeWhenHidden();
+}
+
+/*!
     Returns the parent of this QGraphicsLayoutItem, or \nullptr if there is
     no parent, or if the parent does not inherit from QGraphicsLayoutItem
     (QGraphicsLayoutItem is often used through multiple inheritance with