Revamp QtWidgets/DragAndDrop examples to C++11

Introduce nullptr and replace foreach with new C++11 range based for
loops. Minor fixups of signals, file dialog usage.

Apply the same changes to the ItemViews/puzzle example since it
shares parts of the code with DragAndDrop/puzzle. Make some
changes to both examples to that the diff of the two becomes
small for easier comparison.

Task-number: QTBUG-60635
Change-Id: I8af824229ebac24d6ec151eae92176d227695490
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/examples/widgets/draganddrop/puzzle/pieceslist.cpp b/examples/widgets/draganddrop/puzzle/pieceslist.cpp
index 30890ecf9b..7846d37ed2 100644
--- a/examples/widgets/draganddrop/puzzle/pieceslist.cpp
+++ b/examples/widgets/draganddrop/puzzle/pieceslist.cpp
@@ -101,7 +101,7 @@ void PiecesList::dropEvent(QDropEvent *event)
     }
 }
 
-void PiecesList::addPiece(QPixmap pixmap, QPoint location)
+void PiecesList::addPiece(const QPixmap &pixmap, const QPoint &location)
 {
     QListWidgetItem *pieceItem = new QListWidgetItem(this);
     pieceItem->setIcon(QIcon(pixmap));