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>

2 files changed, 3 insertions, 3 deletions

diff --git a/examples/widgets/draganddrop/draggabletext/dragwidget.cpp b/examples/widgets/draganddrop/draggabletext/dragwidget.cpp
index fb169b953b..2135ba2ef9 100644
--- a/examples/widgets/draganddrop/draggabletext/dragwidget.cpp
+++ b/examples/widgets/draganddrop/draggabletext/dragwidget.cpp
@@ -123,7 +123,7 @@ void DragWidget::dropEvent(QDropEvent *event)
             hotSpot.setY(hotSpotPos.last().toInt());
         }
 
-        foreach (const QString &piece, pieces) {
+        for (const QString &piece : pieces) {
             QLabel *newLabel = createDragLabel(piece, this);
             newLabel->move(position - hotSpot);
             newLabel->show();
@@ -141,7 +141,7 @@ void DragWidget::dropEvent(QDropEvent *event)
     } else {
         event->ignore();
     }
-    foreach (QWidget *widget, findChildren<QWidget *>()) {
+    for (QWidget *widget : findChildren<QWidget *>()) {
         if (!widget->isVisible())
             widget->deleteLater();
     }
diff --git a/examples/widgets/draganddrop/draggabletext/dragwidget.h b/examples/widgets/draganddrop/draggabletext/dragwidget.h
index 24d1f6f5c7..38abb0ceb8 100644
--- a/examples/widgets/draganddrop/draggabletext/dragwidget.h
+++ b/examples/widgets/draganddrop/draggabletext/dragwidget.h
@@ -61,7 +61,7 @@ QT_END_NAMESPACE
 class DragWidget : public QWidget
 {
 public:
-    DragWidget(QWidget *parent = 0);
+    explicit DragWidget(QWidget *parent = nullptr);
 
 protected:
     void dragEnterEvent(QDragEnterEvent *event) override;