Fix pointer mismatch after QList::move() in tooltip example

The tooltip example moves shape items within a QWidget. Shape items are
stored in a QList of objects. When an item is moved, its pointer is
taken from the QList and stored in a member variable. To have the moved
item on the bottom of the list, QList::move() is called. This
operation re-arranges the list objects, and the member variable starts
pointing at a wrong object.

This patch changes the list from a list of objects, to a list of
pointers. Shape items are therefore allocated on the heap.
A destructor is added to free the heap with qDeleteAll.

The example's documentation is adapted accordingly and a snippet for
the destructor is added.

As a drive-by, int is replaced by qsizetype where it was used as an
index of a QList.

Fixes: QTBUG-104781
Pick-to: 6.5 6.2
Change-Id: I9be26fa7954be5f85729d24f166d66980af71801
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

examples/widgets/doc/src/tooltips.qdoc

@@ -124,6 +124,10 @@
     private \c createShapeItem(), \c initialItemPosition() and \c
     initialItemColor() functions.
 
+    \snippet widgets/tooltips/sortingbox.cpp 27
+
+    In the destructor, we delete all shape items.
+
     \snippet widgets/tooltips/sortingbox.cpp 5
 
     QWidget::event() is the main event handler and receives all the
@@ -199,8 +203,9 @@
     If an item covers the position, we store a pointer to that item
     and the event's position. If several of the shape items cover the
     position, we store the pointer to the uppermost item. Finally, we
-    move the shape item to the end of the list, and make a call to the
-    QWidget::update() function to make the item appear on top.
+    move the shape item's pointer to the end of the list, and make
+    a call to the QWidget::update() function to make the item appear
+    on top.
 
     The QWidget::update() function does not cause an immediate
     repaint; instead it schedules a paint event for processing when Qt
@@ -290,10 +295,9 @@
 
     The \c createShapeItem() function creates a single shape item. It
     sets the path, tooltip, position and color, using the item's own
-    functions. In the end, the function appends the new item to the
-    list of shape items, and calls the QWidget::update() function to
-    make it appear with the other items within the \c SortingBox
-    widget.
+    functions. In the end, the function appends the new item's pointer
+    to the list of shape items, and calls QWidget::update() to make
+    it appear with the other items within the \c SortingBox widget.
 
     \snippet widgets/tooltips/sortingbox.cpp 22
 

examples/widgets/widgets/tooltips/sortingbox.cpp

@@ -59,6 +59,13 @@ SortingBox::SortingBox(QWidget *parent)
 }
 //! [4]
 
+//! [27]
+SortingBox::~SortingBox()
+{
+    qDeleteAll(shapeItems);
+}
+//! [27]
+
 //! [5]
 bool SortingBox::event(QEvent *event)
 {
@@ -67,7 +74,7 @@ bool SortingBox::event(QEvent *event)
         QHelpEvent *helpEvent = static_cast<QHelpEvent *>(event);
         int index = itemAt(helpEvent->pos());
         if (index != -1) {
-            QToolTip::showText(helpEvent->globalPos(), shapeItems[index].toolTip());
+            QToolTip::showText(helpEvent->globalPos(), shapeItems[index]->toolTip());
         } else {
             QToolTip::hideText();
             event->ignore();
@@ -97,13 +104,13 @@ void SortingBox::paintEvent(QPaintEvent * /* event */)
 {
     QPainter painter(this);
     painter.setRenderHint(QPainter::Antialiasing);
-    for (const ShapeItem &shapeItem : std::as_const(shapeItems)) {
+    for (const ShapeItem *shapeItem : std::as_const(shapeItems)) {
 //! [8] //! [9]
-        painter.translate(shapeItem.position());
+        painter.translate(shapeItem->position());
 //! [9] //! [10]
-        painter.setBrush(shapeItem.color());
-        painter.drawPath(shapeItem.path());
-        painter.translate(-shapeItem.position());
+        painter.setBrush(shapeItem->color());
+        painter.drawPath(shapeItem->path());
+        painter.translate(-shapeItem->position());
     }
 }
 //! [10]
@@ -114,7 +121,7 @@ void SortingBox::mousePressEvent(QMouseEvent *event)
     if (event->button() == Qt::LeftButton) {
         int index = itemAt(event->position().toPoint());
         if (index != -1) {
-            itemInMotion = &shapeItems[index];
+            itemInMotion = shapeItems[index];
             previousPosition = event->position().toPoint();
             shapeItems.move(index, shapeItems.size() - 1);
             update();
@@ -169,11 +176,11 @@ void SortingBox::createNewTriangle()
 //! [16]
 
 //! [17]
-int SortingBox::itemAt(const QPoint &pos)
+qsizetype SortingBox::itemAt(const QPoint &pos)
 {
-    for (int i = shapeItems.size() - 1; i >= 0; --i) {
-        const ShapeItem &item = shapeItems[i];
-        if (item.path().contains(pos - item.position()))
+    for (qsizetype i = shapeItems.size() - 1; i >= 0; --i) {
+        const ShapeItem *item = shapeItems[i];
+        if (item->path().contains(pos - item->position()))
             return i;
     }
     return -1;
@@ -208,11 +215,11 @@ void SortingBox::createShapeItem(const QPainterPath &path,
                                  const QString &toolTip, const QPoint &pos,
                                  const QColor &color)
 {
-    ShapeItem shapeItem;
-    shapeItem.setPath(path);
-    shapeItem.setToolTip(toolTip);
-    shapeItem.setPosition(pos);
-    shapeItem.setColor(color);
+    ShapeItem *shapeItem = new ShapeItem;
+    shapeItem->setPath(path);
+    shapeItem->setToolTip(toolTip);
+    shapeItem->setPosition(pos);
+    shapeItem->setColor(color);
     shapeItems.append(shapeItem);
     update();
 }

examples/widgets/widgets/tooltips/sortingbox.h

@@ -21,6 +21,7 @@ class SortingBox : public QWidget
 
 public:
     SortingBox(QWidget *parent = nullptr);
+    ~SortingBox();
 
 protected:
     bool event(QEvent *event) override;
@@ -41,7 +42,7 @@ private:
     int updateButtonGeometry(QToolButton *button, int x, int y);
     void createShapeItem(const QPainterPath &path, const QString &toolTip,
                          const QPoint &pos, const QColor &color);
-    int itemAt(const QPoint &pos);
+    qsizetype itemAt(const QPoint &pos);
     void moveItemTo(const QPoint &pos);
     QPoint initialItemPosition(const QPainterPath &path);
     QPoint randomItemPosition();
@@ -53,7 +54,7 @@ private:
                                   const PointerToMemberFunction &member);
 
 //! [2]
-    QList<ShapeItem> shapeItems;
+    QList<ShapeItem *> shapeItems;
     QPainterPath circlePath;
     QPainterPath squarePath;
     QPainterPath trianglePath;