Chip example: fix an accidental bool->int conversion when using PMF connections

The example was refactored to use the PMF connection syntax.
However this introduced a problem: when connecting a QAbstractButton
to a slot that has a default parameter, the semantics of the connection
change between string-based connections and PMF.

Specifically: when connecting the

  QAbstractButton::clicked(bool checked = false)

signal to a slot like

  View::zoomIn(int level = 1)

then a string-based connection like

  connect(button, SIGNAL(clicked()), this, SLOT(zoomIn()))

would call zoomIn without carrying the signal's parameter over.
In other words, zoomIn's parameter is defaulted. The same connection
using PFM instead is

  connect(button, &QAbstractButton::clicked,
          this, &View::zoomIn)

which would "connect" the arguments. This makes emissions that pass
false as clicked's parameter result in a zoomIn by 0.

Fix it by avoiding the default parameter of zoomIn -- just split
the function in two (zoomIn and zoomInBy).

Amends 8cf8122314.

Pick-to: 5.15 6.2 6.3
Fixes: QTBUG-100135
Done-with: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Change-Id: I10c150c648034449e3154140108de2d64326d965
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

examples/widgets/graphicsview/chip/view.cpp

@@ -65,9 +65,9 @@ void GraphicsView::wheelEvent(QWheelEvent *e)
 {
     if (e->modifiers() & Qt::ControlModifier) {
         if (e->angleDelta().y() > 0)
-            view->zoomIn(6);
+            view->zoomInBy(6);
         else
-            view->zoomOut(6);
+            view->zoomOutBy(6);
         e->accept();
     } else {
         QGraphicsView::wheelEvent(e);
@@ -253,12 +253,22 @@ void View::print()
 #endif
 }
 
-void View::zoomIn(int level)
+void View::zoomIn()
+{
+    zoomSlider->setValue(zoomSlider->value() + 1);
+}
+
+void View::zoomOut()
+{
+    zoomSlider->setValue(zoomSlider->value() - 1);
+}
+
+void View::zoomInBy(int level)
 {
     zoomSlider->setValue(zoomSlider->value() + level);
 }
 
-void View::zoomOut(int level)
+void View::zoomOutBy(int level)
 {
     zoomSlider->setValue(zoomSlider->value() - level);
 }

examples/widgets/graphicsview/chip/view.h

@@ -86,8 +86,10 @@ public:
     QGraphicsView *view() const;
 
 public slots:
-    void zoomIn(int level = 1);
-    void zoomOut(int level = 1);
+    void zoomIn();
+    void zoomOut();
+    void zoomInBy(int level);
+    void zoomOutBy(int level);
 
 private slots:
     void resetView();