use new signals slots syntax

src/ui/HeaderBar.cpp

@@ -36,10 +36,10 @@ HeaderBar::HeaderBar(QWidget* parent)
         layout->addWidget(btn);
         m_speedButtons.push_back(btn);
         mapper->setMapping(btn, i);
-        connect(btn, SIGNAL(clicked()), mapper, SLOT(map()));
+        connect(btn, &QPushButton::clicked, mapper, qOverload<>(&QSignalMapper::map));
     }
-    connect(mapper, SIGNAL(mapped(int)), this, SLOT(onSpeedButton(int)));
-
+    connect(mapper, qOverload<int>(&QSignalMapper::mapped), this, &HeaderBar::onSpeedButton);
+	
     setFixedHeight(sizeHint().height());
 }
 
@@ -70,3 +70,4 @@ void HeaderBar::onSpeedButton(int index)
         emit speedChanged(kSpeeds[index]);
     }
 }
+