Slider: add wheel support

Change-Id: I413d8c853bfe3cc748584dfebd28172ead89d638
Task-number: QTBUG-50221
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>

src/templates/qquickslider.cpp

@@ -565,6 +565,20 @@ void QQuickSlider::mouseUngrabEvent()
     setPressed(false);
 }
 
+void QQuickSlider::wheelEvent(QWheelEvent *event)
+{
+    Q_D(QQuickSlider);
+    QQuickControl::wheelEvent(event);
+    if (d->wheelEnabled) {
+        const qreal oldValue = d->value;
+        const QPointF angle = event->angleDelta();
+        const qreal delta = (qFuzzyIsNull(angle.y()) ? angle.x() : angle.y()) / QWheelEvent::DefaultDeltasPerStep;
+        const qreal step = qFuzzyIsNull(d->stepSize) ? 0.1 : d->stepSize;
+        setValue(oldValue + step * delta);
+        event->setAccepted(!qFuzzyCompare(d->value, oldValue));
+    }
+}
+
 void QQuickSlider::mirrorChange()
 {
     QQuickControl::mirrorChange();

src/templates/qquickslider_p.h

@@ -133,6 +133,8 @@ protected:
     void mouseMoveEvent(QMouseEvent *event) override;
     void mouseReleaseEvent(QMouseEvent *event) override;
     void mouseUngrabEvent() override;
+    void wheelEvent(QWheelEvent *event) override;
+
     void mirrorChange() override;
     void componentComplete() override;
 

tests/auto/controls/data/tst_slider.qml

@@ -471,4 +471,51 @@ TestCase {
 
         control.destroy()
     }
+
+    function test_wheel_data() {
+        return [
+            { tag: "horizontal", orientation: Qt.Horizontal, dx: 120, dy: 0 },
+            { tag: "vertical", orientation: Qt.Vertical, dx: 0, dy: 120 }
+        ]
+    }
+
+    function test_wheel(data) {
+        var control = slider.createObject(testCase, {wheelEnabled: true, orientation: data.orientation})
+        verify(control)
+
+        compare(control.value, 0.0)
+
+        mouseWheel(control, control.width / 2, control.height / 2, data.dx, data.dy)
+        compare(control.value, 0.1)
+        compare(control.position, 0.1)
+
+        control.stepSize = 0.2
+
+        mouseWheel(control, control.width / 2, control.height / 2, data.dx, data.dy)
+        compare(control.value, 0.3)
+        compare(control.position, 0.3)
+
+        control.stepSize = 10.0
+
+        mouseWheel(control, control.width / 2, control.height / 2, -data.dx, -data.dy)
+        compare(control.value, 0.0)
+        compare(control.position, 0.0)
+
+        control.to = 10.0
+        control.stepSize = 5.0
+
+        mouseWheel(control, control.width / 2, control.height / 2, data.dx, data.dy)
+        compare(control.value, 5.0)
+        compare(control.position, 0.5)
+
+        mouseWheel(control, control.width / 2, control.height / 2, 0.5 * data.dx, 0.5 * data.dy)
+        compare(control.value, 7.5)
+        compare(control.position, 0.75)
+
+        mouseWheel(control, control.width / 2, control.height / 2, -data.dx, -data.dy)
+        compare(control.value, 2.5)
+        compare(control.position, 0.25)
+
+        control.destroy()
+    }
 }