Slider: don't break the binding on value when using the mouse wheel

When the wheel was used it could cause any binding on value to be broken
since it was updated directly. Going via range.position ensures this is
not the case.

Change-Id: Ic041ea911cee68de34f5c4e184cf8460f5e002da
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

2 files changed, 35 insertions, 2 deletions

diff --git a/src/controls/Slider.qml b/src/controls/Slider.qml
index e290640e..07ad74c4 100644
--- a/src/controls/Slider.qml
+++ b/src/controls/Slider.qml
@@ -331,14 +331,14 @@ Control {
         onVerticalWheelMoved: {
             if (verticalDelta !== 0) {
                 var delta = Math.abs(verticalDelta)*step > stepSize ? verticalDelta*step : verticalDelta/Math.abs(verticalDelta)*stepSize
-                value -= delta * (inverted ? 1 : -1)
+                range.position = range.positionForValue(value - delta * (inverted ? 1 : -1))
             }
         }
 
         onHorizontalWheelMoved: {
             if (horizontalDelta !== 0) {
                 var delta = Math.abs(horizontalDelta)*step > stepSize ? horizontalDelta*step : horizontalDelta/Math.abs(horizontalDelta)*stepSize
-                value += delta * (inverted ? 1 : -1)
+                range.position = range.positionForValue(value + delta * (inverted ? 1 : -1))
             }
         }
     }
diff --git a/tests/auto/controls/data/tst_slider.qml b/tests/auto/controls/data/tst_slider.qml
index e95d26d9..f6435314 100644
--- a/tests/auto/controls/data/tst_slider.qml
+++ b/tests/auto/controls/data/tst_slider.qml
@@ -439,5 +439,38 @@ Item {
 
             control.destroy();
         }
+
+        Component {
+            id: mouseWheelSlider
+            Slider {
+                 property real boundValue: 10
+                 width: 300
+                 height: 50
+                 minimumValue: 0
+                 maximumValue: 200
+                 stepSize: 2
+                 value: boundValue
+             }
+        }
+
+        function test_mouseWheelWithValueBinding() {
+            var slider = createTemporaryObject(mouseWheelSlider, container)
+            slider.forceActiveFocus()
+
+            var defaultScrollSpeed = 20.0
+            var mouseStep = 15.0
+            var deltatUnit = 8.0
+            var mouseRatio = deltatUnit * mouseStep / defaultScrollSpeed;
+            var sliderDeltaRatio = 1; //(slider.maximumValue - slider.minimumValue)/slider.width
+            var ratio = mouseRatio / sliderDeltaRatio
+
+            compare(slider.value, 10)
+
+            mouseWheel(slider, 5, 5, -20 * ratio, 0)
+            compare(slider.value, 24)
+
+            slider.boundValue = 50
+            compare(slider.value, 50)
+        }
     }
 }