Expose drag threshold in MouseArea

In several cases such as for creating a Slider, it is useful to  have a
0 pixel threshold in order to initiate a drag operation. We have
previously hardcoded this to a platform dependent (usually 10 pixel)
value for MouseArea.

Note that we have no way of indicating the version/revision number
in a grouped property for documentation at the moment.

In addition we deliberately had to remove the REVISION from the
property because it is blocked by QTBUG-33179. However, since
this is not a user-creatable type it should not cause any
issues in practice.

This patch adds MouseArea.drag.threshold in order to improve on this.

Change-Id: Ia4871e64fab39e30c4494f00be99ad38cdd630df
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index c8bc026868..513c3da0a2 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -2077,13 +2077,13 @@ bool QQuickWindowPrivate::sendFilteredMouseEvent(QQuickItem *target, QQuickItem
     return false;
 }
 
-bool QQuickWindowPrivate::dragOverThreshold(qreal d, Qt::Axis axis, QMouseEvent *event)
+bool QQuickWindowPrivate::dragOverThreshold(qreal d, Qt::Axis axis, QMouseEvent *event, int startDragThreshold)
 {
     QStyleHints *styleHints = qApp->styleHints();
     int caps = QGuiApplicationPrivate::mouseEventCaps(event);
     bool dragVelocityLimitAvailable = (caps & QTouchDevice::Velocity)
         && styleHints->startDragVelocity();
-    bool overThreshold = qAbs(d) > styleHints->startDragDistance();
+    bool overThreshold = qAbs(d) > (startDragThreshold >= 0 ? startDragThreshold : styleHints->startDragDistance());
     if (dragVelocityLimitAvailable) {
         QVector2D velocityVec = QGuiApplicationPrivate::mouseEventVelocity(event);
         qreal velocity = axis == Qt::XAxis ? velocityVec.x() : velocityVec.y();