Add dragThreshold property to Event Handlers

We need drag threshold to be adjustable on each handler instance instead
of relying only on the system default drag threshold. For example in
some use cases DragHandler needs to work with a threshold of 0 or 1 to
start dragging as soon as the point is pressed or as soon as the point
is moved, with no "jump", to enable fine adjustment of a value on some
control such as a Slider.

This involves moving the dragOverThreshold() functions that handlers are
using from QQuickWindowPrivate to QQuickPointerHandlerPrivate, so that
they can use the adjustable threshold value.

Task-number: QTBUG-68075
Change-Id: Ie720cbbf9f30abb40d1731d92f8e7f1e6534eeb5
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/quick/handlers/qquickpointerhandler_p.h b/src/quick/handlers/qquickpointerhandler_p.h
index c600e42491..995db9c1dc 100644
--- a/src/quick/handlers/qquickpointerhandler_p.h
+++ b/src/quick/handlers/qquickpointerhandler_p.h
@@ -71,6 +71,7 @@ class Q_QUICK_PRIVATE_EXPORT QQuickPointerHandler : public QObject, public QQmlP
     Q_PROPERTY(QQuickItem * parent READ parentItem CONSTANT)
     Q_PROPERTY(GrabPermissions grabPermissions READ grabPermissions WRITE setGrabPermissions NOTIFY grabPermissionChanged)
     Q_PROPERTY(qreal margin READ margin WRITE setMargin NOTIFY marginChanged)
+    Q_PROPERTY(int dragThreshold READ dragThreshold WRITE setDragThreshold RESET resetDragThreshold NOTIFY dragThresholdChanged REVISION 15)
 
 public:
     explicit QQuickPointerHandler(QQuickItem *parent = nullptr);
@@ -110,11 +111,16 @@ public:
     qreal margin() const;
     void setMargin(qreal pointDistanceThreshold);
 
+    int dragThreshold() const;
+    void setDragThreshold(int t);
+    void resetDragThreshold();
+
 Q_SIGNALS:
     void enabledChanged();
     void activeChanged();
     void targetChanged();
     void marginChanged();
+    Q_REVISION(15) void dragThresholdChanged();
     void grabChanged(QQuickEventPoint::GrabTransition transition, QQuickEventPoint *point);
     void grabPermissionChanged();
     void canceled(QQuickEventPoint *point);