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, 23 insertions, 2 deletions

diff --git a/src/quick/items/qquickdrag.cpp b/src/quick/items/qquickdrag.cpp
index 0ae26cb5c3..166b40aaf2 100644
--- a/src/quick/items/qquickdrag.cpp
+++ b/src/quick/items/qquickdrag.cpp
@@ -45,11 +45,12 @@
 #include <QtQuick/private/qquickevents_p_p.h>
 #include <private/qquickitemchangelistener_p.h>
 #include <private/qv8engine_p.h>
-#include <QtCore/qcoreapplication.h>
 #include <QtCore/qmimedata.h>
 #include <QtQml/qqmlinfo.h>
 #include <QtGui/qdrag.h>
 #include <QtGui/qevent.h>
+#include <QtGui/qstylehints.h>
+#include <QtGui/qguiapplication.h>
 
 #ifndef QT_NO_DRAGANDDROP
 
@@ -785,7 +786,8 @@ void QQuickDragAttached::startDrag(QQmlV4Function *args)
 
 QQuickDrag::QQuickDrag(QObject *parent)
 : QObject(parent), _target(0), _axis(XAndYAxis), _xmin(-FLT_MAX),
-_xmax(FLT_MAX), _ymin(-FLT_MAX), _ymax(FLT_MAX), _active(false), _filterChildren(false)
+_xmax(FLT_MAX), _ymin(-FLT_MAX), _ymax(FLT_MAX), _active(false), _filterChildren(false),
+  _threshold(qApp->styleHints()->startDragDistance())
 {
 }
 
@@ -879,6 +881,25 @@ void QQuickDrag::setYmax(qreal m)
     emit maximumYChanged();
 }
 
+
+qreal QQuickDrag::threshold() const
+{
+    return _threshold;
+}
+
+void QQuickDrag::setThreshold(qreal value)
+{
+    if (_threshold != value) {
+        _threshold = value;
+        emit thresholdChanged();
+    }
+}
+
+void QQuickDrag::resetThreshold()
+{
+    setThreshold(qApp->styleHints()->startDragDistance());
+}
+
 bool QQuickDrag::active() const
 {
     return _active;