Add helper function to reset QMouseEvent localPos

In Qt Quick there are many places which copy mouse events repeatedly,
with the only goal of adjusting the local position. Instead it's much
more sensible to re-use the same event.

Change-Id: I2c6f2b73ee3a7a6df489f813cf2f60b48a6e48df
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

3 files changed, 35 insertions, 0 deletions

diff --git a/src/gui/kernel/qevent.cpp b/src/gui/kernel/qevent.cpp
index 47c1f91fb0..d574ba5cc6 100644
--- a/src/gui/kernel/qevent.cpp
+++ b/src/gui/kernel/qevent.cpp
@@ -405,6 +405,18 @@ Qt::MouseEventFlags QMouseEvent::flags() const
 */
 
 /*!
+    \fn void QMouseEvent::setLocalPos(const QPointF &localPosition)
+
+    \since 5.8
+
+    \internal
+
+    Sets the local position in the mouse event to \a localPosition. This allows to re-use one event
+    when sending it to a series of receivers that expect the local pos in their
+    respective local coordinates.
+*/
+
+/*!
     \fn QPointF QMouseEvent::windowPos() const
 
     \since 5.0
diff --git a/src/gui/kernel/qevent.h b/src/gui/kernel/qevent.h
index fb8a49b1c6..fb72c561ab 100644
--- a/src/gui/kernel/qevent.h
+++ b/src/gui/kernel/qevent.h
@@ -132,6 +132,8 @@ public:
     inline Qt::MouseButton button() const { return b; }
     inline Qt::MouseButtons buttons() const { return mouseState; }
 
+    inline void setLocalPos(const QPointF &localPosition) { l = localPosition; }
+
 #if QT_DEPRECATED_SINCE(5, 0)
     QT_DEPRECATED inline QPointF posF() const { return l; }
 #endif
diff --git a/tests/auto/gui/kernel/qmouseevent/tst_qmouseevent.cpp b/tests/auto/gui/kernel/qmouseevent/tst_qmouseevent.cpp
index 6af6738bdb..a1de205571 100644
--- a/tests/auto/gui/kernel/qmouseevent/tst_qmouseevent.cpp
+++ b/tests/auto/gui/kernel/qmouseevent/tst_qmouseevent.cpp
@@ -75,6 +75,7 @@ public slots:
     void cleanupTestCase();
     void init();
 private slots:
+    void mouseEventBasic();
     void checkMousePressEvent_data();
     void checkMousePressEvent();
     void checkMouseReleaseEvent_data();
@@ -107,6 +108,26 @@ void tst_QMouseEvent::init()
     testMouseWidget->mouseReleaseModifiers = 0;
 }
 
+void tst_QMouseEvent::mouseEventBasic()
+{
+    QPointF local(100, 100);
+    QPointF scene(200, 200);
+    QPointF screen(300, 300);
+    QMouseEvent me(QEvent::MouseButtonPress, local, scene, screen, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
+    QCOMPARE(me.isAccepted(), true);
+    QCOMPARE(me.button(), Qt::LeftButton);
+    QCOMPARE(me.buttons(), Qt::LeftButton);
+    QCOMPARE(me.localPos(), local);
+    QCOMPARE(me.windowPos(), scene);
+    QCOMPARE(me.screenPos(), screen);
+
+    QPointF changedLocal(33, 66);
+    me.setLocalPos(changedLocal);
+    QCOMPARE(me.localPos(), changedLocal);
+    QCOMPARE(me.windowPos(), scene);
+    QCOMPARE(me.screenPos(), screen);
+}
+
 void tst_QMouseEvent::checkMousePressEvent_data()
 {
     QTest::addColumn<int>("buttonPressed");