Refactor transform code in pinchhandler to a separate function

This is needed in order for the wheel handler to have the same behavior.

Change-Id: I42851789787b8da96618d82227b34c53ace15e9b
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

3 files changed, 43 insertions, 21 deletions

diff --git a/src/quick/handlers/qquickpinchhandler.cpp b/src/quick/handlers/qquickpinchhandler.cpp
index 1bee656fc3..4025cd7fbf 100644
--- a/src/quick/handlers/qquickpinchhandler.cpp
+++ b/src/quick/handlers/qquickpinchhandler.cpp
@@ -464,27 +464,10 @@ void QQuickPinchHandler::handlePointerEventImpl(QQuickPointerEvent *event)
         const QPointF centroidStartParentPos = target()->parentItem()->mapFromScene(centroid().sceneGrabPosition());
         m_activeTranslation = QVector2D(centroidParentPos - centroidStartParentPos);
         // apply rotation + scaling around the centroid - then apply translation.
-        QMatrix4x4 mat, startMatrix;
-
-        const QVector3D centroidParentVector(centroidParentPos);
-        mat.translate(centroidParentVector);
-        mat.rotate(float(m_activeRotation), 0, 0, 1);
-        mat.scale(float(m_activeScale));
-        mat.translate(-centroidParentVector);
-        mat.translate(QVector3D(m_activeTranslation));
-
-        QVector3D xformOrigin(target()->transformOriginPoint());
-        startMatrix.translate(float(m_startPos.x()), float(m_startPos.y()));
-        startMatrix.translate(xformOrigin);
-        startMatrix.scale(float(m_startScale));
-        startMatrix.rotate(float(m_startRotation), 0, 0, -1);
-        startMatrix.translate(-xformOrigin);
-
-        mat = mat * startMatrix;
-
-        QPointF xformOriginPoint = target()->transformOriginPoint();
-        QPointF pos = mat * xformOriginPoint;
-        pos -= xformOriginPoint;
+        QPointF pos = QQuickItemPrivate::get(target())->adjustedPosForTransform(centroidParentPos,
+                                                                                m_startPos, m_activeTranslation,
+                                                                                m_startScale, m_activeScale,
+                                                                                m_startRotation, m_activeRotation);
 
         if (xAxis()->enabled())
             pos.setX(qBound(xAxis()->minimum(), pos.x(), xAxis()->maximum()));
diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index ec6bf5a1b8..7469fee72b 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -5122,6 +5122,40 @@ void QQuickItemPrivate::transformChanged()
 #endif
 }
 
+QPointF QQuickItemPrivate::adjustedPosForTransform(const QPointF &centroidParentPos,
+                                                   const QPointF &startPos,
+                                                   const QVector2D &activeTranslation,  //[0,0] means no additional translation from startPos
+                                                   qreal startScale,
+                                                   qreal activeScale,                   // 1.0 means no additional scale from startScale
+                                                   qreal startRotation,
+                                                   qreal activeRotation)                // 0.0 means no additional rotation from startRotation
+{
+    Q_Q(QQuickItem);
+    QVector3D xformOrigin(q->transformOriginPoint());
+    QMatrix4x4 startMatrix;
+    startMatrix.translate(float(startPos.x()), float(startPos.y()));
+    startMatrix.translate(xformOrigin);
+    startMatrix.scale(float(startScale));
+    startMatrix.rotate(float(startRotation), 0, 0, -1);
+    startMatrix.translate(-xformOrigin);
+
+    const QVector3D centroidParentVector(centroidParentPos);
+    QMatrix4x4 mat;
+    mat.translate(centroidParentVector);
+    mat.rotate(float(activeRotation), 0, 0, 1);
+    mat.scale(float(activeScale));
+    mat.translate(-centroidParentVector);
+    mat.translate(QVector3D(activeTranslation));
+
+    mat = mat * startMatrix;
+
+    QPointF xformOriginPoint = q->transformOriginPoint();
+    QPointF pos = mat * xformOriginPoint;
+    pos -= xformOriginPoint;
+
+    return pos;
+}
+
 bool QQuickItemPrivate::filterKeyEvent(QKeyEvent *e, bool post)
 {
     if (!extra.isAllocated() || !extra->keyHandler)
diff --git a/src/quick/items/qquickitem_p.h b/src/quick/items/qquickitem_p.h
index 771228914b..847fd90230 100644
--- a/src/quick/items/qquickitem_p.h
+++ b/src/quick/items/qquickitem_p.h
@@ -591,6 +591,11 @@ public:
     QPointF computeTransformOrigin() const;
     virtual void transformChanged();
 
+    QPointF adjustedPosForTransform(const QPointF &centroid,
+                                    const QPointF &startPos, const QVector2D &activeTranslatation,
+                                    qreal startScale, qreal activeScale,
+                                    qreal startRotation, qreal activeRotation);
+
     void deliverKeyEvent(QKeyEvent *);
     bool filterKeyEvent(QKeyEvent *, bool post);
 #if QT_CONFIG(im)