PinchHandler: make the properties useful when target is null

An example is forthcoming in the form of a documentation snippet.
Also, translation is a relative measurement, so its type is now
QVector2D rather than QPointF.  This doesn't change the QML API:
x and y properties are still defined.

Change-Id: I00f9a02a45c30899a568fe827f47cae9b4cc0f42
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

2 files changed, 21 insertions, 18 deletions

diff --git a/src/quick/handlers/qquickpinchhandler.cpp b/src/quick/handlers/qquickpinchhandler.cpp
index 92bcc643f3..b1a5779981 100644
--- a/src/quick/handlers/qquickpinchhandler.cpp
+++ b/src/quick/handlers/qquickpinchhandler.cpp
@@ -198,23 +198,26 @@ void QQuickPinchHandler::setMaximumY(qreal maxY)
 void QQuickPinchHandler::onActiveChanged()
 {
     if (active()) {
+        m_startMatrix = QMatrix4x4();
+        m_startCentroid = touchPointCentroid();
+        m_startAngles = angles(m_startCentroid);
+        m_startDistance = averageTouchPointDistance(m_startCentroid);
+        m_activeRotation = 0;
+        m_activeTranslation = QVector2D();
         if (const QQuickItem *t = target()) {
             m_startScale = t->scale(); // TODO incompatible with independent x/y scaling
             m_startRotation = t->rotation();
-            m_startCentroid = touchPointCentroid();
-            m_startAngles = angles(m_startCentroid);
-            m_startDistance = averageTouchPointDistance(m_startCentroid);
             QVector3D xformOrigin(t->transformOriginPoint());
-            m_startMatrix = QMatrix4x4();
             m_startMatrix.translate(t->x(), t->y());
             m_startMatrix.translate(xformOrigin);
             m_startMatrix.scale(m_startScale);
             m_startMatrix.rotate(m_startRotation, 0, 0, -1);
             m_startMatrix.translate(-xformOrigin);
-            m_activeRotation = 0;
-            m_activeTranslation = QPointF(0,0);
-            qCInfo(lcPinchHandler) << "activated with starting scale" << m_startScale << "rotation" << m_startRotation;
+        } else {
+            m_startScale = 1;
+            m_startRotation = 0;
         }
+        qCInfo(lcPinchHandler) << "activated with starting scale" << m_startScale << "rotation" << m_startRotation;
     } else {
         qCInfo(lcPinchHandler) << "deactivated with scale" << m_activeScale << "rotation" << m_activeRotation;
     }
@@ -271,7 +274,7 @@ void QQuickPinchHandler::handlePointerEventImpl(QQuickPointerEvent *event)
     if (target() && target()->parentItem()) {
         // 3. Drag/translate
         const QPointF centroidStartParentPos = target()->parentItem()->mapFromScene(m_startCentroid);
-        m_activeTranslation = centroidParentPos - centroidStartParentPos;
+        m_activeTranslation = QVector2D(centroidParentPos - centroidStartParentPos);
 
         // apply rotation + scaling around the centroid - then apply translation.
         QMatrix4x4 mat;
@@ -293,15 +296,15 @@ void QQuickPinchHandler::handlePointerEventImpl(QQuickPointerEvent *event)
         target()->setRotation(rotation);
         target()->setScale(scale);
 
-
         // TODO some translation inadvertently happens; try to hold the chosen pinch origin in place
-
-        qCDebug(lcPinchHandler) << "centroid" << m_startCentroid << "->"  << m_centroid
-                                << ", distance" << m_startDistance << "->" << dist
-                                << ", startScale" << m_startScale << "->" << scale
-                                << ", activeRotation" << m_activeRotation
-                                << ", rotation" << rotation;
+    } else {
+        m_activeTranslation = QVector2D(m_centroid - m_startCentroid);
     }
+    qCDebug(lcPinchHandler) << "centroid" << m_startCentroid << "->"  << m_centroid
+                            << ", distance" << m_startDistance << "->" << dist
+                            << ", startScale" << m_startScale << "->" << scale
+                            << ", activeRotation" << m_activeRotation
+                            << ", rotation" << rotation;
 
     if (!containsReleasedPoints)
         acceptPoints(m_currentPoints);
diff --git a/src/quick/handlers/qquickpinchhandler_p.h b/src/quick/handlers/qquickpinchhandler_p.h
index 356cc0eed3..b1ece494a5 100644
--- a/src/quick/handlers/qquickpinchhandler_p.h
+++ b/src/quick/handlers/qquickpinchhandler_p.h
@@ -70,7 +70,7 @@ class Q_AUTOTEST_EXPORT QQuickPinchHandler : public QQuickMultiPointHandler
     Q_PROPERTY(QVector2D centroidVelocity READ centroidVelocity NOTIFY updated)
     Q_PROPERTY(qreal scale READ scale NOTIFY updated)
     Q_PROPERTY(qreal rotation READ rotation NOTIFY updated)
-    Q_PROPERTY(QPointF translation READ translation NOTIFY updated)
+    Q_PROPERTY(QVector2D translation READ translation NOTIFY updated)
     Q_PROPERTY(qreal minimumX READ minimumX WRITE setMinimumX NOTIFY minimumXChanged)
     Q_PROPERTY(qreal maximumX READ maximumX WRITE setMaximumX NOTIFY maximumXChanged)
     Q_PROPERTY(qreal minimumY READ minimumY WRITE setMinimumY NOTIFY minimumYChanged)
@@ -100,7 +100,7 @@ public:
     PinchOrigin pinchOrigin() const { return m_pinchOrigin; }
     void setPinchOrigin(PinchOrigin pinchOrigin);
 
-    QPointF translation() const { return m_activeTranslation; }
+    QVector2D translation() const { return m_activeTranslation; }
     qreal scale() const { return m_activeScale; }
     qreal rotation() const { return m_activeRotation; }
     QPointF centroid() const { return m_centroid; }
@@ -136,7 +136,7 @@ private:
     // properties
     qreal m_activeScale;
     qreal m_activeRotation;
-    QPointF m_activeTranslation;
+    QVector2D m_activeTranslation;
     QPointF m_centroid;
     QVector2D m_centroidVelocity;