add QQuickPointerEvent::touchEventForItem

It's similar to QQuickWindowPrivate::touchEventWithPoints(), and is
used in the same way when delivering a QQuickPointerEvent by sending
a QTouchEvent to the item's event() method.

Change-Id: I0d181eaf924bfdad2db2de9d8acf85d0345aec3e
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

2 files changed, 75 insertions, 1 deletions

diff --git a/src/quick/items/qquickevents.cpp b/src/quick/items/qquickevents.cpp
index 520e5d2704..50714518b1 100644
--- a/src/quick/items/qquickevents.cpp
+++ b/src/quick/items/qquickevents.cpp
@@ -38,6 +38,7 @@
 ****************************************************************************/
 
 #include "qquickevents_p_p.h"
+#include <QtQuick/private/qquickitem_p.h>
 #include <QtQuick/private/qquickwindow_p.h>
 
 QT_BEGIN_NAMESPACE
@@ -535,4 +536,69 @@ bool QQuickPointerEvent::isTabletEvent() const
     }
 }
 
+/*
+   \internal
+
+   make a new QTouchEvent, giving it a subset of the original touch points
+*/
+QTouchEvent *QQuickPointerEvent::touchEventForItem(const QList<const QQuickEventPoint *> &newPoints, QQuickItem *relativeTo) const
+{
+    QList<QTouchEvent::TouchPoint> touchPoints;
+    Qt::TouchPointStates eventStates;
+    // TODO maybe add QQuickItem::mapVector2DFromScene(QVector2D) to avoid needing QQuickItemPrivate here
+    // Or else just document that velocity is always scene-relative and is not scaled and rotated with the item
+    // but that would require changing tst_qquickwindow::touchEvent_velocity(): it expects transformed velocity
+    QMatrix4x4 transformMatrix(QQuickItemPrivate::get(relativeTo)->windowToItemTransform());
+    for (const QQuickEventPoint * p : newPoints) {
+        const QTouchEvent::TouchPoint *tp = touchPointById(p->pointId());
+        if (tp) {
+            eventStates |= tp->state();
+            QTouchEvent::TouchPoint tpCopy = *tp;
+            tpCopy.setPos(relativeTo->mapFromScene(tpCopy.scenePos()));
+            tpCopy.setLastPos(relativeTo->mapFromScene(tpCopy.lastPos()));
+            tpCopy.setStartPos(relativeTo->mapFromScene(tpCopy.startScenePos()));
+            tpCopy.setRect(relativeTo->mapRectFromScene(tpCopy.sceneRect()));
+            tpCopy.setVelocity(transformMatrix.mapVector(tpCopy.velocity()).toVector2D());
+            touchPoints << tpCopy;
+        }
+    }
+
+    // if all points have the same state, set the event type accordingly
+    const QTouchEvent &event = *asTouchEvent();
+    QEvent::Type eventType = event.type();
+    switch (eventStates) {
+    case Qt::TouchPointPressed:
+        eventType = QEvent::TouchBegin;
+        break;
+    case Qt::TouchPointReleased:
+        eventType = QEvent::TouchEnd;
+        break;
+    default:
+        eventType = QEvent::TouchUpdate;
+        break;
+    }
+
+    QTouchEvent *touchEvent = new QTouchEvent(eventType);
+    touchEvent->setWindow(event.window());
+    touchEvent->setTarget(relativeTo);
+    touchEvent->setDevice(event.device());
+    touchEvent->setModifiers(event.modifiers());
+    touchEvent->setTouchPoints(touchPoints);
+    touchEvent->setTouchPointStates(eventStates);
+    touchEvent->setTimestamp(event.timestamp());
+    touchEvent->accept();
+    return touchEvent;
+}
+
+const QTouchEvent::TouchPoint *QQuickPointerEvent::touchPointById(int pointId) const {
+    const QTouchEvent *ev = asTouchEvent();
+    if (!ev)
+        return nullptr;
+    const QList<QTouchEvent::TouchPoint> &tps = ev->touchPoints();
+    auto it = std::find_if(tps.constBegin(), tps.constEnd(),
+        [&pointId](QTouchEvent::TouchPoint const& tp) { return tp.id() == pointId; } );
+    // return the pointer to the actual TP in QTouchEvent::_touchPoints
+    return (it == tps.end() ? nullptr : it.operator->());
+}
+
 QT_END_NAMESPACE
diff --git a/src/quick/items/qquickevents_p_p.h b/src/quick/items/qquickevents_p_p.h
index c4c4daf830..af3e385ce6 100644
--- a/src/quick/items/qquickevents_p_p.h
+++ b/src/quick/items/qquickevents_p_p.h
@@ -378,6 +378,8 @@ private:
     QPointerUniqueId m_uniqueId;
 };
 
+class QQuickItem;
+
 class Q_QUICK_PRIVATE_EXPORT QQuickPointerEvent : public QObject
 {
     Q_OBJECT
@@ -406,6 +408,9 @@ public:
     Qt::MouseButton button() const { return m_button; }
     Qt::MouseButtons buttons() const { return m_pressedButtons; }
 
+    // ----------------------------------------------------
+    // helpers for C++ event delivery, not for QML properties
+
     /** Returns the original touch event. */
     QTouchEvent *asTouchEvent() const;
 
@@ -414,7 +419,6 @@ public:
      * Returns nullptr in case the original event was not a mouse event. */
     QMouseEvent *asMouseEvent() const;
 
-    // helpers for C++ event delivery, not for QML properties
     int pointCount() const { return asTouchEvent() ? m_touchPoints.count() : 1; }
     const QQuickEventPoint *point(int i) const {
         if (asTouchEvent())
@@ -422,6 +426,10 @@ public:
         return i == 0 ? m_mousePoint : nullptr;
     }
 
+    const QTouchEvent::TouchPoint *touchPointById(int pointId) const;
+
+    QTouchEvent *touchEventForItem(const QList<const QQuickEventPoint *> &newPoints, QQuickItem *relativeTo) const;
+
 protected:
     bool isValid() const { return m_event != nullptr; }