Add QQuickPointerEvent::syntheticMouseEvent

It makes it easier to send synthetic mouse events for touch.

Change-Id: Ibb8e2737e3245ae7438708aa170ec1f888e770d8
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

2 files changed, 52 insertions, 1 deletions

diff --git a/src/quick/items/qquickevents.cpp b/src/quick/items/qquickevents.cpp
index ad5a007b37..d09294b515 100644
--- a/src/quick/items/qquickevents.cpp
+++ b/src/quick/items/qquickevents.cpp
@@ -38,6 +38,7 @@
 ****************************************************************************/
 
 #include "qquickevents_p_p.h"
+#include <QtGui/private/qguiapplication_p.h>
 #include <QtQuick/private/qquickitem_p.h>
 #include <QtQuick/private/qquickwindow_p.h>
 
@@ -574,6 +575,52 @@ const QQuickEventPoint *QQuickPointerEvent::point(int i) const {
 
 /*!
     \internal
+    Populate the reusable synth-mouse event from one touchpoint.
+    It's required that isTouchEvent() be true when this is called.
+    If the touchpoint cannot be found, this returns nullptr.
+    Ownership of the event is NOT transferred to the caller.
+*/
+QMouseEvent *QQuickPointerEvent::syntheticMouseEvent(int pointID, QQuickItem *relativeTo) const {
+    const QTouchEvent::TouchPoint *p = touchPointById(pointID);
+    if (!p)
+        return nullptr;
+    QEvent::Type type;
+    Qt::MouseButton buttons = Qt::LeftButton;
+    switch (p->state()) {
+    case Qt::TouchPointPressed:
+        type = QEvent::MouseButtonPress;
+        break;
+    case Qt::TouchPointMoved:
+    case Qt::TouchPointStationary:
+        type = QEvent::MouseMove;
+        break;
+    case Qt::TouchPointReleased:
+        type = QEvent::MouseButtonRelease;
+        buttons = Qt::NoButton;
+        break;
+    default:
+        Q_ASSERT(false);
+        return nullptr;
+    }
+    m_synthMouseEvent = QMouseEvent(type, relativeTo->mapFromScene(p->scenePos()),
+        p->scenePos(), p->screenPos(), Qt::LeftButton, buttons, m_event->modifiers());
+    m_synthMouseEvent.setAccepted(true);
+    m_synthMouseEvent.setTimestamp(m_event->timestamp());
+    // In the future we will try to always have valid velocity in every QQuickEventPoint.
+    // QQuickFlickablePrivate::handleMouseMoveEvent() checks for QTouchDevice::Velocity
+    // and if it is set, then it does not need to do its own velocity calculations.
+    // That's probably the only usecase for this, so far.  Some day Flickable should handle
+    // pointer events, and then passing touchpoint velocity via QMouseEvent will be obsolete.
+    // Conveniently (by design), QTouchDevice::Velocity == QQuickPointerDevice.Velocity
+    // so that we don't need to convert m_device->capabilities().
+    if (m_device)
+        QGuiApplicationPrivate::setMouseEventCapsAndVelocity(&m_synthMouseEvent, m_device->capabilities(), p->velocity());
+    QGuiApplicationPrivate::setMouseEventSource(&m_synthMouseEvent, Qt::MouseEventSynthesizedByQt);
+    return &m_synthMouseEvent;
+}
+
+/*!
+    \internal
     Returns a pointer to the original TouchPoint which has the same
     \l {QTouchEvent::TouchPoint::id}{id} as \a pointId, if the original event is a
     QTouchEvent, and if that point is found. Otherwise, returns nullptr.
diff --git a/src/quick/items/qquickevents_p_p.h b/src/quick/items/qquickevents_p_p.h
index 0a306e8b46..65a9ae190a 100644
--- a/src/quick/items/qquickevents_p_p.h
+++ b/src/quick/items/qquickevents_p_p.h
@@ -396,7 +396,8 @@ public:
       , m_button(Qt::NoButton)
       , m_pressedButtons(Qt::NoButton)
       , m_pointCount(0)
-      , m_mousePoint(nullptr) { }
+      , m_mousePoint(nullptr)
+      , m_synthMouseEvent(QEvent::MouseMove, QPointF(), Qt::NoButton, Qt::NoButton, Qt::NoModifier) { }
 
 public: // property accessors
     const QQuickPointerDevice *device() const { return m_device; }
@@ -422,6 +423,8 @@ public: // helpers for C++ only (during event delivery)
 
     QTouchEvent *touchEventForItem(const QList<const QQuickEventPoint *> &newPoints, QQuickItem *relativeTo) const;
 
+    QMouseEvent *syntheticMouseEvent(int pointID, QQuickItem *relativeTo) const;
+
 private:
     void initFromMouse(QMouseEvent *ev);
     void initFromTouch(QTouchEvent *ev);
@@ -434,6 +437,7 @@ private:
     int m_pointCount;
     QVector<QQuickEventTouchPoint *> m_touchPoints;
     QQuickEventPoint *m_mousePoint;
+    mutable QMouseEvent m_synthMouseEvent;
 
     Q_DISABLE_COPY(QQuickPointerEvent)
 };