Fix memory leak with QQuickEventPoint

Store PointVelocityData by value in the QMap to avoid leaking memory.
This also appears to be slightly faster than heap allocation, with
the struct being relatively small (24 or 32 bytes depending on qreal).

Fixes: QTBUG-73182
Change-Id: Ibd9374746b76fd5b78c23283d278b6af42907c96
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

1 files changed, 16 insertions, 22 deletions

diff --git a/src/quick/items/qquickevents.cpp b/src/quick/items/qquickevents.cpp
index c43eab6b8a..28b217b7b3 100644
--- a/src/quick/items/qquickevents.cpp
+++ b/src/quick/items/qquickevents.cpp
@@ -1135,10 +1135,10 @@ void QQuickEventTouchPoint::reset(const QTouchEvent::TouchPoint &tp, ulong times
 struct PointVelocityData {
     QVector2D velocity;
     QPointF pos;
-    ulong timestamp;
+    ulong timestamp = 0;
 };
 
-typedef QMap<quint64, PointVelocityData*> PointDataForPointIdMap;
+typedef QMap<quint64, PointVelocityData> PointDataForPointIdMap;
 Q_GLOBAL_STATIC(PointDataForPointIdMap, g_previousPointData)
 static const int PointVelocityAgeLimit = 500; // milliseconds
 
@@ -1149,42 +1149,36 @@ static const int PointVelocityAgeLimit = 500; // milliseconds
 */
 QVector2D QQuickEventPoint::estimatedVelocity() const
 {
-    PointVelocityData *prevPoint = g_previousPointData->value(m_pointId);
-    if (!prevPoint) {
+    auto prevPointIt = g_previousPointData->find(m_pointId);
+    auto end = g_previousPointData->end();
+    if (prevPointIt == end) {
         // cleanup events older than PointVelocityAgeLimit
-        auto end = g_previousPointData->end();
         for (auto it = g_previousPointData->begin(); it != end; ) {
-            PointVelocityData *data = it.value();
-            if (m_timestamp - data->timestamp > PointVelocityAgeLimit) {
+            if (m_timestamp - it->timestamp > PointVelocityAgeLimit)
                 it = g_previousPointData->erase(it);
-                delete data;
-            } else {
+            else
                 ++it;
-            }
         }
-        // TODO optimize: stop this dynamic memory thrashing
-        prevPoint = new PointVelocityData;
-        prevPoint->velocity = QVector2D();
-        prevPoint->timestamp = 0;
-        prevPoint->pos = QPointF();
-        g_previousPointData->insert(m_pointId, prevPoint);
+        prevPointIt = g_previousPointData->insert(m_pointId, PointVelocityData());
     }
-    const ulong timeElapsed = m_timestamp - prevPoint->timestamp;
+
+    auto &prevPoint = prevPointIt.value();
+    const ulong timeElapsed = m_timestamp - prevPoint.timestamp;
     if (timeElapsed == 0)   // in case we call estimatedVelocity() twice on the same QQuickEventPoint
         return m_velocity;
 
     QVector2D newVelocity;
-    if (prevPoint->timestamp != 0)
-        newVelocity = QVector2D(m_scenePos - prevPoint->pos)/timeElapsed;
+    if (prevPoint.timestamp != 0)
+        newVelocity = QVector2D(m_scenePos - prevPoint.pos) / timeElapsed;
 
     // VERY simple kalman filter: does a weighted average
     // where the older velocities get less and less significant
     static const float KalmanGain = 0.7f;
     QVector2D filteredVelocity = newVelocity * KalmanGain + m_velocity * (1.0f - KalmanGain);
 
-    prevPoint->velocity = filteredVelocity;
-    prevPoint->pos = m_scenePos;
-    prevPoint->timestamp = m_timestamp;
+    prevPoint.velocity = filteredVelocity;
+    prevPoint.pos = m_scenePos;
+    prevPoint.timestamp = m_timestamp;
     return filteredVelocity;
 }