Fix rare duplicate ids forming in touch point id's mapping

QTouchEvent may contain touch point release and press simultaneously
in this particular order. Hence if mapping for released point is deleted
before id is chosen for pressed one, output transformed list may contain
points with same ids. Since new touch points delivered before released
one, this will lead to assert in chromium about duplicate ids.

Change-Id: I209d7d8c752c7bd74d2580ef65478c92e54cb099
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 7 insertions, 1 deletions

diff --git a/src/core/render_widget_host_view_qt.cpp b/src/core/render_widget_host_view_qt.cpp
index 525e9924e..f8e20d188 100644
--- a/src/core/render_widget_host_view_qt.cpp
+++ b/src/core/render_widget_host_view_qt.cpp
@@ -1251,6 +1251,7 @@ void RenderWidgetHostViewQt::processMotionEvent(const ui::MotionEvent &motionEve
 
 QList<QTouchEvent::TouchPoint> RenderWidgetHostViewQt::mapTouchPointIds(const QList<QTouchEvent::TouchPoint> &inputPoints)
 {
+    QList<int> idsToRemove;
     QList<QTouchEvent::TouchPoint> outputPoints = inputPoints;
     for (int i = 0; i < outputPoints.size(); ++i) {
         QTouchEvent::TouchPoint &point = outputPoints[i];
@@ -1262,9 +1263,14 @@ QList<QTouchEvent::TouchPoint> RenderWidgetHostViewQt::mapTouchPointIds(const QL
         point.setId(it.value());
 
         if (point.state() == Qt::TouchPointReleased)
-            m_touchIdMapping.remove(qtId);
+            idsToRemove.append(qtId);
     }
 
+    for (int qtId : qAsConst(idsToRemove))
+        m_touchIdMapping.remove(qtId);
+
+    Q_ASSERT(outputPoints.size() == std::accumulate(outputPoints.cbegin(), outputPoints.cend(), QSet<int>(),
+                [] (QSet<int> s, const QTouchEvent::TouchPoint &p) { s.insert(p.id()); return s; }).size());
     return outputPoints;
 }