macOS: Avoid modifying hash while iterating it

QCocoaTouch sneakily updated the list of active touches in the
destructor, causing problems when we switched from Q_FOREACH
to ranged-for.

Fixes: QTBUG-83876
Change-Id: If7ec9e9116b7eb581580b461ae12ad70c739906d
Reviewed-by: Simon Hausmann <hausmann@gmail.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/plugins/platforms/cocoa/qmultitouch_mac.mm b/src/plugins/platforms/cocoa/qmultitouch_mac.mm
index 95256657fe..ac2317b217 100644
--- a/src/plugins/platforms/cocoa/qmultitouch_mac.mm
+++ b/src/plugins/platforms/cocoa/qmultitouch_mac.mm
@@ -184,7 +184,10 @@ QCocoaTouch::getCurrentTouchPointList(NSEvent *event, bool acceptSingleTouch)
     if (_touchCount != _currentTouches.size()) {
         // Remove all instances, and basically start from scratch:
         touchPoints.clear();
-        for (QCocoaTouch *qcocoaTouch : _currentTouches) {
+        // Deleting touch points will remove them from current touches,
+        // so we make a copy of the touches before iterating them.
+        const auto currentTouchesSnapshot = _currentTouches;
+        for (QCocoaTouch *qcocoaTouch : currentTouchesSnapshot) {
             if (!_updateInternalStateOnly) {
                 qcocoaTouch->_touchPoint.state = Qt::TouchPointReleased;
                 touchPoints.insert(qcocoaTouch->_touchPoint.id, qcocoaTouch->_touchPoint);