[Quick] Make sure an transition instance is stopped when replaced

When a running transition does not finish of natural causes (reached
the end state due to e.g. the timer finishing), it can happen that it
will never be marked as finished. Specifically, when an transition is
running (e.g. an add animation for a ListView), and that transition is
replaced by another transition (a displace transition, because another
item got added to the ListView before the add transition was finished),
the first animation was never marked as stopped. The effect was that
the running property would stay "true" for forever.

Task-number: QTBUG-38099
Change-Id: Icbcc732f787ff23c72d843f1ecaa86a2cc9c75ec
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/quick/items/qquickitemviewtransition.cpp b/src/quick/items/qquickitemviewtransition.cpp
index c06dcce0d9..0fde0beb75 100644
--- a/src/quick/items/qquickitemviewtransition.cpp
+++ b/src/quick/items/qquickitemviewtransition.cpp
@@ -500,6 +500,8 @@ void QQuickItemViewTransitionableItem::startTransition(QQuickItemViewTransitione
     }
 
     if (!transition || transition->m_type != nextTransitionType || transition->m_isTarget != isTransitionTarget) {
+        if (transition)
+            transition->cancel();
         delete transition;
         transition = new QQuickItemViewTransitionJob;
     }