QQmlDelegateModel: On deletion, cancel any remaining incubations

This fixes the memory leaks from the "x items in the process of being
created at engine destruction" situation.

Change-Id: I65fe278ead3d4de0cbddc075972a6774b231814f
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 12 insertions, 2 deletions

diff --git a/src/qmlmodels/qqmldelegatemodel.cpp b/src/qmlmodels/qqmldelegatemodel.cpp
index 095b66b379..a68631830d 100644
--- a/src/qmlmodels/qqmldelegatemodel.cpp
+++ b/src/qmlmodels/qqmldelegatemodel.cpp
@@ -269,13 +269,23 @@ QQmlDelegateModel::~QQmlDelegateModel()
             Q_ASSERT(cacheItem->contextData->refCount == 1);
             cacheItem->contextData = nullptr;
             cacheItem->scriptRef -= 1;
+        } else if (cacheItem->incubationTask) {
+            // Both the incubationTask and the object may hold a scriptRef,
+            // but if both are present, only one scriptRef is held in total.
+            cacheItem->scriptRef -= 1;
         }
+
         cacheItem->groups &= ~Compositor::UnresolvedFlag;
         cacheItem->objectRef = 0;
+
+        if (cacheItem->incubationTask) {
+            d->releaseIncubator(cacheItem->incubationTask);
+            cacheItem->incubationTask->vdm = nullptr;
+            cacheItem->incubationTask = nullptr;
+        }
+
         if (!cacheItem->isReferenced())
             delete cacheItem;
-        else if (cacheItem->incubationTask)
-            cacheItem->incubationTask->vdm = nullptr;
     }
 }