Destroy QWindowContainer's fake parent window when not needed

Keeping the fake parent window around in a created state means we're
wasting system resources such as native platform views/windows, and
makes it harder to debug the lifetime of these resources.

The fake window will be re-created if re-parented into at a later
point.

Change-Id: Ib82560e7e565af19d58afe121fd087669a6ffb95
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/widgets/kernel/qwindowcontainer.cpp b/src/widgets/kernel/qwindowcontainer.cpp
index 4ef34f0102..4b289d2d33 100644
--- a/src/widgets/kernel/qwindowcontainer.cpp
+++ b/src/widgets/kernel/qwindowcontainer.cpp
@@ -315,6 +315,7 @@ bool QWindowContainer::event(QEvent *e)
             d->window->setParent(d->usesNativeWidgets
                                  ? windowHandle()
                                  : window()->windowHandle());
+            d->fakeParent.destroy();
         }
         if (d->window->parent()) {
             d->markParentChain();
@@ -404,6 +405,7 @@ void QWindowContainer::parentWasChanged(QWidget *parent)
                 Q_ASSERT(toplevel->windowHandle());
             }
             d->window->setParent(toplevel->windowHandle());
+            d->fakeParent.destroy();
             d->updateGeometry();
         }
     }