Reset QWidget's winId when backing window surface is destroyed

We already reset it though e.g. QWidget::destroy, but if the backing
window is destroyed spontaneously or via another API we need to catch
that and send a WinIdChange event so clients who pulled out the original
winId will not think the pointer is still valid

Change-Id: I8556940ee871e81a51f73daeb2064f95bf41371c
Fixes: QTBUG-69289
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 2c84ff7161..53d87c6113 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -9365,6 +9365,12 @@ bool QWidget::event(QEvent *event)
         d->renderToTextureReallyDirty = 1;
 #endif
         break;
+    case QEvent::PlatformSurface: {
+        auto surfaceEvent = static_cast<QPlatformSurfaceEvent*>(event);
+        if (surfaceEvent->surfaceEventType() == QPlatformSurfaceEvent::SurfaceAboutToBeDestroyed)
+            d->setWinId(0);
+        break;
+    }
 #ifndef QT_NO_PROPERTIES
     case QEvent::DynamicPropertyChange: {
         const QByteArray &propName = static_cast<QDynamicPropertyChangeEvent *>(event)->propertyName();