Check thread->isRunning before posting WMReleaseSwapchainEvent

If the window becomes "obscured" (hidden), rendering (i.e. the render
thread) stops. Getting a PlatformSurfaceAboutToBeDestroyed afterwards
led to sending (and blocking) the WMReleaseSwapchainEvent to the render
thread. This lead to a deadlock. While this is not something that
happens normally, the problem is showcased by the "headless" case of
the qquickwindow autotest which has a quite aggressive destroy() call
on the QQuickWindow.

Change-Id: I4726b76646564162af645508e08e35e268fea7e4
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/quick/scenegraph/qsgthreadedrenderloop.cpp b/src/quick/scenegraph/qsgthreadedrenderloop.cpp
index 20ed00664a..0a62f85388 100644
--- a/src/quick/scenegraph/qsgthreadedrenderloop.cpp
+++ b/src/quick/scenegraph/qsgthreadedrenderloop.cpp
@@ -1413,7 +1413,7 @@ bool QSGThreadedRenderLoop::eventFilter(QObject *watched, QEvent *event)
             QQuickWindow *window = qobject_cast<QQuickWindow *>(watched);
             if (window) {
                 Window *w = windowFor(m_windows, window);
-                if (w) {
+                if (w && w->thread->isRunning()) {
                     w->thread->mutex.lock();
                     w->thread->postEvent(new WMReleaseSwapchainEvent(window));
                     w->thread->waitCondition.wait(&w->thread->mutex);