Sync QWindow visible state during QWidget destruction

A call to QWidget::destroy() will end up in QWindow::destroy(), which
calls QWindow::setVisible(false).

A call to QWindow::setVisible(false) on a widget's window will under
normal circumstances end up in QWidgetPrivate::setVisible(), which in
turn recurses back into QWindowPrivate::setVisible(), via
QWidgetPrivate::hide_helper(), ensuring that the QWindow internal
state is updated, visibleChanged emitted, and show/hide events sent.

Durin QWidget::destroy() we end up in QWindow::destroy(), which calls
QWindow::setVisible(false), but in this case the widget no longer has
Qt::WA_WState_Created, so the hide_helper() call is skipped, and the
corresponding QWindow is not kept in the loop.

To work around this we could have checked for windowHandle() instead
of Qt::WA_WState_Created before calling hide_helper(), but that had
many other side effects, so we opt for a more targeted fix.

Pick-to: 6.5
Change-Id: I68f80e5f7df9ee811afcd274a7ee4de31a110da5
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
(cherry picked from commit 5b09d9e6d694045a6cef15f8984bab63cf86402c)
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
(cherry picked from commit 3bc3cf3ba95819c85fc94cb4bcd65ef6d6748efa)

2 files changed, 39 insertions, 0 deletions

diff --git a/src/widgets/kernel/qwidgetwindow.cpp b/src/widgets/kernel/qwidgetwindow.cpp
index d86af94a9c..99c54b9d98 100644
--- a/src/widgets/kernel/qwidgetwindow.cpp
+++ b/src/widgets/kernel/qwidgetwindow.cpp
@@ -51,6 +51,17 @@ public:
                 widget->setAttribute(Qt::WA_WState_ExplicitShowHide, wasExplicitShowHide);
                 widget->setAttribute(Qt::WA_WState_Hidden, wasHidden);
             }
+
+            // The call to QWidgetPrivate::setVisible() above will normally
+            // recurse back into QWidgetWindow::setNativeWindowVisibility()
+            // to update the QWindow state, but during QWidget::destroy()
+            // this is not the case, as Qt::WA_WState_Created has been
+            // unset by the time we check if we should call hide_helper().
+            // We don't want to change the QWidget logic, as that has
+            // other side effects, so as a targeted fix we sync up the
+            // visibility here if needed.
+            if (q->isVisible() != visible)
+                QWindowPrivate::setVisible(visible);
         } else {
             QWindowPrivate::setVisible(visible);
         }
diff --git a/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp b/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
index 549206875c..5d19aa3c75 100644
--- a/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
+++ b/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp
@@ -433,6 +433,8 @@ private slots:
     void showFullscreenAndroid();
 #endif
 
+    void setVisibleDuringDestruction();
+
 private:
     const QString m_platform;
     QSize m_testWidgetSize;
@@ -13403,5 +13405,31 @@ void tst_QWidget::showFullscreenAndroid()
 }
 #endif // Q_OS_ANDROID
 
+void tst_QWidget::setVisibleDuringDestruction()
+{
+    CreateDestroyWidget widget;
+    widget.create();
+    QVERIFY(widget.windowHandle());
+
+    QSignalSpy signalSpy(widget.windowHandle(), &QWindow::visibleChanged);
+    EventSpy<QWindow> showEventSpy(widget.windowHandle(), QEvent::Show);
+    widget.show();
+    QTRY_COMPARE(showEventSpy.count(), 1);
+    QTRY_COMPARE(signalSpy.count(), 1);
+
+    EventSpy<QWindow> hideEventSpy(widget.windowHandle(), QEvent::Hide);
+    widget.hide();
+    QTRY_COMPARE(hideEventSpy.count(), 1);
+    QTRY_COMPARE(signalSpy.count(), 2);
+
+    widget.show();
+    QTRY_COMPARE(showEventSpy.count(), 2);
+    QTRY_COMPARE(signalSpy.count(), 3);
+
+    widget.destroy();
+    QTRY_COMPARE(hideEventSpy.count(), 2);
+    QTRY_COMPARE(signalSpy.count(), 4);
+}
+
 QTEST_MAIN(tst_QWidget)
 #include "tst_qwidget.moc"