From d599451e24b68c1555d965e3566bd9b74bf1b6a2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tor=20Arne=20Vestb=C3=B8?= <tor.arne.vestbo@qt.io>
Date: Fri, 22 Sep 2023 17:39:28 +0200
Subject: [PATCH] Guard QWindowsContext::instance() during screen change on
 shutdown
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Destructing the QWindowsScreenManager might result in a
WM_DISPLAYCHANGE, at which point our QWindowsContext instance
is likely gone. We need to guard against that.

Fixes: QTBUG-117473
Pick-to: 6.5
Change-Id: If32941c5c11231f7c27e9dde54f4315f18da1100
Reviewed-by: Wladimir Leuschner <wladimir.leuschner@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Timothée Keller <timothee.keller@qt.io>
(cherry picked from commit 7d663d2e08fb71801f0f1f084a124e706722bf0f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/plugins/platforms/windows/qwindowsscreen.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/plugins/platforms/windows/qwindowsscreen.cpp b/src/plugins/platforms/windows/qwindowsscreen.cpp
index 6b85a68f69b..677a4dcadeb 100644
--- a/src/plugins/platforms/windows/qwindowsscreen.cpp
+++ b/src/plugins/platforms/windows/qwindowsscreen.cpp
@@ -656,7 +656,8 @@ extern "C" LRESULT QT_WIN_CALLBACK qDisplayChangeObserverWndProc(HWND hwnd, UINT
         if (QWindowsTheme *t = QWindowsTheme::instance())
             t->displayChanged();
         QWindowsWindow::displayChanged();
-        QWindowsContext::instance()->screenManager().handleScreenChanges();
+        if (auto *context = QWindowsContext::instance())
+            context->screenManager().handleScreenChanges();
     }
 
     return DefWindowProc(hwnd, message, wParam, lParam);