[macOS] Check that the screen's index is still valid after updating

It is possible for a screen to be disconnected while it is doing an
update of the available screens. Therefore before returning the pointer
to the screen then it should be rechecked that the index is still within
the range of available screens.

Change-Id: Iaa08070e79a72cb309d8a24cea786a5dccf6b719
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@theqtcompany.com>

2 files changed, 6 insertions, 1 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.mm b/src/plugins/platforms/cocoa/qcocoaintegration.mm
index 933160b2ca..659c803a19 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.mm
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.mm
@@ -450,6 +450,10 @@ QCocoaScreen *QCocoaIntegration::screenAtIndex(int index)
     if (index >= mScreens.count())
         updateScreens();
 
+    // It is possible that the screen got removed while updateScreens was called
+    // so we do a sanity check to be certain
+    if (index >= mScreens.count())
+        return 0;
     return mScreens.at(index);
 }
 
diff --git a/src/plugins/platforms/cocoa/qnsview.mm b/src/plugins/platforms/cocoa/qnsview.mm
index 4e482fb146..913ce08d17 100644
--- a/src/plugins/platforms/cocoa/qnsview.mm
+++ b/src/plugins/platforms/cocoa/qnsview.mm
@@ -469,7 +469,8 @@ QT_WARNING_POP
             NSUInteger screenIndex = [[NSScreen screens] indexOfObject:self.window.screen];
             if (screenIndex != NSNotFound) {
                 QCocoaScreen *cocoaScreen = QCocoaIntegration::instance()->screenAtIndex(screenIndex);
-                QWindowSystemInterface::handleWindowScreenChanged(m_window, cocoaScreen->screen());
+                if (cocoaScreen)
+                    QWindowSystemInterface::handleWindowScreenChanged(m_window, cocoaScreen->screen());
                 m_platformWindow->updateExposedGeometry();
             }
         }