Add a function for QPA plugins to explicitly destroy QScreens

Previously QPlatformScreen was automatically deleting its QScreen
in ~QPlatformScreen(). That means that we cannot use QScreen's
methods when the screen is being removed, because doing so would
call virtual methods of QPlatformScreen. By that point the
QPlatformScreen subclass object does not exist anymore, and we
call the default implementation instead of the subclassed one, or
get a crash for the pure virtual methods. This happens for example
when removing a screen which contains a QWindow with some QML item
using QQuickScreenAttached.

This patch adds a QPlatformIntegration::destroyScreen() function,
which deletes the QScreen and later the QPlatformScreen.

~QPlatformScreen will still delete the QScreen if it was not deleted
with destroyScreen(), so code not ported to the new approach
will continue to work as before, with only a warning added.

Task-number: QTBUG-41141
Change-Id: Ie4a03dee08ceb4c3e94a81875411f6f723273fe1
Reviewed-by: Jørgen Lind <jorgen.lind@theqtcompany.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.mm b/src/plugins/platforms/cocoa/qcocoaintegration.mm
index 72bd09625a..180cb23669 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.mm
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.mm
@@ -337,7 +337,7 @@ QCocoaIntegration::~QCocoaIntegration()
 
     // Delete screens in reverse order to avoid crash in case of multiple screens
     while (!mScreens.isEmpty()) {
-        delete mScreens.takeLast();
+        destroyScreen(mScreens.takeLast());
     }
 
     clearToolbars();
@@ -397,7 +397,7 @@ void QCocoaIntegration::updateScreens()
     // Now the leftovers in remainingScreens are no longer current, so we can delete them.
     foreach (QCocoaScreen* screen, remainingScreens) {
         mScreens.removeOne(screen);
-        delete screen;
+        destroyScreen(screen);
     }
     // All screens in mScreens are siblings, because we ignored the mirrors.
     foreach (QCocoaScreen* screen, mScreens)