Don't quit automatically via QEventLoopLocker if there are open windows

As part of df359bcb703db5a8adbf14e88ba4ae0d54f0cfcd the semantics and
interaction between QEventLoopLocker and QGuiApplication was changed,
based on the assumption that these two mechanisms were independent
and should not affect each other.

This had a surprising regression where the use of QEventLoopLocker in
combination with the QCoreApplication::isQuitLockEnabled() automatic
quit would end up quitting the app, even if it had open windows, for
example when the last job of some internal job queue finished.

It could be argued that if the app has open windows that should not
be closed, they should ignore the Close event, and that an application
with running QEventLoopLocker jobs should maintain an active window
showing the progress of those jobs, but still, this is regression
that we want to fix.

We now bail out if !lastWindowClosed() in QGuiApplication's
canQuitAutomatically, which is triggered from QEventLoopLocker's
isQuitLockEnabled() behavior. And we do so regardless of whether
quitOnLastWindowClosed is set or not, as the latter property
determines the behavior when closing a window, not the behavior
when a QEventLoopLocker goes out of scope.

Similarly, we now block quitting of the application when triggered
by quitOnLastWindowClosed() if a QEventLoop is active, regardless of
the isQuitLockEnabled(), as the latter property is determining
whether we should trigger a quit, not whether we should block them.

[ChangeLog][Important behavior changes] Fixed a regression where
the last QEventLoopLocker going out of scope would quit the app,
even if there were open windows, if quitOnLastWindowClosed was
false.

[ChangeLog][Important behavior changes] Fixed a regression where
closing the last window would quit the app, even if there were
active QEventLoopLockers, if isQuitLockEnabled was false.

Fixes: QTBUG-124386
Pick-to: 6.7 6.5
Change-Id: I84fd0ddea78a2f417f3a17b326113c880079cf85
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 37 insertions, 5 deletions

diff --git a/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp b/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp
index 6b8700f580..d1a50e3d69 100644
--- a/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp
+++ b/tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp
@@ -1004,8 +1004,8 @@ void tst_QGuiApplication::quitOnLastWindowClosedWithEventLoopLocker()
     });
 
     {
-        // Disabling QEventLoopLocker support should not affect
-        // quitting when last window is closed.
+        // Disabling QEventLoopLocker automatic quit should not affect
+        // quitting when last window is closed if there are no lockers.
         app.setQuitLockEnabled(false);
 
         QuitSpy quitSpy;
@@ -1019,8 +1019,40 @@ void tst_QGuiApplication::quitOnLastWindowClosedWithEventLoopLocker()
     }
 
     {
-        // Disabling quitOnLastWindowClosed support should not affect
-        // quitting when last QEventLoopLocker goes out of scope.
+        // Disabling QEventLoopLocker automatic quit should still block
+        // quitting when last window is closed if there is a locker alive.
+        app.setQuitLockEnabled(false);
+
+        QScopedPointer<QEventLoopLocker> locker(new QEventLoopLocker);
+
+        QuitSpy quitSpy;
+        QWindow window;
+        window.show();
+        QVERIFY(QTest::qWaitForWindowExposed(&window));
+        QTimer::singleShot(0, &window, &QWindow::close);
+        QTimer::singleShot(200, &app, []{ QCoreApplication::exit(0); });
+        app.exec();
+        QCOMPARE(quitSpy.quits, 0);
+    }
+
+    {
+        // Disabling quitOnLastWindowClosed automatic quit should not affect
+        // quitting when last QEventLoopLocker goes out of scope if
+        // there are no windows.
+        app.setQuitLockEnabled(true);
+        app.setQuitOnLastWindowClosed(false);
+
+        QuitSpy quitSpy;
+        QScopedPointer<QEventLoopLocker> locker(new QEventLoopLocker);
+        QTimer::singleShot(0, [&]{ locker.reset(nullptr); });
+        QTimer::singleShot(200, &app, []{ QCoreApplication::exit(0); });
+        app.exec();
+        QCOMPARE(quitSpy.quits, 1);
+    }
+
+    {
+        // Disabling quitOnLastWindowClosed automatic quit should still block
+        // quitting via QEventLoopLocker if there's a window alive.
         app.setQuitLockEnabled(true);
         app.setQuitOnLastWindowClosed(false);
 
@@ -1032,7 +1064,7 @@ void tst_QGuiApplication::quitOnLastWindowClosedWithEventLoopLocker()
         QTimer::singleShot(0, [&]{ locker.reset(nullptr); });
         QTimer::singleShot(200, &app, []{ QCoreApplication::exit(0); });
         app.exec();
-        QCOMPARE(quitSpy.quits, 1);
+        QCOMPARE(quitSpy.quits, 0);
     }
 
     {