tst_qapplication: Prevent desktopaware test from deactivating main test

Applications on macOS are automatically activated (put into the foreground),
when launched from the Finder, or via 'open' on the command line. But when
launched from the terminal, e.g. foo.app/Contents/MacOS/foo, the application
will launch in the background (inactive).

In Qt we override this behavior, activating the app even when launched from
the terminal, as a convenience, as long as the application is a GUI application.

Unfortunately this means that when tst_qapplication launches a subprocess that
is a GUI app, it will steal activation from tst_qapplication, which in turn
will break tests that later try to activate a window and check that the window
is then active. The window will not be active until the application is active.

We can work around it by preventing Qt from activating the application, but
ideally we'd find a better solution to this, as we don't want to sprinkle
overrides all over our tests.

Fixes: QTBUG-90699
Pick-to: 6.1 6.0 5.15
Change-Id: If53a86548002b739df0c0a7153d6244924a4a205
Reviewed-by: Morten Johan Sørvig <[email protected]>

tests/auto/widgets/kernel/qapplication/tst_qapplication.cpp

@@ -1525,6 +1525,11 @@ void tst_QApplication::desktopSettingsAware()
 {
 #if QT_CONFIG(process)
     QProcess testProcess;
+#ifdef Q_OS_MACOS
+    QStringList environment = QProcess::systemEnvironment();
+    environment += QLatin1String("QT_MAC_DISABLE_FOREGROUND_APPLICATION_TRANSFORM=1");
+    testProcess.setEnvironment(environment);
+#endif
     testProcess.start("desktopsettingsaware_helper");
     QVERIFY2(testProcess.waitForStarted(),
              qPrintable(QString::fromLatin1("Cannot start 'desktopsettingsaware_helper': %1").arg(testProcess.errorString())));