QTestLib: Disable App Nap on macOS

App Nap may cause stalls or timer delays during test runs.

Change-Id: I828282d12127918439a9a2a4f7d7be6cac457b42
Task-number: QTBUG-61499
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/testlib/qtestcase.cpp

@@ -1728,6 +1728,9 @@ void QTest::qInit(QObject *testObject, int argc, char **argv)
 
     // Don't restore saved window state for auto tests.
     QTestPrivate::disableWindowRestore();
+
+    // Disable App Nap which may cause tests to stall.
+    QTestPrivate::AppNapDisabler appNapDisabler;
 #endif
 
 #if defined(Q_OS_MACX)

src/testlib/qtestutil_macos.mm

@@ -54,6 +54,33 @@ namespace QTestPrivate {
     void disableWindowRestore() {
         [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"ApplePersistenceIgnoreState"];
     }
+
+    /*! \internal
+        \class AppNapDisabler
+        \brief Disables App Nap by registereing a bacground activity.
+
+        App Nap remains disabled as long as the AppNapDisabler instance
+        exists.
+    */
+
+    /*! \internal
+        Creates an AppNapDisabler instance and starts a NSActivityBackground activity.
+    */
+    AppNapDisabler::AppNapDisabler()
+    {
+        m_activity = [[NSProcessInfo processInfo] beginActivityWithOptions:NSActivityBackground
+                                                                    reason:@"Qt Auto Test"];
+        [m_activity retain];
+    }
+
+    /*! \internal
+        Destroys the AppNapDisabler instance and ends the NSActivityBackground activity.
+    */
+    AppNapDisabler::~AppNapDisabler()
+    {
+        [[NSProcessInfo processInfo] endActivity:m_activity];
+        [m_activity release];
+    }
 }
 
 QT_END_NAMESPACE

src/testlib/qtestutil_macos_p.h

@@ -58,6 +58,17 @@ QT_BEGIN_NAMESPACE
 
 namespace QTestPrivate {
     void disableWindowRestore();
+
+    class AppNapDisabler
+    {
+    public:
+        AppNapDisabler();
+        ~AppNapDisabler();
+        AppNapDisabler(const AppNapDisabler&) = delete;
+        AppNapDisabler& operator=(const AppNapDisabler&) = delete;
+    private:
+        id m_activity;
+    };
 }
 
 QT_END_NAMESPACE