tst_qhooks: test that it's possible to chain multiple hooks together

Chaining hooks together was mentioned by Ossi in the comments of
d953d9a4. This patch justs add a test that verifies that it works, and
also serves as an informal example for developers looking how to do it.

Change-Id: I53a014d5663c289ea0559e0926ed301f4e5110e6
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: hjk <hjk@qt.io>

1 files changed, 70 insertions, 0 deletions

diff --git a/tests/auto/corelib/global/qhooks/tst_qhooks.cpp b/tests/auto/corelib/global/qhooks/tst_qhooks.cpp
index f0685d64c5..5fa7566e86 100644
--- a/tests/auto/corelib/global/qhooks/tst_qhooks.cpp
+++ b/tests/auto/corelib/global/qhooks/tst_qhooks.cpp
@@ -35,10 +35,18 @@ class tst_QHooks: public QObject
     Q_OBJECT
 
 private slots:
+    void cleanup();
     void testVersion();
     void testAddRemoveObject();
+    void testChaining();
 };
 
+void tst_QHooks::cleanup()
+{
+    qtHookData[QHooks::AddQObject] = 0;
+    qtHookData[QHooks::RemoveQObject] = 0;
+}
+
 void tst_QHooks::testVersion()
 {
     QVERIFY(qtHookData[QHooks::HookDataVersion] >= 3);
@@ -73,5 +81,67 @@ void tst_QHooks::testAddRemoveObject()
     QCOMPARE(objectCount, 0);
 }
 
+static QVector<QString> hookOrder;
+
+static QHooks::AddQObjectCallback existingAddHook = 0;
+static QHooks::RemoveQObjectCallback existingRemoveHook = 0;
+
+static void firstAddHook(QObject *)
+{
+    hookOrder.append(QLatin1String("firstAddHook"));
+}
+
+static void firstRemoveHook(QObject *)
+{
+    hookOrder.append(QLatin1String("firstRemoveHook"));
+}
+
+static void secondAddHook(QObject *object)
+{
+    if (existingAddHook)
+        existingAddHook(object);
+
+    hookOrder.append(QLatin1String("secondAddHook"));
+}
+
+static void secondRemoveHook(QObject *object)
+{
+    if (existingRemoveHook)
+        existingRemoveHook(object);
+
+    hookOrder.append(QLatin1String("secondRemoveHook"));
+}
+
+// Tests that it's possible to "chain" hooks together (i.e. have multiple hooks)
+void tst_QHooks::testChaining()
+{
+    QCOMPARE(qtHookData[QHooks::AddQObject], (quintptr)0);
+    QCOMPARE(qtHookData[QHooks::RemoveQObject], (quintptr)0);
+
+    // Set the add and remove hooks (could just skip this and go straight to the next step,
+    // but it's for illustrative purposes).
+    qtHookData[QHooks::AddQObject] = (quintptr)&firstAddHook;
+    qtHookData[QHooks::RemoveQObject] = (quintptr)&firstRemoveHook;
+
+    // Store them so that we can call them later.
+    existingAddHook = reinterpret_cast<QHooks::AddQObjectCallback>(qtHookData[QHooks::AddQObject]);
+    existingRemoveHook = reinterpret_cast<QHooks::RemoveQObjectCallback>(qtHookData[QHooks::RemoveQObject]);
+
+    // Overide them with hooks that call them first.
+    qtHookData[QHooks::AddQObject] = (quintptr)&secondAddHook;
+    qtHookData[QHooks::RemoveQObject] = (quintptr)&secondRemoveHook;
+
+    QObject *obj = new QObject;
+    QCOMPARE(hookOrder.size(), 2);
+    QCOMPARE(hookOrder.at(0), QLatin1String("firstAddHook"));
+    QCOMPARE(hookOrder.at(1), QLatin1String("secondAddHook"));
+    delete obj;
+    QCOMPARE(hookOrder.size(), 4);
+    QCOMPARE(hookOrder.at(2), QLatin1String("firstRemoveHook"));
+    QCOMPARE(hookOrder.at(3), QLatin1String("secondRemoveHook"));
+
+    hookOrder.clear();
+}
+
 QTEST_APPLESS_MAIN(tst_QHooks)
 #include "tst_qhooks.moc"