Add QTimer::connectTo(), a shorthand way of connecting to timeout()

There are a couple of Qt classes where you almost always use the
same signal, for example QTimer::timeout, QPushButton::clicked,
and QAction::triggered.

Simply doing timer.connectTo([]{}) is much more convenient, less
tedious and even fun.

Not overloading connect() as it would be confusing to see the
receiver as first argument.

And not naming it onTimeout, as that's a popular way of doing it in
other frameworks. People would assume you could use on* with any signal.
If we ever have on* it should be all or nothing.

[ChangeLog][QtCore] Added QTimer::connectTo(), a shorthand way of
connecting to the timeout() signal.

Change-Id: Ida57e5442b13d50972ed585c3ea7be07e3d8e8d2
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
index 2c6d9ea7c0..2d34aceab8 100644
--- a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
+++ b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
@@ -75,6 +75,7 @@ private slots:
 
     void dontBlockEvents();
     void postedEventsShouldNotStarveTimers();
+    void connectTo();
 };
 
 class TimerHelper : public QObject
@@ -1020,5 +1021,31 @@ void tst_QTimer::crossThreadSingleShotToFunctor()
     delete o;
 }
 
+void tst_QTimer::connectTo()
+{
+    QTimer timer;
+    TimerHelper timerHelper;
+    timer.setInterval(0);
+    timer.start();
+
+    auto context = new QObject();
+
+    int count = 0;
+    timer.connectTo([&count] { count++; });
+    QMetaObject::Connection connection = timer.connectTo(context, [&count] { count++; });
+    timer.connectTo(&timerHelper, &TimerHelper::timeout);
+    timer.connectTo(&timer, &QTimer::stop);
+
+
+    QTest::qWait(100);
+    QCOMPARE(count, 2);
+    QCOMPARE(timerHelper.count, 1);
+
+    // Test that connection is bound to context lifetime
+    QVERIFY(connection);
+    delete context;
+    QVERIFY(!connection);
+}
+
 QTEST_MAIN(tst_QTimer)
 #include "tst_qtimer.moc"