If one needed to listen to a signal just once, one had to
store the QMetaObject::Connection object returned by connect()
and use it to disconnect the slot after the first signal
activation.
This has led to a proliferation of using wrappers (and enough
TMP); they usually look like this:
1) create a shared_ptr<QMO::Connection>, allocating its payload;
2) create a lambda, capturing the shared_ptr by value;
3) in the lambda, disconnect the connection (through the shared_ptr),
and call the actual slot;
4) connect the signal to the lambda, storing the returned
QMO::Connection into the shared_ptr.
This is expensive, error prone for newcomers, and tricky to
support as a general facility inside one's projects.
We can do better, just support single shot connections right
in QObject.
[ChangeLog][QtCore][QObject] Added the Qt::SingleShotConnection
flag. When a connection is established with this flag set,
the slot is going to be activated at most once; when the signal
is emitted, the connection gets automatically broken by Qt.
Change-Id: I5f5feeae7f76c9c3d6323d841efba81c8f98ce7e
Fixes: QTBUG-44219
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
11b8c46d2a