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libcamera: base: signal: Support connecting signals to functors

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It can be useful to connect a signal to a functor, and in particular a
lambda function, while still operating in the context of a receiver
object (to support both object-based disconnection and queued
connections to Object instances).

Add a BoundMethodFunctor class to bind a functor, and a corresponding
Signal::connect() function. There is no corresponding disconnect()
function, as a lambda passed to connect() can't be later passed to
disconnect(). Disconnection typically uses disconnect(T *object), which
will cover the vast majority of use cases.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
This commit is contained in:
Laurent Pinchart
2021-08-27 04:05:33 +03:00
parent c4e2b00d51
commit 58720e1dc9
5 changed files with 114 additions and 0 deletions
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24
src/libcamera/base/signal.cpp
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@@ -121,6 +121,30 @@ SignalBase::SlotList SignalBase::slots()
* \context This function is \threadsafe.
*/
/**
* \fn Signal::connect(T *object, Func func)
* \brief Connect the signal to a function object slot
* \param[in] object The slot object pointer
* \param[in] func The function object
*
* If the typename T inherits from Object, the signal will be automatically
* disconnected from the \a func slot of \a object when \a object is destroyed.
* Otherwise the caller shall disconnect signals manually before destroying \a
* object.
*
* The function object is typically a lambda function, but may be any object
* that satisfies the FunctionObject named requirements. The types of the
* function object arguments shall match the types of the signal arguments.
*
* No matching disconnect() function exist, as it wouldn't be possible to pass
* to a disconnect() function the same lambda that was passed to connect(). The
* connection created by this function can not be removed selectively if the
* signal is connected to multiple slots of the same receiver, but may be
* otherwise be removed using the disconnect(T *object) function.
*
* \context This function is \threadsafe.
*/
/**
* \fn Signal::connect(R (*func)(Args...))
* \brief Connect the signal to a static function slot