Wt  4.0.2
Public Member Functions | List of all members
Wt::EventSignal< E > Class Template Reference

A signal that conveys user-interface events. More...

#include <Wt/WSignal.h>

Inheritance diagram for Wt::EventSignal< E >:
Inheritance graph
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Public Member Functions

virtual bool isConnected () const override
 Returns whether the signal is connected.
 
template<class F >
Wt::Signals::connection connect (const F &function)
 Connects to a function. More...
 
template<class T , class V >
Wt::Signals::connection connect (T *target, void(V::*method)())
 Connects a slot that takes no arguments. More...
 
template<class T , class V >
Wt::Signals::connection connect (T *target, void(V::*method)(E))
 Connects a slot that takes one argument. More...
 
template<class T , class V >
Wt::Signals::connection connect (T *target, void(V::*method)(const E &))
 Connects a slot that takes a 'const argument&'. More...
 
void connect (const std::string &function)
 Connects a JavaScript function. More...
 
void connect (JSlot &slot)
 Connects a slot that is specified as JavaScript only. More...
 
void emit (E e=NoClass::none) const
 Emits the signal. More...
 
void operator() (E e) const
 Emits the signal. More...
 
virtual Wt::Signals::connection connect (WObject *target, WObject::Method method) override
 Connects to a slot. More...
 
- Public Member Functions inherited from Wt::EventSignalBase
const char * name () const
 Returns the event name. More...
 
void disconnect (JSlot &slot)
 Disconnects a JSlot.
 
void preventDefaultAction (bool prevent=true)
 Prevents the default browser action. More...
 
bool defaultActionPrevented () const
 Returns whether the default browser action is prevented. More...
 
void preventPropagation (bool prevent=true)
 Prevents event propagation. More...
 
bool propagationPrevented () const
 Returns whether event propagation is prevented. More...
 
- Public Member Functions inherited from Wt::SignalBase
template<class T , class V >
Wt::Signals::connection connect (T *target, void(V::*method)())
 Connects to a slot. More...
 

Detailed Description

template<typename E = NoClass>
class Wt::EventSignal< E >

A signal that conveys user-interface events.

An EventSignal is a special Signal that may be triggered by user interface events such as a mouse click, key press, or focus change. They are made available through the library in widgets like WInteractWidget, and should not be instantiated directly.

In addition to the behaviour of Signal, they are capable of both executing client-side and server-side slot code. They may learn JavaScript from C++ code, through stateless slot learning, when connected to a slot that has a stateless implementation, using WObject::implementStateless(). Or they may be connected to a JSlot which provides manual JavaScript code.

The typically relay UI event details, using event details objects like WKeyEvent or WMouseEvent.

See also
Signal, JSignal

Member Function Documentation

template<typename E >
template<class F >
Wt::Signals::connection Wt::EventSignal< E >::connect ( const F function)

Connects to a function.

This variant of the overloaded connect() method supports a template function object (which supports operator ()).

When the receiver function is an object method, the signal will automatically be disconnected when the object is deleted, as long as the object inherits from WObject (or Wt::Signals::trackable).

template<typename E >
template<class T , class V >
Wt::Signals::connection Wt::EventSignal< E >::connect ( T target,
void(V::*)()  method 
)

Connects a slot that takes no arguments.

If a stateless implementation is specified for the slot, then the visual behaviour will be learned in terms of JavaScript, and will be cached on the client side for instant feed-back, in addition running the slot on the server.

The slot is as a method of an object target of class T, which equals class V, or is a base class of class V. In addition, to check for stateless implementations, class T must be also be a descendant of WObject. Thus, the following statement must return a non-null pointer:

WObject *o = dynamic_cast<WObject *>(dynamic_cast<V *>(target));
template<typename E >
template<class T , class V >
Wt::Signals::connection Wt::EventSignal< E >::connect ( T target,
void(V::*)(E method 
)

Connects a slot that takes one argument.

This is only possible for signals that take at least one argument.

template<typename E >
template<class T , class V >
Wt::Signals::connection Wt::EventSignal< E >::connect ( T target,
void(V::*)(const E &)  method 
)

Connects a slot that takes a 'const argument&'.

This is only possible for signals that take at least one argument.

template<typename E >
void Wt::EventSignal< E >::connect ( const std::string &  function)

Connects a JavaScript function.

This will provide a client-side connection between the event and a JavaScript function. The argument must be a JavaScript function which optionally accepts two arguments (object and the event):

function(object, event) {
...
}

Unlike a JSlot, there is no automatic connection management: the connection cannot be removed. If you need automatic connection management, you should use connect(JSlot&) instead.

template<typename E >
void Wt::EventSignal< E >::connect ( JSlot slot)

Connects a slot that is specified as JavaScript only.

This will provide a client-side connection between the event and some JavaScript code as implemented by the slot. Unlike other connects, this does not cause the event to propagated to the application, and thus the state changes caused by the JavaScript slot are not tracked client-side.

The connection is tracked, taking into account the life-time of the JSlot object, and can be updated by modifying the slot. If you do not need connection management (e.g. because the slot has the same life-time as the signal), then you can use connect(const std::string&) instead.

template<typename E >
Wt::Signals::connection Wt::EventSignal< E >::connect ( WObject target,
WObject::Method  method 
)
overridevirtual

Connects to a slot.

Every signal can be connected to a slot which does not take any arguments (and may thus ignore signal arguments).

Implements Wt::SignalBase.

template<typename E >
void Wt::EventSignal< E >::emit ( E  e = NoClass::none) const

Emits the signal.

This will cause all connected slots to be triggered, with the given argument.

template<typename E >
void Wt::EventSignal< E >::operator() ( E  e) const

Emits the signal.

This is equivalent to emit().

See also
emit()

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