qconnect: Connect a signal handler

Description Usage Arguments Details Value Author(s) Examples

Description

Like many other GUI toolkits, Qt supports connecting handler functions to signals, which are emitted in response to user actions. The qconnect function connects an R function to a signal on a Qt object.

Usage

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qconnect(x, signal, handler, user.data)

Arguments

x

The Qt object providing the signal

signal

The name of the signal

handler

The R function to handle the signal

user.data

Data to pass to the R function as the last parameter. If omitted, no such argument is passed to the handler.

Details

In Qt, only other QObject instances can listen to a signal, so this function creates a dummy object that invokes the R function upon receipt of the signal.

To disconnect a handler, call the disconnect method on the signal emitter x, passing it the returned dummy QObject; see the example.

Value

A dummy QObject instance that is listening to the signal. Will become invalid when the signal emitter is invalidated.

Author(s)

Michael Lawrence

Examples

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window <- Qt$QWidget()
button <- Qt$QPushButton(window)
listener <- qconnect(button, "pressed", function(x) print("hello world"))
button$disconnect(listener)


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