21.3.7 Using Custom ParametersThis is NOT the latest copy of this book; click here for the latest version.
When you are connecting signals to functions, it is possible to add one or more custom parameters to the signal handler. As seen earlier, connect_object() can be used to pass a particular widget into a function, however an alternative is to use connect() with extra parameters for the information you wish to use inside the function.
So, connect() could have been called like this:
$window->connect('button-press-event', 'show_popup', $menu);
The handler function would then need to have accepted three parameters - the event, the GtkWindow object that emitted the signal, and the custom parameter $menu. The only difference here is that behind the scenes a little more data needs to be passed around for the handler function to be called with the extra parameter.
Here is a complete code example you can try out to get the idea:
<?php
function btnClick($button, $window) {
$window->destroy();
gtk::main_quit();
}
$window =& new GtkWindow();
$btnquit =& new GtkButton("Quit");
$btnquit->connect("clicked", "btnClick", $window);
$window->add($btnquit);
$window->show_all();
gtk::main();
?>
As you can see, the parameter $button is not being used inside btnClick(), however that is hardly a major speed hit.
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