20.7. Responding to User Actions
Problem
You want to do something when a user clicks a button, chooses an item from a dropdown list, or otherwise interacts with a GUI widget.
Solution
Write a
callback function and then associate
the callback function with a signal using the connect( )
method:
// create the window $window = &new GtkWindow(); // create a button with the current time as its label $button = &new GtkButton(strftime('%c')); // set the update_time() function as the callback for the "clicked" signal $button->connect('clicked','update_time'); function update_time($b) { // the button's text is in a child of the button - a label widget $b_label = $b->child; // set the label text to the current time $b_label->set_text(strftime('%c')); } // add the button to the window $window->add($button); // display the window $window->show_all(); // necessary so that the program exits properly function shutdown() { gtk::main_quit(); } $window->connect('destroy','shutdown'); // start GTK's signal handling loop gtk::main();
Discussion
The code in the Solution displays a window with a button in it. On
the button is the time, rendered by
strftime('%c')
. When the button is clicked, its label
is updated with the current time.
The update_time( )
function is called each time the button
is clicked because
$button->connect('clicked','update_time')
makes
update_time( )
the callback function associated
with the button’s clicked
signal. The first argument to the callback function is the widget whose ...
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