Problem
This is in response to Manar's post titled "How to disconnect an event?"
He has set up a button-press-event
, and he would like to switch the signal handler processing the button-press-event depending on some conditions.
In Part 1 we used the methods connect()
and disconnect()
.
In this Part 2, we'll use the methods block()
and unblock()
as shown below:
Solution
- If you need to 'connect', 'disconnect' and 'reconnect' a signal repeatedly such as the case shown in this example, you might want to consider using GObject::block() and GObject::unblock($signal_handler_id) (instead of connect/disconnect) to switch the signal handlers.
- The effect of the above sample code is exactly the same as that of the previous example using connect/disconnect.
Sample Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 40 41 42 43 44 45 46 47 48 49 51 52 53 54 57 58 59 60 61 62 63 64 65 66 67 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 | <?php $window = new GtkWindow(); $window->set_size_request(400, 175); $window->connect_simple('destroy', array('Gtk','main_quit')); $window->add($vbox = new GtkVBox()); // display title $title = new GtkLabel("Switching signal handlers on the fly\n". "Part 2 - using block / unblock"); $title->modify_font(new PangoFontDescription("Times New Roman Italic 10")); $title->modify_fg(Gtk::STATE_NORMAL, GdkColor::parse("#0000ff")); $title->set_size_request(-1, 40); $vbox->pack_start($title, 0); $vbox->pack_start(new GtkLabel(), 0); $label = new GtkLabel('Click on the blue sqaure once. '. 'It will change to green.'); $vbox->pack_start($label, 0); setup_colorbox('#0000ff', 'blue', $vbox); // note 1 $window->show_all(); Gtk::main(); function setup_colorbox($color, $label, $vbox) { $hbox = new GtkHBox(); $hbox->set_size_request(30, 30); $eventbox = new GtkEventBox(); $eventbox->add($hbox); $eventbox->modify_bg(Gtk::STATE_NORMAL, GdkColor::parse($color)); global $signal_id1, $signal_id2; $signal_id1 = $eventbox->connect('button-press-event', 'on_button_press1'); // note 2 $signal_id2 = $eventbox->connect('button-press-event', 'on_button_press2'); // note 2 $eventbox->block($signal_id2); // note 3 $hbox = new GtkHBox(); $vbox->pack_start($hbox, 0); $hbox->pack_start(new GtkLabel()); $hbox->pack_start($eventbox, 0); $hbox->pack_start(new GtkLabel()); } function on_button_press1($eventbox, $event) { if ($event->type!=Gdk::BUTTON_PRESS) return false; echo "on_button_press1!\n"; $eventbox->modify_bg(Gtk::STATE_NORMAL, GdkColor::parse('#00ff00')); global $signal_id1, $signal_id2; $eventbox->block($signal_id1); // note 4 $eventbox->unblock($signal_id2); // note 4 global $label; $label->set_text('Click on this again. It will change to yellow.'); return true; } function on_button_press2($eventbox, $event) { if ($event->type!=Gdk::BUTTON_PRESS) return false; echo "on_button_press2!\n"; $eventbox->modify_bg(Gtk::STATE_NORMAL, GdkColor::parse('#ffff00')); global $signal_id1, $signal_id2; $eventbox->block($signal_id2); // note 5 $eventbox->unblock($signal_id1); // note 5 global $label; $label->set_text('Click on this again. It will change to green.'); return true; } ?> |
Output
As shown above.
Explanation
We make use of the code from How to switch signal handlers on the fly - Part 1 - using connect disconnect?
What's new here:
- Set up the blue color box.
- Set up the
button-press-event
signal. Note that here we register two callback functions on the same button. Don't forget to take note of the signal handler id's. - Block the second callback function so that only the first one is active.
- Block the first callback function and unblock the second callback function.
- Block the second callback function and unblock the first callback function.
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