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Note If the stock item provided to gtk_button_new_from_stock() or any other stock retrieval function

in GTK+ is not found, it will be treated as a mnemonic label. This prevents buttons from being rendered in an unpredictable way.

It is possible for you to define your own stock icons, but this will not be covered until 9, which covers menus and toolbars. An example of a button using the GTK_STOCK_CLOSE stock item can be seen in Figure 4-1.

Figure 4-1. A GTK_STOCK_CLOSE stock item Each stock item can be referred to by its string value or its macro definition. For example, the close stock item used in Listing 4-1 can be referred to as gtk-close or GTK_STOCK_CLOSE. However, the preprocessor directives are merely convenient aliases of the string values, so there is no reason to learn both identifiers.

Tip You should always use the preprocessor directives, because unsupported items will be flagged when you compile the code. If you use the stock item s string, the compiler will not flag the error, and the invalid icon will be displayed.

Listing 4-1. Stock Items (stockitems.c) button = gtk_button_new_from_stock (GTK_STOCK_CLOSE); g_signal_connect_swapped (G_OBJECT (button), "clicked", G_CALLBACK (gtk_widget_destroy), (gpointer) window); There are 98 stock items provided by GTK+ as of the release of 2.10. A list of these items can be viewed in Appendix D. We will use stock items again when covering menus and toolbars in 9. It is important to note that some stock items have been added since the release of GTK+ 2.0, so a few items may not be available to you if you are not running the most current version of GTK+. This is essential to keep in mind when creating new applications. Your users may not have the most current version of GTK+!

The GtkToggleButton widget is a type of GtkButton that holds its active or inactive state after it is clicked. It is shown as pressed down when active. Clicking an active toggle button will cause it to return to its normal state. There are two widgets derived from GtkToggleButton: GtkCheckButton and GtkRadioButton. You can create a new GtkToggleButton with one of three functions. To create an empty toggle button, use gtk_toggle_button_new(). If you want the toggle button to include a label by default, use gtk_toggle_button_new_with_label(). Lastly, GtkToggleButton also supports mnemonic labels with gtk_toggle_button_new_with_mnemonic(). Figure 4-2 shows two GtkToggleButton widgets that were created with two mnemonic labels by calling the gtk_toggle_button_new_with_mnemonic() initializer. The widgets in the screenshot were created with the code in Listing 4-2.

Figure 4-2. Two GtkToggleButton widgets In the example in Listing 4-2, when one toggle button is activated, the other is disabled. The only way to make it sensitive is to deactivate the original toggle button. Listing 4-2. Using Toggle Buttons (togglebuttons.c) #include <gtk/gtk.h> static void button_toggled (GtkToggleButton*, GtkWidget*); int main (int argc, char *argv[]) { GtkWidget *window, *vbox, *toggle1, *toggle2; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_window_set_title (GTK_WINDOW (window), "Toggle Buttons"); gtk_container_set_border_width (GTK_CONTAINER (window), 10); vbox = gtk_vbox_new (TRUE, 5); toggle1 = gtk_toggle_button_new_with_mnemonic ("_Deactivate the other one!"); toggle2 = gtk_toggle_button_new_with_mnemonic ("_No! Deactivate that one!");

g_signal_connect (G_OBJECT (toggle1), "toggled", G_CALLBACK (button_toggled), (gpointer) toggle2); g_signal_connect (G_OBJECT (toggle2), "toggled", G_CALLBACK (button_toggled), (gpointer) toggle1); gtk_box_pack_start_defaults (GTK_BOX (vbox), toggle1); gtk_box_pack_start_defaults (GTK_BOX (vbox), toggle2); gtk_container_add (GTK_CONTAINER (window), vbox); gtk_widget_show_all (window); gtk_main (); return 0; } /* If the toggle button was activated, set the other as disabled. Otherwise, * enable the other toggle button. */ static void button_toggled (GtkToggleButton *toggle, GtkWidget *other_toggle) { if (gtk_toggle_button_get_active (toggle)) gtk_widget_set_sensitive (other_toggle, FALSE); else gtk_widget_set_sensitive (other_toggle, TRUE); } The only signal added by the GtkToggleButton class is toggled, which is emitted when the user activates or deactivates the button. This signal was triggered in Listing 4-2 by one toggle button in order to disable the other. In Listing 4-2, another important piece of information was shown: multiple widgets can use the same callback function. We did not need to create a separate callback function for each toggle button, since each required the same functionality. It is also possible to connect one signal to multiple callback functions, although this is not recommended. Instead, you should just implement the whole functionality in a single callback function.