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>Toggle Buttons

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>Toggle Buttons

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>Toggle buttons are derived from normal buttons and are very similar,

except they will always be in one of two states, alternated by a

click. They may be depressed, and when you click again, they will pop

back up. Click again, and they will pop back down.

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>Toggle buttons are the basis for check buttons and radio buttons, as

such, many of the calls used for toggle buttons are inherited by radio

and check buttons. I will point these out when we come to them.

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>Creating a new toggle button:

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>GtkWidget *gtk_toggle_button_new( void );

GtkWidget *gtk_toggle_button_new_with_label( const gchar *label );

GtkWidget *gtk_toggle_button_new_with_mnemonic( const gchar *label );

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>As you can imagine, these work identically to the normal button widget

calls. The first creates a blank toggle button, and the last two, a

button with a label widget already packed into it. The _mnemonic() variant

additionally parses the label for '_'-prefixed mnemonic characters.

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>To retrieve the state of the toggle widget, including radio and check

buttons, we use a construct as shown in our example below. This tests

the state of the toggle button, by accessing the 

CLASS="LITERAL"

>active

> field of the

toggle widget's structure, after first using the

CLASS="LITERAL"

>GTK_TOGGLE_BUTTON

> macro to cast the widget pointer into a toggle

widget pointer. The signal of interest to us emitted by toggle

buttons (the toggle button, check button, and radio button widgets) is

the "toggled" signal. To check the state of these buttons, set up a

signal handler to catch the toggled signal, and access the structure

to determine its state. The callback will look something like:

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>void toggle_button_callback (GtkWidget *widget, gpointer data)

{

    if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (widget))) 

    {

        /* If control reaches here, the toggle button is down */

    } else {

        /* If control reaches here, the toggle button is up */

    }

}

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>To force the state of a toggle button, and its children, the radio and

check buttons, use this function:

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>void gtk_toggle_button_set_active( GtkToggleButton *toggle_button,

                                   gboolean        is_active );

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>The above call can be used to set the state of the toggle button, and

its children the radio and check buttons. Passing in your created

button as the first argument, and a TRUE or FALSE for the second state

argument to specify whether it should be down (depressed) or up

(released). Default is up, or FALSE.

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>Note that when you use the gtk_toggle_button_set_active() function, and

the state is actually changed, it causes the "clicked" and "toggled"

signals to be emitted from the button.

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>gboolean gtk_toggle_button_get_active	(GtkToggleButton *toggle_button);

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>This returns the current state of the toggle button as a boolean

TRUE/FALSE value.

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