GtkVolumeButton — A button which pops up a volume control
GtkVolumeButton is a subclass of GtkScaleButton that has
been tailored for use as a volume control widget with suitable
icons, tooltips and accessible labels.
typedef struct _GtkVolumeButton GtkVolumeButton;
GtkWidget* gtk_volume_button_new (void);
Creates a GtkVolumeButton, with a range between 0.0 and 1.0, with
a stepping of 0.02. Volume values can be obtained and modified using
the functions from GtkScaleButton.