A button which pops up a volume control
Class GtkVolumeButton
GtkVolumeButton is a subclass of GtkScaleButton that has been tailored for use as a volume control widget with suitable icons, tooltips and accessible labels.
The constructor 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.