set_background_gicon
Description:
Updates the icon to use icon as the base background image.
If icon is null, this will go back using style information or
default theming for its background image.
If this method is called and an icon name was already set as background for the icon, icon will be used, i.e. the last method
called between set_background_gicon and
set_background_icon_name has always priority.
Parameters:
| this | |
| icon |
a Icon, or null |