Sets the icon of the tooltip (which is in front of the text) to be the icon indicated by icon_name with the size indicated by size. If icon_name is null, the image will be hidden.
an icon name, or null
a stock icon size (#GtkIconSize)
Sets the icon of the tooltip (which is in front of the text) to be the icon indicated by icon_name with the size indicated by size. If icon_name is null, the image will be hidden.