Here we define some guidelines for when creating new icons that extend the standardized list of icon names defined here, in order to provide icons for more specific MIME types, devices, or international flags.
Icon names are in the en_US.US_ASCII locale. This means that the allowable characters in the icon names, must fall withing the US-ASCII character set. As a further restriction, all icon names may only contain lowercase letters, numbers, underscore, dash, or period characters. Spaces, colons, slashes, and backslashes are not allowed. Also, icon names must be spelled as they are in the en_US dictionary.
The dash “-” character is used to separate levels of specificity in icon names, for all contexts other than MimeTypes. For instance, we use “input-mouse” as the generic item for all mouse devices, and we use “input-mouse-usb” for a USB mouse device. However, if the more specific item does not exist in the current theme, and does exist in a parent theme, the generic icon from the current theme is preferred, in order to keep consistent style.