40.3 Console Types and Device Classes

Every device is of a particular type, which describes how the connection to that device is made and how the device operates, and a particular class, which describes other characteristics of the device (currently, the color capabilities of the device).

The currently-defined device types are

x

A connection to an X display (such as ‘willow:0’).

tty

A connection to a tty (such as ‘/dev/ttyp3’).

stream

A stdio connection. This describes a device for which input and output is only possible in a stream-like fashion, such as when SXEmacs in running in batch mode. The very first device created by SXEmacs is a terminal device and is used to print out messages of various sorts (for example, the help message when you use the ‘-help’ command-line option).

The currently-defined device classes are

color

A color device.

grayscale

A grayscale device (a device that can display multiple shades of gray, but no colour).

mono

A device that can only display two colours (e.g. black and white).

Function: device-type &optional device

This function returns the type of device. This is a symbol whose name is one of the device types mentioned above. device defaults to the selected device.

Function: device-or-frame-type device-or-frame

This function returns the type of device-or-frame.

Function: device-class &optional device

This function returns the class (color behavior) of device. This is a symbol whose name is one of the device classes mentioned above.

Function: valid-device-type-p device-type

This function returns whether device-type (which should be a symbol) specifies a valid device type.

Function: valid-device-class-p device-class

This function returns whether device-class (which should be a symbol) specifies a valid device class.

Variable: terminal-device

This variable holds the initial terminal device object, which represents SXEmacs’s stdout.