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.