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1 Devices

A device is an object representing a connection to a particular display device, such as an X display or a tty. Each device has one or more frames in which text can be displayed. For X displays and the like, a frame corresponds to the normal window-system concept of a window. Frames can overlap, be displayed at various locations within the display, be resized, etc. For tty’s, only one frame can be displayed at a time, and it occupies the entire tty display area. However, you can still define multiple frames and switch between them. Their contents are entirely separate from each other. These sorts of frames resemble the “virtual console” capability provided under Linux or the multiple screens provided by the multiplexing program ‘screen’ under Unix.

When you start up XEmacs, an initial device is created to display frames on. This will either be an X device or a tty device, depending on what mode you started XEmacs in (this is determined by the ‘DISPLAY’ environment variable, the ‘-nw’, ‘-t’ and ‘-display’ command-line options, etc.).

You can connect to other devices by creating device objects, as described below. Many functions (for example the frame-creation functions) take an optional device argument specifying which device the function pertains to. If the argument is omitted, it defaults to the selected device (see below).

Function: devicep object

This returns non-nil if object is a device.


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1.1 Basic Device Functions

Function: device-list

This function returns a list of all existing devices.

Function: device-or-frame-p object

This function returns non-nil if object is a device or frame. This function is useful because devices and frames are similar in many respects and many functions can operate on either one.

Function: device-frame-list device

This function returns a list of all frames on device.

Function: frame-device frame

This function returns the device that frame is on.


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1.2 Device Types and 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’).

terminal

A stdio connection. This describes a device for which input and output is only possible in a stream-like fashion, such as when XEmacs in running in batch mode. The very first device created by XEmacs 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 color).

mono

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

Function: device-type device

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

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

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

Function: device-class 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 device-type

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

Function: valid-device-class device-class

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

Variable: terminal-device

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


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1.3 Connecting to a Device

Function: make-device &optional type device-data

This function creates a new device.

The following two functions create devices of specific types and are written in terms of make-device.

Function: make-tty-device &optional tty terminal-type

This function creates a new tty device on tty. This also creates the tty’s first frame. tty should be a string giving the name of a tty device file (e.g. ‘/dev/ttyp3’ under SunOS et al.), as returned by the ‘tty’ command issued from the Unix shell. A value of nil means use the stdin and stdout as passed to XEmacs from the shell. If terminal-type is non-nil, it should be a string specifying the type of the terminal attached to the specified tty. If it is nil, the terminal type will be inferred from the ‘TERM’ environment variable.

Function: make-x-device &optional display argv-list

This function creates a new device connected to display. Optional argument argv-list is a list of strings describing command line options.

Function: delete-device device

This function deletes device, permanently eliminating it from use. This disconnects XEmacs’s connection to the device.

Variable: create-device-hook

This variable, if non-nil, should contain a list of functions, which are called when a device is created.

Variable: delete-device-hook

This variable, if non-nil, should contain a list of functions, which are called when a device is deleted.

Function: device-live-p object

This function returns non-nil if object is a device that has not been deleted.

Function: device-x-display device

This function returns the X display which device is connected to, if device is an X device.


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1.4 The Selected Device

Function: select-device device

This function selects the device device.

Function: selected-device

This function returns the device which is currently active.


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1.5 Device Input

Function: device-baud-rate device

This function returns the output baud rate of device.

Function: device-disable-input device

This function disables input on device device.

Function: device-enable-input device

This function enables input on device device.

Function: device-function-keymap device

This function returns the function key mapping for device.

Function: set-device-baud-rate device rate

This function sets the output baud rate of device to rate.

Function: set-device-function-keymap device keymap

This function sets the function mapping for device to keymap.


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