PROMPT -- Prompt Boxes


	1) Usage

	| OBJECT pmt[MENU];

	A PROMPT instance has no state, but all information required
	for creating a prompt box is passed to it using arguments.
	There is only one singe method called INPUT. When an INPUT
	message is sent to an instance of PROMPT, a prompt box will be
	displayed on the terminal screen. The terminal will be put into
	raw mode, allowing the user to edit the content of the prompt
	box interactively. When the box is closed, it will not be
	removed from the screen.

	The PROMPT class uses the color set structure described in the
	'common data structures' section.


	2) Methods


	2.1 INPUT

	| PMT.INPUT(x, y, lx, max, cs, buffer, xkeys)
	| ! Num,Num,Num,Num,Bvec,Bvec,Vec => Key|-1

	PMT.INPUT creates a one-line editing box with a length of LX
	characters at the ccorinates (X,Y) on the terminal screen. It
	prints the last LX characters of BUFFER in this window. If the
	length of the string in BUFFER is less than LX, it prints it
	left-justified and fills the rest of the window with blanks.
	The MAX argument specifies the maximum length of the string in
	BUFFER. BUFFER must provide space for MAX characters. The MAX
	value includes the terminating NUL character, so only up to
	MAX-1 characters may be entered. The XKEYS argument is a vector
	of 'exit keys', where the first member of the vector holds the
	number of keys contained in it. Pressing one of the keys
	defined in this vector causes the INPUT method to exit.

	MAX may be larger than or equal to LX. If MAX is greater than
	LX, INPUT will side-scroll the text if necessary.

	After painting the window, the terminal is put into raw mode
	and PMT.INPUT lets the user edit the content of string
	interactively. Keys used for editing are listed in the
	following section.

	PMT.INPUT uses a so-called 'smart default'. It is indicated by
	initially displaying the text of BUFFER using C_SELECT color.
	When the first key pressed by the user is not a navigation key,
	the key pressed replaces the entire string. When a navigation
	key is pressed, the color changes to C_TEXT and the text can be
	edited normally.

	PMT.INPUT returns the key last pressed.

	A special return value of -1 indicates that the specified
	length LX is too long (>128 characters).


	2.2 Editing Keys

	The following keys may be used for editing text in prompt boxes
	(^X denotes [control]+[X], K_X denotes ttyctl.K_X):

	Key		Alt.	Description
	---		----	-----------
	K_LEFT		^P	move to the left one character
	K_RIGHT		^N	move to the right one character
	K_DEL		^D	delete the character on the right
	BACKSPACE	.	delete the character on the left
	^U		.	delete all characters
	K_HOME		^A	move to the first character
	K_END		^E	move behind the last character
	^V		.	insert the character typed next (quote)

	Other characters will be inserted literally, if their ASCII
	codes are below 256.

	When a character contained in the XKEYS set is pressed, the
	method exits immediately, returning the key pressed. XKEYS is
	checked before other bindings. Therefore, including 'X' in the
	exit key set, for example, would make PMT.INPUT exit when an
	uppercase 'X' is typed, rendering the input of capital X
	characters impossible.


	3) Common Data Structures


	3.1 CSET -- Color Sets

	The color set structure CSET, which is implemented in the
	FILEBOX, FORM, MENU, and PROMPT classes, has the following
	members:

	Member		Used for...
	C_BACKGROUND	box backgrounds
	C_FRAME		drawing box frames
	C_TEXT		writing text
	C_SOTEXT	writing higlighted text
	C_SELECT	drawing the selection bar

	For the exact usage of this structure, see the description of
	the classes which use it. The CSET structure has the same
	layout in all classes. Therefore, one and the same color set
	may be used in file boxes, forms, menues, and prompt boxes.


	3.2 FSET -- Frame Character Sets

	The frame character set structure FSET, which is implemented in
	the FILEBOX, FORM, and MENU classes, has the following members:

	F_UL	upper left corner
	F_UR	upper right corner
	F_LL	lower left corner
	F_LR	lower right corner
	F_HL	horizontal lines
	F_VL	vertical lines

	NOTICE: FSET is a packed structure. To define one, use

	var fs::FSET;

	and to access its members, use fs::F_UL, fs::F_UR, etc.

	EXAMPLE: Using the FSET structure PACKED"1234-|" would result
	in a box of the form

	| 1----------2
	| |          |
	| |          |
	| 3----------4

	The FSET structure has the same layout in all classes.
	Therefore, one and the same frame character set may be used in
	file boxes, forms, and menues.