The eXternal Screen Blanker Library Standard V1.0
		-------------------------------------------------

	      Written by Oliver Wagner, placed in the Public Domain

		Contact: OW@AWORLD.ZER
			 ow@aworld.zer.sub.org

1. Purpose
----------
XSB  is  a  defined standard for fancy screen blankers.  It allows the easy
implementation  of  blanking  effects  without  worrying  about the blanker
commodity  itself.   Also,  it allows sharing a screen blanking effect with
several different blankers supporting the XSB standard.

A  simple  screen  blanking  commodity  --  XSBCX  --  is  included  in the
distribution package.

If  you  think that is complete nonsense, usefull and a waste-of-time, then
you maybe correct.

2. Credits
----------
Credits go to Christoph Teuber, Sandro Paolini and Holger Lubitz who helped
to work out the original idea.

3. Implementation
-----------------
A  XSB  library simply consists of three entry points.  The library will be
loaded  by  the blanking commodity, and will be run on the commodity's task
schedule.

The entry points are:



	void XSBBlankScreen(long sigmask,struct XSBInfo *xsi) (-30 XSBBase)
				D0		A0

	The main blanking entry point. The XSB commodity will call this
	routine when it is time to blank the screen.

	"sigmask" is a exec signal bit (already converted to a mask)
	which is used by the commodity system to signal that the
	blanking effect should quit and restore the original screen
	display. You can do a "Wait(sigmask)" or so to find out when the
	user is doing input again.

	"xsi" is a structure created by the calling commodity for your
	convinience. The structure is defined as

	 struct XSBInfo {
	  struct timerequest *tr;
	  struct XSBPref *prefs;
	 };

	"tr" is a pointer to a ready-to-use timerequest (UNIT_VBLANK),
	opened by the calling commodity. Use it to delay your actions.

		NEVER DO A BUSY LOOP INSIDE YOUR BLANKING EFFECT!

	"prefs" is a pointer to an array of XSBPref structures, loaded
	from the file "ENV:XSB/<blankername>.XSBP". The contents of
	the XSBPref structures are defined by you. If no prefs file
	was found, "prefs" will be NULL. See the XSBGetParams() call
	for more information on XSB preferences.



	char *XSBGetID(void) (-36 XSBBase)
	 D0

	This call simply returns a string giving information about
	the blanking effect created by the library. It will be display
	by the calling commodity upon the user's request, normally
	by the EasyRequest() or a similar function. That means that
	you can include "\n"s in the text as line delimiters.


	struct XSBParams *XSBGetParams(void) (-42 XSBBase)
	 D0

	This call returns a linked list of XSBParams structures, or
	NULL if the blanking library doesn't support preferences.

	The structure is defined as:

	 struct XSBParams {
	  struct XSBParams *next;
	  long type; /* see defines below */
	  char *text; /* text label for gadgets */
	  char **labels; /* optional labels for cycle gadgets */
	  long min,max; /* optional min/max values for sliders */
	  struct XSBPref *value; /* value entry */
	 };

	Upon the user's request, the calling commodity will build a
	preference requester with the items described by the 
	XSBParams structures. The user than may manipulate the items,
	save or cancel the changes. Overflow checking must be done
	by the library. A maximum of 10 preference items are supported.
	The XSBPref structures should belong to the libraries private
	data space and should be initialized at loading time.

	See the provided include file, "xsb.h", and the provided
	example library for more information about using the XSB
	preference system.