
	DropShadow 					Copyright James Mackraz, 1987
	Version 2, Revision 0						April 7, 1987

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	Notes for source release					May 2, 1987

	This program and all or any part of the source cannot be
	distributed for profit.  Inclusion on not-for-profit disk
	collections is permitted.  The program may not be modified
	to omit or modify the title in the control window.

	Notice that this program still has holes from the early
	versions. For one thing, it assues that layers activity
	always happens on the workbench, and will recalculate
	the shadow.  Another, is that it doesn't take any care to
	be sure that no other program has pre-empted the layer vectors
	that it steals.  So in the words of Sidekick: load me last.

	Also, the option to make the shadows move with the hour
	and the season (after you configure virtual north) has
	not been implemented.
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	Notes for Version 2, Revision 0 			April 7, 1987

	Added the following from the wish list:

	-A slider gadget is implemented to adjust the 3-dimensional
	distance between the planes of the windows.

	-A slider gadget is implemented to adjust shadow darkness.  If
	desired, full independent control of the shadow colors is
	possible.

	I had some problems with the latter, so I now increase the
	task priority while the darkness slider is selected.  It
	has not been tested thoroughly. (May 2: haven't heard any
	complaints yet.)

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	Notes for Version 1, Revision 1				March 12,1987

	When Windows are moved, created, sized, deleted, or depth-
	arranged, Intuition calls layers.library.  This program
	intercepts those calls to determine that the shadow needs
	to be recalculated.  Before this version, this recalculating
	and redrawing was done before Intuition got a chance to
	redraw Window borders and Gadgets.

	This version of DropShadow performs the work on its schedule,
	and is only signaled by the code which intercepts the
	layers calls.  This makes for a smoother and less dangerous
	implementation.
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	Notes for Version 1, Revision 0				March 1, 1987


	The program on this disk creates and maintains multi-level
	transparent drop shadows of windows on the Workbench screen.

	The program creates its own window, and is terminated by closing
	that window.  The program, named DropShadow, may be run from
	the CLI, or if associated with an icon, from the Workbench.

	The shadows are created by attaching an additional bitplane to
	the Workbench's display bit map, but doing so in a way which
	is transparent to the Workbench or its application programs.

	Unfortunately, this third bitplane brings the Workbench screen
	to a point which causes processor cycles to be stolen by the
	display generation hardware.  Thus, this program is probably
	best used only for demos and having fun, at least for users
	without "Fast" RAM.

	Enhancements which are planned include:

	-The program detects that the shadow image needs to be
	recalculated by monitoring the layers library.  That section
	of code should check that the layers activity is in fact in
	the Workbench screen.

	-A way to detect color changes in preferences would allow the
	shadow colors to track user changes to the Workbench colors.
	In the meantime, the program must be restarted to initialize the
	shadow colors.  Commodities Exchange can be used for this.

	-A technique of unknown type is planned for user control of
	the light source which casts shadows.  Shadows cast according
	to the position of the sun (time of day and season) are possible
	but unlikely.

	-This program is not yet a safe Library vector stealer.  It should
	refuse to exit if some other program has displaced its vectors,
	lest that other program call DropShadow after it has exited.


								Jim Mackraz
								4021 Second St.
								Palo Alto, CA 94306

