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From: cmcmanis@sun.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: DropShadow
Message-ID: <17734@sun.uucp>
Date: Thu, 30-Apr-87 14:28:43 EDT
Article-I.D.: sun.17734
Posted: Thu Apr 30 14:28:43 1987
Date-Received: Sat, 2-May-87 01:29:03 EDT
References: <1555@solar.STANFORD.EDU>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 30
Summary: Thats a Jim Mackraz goody

In article <1555@solar.STANFORD.EDU>, (Stuart Ferguson) writes:
> While people are discussing Workbench enhancements/improvements, why not
> include _DropShadow_* as part of the environment? 

Because it slows things down a bit? 
 
> By the way, does anyone know how that program works?  Specifically: it
> must add another bitplane to the Workbench screen but how does it do it?
> Does it append the bitplane to the existing ones or does it allocate a
> whole new screen and point the Workbench at it?
> 	Stuart		shf@solar.Stanford.EDU

Jim Mackraz wrote it but kept the source secret. However he had published
his dualpf program slightly earlier and the techniques seem to be similar.
You can allocate another bitplane for the Workbench screen using AllocRaster
and plugging the pointer into the bp->Planes[2] entry. Then set the 4
upper color registers to 'darker' versions of the workbench colors, diddle
the screen pointers to make it believe it is a 3 bitplane screen, and
voila whenever you draw a 1 bit in the new plane the user sees a shadow.
Of course that is the easy part, now you have to SetFunction() the Layers
library to let you know when the windows may have changed and update their
shadows. And you have to calculate the 'altitude' of the various windows
and figure out how to adjust the shadows etc. 


-- 
--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These views are my own and no one elses. They could be yours too, just
call MrgCop() and then ReThinkDisplay()!