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From: pvf@bridge2.UUCP
Newsgroups: net.micro.atari16
Subject: Re: Logbase/Physbase and Screen Dumps
Message-ID: <176@bridge2.UUCP>
Date: Tue, 22-Apr-86 18:04:33 EDT
Article-I.D.: bridge2.176
Posted: Tue Apr 22 18:04:33 1986
Date-Received: Fri, 2-May-86 23:11:46 EDT
References: <157@bridge2.UUCP> <860421-105316-1612@Xerox>
Organization: Bridge Communications, Inc., Mountain View, Ca
Lines: 52

> 
> 
> >I believe that the screen dump routine should be using the
> >physbase pointer, as all I have read implies that the screen
> >dump capability should give you a printout of what is visible
> >on the actual screen
> 
> >Have I found a bug?  Is there any way to fix it?
> 
> 	No. You haven't found a bug. If you think about the reasoning behind
> having two locations "logbase" and "physbase" you will see that it is
> working properly. The ideas is to allow the programmer to perform page
> flipping while using the system routines for writing to the screen. In
> order for this to work you must display one screen but have the system
> routines use another. Thus, there are two pointer, one points to the
> memory which is to be displayed on the screen (physbase) the other to
> the memory which is to be used by the system routines (logbase). If you
> want the system routines to work on the currently displayed memeory then
> you must set "logbase" to "physbase". If you started having system
> routine use physbase then you would loose flexability (Printing one
> screen while viewing another for example). To solve your problem simply
> set "logbase" to "physbase" before calling the screen dump routine and
> restore it after you return.
> 	
> 	
> John 

You COMPLETELY missed the point of the question.  I KNOW how logbase
and physbase work.  My program uses them and the result is that I get
nice crisp screen transitions despite the fact that the program needs
several seconds to prepare the next image.  OK, now back to the question.

Let me clarify, I did not issue a system call to print the screen.  The
manual says that I can hit ALT/HELP (or whatever the key combo is as per
the documentation) to get hardcopy OF THE SCREEN.  I hit ALT/HELP and
DID NOT GET HARD COPY OF THE SCREEN.  I got hard copy of the image that
was partially built.  Had I issued the call, you can be sure that I would
have had the pointers pointing at what I wanted them to point at.

I AM suggesting that the ALT/HELP routine use physbase instead of logbase.
I suppose this implies that the screen dump system should take a parameter
indicating the area of memory to be printed, while the parameter passed in
the case of the ALT/HELP key be physbase.

he use of a the keyboard to get screen dumps is to take care of the 
case where the program does not have the capability or desire to provide
the function itself.  Instead, it printed the confusing half-built 
image that the program was preparing.

I am trying to point out to ATARI that the capability could be made to
operate in a more useful fashion.
Perhaps someone from ATARI would care to comment.