Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!gem.mps.ohio-state.edu!sunybcs!sybil.cs.Buffalo.EDU!gbbrooks
From: gbbrooks@sybil.cs.Buffalo.EDU (G. Brandon Brooks)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Fast Scrolling
Message-ID: <13939@eerie.acsu.Buffalo.EDU>
Date: 29 Nov 89 21:17:23 GMT
Sender: nobody@acsu.buffalo.edu
Reply-To: gbbrooks@sybil.cs.buffalo.edu (G. Brandon Brooks)
Organization: SUNY/Buffalo Computer Science
Lines: 49

Newsgroups: comp.sys.amiga.tech
Subject: Re: Fast Scrolling
Summary: 
Expires: 
References: <762@milton.acs.washington.edu> <6072@ucdavis.ucdavis.edu>
Sender: 
Reply-To: gbbrooks@sybil.cs.Buffalo.EDU.UUCP (G. Brandon Brooks)
Followup-To: 
Distribution: 
Organization: SUNY/Buffalo Computer Science
Keywords: scrolling,spam

In article <6072@ucdavis.ucdavis.edu> rogers@iris.ucdavis.edu (Brewski Rogers) writes:
>In article <762@milton.acs.washington.edu> zeno@milton.acs.washington.edu (Sean Lamont) writes:
>>
>>I am trying to do horizontal smooth scrolling.  I have tried two methods,
>>one using SCROLLRASTPORT and one using SCROLLVPORT.
>>
>>Problems I want to solve:
>>
>>1)  I can't GET SCROLLVPORT to work at all!!! I gave it the VPORT record    
>>    of my screen, but it did nothing.  I've tried this in several
>>vport environments. 
>>
>>2) It's TOO SLOW!  A SCROLLRASTPORT takes far too much time to scroll
>>anything of any substance. (like a 400 x 200 5-plane bitmap) I know
>>it's possible to move bitmaps much faster (for example, Screen sizing)
>>How would one go about making a FAST scroll?
>>
>
>Basically, there are NO fast intuition routines to scroll your
>screens View. This may be connected to the fact that most screens
>can be dragged up and down the screen...
>

	I use Benchmark Modula-2, and to scroll a view, all I do is:

ViewPort.DxOffset := 10;
ViewPort.DyOffset := 5;
ScrollVPort(ViewPort);

	This moves a view IMMEDIATELY 10 pixels to the right, and 5 pixels
down; effextively making (10,5) the origin of the screen (0,0).
	In "C"Just change the syntax, and I think it'll work. Just changing
the DxOffsets and DyOffsets doesn't do any good - I assume that is what you
were doing - The computer must be TOLD that you did this. A ScrollVPort()
command will do the job.

		-Good Luck, Brandon!