Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!mcsun!hp4nl!media01!pkr
From: pkr@media01.UUCP (Peter Kriens)
Newsgroups: comp.lang.smalltalk
Subject: Re: optimising redraws of graphic panes in  ST/V 286
Message-ID: <2038@media01.UUCP>
Date: 18 Feb 91 21:08:39 GMT
References: <1991Feb8.102528.10392@runx.oz.au> <3201.27b6a2ea@iccgcc.decnet.ab.com>
Reply-To: pkr@media01.UUCP (Peter Kriens)
Organization: aQute, Netherlands
Lines: 46

> Dear netland,
>
> I've got a graphics application written in Smalltalk V/286. One
> problem with it is that the screen redraws are a slow. I've
> got a display of a X-Y plot with lots of  lines/ text labels on it.
> I've tried various ways to speed up the redraws. The manuals isn't exactly
> helpful and so I include below a sample listing and ask the following
> questions...
>
> - would you expect that writing to a virtual form, then copying
>   this to the display, would speed up the redraw? If yes, then
>   how is this done? I've tried every variant I can think of on
>   setting drawLine's pen's dest/sourceForm to Display/form etc.,
>   etc.
> - any other ideas on how to speed up the redraws on the following
>   sample system?
>
> There must be a way. The standard Smalltalk window redraws are
> FASTTTT. What am I doing wrong?

Unfortunately I did not see the original listing, only a reply. I could
give you a few tips for speeding up general graphics. maybe you can use them.

	Only draw the parts that are needed. Clip the area which
	you know that is not changed. 

	Draw on a bitmap and bitblit the resulting form on a redraw
	message. A lot of people dont know how the MVC mechanism should
	be used. Make a form of the largest size you are going
	to be using. Use this as a drawing area that is kept up
	to date. If you make changes that need to be shown on the
	screen say "self changed: #xxxx" where xxxx is the name
	of the graphpane. The message xxxx should then just return
	you form.

	If you have objects you show on the screen with text and
	graphics in it, use a form to represent these so that you
	don't have to rebuild this each time you redraw the screen.

	Buy a faster machine.

If you want, you can send me your code and I can inspect it to see what
is going on.

Peter Kriens
pkr@media01.uucp