Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!gergle.UUCP!greg
From: greg@gergle.UUCP
Newsgroups: comp.windows.news
Subject: Re:  Freezing canvases
Message-ID: <8806111733.AA08238@parallax.parallax.com>
Date: 11 Jun 88 23:43:53 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 20


>Is there any way of "freezing" a canvas so that output does not appear on the
>screen until the canvas is "unfrozen" ?. This is rather like the /Mapped field
>except that a frozen canvas does not vanish from the screen. 

>Why should I want such a facility ?. Well, it is often better to freeze a
>window before outputing a complex picture/diagram and then unfreeze it, so that
>the picture appears all at once. Watching a diagram form piece by piece on the
>screen seems to draw attention to the performance (or lack of it) of the NeWS
>server.

There is only one way I know of to achieve this affect in NeWS.

Create an unmapped canvas the same size as your ClientCanvas.
Always draw into this canvas.
When you want to update the display, imagecanvas from the unmapped canvas to
your ClientCanvas. Make sure that the scale is correctly set when you 
imagecanvas.  If should  be WidthOfClientCanvas HeightOfClientCanvas scale.


	-greg.