Xref: utzoo comp.sys.mac.programmer:4043 comp.sys.mac:25462
Path: utzoo!attcan!uunet!munnari!basser!usage!grants
From: grants@usage.csd.unsw.oz (Grant Sayer)
Newsgroups: aus.mac,comp.sys.mac.programmer,comp.sys.mac
Subject: Fast image changes
Keywords: Vertical Retrace Queue, Color QuickDraw
Message-ID: <243@usage.csd.unsw.oz>
Date: 23 Jan 89 01:05:38 GMT
Organization: Computing Services Dept, UNSW, Australia
Lines: 10


 	I am trying to draw two images one on an offscreen pixelmap and then
quickly swap the images, testing if a subject can detect the colour changes.
The problem is that with the vertical retrace the subject will see part of the
scan line which interrupts the picture.  Does the method of placing the code which swaps the images, basically a copybits operation, into the VBL task queue seem a viable solution.  If this is the casethen is it true that Turbo Pascal failsto allow procedures to be passed using the @ operator on the procedure name thereby preventing installation of the drawing procedure into VBInstall

	Any comments or suggestions would be appreciated

Thanks in advance
Grant Sayer (grants%usage.csd.unsw.oz@munnari.oz)