Re: [MacPerl] QuickDraw and PICT Resources

[ajf@afco.demon.co.uk (Alan Fry)]

Chris <trasgo@netins.net> writes 21 December 1998:

>  Well, I have intentions of trying to lead Dante through Hell, using the
>arrow keys as input.  However!  I'd like to have a background as well.
>As one can infer, every time Dante moves, he leaves images of his
>previous position behind.  To negate this in the past, I've simply
>re-DrawPictured the background.  This is extremely slow.

Offscreen graphics generally solves this kind of problem and it works very
well with MacPerl. You need the updates on Matthias' site for
MacPerl_21May98, QD_19May98 and QDOffscreen_19May98 however.

The procedure set out in IM, in the chapter on Offscreen Graphics, can be
followed pretty much word for word and it is not at all a complicated
business. I have some examples which I would be happy to send to anyone
interested.

It is possible sometimes to put the fixed part of the image in one
offscreen world and draw the changing part in another. Appropriate
transfers between the offscreen worlds and the physical screen (which are
almost instantaneous) can achieve surprisingly fast response times.

Alan Fry



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