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Demos Amiga Demoscene Archive Forum / Coding / Various subroutines calls during VBL interrupt : how to ?


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HM Kaiser
#1 - Posted: 20 Mar 2012 10:20
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Hi !
I have a question about VBL interrupt, and demo effects subroutines. Let's explain that:

Let's say the VBL interrupt handles, for instance, a starfield and a scrolltext, which are permanent.
In the intro, the first effect does not need VBL for timing.

But for another effect, I need to do more things during the VBL interrupt. And when this effect is finished, these things of course don't need to run any longer.
-> how do I call this additionnal stuff ? I thought about a "flag" tested in the VBL interrupt routine, and jump (or not) to the additionnal stuff given the result of this flag ?
-> or should I do another VBL interrupt, with additional code / jumps to sub routines ?

What are the good practices ?
#2 - Posted: 20 Mar 2012 12:35
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put the addresses of the subroutines in a list and update the contents of the list based on where you are in the demo mayhaps? then you just jump to any subroutine sequentially through the list until you reach the end of the list (use a zero or similar for termination).
HM Kaiser
#3 - Posted: 20 Mar 2012 21:38
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Implemented this technique in my code. I like this way to do, thanks :-)
#4 - Posted: 21 Mar 2012 17:10
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I second bstrr. It also proofed handy to have some macro to register a function for execution in the next VBL, i.e. fill the list.


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