ANIMATION AND SCANLINES

[paul.parkhurst@uttsbbs.uucp (Paul Parkhurst)]

-> Does anybody out there have the code to detect where the current
-> scanline on the GS screen is at so I could draw an image to the
-> screen without scanline flicker. Currently, the C/asm code I have
-> waits until a vertical blank before it draws to the screen, but that
-> slows it down.

   What you can do is set the scanline interrupt bit for a particular
line (usually, a line after what it is you want to draw).  When you hit
the interrupt, draw what needs to be drawn.  Since the interrupt occured
on the line after what you are drawing, you should have plenty of time
to update the upper part of the screen before its redrawn.

   I did this in a long-lost project of mine and it worked fine.  No
flicker in the animation at all.

Paul Parkhurst

paul.parkhurst@uttsbbs.UUCP
                                                                                                            
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