Stuart Brady wrote: > I haven't written one yet... I imagine that it'd be good > practice, and maybe I could learn something in the process.
Certainly. I think it's the thing most demo coders start with :) > Does this sound like a sensible approach for pixel-by-pixel > scrolling? [snip] I don't think many people bother with pixel-by-pixel: certainly (as far as I remember) my scrollies always moved a byte at a time. Pixel-by-pixel is really slow, even at 50fps: remember most people read at about what, 10 words a second? If your text is going by at (50/5/5 = 2) words (given an average of 5 chars per word, 5 pixels per char) per second, that's going to be -really- dull. The buffering is worthwhile if you're likely to have anything else going on in the same screen area which could corrupt the scrolled area (like starfields etc) but otherwise you might as well just write directly to the screen and scroll the whole thing with LDIR (or LDI unrolled, if you prefer... or stack copying, if you're -really- short of t-states!). The alternative is to write optimised scrolling code for -each letter-. That's a bit complex, but basically you keep track of where each letter is on the screen, and you work out what you need to change to shift that letter one position. For example, if it's a "!" you only need to move about 1/5th of the bytes you would in a generalised scrolling routine (assuming it's a fixed-font, of course). > I suppose changing the video page between scanlines would > work? Whatever for?? But yes, it does. Geoff ________________________________________________________________________ This email has been scanned for all viruses by the MessageLabs SkyScan service. For more information on a proactive anti-virus service working around the clock, around the globe, visit http://www.messagelabs.com ________________________________________________________________________
