kfink@jarthur.Claremont.EDU (Kevin Fink) (12/15/89)
My brother still hasn't gotten what he wants. Here is another message from him. --------------------------------------------------------------------------- In a previous posting, I said I still couldn't get smooth scrolling to work and I gave several sample programs to show how the screen flickers even when a character-shift is not taking place. Judging by the responses I have received, it seems I did not make myself clear. I wrote an ML program using double-buffering. However, the program listings I gave in the previous letter did not contain any sort of buffering. This was intentional. [ed. note. There's no way in hell I'm going to type in a long ML program, even if he sends me one. Do I look like a secretary?] The first BASIC program I listed only manipulates the VIC-II chip. If everything works correctly, this should scroll the screen down one bit at a time, then jump up seven bits and scroll dows again. The whole row of characters is never shifted. This should not produce any flicker because it is using the internal VIC-II chip register and nothing else. However, it does. The flickering is not just at the transistion where the screen moves seven bits; it happens at, as far as I can tell, any or all of the one-bit transitions. Maybe I am missing something, but it seems to me that the whole point of double-buffering was to eliminate the flicker produced by the transition of whole row (or column) of characters to either direction. This would not eliminate the flicker caused by the normal one-bit transitions, since there is no reason to switch screens between these. My question is what causes the one-bit transition flicker and how can I get around it? --------------------------------------------------------------------------- Thanks for all your help. Kevin Fink