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Index › Programming Questions & Help › Programs › scrolling machine
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scrolling machine (Read 729 times)
gregniemeyer
scrolling machine
Nov 14th, 2007, 8:25am  
Dear Discourse,

I am trying to get an elegant scrolling mechanism going with the pixels[] array. Trouble is there always seems to be one line (the first one) look still. How can this be avoided?
The scrolling action I have is here:

 loadPixels();
 for (int w = 0; w < (width*height); w = w+width ){
   arraycopy(pixels, w, scoot, 0, scoot.length);
   arraycopy(scoot, 0, pixels, max(0,w-1), scoot.length);
 }
 updatePixels();


Thanks, Greg
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antiplastik
Re: scrolling machine
Reply #1 - Nov 16th, 2007, 10:07am  
Hi Greg! I finally found a solution...

The problem is, your first line can't be moved to the left since max(0, w-1) returns 0. At each time step, the very first pixel of each line you want to scroll has to be moved at the end of the line.

This may be more explicit with a schema, but here is the code :

Code:
loadPixels();
for (int w = 0; w < (width*height); w += width ){
  // pixels : ABCDEF
  arraycopy(pixels, w+1, scoot, 0, scoot.length-1);
  // scoot  : BCDEF_
  scoot[scoot.length-1] = pixels[w];
  // scoot  : BCDEFA
  arraycopy(scoot, 0, pixels, w, scoot.length);
  // pixels : BCDEFA
  }
updatePixels();
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