Listing 3. Compute the window dimensions.
  if(width % 4 == 0){
    windowWidth = width;
  }else{
    windowWidth = (width/4)*4 + 4;
  }//end else
  
  if(windowWidth < 108){
    windowWidth = 108;
  }//end if
  
  //Make the height sufficient to contain two copies of
  // the image, one above the other.
  windowHeight = 2 * height;