script.aculo.us Please help with this javascript slideshow bug

[lisali]

Hi,

In the slide show code below, there's a function to press "previous" and "next" links. The "next" one works fine, and if you keep pressing it, it cycles through all the slides.

The "previous" one is a bit messed up, for some reason - it will go back a slide or two but then it will just go blank!

Could you please help?
Thank you!

<script type="text/javascript">
        start_slideshow(1, 3, 3000);

        var currentSlide = 1;

        function start_slideshow(start_frame, end_frame, delay) {
            id = setTimeout(switch_slides(start_frame,start_frame,end_frame, delay), delay);
        }

        function switch_slides(frame, start_frame, end_frame, delay) {
            
            return (function() {
                             
                Effect.Fade('slide' + frame, { duration: 1.0 });
                
                if (frame == end_frame) {
                    frame = start_frame; 
                    currentSlide = frame;
                } else {
                    frame = frame + 1; 
                    currentSlide = frame;
                }
                
                Effect.Appear('slide' + frame, { duration: 1.0 });
                
                if (delay == 1000) {
                    delay = 3000; 
                }
                
                id = setTimeout(switch_slides(frame, start_frame, end_frame, delay), delay);
            })
        }

        function stop_slideshow() {
            clearTimeout(id);
        }
        
        function next_slide() {
            
            clearTimeout(id);

            Effect.Fade('slide' + currentSlide, { duration: 1.0 });
            
            if (currentSlide == 4) {
                currentSlide = 0;
            }
            
            currentSlide = currentSlide + 1;
            Effect.Appear('slide' + currentSlide, { duration: 1.0 });
            id = setTimeout(switch_slides(currentSlide, currentSlide, currentSlide, delay), delay);
        }
        
        function previous_slide() {
            
            clearTimeout(id);
            
            if (currentSlide == 0) {
                currentSlide = 1;
            } else {
              Effect.Fade('slide' + currentSlide, { duration: 1.0 });
              
              currentSlide = currentSlide - 1;
              Effect.Appear('slide' + currentSlide, { duration: 1.0 });
              id = setTimeout(switch_slides(currentSlide, currentSlide, currentSlide, delay), delay);
            }
        }
        
    </script>

The previous/next links are like this:

<a href="#" onclick="next_slide()">Next</a>
<a href="#" onclick="previous_slide()">Previous</a>