Programming a scroller

Programming a scroller

As you already know how to write to the statusbar and how the setTimeout- function works the scroller will be easy for you to understand. In the online version you have the possibility to watch this scroller code in work. Have a look at the script:

Here goes your cool page!

This script uses the same functions (or parts of it) we already used above. The setTimeout(...) 'tells' the timer to call the scroll() function when the time is up. The scroller will move one step further. At the beginning there are a lot of calculations but these are not too important for understanding how the script works. The calculations are there for getting the position where the scroller ought to start. If it is just at the start the script has to add some spaces in order to place the text right.

I told you at the beginning of this part of my introduction that scrollers are not very popular or if they are still popular they won't be it very long anymore. There are some reasons. I list several here but there are certainly more. If you see this effect for the first time it might be quite nice but looking at it the 1 million and second time it is not that fun anymore. Well, this is no good argument indeed because this affects nearly every cool trick used in your pages. There are more severe problems. What I don't like is that it changes the speed when you move the mouse (It gets faster!). At least it does that for me. This effect gets a lot stronger when you want to make the scroller little bit faster by changing the setTimeout- value. Maybe there is a way around this problem. But the worst is that if you let this script run some time you get an Out of memory error. And this is really ugly. It seems to be a problem of the Netscape Navigator 2.0. Maybe a higher version will have this bug fixed.

There are many other routines out there on the Net. I've seen some scrollers writing the text to a frame. Programming this shouldn't be too difficult with the techniques described in this tutorial.

Last changed: 11.May'96

©1996 by Stefan Koch