We have examined a working case history of a ticker being used in a very busy site. We've learned that the design criteria that seemed reasonable in 1999, do not hold up over time and this gives us some cause for concern. We might make similar judgement calls now and still encounter similar problems with browsers because we did not anticipate their behavior. Hopefully, the continuing standards creation and evolution will address those issues and in time they will be less severe. A standards-based approach is probably the safest course.
We have looked at several alternative ways to solve our problems, and have designed a far better ticker. Around the time this book is published, that new ticker (or something similar to it), will be in daily use on the BBC News Online web site.
So, returning to our new design criteria, let's see if we have satisfied our original goals:
It now runs on more platform/browser combinations than it did before.
The code is most definitely simpler and is about half the length it was before.
We now have a really optimum data passing mechanism and it could still be integrated into the workflow of a content management process.
We have added significant style control functionality.
We didn't find a better event control mechanism, but the behavior appears to be stable and doesn't crash.
We have replaced the need for the
APPLETby allowing the user to call an external page of headlines. We could replace that with all of the ticker headlines in place, but that might change the geometry of the page.
DOM standardization does not really help us in solving a problem like this, because DOM is not nearly complete enough to be useful. We really need traversal and range to be implemented, or we have to write filter scripts to eliminate unwanted text nodes from the child node collections.
Created: November 8, 2001
Revised: November 8, 2001