[Chameleon] A new set of Chameleon widgets

[Mike Leahy]

Hello list,

I have been working on a set of custom widgets for Chameleon over the
past couple weeks that some users may be interested in trying.  I've
made a file and detailed description available at
http://gaia.uwaterloo.ca/mgl/.  The zip file that can be downloaded
contains all the widgets I have worked on for a project I am currently
participating in.  Also included is a sample that should allow you to
test them, and some basic setup instructions in a README.txt.  To view a
live demo, you can look at http://gaia.uwaterloo.ca/mgl/resizetest2/.
You should find the map works relatively well without reloading the page
in the browser, and that it will resize to fill the browser window after
it is resized.

This work is in part a follow-up to the posts I made a couple weeks
ago regarding enabling an AJAX-based chameleon interface.  I had been
able to make a simple Chameleon application function without reloading
the page directly in the browser, but instead loading it through an
XMLHttpRequest object in JavaScript, and updating appropriate content in
the page.  After doing so, I found that I had trouble when I got to the
stage of making elements inside the page more dynamic (i.e., resizing
the map widget - which for unclear reasons wouldn't display beyond its
original extent).

The best/only suggestion that I received regarding that problem was to
rewrite the MapDHTML widget so that operations such as clipping the
image while panning took place by simply displaying the image inside a
div layer with overflow:hidden specified in the style.  I have now done
this, but rather than attempting to reverse-engineer the original
MapDHTML widget's functionality, I found it simpler to start a new one
essentially from scratch. As a result, I had to also rework many other
widgets that are required for basic interaction with the map.  The
results (as you can see in the demo above) seem to work fairly well so
far.  There may be more widgets to come as we continue working on the
tool we're developing, but I think what I've finished so far will
provide a good start for any users interested in developing Chameleon
applications that does not require reloading the page. There are also
some fixes/enhancements to tools like the circle or polygon ROIs, which
I noticed didn't seem to draw properly in the default versions (is this
a known issue?).

I hope everybody feels free to try out these widgets, and I look forward
to any comments or feedback.

Mike