[Chameleon] Hawaii Application

Paul Spencer
Tue, 09 Sep 2003 15:30:48 -0400
Hi Bart,

(note I've removed the mapserver list)

answers/comments in line ...

Bart van den Eijnden wrote:

> Hi Dave,
> thanks for sharing this with us. I use mainly IE 6.0. I am even amazed 
> how much of the functionality works in Opera 7.10, exceot for the 
> zoom-in box (big red panel in map). 

cool.  If I get a chance to try with Opera, I will try to sort this 
out.  It is likely something to do with differences in the javascript 
api implemented in Opera that we are not aware of.

> I do have some questions about it though:
> * How much time does it take an average developer, familiar with 
> Chameleon, to build this kind of site? 

This site took several days, but that was because we were also fixing 
issues with the legend widget at the same time.  If we were doing a 
similar application and all the widgets we needed were working already, 
this would take probably about 1-2 days of template design and graphic 
design, 3 tops.  All the work should be in laying out the page and 
designing graphics.

> * I see the key map, which is unchanged in extent during zoom actions, 
> is refreshed all the time. Is it cached at the serverside or created 
> all the time? 

The keymap is re-drawn on every page refresh.  There are definite 
optimizations that could happen here.  Interestingly, the keymap is 
being rendered by PHP rather than by MapServer to allow for some 
interesting effects such as changing projections.  There is a bug 
registered in MapServer to handle this in the lower level code, however.

> * Is there a way with Chameleon to move layers up and down? This is 
> not so important for your demo with mostly point symbols. 

yes and no.  There are no widgets that accomplish this directly, but 
there is a javascript API (cwcjsapi widget) that provides a javascript 
interface to moving layers around.  There are also some plans for 
promote/demote widgets but we have no project that really needs that yet.

> * Are all the legend images prepared at the server-side, i.e. not 
> generated? 

The images in this case pre-exist as gif files (or png?).  There is an 
option to have MapServer return the key image it would have placed in 
the legend, although there are some issues with that (such as being 
limited to a preset size by the legend object in the map file).

> * Is there a reason why Chameleon does not use frames? Would it 
> require a lot of rebuilding? 

Chameleon will work in frames.  We are currently embedding Chameleon 
functionality into MapLab (well, MapEdit), which is frames-based.

> * What worries me a bit is the performance, is it due to your server 
> environment or due to Chameleon? I see now after testing in Opera that 
> the average download speed I get from your server is only 15-20 KB/s, 
> with lows in the 5 KB/s, and highs in the 40 KB/s. 

Chameleon, or at least the widgets in this application, are a bit 
javascript heavy.  This is by design and was to meet the requirements of 
the contract that built the technical foundation of Chameleon.  It is 
possible to build widgets that do not use javascript at all.  We are 
doing this for some of our clients, and it is pretty snappy in this case.

There are probably many performance enhancements that we could consider 
in the core of Chameleon as well.  These will be undertaken when we have 
an opportunity to do so, right now the focus is on getting the 
functionality all there.

The connection speeds we get locally are quite a bit faster than yours 
(to be expected), it could be just a general internet bandwidth issue 
between you and us?

> * When I use the Quick view dropdown, I sometimes get a Javascript 
> error: invalid syntax, line 690, and then a really big URL which seems 
> to have returns after the coordinates (so I see 
> KEYMAP_EXTENTS_MAXX=-on one line, and the actual X value on the next 
> line of the details panel of the javascript error).
> I sometimes get the same error when selecting layers and updating the 
> map. After this error almost nothing works anymore. I could not 
> generate this error using Opera. 

This was using IE?  I suspect that the form is using the GET method, 
which is generating URLs longer than IE can handle (known IE issue), and 
Opera does not have this limitation.  I will ask the maintain to switch 
the form to POST and let you know.

Cheers and thanks for taking the time to evaluate this so thoroughly.


> Best regards,
> Bart
> On Tue, 09 Sep 2003 13:22:31 -0400, Dave McIlhagga 
> <> wrote:
>> Hi,
>> For anyone interested in seeing a demo of Chameleon 1.1 with 
>> MapServer 4.0 in action, here's our redeveloped Hawaii application.
>> Comments welcome,
>> Dave

Paul Spencer
Applications and Software Development
DM Solutions Group Inc.

This archive was generated by Pipermail.