[erlang-questions] how: ot: real time web pages?

Jani Launonen <>
Sun Dec 2 16:07:31 CET 2007


Jouni Rynö kirjoitti 2.12.2007 kello 9.25:

>
> I start from what I would like to have:
> A web page with a real time updated display of numerical values and
> graphs. Think about typical process displays in industry,
> temperatures, voltages and some graphs showing parameter history.
> Maybe some graphical layout of hardware, to show how each parameter
> is connected to each other.
>
> To achieve that, I would need a  web page template format, where I  
> can:
> - define named text fields, which shall be updated
> - define named graphics, which can be updated
> - and some code to generate the real page and connection functions
> for (comet style?) communication with the page and erlang process
> feeding the data

I did year or two ago a test where I made some SVG components to show  
some measurements in real-time. The SVG graph was updated by  
javascript which used httprequest to php enable Apache.

The SVG komponents were composed to one web page by running XML  
configuration file through XSLT transformation, which picked correct  
SVG fragments from different files. It worked satisfactorily, but I  
didn't had the time to make any nice way to automatically connect the  
graphs by lines (like factory conveyer belts) and I don't know if it  
could have been done automatically (off line) by XSLT transformation  
or should I've used javascript for that.

In fact, I'm thinking again the same system --- this time using  
Erlang in server end. So if you come up with some nice solution,  
please report it to the list :)

>
> Currently I have all that implemented as Tcl/Tk canvas (thanks to Ola
> Samuelsson and ewish, which was distributed with Erlang back in 97 or
> so?)
>
> As my understanding of "javascript" is practically zero, I would like
> get a hint on how to do this. Googling shows a lot of options, most
> of the systems not quite being there. Should it be simply javascript
> and svg, changes updated via attributes. Or canvas tag (complicated
> with text fields?) Or haxe and flash (for which I did not find
> examples, how the update mechanism would work) Or something else?
>
> Is this doable? Some examples existing already?

Perhaps there could some working SVG component libraries in web? I  
tried to search for such, but could find quite such that I was  
looking for.

Jani

>
> Jouni
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