CurlrObject - Curl RTE detection

Once you've taken the trouble to write a Curl applet, there's a good chance you'll want to include it in a web page; at that point you'll need some way to detect the Curl RTE and check its version on different platforms and browsers.

If you've ever included a Flash movie on a page this will be a familiar issue to you. The question of how best to embed the Flash plugin has a long history - the various browsers have made plugin detection notoriously awkward, but over the years a standard practice of sorts, has developed to the point where you can find numerous helpful scripts, and Adobe now provide a Flash Player Detection kit along with guidelines for detection.

Unfortunately, Curl doesn't provide an equivalent script for doing this so you've been on your own - until now, that is. I've written some Javascript that will do the job for you, based on the best example I could find for Flash - SWFObject script developed by Geoff Stearns. In the spirit of the original, I've called it CurlrObject, and it is a Javascript-only detection, avoiding the use of VBasic on PCs. As an added bonus, I've included in the script a way of specifying parameters for the applet - to answer another frequently asked question.

If you're in a hurry you can view the code and you can download it from the Code page. Read on for usage notes.

CurlrObject is surprisingly easy to use. Just include the script file in your web page, add a couple of lines of Javascript and identify a HTML element to contain the Curl applet. For example:

<script type="text/javascript" src="curlrobject_source.js"></script> ... <div id="curlrcontent"> <bold>You need v5.0 of Curl to run this application.</bold> </div> <script language ="JavaScript"> var co = new CurlrObject("sampleCurlrObject.curl", "curlrcontent", "100%", "100%", "5.0"); co.write("curlrcontent"); </script>

The parameters for CurlrObject are:

parameter	Description
appletUrl	The location of the Curl applet to be run.
width	The width of the Curl applet
height	The height of the Curl applet
version	The required version of the Curl RTE
id	(optional) The id to be used for the embed tag.
redirectUrl	(optional) The location for the RTE install. Defaults to http://www.curl.com/download/index.php.

Like the SWFObject the net result of successful detection is to place and populate an <embed> node into the target element. In other respects CurlrObject has behavior that is a little different from SWFObject; in particular if the script cannot find the Curl RTE it writes a message to the target HTML element that includes a link to the Curl download page - or to the redirectUrl. Other diiferences are: the id parameter is optional, and no detectkey is specifiable.

One reason you may want to use a different redirectUrl from the default arises when require an older version of the RTE than is current - these are found at a different location on the Curl web site.

If the browser has disabled the RTE a different message will be written - but I haven't yet found a way to distinguish between these two situations in IE.

If you're familiar with Javascript, then you will probably feel comfortable customizing the functions getINSTALLCURLHTML and getDISABLEDCURLHTML to change the message or the behavior of the script when the RTE is not found.

Specifying parameters for the Curl applet.

You can use the CurlrObject to specify startup parameters for the applet; e.g.

<script language ="JavaScript"> var co = new CurlrObject("hello.curl", "curlrcontent", "100%", "100%", "5.0"); co.addVariable("testvar1", "value 1"); co.addVariable("testvar2", "value 2"); co.addVariable("testvar3", "value 3"); co.write("curlrcontent"); </script>

This builds a query args list and attaches it to the applet Url. To extract the name value pairs in your Curl applet you'll need code like this procedure, which constructs an Arguments object from the applet's query arguments.

{define-proc public {get-query-args query-url:Url}:Arguments || the returned arguments let ret-args:Arguments = {Arguments} || A read/write buffer for the query string - including the "?" let query-str:StringBuf = {StringBuf query-url.query} {if query-str.size <= 0 then {return ret-args}} || remove the '?' {query-str.remove 0} || split at the '&' let nv-pairs:StringArray = {query-str.split split-chars="&"} || build the argument list {for nv in nv-pairs do || nv has the form name = value - split at the '=' let pair:StringArray = {nv.split split-chars="="} || add name and value to the argument list {ret-args.append {pair[1].trim-clone}, keyword = {url-decode-string {pair[0].trim-clone} } } } || return the result {return ret-args} }

To see it in action you can run the sample page with three Curl applets requiring different RTE versions. (You don't have to install all the versions if you don't want to).

I've done some basic testing - but I'm not at all sure if the case of the RTE installed but not enabled works on all browsers - it doesn't in IE. If you use it and find problems or have improvements to suggest, let me know.