[Javascript] writing/reading the same file at the same time

Tue May 25 10:32:12 CDT 2004

Hi H and Flavio,

I was looking for something like what H suggested, but flavio's simpler solution is good enough for now.  
copying the file was a lot faster than creating it, and therefore the flickering is now reduced to almost none.

Later on I'll comeback to the problem and try H's solution.  And of course I'll let you all know :)

tks to both,
Günther.

"[JavaScript List]" <javascript at LaTech.edu> schrieb am 25.05.04 16:25:58:
> 
> Simply setting the src of a Image()-object does not halt the execution 
> and wait for the image to be loaded. I suggest you set an event handler 
> or onreadystate-handler on your image, and then do the swapping when 
> you're sure the image is fully downloaded.
> 
> If I recall correctly, oImage.onload works in Mozilla, and 
> oImage.onreadystatechange works in Internet Explorer. oImage.readyState 
> should be '4' when it's done loading in Explorer.
> 
> Could we see your webcam when you're done? ;)
> 
> Regards,
> H
> 
> Günther Mittermayer wrote:
> > Hi there, 
> > 
> > I have an application, where the JavaScript refreshes an Image contained in a HTML page.
> > 
> > Since this image is continuously generated by a Perl script, I get a random blinking of the image, that I am assuming to be due to the times when both (the Javascript and the Perl script) try to access the image at the same time.
> > 
> > anyone got an Idea on how to solve that?  I tried "preloading" the image, but nope.. doesn't work.
> > 
> > It is not very critical if I miss some refreshes, that is, if the Javascript tries reading the file when it is in use, it is ok not to do anything, and wait for the next loop....  
> > does JavaScript handle exceptions?? how does that work, with try/catches just like in Java?
> > 
> > any help/ comments are welcome,
> > Günther.
> > 
> > here is some code:
> > 
> > <html>
> > <head>
> > 
> > <meta http-equiv="cache-control" content="no-cache">
> > <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
> > <meta name="description" content="Fireworks Splice HTML">
> > 
> > <script type="text/javascript">
> > function refresh_image()
> > {
> > 
> > <!-- Preloads the Image to a temporary variable to avoid blinking - Nice try.. but not working-->
> > img_tmp = new Image();
> > img_tmp.src = "theimage.png";
> > 
> > <!-- Refreshes the image -->
> > var img = document.getElementById('imageID');
> > img.src = img_tmp.src;
> > setTimeout('refresh_image()',600)
> > };
> > 
> > </script>
> > </head>
> > <body onLoad="setTimeout('refresh_image()',600)">
> > <form method='POST' action='/cgi-bin/elem_props.cgi' target='elem_props'>
> > 	<center><input type='image' name='image1' id='imageID' src='theimage.png'></center>
> > </form>
> > </body>
> > </html>
> > 
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