[Mod_gzip] MSIE download component + gzip bug

Sat, 19 Oct 2002 13:14:51 +0200

Hi all,

I've been experiencing trouble with mod_gzip in combination with IE6 and
the Microsoft proprietary downloader component that is included with IE
since 5.0.

Background: The component allows you to download a text file from the
server with HTTP and return it to Javascript with a callback function. I
use this functionality to create new layers and load them with content on
the fly. Here is the example from MSDN (first hit for "startDownload" on
google):

  <HTML XMLNS:MSIE >
  <MSIE:DOWNLOAD ID="oDownload" STYLE="behavior:url(#default#download)" />
  <SCRIPT>
    function onDownloadDone(s) { alert (s); }
  </SCRIPT>
  <P>Click <A HREF="javascript:oDownload.startDownload('download.htm',
                    onDownloadDone)">here</A> to download this page.

In recent IE6 versions this component seems to have problems with gzip
content-encoding. Installing mod_gzip 1.3.26 on Apache 1.3.27 rendered the
downloader broken for IE6 visitors: for some downloaded files, the
component just never invokes the callback, as if the server did not return
a response. When I set "mod_gzip_on No" in the affected VirtualHost and
restart Apache, the component works without any problem.

The component exhibits this behavior on the following versions:

    6.0.2600.0000
    6.0.2800.1106.xpsp1.020828-1920

Unfortunately I do not have older versions available for testing.
It is not really a huge issue since the IE downloader component is fairly
"underground" and not standardized, although I don't know if the failure
might be a telltale for any other gzip content-encoding troubles in IE6.

My workaround was to add a new extension in Apache (.htmlx, .phpx) with
appropriate types/handlers and exclude those extension from mod_gzip
compression; then I made sure to only download .htmlx, .phpx pages with
this component.

If mod_gzip developers or anybody else are interested in some testcase
files or know how I should submit this to Microsoft let me know. For now
this message is just a "heads up" for anybody using the component with
mod_gzip on the server side.

cheers,
Walter (satisfied mod_gzip user)