SVGZ doesn't have the good encoding

The mime-type of the attachment is set at upload time, using the mime-type that the uploading browser claims the file to be when POSTing.

So the problem is that the browser that uploaded it is setting the wrong mime-type, and Launchpad is then faithfully serving it as the mime-type it was told to.

So I don't think this is a Launchpad bug (although perhaps it would be useful for the person uploading the attachment to be able to override the mime-type that a browser auto-detects?).

(Btw, an encoding of "gzip" would be wrong here: the file itself is gzipped, as indicated by the "z" in "svgz". So its not just a transfer encoding, it's the actual content of the file. It would be wrong to tell the receiving browser that the file extension is "svgz", but then tell it to ungzip the contents before saving them, which is what your proposed Apache directives would do.)

Actually, we are using Zope's zope.app.content_types.guess_content_type() function here, and it returns "image/svg+xml" for such a file.

There are probably two parts here:

1. get proper Content-Encoding support in the librarian. We have a bug for this but I don't recall its ID.

2. Work out some way to mark .svgz and similar files with "Content-Encoding: gzip".

Same difficulties trying to use SVGZ images with Zope3.

There's no easy way to set the header "Content-Encoding: gzip" for a file object which is gzipped.

See bug #174204 for a proposed solution.
IMHO this solution may apply to the "zope.app.file.interfaces.IFile" too.
We already use the "contentType" attribute.
Let's add a "contentEncoding" optional attribute.

https://bugs.edge.launchpad.net/launchpad-foundations/+bug/174204 is the librarian feature request

The zope.contenttype project on Launchpad has been archived at the request of the Zope developers (see https://answers.launchpad.net/launchpad/+question/683589 and https://answers.launchpad.net/launchpad/+question/685285). If this bug is still relevant, please refile it at https://github.com/zopefoundation/zope.contenttype.