Well, to me this sounds like Evolution's behavior is buggy at best, 
but rather very broken. I don't think it makes sense to workaround its 
behavior until it has at least official support for WebDAV.

Yes, I know that it is a bit tricky.

Did you examine the content sended to Kronolith?



I forgot comment you something. At this point, we experienced a weird 
behaviour from Evolution: try to select Free/Busy on Publish as:. Yes, 
i know, it sould be iCal, but try it.



Sniffing traffic, I realised that, at first place, Evolution tries to 
publish calendar as Free/Busy format, even if you select iCal format. 
But then i selected Free/Busy format, and i could get the iCal format!.



Weird, and I think it is a bug from Evolution.

And I still can't get it working this way, nothing happens when I 
click on Publish.

Wow, that's complicated. I wonder why it doesn't offer a way to 
subscribe to WebDAV calendars in the first place.

Well, I can tell you my work around.



In Evolution, you can get webcal calendars (works fine with HTTP 
authentication, but read-only), and CalDAV calendars (will be the best 
option soon in Kronolith ;-)



Our goal was to do a publication with Evolution using WebDAV, similary 
like Ligthning/Sunbird does.

To do it, Evolution (version 2.12.1 on Ubuntu) offers the next way:



1 - Edit -> Properties -> Calendar and Tasks -> Calendar Publishing -> Add

2 - You select all calendars that you want to publish (it doesn't mind 
if are local or webcals)

3 - Publish location with:

     - Service Type: WebDAV(HTTP)

     - Server: your horde server

     - File: /rpc.php/kronolith/[user].ics

     - Username and password for the HTTP authentication



An then, when you select Action -> Publish Calendar Information, 
occurs the steps of Comment #1.



With the patch attached, it works for me.

As far as I can see, Evolution only supports CalDAV calendars, which 
is not fully implemented in Kronolith yet. When I tried to add 
Kronolith calendars to Evolution, the HTTP authentication worked 
perfectly, but Evolution didn't continue to send requests after the 
initial OPTIONS request. Did you see anything else?

Whe Evolution mail client tries to do a webdav publication, apart from 
send data as application/octect-steam, it follows the next steps:



1 - It tries to publish without authentication data and without any 
calendar data. If 401 Unauthorized returned by the server, evolution 
tries to do a authentication BUT no calendar data is sent.

2 - If afther that athentication steps evolution get a HTTP 200 OK 
response, it sends the vcalendar data.



To handle that situation, kronolith sould be able to accept that 
content type and handle empty requests.



I suggest a way to do it, checking data size in webdav.php and adding 
content-type in api.php. Even the data size check could be done inside 
_kronolith_put, in api.php.