[Pmwiki-users] Re: PmWikiDraw and multiple editors?

[Ciaran]

On Thu, 16 Dec 2004 11:11:35 +0100, chr at home.se <chr at home.se> wrote:
> On Thu, 16 Dec 2004, Ciaran wrote:
> 
> > How exactly would you suggest this is implemented, bearing in mind the
> > fact that you can never tell when a user has finished drawing.  Their
> > web client may have crashed, or they may have just changed pages and
> > not exited correctly ?   Whatever I come up with ends up breaking the
> > system in some way, i.e. locking everyone out for x hours etc :)
> 
> I don't know how to achieve it, but the important thing is that when you
> save you don't (accidentally and uknowingly) overwrite changes some else
> has made.  I suspect we will need some special mechanism on the pmwiki
> side anyway, so plain upload probably won't work. What I mean is that when
> you download the drawing source, you need to remember it's timestamp, and
> then when you upload it you need to check that the source (on the wiki
> site) still have the same time stamp. This operation needs to be atomic.
> 
> You should probably discuss this in a more general context, Patrick and
> other people on this list probably have some useful ideas. The problems
> are quite similar to handling wiki pages for instance.
> 
> /Christian
> 
> --
> Christian Ridderstr?m, +46-8-768 39 44               http://www.md.kth.se/~chr
> 
> 
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> 
The only interface to the system I have available is the upload
mechanism :) PmWiki pages do not lock on editing.  In PmWiki1 if user
b saved the changes based on something that was loaded after user a
started making changes and before user a saved.  Then user a would
lose their changes when user b eventually saved.  This is *exactly*
what the behaviour of PmWikiDraw is.  In PmWiki2 its somewhat better,
the changes are merged.  I'm not convinced that there is *any* way
with the current uploads interface I can achieve similar behaviour. 
The best I hope to offer is the version history, which would enable a
user to see there were multiple changes made.    I can't see Pm
modifying PmWiki to allow for this requirement but if you both want to
discuss it and come up with a way in which PmWikiDraw can use it, then
I'm happy to spend some time (and believe me it will take a fair
amount of effort) to get it working.  And a change like this would
definately break backwards compatibility!

Thanks
-- 
- Ciaran