How to prevent a shared document from downloading more than once?

Wade Brainerd wadetb at
Mon Mar 16 12:34:14 EDT 2009

I wrote a brief proposal a few weeks ago for an improvement to the
collab API that might help this problem.  The discussion is in  Aleksey Lim wrote an example
implementation of this Cartoon Builder.

The idea is that rather than having overlapping entry points for
intializing activity instances: __init__ (new instance but all the
others also), read_file (resume instance), shared_cb (join, share
instance) we have a new set of callbacks which are invoked *after*

share_instance(is_initiator) - could be split into join_instance and

alsroot's implementation is below, and it calls the old interfaces
when they are not present.

Perhaps these new callbacks could be integrated into Sugar 0.86?  But
in the meantime, you can always just add Aleksey's into your


On Mon, Mar 16, 2009 at 11:29 AM, James Simmons
<jim.simmons at> wrote:
> It looks like my last naive question about collaboration started a
> discussion so notable that Walter Bender wrote about it in his blog
>  Let's see what you can do with this one.
> Both my Activities, Read ETexts and View Slides, have document sharing
> code mostly copied from the core Read activity.  Currently this works
> just fine in both Activities, with only one problem.  Suppose someone
> shares a document with me, I receive it successfully, then quit, causing
> the copied document to be saved in my Journal.  Now if the original user
> stops sharing (closes his copy of the Activity) and I resume mine I get
> my stored copy and all is wonderful.  But suppose the original user
> *doesn't* stop sharing.  I resume my copy, see the stored copy on the
> screen, but I *still* download the document my friend is sharing.  I
> don't want to do that.  It wastes bandwidth and time and causes *keep*
> errors when you close the document.
> Now the problem is, the sharing code is in the __init__() method, which
> always runs before anything else, and the read_file() method, which runs
> when you resume from the Journal, unfortunately *after* the Activity has
> already decided it needs to download the file.  I need a way for the
> __init__ method to realize that it doesn't need to download the file, or
> some other way to deal with the problem.
> Thanks,
> James Simmons
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