I'm proud to announce "Gadget-to-Gadget Communication", otherwise
known as PubSub, which is a killer new beta feature that's currently
available for you all to try out!

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What is "Gadget-to-Gadget Communication", a.k.a. PubSub?

PubSub allows multiple gadgets on the same page to send and receive
data from each other.  In other words, you can now build a gadget that
communicates back and forth with one another.  This introduces a brand
new concept and strategy involved when writing gadgets.  Information
is no longer constrained to fit inside a single gadget.  Instead, you
can now split up various pieces of information amongst multiple
gadgets and allow them to communicate with each other to paint a
bigger picture.  Gadgets now have the ability to be more closely
integrated with one another and present a network of information to
users.  If users only care about one particular segment, they can
simply remove or minimize any gadgets containing extraneous
information that they don't care about.

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How does PubSub work?

PubSub is a new framework which allows 'publisher' gadgets on iGoogle
to communicate changes to 'subscriber' gadgets that have declared
interest in those changes.  This is currently available only on
iGoogle and publisher/subscriber gadgets must be on the same page.
For a list of current issues and limitations, see more information
below.

Here's documentation on how to get to started:
http://www.google.com/apis/gadgets/pubsub.html

Here's an iGoogle tab you can add to quickly see some simple examples:
http://www.google.com/ig/sharetab?source=stb&atr=PubSub&n_32=url%3Dht...

*Note:* As a beta feature, documentation on PubSub is not currently
linked to from the Google Gadgets API developer guide or anywhere
else.

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What's a BETA-feature?

It's an early release of a feature in order get valuable feedback from
real gadget developers (all of you) about the current design along
with some ideas on how to make it better.  We can't promise that you
won't encounter any bugs since it's still a beta.  However, when any
changes arise, we'll notify everyone about the change by posting it to
this thread.  We're thrilled to hear your opinions on the design as
well as any creative ideas on how to use it.  If you have any
questions or comments, please let us know.

In the meantime, here's the current list of limitations and known
issues:
-- Need more practical examples.  Coming soon.
-- Does not work in Safari.  Works correctly in Firefox and IE.
-- Only works in iGoogle.  Does not work on third-party websites or
other container pages such as Google Desktop.
-- Only available to type="html" and type="html-inline" gadgets.
-- Does not work consistently when multiple inlined (type="html-
inline") "subscriber" gadgets exist on the same page in iGoogle.
-- Moving (drag/dropping) a "subscriber" gadget to a different
position in iGoogle creates an error.  PubSub ceases to work
afterwards.
-- The "finance_symbol" channel described in the documentation is
currently broken.
-- Publisher gadgets cannot pass empty strings to subscriber gadgets.
-- JavaScript error is sometimes thrown when loading gadgets on
iGoogle.
-- Browser 'Stop' buttons sometimes have strange flickering behavior.

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As always, please reply back with any feedback or comments you may
have.  We'd love to hear from you!

Have fun!

Dann