[Pidgin] #4650: Use XEP-0115: Entity Capabilities e.g. to not send XHTML-IM content, Chat State Notificiations

[Pidgin]

#4650: Use XEP-0115: Entity Capabilities e.g. to not send XHTML-IM content, Chat
State Notificiations
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Reporter:  spike411  |       Owner:  nwalp                      
    Type:  defect    |      Status:  new                        
Priority:  minor     |   Component:  XMPP                       
 Version:            |    Keywords:  xmpp, caps, xhtml, xhtml-im
 Pending:  0         |  
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 Please, see the original ticket filed for Adium:

 http://trac.adiumx.com/ticket/8681

 Currently, Adium (and possibly Pidgin/libpurple!) sends XHTML-IM content
 and Chat States Notifications to every XMPP contact, even though it
 doesn't advertise support for these extensions.

 The problem is that for example Bombus (mobile, GPRS) users don't want to
 receive this data, because it costs them more money and they can't do
 anything about it.

 Using the information obtained via Entity Capabilities is exactly what's
 needed.
 ----
 1.1 Motivation

 It is often desirable for an XMPP application (commonly but not
 necessarily a client) to take different actions depending on the
 capabilities of another application from which it receives presence
 information. Examples include:

  - Showing a different set of icons depending on the capabilities of other
 entities.
  - Not sending XHTML-IM or other rich content to plaintext clients such as
 cell phones.
  - Allowing the initiation of a Voice over IP (VoIP) session only to
 clients that support Jingle and Jingle Audio via RTP.
  - Not showing a "Send a File" button if another user's client does not
 support File Transfer.
  - Filtering Publish-Subscribe notifications based on advertised
 subscriber interests.
 ----

 The File Transfer button example is also applicable to current Adium (and
 Pidgin).

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Ticket URL: <http://developer.pidgin.im/ticket/4650>
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