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<?xml version="1.0" ?>
<node name="/Client_Observer"
xmlns:tp="http://telepathy.freedesktop.org/wiki/DbusSpec#extensions-v0">
<tp:copyright>Copyright (C) 2008 Collabora Ltd.</tp:copyright>
<tp:copyright>Copyright (C) 2008 Nokia Corporation</tp:copyright>
<tp:license xmlns="http://www.w3.org/1999/xhtml">
<p>This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.</p>
<p>This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.</p>
<p>You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.</p>
</tp:license>
<interface name="org.freedesktop.Telepathy.Client.Observer.DRAFT"
tp:causes-havoc="experimental">
<tp:added version="0.17.UNRELEASED"/>
<tp:requires interface="org.freedesktop.Telepathy.Client.DRAFT"/>
<tp:docstring xmlns="http://www.w3.org/1999/xhtml">
<p>Observers monitor the creation of new channels. This
functionality can be used for things like message logging.
All observers are notified simultaneously.</p>
<p>Observers SHOULD NOT modify the state of a channel except
via user interaction.</p>
<tp:rationale>
<p>We want Observer UIs for file transfer channels (a progress
bar for the transfer) to be able to have a Cancel button.</p>
</tp:rationale>
<p>Observers MUST NOT carry out actions that exactly one process
must take responsibility for (e.g. acknowledging Text
messages, or carrying out the actual transfer in a file transfer
channel).</p>
<tp:rationale>
<p>Since arbitrarily many observers can be activated for
each channel, it would not make sense for observers to do things
that can only be done by one process (acknowledging
<tp:dbus-ref
namespace="org.freedesktop.Telepathy.Channel.Type">Text</tp:dbus-ref>
messages, carrying out streaming for
<tp:dbus-ref
namespace="org.freedesktop.Telepathy.Channel.Type">StreamedMedia</tp:dbus-ref>
channels, doing the actual data transfer for file transfers,
setting up the out-of-band connection for Tubes). The
<tp:dbus-ref
namespace="org.freedesktop.Telepathy.Client">Handler</tp:dbus-ref>
is responsible for such tasks.</p>
<p>Handlers MAY, of course, delegate responsibility for these
tasks to other processes (including those run as observers),
but this MUST be done explicitly via a request from the Handler
to the Observer.</p>
</tp:rationale>
<p>Whenever new channels are signalled, the channel dispatcher
will notify all running or activatable observers whose
<tp:member-ref>ObserverChannelFilter</tp:member-ref> property
(possibly as cached in the .client file) indicates that they are
interested in the channel.</p>
<p>Observers are activated for all channels in which they have
registered an interest - incoming, outgoing or automatically created -
although of course the ObserverChannelFilter property can be set
to filter on the
<tp:dbus-ref
namespace="org.freedesktop.Telepathy">Channel.FUTURE.Requested</tp:dbus-ref>
property.</p>
</tp:docstring>
<property name="ObserverChannelFilter"
tp:name-for-bindings="Observer_Channel_Filter"
type="aa{sv}" access="read" tp:type="Channel_Class[]">
<tp:docstring xmlns="http://www.w3.org/1999/xhtml">
<p>A specification of the channels in which this observer is
interested. The <tp:member-ref>ObserveChannels</tp:member-ref> method
should be called by the channel dispatcher whenever any of the new
channels in a NewChannels signal match this description.</p>
<p>(FIXME: open issue: do we want this, and the corresponding
Approver and Handler properties, to be able to change at
runtime?)</p>
<p>Only certain D-Bus types have useful semantics for matching like this,
so only certain types are allowed:</p>
<dl>
<dt>Integers of all sizes, including byte (y, n, q, i, u, x, t)</dt>
<dd>Matched by numeric value, regardless of type (e.g. 42 as a
16-bit signed integer 'n' is considered equal to 42 as a 32-bit
unsigned integer 'u')</dd>
<dt>Booleans (b)</dt>
<dd>Matched by equality in the obvious way; not considered equal to any
other type</dd>
<dt>Strings (s)</dt>
<dd>Matched by equality in the obvious way; not considered equal to any
other type</dd>
<dt>Object paths (o)</dt>
<dd>Matched by equality in the obvious way; not considered equal to any
other type</dd>
</dl>
<p>This property never changes while the observer process is
running. For activatable processes, the filter can change due to an
upgrade - the channel dispatcher SHOULD observe changes to .client files
using a mechanism like inotify.</p>
<p>For observers that have a .client file, the channel dispatcher
may discover this property from keys of the form
<code><em>propertyname</em>/<em>type</em></code>,
in groups in the .client file whose name is the name of this
interface followed by <code>.ObserverChannelFilter</code>,
a space and an ASCII decimal number starting from 0.</p>
<p>Integers in the .client file are encoded in ASCII decimal, booleans
are encoded as "true" or "false", and strings are encoded in the usual
way for desktop files (including the C-style backslash escapes
documented in the Desktop Entry specification).</p>
<p>For instance, a .client file for an observer that is only interested
in Text channels, with CONTACT or ROOM handles, that were requested by
a local client:</p>
<pre>
[org.freedesktop.Telepathy.Client.DRAFT]
Interfaces=org.freedesktop.Telepathy.Client.Observer.DRAFT;
[org.freedesktop.Telepathy.Client.Observer.DRAFT.ObserverChannelFilter 0]
org.freedesktop.Telepathy.Channel.Type s=org.freedesktop.Telepathy.Channel.Type.Text
org.freedesktop.Telepathy.Channel.TargetHandleType u=1
org.freedesktop.Telepathy.Channel.FUTURE.Requested b=true
[org.freedesktop.Telepathy.Client.Observer.DRAFT.ObserverChannelFilter 1]
org.freedesktop.Telepathy.Channel.Type s=org.freedesktop.Telepathy.Channel.Type.Text
org.freedesktop.Telepathy.Channel.TargetHandleType u=2
org.freedesktop.Telepathy.Channel.FUTURE.Requested b=true
</pre>
</tp:docstring>
</property>
<method name="ObserveChannels" tp:name-for-bindings="Observe_Channels">
<tp:docstring xmlns="http://www.w3.org/1999/xhtml">
<p>Called by the channel dispatcher when channels in which the
observer has registered an interest are created.</p>
<p>The observer MUST NOT return from this method call until it is ready
for a handler for the channel to run (which may change the channel's
state).</p>
<tp:rationale>
<p>The channel dispatcher must wait for observers to start up,
to avoid the following race: text channel logger (observer) gets
ObserveChannel, text channel handler gets
<tp:dbus-ref
namespace="org.freedesktop.Telepathy.Client.Handler.DRAFT">HandleChannels</tp:dbus-ref>
channel handler starts up faster and acknowledges messages,
logger never sees those messages.</p>
</tp:rationale>
</tp:docstring>
<arg name="Account" type="o" direction="in">
<tp:docstring>
The
<tp:dbus-ref namespace="org.freedesktop.Telepathy">Account</tp:dbus-ref>
with which the channels are associated. The
well-known bus name to use is that of the
<tp:dbus-ref namespace="org.freedesktop.Telepathy">AccountManager</tp:dbus-ref>.
</tp:docstring>
</arg>
<arg name="Connection" type="o" direction="in">
<tp:docstring>
The
<tp:dbus-ref namespace="org.freedesktop.Telepathy">Connection</tp:dbus-ref>
with which the channels are associated. The
well-known bus name to use can be derived from this object
path by removing the leading '/' and replacing all subsequent
'/' by '.'.
</tp:docstring>
</arg>
<arg name="Channels" type="a(oa{sv})" tp:type="Channel_Details[]"
direction="in">
<tp:docstring xmlns="http://www.w3.org/1999/xhtml">
<p>The
<tp:dbus-ref
namespace="org.freedesktop.Telepathy">Channel</tp:dbus-ref>s
and their properties. Their well-known bus names are all the same
as that of the Connection.</p>
<tp:rationale>
<p>The ChannelDispatchOperation is <em>not</em> supplied: for
requests, there isn't one, and for incoming channels, it hasn't
been created yet.</p>
</tp:rationale>
</tp:docstring>
</arg>
<arg name="Observer_Info" type="a{sv}" direction="in">
<tp:docstring xmlns="http://www.w3.org/1999/xhtml">
<p>Additional information about these channels. No keys are
currently defined.</p>
<p>If keys are defined for this dictionary, all will be optional;
observers MAY safely ignore any entry in this dictionary.</p>
</tp:docstring>
</arg>
</method>
</interface>
</node>
<!-- vim:set sw=2 sts=2 et ft=xml: -->
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