libnotify/docs/notification-spec.xml

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<article id="index">
 <articleinfo>
  <title>Desktop Notifications Specification</title>
  <releaseinfo>Version 1.1</releaseinfo>
  <date>25 August 2007</date>
  <authorgroup>
   <author>
    <firstname>Mike</firstname>
    <surname>Hearn</surname>
    <affiliation>
     <address>
      <email>mike@navi.cx</email>
     </address>
    </affiliation>
   </author>
   <author>
    <firstname>Christian</firstname>
    <surname>Hammond</surname>
    <affiliation>
     <address>
      <email>chipx86@chipx86.com</email>
     </address>
    </affiliation>
   </author>
  </authorgroup>
  <revhistory>
   <revision>
    <revnumber>1.0</revnumber>
    <date>25 August 2007</date>
    <authorinitials>cdh</authorinitials>
    <revremark>
     Added spec_version to the GetServerInformation return values.
     Mark this specification as a 1.0.
    </revremark>
   </revision>
   <revision>
    <revnumber>0.9</revnumber>
    <date>15 January 2006</date>
    <authorinitials>cdh</authorinitials>
    <revremark>
     Clarify the naming for the application IDs.
     Put back a number of things that probably shouldn't have been removed
     from the spec.
    </revremark>
   </revision>
   <revision>
    <revnumber>0.8</revnumber>
    <date>23 September 2005</date>
    <authorinitials>J5</authorinitials>
    <revremark>
     Major overhaul of spec to work with the newer D-Bus recursive type system.
     Simplify protocol.
     Changed the verbage notification type to category
    </revremark>
   </revision>
   <revision>
    <revnumber>0.7</revnumber>
    <date>28 July 2005</date>
    <authorinitials>cdh</authorinitials>
    <revremark>
     Added "x" and "y" hints. Talk about the variant type for hint values.
    </revremark>
   </revision>
   <revision>
    <revnumber>0.6</revnumber>
    <date>1 April 2005</date>
    <authorinitials>cdh</authorinitials>
    <revremark>
     Updated to work with D-BUS 0.31+.
    </revremark>
   </revision>
   <revision>
    <revnumber>0.5</revnumber>
    <date>2 October 2004</date>
    <authorinitials>cdh</authorinitials>
    <revremark>
     Added a "suppress-sound" hint. Added a "sound" capability. Renamed the
     "soundfile" hint to sound-file".
    </revremark>
   </revision>
   <revision>
    <revnumber>0.4</revnumber>
    <date>29 September 2004</date>
    <authorinitials>cdh</authorinitials>
    <revremark>
     Added image support in markup, and made the restrictions on markup more
     clear. Removed the High urgency. Added new notification types. Fixed
     notification expiration.
    </revremark>
   </revision>
   <revision>
    <revnumber>0.3</revnumber>
    <date>15 September 2004</date>
    <authorinitials>cdh</authorinitials>
    <revremark>Added hint and notification type sections</revremark>
   </revision>
   <revision>
    <revnumber>0.2</revnumber>
    <date>foo</date>
    <authorinitials>mh</authorinitials>
    <revremark>Added replaces field to protocol</revremark>
   </revision>
   <revision>
    <revnumber>0.1</revnumber>
    <date>foo</date>
    <authorinitials>mh</authorinitials>
    <revremark>Initial version</revremark>
   </revision>
  </revhistory>
 </articleinfo>

 <sect1 id="introduction">
  <title>Introduction</title>
  <para>
   This is a draft standard for a desktop notifications service, through
   which applications can generate passive popups (sometimes known as
   "poptarts") to notify the user in an asynchronous manner of events.
  </para>
  <para>
   This specification explicitly does not include other types of
   notification presentation such as modal message boxes, window manager
   decorations or window list annotations.
  </para>
  <para>
   Example use cases include:
  </para>
  <itemizedlist>
   <listitem>
    <para>
     Presence changes in IM programs: for instance, MSN Messenger on
     Windows pioneered the use of passive popups to indicate presence
     changes.
    </para>
   </listitem>
   <listitem><para>Scheduled alarm</para></listitem>
   <listitem><para>Completed file transfer</para></listitem>
   <listitem><para>New mail notification</para></listitem>
   <listitem><para>Low disk space/battery warnings</para></listitem>
  </itemizedlist>
 </sect1>

 <sect1 id="basic-design">
  <title>Basic Design</title>
  <para>
   In order to ensure that multiple notifications can easily be
   displayed at once, and to provide a convenient implementation, all
   notifications are controlled by a single session-scoped service which
   exposes a D-BUS interface.
  </para>
  <para>
   On startup, a conforming implementation should take the
   <literal>org.freedesktop.Notifications</literal> service on
   the session bus. This service will be referred to as the "notification
   server" or just "the server" in this document. It can optionally be
   activated automatically by the bus process, however this is not required
   and notification server clients must not assume that it is available.
  </para>
  <para>
   The server should implement the
   <literal>org.freedesktop.Notifications</literal> interface on
   an object with the path <literal>"/org/freedesktop/Notifications"</literal>.
   This is the only interface required by this version of the specification.
  </para>
  <para>
   A notification has the following components:
  </para>
  <table>
   <title>Notification Components</title>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>Component</entry>
      <entry>Description</entry>
     </row>
    </thead>
    <tbody valign="top">
     <row>
      <entry>Application Name</entry>
      <entry>
       This is the optional name of the application sending the notification.
       This should be the application's formal name, rather than some sort
       of ID. An example would be "FredApp E-Mail Client," rather than
       "fredapp-email-client."
      </entry>
     </row>
     <row>
      <entry>Replaces ID</entry>
      <entry>
       An optional ID of an existing notification that this
       notification is intended to replace.
      </entry>
     </row>
     <row>
      <entry>Notification Icon</entry>
      <entry>
        The notification icon. See <xref linkend="icons-and-images-formats"/>.
      </entry>
     </row>
     <row>
      <entry>Summary</entry>
      <entry>
       This is a single line overview of the notification. For instance,
       "You have mail" or "A friend has come online". It should generally
       not be longer than 40 characters, though this is not a requirement,
       and server implementations should word wrap if necessary. The summary
       must be encoded using UTF-8.
      </entry>
     </row>
     <row>
      <entry>Body</entry>
      <entry>
       <para>
        This is a multi-line body of text. Each line is a paragraph, server
        implementations are free to word wrap them as they see fit.
       </para>
       <para>
        The body may contain simple markup as specified in
        <xref linkend="markup"/>. It must be encoded using UTF-8.
       </para>
       <para>
        If the body is omitted, just the summary is displayed.
       </para>
      </entry>
     </row>
     <row>
      <entry>Actions</entry>
      <entry>
       <para>
        The actions send a request message back to the notification client
        when invoked. This functionality may not be implemented by the
        notification server, conforming clients should check if it is available
        before using it (see the GetCapabilities message in
        <xref linkend="protocol"/>). An implementation is free to ignore any
        requested by the client. As an example one possible rendering of
        actions would be as buttons in the notification popup.
       </para>
       <para>
        Actions are sent over as a list of pairs. Each even element in the
        list (starting at index 0) represents the identifier for the action.
        Each odd element in the list is the localized string that will be
        displayed to the user.
       </para>
       <para>
        The default action (usually invoked my clicking the notification)
        should have a key named <literal>"default"</literal>. The name can
        be anything, though implementations are free not to display it.
       </para>
      </entry>
     </row>
     <row>
      <entry>Hints</entry>
      <entry>
       <para>
        Hints are a way to provide extra data to a notification server that
        the server may be able to make use of.
       </para>
       <para>See <xref linkend="hints"/> for a list of available hints.</para>
      </entry>
     </row>
     <row>
      <entry>Expiration Timeout</entry>
      <entry>
       <para>
        The timeout time in milliseconds since the display of the notification
        at which the notification should automatically close.
       </para>
       <para>
        If -1, the notification's expiration time is dependent on the
        notification server's settings, and may vary for the type of
        notification.
       </para>
       <para>
        If 0, the notification never expires.
       </para>
      </entry>
     </row>
    </tbody>
   </tgroup>
  </table>
  <para>
   Each notification displayed is allocated a unique ID by the server.
   This is unique within the session. While the notification server is
   running, the ID will not be recycled unless the capacity of a uint32 is
   exceeded.
  </para>
  <para>
   This can be used to hide the notification before the expiration timeout
   is reached. It can also be used to atomically replace the notification
   with another. This allows you to (for instance) modify the contents of
   a notification while it's on-screen.
  </para>
 </sect1>

 <sect1 id="backwards-compat" xreflabel="Backwards Compatibility">
  <title>Backwards Compatibility</title>
  <para>
   Clients should try and avoid making assumptions about the presentation and
   abilities of the notification server. The message content is the most
   important thing.
  </para>
  <para>
   Clients can check with the server what capabilities are supported
   using the <literal>GetCapabilities</literal> message. See
   <xref linkend="protocol"/>.
  </para>
  <para>
   If a client requires a response from a passive popup, it should be
   coded such that a non-focus-stealing message box can be used in the
   case that the notification server does not support this feature.
  </para>
 </sect1>

 <sect1 id="markup" xreflabel="Markup">
  <title>Markup</title>
  <para>
   Body text may contain markup. The markup is XML-based, and consists
   of a small subset of HTML along with a few additional tags.
  </para>
  <para>
   The following tags should be supported by the notification server.
   Though it is optional, it is recommended. Notification servers that do
   not support these tags should filter them out.
  </para>
  <informaltable>
   <tgroup cols="2">
    <tbody valign="top">
     <row>
      <entry>
       <sgmltag class="starttag">b</sgmltag> ...
       <sgmltag class="endtag">b</sgmltag>
      </entry>
      <entry>Bold</entry>
     </row>
     <row>
      <entry>
       <sgmltag class="starttag">i</sgmltag> ...
       <sgmltag class="endtag">i</sgmltag>
      </entry>
      <entry>Italic</entry>
     </row>
     <row>
      <entry>
       <sgmltag class="starttag">u</sgmltag> ...
       <sgmltag class="endtag">u</sgmltag>
      </entry>
      <entry>Underline</entry>
     </row>
     <row>
      <entry>
       <sgmltag class="starttag">a href="..."</sgmltag> ...
       <sgmltag class="endtag">a</sgmltag>
      </entry>
      <entry>Hyperlink</entry>
     </row>
     <row>
      <entry>
       <sgmltag class="emptytag">img src="..." alt="..."</sgmltag>
      </entry>
      <entry>Image</entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
  <para>
   A full-blown HTML implementation is not required of this spec, and
   notifications should never take advantage of tags that are not listed
   above. As notifications are not a substitute for web browsers or complex
   dialogs, advanced layout is not necessary, and may in fact limit the
   number of systems that notification services can run on, due to memory
   usage and screen space. Such examples are PDAs, certain cell phones, and
   slow PCs or laptops with little memory.
  </para>
  <para>
   For the same reason, a full XML or XHTML implementation using XSLT or
   CSS stylesheets is not part of this specification. Information that
   must be presented in a more complex form should use an application-specific
   dialog, a web browser, or some other display mechanism.
  </para>
  <para>
   The tags specified above mark up the content in a way that allows them
   to be stripped out on some implementations without impacting the actual
   content.
  </para>

  <sect2 id="hyperlinks" xreflabel="Hyperlinks">
   <title>Hyperlinks</title>
   <para>
    Hyperlinks allow for linking one or more words to a URI. There is no
    requirement to allow for images to be linked, and it is highly suggested
    that implementations do not allow this, as there is no clean-looking,
    standard visual indicator for a hyperlinked image.
   </para>
   <para>
    Hyperlinked text should appear in the standard blue underline format.
   </para>
   <para>
    Hyperlinks cannot function as a replacement for actions. They are
    used to link to local directories or remote sites using standard URI
    schemes.
   </para>
   <para>
    Implementations are not required to support hyperlinks.
   </para>
  </sect2>

  <sect2 id="images" xreflabel="Images">
   <title>Images</title>
   <para>
    Images may be placed in the notification, but this should be done with
    caution. The image should never exceed 200x100, but this should be thought
    of as a maximum size. Images should always have alternative text
    provided through the <literal>alt="..."</literal> attribute.
   </para>
   <para>
    Image data cannot be embedded in the message itself. Images referenced
    must always be local files.
   </para>
   <para>
    Implementations are not required to support images.
   </para>
  </sect2>
 </sect1>

 <sect1 id="icons-and-images" xreflabel="Icons and Images">
  <title>Icons and Images</title>
  <para>
   A notification can optionally have an associated icon and/or image.
  </para>
  <para>
   The icon is defined by the "app_icon" parameter.
   The image can be defined by the "image_path", the "image_data" hint or the
   deprecated "icon_data" hint.
  </para>
  <sect2>
   <title>Priorities</title>
   <para>
    An implementation which only displays one image or icon must choose which one
    to display using the following order:
    <orderedlist>
     <listitem><para>"image_data"</para></listitem>
     <listitem><para>"image_path"</para></listitem>
     <listitem><para>app_icon parameter</para></listitem>
     <listitem><para>for compatibility reason, "icon_data"</para></listitem>
    </orderedlist>
   </para>

   <para>
    An implementation which can display both the image and icon must show the
    icon from the "app_icon" parameter and choose which image to display using
    the following order:
    <orderedlist>
     <listitem><para>"image_data"</para></listitem>
     <listitem><para>"image_path"</para></listitem>
     <listitem><para>for compatibility reason, "icon_data"</para></listitem>
    </orderedlist>
   </para>
  </sect2>

  <sect2 id="icons-and-images-formats" xreflabel="Icons and Images Formats">
   <title>Formats</title>
   <para>
    The "image_data" and "icon_data" hints should be a raw image data structure
    of signature (iiibiiay) which describes the width, height, rowstride, has
    alpha, bits per sample, channels and image data respectively.
  </para>
   <para>
    The "app_icon" parameter and "image_path" hint should be either an URI
    (file:// is the only URI schema supported right now) or a name in a
    freedesktop.org-compliant icon theme (not a GTK+ stock ID).
   </para>
  </sect2>
 </sect1>

 <sect1 id="categories" xreflabel="Categories">
  <title>Categories</title>
  <para>
   Notifications can optionally have a type indicator. Although neither
   client or nor server must support this, some may choose to. Those servers
   implementing categories may use them to intelligently display
   the notification in a certain way, or group notifications of similar
   types.
  </para>
  <para>
   Categories are in
   <literal><replaceable>class.specific</replaceable></literal> form.
   <literal>class</literal> specifies the generic type of notification, and
   <literal>specific</literal> specifies the more specific type of
   notification.
  </para>
  <para>
   If a specific type of notification does not exist for your notification,
   but the generic kind does, a notification of type
   <literal><replaceable>class</replaceable></literal> is acceptable.
  </para>
  <para>
   Third parties, when defining their own categories, should discuss
   the possibility of standardizing on the hint with other parties, preferably
   in a place such as the
   <ulink url="http://freedesktop.org/mailman/listinfo/xdg">xdg</ulink>
   mailing list at
   <ulink url="http://freedesktop.org/">freedesktop.org</ulink>. If it
   warrants a standard, it will be added to the table above. If no
   consensus is reached, the category should be in the form of
   "<literal>x-<replaceable>vendor</replaceable>.<replaceable>class</replaceable>.<replaceable>name</replaceable></literal>."
  </para>
  <para>
   The following table lists standard notifications as defined by this spec.
   More will be added in time.
  </para>
  <table>
   <title>Categories</title>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>Type</entry>
      <entry>Description</entry>
     </row>
    </thead>
    <tbody valign="top">
     <row>
      <entry><literal>"device"</literal></entry>
      <entry>
       A generic device-related notification that doesn't fit into
       any other category.
      </entry>
     </row>
     <row>
      <entry><literal>"device.added"</literal></entry>
      <entry>A device, such as a USB device, was added to the system.</entry>
     </row>
     <row>
      <entry><literal>"device.error"</literal></entry>
      <entry>A device had some kind of error.</entry>
     </row>
     <row>
      <entry><literal>"device.removed"</literal></entry>
      <entry>
       A device, such as a USB device, was removed from the system.
      </entry>
     </row>
     <row>
      <entry><literal>"email"</literal></entry>
      <entry>
       A generic e-mail-related notification that doesn't fit into any
       other category.
      </entry>
     </row>
     <row>
      <entry><literal>"email.arrived"</literal></entry>
      <entry>A new e-mail notification.</entry>
     </row>
     <row>
      <entry><literal>"email.bounced"</literal></entry>
      <entry>A notification stating that an e-mail has bounced.</entry>
     </row>
     <row>
      <entry><literal>"im"</literal></entry>
      <entry>
       A generic instant message-related notification that doesn't fit
       into any other category.
      </entry>
     </row>
     <row>
      <entry><literal>"im.error"</literal></entry>
      <entry>An instant message error notification.</entry>
     </row>
     <row>
      <entry><literal>"im.received"</literal></entry>
      <entry>A received instant message notification.</entry>
     </row>
     <row>
      <entry><literal>"network"</literal></entry>
      <entry>
       A generic network notification that doesn't fit into any other
       category.
      </entry>
     </row>
     <row>
      <entry><literal>"network.connected"</literal></entry>
      <entry>
       A network connection notification, such as successful sign-on to a
       network service. This should not be confused with
       <literal>device.added</literal> for new network devices.
      </entry>
     </row>
     <row>
      <entry><literal>"network.disconnected"</literal></entry>
      <entry>
       A network disconnected notification. This should not be confused with
       <literal>device.removed</literal> for disconnected network devices.
      </entry>
     </row>
     <row>
      <entry><literal>"network.error"</literal></entry>
      <entry>
       A network-related or connection-related error.
      </entry>
     </row>
     <row>
      <entry><literal>"presence"</literal></entry>
      <entry>
       A generic presence change notification that doesn't fit into
       any other category, such as going away or idle.
      </entry>
     </row>
     <row>
      <entry><literal>"presence.offline"</literal></entry>
      <entry>An offline presence change notification.</entry>
     </row>
     <row>
      <entry><literal>"presence.online"</literal></entry>
      <entry>An online presence change notification.</entry>
     </row>
     <row>
      <entry><literal>"transfer"</literal></entry>
      <entry>
       A generic file transfer or download notification that doesn't fit
       into any other category.
      </entry>
     </row>
     <row>
      <entry><literal>"transfer.complete"</literal></entry>
      <entry>A file transfer or download complete notification.</entry>
     </row>
     <row>
      <entry><literal>"transfer.error"</literal></entry>
      <entry>A file transfer or download error.</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="urgency-levels" xreflabel="Urgency Levels">
  <title>Urgency Levels</title>
  <para>
   Notifications have an urgency level associated with them. This defines
   the importance of the notification. For example, "Joe Bob signed on"
   would be a low urgency. "You have new mail" or "A USB device was unplugged"
   would be a normal urgency. "Your computer is on fire" would be a critical
   urgency.
  </para>
  <para>Urgency levels are defined as follows:</para>
  <table>
   <title>Urgency Levels</title>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>Type</entry>
      <entry>Description</entry>
     </row>
    </thead>
    <tbody valign="top">
     <row>
      <entry>0</entry>
      <entry>Low</entry>
     </row>
     <row>
      <entry>1</entry>
      <entry>Normal</entry>
     </row>
     <row>
      <entry>2</entry>
      <entry>Critical</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
  <para>
   Developers must use their own judgement when deciding the urgency of a
   notification. Typically, if the majority of programs are using the same
   level for a specific type of urgency, other applications should follow
   them.
  </para>
  <para>
   For low and normal urgencies, server implementations may display the
   notifications how they choose. They should, however, have a sane
   expiration timeout dependent on the urgency level.
  </para>
  <para>
   Critical notifications should not automatically expire, as they are
   things that the user will most likely want to know about. They should
   only be closed when the user dismisses them, for example, by clicking on
   the notification.
  </para>
 </sect1>

 <sect1 id="hints" xreflabel="Hints">
  <title>Hints</title>
  <para>
   Hints are a way to provide extra data to a notification server that
   the server may be able to make use of.
  </para>
  <para>
   Neither clients nor notification servers are required to support any
   hints. Both sides should assume that hints are not passed, and should
   ignore any hints they do not understand.
  </para>
  <para>
   Third parties, when defining their own hints, should discuss the
   possibility of standardizing on the hint with other parties, preferably
   in a place such as the
   <ulink url="http://freedesktop.org/mailman/listinfo/xdg">xdg</ulink>
   mailing list at
   <ulink url="http://freedesktop.org/">freedesktop.org</ulink>. If it
   warrants a standard, it will be added to the table above. If no
   consensus is reached, the hint name should be in the form of
   <literal>"x-<replaceable>vendor</replaceable>-<replaceable>name</replaceable>."</literal>
  </para>
  <para>
   The value type for the hint dictionary in D-BUS is of the
   <literal>DBUS_TYPE_VARIANT</literal> container type. This allows different
   data types (string, integer, boolean, etc.) to be used for hints. When
   adding a dictionary of hints, this type must be used, rather than putting
   the actual hint value in as the dictionary value.
  </para>
  <para>
   The following table lists the standard hints as defined by this
   specification. Future hints may be proposed and added to this list
   over time. Once again, implementations are not required to support these.
  </para>
  <table>
   <title>Standard Hints</title>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Value Type</entry>
      <entry>Description</entry>
      <entry>Spec Version</entry>
     </row>
    </thead>
    <tbody valign="top">
     <row>
      <entry><literal>"category"</literal></entry>
      <entry>string</entry>
      <entry>
       The type of notification this is.
      </entry>
      <entry/>
     </row>
     <row>
      <entry><literal>"desktop-entry"</literal></entry>
      <entry>string</entry>
      <entry>
       This specifies the name of the desktop filename representing the
       calling program. This should be the same as the prefix used for the
       application's .desktop file. An example would be "rhythmbox" from
       "rhythmbox.desktop". This can be used by the daemon to retrieve the
       correct icon for the application, for logging purposes, etc.
      </entry>
      <entry/>
     </row>
     <row>
      <entry><literal>"image_data"</literal></entry>
      <entry>(iiibiiay)</entry>
      <entry>
        This is a raw data image format which describes the width, height,
        rowstride, has alpha, bits per sample, channels and image data
        respectively.
      </entry>
      <entry>&gt;= 1.1</entry>
     </row>
     <row>
      <entry><literal>"image_path"</literal></entry>
      <entry>string</entry>
      <entry>
        Alternative way to define the notification image. See <xref linkend="icons-and-images"/>.
      </entry>
      <entry>&gt;= 1.1</entry>
     </row>
     <row>
      <entry><literal>"icon_data"</literal></entry>
      <entry>(iiibiiay)</entry>
      <entry>
        <emphasis>Deprecated</emphasis>. Use image_data instead.
      </entry>
      <entry>&lt; 1.1</entry>
     </row>
     <row>
      <entry><literal>"resident"</literal></entry>
      <entry>boolean</entry>
      <entry>
       When set the server will not automatically remove the
       notification when an action has been invoked.  The notification
       will remain resident in the server until it is explicitly
       removed by the user or by the sender.  This hint is likely only
       useful when the server has the "persistence" capability.
      </entry>
      <entry/>
     </row>
     <row>
      <entry><literal>"sound-file"</literal></entry>
      <entry>string</entry>
      <entry>
       The path to a sound file to play when the notification pops up.
      </entry>
      <entry/>
     </row>
     <row>
      <entry><literal>"sound-name"</literal></entry>
      <entry>string</entry>
      <entry>
       A themeable named sound from the freedesktop.org
       <ulink url="http://0pointer.de/public/sound-naming-spec.html">sound naming specification</ulink>
       to play when the notification pops up. Similar to icon-name, only for
       sounds. An example would be "message-new-instant".
      </entry>
      <entry/>
     </row>
     <row>
      <entry><literal>"suppress-sound"</literal></entry>
      <entry>boolean</entry>
      <entry>
       Causes the server to suppress playing any sounds, if it has that
       ability. This is usually set when the client itself is going to
       play its own sound.
      </entry>
      <entry/>
     </row>
     <row>
      <entry><literal>"x"</literal></entry>
      <entry>int</entry>
      <entry>
       Specifies the X location on the screen that the notification should
       point to. The <literal>"y"</literal> hint must also be specified.
      </entry>
      <entry/>
     </row>
     <row>
      <entry><literal>"y"</literal></entry>
      <entry>int</entry>
      <entry>
       Specifies the Y location on the screen that the notification should
       point to. The <literal>"x"</literal> hint must also be specified.
      </entry>
      <entry/>
     </row>
     <row>
      <entry><literal>"urgency"</literal></entry>
      <entry>byte</entry>
      <entry>
       The urgency level.
      </entry>
      <entry/>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="protocol" xreflabel="Protocol">
  <title>D-BUS Protocol</title>
  <para>
   The following messages <emphasis>must</emphasis> be supported by all
   implementations.
  </para>

  <sect2 id="commands">
   <title>Message commands</title>

   <sect3 id="command-get-capabilities">
    <title><literal>org.freedesktop.Notifications.GetCapabilities</literal></title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>STRING_ARRAY
       <function>org.freedesktop.Notifications.GetCapabilities</function>
      </funcdef>
      <void/>
     </funcprototype>
    </funcsynopsis>
    <para>
     This message takes no parameters.
    </para>
    <para>
     It returns an array of strings. Each string describes an optional
     capability implemented by the server. The following values are
     defined by this spec:
    </para>
    <table>
     <title>Server Capabilities</title>
     <tgroup cols="2">
      <tbody valign="top">
       <row>
        <entry><literal>"actions"</literal></entry>
        <entry>
         The server will provide the specified actions to the user. Even if
         this cap is missing, actions may still be specified by the client,
         however the server is free to ignore them.
        </entry>
       </row>
       <row>
        <entry><literal>"body"</literal></entry>
        <entry>
         Supports body text. Some implementations may only show the
         summary (for instance, onscreen displays, marquee/scrollers)
        </entry>
       </row>
       <row>
        <entry><literal>"body-hyperlinks"</literal></entry>
        <entry>
         The server supports hyperlinks in the notifications.
        </entry>
       </row>
       <row>
        <entry><literal>"body-images"</literal></entry>
        <entry>
         The server supports images in the notifications.
        </entry>
       </row>
       <row>
        <entry><literal>"body-markup"</literal></entry>
        <entry>
         Supports markup in the body text. If marked up text is sent
         to a server that does not give this cap, the markup will show
         through as regular text so must be stripped clientside.
        </entry>
       </row>
       <row>
        <entry><literal>"icon-multi"</literal></entry>
        <entry>
         The server will render an animation of all the frames in a given
         image array. The client may still specify multiple frames even if
         this cap and/or <literal>"icon-static"</literal> is missing, however
         the server is free to ignore them and use only the primary frame.
        </entry>
       </row>
       <row>
        <entry><literal>"icon-static"</literal></entry>
        <entry>
         Supports display of exactly 1 frame of any given image array.
         This value is mutually exclusive with
         <literal>"icon-multi"</literal>, it is a protocol error for the
         server to specify both.
        </entry>
       </row>
       <row>
        <entry><literal>"sound"</literal></entry>
        <entry>
         The server supports sounds on notifications. If returned, the
         server must support the <literal>"sound-file"</literal> and
         <literal>"suppress-sound"</literal> hints.
        </entry>
       </row>
      </tbody>
     </tgroup>
    </table>
    <para>
     New vendor-specific caps may be specified as long as they start with
     <literal>"x-<replaceable>vendor</replaceable>"</literal>. For instance,
     <literal>"x-gnome-foo-cap"</literal>. Capability names must not
     contain spaces. They are limited to alpha-numeric characters and dashes
     (<literal>"-"</literal>).
    </para>
   </sect3>

   <sect3 id="command-notify">
    <title><literal>org.freedesktop.Notifications.Notify</literal></title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>UINT32
       <function>org.freedesktop.Notifications.Notify</function>
      </funcdef>
      <paramdef>STRING <parameter>app_name</parameter></paramdef>
      <paramdef>UINT32 <parameter>replaces_id</parameter></paramdef>
      <paramdef>STRING <parameter>app_icon</parameter></paramdef>
      <paramdef>STRING <parameter>summary</parameter></paramdef>
      <paramdef>STRING <parameter>body</parameter></paramdef>
      <paramdef>ARRAY <parameter>actions</parameter></paramdef>
      <paramdef>DICT <parameter>hints</parameter></paramdef>
      <paramdef>INT32 <parameter>expire_timeout</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     Sends a notification to the notification server.
    </para>
    <table>
     <title>Notify Parameters</title>
     <tgroup cols="3">
      <thead>
       <row>
        <entry>Name</entry>
        <entry>Type</entry>
        <entry>Description</entry>
       </row>
      </thead>
      <tbody valign="top">
       <row>
        <entry><parameter>app_name</parameter></entry>
        <entry>STRING</entry>
        <entry>
         The optional name of the application sending the notification.
         Can be blank.
        </entry>
       </row>
       <row>
        <entry><parameter>replaces_id</parameter></entry>
        <entry>UINT32</entry>
        <entry>
         The optional notification ID that this notification replaces. The
         server must atomically (ie with no flicker or other visual cues)
         replace the given notification with this one. This allows clients to
         effectively modify the notification while it's active. A value of
         value of 0 means that this notification won't replace any
         existing notifications.
        </entry>
       </row>
       <row>
        <entry><parameter>app_icon</parameter></entry>
        <entry>STRING</entry>
        <entry>
         The optional program icon of the calling application. See <xref linkend="icons-and-images"/>.
         Can be an empty string, indicating no icon.
        </entry>
       </row>
       <row>
        <entry><parameter>summary</parameter></entry>
        <entry>STRING</entry>
        <entry>The summary text briefly describing the notification.</entry>
       </row>
       <row>
        <entry><parameter>body</parameter></entry>
        <entry>STRING</entry>
        <entry>The optional detailed body text. Can be empty.</entry>
       </row>
       <row>
        <entry><parameter>actions</parameter></entry>
        <entry>ARRAY</entry>
        <entry>
         Actions are sent over as a list of pairs. Each even element in
         the list (starting at index 0) represents the identifier for the
         action. Each odd element in the list is the localized string
         that will be displayed to the user.
        </entry>
       </row>
       <row>
        <entry><parameter>hints</parameter></entry>
        <entry>DICT</entry>
        <entry>
         Optional hints that can be passed to the server from the client
         program. Although clients and servers should never assume each other
         supports any specific hints, they can be used to pass along
         information, such as the process PID or window ID, that the server
         may be able to make use of. See <xref linkend="hints"/>. Can be
         empty.
        </entry>
       </row>
       <row>
        <entry><parameter>expire_timeout</parameter></entry>
        <entry>INT32</entry>
        <entry>
         <para>
          The timeout time in milliseconds since the display of the notification at
          which the notification should automatically close.
         </para>
         <para>
          If -1, the notification's expiration time is dependent on the
          notification server's settings, and may vary for the type of
          notification.

          If 0, never expire.
         </para>
        </entry>
       </row>
      </tbody>
     </tgroup>
    </table>
    <para>
     If <parameter>replaces_id</parameter> is 0, the return value is a
     UINT32 that represent the notification. It is unique, and will not be
     reused unless a <constant>MAXINT</constant> number of notifications
     have been generated. An acceptable implementation may just use an
     incrementing counter for the ID. The returned ID is always greater than
     zero. Servers must make sure not to return zero as an ID.
    </para>
    <para>
     If <parameter>replaces_id</parameter> is not 0, the returned value
     is the same value as <parameter>replaces_id</parameter>.
    </para>
   </sect3>

   <sect3 id="command-close-notification">
    <title><literal>org.freedesktop.Notifications.CloseNotification</literal></title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>void
       <function>org.freedesktop.Notifications.CloseNotification</function>
      </funcdef>
      <paramdef>UINT32 id</paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     Causes a notification to be forcefully closed and removed from the user's
     view. It can be used, for example, in the event that what the
     notification pertains to is no longer relevant, or to cancel a
     notification with no expiration time.
    </para>
    <para>
     The <literal>NotificationClosed</literal> signal is emitted by this
     method.
    </para>
    <para>
     If the notification no longer exists, an empty D-BUS Error message is
     sent back.
    </para>
   </sect3>

   <sect3 id="command-get-server-information">
    <title><literal>org.freedesktop.Notifications.GetServerInformation</literal></title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>
       void
       <function>org.freedesktop.Notifications.GetServerInformation</function>
      </funcdef>
      <paramdef>out STRING <parameter>name</parameter></paramdef>
      <paramdef>out STRING <parameter>vendor</parameter></paramdef>
      <paramdef>out STRING <parameter>version</parameter></paramdef>
      <paramdef>out STRING <parameter>spec_version</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This message returns the information on the server. Specifically,
     the server name, vendor, and version number.
    </para>
    <table>
     <title>GetServerInformation Return Values</title>
     <tgroup cols="2">
      <thead>
       <row>
        <entry>Name</entry>
        <entry>Type</entry>
        <entry>Description</entry>
       </row>
      </thead>
      <tbody valign="top">
       <row>
        <entry><parameter>name</parameter></entry>
        <entry>STRING</entry>
        <entry>The product name of the server.</entry>
       </row>
       <row>
        <entry><parameter>vendor</parameter></entry>
        <entry>STRING</entry>
        <entry>
         The vendor name. For example, "KDE," "GNOME,"
         "freedesktop.org," or "Microsoft."
        </entry>
       </row>
       <row>
        <entry><parameter>version</parameter></entry>
        <entry>STRING</entry>
        <entry>The server's version number.</entry>
       </row>
       <row>
        <entry><parameter>spec_version</parameter></entry>
        <entry>STRING</entry>
        <entry>The specification version the server is compliant with.</entry>
       </row>
      </tbody>
     </tgroup>
    </table>
   </sect3>
  </sect2>

  <sect2 id="signals">
   <title>Signals</title>

   <sect3 id="signal-notification-closed">
    <title><literal>org.freedesktop.Notifications.NotificationClosed</literal></title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>
       <function>org.freedesktop.Notifications.NotificationClosed</function>
      </funcdef>
      <paramdef>UINT32 <parameter>id</parameter></paramdef>
      <paramdef>UINT32 <parameter>reason</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     A completed notification is one that has timed out, or has been
     dismissed by the user.
    </para>
    <table>
     <title>NotificationClosed Parameters</title>
     <tgroup cols="2">
      <thead>
       <row>
        <entry>Name</entry>
        <entry>Type</entry>
        <entry>Description</entry>
       </row>
      </thead>
      <tbody valign="top">
       <row>
        <entry><parameter>id</parameter></entry>
        <entry>UINT32</entry>
        <entry>The ID of the notification that was closed.</entry>
       </row>
       <row>
        <entry><parameter>reason</parameter></entry>
        <entry>UINT32</entry>
        <entry>
         <para>The reason the notification was closed.</para>
         <para>1 - The notification expired.</para>
         <para>2 - The notification was dismissed by the user.</para>
         <para>3 - The notification was closed by a call to
               <literal>CloseNotification</literal>.</para>
         <para>4 - Undefined/reserved reasons.</para>
        </entry>
       </row>
      </tbody>
     </tgroup>
    </table>
    <para>
     The ID specified in the signal is invalidated
     <emphasis>before</emphasis> the signal is sent and may not be used
     in any further communications with the server.
    </para>
   </sect3>

   <sect3 id="signal-action-invoked">
    <title><literal>org.freedesktop.Notifications.ActionInvoked</literal></title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>
       <function>org.freedesktop.Notifications.ActionInvoked</function>
      </funcdef>
      <paramdef>UINT32 <parameter>id</parameter></paramdef>
      <paramdef>STRING <parameter>action_key</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This signal is emitted when one of the following occurs:
    </para>
    <itemizedlist>
     <listitem>
      <para>
       The user performs some global "invoking" action upon a notification.
       For instance, clicking somewhere on the notification itself.
      </para>
     </listitem>
     <listitem>
      <para>
       The user invokes a specific action as specified in the original
       Notify request. For example, clicking on an action button.
      </para>
     </listitem>
    </itemizedlist>
    <table>
     <title>ActionInvoked Parameters</title>
     <tgroup cols="2">
      <thead>
       <row>
        <entry>Name</entry>
        <entry>Type</entry>
        <entry>Description</entry>
       </row>
      </thead>
      <tbody valign="top">
       <row>
        <entry><parameter>id</parameter></entry>
        <entry>UINT32</entry>
        <entry>
         The ID of the notification emitting the ActionInvoked signal.
        </entry>
       </row>
       <row>
        <entry><parameter>action_key</parameter></entry>
        <entry>STRING</entry>
        <entry>
         The key of the action invoked. These match the keys sent over
         in the list of actions.
        </entry>
       </row>
      </tbody>
     </tgroup>
    </table>
    <note>
     <para>
      Clients should not assume the server will generate this signal. Some
      servers may not support user interaction at all, or may not support
      the concept of being able to "invoke" a notification.
     </para>
    </note>
   </sect3>
  </sect2>
 </sect1>
</article>