1. What Is an Extension Installer?
  2. Extension Manifests
    1. Extension Metadata
    2. Extension Hooks
    3. Extension Actions
  3. Inserting Installers in Waves
  4. Examples

What Is an Extension Installer?

An extension installer is a package consisting of one or more of the following parts:

  • Extension metadata, which describes information about the extension including what it does, who created it and the current version.
  • One or more hooks that describe how the extension interfaces with the client.
  • Actions, which declare what happens when a hook is triggered, such as inserting gadgets or adding participants and robots.

You reference an extension installer through a special XML file, called the Extension Manifest. You can add this extension manifest directly within the Wave client to an existing or new wave, where it behaves according to the extension's defined hooks and actions.

Extension Manifests

Extension manifests are XML files that define how extensions hook into the Google Wave Client and how they behave. Manifests contain three parts: metadata, hooks, and actions. The metadata tells Google Wave how to render the installer, hooks tell the client how and where the extension works within the client, and actions define what happens when the extension is used.

For example, the following extension installer will add a toolbar icon to the toolbar, and when that is clicked (the hook), it will insert a map gadget (the action):

    name="Map Gadget"
    description="Collaborate on a map of placemarks, paths, and shapes with other participants. Great for planning events and trips."> 
  <author name="Google"/> 
  <menuHook location="toolbar" text="Add Map Gadget"
    <insertGadget url=""/> 

(View this installer XML in the browser, or a wave with this installer)

This simple manifest declares that a <menuHook> extension should be installed on the wave client's toolbar by the statement location="toolbar". The <menuHook> tag also specifies a URL (iconUrl) for the icon to be added to the toolbar. Then, the hook specifies a child action <insertGadget> that will add the specified gadget to the wave upon initiation of the parent hook. You may implement multiple hooks and actions for the same extension.

Extension Metadata

Before specifying hooks and actions, an extension installer first describes various pieces of metadata. This information is primarily used for presenting the extension to users, such as rendering the installer as an installable puzzle piece in a wave.

The following attributes should be specified on the root <extension> tag:

  • name: the display title of the extension
  • description: about 2-3 sentences describing what the extension does - no more than 150 characters
  • infoUrl: a link to the site or location providing more information about the extension.
  • thumbnailUrl: an image, ideally 120*120px, which is displayed in the installer puzzle piece
  • version: the current version fo the extension. The wave server uses string comparison for version checking, so version numbers do not have to numerically increase, and it assumes "0" if the version is not specified.

The author should be specified using <author> children tags, with name and email attributes.

Extension Hooks

An extension hook defines how the extension hooks into a Google Wave client. As such, the wave client is responsible for implementing the hook. In theory, a hook could be implemented in different ways on different implementations of Google wave clients.

Menu Hook

menuHook indicates that the extension should insert a UI element within a menu in the wave client.

  • location: where to hook into the client — supports the following values:
    • toolbar indicates that the extension should be placed within the wave client toolbar and will appear as an icon.

    • newwavemenu indicates that the extension should be placed within the New Wave menu (as a suboption). New wave actions will create a wave automatically when clicked and all actions will subsequently act upon it.

  • text: specifies the text to display, which will show up as tooltip text if toolbar is specified as the extension's location, and will not be used otherwise.
  • iconUrl: specifies a 20*20px image, which will be displayed on the editing toolbar if toolbar is the location.

For example, this menuHook adds a suboption to the "New Wave" menu, and when the user installs and clicks the option, the client will create a new wave with the two participants on it.

<menuHook location="NewWaveMenu" text="New Friends Wave">
    <participant id=""/>
    <participant id=""/>

Regex Hook (Preview)

regexHook indicates that the extension should be triggered when the wave client finds a matching regular expression in the currently edited text. This is useful for firing actions when text is matched. For example, a regex hook can add a robot that processes matched content (e.g. emoticons, phone numbers, etc).

  • pattern: the pattern to match against while the user is editing a blip.

For example, this regexHook searches for smiley faces, and when it finds one, it prompts the user to add an emoticon robot:

<regexHook pattern="\:\)">
    <participant id=""/>

Note: This hook is in preview mode and currently only enabled on We look forward to hearing your feedback on this hook in the forum.

Saved Search Hook

savedSearchHook adds saved searches when the extension is installed, and is a special type of hook that does not actually get triggered by the user doing something in the client. This hook is particularly useful for making it easy to find waves associated with your extension, like those created by a robot ("").

  • name: specifies the name of the search in the navigation panel.
  • query: specifies the query to execute when the user selects the search.
  • color (optional): specifies a CSS-based html color attribute (e.g. #FF00FF or yellow), which becomes the background color of the search in the navigational panel, and the color of the label in the digest.

For example, this extension installs a saved search for unread waves:

<extension name="Unread Wave Search"
    description="Installs a saved search that shows all unread waves.">
  <savedSearchHook name="Show unread" query="is:unread"

Extension Actions

Each hook in turn defines one or more actions that act within a defined scope. The following actions are supported:

Add Participants

Adds participants to the current wave. Participants are specified via participant child elements whose id attribute specifies the participant's wave address.

For example, this extension creates a new wave with a chess playing robot.

<menuHook location="NewWaveMenu" text="New Chess Match"> 
    <participant id=""/>

Add Saved Search

Similar to SavedSearchHook, adds a new saved search to the search menu. Note that adding saved searches in this way will not automatically remove them when the extension is uninstalled. See Saved Search Hook for a list of acceptable attributes.

For example, this extension adds a saves search for chess games after the user first uses the gadget.

<menuHook location="toolbar" text="Add Chess Gadget"
  <addSavedSearch title="Chess Game" query="has:gadget ChessGame"

Annotate Selection

Applies an annotation to the current selection while in edit mode. The annotation key and value is specified with key and value attributes, respectively.

For example, this extension applies bold and strike-out styles to the selected text:

<menuHook location="toolbar" text="Boldicize"> 
  <annotateSelection key="style/fontWeight" value="bold"/>
  <annotateSelection key="style/fontStyle" value="italic"/>

For information about using this robot, read the Annotations section in the documentation, and the Responding to User Selection article.

Insert Gadget

Inserts a gadget at the current cursor location. The gadget url is specified via a url attribute.

For example, this extension inserts a chess gadget:

<menuHook location="toolbar" text="Add Chess Gadget"

Inserting Installers in Waves

Once you've created the installer XML, you will want to actually test it out and see how it works. To do that, you need to insert an installer element in the wave, and before you can do that, you must install a special extension, "Extension Installer Creator", that makes it easy to insert installer elements.

1. Install "Extension Installer Creator":

  • If you're using Wave Sandbox, you can install the extension from this gallery wave..
  • If you're using Wave Preview, you can install the extension from this gallery wave.

Once you're viewing the wave, just click "Install" on the installer.

2. Once you install the extension, you will see a toolbox on your editing toolbar while editing a blip. To insert an installer, click that toolbar icon, and paste the URL of your XML in the text box.

3. After clicking "OK", you will see an installer element in the wave, showing the information from your XML. If the installer does not load correctly, then check the XML and make sure that it is valid.

4. If you make changes to your installer XML and want to test the new XML, you will need to re-insert the installer with a random query parameter appended to the end of the URL, to avoid the wave using a cached copy of the XML. For more information on caching of installers, see this FAQ.

5. Once you're happy with the installer you can share it with your friends by adding them to the wave, or share it with the world by adding to the wave. If you want to share it in the extensions gallery, then submit it here.


The following are actual example installer XMLs that can show you how to use the actions and hooks described above.