Gadgets API

Gadgets XML Reference

This is the reference for the gadget spec XML.

You can see the JavaScript reference here.

Contents

  1. ModulePrefs Elements and Attributes
  2. User Preferences
  3. Content Section
  4. JavaScript Reference
    1. Feature-Specific JavaScript Libraries

ModulePrefs Elements and Attributes

The <ModulePrefs> section in the XML file specifies characteristics of the gadget, such as title, author, preferred sizing, and so on. For example:

<Module>
<ModulePrefs title="Developer Forum" title_url="http://groups.google.com/group/Google-Gadgets-API"
height="200" author="Jane Smith" author_email="xxx@google.com"/>
<Content ...>
... content ...
</Content>
</Module>

The users of your gadget cannot change these attributes.

<ModulePrefs> serves as a container element for all metadata, features, and processing rules. For nested element descriptions, see their individual sections below. This section summarizes the elements and attributes in <ModulePrefs>. In the sections below, the level of nesting is indicated by slashes. For example, /ModulePrefs/Locale describes the <Locale> element that is nested inside the <ModulePrefs> element. This might appear in a gadget specification as follows:

<ModulePrefs>
<Locale lang="en" country="us" /> <Locale lang="ja" country="jp" /> </ModulePrefs>

ModulePrefs

The following table lists the <ModulePrefs> attributes that are supported in all containers. See your container documentation for any container-specific <ModulePrefs> attributes.

Attribute Description
title Optional string that provides the title of the gadget. This title is displayed in the gadget title bar on iGoogle. If this string contains user preference substitution variables and you are planning to submit your gadget to the iGoogle content directory, you should also provide a directory_title for directory display.
title_url Optional string that provides a URL that the gadget title links to. For example, you could link the title to a webpage related to the gadget.
description Optional string that describes the gadget.
author Optional string that lists the author of the gadget.
author_email Optional string that provides the gadget author's email address. You can use any email system, but you should not use a personal email address because of spam. One approach is to use an email address of the form helensmith.feedback+coolgadget@gmail.com in your gadget spec.

Gmail drops everything after the plus sign (+), so this email address is interpreted as helensmith.feedback@gmail.com.

You can create a Gmail account here.
screenshot Optional string that gives the URL of a gadget screenshot. This must be an image on a public web site that is not blocked by robots.txt. PNG is the preferred format, though GIF and JPG are also acceptable. Gadget screenshots should be 280 pixels wide. The height of the screenshot should be the "natural" height of the gadget when it's in use.
thumbnail Optional string that gives the URL of a gadget thumbnail. This must be an image on a public web site that is not blocked by robots.txt. PNG is the preferred format, though GIF and JPG are also acceptable. Gadget thumbnails should be 120x60 pixels.

ModulePrefs/Require and ModulePrefs/Optional

The <Require> and <Optional> elements declare feature dependencies of the gadget.

Attributes:

  • "feature" -- The name of the feature. Required

Examples:

<Require feature="dynamic-height"/>
<Optional feature="shareable-prefs"/>

ModulePrefs/Require/Param and ModulePrefs/Optional/Param

These elements provide configuration parameters for a feature.

Attributes:

  • "name" -- The name of the parameter. Required.

ModulePrefs/Preload

The <Preload> element instructs the container to fetch data from a remote source during the gadget rendering process. This element is used in conjunction with makeRequest(), which fetches data from a remote server.

For example, suppose you have a request that looks like this:

gadgets.io.makeRequest("http://www.example.com", response, params);

You can preload the content at http://www.example.com by adding a <Preload> tag to your gadget's <ModulePrefs> section:

<ModulePrefs title="Demo Preloads" description="Demo Preloads">
  <Preload href="http://www.example.com" />
</ModulePrefs>

When your gadget executes the makeRequest() call, this content is returned instantly, without needing to hit your server again.

You use <Preload> to reduce latency for gadgets that use makeRequest() to fetch data from remote servers.

Attributes:

  • "href" -- A URL specifiying the location of the data to prefetch. Required.
  • "authz" -- The authentication type to use for making this request. Valid values are "none" (default), "signed", and "oauth". Optional.

These attributes map to the authorization parameters in the makeRequest() query string:

Attribute Description
oauth_service_name The nickname the gadget uses to refer to the OAuth <Service> element from its XML spec. If unspecified, defaults to "". Maps to gadgets.io.RequestParameters.OAUTH_SERVICE_NAME.
oauth_token_name The nickname the gadget uses to refer to an OAuth token granting access to a particular resources. If unspecified, defaults to "". Gadgets can use multiple token names if they have access to multiple resources from the same service provider. For example, a gadget with access to a contact list and a calendar might use a token name of "contacts" to use the contact list token, and a contact list of "calendar" to use the calendar token. Maps to gadgets.io.RequestParameters.OAUTH_TOKEN_NAME.
oauth_request_token A service provider may be able to automatically provision a gadget with a request token that is preapproved for access to a resource. The gadget can use that token with the OAUTH_REQUEST_TOKEN parameter. This parameter is optional. Maps to gadgets.io.RequestParameters.OAUTH_REQUEST_TOKEN.
oauth_request_token_secret The secret corresponding to a preapproved request token. This parameter is optional. Maps to gadgets.io.RequestParameters.OAUTH_REQUEST_TOKEN_SECRET.
sign_owner Boolean that indicates whether the owner must be authenticated. If unspecified, defaults to "true". Maps to gadgets.io.RequestParameters.SIGN_OWNER.
sign_viewer Boolean that indicates whether the viewer must be authenticated. If unspecified, defaults to "true". Maps to gadgets.io.RequestParameters.SIGN_VIEWER.
views A comma-separated list of the view names that trigger the specified preload.

Note that all of the <Preload> attributes also apply to proxied content.

ModulePrefs/Icon

The <Icon> element specifies a 16px x 16px image that containers can associate with a particular gadget (for example, the container might display the icon next to the gadget's name in the left nav bar).

The content of the <Icon> tag can be one of the following:

  • An HTTP URL pointing to an image file on the web
  • Inlined base64-encoded image data.

Attributes:

  • "mode" -- The encoding used for the icon when embedding an image. Currently, only base64 is supported. Optional.
  • "type" -- The MIME of the embedded icon text. Optional.

Examples:

<ModulePrefs title="My gadget">
  <Icon>http://remote/favicon.ico</Icon>
</ModulePrefs>

<ModulePrefs title="My gadget">
  <Icon mode="base64" type="image/png">base64 encoded data</Icon>
</ModulePrefs>

ModulePrefs/Locale

The <Locale> element specifies the locales supported by your gadget. You can also use it to specify message bundles, as described in Gadgets and Internationalization.

Attributes:

  • "lang" -- The language associated with the locale. Optional.
  • "country" -- The country associated with the locale. Optional.
  • "messages" -- A URL that points to a message bundle. Message bundles are XML files that contain the translated strings for a given locale. For more information, see Gadgets and Internationalization. Optional.
  • "language_direction" -- The direction of the gadget. Optional. Its value can either be "rtl" (right-to-left) or "ltr" (left-to-right). The default is "ltr". This attribute lets you create gadgets that support both left-to-right and right-to-left languages. For more discussion of this topic, see Creating Bi-directional Gadgets. You can use the following substitution variables in conjunction with language_direction:
    • __BIDI_START_EDGE__: The value is "left" when the gadget is in LTR-mode and "right" when the gadget is in RTL-mode.
    • __BIDI_END_EDGE__: The value is "right" when the gadget is in LTR-mode and "left" when the gadget is in RTL-mode.
    • __BIDI_DIR__: The value of this variable is "ltr" when the gadget is in LTR-mode and "rtl" when the gadget is in RTL-mode.
    • __BIDI_REVERSE_DIR__: The value of this variable is "rtl" when the gadget is in LTR-mode and "ltr" when the gadget is in RTL-mode.

For example, this snippet specifies two different locales:

<ModulePrefs>
  <Locale lang="en" country="us" />
  <Locale lang="ja" country="jp" />
</ModulePrefs>

The "lang" (language) and "country" attributes are both optional, but you must have at least one of them for each <Locale>. If you omit either attribute, the value is equivalent to "*" and "ALL". If you specify a country and no language, it is assumed that your gadget supports all languages associated with the country. Likewise, if you specify a language and no country, it is assumed that your gadget supports all countries associated with the language.

The valid values for language are ISO639-1 two-digit language codes, and for country they are ISO 3166-1 alpha-2 codes.

There are a few exceptions to the usual language rules:

  • Simplified Chinese: lang="zh-cn" (typically for country="cn").
  • Traditional Chinese: lang="zh-tw" (typically for country="tw" or "hk", Taiwan or Hong Kong, respectively).

ModulePrefs/OAuth

The <OAuth> element defines a gadget's use of the OAuth proxy. For more information about implement OAuth in gadgets, see Writing OAuth Gadgets.

ModulePrefs/OAuth/Service

This element identifies a single OAuth service configuration.

Attributes:

  • "name" -- The name of the service (for example, "google"), used for referencing OAuth services at runtime. This parameter is optional, and if unspecified, defaults to "". Gadget developers specify which OAuth service they wish to use by passing the service name as a parameter to makeRequest().

ModulePrefs/OAuth/Service/Request and ModulePrefs/OAuth/Service/Access

Represents the OAuth request token and access token URLs. See the OAuth spec and Writing OAuth Gadgets for details.

Attributes:

  • "url" -- The URL for the endpoint.
  • "method" -- The HTTP verb to use for making the request. This parameter is optional. If unspecified, it defaults to POST.
  • "param_location" -- One of 3 possible locations in the request to the service where the OAuth parameters may be passed. You can use this value to specify the location of OAuth-related parameters. The possible values are:
    • "uri-query" -- OAuth parameters are passed in the query string.
    • "auth-header" -- OAuth parameters are passed in the Authorization header.
    • "post-body" -- OAuth parameters are passed in the body of the POST request.

These values correspond to the options described in the OAuth spec. The default value is "auth-header".

ModulePrefs/OAuth/Service/Authorization

The OAuth authorization URL.

User Preferences

Some gadgets need to give users a way of supplying user-specific information. For example, a weather gadget might require users to provide their postal codes. The user preferences (<UserPref>) section in the XML file describes the user input fields that are turned into user interface controls when the gadget runs.

The following table lists the <UserPref> attributes:

Attribute Description
name Required "symbolic" name of the user preference; displayed to the user during editing if no display_name is defined. Must contain only letters, number and underscores, i.e. the regular expression ^[a-zA-Z0-9_]+$. Must be unique.
display_name Optional string to display alongside the user preferences in the edit window. Must be unique.
urlparam Optional string to pass as the parameter name for content type="url".
datatype Optional string that indicates the data type of this attribute. Can be string, bool, enum, hidden (a string that is not visible or user editable), or list (dynamic array generated from user input). The default is string.
required Optional boolean argument (true or false) indicating whether this user preference is required. The default is false.
default_value Optional string that indicates a user preference's default value.

User preferences can be accessed from your gadget using the user preferences JavaScript API, for example:

<script type="text/javascript">
   var prefs = new _IG_Prefs();
   var someStringPref = prefs.getString("StringPrefName");
   var someIntPref = prefs.getInt("IntPrefName");
   var someBoolPref = prefs.getBool("BoolPrefName");
</script>

Enum Data Types

One of the values you can specify for the <UserPref> datatype attribute is enum. The enum data type is presented in the user interface as a menu of choices. You specify the contents of the menu using <EnumValue>.

For example, this <UserPref> lets users set the level of difficulty for a game. Each value that will appear in the menu (Easy, Medium, and Hard) is defined using an <EnumValue> tag.

<UserPref name="difficulty" 
     display_name="Difficulty"
     datatype="enum"
     default_value="4">
  <EnumValue value="3" display_value="Easy"/>
  <EnumValue value="4" display_value="Medium"/>
  <EnumValue value="5" display_value="Hard"/>
</UserPref>

The following table lists the <EnumValue> attributes:

Attribute Description
value Required string that provides a unique value. This value is displayed in the menu in the user preferences edit box unless a display_value is provided.
display_value Optional string that is displayed in the menu in the user preferences edit box. If you do not specify a display_value, the value is displayed in the user interface.

Content Section

The <Content> section defines the type of content, and either holds the content itself or has a reference to external content. The <Content> section is where the gadget attributes and user preferences are combined with programming logic and formatting information to become a running gadget. For more discussion on content types, see Choosing a Content Type.

The following table lists the <Content> attributes:

Attribute Description
type Optional string that gives the type of the content. The possible values are html and url. The default is html.
href String that provides a destination URL. This can apply to either a type="url" gadget or to proxied content.
view Optional string. Indicates in which view of the container the content should be displayed. A gadget can define multiple content sections, each of which can apply to a different view or views.
preferred_height The gadget's initial height, in pixels.
preferred_width The gadget's initial width, in pixels.

ModulePrefs/Content@href (Proxied Content)

Proxied content is a feature that lets you specify HTML content by URL for a particular view.

The target URL you specify for this feature should be valid HTML 4.01, XHTML 1.1, and so on. You should not specify an image or Flash URL, though you could wrap these things in HTML and then link to the HTML. Your target HTML content must include the <html>, <head>, and <body> tags.

For example, this gadget uses proxied content for the canvas view, and inline content for the home view:

<?xml version="1.0" encoding="UTF-8"?>
<Module>
  <ModulePrefs title="Proxied Content Example">
</ModulePrefs>
  <Content view="canvas" 
    href="http://gadget-doc-examples.googlecode.com/svn/trunk/opensocial-09/mycontent.html">
  </Content>
  <Content view="home">
    <![CDATA[
      Hello, home view!
    ]]>
  </Content>
</Module>

Proxied content uses the same attributes that apply to the <Preload> element. See ModulePrefs/Preload for details.

JavaScript Reference

You can see the JavaScript Reference here.

Including Feature-Specific JavaScript Libraries

To create a gadget that uses a particular feature, such as tabs or a Flash movie, you must include the feature library in your gadget spec using the <Require> tag (inside <ModulePrefs>). For example:

<ModulePrefs 
  title="My Tabbed Gadget">
  <Require feature="tabs"/>
</ModulePrefs> 

The gadgets.* API provides the following feature libraries:

Feature Library Description Syntax
setprefs Sets the value of a user preference programmatically. See Saving State for more information. <Require feature="setprefs"/>
dynamic-height Gives a gadget the ability to resize itself. See Managing Gadget Height for more information. <Require feature="dynamic-height"/>
settitle Sets a gadget's title programmatically. See Setting a Gadget's Title for more information. <Require feature="settitle"/>
tabs Adds a tabbed interface to a gadget. See Tabs for more information. <Require feature="tabs"/>
minimessage Displays a dismissable, temporary message inside a gadget. See MiniMessages for more information. <Require feature="minimessage"/>
flash Embeds a Flash movie (specifically, a .swf file) in a gadget. See Flash for more information. <Require feature="flash"/>
locked-domain The locked-domain library isolates your gadgets from other gadgets running on the same page. You can only use this feature with type="html" gadgets. We suggest that you add this feature requirement to your gadget if your gadget stores sensitive private user data. This feature is only supported on iGoogle and Google Calendar. Other gadget containers may not support this feature and will reject your gadget. <Require feature="locked-domain"/>

To see all of the methods supported by a given feature, see the JavaScript Reference.

 

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Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 3.0 License, and code samples are licensed under the Apache 2.0 License.

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