The `widget` module provides your add-on with a simple user interface that is
consistent with other add-ons and blends in well with Firefox.
"Widgets" are small pieces of content that live in the Firefox 4
[add-on bar](https://developer.mozilla.org/en/The_add-on_bar).
They can be simple icons or complex web pages. You can attach
[panels](modules/sdk/panel.html) to them that open when they're
clicked, or you can define a custom click handler to perform some other action,
like opening a web page in a tab.
There are a few advantages to using widgets over an ad hoc user interface.
First, your users will be accustomed to interacting with add-ons via widgets and
the add-on bar. Second, it allows Firefox to treat your interface as a
first-class citizen. For example, in the future Firefox may allow the user to
drag widgets from the add-on bar to other toolbars. By exposing your interface
as a widget, your add-on would automatically inherit such functionality.
## Creation and Content ##
Widgets can contain images or arbitrary web content. You can include this
content inline as a string by using the `content` property, or point to content
using a URL with the `contentURL` property.
Upon creation, the widget is automatically added to the add-on bar.
You can set the width of a widget, but the height is fixed so as to fit in the
add-on bar. If the content is an image, it is automatically scaled to be 16x16
pixels.
For example, this widget contains an image, so it looks like a simple icon:
require("sdk/widget").Widget({
id: "mozilla-icon",
label: "My Mozilla Widget",
contentURL: "http://www.mozilla.org/favicon.ico"
});
You can make `contentURL` point to an HTML or icon file which you have
packaged inside your add-on. Just save the file in your add-on's `data`
directory, and reference it using the `data.url()` method of the
[`self`](modules/sdk/self.html) module:
var data = require("sdk/self").data;
require("sdk/widget").Widget({
id: "my-widget",
label: "My Widget",
contentURL: data.url("my-content.html")
});
This widget contains an entire web page:
require("sdk/widget").Widget({
id: "hello-display",
label: "My Hello Widget",
content: "Hello!",
width: 50
});
Widgets are quite small by default, so this example used the `width` property to
grow it in order to show all the text.
## Scripting Widget Content ##
To interact with the widget's content you need to load a separate script into
the panel. In the SDK these scripts are called "content scripts" because
they're explicitly used for interacting with web content.
While content scripts can access the content they're attached to, they can't
use the SDK's APIs. So implementing a complete solution usually means you
have to send messages between the content script and the main add-on code.
* You can specify one or more content scripts to load into the widget using the
`contentScript` or `contentScriptFile` options to the
[`Widget()` constructor](modules/sdk/widget.html#Widget(options)).
* You can communicate with the script using either the
[`postMessage()`](dev-guide/guides/content-scripts/using-postmessage.html)
API or (preferably, usually) the
[`port`](dev-guide/guides/content-scripts/using-port.html) API.
Unless your content script is extremely simple and consists only of a
static string, don't use contentScript: if you do, you may
have problems getting your add-on approved on AMO.
Instead, keep the script in a separate file and load it using
contentScriptFile. This makes your code easier to maintain,
secure, debug and review.
For example, suppose we want to implement a media player as an add-on.
We could implement the main user interface as a widget hosting an array
of buttons to control play/pause/stop functions.
We can then use a content script to listen for clicks on those buttons.
But because content scripts can't use the SDK's APIs, we'll want the
content script to send messages to the main add-on code, which can then
implement the media player functions using the SDK.
The widget's content is specified using HTML like this:
<html>
<body>
<img src="play.png" id="play-button">
<img src="pause.png" id="pause-button">
<img src="stop.png" id="stop-button">
</body>
</html>
We just include three icons, and assign an ID to each one. This HTML file,
and the icon files it references, are saved in the add-on's `data`
directory.
Next, we write a content script that listens for click events on each icon
and sends the corresponding message to the main add-on code:
var play_button = document.getElementById("play-button");
play_button.onclick = function() {
self.port.emit("play");
}
var pause_button = document.getElementById("pause-button");
pause_button.onclick = function() {
self.port.emit("pause");
}
var stop_button = document.getElementById("stop-button");
stop_button.onclick = function() {
self.port.emit("stop");
}
We save this file in the add-on's `data` directory as "button-script.js".
Finally. in the add-on's "main.js" file, we create the widget, assign it
the HTML file and the content script, and listen for events from the content
script:
const widgets = require("sdk/widget");
const data = require("sdk/self").data;
var player = widgets.Widget({
id: "player",
width: 72,
label: "Player",
contentURL: data.url("buttons.html"),
contentScriptFile: data.url("button-script.js")
});
player.port.on("play", function() {
console.log("playing");
});
player.port.on("pause", function() {
console.log("pausing");
});
player.port.on("stop", function() {
console.log("stopping");
});
To learn much more about content scripts, see the
[Working with Content Scripts](dev-guide/guides/content-scripts/index.html)
guide.
Scripting Trusted Widget Content
We've already seen that you can package HTML files in your add-on's `data`
directory and use them to define the widget's content. We can call this
"trusted" content, because unlike content loaded from a source outside the
add-on, the add-on author knows exactly what it's doing. To
interact with trusted content you don't need to use content scripts:
you can just include a script from the HTML file in the normal way, using
`script` tags.
Like a content script, these scripts can communicate with the add-on code
using the
[`postMessage()`](dev-guide/guides/content-scripts/using-postmessage.html)
API or the
[`port`](dev-guide/guides/content-scripts/using-port.html) API.
The crucial difference is that these scripts access the `postMessage`
and `port` objects through the `addon` object, whereas content scripts
access them through the `self` object.
To show the difference, convert the `player` add-on above
to use normal page scripts instead of content scripts.
First, in the content script, change `self` to `addon`, and wrap it in a
function:
function init() {
var play_button = document.getElementById("play-button");
play_button.onclick = function() {
addon.port.emit("play");
}
var pause_button = document.getElementById("pause-button");
pause_button.onclick = function() {
addon.port.emit("pause");
}
var stop_button = document.getElementById("stop-button");
stop_button.onclick = function() {
addon.port.emit("stop");
}
}
Next, add a `script` tag to reference "button-script.js", and
call its `init()` function on load:
<html>
<head>
<script src="button-script.js"></script>
</head>
<body onLoad="init()">
<img src="play.png" id="play-button">
<img src="pause.png" id="pause-button">
<img src="stop.png" id="stop-button">
</body>
</html>
Finally, remove the line attaching the content script from "main.js":
const widgets = require("sdk/widget");
const data = require("sdk/self").data;
var player = widgets.Widget({
id: "player",
width: 72,
label: "Player",
contentURL: data.url("buttons.html")
});
player.port.emit("init");
player.port.on("play", function() {
console.log("playing");
});
player.port.on("pause", function() {
console.log("pausing");
});
player.port.on("stop", function() {
console.log("stopping");
});
## Attaching Panels to Widgets ##
You can supply a [panel](modules/sdk/panel.html) to the widget's
constructor: if you do this, the panel is automatically displayed when the
user clicks the widget.
data = require("sdk/self").data
var clockPanel = require("sdk/panel").Panel({
width:215,
height:160,
contentURL: data.url("clock.html")
});
require("sdk/widget").Widget({
id: "open-clock-btn",
label: "Clock",
contentURL: data.url("History.png"),
panel: clockPanel
});
Note that this is, at the moment, the only way you can attach a panel to a widget.
You must supply the panel in the widget's constructor for it to work. If you
assign the panel to the widget after construction, the panel can still be shown
but will not be anchored to the widget:
data = require("sdk/self").data
var clockPanel = require("sdk/panel").Panel({
width:215,
height:160,
contentURL: data.url("clock.html")
});
widget = require("sdk/widget").Widget({
id: "open-clock-btn",
label: "Clock",
contentURL: data.url("History.png")
});
widget.panel = clockPanel;
// Will not be anchored
widget.panel.show();
Also, if you try to call `panel.show()` inside your widget's `click` event
listener, the panel will not be anchored:
data = require("sdk/self").data
var clockPanel = require("sdk/panel").Panel({
width:215,
height:160,
contentURL: data.url("clock.html")
});
require("sdk/widget").Widget({
id: "open-clock-btn",
label: "Clock",
contentURL: data.url("History.png"),
panel: clockPanel,
onClick: function() {
// Will not be anchored
this.panel.show();
}
});
See [bug 638142](https://bugzilla.mozilla.org/show_bug.cgi?id=638142).
## Private Windows ##
If your add-on has not opted into private browsing, then your widget will
not appear in any private browser windows.
To learn more about private windows, how to opt into private browsing, and how
to support private browsing, refer to the
[documentation for the `private-browsing` module](modules/sdk/private-browsing.html).
## Examples ##
For conciseness, these examples create their content scripts as strings and use
the `contentScript` property. In your own add-ons, you will probably want to
create your content scripts in separate files and pass their URLs using the
`contentScriptFile` property. See
[Working with Content Scripts](dev-guide/guides/content-scripts/index.html) for more
information.
var widgets = require("sdk/widget");
// A basic click-able image widget.
widgets.Widget({
id: "google-link",
label: "Widget with an image and a click handler",
contentURL: "http://www.google.com/favicon.ico",
onClick: function() {
require("sdk/tabs").activeTab.url = "http://www.google.com/";
}
});
// A widget that changes display on mouseover.
widgets.Widget({
id: "mouseover-effect",
label: "Widget with changing image on mouseover",
contentURL: "http://www.yahoo.com/favicon.ico",
onMouseover: function() {
this.contentURL = "http://www.bing.com/favicon.ico";
},
onMouseout: function() {
this.contentURL = "http://www.yahoo.com/favicon.ico";
}
});
// A widget that updates content on a timer.
widgets.Widget({
id: "auto-update-widget",
label: "Widget that updates content on a timer",
content: "0",
contentScript: 'setTimeout(function() {' +
' document.body.innerHTML++;' +
'}, 2000)',
contentScriptWhen: "ready"
});
// A widget created with a specified width, that grows.
var myWidget = widgets.Widget({
id: "widget-effect",
label: "Wide widget that grows wider on a timer",
content: "I'm getting longer.",
width: 50,
});
require("sdk/timers").setInterval(function() {
myWidget.width += 10;
}, 1000);
// A widget communicating bi-directionally with a content script.
var widget = widgets.Widget({
id: "message-test",
label: "Bi-directional communication!",
content: "bar",
contentScriptWhen: "ready",
contentScript: 'self.on("message", function(message) {' +
' alert("Got message: " + message);' +
'});' +
'self.postMessage("ready");',
onMessage: function(message) {
if (message == "ready")
widget.postMessage("me too");
}
});
@class
Represents a widget object.
@constructor {options}
Creates a new widget. The widget is immediately added to the add-on bar.
@param options {object}
An object with the following keys:
@prop label {string}
A required string description of the widget used for accessibility,
title bars, and error reporting.
@prop id {string}
Mandatory string used to identify your widget in order to save its
location when the user moves it in the browser.
This string has to be unique and must not be changed over time.
@prop [content] {string}
An optional string value containing the displayed content of the widget.
It may contain HTML. Widgets must have either the `content` property or the
`contentURL` property set.
If the content is an image, it is automatically scaled to be 16x16 pixels.
@prop [contentURL] {string}
An optional string URL to content to load into the widget. This can be
[local content](dev-guide/guides/content-scripts/index.html) or remote
content, an image or web content. Widgets must have either the `content`
property or the `contentURL` property set.
If the content is an image, it is automatically scaled to be 16x16 pixels.
@prop [panel] {Panel}
An optional [panel](modules/sdk/panel.html) to open when the
user clicks on the widget. Note: If you also register a "click" listener,
it will be called instead of the panel being opened. However, you can show
the panel from the listener by calling `this.panel.show()`.
@prop [width] {integer}
Optional width in pixels of the widget. If not given, a default width is
used.
@prop [onClick] {function}
Include this to listen to the widget's `click` event.
@prop [onMessage] {function}
Include this to listen to the widget's `message` event.
@prop [onMouseover] {function}
Include this to listen to the widget's `mouseover` event.
@prop [onMouseout] {function}
Include this to listen to the widget's `mouseout` event.
@prop [onAttach] {function}
Include this to listen to the widget's `attach` event.
@prop [tooltip] {string}
Optional text to show when the user's mouse hovers over the widget. If not
given, the `label` is used.
@prop [allow] {object}
An optional object describing permissions for the content. It should
contain a single key named `script` whose value is a boolean that indicates
whether or not to execute script in the content. `script` defaults to true.
@prop [contentScriptFile] {string,array}
A local file URL or an array of local file URLs of content scripts to load.
Content scripts specified by this property are loaded *before* those
specified by the `contentScript` property.
@prop [contentScript] {string,array}
A string or an array of strings containing the texts of content scripts to
load. Content scripts specified by this property are loaded *after* those
specified by the `contentScriptFile` property.
@prop [contentScriptWhen="end"] {string}
When to load the content scripts. This may take one of the following
values:
* "start": load content scripts immediately after the document
element for the widget is inserted into the DOM, but before the DOM content
itself has been loaded
* "ready": load content scripts once DOM content has been loaded,
corresponding to the
[DOMContentLoaded](https://developer.mozilla.org/en/Gecko-Specific_DOM_Events)
event
* "end": load content scripts once all the content (DOM, JS, CSS,
images) for the widget has been loaded, at the time the
[window.onload event](https://developer.mozilla.org/en/DOM/window.onload)
fires
This property is optional and defaults to "end".
@prop [contentScriptOptions] {object}
Read-only value exposed to content scripts under `self.options` property.
Any kind of jsonable value (object, array, string, etc.) can be used here.
Optional.
@method
Removes the widget from the add-on bar.
@method
Sends a message to the widget's content scripts.
@param data {value}
The message to send.
The message can be any
JSON-serializable value.
@method
Registers an event listener with the widget.
@param type {string}
The type of event to listen for.
@param listener {function}
The listener function that handles the event.
@method
Unregisters an event listener from the widget.
@param type {string}
The type of event for which `listener` was registered.
@param listener {function}
The listener function that was registered.
@method
Retrieve a `WidgetView` instance of this widget relative to a browser window.
@param window {BrowserWindow}
The [BrowserWindow](modules/sdk/windows.html) instance to match.
@returns {WidgetView}
A `WidgetView` instance associated with the browser window. Any changes
subsequently applied to this object will only be applied to the widget
attached to that window.
@property {string}
The widget's label. Read-only.
@property {string}
A string containing the widget's content. It can contain HTML. Setting it
updates the widget's appearance immediately. However, if the widget was
created using `contentURL`, then this property is meaningless, and setting it
has no effect.
@property {string}
The URL of content to load into the widget. This can point to
local content loaded from your add-on's "data" directory or remote
content, an image or web content. Setting it updates the widget's appearance
immediately. However, if the widget was created using `content`, then this
property is meaningless, and setting it has no effect.
Setting the `contentURL` property will break the channel of communication
between this widget and any content scripts it contains. Messages sent from
the content script will no longer be received by the main add-on code, and
vice versa. This issue is currently tracked as
[bug 825434](https://bugzilla.mozilla.org/show_bug.cgi?id=825434).
@property {Panel}
A [panel](modules/sdk/panel.html) to open when the user clicks on
the widget.
@property {number}
The widget's width in pixels. Setting it updates the widget's appearance
immediately.
@property {string}
The text of the tooltip that appears when the user hovers over the widget.
@property {object}
A object describing permissions for the content. It contains a single key
named `script` whose value is a boolean that indicates whether or not to
execute script in the content.
@property {string,array}
A local file URL or an array of local file URLs of content scripts to load.
@property {string,array}
A string or an array of strings containing the texts of content scripts to
load.
@property {string}
When to load the content scripts. This may have one of the following
values:
* "start": load content scripts immediately after the document
element for the widget is inserted into the DOM, but before the DOM content
itself has been loaded
* "ready": load content scripts once DOM content has been loaded,
corresponding to the
[DOMContentLoaded](https://developer.mozilla.org/en/Gecko-Specific_DOM_Events)
event
* "end": load content scripts once all the content (DOM, JS, CSS,
images) for the widget has been loaded, at the time the
[window.onload event](https://developer.mozilla.org/en/DOM/window.onload)
fires
@property {object}
Read-only value exposed to content scripts under `self.options` property.
Any kind of jsonable value (object, array, string, etc.) can be used here.
Optional.
@property {EventEmitter}
[EventEmitter](modules/sdk/deprecated/events.html) object that allows you to:
* send events to the content script using the `port.emit` function
* receive events from the content script using the `port.on` function
See the guide to
communicating using port for details.
@event
This event is emitted when a browser window is opened and a new `WidgetView`
object is created. If the widget has a content script, this event is fired
only when the content script is applied according to the `contentScriptWhen`
attribute.
@argument {WidgetView}
The related `WidgetView` object.
@event
This event is emitted when the widget is clicked.
@argument {WidgetView}
Listeners are passed a single argument which is the `WidgetView` that triggered the click event.
@event
If you listen to this event you can receive message events from content
scripts associated with this widget. When a content script posts a
message using `self.postMessage()`, the message is delivered to the add-on
code in the widget's `message` event.
@argument {value}
Listeners are passed a single argument which is the message posted
from the content script. The message can be any
JSON-serializable value.
@event
This event is emitted when the user moves the mouse over the widget.
@event
This event is emitted when the user moves the mouse away from the widget.
@class
Represents a widget instance specific to one browser window.
Anything you do to an instance of this object will only be applied to the
instance attached to its browser window: widget instances attached to other
browser windows will be unaffected.
By contrast, any changes you make to an instance of the normal `Widget` class
will be applied across all browser windows.
This class has all the same methods, attributes and events as the `Widget`
class except for the `getView` method and the `attach` event.
In this example `WidgetView` is used to display different content for
`http` and `https` schemes:
// A widget that update its content specifically to each window.
var tabs = require("sdk/tabs");
var windows = require("sdk/windows").browserWindows;
var widget = require("sdk/widget").Widget({
id: "window-specific-test",
label: "Widget with content specific to each window",
content: " ",
width: 50
});
// Observe tab switch or document changes in each existing tab:
function updateWidgetState(tab) {
var view = widget.getView(tab.window);
if (!view) return;
// Update widget displayed text:
view.content = tab.url.match(/^https/) ? "Secured" : "Unsafe";
}
tabs.on('ready', updateWidgetState);
tabs.on('activate', updateWidgetState);
@method
Removes the widget view from the add-on bar.
@method
Sends a message to the widget view's content scripts.
@param data {value}
The message to send. The message can be any
JSON-serializable value.
@method
Registers an event listener with the widget view.
@param type {string}
The type of event to listen for.
@param listener {function}
The listener function that handles the event.
@method
Unregisters an event listener from the widget view.
@param type {string}
The type of event for which `listener` was registered.
@param listener {function}
The listener function that was registered.
@property {string}
The widget view's label. Read-only.
@property {string}
A string containing the widget view's content. It can contain HTML.
Setting it updates the widget view's appearance immediately. However,
if the widget view was created using `contentURL`, then this property
is meaningless, and setting it has no effect.
@property {string}
The URL of content to load into the widget. This can point to
local content loaded from your add-on's "data" directory or remote
content, an image or web content. Setting it updates the widget's appearance
immediately. However, if the widget was created using `content`, then this
property is meaningless, and setting it has no effect.
Setting the `contentURL` property will break the channel of communication
between this widget and any content scripts it contains. Messages sent from
the content script will no longer be received by the main add-on code, and
vice versa. This issue is currently tracked as
[bug 825434](https://bugzilla.mozilla.org/show_bug.cgi?id=825434).
@property {Panel}
A [panel](modules/sdk/panel.html) to open when the user clicks on
the widget view.
@property {number}
The widget view's width in pixels. Setting it updates the widget view's
appearance immediately.
@property {string}
The text of the tooltip that appears when the user hovers over the widget
view.
@property {object}
A object describing permissions for the content. It contains a single key
named `script` whose value is a boolean that indicates whether or not to
execute script in the content.
@property {string,array}
A local file URL or an array of local file URLs of content scripts to load.
@property {string,array}
A string or an array of strings containing the texts of content scripts to
load.
@property {string}
When to load the content scripts. This may have one of the following
values:
* "start": load content scripts immediately after the document
element for the widget view is inserted into the DOM, but before the DOM
content itself has been loaded
* "ready": load content scripts once DOM content has been loaded,
corresponding to the
[DOMContentLoaded](https://developer.mozilla.org/en/Gecko-Specific_DOM_Events)
event
* "end": load content scripts once all the content (DOM, JS, CSS,
images) for the widget view has been loaded, at the time the
[window.onload event](https://developer.mozilla.org/en/DOM/window.onload)
fires
@property {object}
Read-only value exposed to content scripts under `self.options` property.
Any kind of jsonable value (object, array, string, etc.) can be used here.
Optional.
@property {EventEmitter}
[EventEmitter](modules/sdk/deprecated/events.html) object that allows you to:
* send events to the content script using the `port.emit` function
* receive events from the content script using the `port.on`
See the guide to
communicating using port for details.
@event
The `detach` event is fired when the widget view is removed from its related
window.
This can occur if the window is closed, Firefox exits, or the add-on is
disabled.
@event
This event is emitted when the widget view is clicked.
@event
If you listen to this event you can receive message events from content
scripts associated with this widget view. When a content script posts a
message using `self.postMessage()`, the message is delivered to the add-on
code in the widget view's `message` event.
@argument {value}
Listeners are passed a single argument which is the message posted
from the content script. The message can be any
JSON-serializable value.
@event
This event is emitted when the user moves the mouse over the widget view.
@event
This event is emitted when the user moves the mouse away from the widget view.