There are a variety of ways you can Install extensions and themes from web pages, including direct linking to the XPI files and using the InstallTrigger object.
Extension and web authors are encouraged to use the method described below to install XPIs, as it provides the best experience to users.
Let's go through this piece by piece. The HTML is the install link. The href attribute contains a direct link to the extension XPI file, this is what will show in the location bar when the link is moused over. Users can save the XPI file to disk easily by right clicking on the link and choosing "Save Link As..."
When the link is clicked it calls the function install passing the event object as the parameter.
The install first creates a parameter block:
This specifies the display name (Foo) for use in the confirmation dialog, the URL to the extension (which is the link href, recall), the Icon URL to display in the confirmation dialog, a hash of the xpi file contents (to protect against corrupted downloads), and a toString function which will allow this code to work with versions of Firefox 0.8 and earlier. You could also use the old style parameter block ({ "Foo": aEvent.target.href }) if you wanted - and didn't have an Icon to use for the confirmation dialog.
InstallTrigger.install is then called to install the item with the parameter block.
This last part is the most important - the install function must return false so that when the link is clicked, only the script is run, and the link href is not navigated to. If you omit this step, the user may see two installation dialogs—since you've effectively invoked two install requests, one from the InstallTrigger, one from trying to load the XPI file directly.
URL
The URL property specifies the URL of the XPI to install. This property is required.
IconURL
The IconURL property specifies an icon to be displayed in the installation dialog. This property is optional. If you do not specify an icon, the default icon will be used, usually a green puzzle piece. The icon can be any image format supported by Firefox, and should be 32x32 pixels in size.
Hash
The Hash property specifies a cryptographic hash of the XPI file contents. This is used to verify the downloaded file, to protect against a corrupted file being served by a mirror download server, for example. You can use any hash function supported by nsICryptoHash. The hash is specified as hash function:hash value, for example, sha1:28857e60d043447c5f4550853f2d40770b326a13.
toString()
The toString() property should return the XPI URL, for compatibility with Firefox browsers older than version 1.0, and other applications such as Seamonkey.
Extension and web authors are encouraged to use the method described below to install XPIs, as it provides the best experience to users.
Web Script Example
<script type="application/javascript">
<!--
function install (aEvent)
{
for (var a = aEvent.target; a.href === undefined;) a = a.parentNode;
var params = {
"Foo": { URL: aEvent.target.href,
IconURL: aEvent.target.getAttribute("iconURL"),
Hash: aEvent.target.getAttribute("hash"),
toString: function () { return this.URL; }
}
};
InstallTrigger.install(params);
return false;
}
-->
</script>
<a href="http://www.example.com/foo.xpi"
iconURL="http://www.example.com/foo.png"
hash="sha1:28857e60d043447c5f4550853f2d40770b326a13"
onclick="return install(event);">Install Extension!</a>
Let's go through this piece by piece. The HTML is the install link. The href attribute contains a direct link to the extension XPI file, this is what will show in the location bar when the link is moused over. Users can save the XPI file to disk easily by right clicking on the link and choosing "Save Link As..."
When the link is clicked it calls the function install passing the event object as the parameter.
The install first creates a parameter block:
var params = {
"Foo": { URL: aEvent.target.href,
IconURL: aEvent.target.getAttribute("iconURL"),
Hash: aEvent.target.getAttribute("hash"),
toString: function () { return this.URL; }
};
This specifies the display name (Foo) for use in the confirmation dialog, the URL to the extension (which is the link href, recall), the Icon URL to display in the confirmation dialog, a hash of the xpi file contents (to protect against corrupted downloads), and a toString function which will allow this code to work with versions of Firefox 0.8 and earlier. You could also use the old style parameter block ({ "Foo": aEvent.target.href }) if you wanted - and didn't have an Icon to use for the confirmation dialog.
InstallTrigger.install is then called to install the item with the parameter block.
return false;
This last part is the most important - the install function must return false so that when the link is clicked, only the script is run, and the link href is not navigated to. If you omit this step, the user may see two installation dialogs—since you've effectively invoked two install requests, one from the InstallTrigger, one from trying to load the XPI file directly.
Available Parameters for the install object
The InstallTrigger.install method accepts a JavaScript object as a parameter, with several properties on that object used to affect the install.URL
The URL property specifies the URL of the XPI to install. This property is required.
IconURL
The IconURL property specifies an icon to be displayed in the installation dialog. This property is optional. If you do not specify an icon, the default icon will be used, usually a green puzzle piece. The icon can be any image format supported by Firefox, and should be 32x32 pixels in size.
Hash
The Hash property specifies a cryptographic hash of the XPI file contents. This is used to verify the downloaded file, to protect against a corrupted file being served by a mirror download server, for example. You can use any hash function supported by nsICryptoHash. The hash is specified as hash function:hash value, for example, sha1:28857e60d043447c5f4550853f2d40770b326a13.
toString()
The toString() property should return the XPI URL, for compatibility with Firefox browsers older than version 1.0, and other applications such as Seamonkey.
This post first appeared on Java4you - Java Programming Tutorials, Examples,, please read the originial post: here
