Display a page with a Firefox extension

Can someone please tell me how to write a Firefox extension that displays a local HTML page (contai开发者_运维知识库ned in the extension) when a user opens a new tab or web page.

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You will need this function to read a file inside your addon

function Read(file)
{
    var ioService=Components.classes["@mozilla.org/network/io-service;1"]
        .getService(Components.interfaces.nsIIOService);
    var scriptableStream=Components
        .classes["@mozilla.org/scriptableinputstream;1"]
        .getService(Components.interfaces.nsIScriptableInputStream);

    var channel=ioService.newChannel(file,null,null);
    var input=channel.open();
    scriptableStream.init(input);
    var str=scriptableStream.read(input.available());
    scriptableStream.close();
    input.close();
    return str;
}

Then create an element and add the content of the HTML.

gBrowser.addEventListener("DOMContentLoaded", function(e) {
    var documentElement = e.originalTarget.defaultView.document;
    var div = documentElement.createElement("div");
    div.innerHTML = Read("chrome://extensioname/content/file.html");
    documentElement.body.appendChild(div);
});

Use e.originalTarget.defaultView.location.href to filter the pages you want this behavior.

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You may find some info at https://developer.mozilla.org/en/Observer_Notifications and https://developer.mozilla.org/en/Code_snippets/Progress_Listeners and https://developer.mozilla.org/En/Code_snippets/On_page_load .

To display HTML content inside XUL content (though you can also cause a pure XHTML dialog to open), you can use a XUL iframe

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If you override the BrowserOpenTab function you can make it open the page of your choice rather than about:blank. This could be a page provided by your extension; ideally you would implement an alternative about URI for it.