firefox extension working on page load - firefox-addon

Question

I'm trying to create my first extension.
I've found this sample: http://blog.mozilla.org/addons/2009/01/28/how-to-develop-a-firefox-extension/
I need to get some html content on a specific page and write something in the same page, so I modified it and got what I needed (with javascript I added content in the table I want). But to view my content I have to launch the extension from the button on the status bar, while I would like to have it already active in the page as I load/reload it (with a check on the url so to have it working only on that page) but I can't have it automatically.
I tried to add linkTargetFinder.run(); on init area, but... nothing. Moreover the extension as an "autorun" but eve if active, I don0t see any change.
any working sample?
Thanks
Nadia
Here it is the code (I edited just the .js file), I commented a couple of test not working...
var linkTargetFinder = function () {
var prefManager = Components.classes["#mozilla.org/preferences-service;1"].getService(Components.interfaces.nsIPrefBranch);
return {
init : function () {
gBrowser.addEventListener("load", function () {
var autoRun = prefManager.getBoolPref("extensions.linktargetfinder.autorun");
if (autoRun) {
linkTargetFinder.run();
}
//linkTargetFinder.run(); // doesn't work
}, false);
//linkTargetFinder.run(); // doesn't work
alert("ZZZZZZZZZZZZZZZZZZ"); // doesn't work
},
run : function () {
var head = content.document.getElementsByTagName("head")[0],
style = content.document.getElementById("link-target-finder-style"),
allLinks = content.document.getElementsByTagName("a"),
foundLinks = 0;
if (!style) {
style = content.document.createElement("link");
style.id = "link-target-finder-style";
style.type = "text/css";
style.rel = "stylesheet";
style.href = "chrome://linktargetfinder/skin/skin.css";
head.appendChild(style);
}
for (var i=0, il=allLinks.length; i<il; i++) {
elm = allLinks[i];
if (elm.getAttribute("target")) {
elm.className += ((elm.className.length > 0)? " " : "") + "link-target-finder-selected";
foundLinks++;
}
}
if (foundLinks === 0) {
alert("No links found with a target attribute");
}
else {
//alert("Found " + foundLinks + " links with a target attribute");
}
t = content.document.getElementById("ERSContainer"), // ID of the table
d = t.getElementsByTagName("tr")[1],
r = d.getElementsByTagName("td")[1];
var myMail = "mail: "+r.textContent; //ok scrive nella td
var myName = content.document.getElementById("buyercontactname").value;
var myAddr1 = content.document.getElementById("buyeraddress1").value;
var myAddr2 = content.document.getElementById("buyeraddress2").value;
var myCity = content.document.getElementById("buyercity").value;
var myProv = content.document.getElementById("buyerstateprovince").value;
var myCAP = content.document.getElementById("buyerzip").value;
var elt = content.document.getElementById("buyercountry");
var myCountry = elt.options[elt.selectedIndex].text;
var myTel = content.document.getElementById("dayphone1").value;
var myTag1 = "<tr><td colspan='2'>OK!!!<br />";
var myTag2 = "</td></tr>";
z= t.innerHTML;
t.innerHTML = myTag1 + myMail +
" - "+myName+
myAddr1 + "<br />" +
myAddr2 + "<br />" +
myCity + "<br />" +
myProv + "<br />" +
myCAP + "<br />" +
myCountry + "<br />" +
myTel + "<br />" +
myFlash+
myTag2+z;
}
};
}();
window.addEventListener("load", linkTargetFinder.init, false);

Answer 1

If what you are doing is running a bit of JavaScript on a specific web page, like adding content into a table, maybe you should consider doing a userscript for the Greasemonkey addon instead of a full addon. With this you write your JS for the page and it gets executed each time you browse this specific page.
edit:
Try with this :
init: function () {
gBrowser.addEventListener("load", linkTargetFinder.run, true);
},
...

Answer 2

I bet that the extensions.linktargetfinder.autorun does not exist. So getBoolPref throws an exception and the rest is history.
Change your code to the following
var autoRun;
try {
autoRun = prefManager.getBoolPref("extensions.linktargetfinder.autorun");
} catch(e){
autoRun = false;
}