Extentsions FAQ

How to write an XPCOM component in C++ that can communicate to a COM component?

Write an XPCOM component in C++ - it will talk to the COM component and will be accessible to JS code via XPConnect.

How to customizes toolbar button to coexist in a toolbar palette and status bar?

Option #3

Install Status Buttons 1.0

<https://addons.mozilla.org/firefox/1272/>

"Lets you put toolbar buttons at either end of the status-bar. Just drag them there from the toolbar customisation window, like you would when adding buttons to the toolbars."

Option #4

Install Toolbar Control

<http://webdesigns.ms11.net/chromeditp.html>

Asking for help with getting an extension to process Windows messages.

use WM_COPYDATA

How to creating an extension that can replace HTML code on a specific page that does not use Greasemonkey?

var newNode = document.createElement(" ... html content here ... ");

var replaceMe = document.getElementById("replaceMe");

replaceMe.parentNode.replaceChild(newNode, replaceMe);

Is it possible to place an image in the window that can be moved to anywhere in the window, and always remain on top of everything else?(similiar to using position:absolute and-index:100000 in HTML)

you can almost do this with a stack:

<window ...>
    <stack flex="1">
       <image top="40" left="80"/>
       <vbox>
          other content here
       </vbox>
    </stack>
</window>

The only restriction is that your image can't overlap the right or bottom of the window. There are workarounds to this restriction by messing around with overflow or negative margins but I forgot offhand how to do that.

How to create a dynamic drop down menu that may have submenus using JavaScript for an extension?

These two links should give you a starting point:

http://www..xulplanet.com/tutorials/...u/advmenu.html

http://www.xulplanet.com/tutorials/x...dommodify.html

Request for a Thunderbird extension that can automatically detect the default domain when composing e-mails via autodetect.

<https://bugzilla.mozilla.org/show_bug.cgi?id=312818>

"Thunderbird requires domain in addresses and doesn't always add default"

There is an extension that allows what you want attached to one of the comments in this bug.

How to get the value of a text box when a button is clicked?

Read http://developer.mozilla.org/en/docs/Extension_FAQ and check if there are any errors in JS console.

Is there anyway, via plugin or extension, for Firefox to mimic the functionality of IE in this respect?

The IETab (Opens IE in a Firefox tab) should be able do this if you set it to always open "file://*" URLs in an IE tab. The appearance with a FireFox tab isn't quite the same as having a completely separate Explorer window. However, it's functional and does allow for the Explorer to be handling the display of the folder contents, and all of the right-click context menu support is present so it should meet my needs.

What is the valid location and things needed to to release a Mozilla extension on Mozallia site?

You must remove updateURL from the install.rdf and use a known to AMO minVersion/maxVersion.

No confirmation that the answer given worked yet.

Is it possible to open the URL in a new tab?

var tab = gBrowser.addTab( url );

// And if you want it to load in the foreground:
gBrowser.selectedTab = tab;

Is it possible to read the html-code of the current URL/site?

Yes, this is possible. Use the DOM API (http://www.w3schools.com/dom/default.asp has a good tutorial).

Not the best answer but a good starting point for the question asker to do some research towards the answer.

Why does his extension not able to read the contents of a folder and then produce a segmentation fault after his extension reads preferences in Thunderbird?

Are there any built in libraries that can be used to encrypt data?

1. You can use nsISecretDecoderRing.encryptString() and nsISecretDecoderRing.decryptString(). However, I'm not sure how/if that works if the user hasn't defined a master password in Options->Security->Use a master password.
2. You can AES-128 or AES-256 symmetric encryption via aes.js (http://tinyurl.com/pp79t).

No confirmation from the question asker on whether this answer was helpful in solving their problem.

Any suggestions to remove tool tip appears on the menu it when it should not?

What you described was a bug (https://bugzilla.mozilla.org/show_bug.cgi?id=147670). It looks like it has been fixed for Firefox version 2.

What do I need to do to avoid deadlocks? Do I need to marshalinvokations to a particular thread? If so, how? Are there any fundamental rules related to threading in XPCOM, and if so, where are these defined?

DOM can only be accessed from the main thread. Also, check out this site to learn how to set up a proxy: http://www.mozilla.org/projects/xpcom/Proxies.html

How to test a tab has been closed or not?

You can capture the even of tab closing. You can get the tab that is being closed. This should be enough for you.

Is it possible to fix the size exactly at 16x16 pixels avoiding any resize?

Simply position the image and it will no longer be stretched to the size of the stack. <image left="0" top="0"> would seem to suffice.

Could there be more than two images to reflect more than two states?
Does the rules in the CSS file have to be in any particular order (if two rules match, which is chosen)?

I have two states switching images in the tool bar and would have no problem implementing a third, so yes it's possible.

//setting the state document.getElementById("toolbar-button").setAttribute("toolbar-button", "on");
//or
document.getElementById("toolbar-button").setAttribute("toolbar-button","off");

//CSS

#myExten-toolbar-button[myExten-toolbar-button="on"] {
   list-style-image: url("chrome://myExten/skin/toolbar-button.png");
   -moz-image-region: rect(0px 24px 24px 0px);
}

 #myExten-toolbar-button[myExten-toolbar-button="off"] {
   list-style-image: url("chrome://myExten/skin/toolbar-button-off.png");
   -moz-image-region: rect(0px 24px 24px 0px);
}

To implement a third I would simply change add an attribute and the corresponding CSS

See http://www.w3.org/TR/REC-CSS2/cascade.html#cascade

How to get a refenece to the sidebar window

Assuming you have chrome privileges, this should work:

var Ci = Components.interfaces;
var topLevelWindow = 
window.QueryInterface(Ci.nsIInterfaceRequestor)
       .getInterface(Ci.nsIWebNavigation)
       .QueryInterface(Ci.nsIDocShellTreeItem)
       .rootTreeItem
       .QueryInterface(Ci.nsIInterfaceRequestor)
       .getInterface(Ci.nsIDOMWindow)
       .QueryInterface(Ci.nsIDOMChromeWindow);
var sidebar = topLevelWindow.document.getElementById("sidebar");
alert(sidebar.contentDocument); 

Is there anyone successfully using Dojo in a Firefox extension and where to fine sample codes?

The problem with most JS frameworks is that they bootstrap by dynamically appending script elements, which doesn't work in XUL, last I checked. Take a look at the bottom of http://svn.dojotoolkit.org/dojo/trunk/dojo.js

see what it's trying to load and write out the script element by hand.

Could someone write an extension that would collapse the current sidebar in Firefox?

These are called "Grippies"

<https://addons.mozilla.org/firefox/2242/>

This extension brings grippies back to Firefox (and Thunderbird!)

Is there any way to write a regular extension that returns a "dummy" object when an Instance of "@mozilla.org/helperapplauncherdialog;1" is created?

You can write a dummy XPCOM component implementing the necessary interfaces and register it with the sane contract id.

http://developer.mozilla.org/en/docs...PCOM_Component

Would anyone be able to suggest the best way to do source level debugging in a Firefox extension?

In the Debug menu, uncheck Exclude Browser Files.

Use the debugger by typing in a command like this: /break chrome://myextension/content/myfile.js 123

Then I suggest using flat chrome. If you turn off the XUL cache you don't even need to restart to see changes, simply open a new window.

How can I backup some of the files before upgrade an extension and put them back afterward? Do I need to write an installation script to achieve this?

You shouldn't store data there, so there's nothing to backup.

Do not store files within the extension directory.

The Profile directory is ment to do so.

Storing files within the extension directory is a no-no because it might break the multi-user support of those Mozilla products, as it is possible to install extensions directly within the application directory.

Inspector, Talkback and the default theme are nowadays installed like this.

Does Firefox clean up the preferences set by extension? If not, how to proceed?

When user chooses to uninstall an extension, a nsIObserverService notification is sent out. The problem is, while your extension is still active, user can cancel uninstallation, and when it is physically uninstalled, your code can't run.

Right. And if you uninstall Firefox, the profile data is left behind.

It would be nice to give the option of clearing extension's data, but it should be implemented at application level, not by each extension individually.

It might be an option to stick with it and perform stuff when it comes to application shutdown.

The Sanitize stuff does this (clean stuff on exit).

http://lxr.mozilla.org/mozilla1.8/so...ents/nsBrowser...

Firefox will clean all those preferences which are still "default", that is not changed by the user or the application/extension.

To provide those default preferences to your extension see: http://kb.mozillazine.org/Dev_:_Usin...lt_preferences

BTW: Resetting prefences to default will clear them in case no default prefence is (still) available.

Those will be completely removed upon next application launch.

Is it possible to create a sidebar on the top of the page?

Not unless you make it a separate window. There's a bug in bugzilla about stacking other widgets on top of browser/iframe, which hopefully will be fixed for Gecko 1.9.

Could someone write an extension that zaps the Google Analytics cookie, the Urchin cookie, switches Gmail and Google Calender to HTTPS?

CustomizeGoogle extension already has support for switching Gmail to HTTPS (and calendar possibly, too).

Does anyone know how write a bounce email extension?

Are you aware of the "mailredirect" extension? It allows bouncing to arbitrary addresses. It seems what you want is a one button access to that extension with a prefilled bounce address, right?

could someone make an extension for Thunderbird that preview upcomeing events and number of new messages?

In our company I write this extension that connects to our GroupWare server (HTTP). What server should souch extension work gainst? Did you mean Exchange?

How to attach information using the StringProperties of an IMAP message with out changing the properties?

String properties are implemented as IMAP user flags. However not all servers support user flags, in which case you get reduced functionality as follows: all flags are stored in your local cache and are lost if your cache gets invalidated, and only "known" properties are copied when messages are copied. The list of "known" properties is: junkscore junkscoreorigin label priority keywords.

Keywords - In the GUI they are called Tags. They replace the old Labels (although the labels are still recognised).

Preserved properties source code - nsImapMailFolder::CopyMessages

why extension preferences do not get changed until after it's upgrade?

why extension preferences do not get changed until after it's upgrade?

Is there a way of changing the Thunderbird displays headers when replying and forwarding?

Why there are some rss feeds that do not appear as livemarks when bookmarked even though the necessary tags for the feed to appear as a livemark are seemingly present and properly formatted in the feeds source?

Asking for help in knowing the data that is typed into text boxes.

Asking about the feasibility of making an extension that has the same functionality as “trace route”.

How can we programmatically extract the subject, sender, date and the body of an e- mail when you are reading one (in Thunderbird presumably)?

Could someone make an addressbook enhancer extension that has the ability to put pictures on a contact and other features the Thunderbird address book lacks.

Is there a way to save a whole news thread in Thunderbird?

Is there some workaround for the timing issue with Windows and Linux?

Has anyone experienced problem with update that it only considers themes and extensions during the update check, ignoring langpacks with Firefox 2.0?

What language does it require to write XPCOM/XPConnect component that able to intercept,process and redirect HTTP request?
When does content become available in the cache?
Can "partial" data be read from the cache while the request is still in progress?
How difficult is to write a Firefox extensions that does intercetp, process and redirect HTTP request?
Can anyone point me to any good tutorials that may help me get started?

where to modify the email addresses being returned by an LDAP address book?

Is there an extension or script get the actual link of a redirected zip file?

Which Mozilla objects to use to download the data the URL points to and how to combine them?

Can anyone recomment the best way to implement unit tests for an extension and are there any unit-tested extensions examples?

How to get return links from Google Search, and what security pitfalls to look out for while writing extension?