Adding add-on bar to a custom XULRunner application

On MDN, the phrase "Add-on Manager-enabled XUL application" is introduced.

By dragging a XPI file containing an add-on and dropping it onto a FireFox window, the addon's widgets will be installed in FireFox's add-on bar.

I can also use Firefox to run a XUL application by specifying the commandline option "-app application.ini".

Since MDN makes me think that the two are not mutually exclusive, I'm looking for a simple 4 step process where steps 1 and 2 are create a XUL application and XPI independently, step 3 describes how to change either the XUL application or the XPI in preparation for step 4, and step 4 is final integration.

I'll start you off with steps 1 and 2, and then suggest some things that need to be done in steps 3 or 4.

Step 1: Build the XPI by following the tutorial at https://addons.mozilla.org/en-US/developers/docs/sdk/1.3/dev-guide/addon-development/implementing-simple-addon.html

Step 2: Build the XUL application by following the tutorial at https://developer.mozilla.org/en/Getting_started_with_XULRunner

Now for Steps 3 and 4. They should include modifying the application.ini built in step 2 by adding the code:

[XRE]
EnableExtensionManager=1

They should also include adding lines to prefs.js to support the extension manager. And they may require adding addon bar window element to XUL by adding code similar to:

<toolbarpalette id="BrowserToolbarPalette">
<toolbarbutton 
    id="xfox-statusbarpanel" class="toolbarbutton-1 chromeclass-toolbar-additional"
    label="&name;"
    tooltiptext="&name;"
    oncommand="toggleSidebar('xfox-sidebar');"
    context="xfox-contextmenu">
</toolbarbutton>
</toolbarpalette>

I've succeeded in making the "Add-on Manager-enabled XUL application" (aka <TestApp>) accept the XPI (aka <wikipanel>) and attempt to install it, but it fails with the error message: "<wikipanel> could not be installed because it is not compatible with <TestApp version 1.0>"

[edit] I editted INSTALL.RDF (for my XPI) and added the following:

<em:targetApplication>
   <Description>
     <em:id>testapp@sample.xul</em:id>
     <em:minVers‌ion>0.0</em:minVersion>
     <em:maxVersion>9.*</em:maxVersion>
   </Description>
 </em:targe‌tApplication>.

The extension now installs, but I am getting the following error in jsconsole:

Error: The widget module currently supports only Firefox. In the future it will support other applications. Please see https://bugzilla.mozilla.org/show_bug.cgi?id=560716 for more information.

Solution

I've found the answer but it is a bit of a hack and requires removing the following lines of code from the addon-kit javascript source:

if (!require("api-utils/xul-app").is("Firefox")) {
    throw new Error([
      "The widget module currently supports only Firefox.  In the future ",
      "it will support other applications. Please see ",
      "https://bugzilla.mozilla.org/show_bug.cgi?id=560716 for more information."
    ].join(""));
}

Since the above code is specifically designed to prevent using the addon kit in anything other than bonafide Firefox, this avenue is not worth pursuing further. However, if there is a way to build a xul-app in such a way that it conforms to Firefox, then I will revisit the issue.

Firefox is chrome://browser/content/browser.xul after all.