Question

My Firefox extension generates events, e.g. click. In response, the web application tries to open a new window. However it’s getting blocked by Firefox as Popup blocker kicks in. However, if I manually click a button and in response to that when the web app tries to open window, it goes through.

My question is why aren’t events generated by my extension treated as ‘trusted’, and treated the same way at user click? Is there some backdoor to achieve that behavior?

Answer 1

Edit: This answer is badly outdated. It refers to classic extensions that are no longer supported as of Firefox 57. Extensions based on the Web Extensions API have no way of generating trusted events.

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Yes, events generated by extensions are always trusted. That means that event.isTrusted will be true and the events will be able to trigger actions that require trusted events (e.g. Ctrl-Tab keypress event to switch browser tabs). However, they stay synthesized events meaning that there is no native (OS-level) event associated with them. And since the pop-up blocker works with native events it will not see the events generated by your extension.

You can use nsIDOMWindowUtils.sendMouseEventToWindow() instead of document.createEvent(). This method is meant for testing and will generate a native event as well. This should be good enough for the pop-up blocker.

var utils = window.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
                  .getInterface(Components.interfaces.nsIDOMWindowUtils);
utils.sendMouseEventToWindow("click", 10, 20, 0, 1, 0);