NPAPI - use javascript objects/functions from within plugin

Question

I've read about how to obtain a handle on DOM elements. This was a very helpful link: http://forums.mozillazine.org/viewtopic.php?f=27&t=1521545

My question now is, can I get a handle on a Javascript var/object I've created, or arbitrary functions?

On page load, i have a script executing something like this...

var controller = new Controller()

or

function callme(param1, param2) { ... }

now, from within my plugin, I want to be able to call methods from my controller object. OR, execute that function callme. Is this possible and how would I go about doing this?

Thanks,

Chris

Community · Accepted Answer · 2020-06-20 09:12:55Z

7

From your link you know how to get the NPObject for the DOM window; from there all you need to know is that all global javascript variables are actually properties of the window.

var controller = new Controller();

If you've done this in the global scope, then window.controller is your variable, so you just need to do:

/* Get window object */
NPObject* window = NULL;
NPN_GetValue(aInstance, NPNVWindowNPObject, &window);

/* Get document object */
NPVariant controllerVar;
NPIdentifier id = NPN_GetStringIdentifier("controller");
NPN_GetProperty(aInstance, window, id, &controllerVar);
NPObject* document = NPVARIANT_TO_OBJECT(controllerVar);

You can then access properties on your Controller object or call methods. Note that if controller were a function you could call it with NPN_InvokeDefault.

BTW, FireBreath automates most of this.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Jan 5, 2011 at 16:40

taxilian

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1 Comment

chrisd Over a year ago

Great, thanks so much. I've read your blog and your 3-part plugin tutorial, but it appears it's my lack of DOM/javascript know-how that's in the way. I tried assuming the above was true, and used chrome's javascript console to list the window object's properties, but a different error was in the way that prevented my object from being a child of window. I appreciate the speedy response.

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