Can a JavaScript function detect which Flash DOM object called it?

Question

Here's the challenge: I have a Flash movie which will be embedded in a page using an unknown DOM ID that I want to be able to identify/store for callback in a JS function.

My ideal user flow would be:

User clicks button in Flash.
Flash pauses any animations / video / sounds / etc.
Flash calls an injected JS function to display a page-covering overlay experience.
When user closes overlay experience, a callback method on the Flash object is called.
Flash resumes playback.

The problem is, when AS3 uses the ExternalInterface.call("functionName", args...) method, there doesn't seem to be a DOM event triggered, and thus it is impossible to tell which object called a JS function, so having a "registerMe()" function doesn't seem to work. Basically, the injected JS function has no way to determine which DOM object to call, because the ID of the Flash object is unknown.

[UPDATE] It turns out, a SWF can determine its own url using loaderInfo.url. I'm passing that information to the script that launches the overlay experience so it can be stored for a future comparison against all application/x-shockwave-flash DOM objects. When a match is found, that is the calling SWF. Does anyone see a flaw in this logic? (I'm not nearly as proficient with JS as I am with AS)

I sometimes have nightmares about trying to get Flash and JS to work together. — sdleihssirhc, May 20 '11 at 23:49
There's always the brute-force technique of finding all SWFs on the page and trying the callback function on each of them, but that strikes me as risky and irresponsible, so it's not really on the table. — Joshua Sullivan, May 21 '11 at 00:23
Yes. We are creating the swf, but won't be controlling its distribution (it will be served on several ad networks). — Joshua Sullivan, May 21 '11 at 03:43
after your update: an obvious problem would be two or more of the same swfs (with the same url) on the same page. Only when you can be sure that will never happen, I think you're safe. — frankhermes, May 22 '11 at 19:10
True enough. I think that can be filed under "acceptable risk" at this point. :) — Joshua Sullivan, May 23 '11 at 04:20

score 5 · Accepted Answer · edited May 23 '17 at 11:52

The JavaScript function you are calling is being called manually, not as an event. It's just like if you used the call or apply methods in JS.

What you can do is pass the DOM name/ID of the active flash video as a parameter to the function you're calling, so that it knows which DOM element to refer back to:

ExternalInterface.call( 'functionName', arg1, arg2, ..., ExternalInterface.objectID );

One "gotcha" with this method is that you need to make sure the object and/or embed elements have both their [id] and [name] attributes set, because ExternalInterface.objectID will be registered inconsistently across browsers.

If I remember right, IE reads the [name] and ff/chrome/opera/safari read the [id], although I believe a couple browsers would fallback successfully to the [name]. I will need to do a test to confirm this.

In any event, give an identical name and id and it should work fine (you'll be able to select the element in the DOM just based on the ID).

score 2 · Answer 2 · answered May 21 '11 at 02:40

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Since I'm assuming that you have full control over the entire embedding process here, sounds like you could tell the SWF its DOM ID as a flashvar as it's being embedded (whether that's via Javascript like SWFObject or as the server generates the HTML). Then, when it calls the Javascript function to trigger the interface, it can send its DOM ID as an argument.

Not exactly ideal, but definitely feasible and easy on the browser.

answered May 21 '11 at 02:40

Matchu

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Unfortunately, we are not controlling distribution of the SWF... it will be on several different ad networks and there are no guarantees that any parameters we set when we upload the swf will be valid once it is out in the wild. – Joshua Sullivan May 21 '11 at 03:45

score 0 · Answer 3 · answered May 21 '11 at 02:41

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I don't think you can. The only "clean" way I can think of is to inject the ID of the Flash object through Flashvars. The ugly way would be to find all Flash objects and use loaderInfo.url to compare and identify the correct Flash Object.

answered May 21 '11 at 02:41

Cay

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Unfortunately, the scenario for the Flash piece is that it is being served through various ad networks and, thus, won't have a consistent ID. – Joshua Sullivan May 21 '11 at 03:42

Can a JavaScript function detect which Flash DOM object called it?

3 Answers3