[whatwg] Feedback on the Mozilla FullScreen API proposal

Mike Wilcox mike at mikewilcox.net
Fri Aug 6 06:39:30 PDT 2010

Kudos to Mozilla (and Robert?). This is awesome. It does appear that you plan to allow fullscreen without the use of a user-trigggered event such as a button-click like Flash does. Not only would I like to launch my app in fullscreen to play a game, I may want to allow my advertisers to launch fullscreen videos for a premium fee. I think this is a good thing. It's important to keep restriction versatile so that both the user and developer are in control. As opposed to too much security completely killing the feature and force developers to continue to rely upon Flash.

First a small thing. The format of the CSS style:
I don't see why "fullscreen" should be hyphenated. Even the title of the page uses it as one word.

I don't understand the use of requestFullScreenWithKeys(). Why would I ever use a more restrictive method? How about just fullscreen() - and it toggles? And security is handled through element attributes?

I assume the entire reason for security is for third party apps (video) and advertisements (have I missed an actor?). It seems to me that I would want to prevent a third party from calling fullscreen. The spec makes it look like its up to the developer on whether to use the security or not. Did I read it wrong? The spec focuses a lot on iframes. It's fine to restrict functionality in an iframe, but a majority of third party apps and advertisements don't happen in an iframe, they are written to the page, often with document.write – and they often write their own iframe. The iframe restriction will work for scenarios such as an HTML5 Video embed, but not for ads.

Here are some suggested constants. The actual spelling or exact usage is not relevant, I'm addressing functionality (I agree with Anne on constants in JS). I'm looking at these suggestions mostly from the POV of a web developer, not a user nor user agent.

The first, simple use case I'm looking to solve is to block your ads from using fullscreen. I don't see a way to do that in the spec. I recommend the above options are properties of the document.body:
	<body allowFullscreen="blocked">

Note however, that I recommend that allowFullscreen="block" be the default, so ads can't start launching fullscreen in existing, unmaintained pages.

The second simple scenario is to use fullscreen but you don't need to worry about ads:
	<body allowFullscreen="allow">

The third scenario gets more tricky, and is why I am suggesting using the properties as node attributes. Think about the NY Times wanting to allow fullscreen to read the article but block ads (or certain ads) from fullscreen:
	<body allowFullscreen="blocked">
		<article allowFullscreen="allow">
		<aside allowFullscreen="blocked">

The suggestion is that fullscreen permissions are on the element level and are inherited. Further, they should be only writable in HTML markup, and read-only in JavaScript so permissions cannot be dynamically changed.

A potential problem is a rouge third party script scanning the page to find the article element allows fullscreen; and it writes content to it and launches it. The solution could be that allowFullscreen is NOT readable by JavaScript – it can only discover permissions by the attempt to go fullscreen.  

A modification to this would be a write-once apiKey that is private:

	document.setFullscreenApiKey("mysecret"); // set only once, subsequent calls ignored, cannot be read
	onClick = function(){
<body allowFullscreen="password">

I think this idea is clever, but I may be over thinking it. allowFullscreen="userIntiated,mouseOnly" is probably all that is needed in this case (and perhaps most cases).

Of course, nothing is 100% secure, and since this is the list that said DRM is impossible, I'm really advocating that we don't try for 100% safety and cripple the feature. 

Mike Wilcox
mike at mikewilcox.net

On Aug 5, 2010, at 5:17 PM, Simon Fraser wrote:

> This is feedback on the Mozilla FullScreen API proposal here:
> <https://wiki.mozilla.org/index.php?title=Gecko:FullScreenAPI>

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