[webvr] Why does entering VR need to be on user interaction?

Kip Gilbert kgilbert at mozilla.com
Wed Sep 21 02:04:52 UTC 2016

Hi Michael,

Perhaps I can help answer some of these...

> On Sep 20, 2016, at 6:20 PM, Michael Chang <flux.blackcat at gmail.com> wrote:
> In the latest chromium build:
> VrDisplay.RequestPresent must happen in a user gesture. (Click, touch, etc.)
> If you want the page to automatically enter VR (say, from a settimeout), you get this error now
>> Uncaught (in promise) DOMException: API can only be initiated by a user gesture.
> I want to understand the thought process behind this decision.
> To my understanding, Chrome requires user interaction to go Full Screen because some old person might get tricked into thinking the browser is now their OS and they're entering their credit card to phishing, which is a security concern.
> Am I wrong that is the only reason? How is that relevant to VR though? Why is a user gesture required to enter VR?
The rationale is that we wish to protect users from scripts in pages such as ads that wish to take over your VR session.

> I want to argue that adding an extra button press to enter VR is bad friction on both user and developer end. I know it sounds minor, and probably a crap ton of hand holding do-not-put-your-hands-and-legs-outside-of-the-vehicle decision making that goes into making Chrome, but it worries me a lot.
> On the User End
> Recall the wonderful discussion we had in the other thread about the future of VR, and building the metaverse and linking to other pages which are also VR. How incredibly bad would that user experience be if every time you link somewhere in VR, you have to take off your headset, go back to your desk and find the mouse, then click on enter VR, in which every website might have a different way of doing so?

For this use case, the onvrdisplayactivate event will fire on the page after it is loaded with a reason value indicating that there is a VR to VR link traversal.  Within this event, the page can enter VR without a user interaction as the link traversal itself is sufficient.
> On the Developer End
> From a developer's perspective, it's bad enough we have to constantly take our headsets off and on just to find out what's going on inside there. Take for example, Unreal Engine's VR developer mode being really awesome because it knows when you've taken off or on the HMD. This is developer friendly, there's very little friction between the editor and entering VR.
> I don't know how you guys develop VR and I've tried several methods to make it friction free.
> My VR Development Style
> My first method is developing in HMD all the time, using a combination of Virtual Desktop launching chromium and having its home page be localhost:8000 and a voice command to reload the page. This is neat because I can still type in Sublime Text in VR, and still see WebVR live-reloading and everything still works.
> My current method is having a setTimeout automatically enter me in VR (1 second after page reload) and I just have the HMD on my head and pull it down when I need to see something, and just hit reload. This method no longer works.
Perhaps we could adjust the spec to include refreshing a WebVR site as one of the "reason" values that is passed to onvrdisplayactivate...  would that solve the issue?
> So what do I do now? I guess I can bind a Vive button to enter VR? How janky is this? Why do we have to do these hacks to enter VR, when WebVR is about VR content and having to worry about how to enter VR is just friction that shouldn't be there?
Would it help to have a "Dev mode" or such switch for exceptional cases?
> Please, if anyone has insight, power to roll back this decision, or just want to discuss this issue, hit reply below.
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Thanks for the feedback!  For the Firefox implementation, would you have any particular wants to include in upcoming WebVR devtools?

  Kearwood "Kip" Gilbert

  Mozilla VR Team
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