the method getDisplayMedia only can be called from a user gesture handler

• Component: WebRTC
• Status: NEW ---

[walter]

When we share screen in Safari browser, we found there is a restriction - the method getDisplayMedia must be called from a user gesture handler

In our current meeting behaviour, we cannot call "getDisplayMedia" method from a user gesture handler directly. The reason is  we need to get the presenter privilege first.
As a result, the calling of "getDisplayMedia" is from a callback handler.  We got the following error from the callback handler:

```
getDisplayMedia error: InvalidAccessError InvalidAccessError: getDisplayMedia must be called from a user gesture handler.
```

At least, the calling should not fail. I think a prompt for surface picker or asking permission is acceptable.


Could Safari loosen the restriction just like Chrome browser?

I wrote a example: https://www.fanyamin.com/webrtc/examples/desktop_sharing.html

You can try it by Safari and Chrome, it is ok by Chrome but failed to start sharing by Safari.

[Radar WebKit Bug Importer]

<rdar://problem/80360292>