Video should go to fullscreen mode on orientation change into landscape

[aghassemi]

If a visible video with landscape aspect ratio is playing (autoplay or user-initiated) in the middle of the screen in portrait mode and user rotates device into landscape, it is a strong signal user wants immersive fullscreen and therefore video should automatically go into fullscreen mode.

We may want to put this behind a page-level config (ideally opt-out).

UX thoughts? @cramforce @rudygalfi @edlea-g

[aghassemi]

/cc @abeck000

[cramforce]

Assuming the video is in portrait. We should do this only if major platforms such as FB and Snapchat do it.

[aghassemi]

Added the aspect ration requirement to the description.

FB (Native): Doesn't do this for autoplay videos, user-played videos always go to fullscreen mode anyway, so this is not applicable for non-autoplay videos. Same with twitter.

FB(Web): Unlike native, videos do play inline but orientation change does nothing.

Snapchat(Native): All videos are immersive fullscreen to start with, so not applicable.

YouTube(Native): Does this in native app

YouTube(Web): Does NOT do it on mobile web (despite UI mimicking native)

Washington Post(Native): Landscape orientation change not event allowed.

so lots of different UX out there.

What we do here could be just an element-level attribute as well so authors can decide based on their content if it make sense to go to fullscreen on orientation change. Or we could just do this for fixed hero videos