Open Radar

 
Summary:
When a video is played in fullscreen mode from Safari, and then the fullscreen space is removed from Mission Control, this results in some bugs with the video player.

Sometimes the video player in the website it was originally made fullscreen from starts rendering at a different resolution. Taking the video to fullscreen again later on almost always breaks the fullscreen player, with the video rendering in a tiny box towards the middle of the screen instead of taking the entire screen

The issue persists on refreshing the webpage, and can only be fixed by closing the tab. This has been tested with Youtube.com and WWDC videos on developer.apple.com

Steps to Reproduce:
1. Open a webpage with a video in Safari (YouTube.com and WWDC videos tested here)
2. Press F to take it fullscreen
3. Open Mission Control
4. Drag out the space showing the fullscreen mode to a desktop so that it disappears and is added back to the original webpage
5. Return to the webpage

Expected Results:
The player on the webpage should look identical to what it was before taking it fullscreen. Taking it fullscreen again should work as expected

Actual Results:
The player can instead render at a different resolution (observed on YouTube). Taking it fullscreen renders the video in a small box of the screen

Version:
Safari 10.1.2

Notes: