It'd be great to have videos like YouTube use a smooth animation when going fullscreen. An animation that makes sense would be the same used to make any window fullscreen, where it just zooms in. Safari on MacOS uses a nice animation on YouTube videos to go fullscreen. It'd be great to have something like that, but with just the video itself zooming into fullscreen like an application window would. A janky example of Safari going fullscreen: https://www.youtube.com/watch?v=ibhUk0WogO0
Yeah, our "animation" for entering fullscreen has always looked pretty buggy.
CC'ing 198053, the desync *may* related to whatever is going on with our full-screen transition code. I got quite lost investigating that issue however, so take it with a grain of salt...
I'm almost positive the desync issue occurs without entering fullscreen, so I doubt it.
macOS WebKit does an interesting thing here: it basically splits the video into a new window, positions it where the video was and fullscreens that. We could do a similar thing with a new window, and it would already be quite nice, but we cannot manually position it on Wayland, so it's not really possible to replicate that.