Ok, so the problem is, while youtube technically supports ultra wide monitors (like 21:9 ratio) and it works perfectly fine when an uploaded video is actually 21:9, there are a LOT of dumb f*ks (including people working for major movie studios and record companies, apparently) who keep uploading ultra wide videos with black bars hard-coded into them (effectively turning them back into 16:9 aspect ratio). Meaning the actual video frame looks like this:
instead of looking the way it's supposed to look:
So when you go fullscreen on an ultrawide monitor showing a video coded like example 1, the monitor treats it the way an ultrawide monitor treats any other 16:9 video - it adds black bars on the sides. And while it's totally fine for actual 16:9 videos (720p, 1080p etc.) when you do it to a stupidly coded example 1 - you get this:
Anyways, there's a simple fix for that in Chrome:
https://chrome.google.com/webstore/detail/ultrawide-video/lngfncacljheahfpahadgipefkbagpdl
Can anyone please, PLEASE make a similar extension for Maxthon.
I'll be forever grateful. Hell, I'll buy you a coffee (or 10)