I was messing around in the options, seeing that a new fullscreen resolution slider had been added, then I realized the fullscreen button itself didn't work.
What I expected to happen was...:
1. Pressing the fullscreen button in the options/video settings menu would toggle fullscreen on and off.
2. After pressing the fullscreen button, it would say "on".
What actually happened was...:
The fullscreen menu defaulted to off and had glitchy effects, like the screen being fullscreen but the game being surrounded by a black border. The fullscreen button also does not toggle, and stays off.
Steps to Reproduce:
1. Go to the Video Settings tab of options
2. Press the fullscreen button
All posted screenshots were not using Minecraft's screenshot generator, as those don't demonstrate the glitch fully.
Environment
MacBook Air, Intel HD Graphics 6000 1526 MB
Duplicate of MC-121367, please use the search function before reporting.