Feature Request: More options for using half resolution in fullscreen mode #581

Hi, I am playing Minecraft on a MacBook Pro with the Retina display. Therefore, I sometimes want to use the feature where the game runs at half resolution in full screen mode. The problem is that I don't want to use half resolution every time I am in fullscreen mode.

Because macOS has two different full screen modes (Minecraft fullscreen mode when pressing f11 and macOS native fullscreen mode when pressing fn+f), I would suggest the following feature:

• When Minecraft is using the f11 borderless fullscreen mode, the game runs at half resolution
• When Minecraft is in the macOS native fullscreen mode, the game runs at full resolution

In addition, is there a way that the GUI size then will always stay the same, so GUI elements don't look smaller when using a higher resolution. Thank you in advance.