Emulator

By default Dolphin will display everything the game scans out to the screen, regardless of aspect ratio. However, many games expect the display to crop that image, and will have erroneous graphics along one of the edges, usually the bottom. The solution Dolphin has for this is Crop, which crops in to exactly 4:3, 5:4, or 16:9, behaving more like how the games expect and hiding erroneous graphics along the edge.

However, Crop is not able to achieve this on my MacBook Pro. I'll be using The Last Story's green line along the bottom of the screen to demonstrate.

MacBook No Crop
MacBook Crop

But on my desktop with its 16:9 display, Crop works exactly as intended.

Desktop No Crop
Desktop Crop

So what seems to be happening here is that Dolphin is relying on the window itself being 16:9. I can show this by going into windowed mode. With Auto-Adjust Window Size, it is perfectly 16:9 and crop is successfully hiding the green line. However if I drag the window down a bit to make it a taller aspect ratio, the green line reappears despite Crop still being enabled.

Desktop 16-9 Window
Desktop Taller Window

This is not ideal. As 16:10 and 3:2 monitors become even more common, it would definitely be nice for Crop to fulfill its purpose regardless of the display's aspect ratio.

Tested On:
5.0-9705
5.0-12307
5.0-15568
5.0-15804 (latest master)

Tested Games:
The Last Story
Super Smash Bros Brawl

Tested on Systems:

14in M1 Max MacBook Pro
MacOS 12.1

Intel Core i9-9900k
GeForce RTX 3090 (slight overclock)
Windows 10 1909