What is the mechanism of "universal control" that enables direct cooperation just by arranging Mac and iPad side by side?

At Apple's developer event "WWDC 2021" held on June 8, 2021 Japan time, "Universal Control" that can seamlessly link Mac and iPad was announced as a new function of macOS Monterey and iPad OS 15. I did. Apple has answered an interview with The Verge, an IT news site, about how this function works.

At WWDC 2021's keynote, Apple's Senior Vice President of Software Engineering, Craig Federighi, is demonstrating Universal Control, which you can watch from around 1 hour 22 minutes 40 seconds in the following movie.

Universal Control is characterized by physically bringing the Mac and iPad closer together. Please note that this Mac and iPad must be linked to the same Apple account.

And when you drag the mouse pointer to the edge of the Mac screen ...

Universal control works, and a bar with a small protrusion sticking out appears at the edge of the iPad screen. This bar makes it easy to see that the mouse cursor has moved to the iPad. You can move the cursor to activate Universal Control only from the Mac side. It is impossible to start Universal Control by moving the cursor from the iPad side at the time of writing the article.

If you keep dragging the mouse, the mouse cursor will be displayed on the iPad.

In fact, a small arrow is drawn on the bar where the mouse cursor sticks out. Move the cursor up and down with the protrusion protruding from the bar to adjust the "up and down position shift" between the Mac screen and the iPad screen so that the user can use the mouse comfortably even across the two screens. It is devised to.

Federighi also demonstrated the iMac next to the MacBook Pro and iPad Pro, sharing a single mouse cursor on three machines.

He operated the iMac's Magic Mouse to move the cursor from the iMac to the MacBook Pro and iPad Pro.

With Universal Control, Bluetooth recognizes each other as devices associated with the same Apple account approach. Then, when the connection between the devices is established by Wi-Fi Direct, Universal Control is activated. Up to 3 devices can be interconnected with Universal Control.

Devices running Universal Control are interconnected via Wi-Fi Direct, so as Federighi demonstrated in the demo, "Move illustrations drawn on the iPad to the MacBook Pro." , You can send and receive files directly between devices. However, if you want to drag a file from your Mac to your iPad, you need to have an app on your iPad that accepts the received file, such as "File".

The Verge claims that Universal Control is a combination of the following four technologies that Apple has developed so far:

1: Device interconnection
Uniersal Control is the same as "AirDrop" that directly exchanges data between Apple devices in that it "establishes a link between devices with Bluetooth and converts it to Wi-Fi Direct to send and receive data". In the first place, the mechanism of linking Apple devices that are physically close to each other via Bluetooth was also used in "linkage" and "Handoff".

2: Multitask function
The multitasking function is a function for operating multiple apps on the iPad at the same time or switching between them with a simple gesture. When connecting an iPad and a Mac, it is required that the iPad also supports drag and drop operations and handles files visually. With the implementation of the multitasking function on the iPad OS, it is now possible to drag and drop files on the iPad as well.

3: Keyboard and mouse support
With the iPad OS 14 released in 2020, support for the mouse and trackpad, which was previously part of the accessibility feature, has become official, and the mouse cursor is now displayed.

4: Sidecar function
Sidecar is a feature that allows you to use your iPad as a sub monitor for your Mac. Sidecar is a separate feature from Universal Control, but The Verge states that "latency reduction on iPads and Macs connected with Universal Control applies the lessons learned from Sidecar."

The beta version of macOS Menteley / iPadOS 15 for developers has been distributed since June 8, 2021 when WWDC 2021 was held, but Universal Control is not yet available in this beta version for developers. Whether universal control is possible in the public beta version scheduled to be released in July 2021 is unknown at the time of writing the article.