A3 Monitor for macOS

Use the Lenovo ThinkReality A3 AR glasses on a Mac, as a normal monitor and as a teleprompter.

_{The built-in teleprompter, filmed through the A3's lens.}

Lenovo only ever shipped Windows (and Motorola phone) software for the A3, and the product is end-of-life. Plugged into a Mac, the glasses show nothing. This project gets them working:

• Turns the glasses' display on over USB-HID (the same command Lenovo's Windows software sends).
• Monitor mode: adds a 1920 × 1080 virtual display called Glasses Screen and mirrors it into both eyes, so the A3 behaves like a flat second monitor. Both eyes, left eye only, or right eye only.
• Adjust the picture: move it up or down, make it smaller, or change the perceived distance.
• Prompter: a built-in teleprompter. The control window is on your Mac, the text floats in front of you. Black is transparent on the glasses, so only the text is visible. Includes legibility settings (weight, extra thickness, letter spacing) that help if you don't wear your glasses under the A3.
• Menu-bar app, optional launch at login.

Background

I was given a ThinkReality A3 to test when it launched. It works with my ThinkPad, but for the last two years I've mostly used a Mac, and on a Mac the glasses show nothing, so they ended up on a shelf. One evening I took them down and wondered whether I could solve this together with Claude (Opus 5.5). A few hours later they worked as a monitor and a teleprompter. This repo is the result.

Not affiliated with or endorsed by Lenovo. "Lenovo" and "ThinkReality" are trademarks of Lenovo. Use at your own risk. This project only sends the display commands Lenovo's own software sends, and never touches the firmware-update commands.

Requirements

• A Lenovo ThinkReality A3 (PC Edition tested)
• A Mac whose USB-C port supports DisplayPort Alt Mode (tested on Apple M2 Pro)
• macOS 13 or later
• Xcode or the Command Line Tools (xcode-select --install) to build

Build and install

git clone https://github.com/alisinan/a3-mac.git
cd a3-mac/app
bash build.sh --install

This builds A3 Monitor.app, copies it to /Applications and opens it.

On first launch macOS asks for Screen Recording permission (needed to mirror the virtual display). Allow it, then quit A3 Monitor from its menu and open it again. It may also ask for Input Monitoring (used to send the display-on command to the glasses).

The app is signed ad hoc, so every rebuild counts as a new app for macOS and you'll be asked for Screen Recording permission once more. build.sh clears the stale entry for you.

Use

1. Plug in the glasses. A3 Monitor turns their display on within a few seconds.
2. In System Settings › Displays, place Glasses Screen next to your main display. That's the screen you drag windows to. Move Think A3 (the physical glasses output, which A3 Monitor covers) to a corner out of the way. The mouse is kept out of it.
3. Use the A3 menu-bar item:
   • Both eyes / Left eye only / Right eye only
   • Resolution: 1920×1080 down to 1024×576 (lower = bigger text)
   • Image size, Move image up / down, Image nearer / farther
   • Prompter… opens the teleprompter
   • Open at login

Prompter

Prompter… opens the control window on your Mac. Paste your script, set speed, size and legibility; the text appears on the glasses.

Keys (control window focused)

Key	Action
Space / Page Down	play / pause
↑ ↓	speed
← → / Page Up	jump back / forward 3 lines
+ −	font size
R / Home	back to top

Text in [brackets] is shown dimmed, for cues. Most presentation clickers send Page Up / Page Down.

prompter/a3_prompter.html also works on its own in a browser (open it, click Open display window, move that window onto the glasses and press F).

Command-line tools

tools/ has two small Python scripts (need pip install hidapi):

• a3_display.py on turns the display on without the app; status, display on|off, wake.
• a3_probe.py lists the glasses' HID interfaces. Read-only.

How it works

The A3 is a USB-C device with a DisplayPort Alt Mode video input plus a bunch of USB interfaces (HID, cameras, audio). It won't enable DisplayPort until the host sends a HostInfo command on a vendor HID channel. After that it appears as a 3840 × 1080 side-by-side display: the left half goes to the left eye, the right half to the right eye.

A3 Monitor:

1. sends HostInfo over IOKit HID,
2. creates a 1920 × 1080 virtual display with CGVirtualDisplay (a private CoreGraphics API, also used by DeskPad and BetterDisplay),
3. captures it with ScreenCaptureKit, and
4. draws each frame into both halves of a borderless window covering the glasses' display.

The prompter is a WebKit page shown full-screen on the virtual display, so it goes through the same mirror.

Protocol details: docs/PROTOCOL.md.

Known limitations

• CGVirtualDisplay is undocumented. A future macOS update could break it.
• The glasses' own display still appears in System Settings › Displays. macOS offers no way to hide a connected display without cutting its signal.
• The optics have a fixed focal distance. Software can't correct for short-sightedness. Prescription inserts or contact lenses can.
• Head tracking, cameras and the SLAM sensors are not used.

License

MIT, see LICENSE.