Fix macOS SSH desktop capture with Quartz

[patp]

The problem

SSHDESK on macOS can be fully installed (venv, forced command, sudoers, Screen Recording, Accessibility) and still fail the moment a client connects:

could not create image from display
Traceback (most recent call last):
  ...
  File ".../PIL/ImageGrab.py", line 56, in grab
    raise subprocess.CalledProcessError(retcode, args)
subprocess.CalledProcessError: Command '['screencapture', '-x', '/tmp/...png']' returned non-zero exit status 1

That is not a missing TCC prompt and not a broken OpenSSH config. sshdesk-server never gets a frame.

Root cause: NativeCapture calls Pillow ImageGrab.grab(). On Darwin, current Pillow does not use CoreGraphics. It shells out to /usr/sbin/screencapture. That CLI has failed from SSH sessions for years, even when the Python process already has Screen Recording. On a headless Mac whose only display is a Screen Sharing virtual display, it also fails under launchctl asuser.

The docs said NativeCapture used “Pillow’s CoreGraphics path.” The code did not.

Second bug, same session: if capture is fixed first, PyObjC 12 then crashes input with AttributeError: AXIsProcessTrusted. That symbol is no longer exported on the Quartz module, so MacOSInput dies before any click/key is injected.

The fix

• Capture Darwin frames with Quartz CGDisplayCreateImage (already a sshdesk[macos] dependency) inside the TCC-permitted Python process. Do not call screencapture.
• Resize to CGDisplayPixelsWide × CGDisplayPixelsHigh so mouse coordinates match MacOSInput.
• Leave Windows on Pillow ImageGrab.
• Treat Quartz.AXIsProcessTrusted as optional; fall back to the ApplicationServices C API.
• Tests for bitmap conversion/resize, the Screen Recording error, skipping ImageGrab on Darwin, and the Accessibility fallback.

Verified

Mac Studio, Darwin 25 / macOS 26, Apple M3 Ultra, headless Screen Sharing virtual display, SSHDESK 0.4.5:

• screencapture -x → could not create image from display (exit 1)
• CGDisplayCreateImage → real 2642×1640 frame
• After this change: sshdesk-server --check → 1321x820 NativeCapture capture; input=enabled
• sshdesk-agent screenshot returned the live Finder desktop
• Interactive ssh -t set the title to SSHDESK - Martins-Mac-Studio.local and started drawing

Test plan

python3 -m venv .venv
.venv/bin/python -m pip install -e '.[dev]'
.venv/bin/python -m unittest discover -s tests -v
.venv/bin/ruff check src tests

On a macOS host with Screen Recording + Accessibility granted to the venv Python:

sshdesk-server --check
ssh -t sshdesk@host

[rylena]

lgtm 👍🏾