CGEventPost is not working in (MacOS) launchd daemon

Question

i want to simulate the keyboard with CGEventPost in the user session (MacOS).

CGEventRef keyEvent = CGEventCreateKeyboardEvent( NULL, keyCode, down ) ;
CGEventPost( kCGHIDEventTap, keyEvent ) ;
CFRelease( keyEvent ) ;

when i use this code in a normal app(whether run as root) , it works fine.

but when i run it in launchd-daemon like the project smjobbless , it's not working.

here is my launch.plist:

<dict>
    <key>Label</key>
    <string>com.apple.bsd.SMJobBlessHelper</string>
    <key>RunAtLoad</key>
    <true/>
    <key>MachServices</key>
    <dict>
        <key>com.apple.bsd.SMJobBlessHelper</key>
        <true/>
    </dict>
    <key>KeepAlive</key>
    <dict>
        <key>SuccessfulExit</key>
        <false/>
    </dict>
</dict>

the launchd-daemon project had been installed at /Library/PrivilegedHelperTools success and everything is running OK （seems run as root） except the CGEventPost , it's very strange , any suggestions?

Answer 1

Daemon processes do not have access to the window session. UI events should be pushed back over the XPC channel to a process in the user's session (generally running as the user rather than root). If you want a launchd configuration, consider LaunchAgents rather than LaunchDaemons.

Consider how this would work under fast user switching when there are multiple active window sessions.

Directly to your question, in the above-linked docs, note:

The Core Graphics framework relies on the presence of the window server and thus is available only to applications running in a login session.

Your daemon does not run in a login session.