External display output

graphics.external-displayHands-on · challengeHigh confidence

How it tests

Watches the external connectors (DisplayPort, HDMI, DVI, VGA) for one to connect and reads its EDID and modes. Then it puts a test card on that output itself, by KMS on a CRTC of its own: a dark card with a white border and a 3-digit code. The code shows on the monitor only, never on the Mac's screen. The tester types it; a miss gets one more try with a new code that differs in at least two digits.

How it decides

Supported: connected with an EDID and modes, the card went up, and the code typed right. Partial: the code typed right on a connector with no EDID; or detected and the tester sees no picture or a wrong one. Failed: nothing connects (“Nothing shows up”, offered after 15 s). Not tested (uncertain): a wrong code twice, or the card couldn't go up and the tester only says they see the mirrored console.

How sure it is

A blind guess passes about 2 times in 900, and the picture on the monitor is drawn for it, not mirrored.

What could mislead it

Could pass when it shouldn'tThe criterion covers every built-in video output; only the port the monitor went into is tested (its connector is named in the evidence).
Could fail when it shouldn'tAn adapter (Mini DisplayPort to HDMI or VGA) gives no EDID, so a good picture comes out partial.
Could end without a verdictTwo typos end it as not tested (uncertain).