I'm trying to hook up dual monitors (Samsung CF390) to my MacBook Pro, but when I do, I only have the desktop image projecting on both screens. When I go into Settings > Display, the "Arrangement" option isn't available.
I have both monitors' HDMI cables running through 1 USB-C to HDMI adapter. (The adapter has two ports.)
Is the solution to this problem having two adapters? My thinking is even though the adapter has 2 ports, the MacBook hardware or software can't Fully make use of both displays.
What can I change to get three total displays working on macOS High Sierra (10.13.x)?
Best Answer
I have the same issue. As far as I can tell, it's an issue with High Sierra. and DisplayLink that's not fully resolvable other than through downgrade to an earlier version of the OS. Here's the notice from DisplayLink:
Their workaround kind of works, but it messes up the resolution of the primary monitor and causes periodic flickering. Here's a direct link to that workaround: support.displaylink.com/knowledgebase/articles/1854724.
After updating to MacOS Mojave version 10.14 Beta (18A384a) and DisplayLink v4.3 beta, I can confirm that the "Arrangement" tab comes back and that my laptop recognizes both external monitors and the laptop display at the same time. However, both monitors are always black. The cursor still moves across all three screens, but that's about it. In other words, functionally multiple monitor capability is still broken as of the above MacOS version.
If you select mirror mode, then select "Gather Windows," and then change the external monitors' "Optimize for:" option to "Built-in Retina Display," you can get mirror mode to work nearly properly (there's occasional minor flicker), but there's still no solution for other modes (e.g. where each display is independently able to host windows).