Switching off Macbook Screen but external monitor is also switching off

[Pfanny]

Iam running a MacBook Pro 2017 15inch and using an LG32UD99-W Monitor. Try to switch off macbook screen it going off but one second later also my external screen. monitor connected via USB-C. Hope u can help me.

[Pfanny]

i am running MacOS High Sierra

[PeterBennink]

Same problem, MBP13 (2017), had to do a hard reboot to fix.

[Pfanny]

U can fix it by just closing the laptop. And open again. Both monitors will work again. But switching off one monitor is not possible

[PeterBennink]

Hm that's a shame, that was the whole reason I wanted to use this..

[Pfanny]

Me too

[djalmaaraujo]

same with me. High sierra.

[Gen0]

I believe this is the MacBook, rather than the app. MacBook's power management is so good it switches off the graphics card frame buffer (or forces it to low power mode, which would be too little clockspeed to run external retina displays at all) when the display goes off too. The switch on the lid is hardwired to power it back up.

I doubt it's manageable in software, but if it is dev, you could fix this by switching the primary display to the external, then forcing 3D mode on the GPU with some transparent box render calls (not null so the GPU actually has to do something). GPU performance sucks on secondary displays even with Mac Pros so if the switch not possible it's a lost case and is by design (perhaps to stop MacBook Logic boards being bought from parts and resold in third party desktops).

[reestr]

I have this issue also with High Sierra, using eGPU and external display. Closing and reopening the lid of the macbook does nothing.

[reestr]

Is this connected to the general High Sierra bug which has been filed?