As far as I know there is no way to easily disable/enable an iMac's internal display at will while simultaneously powering up an external display. Can anyone suggest a solution to achieve this functionality?
Here's the use case scenario presented to me today:
This user basically wants a 21" or 27" laptop that will power two external 27" displays for 3 out of every 4 weeks. For the remaining week it needs to be on the road with them. As no such laptop exists, the scenario is that they want to use an iMac as a tower under a desk for 3 weeks each month. The iMac would provide all the CPU/GPU processing power to run applications and power the two 27" displays. Then, when they need to go on the road, they would just grab the iMac and cart it around in a car. Their desk already has two 27" displays (connected to monitor arms), and therefore it is not practical to just move one of the displays for 3 weeks of the month, nor is there the room to also place an iMac on the desk.
I did ask Why not just get a 15" MBP, but was told they need at least a 21" screen (preferably more) to display the data they work with.
The only practical solutions I could come up with were:
Use two Macs - an iMac to take on the road, and another suitable Mac (perhaps a current model Mac Pro or 15" MBP) to keep on the desk. However, they were not keen on this solution as the data is highly sensitive and it increases the risk of a breach. Apparently the data is so sensitive that the computer will never be connected to the internet and it will be secured in a custom-built cage below the desk. I did ask how they intend to manage the risk on a device that is on the road for one week each month, but was told that was out of scope!
Turn the built-in display brightness down to zero - The user is concerned about the long-term impact this will have on the display etc as the display is not actually disabled or put to sleep while it's being used in this fashion for 3 weeks each month.
My hope is that I'm just missing something really simple (e.g. a terminal command that works on a desktop Mac to put the built-in display to sleep), or a piece of software that does the same thing. Any suggestions/hacks/workarounds are most welcome!