How to change 3rd monitor programmatically

Question

When I'm using my laptop, I use 3 displays:

1. The laptop display
2. A second monitor (connected through VGA)
3. A TV (connected through HDMI)

My videocard doesn't support 3 monitors, so I'm constantly switching from 2 to 3: when I'm on the computer, I use the 2nd monitor, and when I want to watch some movies, etc. I use the 3rd.

I currently have to go to Screen Resolution, select the monitor that is not in use, and choose Extend desktop to this display.

Is there a way I can automate it?

Is there any command-line tool, or any Windows API that allows doing it?

Edit:
Display Changer seems to do what I need, but the problem is that it only detects the working monitors. The 3rd monitor (which isn't currently in use) isn't detected, so I can't attach it.

Answer 1

A bit of RE on DisplaySwitch.exe shows that it calls

SetDisplayConfig(0, NULL, NULL, NULL, 0x888)

to set it to Extended on my computer.

From there, a little digging around got me to the SetDisplayConfig documentation obviously and also this SO page with some example code that queries your current display state and adds the actual flags to change them if you want to do so.

Answer 2

I answered a similar question with suggestion to try UltraMon or use their SDK, but you can also hit the Win32 API directly with ChangeDisplaySettingsEx. Another user, Sai, gave an reference to an example showing use of the function.