[Solved] Dual-monitors stopped working.

[iainrs]

I have a dual monitor setup with 2 '22 inch monitors which has worked for many(5+) years on Linux Mint.

left Samsung - desktop with vertical secondary panel-2 on right hand side

right Benq - used as main screen with horizontal panel-1 (including menu_) on top
(this is the systems primary monitor - Grub menu displays etc)


I was playing with changing margins on the display (to prevent full-sized windows covering my vertical panel) and also contemplating changing the workspace setup
and went into the 'display' screen to experiment with swapping the monitors around.
(not quite sure exactly what I did but nothing too unusual(?) )

I found that the system insisted on 'having the monitors set to 'Mirror' even though the 'mirror option' was set off.

If I disabled a screen the dual-monitor icon showed two screen (with one disabled). on 'enabling' the screen it returned to 'mirror' mode.

I rebooted but nothing changed.

original post
I then disabled the rh screen (Benq) and rebooted (bad idea !!).

The system comes up using the BenQ for Grub etc. Mint 18.2 loads and then I'm left with the lhs Samsung only.
I lost my top panel with my menu ! (now restored onto my single left hand monitor via panel-2)


Whatever I do the Benq remains 'disabled. (see attached image).

Unless someone can help I'll have to re-load Mint 18.2 to get back my dual monitor set-up

A weird problem !!

ps [ 10 minutes later ]

after disconnecting the Benq and reconnecting I managed to get 'display' to restore it but I am still left with the 'mirror' set-up with the same data on each monitor (except panels) (see attached 2)

System: Host: Dylan-II Kernel: 4.4.0-34-generic x86_64 (64 bit)
Desktop: Xfce 4.12.3 Distro: Linux Mint 18.2 Sonya
Machine: Mobo: ASUSTeK model: P7P55D LE v: Rev 1.xx
Bios: American Megatrends v: 2003 date: 12/16/2010
CPU: Quad core Intel Core i5 750 (-MCP-) cache: 8192 KB
clock speeds: max: 2668 MHz 1: 1733 MHz 2: 1200 MHz 3: 1200 MHz
4: 1333 MHz
Graphics: Card: NVIDIA G94 [GeForce 9600 GT]
Display Server: X.Org 1.18.3 drivers: nouveau (unloaded: fbdev,vesa)
Resolution: 1680x1050@59.95hz
GLX Renderer: Gallium 0.4 on NV94 GLX Version: 3.0 Mesa 11.2.0

[iainrs]

[Following Morning]
I switched on this morning still with 'mirrored' monitors and 'mirror' unchecked on 'Display' screen.

I checked 'Mirror' , and applied' to see what happened - two blurred screens.
Then unchecked and the side-by-side re-appeared.
So problem 'solved' even though I don't understand the behaviour of the 'Display' screen.
Sorry to waste time !