Mismatch in screen dimensions for Lubuntu when connecting via HDMI to projector

Question

I am using an Acer Aspire R 11 Convertible, 11.6" HD Touch, Intel Celeron N3050, 2GB Memory, 32GB Storage, running Lubuntu, which is Ubuntu 16.04 (Xenial). I use the awesome window manager primarily, but LXDE is still installed and I can easily switch between the two when necessary.

I use the laptop for giving lectures at my university (I use the touch screen to write notes), and I use the projectors provided by the school. I connect the computer to the screens via an HDMI cable. On the first two days the screen projected and the screen I saw were exactly the same, which is what I want. But for some reason that's no longer the case. I can change the resolution of the HDMI screen and for some settings the screen projected is the upper corner of the screen I see on my laptop, and other times the situation is reversed. This is a problem; if my laptop shows only the upper corner then I can't see the taskbar, and if the students see only the upper corner I have to make the window of the program I am using small, so writing notes is hard. I have not found a setting where the screen projected and the screen on the laptop are exactly the same. This is using whatever the built-in program for managing the monitor settings is (on LXDE).

What can I do to remedy this?

Answer 1

Here are my own experience, since I run Lubuntu and have three monitors.

sudo apt install arandr

After that, look in Lubuntu Menu:

1. At Preferences menu, go to Monitor Settings

2. Enable all monitors Lubuntu has detected (mark these checkbox at left)

Open arandr (it's locates at Preferences sub-menu) and build your own scheme. Save your scheme at place you can find (i suggest ~/mx) and close arandr

When monitor scheme at sometime goes weird, just

1. press CtrlAltT

2. type bash ~/mx.sh

If you prefer, you can set this script to run at session login. Or customize a shortcut to make your work easier