Two monitors in Ubuntu, how to set it up?

Question

Iron

Such a jamb:
A second monitor is connected to the laptop via D-Sub. The displays are configured as one common. Naut 1366*768. monitor - 1280*1024
When the application runs in full screen on the monitor - everything is ok. For example, we open LibrOffice and there is also a calculator on it. Everything is fine, there are no jambs.
But as soon as the application does not work in fullscreen, but on the desktop, lags begin, traces of the window remain when moving, as on Windows before, when the process hung.
At the same time, the window itself works) There are no glitches on the screen of the laptop
How to fix, where to look?

Answer 1

In the "Duplicate desktop" mode, the resolution must be set to the same, as a rule, it is automatically set to the smallest resolution, in your case it should be 1280 * 1024.
If you don't want glitches, do "Extension of the desktop"