Problem with 'properly' using xrandr to set screen resolution

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My monitor is capable of 1600x1200 resolution (Windows and Ubuntu), and following advice here leading to the use of xrandr thus - xrandr --output VGA 1600x1200_60.00 I am able to change the resolution of the visible screen, but this simply makes that screen larger and extend out of the bounds of the monitor screen (likewise a lower resolution makes the visible screen smaller relative to the monitor). Using the --scale flag does not seems to help. Can anyone suggest a possible solution? thanks!