I installed xubuntu under virtualbox in my widescreen laptop. But I was stuck with space wasted on both sides when I switched to fullscreen since default resolution is 4:3.
The fix is quite simple though. Just taking advantage of the xrandr command…
xrandr --newmode "1360x768" 84.75 1360 1432 1568 1776 768 771 781 798 -hsync +vsync xrandr --addmode VBOX0 1360x768 xrandr --output VBOX0 --mode 1360x768