In my laptop (kubunutu 15.10) i manage to resize the window and i saw that the window was too high minimum size (~800x800). A minimal size of (500,300) would be great !!
I've the same problem on my 7 years old netbook. The native screen resolution is just too small.
I'm using a workaround to mitigate the problem. There is a nice command line tool which rescales your resolution.
It's called xrandr. For me this line works:
xrandr -output LVDS1 --mode 1024x600 --scale 1x1.2 --panning 1024x720
Depending on your monitor geometry, you have to change the parameters.