Dual monitor : how to make a window span over both monitors?

English Hardware
1

Whenever I maximize the window it just snaps to one of the monitors. The same for full-screen. How I can prevent this behavior? I need at least a maximized window over both monitors (ideally full-screen).

I have configured the monitors using the KDE monitor tool.

KDE 4.5.1

2

try xrandr. here’s the command i use:

xrandr --output VGA-0 --auto --pos 0x0 --output DVI-0 --mode 1680x1050 --primary --left-of VGA-0

3

Won’t that just configure the monitors? I have the monitors configured with correct positioning and resolution.