Dual screen with Awesome WM

xrandr --output HDMI-1 --off
xrandr --newmode "1680x1050_gtf" 147.02 1680 1784 1968 2256 1050 1051 1054 1087 -HSync +Vsync
xrandr --addmode VGA "1680x1050_gtf"
xrandr --output VGA --mode "1680x1050_gtf" --left-of LVDS

Notes:
1. My first attempt turned out the error "xrandr: cannot find crtc for output VGA", the reason was I did not turn HDMI-1 off. I dunno how HDMI-1 exists on my laptop, but for sure i have to kick it off.
2. Awesome WM is awesome, and it default support dual screen.
3. My LCD is 22' and 1680x1050