The "strange" thing was the behaviour. Also if there should only 1 screen be used (xrandr -s "1920x1080") the screen starts in upper left edge of the secondary monitor (the left one) end it was possible to move the mouse up to the middle of the "primary"
(right) monitor. The primary (right) monitor has a resolution of 1920x1200 normally and the left (secondary) (standard Macbook) display has a resolution of 1680x1050.
If I use xrandr with -s "1920x1080" both screens get black and I can move the mouse from left side of the left monitor to the right side of the right monitor. Leavinbg the fullscren with keyboard shortcurt will lead to the result of having the mouse blocked
1900 pixel from the left side of the left monitor (around 300 pixel right from the right monitors left side). typing then "xrandr -s "3200x1290" gets both screens back in full size without entering fullscreen mode again.
X11.app: main(): argc=2
argv[0] = /Applications/Utilities/XQuartz.app/Contents/MacOS/X11.bin
argv[1] = -psn_0_9345257
Waiting for startup parameters via Mach IPC.
X11.app: Listening on socket for fd handoff: (6) /var/tmp/tmp.0.5coKhL
X11.app: Thread created for handoff. Returning success to tell caller to connect and push the fd.
X11.app: do_start_x11_server(): argc=6
argv[0] = /opt/X11/bin/Xquartz
argv[1] = :0
argv[2] = -nolisten
argv[3] = tcp
argv[4] = -auth
argv[5] = /Users/lefti/.serverauth.69446
X11.app Handing off fd to server thread via DarwinListenOnOpenFD(8)
DarwinListenOnOpenFD: 8
[4173050.225] Xquartz starting:
[4173050.225]
X.Org X Server 1.13.0
[4173050.225] Build Date: 20120927
[4173050.226] Initializing built-in extension Generic Event Extension
[4173050.226] Initializing built-in extension SHAPE
[4173050.226] Initializing built-in extension MIT-SHM
[4173050.226] Initializing built-in extension XInputExtension
[4173050.226] Initializing built-in extension XTEST
[4173050.227] Initializing built-in extension BIG-REQUESTS
[4173050.227] Initializing built-in extension SYNC
[4173050.227] Initializing built-in extension XKEYBOARD
[4173050.227] Initializing built-in extension XC-MISC
[4173050.227] Initializing built-in extension SECURITY
[4173050.227] Initializing built-in extension XINERAMA
[4173050.227] Initializing built-in extension PseudoramiX
[4173050.227] Initializing built-in extension XFIXES
[4173050.227] Initializing built-in extension RENDER
[4173050.227] Initializing built-in extension RANDR
[4173050.227] Initializing built-in extension DAMAGE
[4173050.227] Initializing built-in extension MIT-SCREEN-SAVER
[4173050.227] Initializing built-in extension DOUBLE-BUFFER
[4173050.227] Initializing built-in extension RECORD
[4173050.227] Initializing built-in extension X-Resource
[4173050.227] Initializing built-in extension XVideo
[4173050.227] Initializing built-in extension XVideo-MotionCompensation
[4173050.227] Initializing built-in extension GLX
[4173050.228] x: 1680, y: 0, w: 1920, h: 1178
[4173050.228] x: 0, y: 240, w: 1680, h: 1050
[4173050.242] (II) GLX: Initialized Core OpenGL GL provider for screen 0
[4173050.328] X11.app: DarwinProcessFDAdditionQueue_thread: Sleeping to allow xinitrc to catchup.
[4173050.341] (EE) Error loading keymap /tmp/server-0.xkm
[4173050.341] (EE) XKB: Failed to load keymap. Loading default keymap instead.
[4173052.326] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173053.329] Calling ListenOnOpenFD() for new fd: 8
[4173071.930] x: 0, y: 0, w: 1920, h: 1200
[4173071.951] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173071.952] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173071.952] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173071.952] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173071.952] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173092.046] x: 0, y: 0, w: 1920, h: 1178
[4173092.336] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173092.337] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173298.462] x: 0, y: 0, w: 1920, h: 1200
[4173298.489] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173298.495] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173298.496] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173298.496] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173298.496] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173308.384] x: 0, y: 0, w: 1920, h: 1178
[4173308.710] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173308.724] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173322.185] x: 1680, y: 0, w: 1920, h: 1200
[4173322.185] x: 0, y: 262, w: 1680, h: 1050
[4173322.218] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173322.300] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173358.528] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173358.546] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173358.546] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173395.087] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173442.787] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173442.789] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173487.933] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173516.541] x: 0, y: 0, w: 1920, h: 1080
[4173516.555] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173516.555] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173516.557] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173516.557] noPseudoramiXExtension=0, pseudoramiXNumScreens=1
[4173526.666] x: 1680, y: 0, w: 1920, h: 1200
[4173526.666] x: 0, y: 262, w: 1680, h: 1050
[4173526.672] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173526.686] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173543.084] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173557.446] x: 1680, y: 0, w: 1920, h: 1178
[4173557.446] x: 0, y: 240, w: 1680, h: 1050
[4173557.458] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173557.458] noPseudoramiXExtension=0, pseudoramiXNumScreens=2
[4173614.883] Server terminated successfully (0). Closing log file.
The filtered output from system.log from this morning:
Nov 13 08:37:10 voyager org.macosforge.xquartz.X11.stub[69063]: Xquartz: Starting X server: /Applications/Utilities/XQuartz.app/Contents/MacOS/X11 --listenonly
Nov 13 08:37:12 voyager org.macosforge.xquartz.startx[68970]: /opt/X11/bin/xinit: XFree86_VT property unexpectedly has 0 items instead of 1
Nov 13 08:37:33 voyager X11.bin[69063]: NSAlert is being used from a background thread, which is not safe. This is probably going to crash sometimes. Break on _NSAlertWarnUnsafeBackgroundThreadUsage to debug. This will be logged only once. This may
break in the future.
Nov 13 08:46:16 voyager org.macosforge.xquartz.startx[68970]: /opt/X11/bin/xinit: connection to X server lost
Nov 13 08:46:23 voyager org.macosforge.xquartz.startx[69445]: /opt/X11/bin/xinit: XFree86_VT property unexpectedly has 0 items instead of 1
Nov 13 08:46:40 voyager X11.bin[69390]: NSAlert is being used from a background thread, which is not safe. This is probably going to crash sometimes. Break on _NSAlertWarnUnsafeBackgroundThreadUsage to debug. This will be logged only once. This may
break in the future.
Nov 13 08:55:45 voyager org.macosforge.xquartz.startx[69445]: /opt/X11/bin/xinit: connection to X server lost