Alt-Shift-Left and -Right (M-S-<left>/<right>) do not work in emacs on Raspberry Pi (org-shiftmetaleft / org-shiftmetaright)

Question

I am on a Raspberry Pi with Raspbian and any shortcut with Alt-Shift-arrow has no effect in emacs org-mode. I discovered it while trying to use org-shiftmetaleft and org-shiftmetaright.

This is my lsb_release -a

No LSB modules are available.
Distributor ID: Raspbian
Description:    Raspbian GNU/Linux 10 (buster)
Release:    10
Codename:   buster

and M-x emacs-version is

GNU Emacs 26.1 (build 2, arm-unknown-linux-gnueabihf, GTK+ Version 3.24.5) of 2019-09-23, modified by Debian

I tried to use xevto figure out, what happens when I press the keys but I don't understand what the output means:

FocusOut event, serial 48, synthetic NO, window 0x2c00001,mode NotifyGrab, detail NotifyAncestor FocusIn event, serial 48, synthetic NO, window 0x2c00001,mode NotifyUngrab, detail NotifyAncestor
KeymapNotify event, serial 48, synthetic NO, window 0x0,keys:  
2   0   0   0   0   0   4   0   1   0   0   0   0   0   0   0
0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

I appreciate any ideas how to tackle this.

Answer 1

Apparently it's not an emacs problem. It seems the openbox window manager is intercepting the shortcut.

To disable this behavior I had to copy the system-shortcut-file, rename it and comment the S-A-arrow-shortcuts out.

 mkdir ~/.config/openbox
 cp /etc/xdg/openbox/LXDE/rc.xml ~/.config/openpox/lxde-pi-rc.xml

Then nano ~/.config/openpox/lxde-pi-rc.xml and comment the following lines out with <!-- ... --> or delete them.

<!--  
  <keybind key="S-A-Left">
    <action name="SendToDesktop"><to>left</to><wrap>no</wrap></action>
  </keybind>
  <keybind key="S-A-Right">
    <action name="SendToDesktop"><to>right</to><wrap>no</wrap></action>
  </keybind>
  <keybind key="S-A-Up">
    <action name="SendToDesktop"><to>up</to><wrap>no</wrap></action>
  </keybind>
  <keybind key="S-A-Down">
    <action name="SendToDesktop"><to>down</to><wrap>no</wrap></action>
  </keybind>
-->

After a system restart, M-S-right and M-S-left worked as expected in emacs org-mode. :-)