Setting a custom screen resolution requires configuration changes in both the client Cassini Virtual Workstation (eCS on Virtualbox) and the VirtualBox configuration from the host OS. If multiple VMs exist, the following steps need to be performed for each one.

Configure Virtualbox Machine Settings:
1. Stop all VirtualBox instances and close the VirtualBox Manager window. (Otherwise the settings may be overwritten when the UI is closed.)
2. Run "VBoxManage" command to set screen resolution.
Windows: Run the following command from the VirtualBox program folder. Tip! Use File Explorer to navigate to "C:\Program Files\Oracle\VirtualBox\" then replace the address with "cmd" and hit [enter] key.

VBoxManage setextradata "<Machine Name>" CustomVideoMode# "<width>x<height>x32"
"<Machine Name>" = The name of the VM
"#" is the screen resolution number (1 - 9)
"<width>" and "<height>" are the X and Y dimensions of the desired screen resolution

1080 HD (Widescreens)
VBoxManage setextradata "CassiniSimulation-Lab" CustomVideoMode1 "1920x1080x32"
VBoxManage setextradata "CassiniSimulation-Lab" CustomVideoMode2 "1366×768x32"

Half 1920x1080 for split screen
VBoxManage setextradata "CassiniSimulation-Lab" CustomVideoMode2 "960x1045x32"  

Confirm Settings
VBoxManage getextradata "CassiniSimulation-Lab" enumerate


Configure eCS:
1. Launch the VM configured above.
2. After eCS boots, select System Settings (red toolbox) > Screen.
3. Select the resolution from the list and close the window.
4. Restart eCS by choosing the Power Button > Standard Restart > OK.
5. The VM will restart with the desired resolution.


Software Prerequisites:
VirtualBox v4+ with Extension
eCS with VirtualBox OS/2 Guest Additions installed. (See Install/Upgrade VirtualBox OS/2 Guest Additions)
GRADD video driver installed. (Verify with eCS > Local System > Install/Remove > Video Driver Wizard)

More Information: http://os2notes.net/os2virtualbox4.html

Keywords: screen size, screen