For a multi-head configuration, the first requirement is multiple monitors.
On the VivoBook the main display is a standard display panel on output
eDP1, whose natural size is 1920x1080px and refresh rate 60Hz.
The ScreenPad is on output
HDMI1, of natural size 1080x2160px and
refresh rate 50Hz. There is also a mode of 504x1000px but the screen was
black when I tried it. These parameters can be discovered in /var/log/Xorg.log
when the defaultly configured X-Server starts up.
The X-Server can (and normally does) handle non-configured monitors as well as hotplugged monitors. I created a file /etc/X11/xorg.conf.d/91-2head.J.conf to configure these monitors, but I need to see if it is actually needed for the XFCE configuration explained here. Here is the configuration fragment:
Section "Monitor" Identifier "eDP1" Option "Primary" "true" Option "PreferredMode" "1920x1080" Option "Position" "0 0" EndSection Section "Monitor" Identifier "HDMI1" Option "PreferredMode" "1080x2160" Option "Position" "1920 0" Option "Rotate" "Right" EndSection Section "Device" Identifier "Intel" Driver "intel" Option "Monitor-eDP1" "eDP1" Option "Monitor-HDMI1" "HDMI1" EndSection Section "Screen" Identifier "Screen0" Device "Intel" Monitor "eDP1" # SubSection "Display" , let it figure out the framebuffer geometry. EndSection Section "Screen" Identifier "Screen1" Device "Intel" Monitor "HDMI1" # SubSection "Display" , let it figure out the framebuffer geometry. EndSection Section "ServerLayout" Identifier "2head" Screen 0 "Screen0" Screen 1 "Screen1" below "Screen0" EndSection
This configuration has both monitors showing part of one big framebuffer. Most documentation, and the XFCE configuration plugin, assume this arrangement. Windows can be moved freely between the monitors, or even split between them. But it is also possible to create two independent screens.
With this configuration fragment, when the Display Manager (lightdm for me) logs in its greeter, the greeter window will appear on the window where the cursor is, which in my case is always the ScreenPad. It's easier to use the greeter when it's on the main screen, so move the cursor there. [Update: with a side by side layout the greeter gets on the main screen.]
Now you need to tell XFCE to take control of the server layout. Start
Display settings plugin.
Laptop, should be the primary display; turn that on.
Toshiba…) needs to be rotated to the
right. Keep the defaults for Resolution, Scale, Refresh, Rotation and Reflection, on both screens.
configure new displays when connected, but made no other changes.
Now the ScreenPad is active but has no content; it's black. Try moving a window off the bottom of the main display: it appears on the ScreenPad.
I would like a non-black background on the ScreenPad. Run the
Desktop settings plugin. Move it onto the display you want to
configure (the ScreenPad). Get out your magnifying glass.
Folder dropdown list, pick the directory containing your
background image(s). The images' thumbnails will appear in the big
Wallpaper area. Click on one; it will be shown in the background.
Set the display style. Turn on
Apply to all workspaces; it looks like
you could potentially have a different background on each workspace.
I kept the defaults on the Menu tab. On the Icons tab, these refer to 128px icons for launching the file browser (Thunar) on your home directory, the global filesytem, or the trash. As an old troglodyte from when Project Athena was new, I never use these, so I turned them off, keeping only the removeable device option.
I did an impromptu power measurement: with the ScreenPad disabled, the laptop draws 8W; enabled it needs 9W, the same power whether the background is black, white, or a photo. So the ScreenPad is a light-valve display (same as the main screen) and it's using 1W to 2W.
Effect of various disruptive events on the screen layout:
Scaledexpands isomorphically to fill the narrower dimension, centered in black borders.
Zoomedexpands isomorphically to fill the wider dimension, with parts chopped off in the narrow direction.
So I think the ScreenPad is now operational. Now I need to figure out how to make it useful beyond just showing a pretty picture.