[winswitch] xpra client window on 14" laptop doesn't show full screen of 15" laptop running xpra server

[Tim]

The xpra client window   on a 14" laptop shows the screen of the 15" laptop that runs the xpra server only partially (a part near the bottom and a part near the right are cut off). The screenshot below shows the screen of the 14" laptop with the xpra client window inside: https://i.stack.imgur.com/GA9rX.png
Both laptops are running Lubuntu 18.04.

The remote xpra version and screen dimension and resolution are:

    $ xpra --version
    xpra v3.0.8-r25889

    $ xdpyinfo | grep dimensions
      dimensions:    1920x1080 pixels (508x285 millimeters)

The local xpra version (shown different from the remote one, but might be incorrect, see https://unix.stackexchange.com/questions/578622/have-i-upgraded-a-package-and-why-is-there-a-mismatch-of-its-version-shown) and screen dimension and resolution are:

    $ xpra --version
    xpra v3.0.7-r25627
    
    $ xdpyinfo | grep dimensions
      dimensions:    1440x900 pixels (381x238 millimeters)



Here is the command that I ran to connect

    $ xpra shadow ssh:"t at onion":0
    
    (xpra:16983): dbind-WARNING **: 20:13:10.163: Couldn't register with accessibility bus: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
    2020-04-07 20:13:10,318 Xpra GTK3 X11 client version 3.0.7-r25627 64-bit
    2020-04-07 20:13:10,613  running on Linux Ubuntu 18.04 bionic
    2020-04-07 20:13:10,615  window manager is 'Openbox'
    2020-04-07 20:13:10,697 Warning: failed to import opencv:
    2020-04-07 20:13:10,697  No module named 'cv2'
    2020-04-07 20:13:10,698  webcam forwarding is disabled
    
    (Xpra-Audio-query:17000): dbind-WARNING **: 20:13:11.757: Couldn't register with accessibility bus: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
    2020-04-07 20:13:11,895 GStreamer version 1.14.5 for Python 3.6.9 64-bit
    2020-04-07 20:13:12,374 No OpenGL_accelerate module loaded: No module named 'OpenGL_accelerate'
    2020-04-07 20:13:13,002 Error: cannot handle window transparency
    2020-04-07 20:13:13,002  screen is not composited
    2020-04-07 20:13:13,086 Warning: vendor 'Intel Open Source Technology Center' is greylisted,
    2020-04-07 20:13:13,086  you may want to turn off OpenGL if you encounter bugs
    2020-04-07 20:13:13,349 Error: cannot handle window transparency
    2020-04-07 20:13:13,349  screen is not composited
    2020-04-07 20:13:13,360 Warning: window 4294967295 changed its transparency attribute
    2020-04-07 20:13:13,361  from False to True, behaviour is undefined
    2020-04-07 20:13:13,450 OpenGL enabled with Mesa DRI Mobile Intel® GM45 Express Chipset
    2020-04-07 20:13:13,730 Connected (version 2.0, client OpenSSH_7.6p1)
    2020-04-07 20:13:14,386 loaded RSA private key from '/home/t/.ssh/id_rsa'
    2020-04-07 20:13:14,405 Authentication (publickey) successful!
    2020-04-07 20:13:14,736  keyboard settings: rules=evdev, model=pc105, layout=us
    2020-04-07 20:13:14,834  desktop size is 1440x900 with 1 screen:
    2020-04-07 20:13:14,835   :0.0 (381x238 mm - DPI: 96x96) workarea: 1440x876
    2020-04-07 20:13:14,835     LVDS-1 (303x190 mm - DPI: 120x120)
    2020-04-07 20:13:14,909 no ethtool interface speed available for wlx801f02b5c389
    2020-04-07 20:13:20,742 enabled remote logging
    2020-04-07 20:13:20,744 Xpra GTK3 shadow server version 3.0.8-r25889 64-bit
    2020-04-07 20:13:20,746  running on Linux Ubuntu 18.04 bionic
    2020-04-07 20:13:21,120 server does not support xi input devices
    2020-04-07 20:13:21,123  server uses: auto
    
    (Xpra-Audio-play:17029): dbind-WARNING **: 20:13:22.207: Couldn't register with accessibility bus: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
    2020-04-07 20:13:22,299 sound output using pulseaudio device:
    2020-04-07 20:13:22,300 sound output  'Built-in Audio Analog Stereo'
    2020-04-07 20:13:22,898 sound output using 'opus' audio codec