xrdp session established, all GOOD, but invisible windows in RDP client

[pswiatki]

I have an interesting case on my Arch Linux / Windows 10. Previously (2-3 years ago) everything worked perfectly OK, but I stopped using rdp to Linux for quite a long period. Now that I wanted to use it again I had to go through the pain of setting everything up proper, so that my logs did not show any problems preventing connection. Still, I could not get the remote session to operate properly. No issues in the logs, no timeouts, session shutdowns, misbehaviour of any kind..... except for one: no visibility. I could not believe this could be possible. It turns out the session is established, logon is correct, access is granted, the window manager is launched properly as well as several example apps (xterm, xclock). But just none of them are visible in the rdp client on Windows 10. The only reason I discovered it was that the mouse pointer changed shape when moved in the rdp client. So, remembering from the past that the usual terminal window was in the upper left area of the desktop, I can click blindly on it to bring it into focus and close the entire session by Ctrl-D, or typing exit.
I reason: if it had to do with how xrdp transfers content to the client - then I would not see even the initial xrdp login screen, but I can nicely see it and log in without any problems. It is only later that I can't see anything, but the logs (including journal) tell me all is perfectly OK.
I looked online, but couldn't find anything that could help. What can I do to further troubleshoot this?

[pswiatki]

Alright, got this finally. I installed

[pswiatki@RF-old ~]$ pikaur -Ss xorgxrdp-nvidia
Searching... [###]
aur/xorgxrdp-nvidia 0.2.18.r49.g3d30c7a-1 (5, 0.00)
    Xorg drivers for xrdp, with NVIDIA GPU support.
[pswiatki@RF-old ~]$

in hopes I could get HW acceleration, but since the laptop I connect to has nVidia-Optimus, I believe it did not play well with the driver (No device found message in the log). So, I changed the config to use the regular /etc/X11/xrdp/xorg.conf in place of /etc/X11/xrdp/xorg_nvidia. Just realized my mistake: the xorgxrdp modules (libs, drivers) stayed with nvidia support, which did not work as intended. So, after switching to

[pswiatki@RF-old ~]$ pikaur -Ss xorgxrdp-glamor
Searching... [###]
aur/xorgxrdp-glamor 0.10.3-1 [installed] (7, 0.66)
    Xorg drivers for xrdp, with glamor enabled. Only works on Intel and AMD GPUs.
[pswiatki@RF-old ~]$

things returned back to normal. The X server created by xrdp now uses the Intel's built-in GPU:

[652074.537] rdpPreInit: glamor module load ok
[652074.582] (II) XRDPDEV(0): glamor X acceleration enabled on Mesa Intel(R) HD Graphics 3000 (SNB GT2)
[652074.582] rdpPreInit: glamor init ok
[652074.582] rdpScreenInit: virtualX 800 virtualY 600 rgbBits 8 depth 24
[652074.582] rdpScreenInit: pfbMemory bytes 1920000

... and I can see everything and run apps as intended.

[pswiatki]

My question is this: how is it possible that xrdp renders the image somewhere, but it cannot be seen (and no clear error is indicated)? Just trying to understand it this case thoroughly.