Ubuntu 18.04: Citrix Receiver 13.10 always in Fullscreen mode

Question

UPDATE 5-aug 2018:
On my Desktop workstation I have created 2 VM's (using Virtual Machine Manager).
1) Ubuntu 16.04: clean installation + clean installation of Citrix Reveicer 13.10. I didn't have any problems with the installation of Ctrix Receiver.
The display resolution on the VM is set to 1400 * 1050.
On the VM I have set the preferred window size, of the Citrix session, to 1340 * 970.

When I connect to a Citrix server from FireFox, the Citrix session will fit nicely in a window on the VM without any problems

2) Ubuntu 18.04.1: clean installation + clean installation of Citrix Reveicer 13.10. I didn't have any problems with the installation of Ctrix Receiver.
The display resolution on the VM is set to 1400 * 1050.
On the VM I have set the preferred window size, of the Citrix session, to 1340 * 970.

When I connect to a Citrix server from FireFox, strangely enough the Citrix session stretches to the screen size of the VM. This doesn't happen on the Ubuntu 16.04 VM, only on Ubuntu 18.04.1.

When I set the preferred Citrix window size to 1280 * 840, and connect again to the Citrix server, the Citrix session will fit nicely in a window on the VM without any problems
After setting the preferred Citrix window size to 1280 * 860 or 1340 * 840 or 1300 * 840, strangely enough the Citrix session stretches to the screen size of the VM.

Still any help is appreciated, I use Ubuntu and Citrix Receiver very often
Many thanks, Ronald

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I recently did clean/fresh installation Ubuntu 18.04 and Citrix Receiver 13.10. I was able to connect to a Citrix server from FireFox.

But each time the session appeared in Fullscreen mode.
Using the Citrix configmgr tool, resulted in error-message about missing libcurl.so.4
I managed to solve this error-message with this command

sudo apt install libcurl4-openssl-dev

After this the configmgr worked correctly and I was able to change from Fullscreen mode to Window mode, then saved and closed the configmgr.

From FireFox connected again to Citric server, but still in Fullscreen mode.
I have changed also

Home/.ICAclient/All_Regions.ini

and set the option lines

DesiredHRES=1800
DesiredVRES=1124

Same option lines changed in the file

Home/.ICAClient/wfclient.ini

But every time I connect to Citrix Server, the session is still in Fullscreen mode.

On my previous Ubuntu 16.04 and Citrix Reveiver 13.2, I didn't have this problem.

I have also downgraded Citrix Receiver to 13.3 on the 18.04 installation, but no change.

My question:
is there anyone how has the same type of problem
And is there any solution or reference, in how to fix the problem?

Any help is appreciated and many thanks, Ronald