XenApp 6.5 – Seamless applications always on top

I noticed that intermittently seamless XenApp 6.5 published applications would stay on top of other windows even when they were not active.  In my case I been utilizing the Citrix Receiver Enterprise 13.1.0.89 to take advantage of the Pre-Launch feature.

Was able to replicate the issue with all Receiver versions 3.x, even with the new 3.4 client which also works with the Pre-Launch feature of XenApp 6.5

I did not experience the same problem with legacy clients 11.2 and 12.1 (Don’t use these clients with XenApp 6.5)

Environment

• Windows 2008 R2
• XenApp 6.5
• UPM 4.1
• vSphere 4.0 <-  What the heck? I know, I know 
• Citrix Receiver 3.x

Cause:

The issue exact cause is unknown, but seems to be related to changes in the gain focus behavior of the new Citrix Receiver 3.x.  I contacted Citrix support on this one, and after they thought I was crazy, I was able to replicate the problem while on the phone.

It seems that a Seamless Application Window does not become the active window if you make a local window active while the seamless connection initiates.

Resolution:

After speaking to a senior Citrix support specialist, he directed me to an old Citrix article.  Applying the Registry key changes mentioned solves the issue (TWISeamlessFlag = 1)

For x86 systems:

1. Edit the registry:
HKEY_LOCAL_MACHINE\Software\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\WFClient

2. Create a string value, REG_SZ, called TWISeamlessFlag with a value data of 1.

For x64 Systems:

1. Edit the registry:
HKEY_LOCAL_MACHINE\Software\ Wow6432Node\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\WFClient

2. Create a string value, REG_SZ, called TWISeamlessFlag with a value data of 1.