If users of XenApp/XenDesktop 7.x report flickering icons or elements of menus including the Start menu, whereby small elements of the desktop are refreshed at an excessively high rate, this is an indication that the incorrect graphics mode has been configured. The default graphics mode for XenApp/XenDesktop 7.x is modern Thinwire, which is designed for modern Windows OS versions such as Windows Server 2012 [R2], but with legacy Windows Server 2008 R2 the correct graphics mode is Legacy mode. Flickering icons or menu objects are observed when either the DeepCompressionEncoder, DeepCompressionV2Encoder or CompatibilityEncoder are in use. The graphics encoding mode currently in use can be determined by following the advice in this Citrix blog : Citrix XenDesktop/XenApp – How to Determine HDX Display Mode

Many users will be unaffected

Some users of 2008 R2 will be unaware of this issue as it will only occur when high-frame rates are possible, i.e. on a quality, uncongested LAN, whereas many users may be on networks where frame rates are limited.

To resolve the flickering issue:

• Switch to Legacy graphics mode via the policies in Studio. Legacy graphics mode was designed and optimized for legacy Windows OSes (including Windows Server 2008 R2 and Windows 7 and below) and as such is designed to provide a good experience.

• Alternatively, upgrade to Windows 2012 R2 where the issue is not observed with modern Thinwire.