Skip to main content

Mozilla Firefox 40.x Blocks GPU Acceleration for WebGL, Direct2D, DirectWrite with Citrix XenApp on Windows 2008R2/2012/2012R2

Mozilla Firefox 40.x Blocks GPU Acceleration for WebGL, Direct2D, DirectWrite with Citrix XenApp on Windows 2008R2/2012/2012R2

One of the great things about adding a GPU in a Citrix XenApp environment is that you can allow rich graphics and offload CPU and run your DirectX, OpenGL  applications on a XenApp server. In latest version of Mozilla Firefox WebGL, Direct2D, DirectWrite this have been disabled, so you can’t open webpages that uses these graphics in a Citrix XenApp session.

Symptoms or Error

If you open Mozilla Firefox 40.x and try to open a webGL website like
this will not load anymore cause WebGL is default now disabled in Mozilla Firefox. Mozilla Firefox 40.x  blocks GPU acceleration for WebGL, Direct2D, DirectWrite in remote sessions on Windows Server operating systems.


To determine what content Firefox is blocking, run Firefox in your XenApp remote session and enter the address about:support into the browser address bar. In the section labelled “Graphics” you will see the following content disabled (as of Firefox version 40.0.3):

Direct2D Enabled             Blocked for your graphics card because of unresolved driver issues.
DirectWrite Enabled         false (6.3.9600.17999)
WebGL Renderer             Blocked for your graphics card because of unresolved driver issues.



The text “Blocked for your graphics card” is misleading as, in this case, it is not the specific graphics card but general Windows Server operating system remote sessions that are blocked. Mozilla’s published advice on how to override the graphics driver blocks also applies to XenApp sessions on workstation operating system (see bottom of this Mozilla Wiki – Blocklisting/Blocked Graphics Drivers).

Enable WebGL in Mozilla Firefox

In Mozilla Firefox entering the address about:config into the address bar and setting webgl.force-enabled=true will enable WebGL for XenApp on operating system (Server 2008R2/2012/2012R2)



You can double click on it and then it will become enabled. (with the value=true) and this is user set.
These settings can be change with a policy or with profile management such as RES Workspace Manager or others.


Now you can open the WebGL demo and the graphics will work


Enable DirectDraw2D

In Mozilla Firefox entering the address about:config into the address bar and setting gfx.direct2d.force-enabled=true will enable WebGL for XenApp on operating system (Server 2008R2/2012/2012R2)


You can double click on it and then it will become enabled. (with the value=true) and this is user set.
These settings can be change with a policy or with profile management such as RES Workspace Manager or others.


Enable DirectDraw2D

In Mozilla Firefox entering the address about:config into the address bar and setting gfx.font_rendering.directwrite.enabled=true will enable DirectWrite for XenApp on operating system (Server 2008R2/2012/2012R2)


You can double click on it and then it will become enabled. (with the value=true) and this is user set.
These settings can be change with a policy or with profile management such as RES Workspace Manager or others.


Users should be aware and note the caveats and warnings that Mozilla advises if taking this route to above settings for DirectWrite, Direct2D, WebGL

This issue only affects server operating system (example – Win 2012 R2 and Win 2008 R2) and XenApp.

How to force-enable blocked graphics features

If you would like to forcibly enable a graphics feature that is blocked on your system, follow these instructions. Warning: do this at your own risk. There usually are good reasons why features are blocked.

To force-enable WebGL, go to about:config and set webgl.force-enabled=true.

To force-enable WebGL anti-aliasing, go to about:config and set webgl.msaa-force=true.

To force-enable Layers Acceleration, go to about:config and set layers.acceleration.force-enabled=true.

On Windows Vista and Windows 7, to force-enable Direct2D Content Acceleration, go to about:config and set gfx.direct2d.force-enabled=true.

On Android, to force-enable StageFright software decoding, go to about:config and set stagefright.force-enabled=true.

On Windows, you can also spoof your graphics system information to help debug driver blacklisting issues (see bug 604771):

  1. Create spoofed-firefox.bat in the installation folder (e.g. C:\Program Files (x86)\Mozilla Firefox)
  2. Set the new values of spoofed variables ending with a command to launch Firefox:
    “C:\Program Files (x86)\Mozilla Firefox\firefox.exe” -p -no-remote
  3. Double-click spoofed-firefox.bat and create a profile if required
  4. Click the Firefox button, then select Help, finally Troubleshooting Information and check the Graphics section.

If force-enabling a feature doesn’t work, that probably means that your hardware doesn’t support it. For example, layers acceleration currently requires support for 4Kx4K textures, which rules out some graphics cards, like the Intel G31/G33.


Firefox article (credits to Rachel Berry for writing this CTX article)

Another great blogpost to read about this subject is my friend / CTP fellow Barry Schiffer He was the guy who wrote a great blogpost with some very interesting results on performance tuning Mozilla Firefox in a XenApp/XenDesktop session.


Whitepaper – Best Practice RES Software: Workspace Manager Advanced Connection States for laptops

RES Software have released a best practice whitepaper on how to configure advanced connection states for laptops with RES Workspace Manager.
If you are using RES Software Workspace Manager and Windows 7 combined with your laptops this is a “must read” whitepaper.

About this Guide

This best practice is written for IT professionals, who are going to design, build and/or maintain a RES Workspace Manager managed Windows 7 laptop environment which is fully context aware.


RES Software wants to create insight in understanding the configuration of different connection states. Configuring the correct connection state is essential for a fully working, context aware, Windows 7 laptop environment. The objective of this guide is to zoom in on the connection state detection feature in different scenarios.


This best practice guide is created based on our own experience together with the input and knowledge of our partners and customers, related to Windows 7 laptops in combination with the configuration of RES Workspace Manager.

There are multiple paths you can take and scenarios you can build. In this paper we try to describe RES Workspace technology as simple as possible and deliver a fundament to help you as an IT administrator with context-aware challenges to come.

The shown scenarios are tested and build by ourselves, so combining real life scenarios with proven technology will give you everything you need for a successful implementation.


Context awareness of a laptop environment all starts with detecting the right connection state. Based on the detected connection state, the Workspace is dynamically built. The type of connection (LAN, WAN, VPN, Wi-Fi, UMTS, 3G, HSDPA, etc.) determines in which context the RES Workspace Manager session will start.

Keep in mind that not every connection type has the same bandwidth available, so decisions need to be made what to allow/disallow in which context. Offline is also considered as a connection state.

When switching between connection types (e.g. Wireless to Wired or vice versa) the RES Workspace Manager needs to detect a connection change, determine the current context and perform a refresh of the Workspace.

The configuration that is discussed in this guide contains a Windows 7 laptop environment with RES Workspace Manager installed.
The laptops move between headquarters and external locations. At the external location a connection to the corporate network is allowed. So basically both scenarios result in the same context for RES Workspace Manager Configuration.

Besides these two “online” states the laptop should also be able to work in “offline” state. “Online scenario”


Read the full whitepaper –
Best Practice – Configuring RES Workspace Manager Advanced Connection States for laptops  HERE

RES Workspace Manager 2011 SR4

RES Software have released RES Workspace Manager 2011 SR4, this article explains the new enhancements and improments in RES Workspace Manager 2011 SR4

Enhancements and Improvements in RES Workspace Manager 2011 SR4

App-V: New option to generate user package by App-V on application end

At Composition > Applications > Managed Applications, on the User Settings > Capturing tab, a new capture option for App-V applications has been added: User package generated by App-V on application end. This setting will preserve the App-V package when the application ends.

Cache Updates: Take long time when using many App-V applications

In an environment with a large number of App-V applications, an initial cache update (which will occur e.g. in an environment which uses a provisioning server/golden image) the normal cache updates (objects, resources) could take minutes to complete. An optimization has been made. Now, updating objects and resources will have a higher priority, so they will be completed first.

Desktop Sampler: Several improvements for Uninstall procedure

Several improvements have been made, providing extra Desktop Sampler info in case the automatic uninstall procedure of the DTS should fail:

  • A non verbose logfile is now saved by the msiexec.exe in the user temp directory (defined by the environment variable %temp%) for additional feedback
  • Uninstall could only proceed if the DTSampler GUID was found at the right place in the registry. This has now been changed by a more direct approach.
  • A lot of trace lines have been added. The most important one is feedback about whether the Trace file has been written (or not…).

Environment Variable: Improvement when handling %localappdata% on Microsoft Windows XP

On Microsoft Windows XP machines, the environment variable %localappdata% does not exist. This could pose a problem for configuration items defined in the Management Console and based on %localappdata%. This was already handled as a special case for User Settings, but it will now work for any configuration item. The RES Workspace Manager now uses %userprofile%\local settings\application data as a replacement for %localappdata%. If needed, this behavior can be superseded by defining an environment variable for %localappdata% in the Management Console.

Folder Synchronization: Improved behavior “Run at Interval”

At Composition > Files and Folders > Folder Synchronization, Folder Synchronization tasks that were configured to run at a specific interval, always ran immediately after the session had started. This was not the intended behavior. Folder synchronization tasks now run after the first completed interval. If a Folder Synchronization task MUST also be run during logon, select Run at Logon for the Folder Synchronization task.

Global Authorized Files: Option Logging and default rule for svchost.exe added

At Security > Global Authorized Files, on the Settings tab, a new option Logging and a new default rule for svchost.exe have been added. This security rule determines whether svchost.exe is allowed to start other unmanaged applications or file associations (such as e.g. Windows Media Player and .MP3 files) indirectly.

The Logging option can be used as a Learning mode for this feature. With Logging enabled, security warnings for svchost.exe will be logged. With Logging disabled, no warnings will be logged.

When upgrading from SR3 to SR4, the svchost.exe rule will be added automatically and is enabled by default.

In a new RES Workspace Manager site, the rule will also be created, but it will disabled by default.

Improved Dynamic Privileges

Previously, Dynamic Privileges made use of a temporary administrative account. This is no longer necessary: Dynamic Privileges does not require any special account anymore.

Locations and Devices: Zone rule “Minimum screen resolution” extended

At Context > Locations and Devices, Add/Change Zone, the Zone rule Minimum screen resolution has been extended with ten additional screen resolutions.

RES VDX: RemoteFX now supported by RES Workspace Manager

The following enhancement has been made to RES VDX:

  • RemoteFX is now supported by RES Workspace Manager.

RES VDX: Switching between managed sessions with/without RES VDX/Subscriber now supported

The following enhancement has been made to RES VDX:

  • Switching from one managed session with/without RES VDX/Subscriber to another managed session with/without RES VDX/Subscriber is now supported.

RES Workspace Manager Console: Starting Console on local computer slow

Starting a Workspace Manager Console on a local computer account could be very slow if the computer also resides in an Active Directory Domain. This has been fixed.

User Sessions: Cleaning up “guard.lock”

When User Sessions is enabled, and the current session is not logged off normally (e.g. by doing a “reset session” from a Terminal Server console), the guard.lock file will remain in the user’s Home directory. As a result, the user will be unable to log on for another 10 minutes.

The User Sessions mechanism has now been improved to check if the previous session still exists. If this is not the case, the guard.lock file will be deleted, and the session logon will be granted.

User Sessions: Protocol type PCoIP also shown in User Sessions overview

At Diagnostics > User Sessions, PCoIP was not shown in the column Protocol. It now also shows PCoIP for VMWare View when appropriate.

User Settings: Delete targeted items before applying

When starting a user session in which a User Registry was applied, the registry settings would be merged with the existing registry entries. Thus, any “garbage” within the registry tree/keys would not be cleaned up. Targeted items for capturing User Settings on application or user session level, can now be set to be deleted before applying them.

An extra check box, Empty target when applying user setting, has been added to enable/disable this feature. When this check box is enabled, the corresponding User Setting will be deleted before applying the setting.

User Settings: Saved even when .UPR file is empty

When there are no registry settings to be saved in a user settings file (.UPR) file, an empty file would be created anyway. This has been fixed, no new file will be created in this case.

Various improvements in the Dutch translation of RES Workspace Manager

Various improvements have been made in the Dutch translation of RES Workspace Manager.

Workspace Composer: Configurable waiting time before Composer starts

In certain situations it is desirable to have the Workspace Composer wait a few seconds before starting. This can be done by adding the following registry key:


HKLM\Software\RES\Workspace Manager (32-bits) HKLM\Software\Wow6432Node\RES\Workspace Manager (64-bits)



Value name:


Value data:

Number of seconds to wait

Workspace Composer: Restart behavior improved for Microsoft Windows Vista and later

In certain situations, when a user restarted a workstation running Microsoft Windows Vista and later, this initiated a shutdown. The way in which the RES Workspace Composer handles restarts has been improved.

Workspace Composer: Startup time with RES VDX improved

The startup time of Workspace Composer in combination with RES VDX was slower than the Workspace Composer with RES Subscriber. This has been improved.

Workspace Preferences: JPG picture now allowed as Wallpaper

When the options Hide and Limit “Change Desktop Picture” in WM Console were switched off (at Composition > Desktop > Lockdown and Behavior > Personalization by end user), the end user could only select BMP pictures in Workspace Preferences when changing the Windows Background (Wallpaper).

JPG pictures and other graphical formats are now allowed as well.


Download RES Workspace Manager SR4 from RES customer portal here. (Require ID)

To read the fixes in SR4 download  the release notes (require RES ID) here