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.


Introducing The End User Computing Podcast

Over the last several years, many of us in the industry have discussed the need for community driven End User Computing podcasts focusing on virtualization topics for people designing, deploying, and using Citrix, Microsoft, VMware and surrounding†technologies. I am excited to share that this month, two new Podcasts are being launched! First, a warm congratulations to Jarian Gibson and Andy Morgan on the successful launch of their Podcast, Frontline Chatter. Here’s to many years of continued success! Next, allow me to introduce the End User Computing Podcast!

Continue reading

At E2EVC (Experts to Experts Virtualization Conference) 2-4th November 2012, RES Software showed a sneakpeak from their new IT Store, that will be released in 2013.

My opinion, “I love the new looks of the new client, its simplified and “VERY” userfriendly and it does what the user needs” its build for the new Windows 8 feel and look.

The IT Store is the new client, and the new name that replaces the Service Orchestration Client for Automation Manager. The IT Store will be available in 2013.

The new login screen

The new user interface that the users will see, when the request services.


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