Configuration of Client scaling, DPI scaling, and DPI matching with Citrix Workspace app for Windows

This article presents typical customer use cases and associated configuration options, requirements, limitations, and recommendations for displaying sessions on high resolution monitors.

Multiple or single high resolution monitors connected to Windows endpoint machines can result in published apps & desktop sessions displaying at resolutions that are not optimal for the user, as well as text and icons sizes in desktop sessions that are not optimal for the user.

Broadly there are two approaches to resolving these issues:

  1. Session scaling.
    • The session’s display is scaled up on the client so that text, icons and other object display at the desired size. This limits the resolution handled by the VDA, improving server scalability. The down side to this is that text and other fine detail images may appear blurry due to the scaling.
  2. No session scaling.
    • An unscaled session will display at a higher resolution rather than scaling up the session. Consequently, text, icons, and other objects can appear much smaller than those on the endpoint monitor. However, if specific Citrix component versions and Windows OS version requirements are met, the DPI value on the endpoint monitor can be matched for the desktop session so that text and icon sizes will match that of the endpoint monitor. This feature is calledDPI matching.

Note: This article mentions “Mixed DPI”. This refers to endpoint setups where different DPI scaling settings have been configured across multiple monitors.

Available configuration methods for client scaling, DPI scaling, and DPI matching

Settings can be configured through Receiver for Windows and Citrix Workspace app for Windows group policy settings, or through the Advanced Preferences UI in Receiver for Windows and Citrix Workspace app for Windows.

GPO configuration

To configure DPI scaling using the Citrix Receiver Group Policy Object administrative template (administrators only)

  1. Open the Citrix Receiver Group Policy Object administrative template by running gpedit.msc.
  2. Under the Computer Configuration node, go to Administrative Templates > Citrix Components > Citrix Receiver > DPI
  3. Select High DPI policy.
  4. Change the settings as required.
  5. Click Apply and OK.
  6. From a command line, run the gpupdate /force command.
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Receiver for Windows or Citrix Workspace app for Windows Advanced Preferences UI configuration:

To configure DPI scaling using the graphical user interface:

Note:

You can hide all or part of the Advanced Preferences sheet available from the Citrix Workspace app icon in the notification area. For more information, see Hiding the Advanced Preferences sheet.
  1. Right-click Citrix Receiver for Windows from the notification area.
  2. Select Advanced Preferences and click DPI settings. The DPI settings dialog appears.
  3. Change the settings as required. By default, the option Let the operating system scale the resolution is selected.
  4. Click Save.
  5. Restart the Citrix Receiver for Windows session for the changes to take effect.
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Use cases

There are three possible settings for DPI Scaling in the receiver, Scaled, Unscaled and Operating system Scaling. The use cases for the different settings are as follows:

Use case: Operating System Scaling (also known as DPI scaling)

OS scaling is the default and is identical in behavior to previous receiver versions. This corresponds to the UI setting “Let the operating system scale the resolution”, or the High DPI policy set to disabled. This lets Windows handle all DPI scaling. The resolution on the VDA will be scaled and based on the DPI, resulting in a smaller resolution than the client device. This works well for single monitor sessions, and is efficient when connecting to XenApp 6.5 hosts, or supported XenApp/XenDesktop VDAs configured for Legacy Graphics.

This method does not support Mixed DPI; all monitors must have the same DPI or the session will not work. Scaling can cause blurriness in the images, particularly in the case of text. This setting is recommended for users on Windows 7 endpoints if DPI matching is not possible, or those connecting to Legacy VDAs. It can also be used on Windows 10 if there is no Mixed DPI.

Enhancements to the Operating System scaling since Receiver for Windows 4.10

Citrix Workspace app (CWA) for Windows version 1808

CWA for Windows version 1808 provides improvements in graphics quality for sessions using legacy graphics mode (GDI graphics mode), when DPI Scaling is enabled on the client.

Note: The Legacy graphics mode HDX policy can be used for any currently supported Server OS VDA version that supports Windows Server 2008 R2.

The feature enhancement leverages DirectX 11-based scaling on the client where CWA for Windows version 1808 is installed. Because of this, this feature enhancement is not available for Windows 7 client endpoints; as Windows 7 does not support DirectX 11.

Graphics quality improvements will also be seen in double-hop scenarios. Refer to the list below for use cases that support this feature enhancement:

Single-hop

Client endpoint OS: Supported versions of Windows 10 with CWA for Windows installed and DPI Scaling enabled.

VDA OS: Windows Server 2008 R2.

Double-hop

Client endpoint OS: Supported versions of Windows 10 with CWA for Windows installed and DPI Scaling enabled.

1st hop VDA OS: Citrix support versions of Windows 10 with CWA for Windows installed and DPI Scaling enabled.

2nd hop VDA OS: Windows Server 2008 R2.

Notes:

DPI scaling functionality is supported with HDX Windows media redirection, Flash redirection and Browser content redirection features with XenApp and XenDesktop 7.16 (and higher versions).


Use case: Scaled (also known as client scaling)

The Scaled setting will scale the resolution on the VDA similarly to OS Scaling, however this setting will support mixed DPI scenarios. This corresponds to the UI setting “Yes”, or the High DPI policy set to enabled and the option for “Scale the session for high resolution” set to “Yes”. This setting works well for mixed DPI scenarios when connecting to supported XenApp & XenDesktop and Citrix Virtual Apps & Desktops VDAs. This is the only way to scale Seamless sessions with mixed DPI.

Considerations when using Scaled configuration:

  • Scaling can cause blurriness in the images, particularly in the case of text.
  • There can be poor performance when connecting to Legacy VDAs (XenApp 6.5, or supported VDAs configured for Legacy Graphics).
  • Local App Access, RTOP, and other plugins that use the window positioning API do not work with Scaling.
  • Seamless apps will “jump” between monitors in this mode to maintain correct scaling, this is by design.

This setting is recommended for users on Windows 10 endpoints connecting to currently supported VDAs. It supports mixed DPI without any additional impact on server resources.


Use case: Unscaled (includes DPI matching feature)

This corresponds to the UI setting “No”, or the High DPI policy set to enabled and the option for “Scale the session for high resolution” set to “No”.

This setting should not cause any blurriness due to scaling because the full-unscaled resolution of all monitors is sent to the session.

Enabling the unscaled setting will create sessions with higher resolution (as compared to scaled sessions), which can impact server performance and scalability, as well as increased bandwidth usage over the HDX connection. For this reason, customers will need to decide whether configuring for unscaled or scaled is more suited to their needs.

This setting is recommended for desktop sessions requiring the best image quality, where the additional server resource usage is acceptable.

Unscaled with DPI matching

The desktop session will launch with a DPI value that matches the DPI value of the endpoint monitor on which the session displays. This will result in text, icon and other object sizes in the desktop session matching that of the endpoint’s monitor.

It is also possible for users to change the endpoint monitor’s DPI value mid-session, which will correspondingly change the desktop session’s DPI value to match. Doing so will also change the desktop session’s display resolution.

Requirements:

  • Endpoint: Windows 7 or Windows 10 with minimum Citrix Workspace app for Windows 1811 installed.
  • VDA: Windows 10 with minimum VDA version 1811 installed.

Limitations:

  • The DPI matching feature is only supported for desktop sessions; seamless sessions are not supported.

Unscaled without DPI matching

When DPI matching is not possible, the unscaled setting will still mean the full resolution is sent but without DPI matching. This can result in small text and icons in apps and desktop sessions.

The DPI can still be set within the VDA after session launch, resulting in the desired text and icon sizes, though this is not possible on RDS desktops, or seamless applications.

Requirements:

  • Endpoint: Windows 7 or Windows 10 with minimum Receiver for Windows 4.10 installed (4.11 recommended to resolve some display issues).
  • VDA: Currently supported VDA versions on supported Windows Server OS and Desktop OS versions.

Limitations:

  • Even with one of the High DPI settings enabled, a slight blur has been observed in the desktop viewer UI.
  • In a session, when you change the DPI settings and relaunch it, the size of the session window might not be appropriate. As a workaround, resize the session window.

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