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Mitigation: WPF Window Rendering

In the .NET Framework 4.6 running on Windows 8 and above, the entire window is rendered without clipping when it extends outside of single display in a multi-monitor scenario.

Impact

In general, rendering an entire window across multiple monitors without clipping is the expected behavior. However, on Windows 7 and earlier versions, WPF windows are clipped when they extend beyond a single display because rendering a portion of the window on the second monitor has a significant performance impact.

The precise impact of rendering WPF windows across monitors on Windows 8 and above is not precisely quantifiable since it depends on a large number of factors. In some cases, it may still produce an undesirable impact on performance, particularly for users who run graphics-intensive applications and have windows straddling monitors. In other cases, you may simply want a consistent behavior across .NET Framework versions.

Mitigation

You can disable this change and revert to the previous behavior of clipping a WPF window when it extends beyond a single display. There are two ways to do this:

  • By adding the <EnableMultiMonitorDisplayClipping> element to the <appSettings> section of your application configuration file, you can disable or enable this behavior on apps running on Windows 8 or later. For example, the following configuration section disables rendering without clipping:

    <appSettings>
    <add key="EnableMultiMonitorDisplayClipping" value="true"/>
  </appSettings>

    The <EnableMultiMonitorDisplayClipping> configuration setting can have either of two values:

    • true, to enable clipping of windows to monitor bounds during rendering.

    • false, to disable clipping of windows to monitor bounds during rendering.

  • By setting the EnableMultiMonitorDisplayClipping property to true at app startup.

See also