During a remote desktop session that originates on a Windows Embedded Compact 7 device, the connection bar might leave visual artifacts on an application window when you move the window on the screen. Specifically, this occurs when you move the active application window behind the connection bar and then out again.

In this article: 

• Cause
• Resolution

Cause

The remote desktop client application caches a bitmap that represents the visual state of the remote application window. When you move the remote application window behind the connection bar, the connection bar overwrites a portion of the cached bitmap.

Resolution

There are currently two ways to address this issue:

• Turn on the Windows Embedded Compact 7 Window Compositor feature. Window Compositor displays overlapping windows on a device screen by using alpha blending. To implement alpha blending, Window Compositor first draws each window to a back-buffer surface in memory. Then it aggregates the window surfaces and composes them on a single back-buffer surface. It then displays the windows on the screen. To use this feature, the screen must be operating in 16-bit or 32-bit color mode.

Window Compositor uses hardware acceleration to render display surfaces. Display performance degrades when the device does not support hardware acceleration. No noticeable performance degradation occurs in a device that supports hardware acceleration. For performance implications on platforms that run Windows Embedded Compact 7 refer to the Window Compositor documentation.

• Turn on the Windows Embedded Compact 7 Shadow Bitmap feature. Shadow Bitmap creates a temporary surface on which the OS paints window bitmaps that the server sends to the device before it draws them on the primary surface. This action prevents Shadow Bitmap from drawing the visual state of the connection bar over the bitmaps that the remote computer sends to the device. Although this method for resolving the connection bar drawing artifact issue differs from the Window Compositor method, the effect is the same. In contrast to the Window Compositor method, Shadow Bitmap does not require hardware acceleration for optimal performance. However, the additional operation Shadow Bitmap requires to operate causes slight performance degradation regardless of device support for hardware acceleration.

Turn on the Window Compositor Feature

To turn on Window Compositor

1.    In Microsoft Visual Studio, add the Window Compositor catalog item to your operating system design.

By doing this you add the SYSGEN_COMPOSITION flag to the operating system design project file.

2.    Rebuild the operating system design to incorporate this change.

Turn on the Shadow Bitmap Feature

Use registry settings to turn on the Shadow Bitmap feature. Windows Embedded Compact reads the settings when the remote desktop client application starts, so they can be set manually on a running operating system, before you start the application, or as part of the operating system design.

To turn on Shadow Bitmap

• Set the following DWORD registry values to 1:

HKEY_LOCAL_MACHINE\Software\Microsoft\Terminal Server Client\Shadow Bitmap Enabled

HKEY_LOCAL_MACHINE \Software\Microsoft\Terminal Server Client\UseShadowBitmapInFullScreen

OR

• Set the following DWORD registry values to 1:

HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Shadow Bitmap Enabled

HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\UseShadowBitmapInFullScreen

Unlike the desktop Windows registry, both registry locations shown here are functionally equivalent because Windows Embedded Compact 7 does not differentiate between users.

See Also

• Window Compositor
• Catalog Item Management
• Sysgen Variables