Article ID: 258537
Article Last Modified on 8/7/2007
APPLIES TO
- Microsoft Visual FoxPro 6.0 Professional Edition
This article was previously published under Q258537
SYMPTOMS
When running Visual FoxPro 6.0 under Microsoft Terminal Services, you may experience severe performance degradation.
CAUSE
In an attempt to increase performance, Visual FoxPro draws to off-screen bitmaps and then puts the whole bitmap on the screen. When running under Terminal Services, this behavior can actually slow performance.
RESOLUTION
Microsoft Visual FoxPro 6.0, with Visual Studio Service Pack 4 and later, includes support for a new Config.fpw switch to prevent these off-screen bitmaps from being drawn. The code is:
BITMAP=OFF
STATUS
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article. This bug was corrected in the latest service pack for Visual Studio 6.0.
For additional information about Visual Studio service packs, click the following article numbers to view the articles in the Microsoft Knowledge Base:
194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why
194295 HOWTO: Tell That a Visual Studio Service Pack Is Installed
To download the latest Visual Studio service pack, visit the following Microsoft Web site:
MORE INFORMATION
When Visual FoxPro writes anything to the screen, it writes first to an off-screen bitmap, and then performs a bit-block (bitblt) transfer to the screen. This results in smoother screen painting.
Software that allows remote access to a Visual FoxPro session (for example, Windows Terminal Server) can detect screen changes, mouse moves, and keyboard events. When one of these events occurs, the software broadcasts it over the network. When Visual FoxPro performs a bitblt operation, the entire region is detected as changed and, therefore, the entire region is sent over the wire to the remote computer.
If you have the line of code "BITMAP=OFF" in your Config.fpw, then the off-screen bitmaps are not used. However, the performance of Visual FoxPro applications in Visual Studio 6.0 Service Pack 4 under Windows Terminal Server without off-screen bitmaps can be significantly faster, depending on your screen size, net speed, and other variables.
NOTE: Microsoft recommends that you do not use this setting for normal Visual FoxPro applications or Component Object Model (COM) servers.
There are some side effects that reduce the functionality of certain Visual FoxPro features so that these features are not particularly useful under Windows Terminal Server:
Streaming Output
Streaming output to a form or to _SCREEN is not refreshed. This means that if you ? something to the screen, and then switch to another window and back again, Visual FoxPro refreshes the screen but does not re-execute the ? function. As a result, the output is not refreshed.
Form Drawing Methods
The refresh issue applies to Form Drawing Methods such as Form.Line, Form.Pset, and so on.
Additional query words: sp4
Keywords: kbbug kbfix kbserver kbtermserv kbvs600sp4fix kbvs600sp5fix kbxbase KB258537
