KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q155088: BUG: ListBox Control Scrolls Slowly

Article: Q155088
Product(s): Microsoft FoxPro
Version(s): MACINTOSH:3.0b
Operating System(s): 
Keyword(s): kbnokeyword kbvfp300bBUG
Last Modified: 17-JAN-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual FoxPro for Macintosh, version 3.0b 
-------------------------------------------------------------------------------

SYMPTOMS
========

When scrolling with the scroll bar in the ListBox control of Visual FoxPro, the
scrolling speed is unreasonably slow. The Visual FoxPro ListBox may be many
times slower than the @...GET-List of version 2.6. The scrolling speed of the
ListBox is not dependent on the RowSourceType of the control or the size of the
data set being scrolled.

WORKAROUND
==========

Do one of the following to workaround this behavior:

- Recreate a ListBox-like object by subclassing a grid with the following
  properties:

  ColumnCount = 1
  DeleteMark = .F.
  RecordMark = .F.
  ScrollBars = 2 - Vertical
  HeaderHeight = 0
  GridLines = 0 - None
  RowHeight = FontSize + 2

  The result will be similar in function to a ListBox and will scroll
  considerably faster with the scroll bar. However, if you are using repeated
  arrow keys to scroll, the grid is slower than the ListBox.

  One limitation of this approach is the limited selection of RecordSourceTypes
  of the grid as compared to the RowSourcetypes of the ListBox. The following
  tables illustrate this:

  Grid RecordSourceTypes:

  0 - Table
  1 - Alias
  2 - Prompt
  3 - Query (.QPR)

  ListBox RowSourceTypes:

  0 - None
  1 - Value
  2 - Alias
  3 - SQL Statement
  4 - Query (.QPR)
  5 - Array
  6 - Fields
  7 - Files
  8 - Structure
  9 - Popup

- Define and activate a POPUP.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

MORE INFORMATION
================

The following table illustrates the difference in scrolling speed. The test case
used a ListBox sized to show 10 rows and populated with the company field from a
customer table in the Visual FoxPro:Samples:Data folder. The customer table
contains 91 records. The Time column reflects the time necessary to scroll via
the down arrow from top to bottom:

  Machine              Product                  Time     Rate (r/s)
  -------------------- ---------------------    -------- ----------

  Power Mac 9500/132   Visual FoxPro/Mac 3.0     5.5      16.5
  Power Mac 9500/132   FoxPro/Mac 2.6            0.9     102.0
  Power Mac 7100/66    Visual FoxPro/Mac 3.0    26.0       3.5
  Power Mac 7100/66    FoxPro/Mac 2.6            2.8      32.5
  GateWay Pentium120   Visual FoxPro/Win 3.0     0.8     115.0

  Machine Details:

  - Power Mac 9500/132 32MB, VM 40MB, 7.5.3, ATI XClaim GA 4MB-
    1024x768xMillions

  - Power Mac 7100/66 AV 16MB, 24MB VM, 864x624xThousands

  - GateWay Pentium120, Windows NT Server 3.51,SP3, 32MB, 44 MB Swap,
    ATI PCI Video 2MB-1024x768x256

Additional query words: speed crawl redraw performance

======================================================================
Keywords          : kbnokeyword kbvfp300bBUG 
Technology        : kbHWMAC kbOSMAC kbVFPsearch kbAudDeveloper kbVFP300bMac
Version           : MACINTOSH:3.0b

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.