Agrid.exe Navigates to Non-Visible Grid Cells in Visual FoxPro

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In Visual FoxPro, the ActivateCell() method of a grid can be used to change the active cell in a grid. However, ActivateCell() works only for cells that are visible in the grid. A grid may have thousands of rows and more columns than can be shown. These rows and columns can be accessed if the user scrolls the grid or uses the navigation keys (page up, page down, arrow keys, and so forth) to move to them. The sample .vcx file contains a class based on a grid that has a custom method to allow access to any cell in the grid, visible or not.

To use the files included, follow these steps:

1. Download the Agrid.exe or Agrid.hqx file and place it in a new folder.
2. Select Agrid.exe or Agrid.hqx to extract the files.
3. Once the files are extracted, start Visual FoxPro.
4. In Visual FoxPro, set the default directory to the location of the files through the Tools, Options dialog box, File Locations tab or with the SET DEFAULT TO command.
5. The sample form, Gridtest.scx, uses the TestData!Customer table. This is a sample table installed with Visual FoxPro in the \Samples\Data folder. In Visual FoxPro 6.0, the data is located in the Microsoft Visual Studio\Common\Data folder. Copy the files from that folder to the folder where the sample files for this article have been saved. Visual FoxPro 5.x users do not need to copy the .qpr, .prg, .pjx and .pjt files from that folder.
6. The form and class library were created in Visual FoxPro 5.0a. To use them in Visual FoxPro 3.x, issue the following commands in Visual FoxPro 3.x to recompile them:

         COMPILE FORM Gridtest.scx
         COMPILE FORM Agrid.vcx
   							

   When using the files in Visual FoxPro for Macintosh, at least for purposes of this article, setting MacDeskTop off is recommended. The following command will do that:

         SET MACDESKTOP OFF
   							

   The form and class library should be recompiled on the Macintosh. Use the commands above in Visual FoxPro for Macintosh.
7. Run the form by issuing DO FORM Gridtest.scx in the Visual FoxPro Command window or by selecting Do from the Program menu, changing the Files Of Type drop-down list to Form, and selecting Gridtest.scx.
8. The syntax for using the custom function of the agrid class is:

         grid.GoToCell(nrow,ncol)
   							

   where nrow and ncol specify the row and column of the cell to make active.
   
   Try these commands in the Command window with the form running to test the custom method:

         gridtest.agrid1.GoToCell(65,7)
   
         gridtest.agrid1.GoToCell(18,5)
         gridtest.agrid1.GoToCell(12,2)
         gridtest.agrid1.GoToCell(1,1)
         gridtest.agrid1.ActivateCell(18,5)  && Note that this will not work.
   							

   NOTE: An "Invalid subscript reference" error message results from either a zero or negative number entered for the column reference.
9. Quit and examine the agrid class in the Agrid.vcx visual class library as desired.

Any improvements to the code in the GoToCell custom method in the agrid class are appreciated.