Q137963: PRB: Disabled Grid Controls Can Be Selected with Mouse

Article: Q137963
Product(s): Microsoft FoxPro
Version(s): 
Operating System(s): 
Keyword(s): 
Last Modified: 26-AUG-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
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SYMPTOMS
========

You are able to use the mouse to select a disabled grid control. The control
appears to have the focus, but no editing can be performed.

This can occur when:

- A grid column has an Enabled property set to true.

  -or-

- A control inside the grid column has an Enabled property set to true.

  -or-

- The When event returns a false.

This situation can also arise when you press the UP ARROW or DOWN ARROW key under
either of these ircumstances:

- The column is disabled, and you select a control on the column by using the
  mouse. Then you can use the UP ARROW and DOWN ARROW keys to move the focus up
  and down the disabled column.

  -or-

- The DynamicCurrentControl property is used to set the current control to a
  disabled control. Then you can use the UP ARROW and DOWN ARROW keys to move
  up or down from the disabled control.

CAUSE
=====

This is normal behavior for the Grid object. This situation occurs because the
Grid object must change the record pointer before it can query columns or column
controls for enabled = true. Once the record pointer is changed, the grid can't
go back because the grid does not save a previous record pointer.

It might be argued that the grid should leave the focus on the prior column
before the user switches to the disabled column or control, but this leads to
problems when handling two special cases:

- When the grid is entered for the first time, and there is no prior column.

- When DynamicCurrentControl is used and the current control for the previous
  column gets set to a disabled control.

In addition, the grid must behave this way to accommodate the following special
case. If all the columns of a grid are disabled and the RecordMark and
DeleteMark properties are set to false, the user needs to have a way to change
the record pointer within the grid.

RESOLUTION
==========

Include code in the AfterRowColChange event to handle cases in which the column
is being changed to a disabled column or control. Following are two examples of
code to accomplish this.

Example One
-----------

The following example demonstrates the simplest case. For this example, assume
that column one is always disabled, column two is never disabled, and horizontal
scrolling is disabled.

     LPARAMETERS nColIndex

     * LPARAMETERS statement required and inserted by Visual FoxPro

     * Check to see if you're on column one
     IF nColIndex = 1
         * Change the active cell
         WITH This
             .ActivateCell(.RelativeRow, 2)
         ENDWITH
     ENDIF

NOTE: This example makes use of the RelativeRow property. Do not use the
ActiveRow property; it will not work properly. Note that the ActiveCell method
assigns the focus to column two even if column two is disabled or the current
control in column two is disabled.

Example Two
-----------

The following example is slightly more robust. It can be used on scrollable
grids, where the columns or controls may have a variable enabled setting. The
code first checks to make sure that the current column is valid. If it is not,
it starts moving through the available columns until it finds a valid column for
input focus, and then sets the focus. The code wraps from the last column to the
first, taking into account that several controls may exist within the column.
The code leaves the focus on the current column if no columns are enabled.

     LPARAMETERS nColIndex

     * LPARAMETERS statement required and inserted by Visual FoxPro

     LOCAL iLoop, iMax, lFocusSet

     WITH This && Grid

        * Initialize Loop Variables
        iMax = .ColumnCount
        iLoop = nColIndex + 1

        * Check if current column is valid
        WITH .Columns(nColIndex)
           * Column is valid only if the Column's Enabled Property is True
           * and the CurrentControl's Enabled Property is True

           * Note: The EVAL function (cf. EVALUATE() online help) is used as
           * as an alternative to macro substitution for accessing the
           * column's current control

           lFocusSet=.Enabled .AND. EVAL("." + .CurrentControl + ".Enabled")

        ENDWITH

        * Start at next column (to the right) and cycle through all columns
        * until a valid column is reached or loop returns to current column

        * Note: If the current column is valid, lFocusSet = true and this
        * loop is skipped
        DO WHILE iLoop # nColIndex .AND. .NOT. lFocusSet
           * Wrap to first column if necessary
           IF iLoop > iMax
              iLoop = 1
           ELSE

              WITH .Columns(iLoop)
                 * If this column is Valid (same criteria as above)
                 IF .Enabled .AND. EVAL("." + .CurrentControl + ".Enabled" )
                    * Set focus to column and end loop
                    .SetFocus
                    lFocusSet = .T.
                 ENDIF
              ENDWITH
              * Advance to next column
              iLoop = iLoop + 1
           ENDIF
        ENDDO
     ENDWITH

NOTE: This example does not take into account columns or controls within columns
that have a When event that returns False.

STATUS
======

This behavior is by design.

Additional query words: VFoxWin

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300

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