PRB: Clicking a Disabled Item in a List Box Selects It

• Microsoft Visual FoxPro for Windows, version 3.0

SYMPTOMS

One or several items in a list box are disabled. If a disabled element is clicked and then enabled, it becomes the selected item in the list.

CAUSE

The value property of the combo box determines which item is displayed. This property is modified when you scroll through a list and the LISTINDEX property varies. Clicking any item in a list, even if it is disabled, changes the LISTINDEX property. If the element is then enabled, the LISTINDEX property is still set to this item, and the list box value is set to the value of the element.

WORKAROUND

An alternative is to compare the elements referred by the LISTINDEX and the VALUE properties. If the VALUE property of the combo box is different from the value of the element referred by LISTINDEX, reset the listindex property to the value property. You can then enable the list element.

STATUS

This behavior is by design.

MORE INFORMATION

The following example program illustrates a workaround to the behavior described. It displays a form with a combo box and a command button. The command button enables all of the items in the list. When the button is clicked, the program checks if the value of the combo box corresponds to the listindex. If it does not, the listindex is reset.

To run this sample program, copy and paste the code into a program file (.PRG file), and run it. When the list is displayed, click the third element, which is disabled. Then click the command button. The element displayed in the text part of the combo box does not change.

Example Workaround Code

oForm1=CREATE('myform') oForm1.SHOW

*:************************************************************************* *: *: Class: myform BaseClass: FORM *: *:************************************************************************* DEFINE CLASS myform AS FORM

      Dimension astep(4,1)
      WindowType=1
      ADD OBJECT combo1 AS COMBOBOX WITH HEIGHT = 37,LEFT = 48,;
        STYLE = 2,TOP = 24
      ADD OBJECT cmdenable AS COMMANDBUTTON WITH TOP = 72,LEFT = 48,;
        HEIGHT = 37,WIDTH = 157,CAPTION = "Enable Steps 2-4"
      PROCEDURE cmdenable.CLICK
         DO CASE
         * The case statement takes into account the fact that the
         * value can be a character. It then goes through the list
         * and finds the index that corresponds to the current value
         * and resets the listindex.
         CASE TYPE('THISFORM.COMBO1.VALUE')="C"
            IF THISFORM.combo1.VALUE <> ;
               THISFORM.combo1.LIST(THISFORM.combo1.LISTINDEX)
               i = 1
               lexit=.F.
               DO WHILE i <= THISFORM.combo1.LISTCOUNT AND lexit=.F.
                  IF THISFORM.combo1.LIST(i)=THISFORM.combo1.VALUE
                     nNewIndex=i
                     lexit=.T.
                  ENDIF
                  i=i+1
               ENDDO
                THISFORM.combo1.LISTINDEX=nNewIndex
               ENDIF

         CASE TYPE('Thisform.combo1.value')="N"
             IF THISFORM.combo1.VALUE<> THISFORM.combo1.LISTINDEX
               THISFORM.combo1.LISTINDEX=THISFORM.combo1.VALUE
            ENDIF
         ENDCASE

         FOR m.i = 2 TO 4
            THisform.aStep[m.i, 1] = STRTRAN(Thisform.aStep[m.i, 1], '\')
         ENDFOR

         THISFORM.combo1.REQUERY

      ENDPROC

      PROCEDURE INIT
         This.aStep[1,1] = 'Step 1'
         This.aStep[2,1] = '\Step 2'
         This.aStep[3,1] = '\Step 3'
         This.aStep[4,1] = '\Step 4'
         THIS.combo1.ROWSOURCETYPE = 5
         THIS.combo1.ROWSOURCE = 'Thisform.aStep'
         THIS.combo1.VALUE = 1
      ENDPROC
   ENDDEFINE