Numeric or Currency TextBox

[Paul Squires]

A common question is how to filter out unwanted characters from a TextBox. For example, say you need a TextBox to only accept a currency value, then you would allow numbers and the period. Here is an easy way to do it in FireFly (easy, because FireFly already handles the subclassing for you).

Code Select Expand


'--------------------------------------------------------------------------------
Function FORM1_TEXT1_WM_CHAR ( _
                             ControlIndex  As Long,  _  ' index in Control Array
                             hWndForm      As Dword, _  ' handle of Form
                             hWndControl   As Dword, _  ' handle of Control
                             chCharCode    As Long,  _  ' character code
                             lKeyData      As Long   _  ' key data
                             ) As Long

     
   ' If the key pressed is not valid then the WM_CHAR handler
   ' will return TRUE thereby stopping processing of that key.
   Function = ProcessTextBoxKeys( hWndControl, chCharCode )
   
End Function


'--------------------------------------------------------------------------------
Function ProcessTextBoxKeys( ByVal hWndControl As Dword, _
                             ByVal chCharCode  As Long _
                             ) As Long
                             
   ' This function is called from the WM_CHAR message handler for
   ' the TextBox wanting to filter numeric data.
   
   Local fHasPeriod As Long
   Local i          As Long
   Local st         As String
   
   
   st = FF_TextBox_GetText( hWndControl )
   
   fHasPeriod = Instr(st, ".")
   
   Select Case chCharCode
      Case 8     ' backspace (always allow)
         
      Case 48 To 57, 8    ' numbers
         ' only allow two digits after the period
         If fHasPeriod Then
            If Len(Mid$(st, fHasPeriod+1)) >= 2 Then Function = %TRUE
         End If   
         
      Case 46   ' period (only allow one)
         If fHasPeriod Then Function = %TRUE
         
         ' Don't allow the period to be placed any further back than
         ' the last two numbers.
         i = FF_TextBox_GetSelStart( hWndControl ) + 1     
         If Len(st) - i >= 2 Then Function = %TRUE
           
   
      Case Else  ' don't allow anything else
         Function = %TRUE
         
   End Select
                             
End Function
             


[Paul Squires]

This type of numeric/currency TextBox looks best when the TextBox has the ES_RIGHT WindowStyle set.