Listbox: use of %LB_GETSELITEMS

[Eddy Van Esch]

I have a listbox with LB_MULTIPLESEL enabled, so one can select
more than 1 item at the time.
Does anybody have some example sourcecode of reading the pointers
to the listbox items that are selected? I think it is done by sending
the %LB_GETSELITEMS message. It sends back an array of pointers, but
it's not clear to me how to store and process this array...
Kind regards
Eddy


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[Eddy Van Esch]

I found a VB example.. Will convert it to PB and try it out...

   Option Explicit 

    Public Const LB_SETSEL = &H185& 
    Public Const LB_GETSELCOUNT = &H190 
    Public Const LB_GETSELITEMS = &H191 

    Public Declare Function SendMessageLong Lib _ 
          "user32" Alias "SendMessageA" _  
          (ByVal hwnd As Long, _ 
          ByVal wMsg As Long, _  
          ByVal wParam As Long, _  
          ByVal lParam As Long) _ 
          As Long 

    Public Declare Function SendMessageArray Lib _ 
          "user32" Alias "SendMessageA" _  
          (ByVal hwnd As Long, _ 
          ByVal wMsg As Long, _ 
          ByVal wParam As Long, _  
           lParam As Any) _ 
          As Long 

    '  When lParam equals -1, setting wParam to False deselects all 
    '  selections and setting to True selects all entries. 
    '  Setting lParam to any other number selects or deselects 
    '  the index specified, as per the wParam setting. 

Subroutines in Form Containing List: 

    '-------------------------------------------- 
    Public Sub ReturnSelectedIndexes (LB As Control) 
       Dim SizeOfSelectedArray As Long 
       Dim ret As Long 
       ReDim SelectedArray(1 To 1) As Long 

       SizeOfSelectedArray = SendMessageArray(LB.hwnd, _ 
           LB_GETSELCOUNT, 0, 0) 
       ReDim SelectedArray(1 To SizeOfSelectedArray) As Long 
       ret = SendMessageArray(LB.hwnd, _ 
           LB_GETSELITEMS, SizeOfSelectedArray, SelectedArray(1)) 
    End Sub 
    '-------------------------------------------- 
    Public Sub ClearList (LB As Control) 
       Dim ret As Long 
       r = SendMessageLong(LB.hwnd, LB_SETSEL, False, -1) 
    End Sub 
    '-------------------------------------------- 
    Public Sub SelectAll (LB As Control) 
       Dimret As Long 
       r = SendMessageLong(LB.hwnd, LB_SETSEL, True, -1) 
    End Sub 
    '--------------------------------------------

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[Borje Hagsten]

The array must be LONG's and should be used together with
LB_GETSELCOUNT, something like:

  LOCAL lRes AS LONG
  lRes = SendMessage(hList, %LB_GETSELCOUNT, 0, 0)
  IF lRes AND lRes <> %LB_ERR THEN
     REDIM Larry(lRes - 1) AS LONG
     lRes = SendMessage(hList, %LB_GETSELITEMS, lRes, VARPTR(Larry(0)))
     'Larry now contains the items that are selected
  END IF

Added "IF lRes THEN" to sample, for safety..
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[This message has been edited by Borje Hagsten (edited April 05, 2001).]

[Chris Boss]

Eddy;

I find using

LastIndex&=SendMessage(hCtrl, %LB_GETCOUNT, 0,0)-1
IF LastIndex&>=0 THEN
   FOR N&=0 TO LastIndex&
      IF SendMessage(hCtrl, %LB_GETSEL, N&, 0)>0 THEN
          ' do something with the item which is selected 
      END IF
   NEXT N&
END IF

works well since I can process the items one at a time without resorting
to storing stuff in an array.

It works for me !


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[Borje Hagsten]

For small lists, okay. To keep track of a list with 10,000 items,
%LB_GETSELITEMS makes big difference, especially on slow machines.
Remember that the average user machine is <200MHz..


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[Eddy Van Esch]

Chris,
Yes, your method works, but as Borje said, it could take some time
searching large lists.
In the meantime, I found that one can use 3 'methods' to access a
listbox (or any other control):
- sending messages with CONTROL SEND
- sending messages with the API 'SendMessage()'-function
- or using the predefined functions in 'Commctrl.inc'
I think I must choose 1 of the 3 to make my source code look consequent.
The 'Commctrl.inc'-functions look quite handy....
Eddy


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