SendMessage vs. CALL of Window Procedure

[Michael Mattias]

I thought SendMessage, when used as a FUNCTION, returns the return value of the associated window procedure.

But, when I did this...

FUNCTION TabMainDialogProc (BYVAL hWnd AS LONG, BYVAL wMsg AS LONG, _
                  BYVAL wParam AS LONG, BYVAL lParam AS LONG) EXPORT AS LONG

   SELECT CASE wMSg

    CASE %PWM_QUERY_MARKED           ' private message; wparam = claim_seq_no
                                     ' returns true or false, claim is marked
          ' need to search every item of the listview, query its lparam
          ' until I find the target sequence number
          ' get the item data from the listview, in which the lparam is its pClaim
          'MSGBOX "RECEIVED PWM_QUERY MARKED in TabMain"
          hWndLV = GetDlgItem (hWndTab(%SUB_TAB_CLAIMLIST),%ID_LISTVIEW_CLAIMS)
          lvi.iSubItem = 0
          lvi.mask = %LVIF_PARAM OR %LVIF_STATE
          lvi.Statemask = %LVIS_STATEIMAGEMASK    ' bits 12-15
          K = %FALSE
          FOR I = 0 TO @pOSVP.RFI.nClaim - 1
              lvi.iitem = I
              J = SendMessage (hWndLV, %LVM_GETITEM, 0&, BYVAL VARPTR (lvi))
              pCLaim = lvi.lparam
              IF @pclaim.claim_seq_no = wparam THEN   ' this is the one we want
                ' working OK now      MSGBOX "Found requested claim, seq#=" & STR$(wParam)
                 'MSGBOX "lvi State of target=" & HEX$(lvi.state, 4) ' returns correwct
                 IF lvi.state = %LV_CHECKBOX_SELECTED THEN
                   ' MSGBOX "CHECKBOX SELECTED, SETTING FUNCTION = TRUE"
                    K = %TRUE
                 END IF
                 EXIT FOR
                 ' FUNCTION = ISTRUE (lvi.state AND %LV_CHECKBOX_SELECTED) = %LV_CHECKBOX_SELECTED
               END IF
           NEXT I
          ' MSGBOX "Exiting funtion with K = " & STR$(K)
           FUNCTION = K
           EXIT FUNCTION

And called it like this...

         I = SendMessage (GetParent(GetParent(hwnd)), %PWM_QUERY_MARKED, Claim_seq_no, 0&)
         ' MSGBOX "PWM QUERY FUNCTION RETURNS:" & STR$(I)

... It always returned zero, even why my "debug" code told me the function was being set to %TRUE..

So, I thought I'd just call the function this way:

       I = TabMainDialogProc (GetParent(GetParent(hwnd)), %PWM_QUERY_MARKED, Claim_seq_no, 0&)

This way returned the value assigned to the FUNCTION.

Using SendMessage, I know the message was getting to the right place; but the return value was always zero.

Using the explicit call works, so I am going to do that with a couple of other private messages I need to process.

But I was wondering if I misunderstand how "sendmessage" works. MSDN enlightens (?) us with,

"Return Values.
The return value specifies the result of the message processing; it depends on the message sent. "

Comments appreciated...

MCM

[Dominic Mitchell]

Micheal;
The name of your window procedure implies that it is for a dialog.
If it is, then what you are trying to do will not work. That will
only work for standard windows. To return a result from a dialog
procedure do the following-

SetWindowLong hWndDlg, %DWL_MSGRESULT, lResult
FUNCTION = %TRUE

------------------
Dominic Mitchell

[Michael Mattias]

Thank you, that's exactly what I needed to know. (Works, too).

Your tip led me to check MSDN under the generic "DialogProc" entry, and I noticed there a couple of other "Window" functions which behave differently when the windowproc is a dialog procedure. I guess now I know where to look next time I want to do something like this.

MCM