DDT and %GWL_USERDATA

[Peter Stephensen]

I like to use SetWindowLong(hWnd, %GWL_USERDATA , VARPTR(udt)) when creating dialogs to avoid global variables. This can not be done in DDT because DDT uses %GWL_USERDATA.
Instead i have tried the following method: Define
%DDT_USERDATA = %DWL_MSGRESULT
and then use SetWindowLong(hWnd, %DDT_USERDATA , VARPTR(udt)).
It seems to work OK. But is it OK?
%DWL_MSGRESULT is explained as: "Sets the return value of a message processed in the dialog box procedure".

Regards
Peter

[Semen Matusovski]

Peter --
Perhaps, this is Ok for WM_INITDIALOG and 99,99% sure that DDT doesn't use it for own purposes.
But when %WM_INITDIALOG is processed, this field will be destroyed.
Sample:

   #Compile Exe
   #Register None
   #Dim All
   #Include "win32api.inc"
   CallBack Function hDlg_CB()
      Select Case CbMsg
         Case %WM_INITDIALOG
            SetWindowText CbHndl, Time$ + Str$(GetWindowLong(CbHndl, %DWL_MSGRESULT))
         Case %WM_ERASEBKGND
'            SetWindowText CbHndl, Time$ + Str$(GetWindowLong(CbHndl, %DWL_MSGRESULT))
      End Select
   End Function

   Function PbMain
     Dim hDlg As Long
     Dialog New 0, "Select Test", , , 500, 260, %WS_SYSMENU To hDlg
     Control Add TextBox, hDlg, 101, "", 10, 120, 480,  110
     SetWindowLong hDlg, %DWL_MSGRESULT, 125
     Dialog Show Modal hDlg, Call hDlg_CB
   End Function

Uncomment second SetWindowText, try another event (WM_SIZE, WM_PAINT).

Why I thought about caption ?
Clear that not DDT, not OS will touch it.

PS. Interesting, what DDT keeps in GWL / DWL USERDATA ?
Could be something useful ?


[This message has been edited by Semen Matusovski (edited April 01, 2000).]

[Peter Stephensen]

Thanks Semen.
You are right. Interesting what DDT keeps in GWL_USERDATA.

Regards
Peter

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[Lance Edmonds]

R&D have not released any information on what DDT uses the
%GWL_USERDATA storage for, except to say that it is definately reserved for use by the DDT engine and therefore must not be used by applications using DDT.



------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>