DDT Subclassing, What am I doing wrong?

[Gregery D Engle]

Guys, I'm trying to make a way to be able to do this:


SHOWDDT hDlg&, CODEPTR(dlgProc)

The key is that I don't want any global variables, so
I use a function with STATIC vars to keep track of all
the hwnd's and DDT CodePtr's. However, when I run this,
it seems as if DDT is getting any of the messages.


Here is what I have so far.

#COMPILE EXE
#INCLUDE "win32api.inc"
%DEBUGMODE = 1

TYPE SubClassStruct
    hWnd AS LONG
    lpPrevWndFunc AS LONG
END TYPE
    
DECLARE CALLBACK FUNCTION DlgProc()

SUB DEBUG_PRINT (SOut AS STRING)
   #IF %DEBUGMODE
       STATIC hConsole AS LONG, cWritten AS LONG
       IF hConsole = 0 THEN AllocConsole: hConsole = GetStdHandle(-11&)
       WriteConsole hConsole, BYCOPY sOut + $CrLf, LEN(sOut) + 2, cWritten, BYVAL 0&
   #ENDIF
END SUB

SUB CodePTRList(hWnd&, lCodePTR&)
    STATIC SubClass() AS SubClassStruct
    STATIC lDialogs&
    DEBUG_PRINT "Number of dialogs: " & STR$(lDialogs&)
    IF lDialogs& = 0 THEN
        REDIM SubClass(0 TO 99)
    END IF

    FOR lCounter& = 0 TO lDialogs&
        IF SubClass(lCounter&).hWnd& = hWnd& THEN
            lCodePTR& = SubClass(lCounter&).lpPrevWndFunc&
            EXIT SUB
        END IF
    NEXT

    INCR lDialogs&
    SubClass(lDialogs&).hWnd& = hWnd&
    SubClass(lDialogs&).lpPrevWndFunc& = lCodePTR&
        
END SUB

FUNCTION SubClassProc(BYVAL hWnd&, BYVAL wMsg&, BYVAL wParam&, BYVAL lParam&) AS LONG
    CodePTRList hWnd&, OldProc&
    DEBUG_PRINT STR$(hWnd&) & " " & STR$(OldProc&)
    a& = CallWindowProc(OldProc&, hWnd&, wMsg&, wParam&, lParam&)
END FUNCTION

CALLBACK FUNCTION DlgProc() AS LONG
    DEBUG_PRINT "DLGPROC..." & STR$(CBMSG)
END FUNCTION

FUNCTION PBMAIN() AS LONG
    DIALOG NEW 0, "This is a Test",,, 160, 50, Style&, eStyle& TO hDlg&   'CALL DWORD CODEPTR(DlgProc())
    CodePTRList hDlg&, SetWindowLong(hDlg&, %GWL_WNDPROC, CODEPTR(SubClassProc))
    DIALOG SHOW MODELESS hDlg&, CALL DlgProc()
    DO
        DIALOG DOEVENTS
    LOOP
END FUNCTION

------------------
-Greg



[This message has been edited by Gregery D Engle (edited July 20, 2001).]

[Lance Edmonds]

Well, a few things for you:

1. The code is not thread-safe (use of static variables without synchronization control). Search the BBS for "CriticalSection".

2. The subclass function is not returning the dialog procedure return value:
Change:

a& = CallWindowProc(OldProc&, hWnd&, wMsg&, wParam&, lParam&)

to:

FUNCTION = CallWindowProc(OldProc&, hWnd&, wMsg&, wParam&, lParam&)

However, since a dialog callback will likely process a very large volume of mesages, your code is adding a significant amount of overhead because it is enumerating your array with every single message the subclassed callback processes.

I'm not clear on what you really want to achieve here, but I think your current approach may need to be reconsidered.

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

[Gregery D Engle]

Lance,

Thanks for your help. I'm just trying to do some crazy ideas
that I came up with, using DDT. My code is only enumerating
the array by the number of dialogs that are being controlled.

I don't see how that is going to slow it down that much.

------------------
-Greg

[Gregery D Engle]

Lance,

I read some topics about CriticalSection and this is what I came
up with, is this Thread Safe?

SUB CodePTRList(hWnd&, lCodePTR&)
    DIM gtCritSect AS CRITICAL_SECTION
    InitializeCriticalSection gtCritSect
    
    EnterCriticalSection gtCritSect
    STATIC SubClass() AS SubClassStruct
    STATIC lDialogs&
    DEBUG_PRINT "Number of dialogs: " & STR$(lDialogs&)
    IF lDialogs& = 0 THEN
        REDIM SubClass(0 TO 99)
    END IF

    FOR lCounter& = 0 TO lDialogs&
        IF SubClass(lCounter&).hWnd& = hWnd& THEN
            lCodePTR& = SubClass(lCounter&).lpPrevWndFunc&
            EXIT SUB
        END IF
    NEXT

    INCR lDialogs&
    SubClass(lDialogs&).hWnd& = hWnd&
    SubClass(lDialogs&).lpPrevWndFunc& = lCodePTR&
    LeaveCriticalSection gtCritSect
END SUB

------------------
-Greg

[Lance Edmonds]

Firstly, you'll probably need the critical_section variable to be global.

Basically, you must call InitializeCriticalSection just once at the start of the app. Although you could probably do it by making it a STATIC variable in the subclass function, and ensuring it is only called one per thread. Ditto for DeleteCriticalSection().

The calls to EnterCriticalSection() and LeaveCriticalSection(), etc, should stay as they are in that function.

Out of curousity, when testing your code, have you tried counting the number of messages that flow though the subclass and/or callback function? You may be surprised at the numbers you get.

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

[Gregery D Engle]

Lance,

Ok, I'll make the changes that you recommend.

No I haven't counted the messages yet, but with my tests so
far I don't see any slowness whatsoever.

------------------
-Greg