CreateWindow does not yield a handle nor an errorcode

[Paul_Felz]

Hi there,

in my prog I place a number of windows on my screen. For all except one everything works fine, but for the last one CreateWindow neither returns a handle nor an error code. See this excerpt here:

character*30 :: ccDatenfensterClass = 'DatenfensterClass'C
character*30 :: ccKartenfensterClass = 'KartenfensterClass'C
character*30 :: ccKontrollfensterClass = 'KontrollfensterClass'C
character*30 :: ccStatusfensterClass = 'StatusfensterClass'C

----

cWindowClass = ccDatenFensterClass
tWndClass%style = ior(CS_HREDRAW, CS_VREDRAW)
tWndClass%lpfnWndProc = loc(DatenWndProc)
tWndClass%cbClsExtra = 0
tWndClass%cbWndExtra = 0
tWndClass%hInstance = hhInstance
tWndClass%hIcon = NULL
tWndClass%hCursor = LoadCursor (NULL, IDC_ARROW)
tWndClass%hbrBackground = GetStockObject (WHITE_BRUSH)
tWndClass%lpszMenuName = NULL
tWndClass%lpszClassName = loc (cWindowClass)

iRslt = RegisterClass (tWndClass)


!   Mitte Oben: "Kartenfenster"

cWindowClass = ccKartenfensterClass
tWndClass.lpfnWndProc = loc (KartenWndProc)
tWndClass.lpszClassName = loc (CWindowClass)

iRslt = RegisterClass (tWndClass)

!   Rechte Seite : "Kontrollfenster"

cWindowClass = ccKontrollfensterClass
tWndClass.lpfnWndProc = loc (KontrollWndProc)
tWndClass.lpszClassName = loc (CWindowClass)

iRslt = RegisterClass (tWndClass)

!   Unterer Bereich : "Statusfenster"

cWindowClass = ccStatusfensterClass
tWndClass.lpfnWndProc = loc (StatusWndProc)
tWndClass.lpszClassName = loc (CWindowClass)

iRslt = RegisterClass (tWndClass)


------


!--------------------------------------------------------------------
!           Einrichten des Kontrollfensters
!--------------------------------------------------------------------
            iKontrollTop = 0
            iKontrollWidth = (iWinWidth - iKarteWidth) / 2
            iKontrollHeight = iWinHeight / 2
            iKontrollLeft = iWinWidth - iKontrollWidth

            iStyle = ior (WS_CHILDWINDOW, WS_VISIBLE)                               ! Einrichten als ChildWindow
            iiWindowCount = iiWindowCount + 1

            iiKontrollHandle = CreateWindow (ccKontrollFensterClass,       &
                                ''C,                                    &
                                iStyle,                                 &
                                iKontrollLeft,                          &
                                iKontrollTop,                           &
                                iKontrollWidth,                         &
                                iKontrollHeight,                        &
                                hWnd,                                   &
                                iiWindowCount,                          &
                                hhInstance,                             &
                                NULL)

            print *,' iiKontrollHandle = ', iiKontrollHandle


            iRslt = ShowWindow(iiKontrollHandle, SW_SHOWNORMAL)
            iRslt = UpdateWindow (iiKontrollHandle)

!--------------------------------------------------------------------
!           Einrichten des Statusfensters
!--------------------------------------------------------------------
            iStatusTop = iWinHeight / 2
            iStatusWidth = (iWinWidth - iKarteWidth) / 2
            iStatusHeight = iWinHeight / 2
            iStatusLeft = iWinWidth - iStatusWidth

            iStyle = ior (WS_CHILDWINDOW, WS_VISIBLE)                               ! Einrichten als ChildWindow
            iiWindowCount = iiWindowCount + 1

            iiStatusHandle = CreateWindow (ccStatusFensterClass,        &
                                ''C,                                    &
                                iStyle,                                 &
                                iStatusLeft,                            &
                                iStatusTop,                             &
                                iStatusWidth,                           &
                                iStatusHeight,                          &
                                hWnd,                                   &
                                iiWindowCount,                          &
                                hhInstance,                             &
                                NULL)

            iRslt = GetLastError ()
            print *,' LastError = ', iRslt
            print *,' iiStatusHandle = ', iiStatusHandle

            iRslt = ShowWindow(iiStatusHandle, SW_SHOWNORMAL)
            iRslt = UpdateWindow (iiStatusHandle)

The prints in line #104 and #105 both yield zero while the window before that ("Kontrollfenster") works just fine. The debugger shows all parameters as they are expected to be.

Any Idea on where to start to pinpoint this bug?

Cheers

PF

[Steve_Lionel]

CreateWindow returns something - what is it? Zero?

[Paul_Felz]

Yes. It returns 0.  See attched screenshot of the print to screen.

PF

[Paul_Felz · Accepted solution]

Got it!

This is not an issue with CreateWindow but with the windows procedure attached to the window to be created.

It happens, when the call to DefWindowProc is not performed for unprocessed messages. I had this call in the wrong line.

Problem solved.

Cheers

PF