C / C++ / MFC

19-Sep-01 6:29

Hello,
I am trying to establish a connection and I think I am missing something very basic. I get an "Invalid Pointer" error when the Open() is called. I am importing msado15.dll in StdAfx.h which is included in the file that contains the code below.

My code:
_ConnectionPtr pConn;
HRESULT hr;
try{
hr = pConn.CreateInstance(__uuidof(Connection));
_bstr_t bstrDSN = "DSN=test_db;UID=gstewart;PWD=gstewart";
pConn->Open(bstrDSN,"","", -1);
}
catch (_com_error e){
MessageBox(e.ErrorMessage());
}

ORi x19-Sep-01 6:41

ORi x

19-Sep-01 6:41

try catch (_com_error &e)

Stu19-Sep-01 6:50

19-Sep-01 6:50

The catch block shouldn't be executing in the first place. For some reason my connection pointer isn't valid after
hr = pConn.CreateInstance(__uuidof(Connection));
is executed. Any ideas what I'm missing? I think I'm missing a header file or something. It comiles just fine though....????

Michael P Butler19-Sep-01 11:11

Michael P Butler

19-Sep-01 11:11

This is the code I use to create an ADO connection, the only difference I can see is that I pass cast my empty strings to _bstr_t first.

Are you getting a compile error or a runtime error

_ConnectionPtr m_pConnection
HRESULT CAdoConnection::Connect(std::string sConnectionStr)
{
    HRESULT hr = S_OK;
    try
    {
        hr = m_pConnection.CreateInstance(__uuidof(Connection));
	if(hr == S_OK)
	{
	    hr = m_pConnection->Open(_bstr_t(sConnectionStr.data()), _bstr_t(""), _bstr_t(""), adConnectUnspecified);
	}
    }
    catch (_com_error &e)
    {
    }


    return hr;
}

Michael

Stu19-Sep-01 11:28

19-Sep-01 11:28

Michael,
I tried the casting and also added the adConnectUnspecified argument. My error occurs at runtime on the Open(...).

Thanks,
Glen

Michael P Butler19-Sep-01 22:21

Michael P Butler

19-Sep-01 22:21

What error number does the try and catch get for the open?

Michael Smile | :)

Stu20-Sep-01 6:03

20-Sep-01 6:03

After hr = pConn.CreateInstance(__uuidof(Connection));
the value of hr is -2147221008. I can't seem to get anything more from the _com_error object that is thrown except that the errormessage says "Invalid Pointer". I wonder if there could be something wrong with my compile options? Confused | :confused:

How can I scroll a CFormView?

Carlos Antollini20-Sep-01 6:18

Carlos Antollini

20-Sep-01 6:18

Did you use the CoInitialize()?

Cheers!!!

Carlos Antollini.

Craig Miller19-Sep-01 6:27

Craig Miller

19-Sep-01 6:27

Hi,

I have an SDI application that uses a CFormView. I have a third party graphics ActiveX control on the CFormView. I need to be able to scroll the CFormView because I want to make the ActiveX control bigger than the viewable area. Can someone help me with the steps to be able to scroll a CFormView?

Thanks for any help you can provide,

Craig

Tomasz Sowinski19-Sep-01 6:53

19-Sep-01 6:53

Use CScrollView::ScrollToPosition. CFormView is derived from CScrollView.

Tomasz Sowinski -- http://www.shooltz.com

Craig Miller19-Sep-01 7:04

Craig Miller

19-Sep-01 7:04

Tomasz, thanks for the response. I'm trying to rubberband the image and I have a callback function that get's this message. Once I get this message, I find out the size of the zoomed view, if it's bigger than the current client area I need to use the scrollbars. Currently, I can't figure out how to make the scroll bars show up. If I try CSrollView::ScrollToPosition it throws an exception because there aren't any scroll bars visible.

Do you know how I can make the scroll bars show up?

Thanks again,

Craig

Tomasz Sowinski19-Sep-01 7:15

19-Sep-01 7:15

Check CScrollView::SetScrollSizes.

Tomasz Sowinski -- http://www.shooltz.com

PostMessage... philosophy...

Craig Miller19-Sep-01 9:54

Craig Miller

19-Sep-01 9:54

That's excellent, thanks again for all your help.

Have a great day,

Craig

Remi Morin19-Sep-01 6:10

19-Sep-01 6:10

Hi, I have a Home-Made control who post a message. This control can be placed anywhere. All of this stuff run very well but something is not like I wan't it to be and it's the first time I use Message queuing

void MyHomeMadeControl::AMethod(void)
{
    
    PostMessage(GetParent(),
                (UINT)this,
                (long)&m_Var);

}

class CBoopView : public CView
{
//some stuff
MyHomeMadeControl m_Ctrl_1;
MyHomeMadeControl m_Ctrl_2;

//everything else
}

void CBoopView::OnZoomScroll(MyHomeMadeControl* WParam,MyHomeMadeParam* lParam)
{
    if(&m_Ctrl_1 == WParam)
    {
        //Here I know it's m_Ctrl_1
    }
    else
    {
        //Here m_Ctrl_2...
    }
}

I don't think it's a very good way to do so...
It is possible in my PostMessage to do something like

PostMessage(GetParent(),
            GetCurrentId(), //this return the Id of my CWnd (you know the UINT nID of the create function)
            (long)&m_Var);

so that way I will used Id number instead of pointers...

thanks

(by the way if there is a "standart way to identify the Object who Post the message tell me)

Remi Morin
Rmorin@Operamail.com
Remi.Morin@Lyrtech.com

Tomasz Sowinski19-Sep-01 7:05

19-Sep-01 7:05

Wrong, wrong, wrong. You're trying to use a parent window pointer as message identifier. This will not work.

#define WM_MY_MESSAGE (WM_USER + 1)
...
GetParent()->PostMessage(WM_MY_MESSAGE, someWparam, someLparam);

You can pass object pointer as wParam or lParam, as long as window that's going to process the message is in the same process. In your case it's true. There's another caveat: PostMessage places message in the queue. Receiving window will not get this message immediately - and depending on application, the object that you passed as message parameter may no longer exist. In such case, use SendMessage instead of PostMessage.

One final note: when you are using your controls only within this program, you may establish communication between windows without messages. Just cast the pointer returned by GetParent() to correct type and call whatever method you need:

// inside YourHomeMadeControl
CBoopView *pView = (CBoopView*)GetParent();
pView->Foo(param1, param2, param3);

Tomasz Sowinski -- http://www.shooltz.com

Remi Morin19-Sep-01 7:44

19-Sep-01 7:44

Some difficulties to understand...
this is a sumary of my .h file

class MyHomeMadeControl :public CWnd
{
// Construction
public:
   MyHomeMadeControl ();
// Overrides
   // ClassWizard generated virtual function overrides
   //{{AFX_VIRTUAL(MyHomeMadeControl )
	private:
   virtual BOOL Create(const RECT& rect, CWnd* pParentWnd, UINT nID, CCreateContext* pContext = NULL);
	//}}AFX_VIRTUAL

// Implementation
public:
   virtual  ~MyHomeMadeControl ();
 // Generated message map functions
protected:
   //{{AFX_MSG(MyHomeMadeControl )
   afx_msg  void OnPaint();
   afx_msg void OnTimer(UINT nIDEvent);
   //}}AFX_MSG
   DECLARE_MESSAGE_MAP()
};
static UINT WM_ON_TIMER_HOMEMADE= RegisterWindowMessage("MyHomeMadeControl_OnTimer");

and then the function on timer in the cpp file:

void CGraphScroll::OnTimer(UINT nIDEvent)
{
//here to ba able to import this code anywhere I have to do something like this
GetParent()->PostMessage(WM_ON_TIMER_HOMEMADE,(UINT)this,something);

/*this will require a #include "parent.h" witch I don't know
((CBoopView)GetParent())->OnTimer(Anything I want)
*/
}

So in a boopView (who can be a any kind of CWnd derived class) I have to trap this message, and I can have 0 to n instance of MyHomeMadeControl.

So for catch the message what I did work, but it's very strange... for a CButton It work very well and it's done like this

ON_BN_CLICKED(IDC_BUTTONX, OnButtonX)

ON_BN_CLICKED is a macro and it will be replace by

ON_CONTROL(BN_CLICKED, IDC_BUTTONX, OnButtonX)

it's exactly what I wan't to re-create with my Home made control, no matter how many of them exist, any of them will find whitch handler to use...

ON_CONTROL(WM_ON_TIMER_HOMEMADE,IDC_MYHOME_MADE_CONTROL_1,OnTimerControl_1)
ON_CONTROL(WM_ON_TIMER_HOMEMADE,IDC_MYHOME_MADE_CONTROL_2,OnTimerControl_2)

this doesn't work...

Remi Morin
Rmorin@Operamail.com
Remi.Morin@Lyrtech.com

Tomasz Sowinski19-Sep-01 8:09

19-Sep-01 8:09

So your control is designed to be a child of any parent and you want to use ON_CONTROL? It's easy: just remember that you need to call SendMessage rather than PostMessage (there's no need to use a queue). Control notifies its parent by sending one of two messages: WM_COMMAND or WM_NOTIFY.

In 16-bit Windows there was only WM_COMMAND, that's why edit, listbox, button and other 'old' controls use this method. OTOH, common controls that made their debut in 32-bit Windows, like listview, treeview, toolbar etc. use WM_NOTIFY. I'd suggest to use WM_NOTIFY as a method of communitaction between the control and any parent window. Use the following code to notify the parent about some event. Note the NM_SOMEEVENT - this is just a unsigned integer number that your parent needs to know. There's no need to use RegisterMessage in this scenario.

NMHDR hdr = { m_hWnd, ::GetWindowLong(m_hWnd, GWL_ID), NM_SOMEEVENT };
GetParent()->SendMessage(WM_NOTIFY, hdr.idFrom, (LPARAM)&hdr);

Parent will get WM_NOTIFY. MFC magic routes this message through message map. Use ON_NOTIFY to insert the handler into msgmap of parent window:

ON_NOTIFY(NM_SOMEEVENT, IDC_MYHOME_MADE_CONTROL_1, OnSomeEvent)

More details in MSDN, just search for WM_NOTIFY and ON_NOTIFY.

Tomasz Sowinski -- http://www.shooltz.com

Remi Morin19-Sep-01 9:02

19-Sep-01 9:02

thanks, it work very well Smile | :)

So it's the way to do that
but question, this structure take all my parameters so in my method (OnSomeEvent in you'r example) I have to call a method like

m_cMyHomeMadeControl.GetCurrentValues(all parameters I wan't)

it's a good way (the parent have to know what is his child)

Remi Morin
Rmorin@Operamail.com
Remi.Morin@Lyrtech.com

Tomasz Sowinski19-Sep-01 9:15

19-Sep-01 9:15

Calling child directly is one possibility. However, you could also easily add your own information. Just derive some struct from NMHDR:

struct MyNotifyInfo : public NMHDR
{
int yourMember1;
char yourMember2[100];
};

You could also create struct with NMHDR as first member:

struct MyNotifyInfo
{
NMHDR nmhdr;
int yourMember1;
char yourMember2[100];
};

The second method is used by Windows SDK - these header files must be compilable even in plain old C which doesn't support inheritance. Have a look at MSDN docs for NMTREEVIEW, NMLISTVIEW or any struct named NMxxxx.

In the parent's handler, just cast NMHDR* to MyNotifyInfo* and you'll be OK.

Tomasz Sowinski -- http://www.shooltz.com

Remi Morin19-Sep-01 9:57

19-Sep-01 9:57

last question...
NMHDR hdr = { m_hWnd, ::GetWindowLong(m_hWnd, GWL_ID), NM_SOMEEVENT };
NM_SOMEEVENT - There's no need to use RegisterMessage in this scenario...

I can use any value?? 0 to maximum unsigned int?
does it can be in conflict whit parent event? or (as I think) only whit MyHomeMadeControl event (in witch case it is easy to avoid)

...

thank you very much for you'r help, it's easy to do code whitout bother whit anything... but take care of everything in a windows program is very hard and good book are not easy to find. Thank you very much

Smile | :)

Remi Morin
Rmorin@Operamail.com
Remi.Morin@Lyrtech.com

Tomasz Sowinski19-Sep-01 10:20