C / C++ / MFC Discussion Boards

Re: which design is better to wrap another class instance

CPallini12-Apr-08 2:33

12-Apr-08 2:33

It's simple: reference variable must alway be assigned. Hence you need to pass an object to the class,
that is, you're making a reference to an existing object.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

Re: which design is better to wrap another class instance

George_George12-Apr-08 3:46

George_George

12-Apr-08 3:46

Thanks for clarification for this. Smile | :)

regards,
George

Re: which design is better to wrap another class instance

Blake Miller14-Apr-08 5:56

Blake Miller

14-Apr-08 5:56

We have historically had so much trouble with 'lost' pointers, that we embed 'cookies' to our other objects within others, instead of the pointers themselves. If you have a pointer to an object, it is hard to tell if the object is still around, unless you have the address of a smart pointer that won't let object delete until all references to the object are gone. If you use cookies, you can ask a lookup table to translate cookie for you, and if that is gone, then object is gone too.

Re: which design is better to wrap another class instance

George_George14-Apr-08 22:41

George_George

14-Apr-08 22:41

Thanks Blake,

I am interested to learn what do you mean embed 'cookies'. Do you show some pesudo code or refer some links please? Smile | :)

regards,
George

Re: which design is better to wrap another class instance

Blake Miller15-Apr-08 7:03

Blake Miller

15-Apr-08 7:03

Suppose I have a list of instances of objects of type "Class A".
Now I want to refer to those Class A objects by specific instance from another class, let's say Class B.

Traditionally, you would have placed a pointer or some reference to the Class A instance within Class B:

class B<br />
{<br />
   ...<br />
   class A* m_pA;<br />
   ...<br />
};

But instead, if you give every instance of class A a 'cookie', such as a unique 32-bit DWORD value:

class A{<br />
   ...<br />
   DWORD m_Cookie;<br />
   ...<br />
};

And then you palce all the instances of Class A into a map, mapping the cookie to the pointer to Class A (So now the pointer to class A is in exactly one place).

Then when you need class B to refer to a specific instance of Class A, instead of using the pointer to Class A, you store its cookie value:

class B
{
...
DWORD m_CookieToA;
...
};

Then when you need to get to a Class A instance from a member function of Class B, you can use the map to look for the cookie for the related Class A. If the map gives you back a value, then you get back a good pointer to class A, and if not, then there is no Class A with that cookie in existence.

If the lifetime of Class A objects will outlive Class B objects, this is fine either way - pointer or cookie.

Otherwise, you might want to provide some synchronization on the map (unless your program is single threaded) so things are not removed from the Class A map while a Class B member function retains or is using a pointer to a Class A object. Otherwise, you are free to delete Class A objects at will, without trying to patch up your Class B objects which might have stored pointers to the Class A instances.

So, you can ask yourself, if it is more important not to crash or to have performance, as the other member mentioned. This technique is not as 'quick' as storing the pointer to Class A within Class B, as far as the quickest reference to Class A from within a Class B member function (you have to look up the cookie in the map each time to fetch the temporary pointer to Class A).

If you wanted to get fancy, you could use a multimap for Class A, and map Class A address, Class A cookie, and the number of references to class A in the map. The reference count would be udpated each time you assigned a cookie to an A to a B. That way, you would know, as yuo were about to delete a Class A instance, if there were any outstanding Class B referring to it.

Re: which design is better to wrap another class instance

George_George16-Apr-08 0:52

George_George

16-Apr-08 0:52

Cool, Blake!

Your answer is clear. Smile | :)

regards,
George

re-entrancy pattern issue setbacks

George_George11-Apr-08 22:24

George_George

11-Apr-08 22:24

Hello everyone,

Two questions about re-entrancy issue,

http://www.codeproject.com/KB/COM/sta_issues.aspx

1. What is the setback of the issue? I think it is still thread-safe since only one STA owning thread will execute on STA component;

2. How to avoid it in design?

thanks in advance,
George

How can remove button of Property Sheet?

Le@rner11-Apr-08 21:44

Le@rner

11-Apr-08 21:44

Hi all,

i m create a property sheet and show property pages in this property sheet.
When i run the application the Property Sheet Show Three Buttons "OK","CANCEL",and "APPLY" at the bottom .and the apply button is Disabled.

How can Remove all these buttons from Property Sheet.

this is my Code::

class CMyPropertySheet : public CPropertySheet
{
DECLARE_DYNAMIC(CMyPropertySheet)

public:
CMyPropertySheet(LPCTSTR pszCaption, CWnd* pParentWnd = NULL, UINT iSelectPage = 0);
virtual ~CMyPropertySheet();
static int CALLBACK XmnPropSheetCallback(HWND hWnd, UINT message, LPARAM lParam);

DECLARE_MESSAGE_MAP()
public:
virtual BOOL OnInitDialog();
HICON m_hIcon;

CPropertyPage1 m_Page1;
CPropertyPage2 m_Page2;
CPropertyPage3 m_Page3;
CPropertyPage4 m_Page4;
CPropertyPage5 m_Page5;

protected:
BOOL m_bNeedInit;
CRect m_rCrt;
int m_nMinCX;
int m_nMinCY;

public:
afx_msg void OnSize(UINT nType, int cx, int cy);
afx_msg void OnGetMinMaxInfo(MINMAXINFO* lpMMI);
virtual INT_PTR DoModal();
//////////////////////////////////////////////////////////////////////
CMyPropertySheet::CMyPropertySheet(LPCTSTR pszCaption, CWnd* pParentWnd, UINT iSelectPage)
:CPropertySheet(pszCaption, pParentWnd, iSelectPage)
, m_bNeedInit(TRUE)
, m_nMinCX(0)
, m_nMinCY(0)
{
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
AddPage(&m_Page1);
AddPage(&m_Page2);
AddPage(&m_Page3);
AddPage(&m_Page4);
AddPage(&m_Page5);

}

CMyPropertySheet::~CMyPropertySheet()
{
}

BEGIN_MESSAGE_MAP(CMyPropertySheet, CPropertySheet)
ON_WM_SIZE()
ON_WM_GETMINMAXINFO()
ON_WM_CLOSE()
END_MESSAGE_MAP()

// CMyPropertySheet message handlers

BOOL CMyPropertySheet::OnInitDialog()
{
this->SetIcon(m_hIcon,TRUE);

BOOL bResult = CPropertySheet::OnInitDialog();

// Adjust property sheet size to account for the new menu.
CRect r; GetWindowRect(&r);
r.bottom += GetSystemMetrics(SM_CYMENU);
MoveWindow(r);

// ...
// Init m_nMinCX/Y
m_nMinCX = r.Width();
m_nMinCY = r.Height();
// After this point, the resize code runs.
m_bNeedInit = FALSE;
GetClientRect(&m_rCrt);

return bResult;
}
// This function must be a STATIC method.
// Callback to allow you to set the default window styles
// for the property sheet.
int CALLBACK CMyPropertySheet::XmnPropSheetCallback(HWND hWnd, UINT message, LPARAM lParam)
{
extern int CALLBACK AfxPropSheetCallback(HWND, UINT message, LPARAM lParam);
// XMN: Call MFC's callback.
int nRes = AfxPropSheetCallback(hWnd, message, lParam);

switch (message)
{
case PSCB_PRECREATE:
// Set your own window styles.
((LPDLGTEMPLATE)lParam)->style |= (DS_3DLOOK | DS_SETFONT
| WS_OVERLAPPEDWINDOW | WS_POPUP | WS_VISIBLE | WS_CAPTION);
break;
}
return nRes;
}
void CMyPropertySheet::OnSize(UINT nType, int cx, int cy)
{
CPropertySheet::OnSize(nType, cx, cy);
CRect r1;

if (m_bNeedInit)
return;

CTabCtrl *pTab = GetTabControl();
ASSERT(NULL != pTab && IsWindow(pTab->m_hWnd));

int dx = cx - m_rCrt.Width();
int dy = cy - m_rCrt.Height();
GetClientRect(&m_rCrt);

HDWP hDWP = ::BeginDeferWindowPos(5);

pTab->GetClientRect(&r1);
r1.right += dx; r1.bottom += dy;
::DeferWindowPos(hDWP, pTab->m_hWnd, NULL,
0, 0, r1.Width(), r1.Height(),
SWP_NOACTIVATE|SWP_NOMOVE|SWP_NOZORDER);

// Move all of the buttons with the lower and right sides.
for (CWnd *pChild = GetWindow(GW_CHILD);
pChild != NULL;
pChild = pChild->GetWindow(GW_HWNDNEXT))

{

if (pChild->SendMessage(WM_GETDLGCODE) & DLGC_BUTTON)
{
pChild->GetWindowRect(&r1); ScreenToClient(&r1);
r1.top += dy; r1.bottom += dy; r1.left+= dx; r1.right += dx;
::DeferWindowPos(hDWP, pChild->m_hWnd, NULL,
r1.left, r1.top, 0, 0,
SWP_NOACTIVATE|SWP_NOSIZE|SWP_NOZORDER);
}
// Resize everything else.
else
{
pChild->GetClientRect(&r1);
r1.right += dx; r1.bottom += dy;
::DeferWindowPos(hDWP, pChild->m_hWnd, NULL, 0, 0,
r1.Width(), r1.Height(),
SWP_NOACTIVATE|SWP_NOMOVE|SWP_NOZORDER);
}

}

::EndDeferWindowPos(hDWP);

}

void CMyPropertySheet::OnGetMinMaxInfo(MINMAXINFO* lpMMI)
{
lpMMI->ptMinTrackSize.x = m_nMinCX;
lpMMI->ptMinTrackSize.y = m_nMinCY;

CPropertySheet::OnGetMinMaxInfo(lpMMI);
}

INT_PTR CMyPropertySheet::DoModal()
{
// Hook into property sheet creation code
m_psh.dwFlags |= PSH_USECALLBACK;
m_psh.pfnCallback = XmnPropSheetCallback;

return CPropertySheet::DoModal();
}

Thanks in advance.

Re: How can remove button of Property Sheet?

Blake Miller14-Apr-08 5:58

Blake Miller

14-Apr-08 5:58

Get window handles of each of the buttons and hide and disable the buttons. Make sure the focus is not on them when doing so. Also, if you have other buttons, you might want to make one of them the defualt button.

call one dialog box from another in sdk

Pankaj Kothawade11-Apr-08 21:00

Pankaj Kothawade

11-Apr-08 21:00

hi all,
i want to create a dialog box same like as we click on Start button of Windows Explorer.
i want to set a focus on one button like (Start Button) at bottom,
from that button i want to call a dialog box on which my child window controls are present.
i am using a dialog box for that bottom button, after click on that button i want to set focus on the another dialog box

plz help me out from dis..

Pankaj

Re: call one dialog box from another in sdk

Hamid Taebi12-Apr-08 7:19

Hamid Taebi

12-Apr-08 7:19

I think I saw an article I think it was nearly your answer but I dont know I saw it on the codeproject or other place.

Menu On RButtonDown of Mouse.

Le@rner11-Apr-08 20:39

Le@rner

11-Apr-08 20:39

Hi all,

i m using this code for creating a menu on Right Button Down of Mouse.

HMENU hMenu = ::CreatePopupMenu();
if (NULL != hMenu)
{
// add a few test items
::AppendMenu(hMenu, MF_STRING, 1, "Item 1");
::AppendMenu(hMenu, MF_STRING, 2, "Item 2");
::AppendMenu(hMenu, MF_STRING, 3, "Item 3");

ClientToScreen(&point);

int sel = ::TrackPopupMenuEx(hMenu,
TPM_CENTERALIGN | TPM_RETURNCMD,
point.x,
point.y,
m_hWnd,
NULL);
::DestroyMenu(hMenu);

it works but i dot no how can take action on its items.

Anyone can help me about this.

Thanks in advance.

Re: Menu On RButtonDown of Mouse.

enhzflep12-Apr-08 7:14

enhzflep

12-Apr-08 7:14

Yeah, sure. The 1, 2 & 3 (3rd parameter) are used as the commandIDs.
When a particular menu option is chosen, this commandID will be sent to your windowProcedure in LOWORD of wParam.

So, what you need to do with the above code is look for 1, 2 or 3 as being the ID of the control that generated a WM_COMMAND message. An rough example may be seen in this code I just ripped out of a class, just pay attention to the way the messages are created and caught.

LRESULT WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
     switch (uMsg)
     {
            case WM_COMMAND:
                 switch LOWORD(wParam)
                 {
                        case <code>IDM_LargeIcons</code>:
                             SetIconStyle(LARGE);
                             break;
                        case <code>IDM_SmallIcons</code>:
                             SetIconStyle(SMALL);
                             break;
                        case <code>IDM_Details</code>:
                             SetIconStyle(DETAIL);
                             break;
                        case <code>IDM_List</code>:
                             SetIconStyle(LIST);
                             break;
                     }
                     break;

                case WM_RBUTTONDOWN:

                     POINT CurPos;
                     GetCursorPos(&CurPos);
		     HMENU hPopupMenu = CreatePopupMenu();

		     //Add pop-up menu to allow user to choose between Icon, LargeIcon, List & Details views
                     InsertMenu(hPopupMenu, 0, MF_BYPOSITION | MF_STRING, <code>IDM_LargeIcons</code>, "Large Icons");
		     InsertMenu(hPopupMenu, 1, MF_BYPOSITION | MF_STRING, <code>IDM_SmallIcons</code>, "Small Icons");
		     InsertMenu(hPopupMenu, 2, MF_BYPOSITION | MF_STRING, <code>IDM_List</code>, "List");
		     InsertMenu(hPopupMenu, 3, MF_BYPOSITION | MF_STRING, <code>IDM_Details</code>, "Details");
		     SetForegroundWindow(GetHwnd());
		     TrackPopupMenu(hPopupMenu, TPM_TOPALIGN | TPM_LEFTALIGN, CurPos.x, CurPos.y, 0, GetHwnd(), NULL);//m_hWndParent, NULL);
		     DestroyMenu(hPopupMenu);
                     return 0;
		 }
		// Always pass unhandled messages on to WndProcDefault
		return WndProcDefault(hWnd, uMsg, wParam, lParam);
	}

The easiest way to make the world a better place is to refuse to help those that wreck it....

Re: Menu On RButtonDown of Mouse.

Hamid Taebi12-Apr-08 7:19

Hamid Taebi

12-Apr-08 7:19

Can you use of context menu,did you declare functions for these id menus.

files present in folder

neha.agarwal2711-Apr-08 19:41

neha.agarwal27

11-Apr-08 19:41

Hi all,

I want to find files which are present in a particular folder.

how can i do it???

Thanks in advance

Re: files present in folder

CPallini11-Apr-08 21:34

CPallini

11-Apr-08 21:34

You may use FindFirstFile and FindNextFile functions, see [^].
Smile | :)

Unlock Process

john563211-Apr-08 17:58

john5632

11-Apr-08 17:58

Hi Experts,

If a process is locked by another process how can I unlock it?

Re: Unlock Process

Schehaider_Aymen11-Apr-08 23:11

Schehaider_Aymen

11-Apr-08 23:11

Hi,

If u are looking for some softs there is Unlocker, u can donload it on http://ccollomb.free.fr/unlocker/unlocker1.8.6.exe[^]

Or if u can exec the command "taskkill /F /Num PID" but u need to enter the appropriate PID Of the process. I don't know how u can get the PID of the process Sigh | :sigh:

but may be if u look more under the Dos commands u will find it.

"The Ultimate Limit Is Only Your Imagination."

MIME Spec

Bram van Kampen11-Apr-08 11:46

Bram van Kampen

11-Apr-08 11:46

Hi,

I am writing an automatic email sending/receiving module. I'm not using MFC for this. It's actually remarkably simple without MFC. Now I want to send along Attachments. The MIME Spec is in Text Form (as in Notepad) and does not facilitate searches.

I've been scouring the MIME specs for an indication as to how to designate data held in a buffer to be sent as an attachment to an email. (i.e.: MIME Header Entries to Name the Data as a File on the Client Side, and Info to identify the Buffer).

Anyone there swith some knowledge about this.

Kind Regards

Bram van Kampen

Prevent active controls under child window to overwhelm it

428811-Apr-08 8:02

4288

11-Apr-08 8:02

Hi guys,

I have a problem: two child windows inside a parent, one normal, one with wndTopMost set

When I pass the mouse over the normal child's controls, they overwhelm the wndTopMost child and cause bad-redrawing

-> This screenshot better explains the problem:
http://img257.imageshack.us/img257/7740/topmostprobss0.jpg

Can you please help me solving the problem?

---

Re: Prevent active controls under child window to overwhelm it

Mark Salsbery11-Apr-08 8:20

Mark Salsbery

11-Apr-08 8:20

What if you use the WS_CLIPSIBLINGS style on the windows?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Prevent active controls under child window to overwhelm it

428811-Apr-08 9:22

4288

11-Apr-08 9:22

Hi Mark, thank you very much

Using WS_CLIPSIBLINGS on the child window that should be topmost places it behind all child windows

That could be a solution also if it isn't what I was looking for

---

Re: Prevent active controls under child window to overwhelm it

Moak12-Apr-08 1:34

Moak

12-Apr-08 1:34

I don't understand the design of your dialog. You have controls overlapping... maybe something is missing in your example screenshot?

My Webchat

Re: Prevent active controls under child window to overwhelm it

Mark Salsbery12-Apr-08 4:41

Mark Salsbery

12-Apr-08 4:41

I agree with Moak - I don't understand the design. You're pretty much getting the behavior you
ask for there. Smile | :)

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Prevent active controls under child window to overwhelm it

428812-Apr-08 10:47

4288

12-Apr-08 10:47

Uhm, how about creating a child window that act like a split window?

Could it be a solution?

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