C / C++ / MFC

act_x1-Apr-04 7:46

act_x

1-Apr-04 7:46

call Invalidate() or InvalidateRect

Antony M Kancidrowski1-Apr-04 7:53

Antony M Kancidrowski

1-Apr-04 7:53

The problem ns has is that dc2 has not been assigned to a device context.

You are right however that after drawing you need to invalidate. Smile | :)

Ant.

John R. Shaw1-Apr-04 8:52

John R. Shaw

1-Apr-04 8:52

You can get the DC at anytime by calling GetDC(). But unless you want the line to be overdrawn the next time the OnDraw() is called then you should just set a flag when the button is pushed and invalidate the area being drawn to.

// in OnDraw()
if( bFlag )
    // draw line

INTP

Ravi Bhavnani1-Apr-04 9:50

1-Apr-04 9:50

The right way to do this is to maintain a data structure that contains a collection of linked points. The data structure is updated in your button's handler. Your view's OnDraw() handler should paint itself (i.e. draw lines) based on the points in the data structure.

See the MFC "Scribble" demo app to see how this is done.

/ravi

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Re: Drawing DC--Thanks

ns5-Apr-04 3:43

5-Apr-04 3:43

Appreciate the help. Many thanks,
ns

What is UNUSED used for?

Jesse Evans1-Apr-04 7:32

Jesse Evans

1-Apr-04 7:32

I've been playing with a CString implementation I found here (Thanks, Joe!)[^] and it collides with another header I use. Compiling my app produces the following warning:
Warning C4065: switch statement contains 'default' but no 'case' labels and points to this section (and another like it) in Joe's StdString.h header:

inline void ssasn(std::wstring& sDst, const int nNull)<br />
{<br />
	UNUSED(nNull);<br />
	ASSERT(nNull==0);<br />
	sDst.assign(L"");<br />
}

I've found UNUSED defined in several ways, in a lot of headers. Here's how it looks in ...\VC98\MFC\Include\AFX.h:

#ifdef _DEBUG<br />
#define UNUSED(x)<br />
#else<br />
#define UNUSED(x) x<br />
#endif<br />
#define UNUSED_ALWAYS(x) x

but in a third-party header I need, it gets defined thus:

#ifndef UNUSED<br />
#ifdef _CVI_<br />
#define UNUSED(a)<br />
#else<br />
#define UNUSED(a) switch((int)&a){default:break;}   /* bypass bogus warnings on external compilers */<br />
#endif

It's this last definition that seems to be getting used in the compilation and generates the warning.
Any ideas what this is for? Can I remove the offending references to it without some weird side effect?

Thanks in advance for all your help.

'til next we type...
HAVE FUN!! -- Jesse

David Crow1-Apr-04 7:55

1-Apr-04 7:55

It's actually in place to squelch another compiler warning: C4101. A variable was declared, but never used. You can add a #pragma warning(disable:4507) statement if you don't like the C4065 warning.

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Jesse Evans1-Apr-04 8:25

Jesse Evans

1-Apr-04 8:25

Thanks, David!

I think you meant disable:4065, but that was enough to overcome my issue.

BTW, why is this sprinkled all over Microsoft's code? Shouldn't one simply remove the reference to the unused variable?

Long Live CodeProject!

'til next we type...
HAVE FUN!! -- Jesse

grigsoft1-Apr-04 8:36

grigsoft

1-Apr-04 8:36

> Shouldn't one simply remove the
> reference to the unused variable?

It depends. Consider this:

void myfunc1(LPVOID p)<br />
{<br />
  ASSERT(p);<br />
  // do smth without p<br />
  // may be later we will use it<br />
}<br />

It's a bit non-natural, but it give you an idea - item can be used in one configuration, but unused in another.
Or maybe this one is better:

void myfunc2(LPVOID p)<br />
{<br />
#ifdef _UNICODE<br />
  // do smth with p<br />
#else<br />
 UNUSED_ALWAYS(p);<br />
 // do smth without p<br />
#endif<br />
}

Igor Green
http://www.grigsoft.com/ - files and folders comparison tools

David Crow1-Apr-04 8:39

1-Apr-04 8:39

Jesse Evans wrote:
I think you meant disable:4065, but that was enough to overcome my issue.

You're right. Blush | :O

How I got C4507 is anyone's guess.

Jesse Evans wrote:
BTW, why is this sprinkled all over Microsoft's code? Shouldn't one simply remove the reference to the unused variable?

I'm not sure. Have a look at the USES_CONVERSION preprocessor directive. It will declare a variable and then use that variable all by itself in a statement just to keep the compiler from complaining about an unreferenced variable.

There's also the case of unreferenced function parameters. With C++, you can declare a function and omit the names of any unused parameters. With C that was not possible, so inside of the function, you could use the UNUSED() macro to get ride of the C4101 warning. Make sense?

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Monitoring a network directory

Jesse Evans1-Apr-04 8:51

Jesse Evans

1-Apr-04 8:51

Thanks, Igor and David. Makes sense, now.

'til next we type...
HAVE FUN!! -- Jesse

LKogut1-Apr-04 7:32

LKogut

1-Apr-04 7:32

Hi all,

I need to monitor the NT/2000/XP network environment for files that I have created and files that I have renamed.
I based my program on the FWATCH example of MSDN, i.e., I'm using ReadDirectoryChangesW and IO Completion Port to receive the notification.
The problem is that I also get notified when some other user (not me) creates or renames a file on the directory that I am monitoring.
Is there any way to filter the notifications so that I only get notified when I create or rename files? If not, is there any way to know which user caused the notification?
Thanks.

Re: Monitoring a network directory

David Crow1-Apr-04 8:50

Re: Monitoring a network directory

1-Apr-04 8:50

LKogut wrote:
Is there any way to filter the notifications so that I only get notified when I create or rename files? If not, is there any way to know which user caused the notification?

When a file is created, you can use GetNamedSecurityInfo() and LookupAccountSid() to see if the current owner of the file is you. Also, if renaming a file causes the owner to change, this will work too.

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

LKogut2-Apr-04 1:35

LKogut

2-Apr-04 1:35

Thanks David, this will help me for sure!
But, unfortunately, not 100%. Looking for the functions on the help, they only work on an NTFS file system. Any clue for non NTFS file system?

Resizing PropertyPages

act_x1-Apr-04 7:25

act_x

1-Apr-04 7:25

How do I resize my PropertySheet and all pages based on size of the Main Dialog ?

I derived a class from PropertySheet and tried to implement an OnInitDialog .
Here's what i tried but didnt come out good

BOOL CMainSheet::OnInitDialog() {<br />
 CPropertySheet::OnInitDialog();<br />
 CWnd *parentWnd = this->GetOwner();<br />
 ASSERT(parentWnd);<br />
  parentWnd->GetClientRect(&parentRect);<br />
 CTabCtrl *pTab = GetTabControl();<br />
 ASSERT(pTab);<br />
 this->SetWindowPos(0,parentRect.left,parentRect.top,200,200,0);<br />
 pTab->SetWindowPos(0,parentRect.left,parentRect.top,200,30,0);<br />
<br />
<br />
 CPropertyPage *page = GetActivePage();<br />
 ASSERT(page);<br />
 this->GetClientRect(&r);<br />
 page->SetWindowPos(0,r.left,r.top,180,180,0)<br />
 return TRUE ;<br />
}

Please advise

CArray on the heap

sschilachi1-Apr-04 6:17

sschilachi

1-Apr-04 6:17

Is there any way to create a CArray object on the heap rather than on the stack?

Thanks

Re: CArray on the heap

David Crow1-Apr-04 6:49

1-Apr-04 6:49

Yes, but why would you want to? As you add items to the array, memory is allocated from the heap to hold the individual items. The array object itself consumes very little memory.

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Re: CArray on the heap

Ravi Bhavnani1-Apr-04 7:08

Problem with strings conversion

1-Apr-04 7:08

My guess is he wants it to exist outside the scope of the creating block.

/ravi

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Re: CArray on the heap

Navin1-Apr-04 7:38

Navin

1-Apr-04 7:38

Simple:

CArray<int> *theArray = new CArray<int>;
// Examples of populating the array
theArray->Add(1);
theArray->Add(42);
theArray->SetAt(0, 1337);

Or am I missing something? Confused | :confused:

Remember, even if you win the rat race, you're still a rat.

doctorpi1-Apr-04 6:05

doctorpi

1-Apr-04 6:05

Hi guys
I've got this

CString file;
HANDLE hFile = CreateFile( ?????,........

What I have to put in ????? to get a valid value in hfile,all my tries have finished with a -1.
LPCSTR(file) doesn't work and I don't know what to do.
Thanks
Doc

Ravi Bhavnani1-Apr-04 6:33

1-Apr-04 6:33

See this[^] link.

/ravi

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doctorpi1-Apr-04 6:42

doctorpi

1-Apr-04 6:42

Already read,but sorry, I can't see the solution.
My question is, how can I convert a CString to the right parameter to the CreateFile method?
Thanks
Doc

Ravi Bhavnani1-Apr-04 6:49

1-Apr-04 6:49

CString strFile = _T("C:\\myfile.txt");
HANDLE hFile = CreateFile (strFile, GENERIC_WRITE, 0, NULL, CREATE_NEW, 0, NULL);

/ravi

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