C / C++ / MFC

Christian Graus22-Oct-01 13:57

22-Oct-01 13:57

Try getting rid of the (void*) cast (why ???), and dereference your variables. CTrackbarCtrl will almost certainly offer operator HWND, but CTrackbarCtrl* most certainly will not.

Christian

As I learn the innermost secrets of the around me, they reward me in many ways to keep quiet.

Men with pierced ears are better prepared for marriage. They've experienced pain and bought Jewellery.

Michael Dunn22-Oct-01 15:56

Michael Dunn

22-Oct-01 15:56

You're comparing an HWND with a C++ object pointer, which obviously aren't the same creatures. Do something like:

if ( (HWND)lParam == slider->m_hWnd )

--Mike--
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This posting is provided "as was" with no warranties, guarantees, lotteries, or any of those little bags of peanuts you get on planes. You assume all risk for crossing the street without holding mommy's hand. © 2001 Mike's Classy Software. Member FDIC. If rash develops, discontinue use.
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clintsinger22-Oct-01 17:02

clintsinger

22-Oct-01 17:02

Thanks, that did the trick.

Cheers,
Clint

Christian Graus22-Oct-01 18:19

22-Oct-01 18:19

Just for my own info, does that mean that dereferencing the slider * wouldn't result in a HWND ? I'm writing my own control classes at the moment and all have operator HWND defined, I'm surprised at the possibility that the M$ classes don't do the same thing ?

Christian

As I learn the innermost secrets of the around me, they reward me in many ways to keep quiet.

Men with pierced ears are better prepared for marriage. They've experienced pain and bought Jewellery.

clintsinger24-Oct-01 6:21

clintsinger

24-Oct-01 6:21

When we dereference the pointer all we get is the pointer to the object it self - not the m_hWnd that it contains. You could get the hWnd when you call the create function ie.

CTrackbarCtrl *tb;
HWND hwnd;

hwnd = tb->Create(...);

but that means you would have to carry around two variables when the hwnd is already being carried around in the class provided by WTL.

Cheers,
Clint Smile | :)

Christian Graus24-Oct-01 11:22

Re: undeclared identifier

24-Oct-01 11:22

So WTL doesn't offer operator HWND on these items, nor does it have a m_hWnd variable ? I find that highly unlikely.

I've just had a look at the WTL source, and they do indeed keep the HWND as a variable called m_hWnd, so that is what you need.

Christian

After all, there's nothing wrong with an elite as long as I'm allowed to be part of it!! - Mike Burston Oct 23, 2001

undeclared identifier

Peter Liddle22-Oct-01 12:21

Peter Liddle

22-Oct-01 12:21

Hey Guys
When i try and use this function

CertGetNameString()

i get a undeclared identifier message when i compile yet msdn says this is defined in wincrypt.h which i have included has anyone got any ideas

peter

Christian Graus22-Oct-01 12:43

Flicker-free drawing question

22-Oct-01 12:43

As this function requires Windows 98/ME, I'd say for sure to get access to it you'll need to install the Platform SDK.

Christian

As I learn the innermost secrets of the around me, they reward me in many ways to keep quiet.

Men with pierced ears are better prepared for marriage. They've experienced pain and bought Jewellery.

Synchronization objects

Not Active22-Oct-01 11:03

Not Active

22-Oct-01 11:03

A co-worker and I were having a discussion about what sync object to use for a particular case. The senerio is as follows:

Read an item from a list
Write data to a device, using a sperate thread
Wait for write to complete
Repeat until list is complete

He designed the above to use a semaphore where I pointed out that an event would be more appropriate in this case. His arguement was that there was no difference in the how the two were created, used, etc. He could not seem to handle the statement "why have two objects to do the same thing".

Could anyone comment on the overhead, resource usage, etc. of the two objects.

Chen Venkataraman22-Oct-01 10:00

Chen Venkataraman

22-Oct-01 10:00

I've a control that is used to update real-time stock quotes. The control uses the CMemDC class to draw to avoid the flickering but i still see the control flicker. Essentially, the drawing code looks like this (borrowed the technique from Chris' Grid control)

XYZControl::OnPaint()
{
    CPaintDC dc(this); // device context for painting
	
    if (m_bDoubleBuffer)    // Use a memory DC to remove flicker
    {
        CMemDC memDC(&dc);
        OnDraw(&memDC);
    }
    else                    // Draw raw - this helps in debugging vis problems.
        OnDraw(&dc);
}

XYZControl::OnDraw(CDC* pDC)
{
    // draw code
}

One interesting thing that i noticed while debugging was that the GetClipBox() call in MemDC contructor returns a empty rectangle. Suspecting this could mean trouble? Any thoughts on what should i check/verify? Confused | :confused:

Thanks

Chen Venkataraman

Tomasz Sowinski22-Oct-01 10:19

22-Oct-01 10:19

When double buffering is on, handle WM_ERASEBKGND and return FALSE.

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

Chen Venkataraman22-Oct-01 11:10

Chen Venkataraman

22-Oct-01 11:10

Shouldn't that be TRUE? Here's the snippet from MSDN for WM_ERASEBKGND :

<br />
An application should return nonzero in response to WM_ERASEBKGND if it processes the message and erases the background; this indicates that no further erasing is required. If the application returns zero, the window will remain marked for erasing. (Typically, this indicates that the fErase member of the PAINTSTRUCT structure will be TRUE.)<br />

Anyway, I've handled the WM_ERASEBKGND message & returned both FALSE & TRUE but it appears that it doesn't matter - the control still flickers.

Chen Venkataraman

Tomasz Sowinski22-Oct-01 11:27

22-Oct-01 11:27

Returning FALSE follows the MSDN docs - after all, you do not erase the background just by returning FALSE from the empty handler.

BTW: Use GetClipBox with a paint DC, not with a memory DC.

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

Christian Graus22-Oct-01 18:29

Writing a Client/Server in Visual C++

22-Oct-01 18:29

The way I always did this was to draw the control to a memory DC, THEN call CPaintDC, THEN draw the control. CPaintDC causes the area to be erased, although it is reasonable to suggest that overriding OnEraseBackground to not call the parent method would solve this also.

When you overrode WM_ERASEBACKGROUND, did you still call the base method ? If so, don't if you don't want the background erased.

Christian

As I learn the innermost secrets of the around me, they reward me in many ways to keep quiet.

Men with pierced ears are better prepared for marriage. They've experienced pain and bought Jewellery.

22-Oct-01 9:10

Hello,

As a part of the college lab work I have to write a client and a server using MFC. The prof explained the whole stuff briefly, and I recall him having talked about threads etc. The client/server have to use the UDP protocol and be able to transfer files (even big ones).

Can someone tell me how to do this? or where I can find relevant resources? I dont know how to analyse the problem.

Thanks,
Mike

Re: Writing a Client/Server in Visual C++

Matt Newman22-Oct-01 13:21

Matt Newman

22-Oct-01 13:21

http://www.codeproject.com/internet/multicastsocket.asp#xx4106xx Gives you a start on multicasting if that is the kind of thing you need. Also check out the Internet & Network section.

-Matt Newman
-Matt Newman

Hiding the main frame in mdi

jangel22-Oct-01 8:51

jangel

22-Oct-01 8:51

Hi, does anybody know how can I hide the main frame in a MDI app?? Tnx

Tomasz Sowinski22-Oct-01 8:55

22-Oct-01 8:55

ShowWindow(SW_HIDE) doesn't work?

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

jangel22-Oct-01 10:04

jangel

22-Oct-01 10:04

Nop

Tomasz Sowinski22-Oct-01 10:24

22-Oct-01 10:24

It works for me. Are you sure you're calling ShowWindow(SW_HIDE) for main frame?

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

jangel22-Oct-01 12:37

jangel

22-Oct-01 12:37

Sorry I think I made the wrong answer. It's there any way to hide the main frame, and show the child frame at the same time?

Christian Graus22-Oct-01 18:36