C / C++ / MFC Discussion Boards

Michael Dunn7-Feb-04 16:02

7-Feb-04 16:02

Anyone have any idea why? Any help is appreciated.

Because that's how WM_MOUSEMOVE works - it's send to the window under the cursor when the mouse is not captured. As Ravi said, you have to capture the mouse to get notified regardless of where the cursor is. You can't do that all the time though, as capturing the mouse means that no other windows will get mouse messages.

--Mike--
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Why does this fail?

Anonymous6-Feb-04 11:40

Anonymous

6-Feb-04 11:40

BYTE ks[256];
GetKeyboardState(ks);
WORD w;
UINT scan;
scan=0;
ToAscii(wParam,scan,ks,&w,0);
ch =char(w);
MessageBox(0,"" + ch,"Key pressed",MB_OK); // <-- is this the right way of getting the char into a string? The results are jumbled

Re: Why does this fail?

Anonymous7-Feb-04 3:11

Anonymous

7-Feb-04 3:11

please buy a book about C++ and windows programming

Re: Why does this fail?

John M. Drescher7-Feb-04 19:23

John M. Drescher

7-Feb-04 19:23

Anonymous wrote:
windows programming

This really is not windows programming (except for the MessageBox). I mean a windows programmer will never do this (reading keyboard codes...). Windows programming is event driven. The proper way to handle the keyboard is through events and accelerators that fire events (i.e. assign ALT-A to send the ID_USER_COMMAND command message)

John

Closing an application

krugger6-Feb-04 11:37

krugger

6-Feb-04 11:37

Hi all;

I am creating an application which will have a login dialog. In the dialog, i have a "close" button which is supposed to close the WHOLE application. Can somebody please help me in getting this done.

Thanks

Nb. Could you please help me to understand have i can gray out menu's and toolbars prior to login on the application

Visual Beginner

Re: Closing an application

Ravi Bhavnani6-Feb-04 13:02

Ravi Bhavnani

6-Feb-04 13:02

In the handler for your dialog's "Close" button, do the following:

AfxGetMainWnd()->PostMessage (WM_CLOSE);
CDialog::OnOK();

This should cause the dialog to close and the app to properly exit.

Your app's menu items can be (selectively) grayed out (i.e. disabled) by implementing UI update handlers for them. You can write a single handler that enables the menu item only if the login phase has successfully completed.

/ravi

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Re: Closing an application

Jim Crafton6-Feb-04 13:05

Jim Crafton

6-Feb-04 13:05

class MyWinApp : public CWinApp {
//rest of code
  virtual BOOL InitInstance();
}


BOOL MyWinApp::InitInstance()
{
  //boiler plate code for CWinApp initialization goes here

  MyLoginDialog dlg;
  if ( IDOK == dlg.DoModal() ) {
    //do rest of app
  }
  else {
    return FALSE;
  }
  return TRUE;
}

this might be one way ot handle it

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Serial implementation deadlock problem

rmnowick6-Feb-04 11:25

rmnowick

6-Feb-04 11:25

All,
I posted a description of this problem on the following board, which the source code was available from:

http://www.codeproject.com/system/serial.asp

Because there is so much more activity on this board I thought I would also post a link to it here. Anyone familiar with the CSerialWnd class might be able to offer me some advice.

Thanks,
Robert

Help converting a demo project?

DanYELL6-Feb-04 11:09

DanYELL

6-Feb-04 11:09

This article here:

http://www.codeproject.com/dialog/scrollablechilddialog.asp

is really cool, but it's for a CDialog. I am trying to
re-write it for a CFormView. The section of code here:

CRect rc;
GetDlgItem(IDC_PLACEHOLDER)->GetWindowRect(rc);
ScreenToClient(&rc);
m_pdlgScroll->MoveWindow(rc);

I have a CFormView with the resource IDD_FORM1. How
can I rewrite this section of code properly? I can't
have:

GetDlgItem(IDD_FORM1)->GetWindowRect(rc);

?????

WINHTTP

Jack Reed6-Feb-04 10:53

Jack Reed

6-Feb-04 10:53

I have been working on a project that retrieves various credit reports from the 3 credit bureaus. I have been trying to retrieve the certificate that I am getting back when connecting to the bureau so that I may verify the certificate. All the examples I have found in the Microsoft documentation show me how to retrieve the info from my local machine but not from the server.

I found information on winhttp and downloaded the latest Platform SDK to utilize it. I created a class to use winhttp to get the certificate back and verify it. The class compiles fine, but when I compile the complete application I get LNK2001 ConvertStringToBSTR errors. When I uninstall the SDK I can compile the application again without using the new class.

I am using Visual Studio .NET (not 2003).

Might anyone know how to get around this or a way I can accomplish the same thing without using winhttp?

Re: WINHTTP

Gerald Schwab6-Feb-04 11:18

Gerald Schwab

6-Feb-04 11:18

My guess is that you need to link with comsupp.lib.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclang/html/vclrfconvertstringtobstr.asp[^]

Re: WINHTTP

Jack Reed6-Feb-04 11:33

Jack Reed

6-Feb-04 11:33

I saw comsupp.lib as well, but I still get the same LNK errors linking with comsupp.lib.

I guess I will keep looking for alternatives. Thank you for your input.

Callback function within a class

Cael6-Feb-04 9:58

Cael

6-Feb-04 9:58

I’m Visual C++ newbie trying to make a Win-32 class that create a hover button (without MFC).

I trying to use the mellertson's article "How to use SetTimer() with callback to a non-static member function" to substitute button’s WNDPROC, so it can process it's own WM_MOUSEOVER, WM_MOUSEHOVER, WM_MOUSELEAVE messages.

I use all the technique shown in the article, and work fine, but only with one control. If I create two o more controls, pObject always refers to the last control created.

Anybody knows how to call a callback function within it's own class?

Please help me.

Confused | :confused:

Re: Callback function within a class

Antti Keskinen6-Feb-04 11:12

Antti Keskinen

6-Feb-04 11:12

The most easiest approach to this problem is not by following Mellertson's article.

Like you stated, you are creating a class that manages a custom button control. What you are doing, infact, is much similar to MFC: a wrapper class for a Win32 API routine. MFC, although, implements everything based on the window-thinking: every control is derived from CWnd.

Instead of using Mellertson's article, consider the following approach:
1. In your program, create a new instance of the class. When this instance is created, all member functions and variables of the class become valid.
2. Call a 'second-phase' constructor that creates the actual Windows button control. As all member functions are properly initialized in step 1, you can refer to a non-static member function to handle the WNDPROC's job.

This approach allows each instance of the button class to function independently, ESPECIALLY if you use dynamic creation of the objects. Just remember that the clean-up work must be implemented very carefully to avoid memory leaks.

In the 'second-phase' constructor, you can use the Win32 API routines to create the button control, and the returned HWND to replace the window procedure function.

-Antti Keskinen

----------------------------------------------
The definition of impossible is strictly dependant
on what we think is possible.

Re: Callback function within a class

Cael6-Feb-04 13:20

Cael

6-Feb-04 13:20

Let's see, I understand two different things:

1. I create a class A, with my non-static callback function (WndProc) and other members. Then I made class B derived from A, in which I create the button and refer to ::WndProc as my new callback function. Or,

2. I create a class A with two constructors. The first one initializes my WndProc and other members. The second one create the button and replace the window procedure function to WndProc.

Which way I should take?

I still confuse Confused | :confused:

Re: Callback function within a class

Antti Keskinen8-Feb-04 9:59

Antti Keskinen

8-Feb-04 9:59

The option number two is correct.

However, I wouldn't recommend replacing the original window procedure. Instead, register a new window class, call it "MyButton", for example. Implement a handler for WM_PAINT, then use DrawEdge SDK function to draw the button edges and place the text on the button. This allows a much greater degree of control on how the button looks and behaves.

I suggest this method mainly because if you replace the original procedure, you must restore it as well when a WM_DESTROY message comes, otherwise the button control might not get freed properly, thus resulting a memory leak.

Here is an article I found while surfing the web. It gives you a basic idea on how to implement an MFC-style window class wrapper. Basically, it has a window procedure method as a non-static function, then it has a static message router function, which is passed to the window class registration. The router, on the other hand, is able to get the correct instance of the class from the passed variables (WPARAM and LPARAM) and then call the appropriate message handler. This behaviour is required if you create multiple objects from the same class.

The article itself can be found here[^].

-Antti Keskinen

----------------------------------------------
The definition of impossible is strictly dependant
on what we think is possible.

Re: Callback function within a class

Cael8-Feb-04 16:32

Cael

8-Feb-04 16:32

Oh man it's too much for me, but I'll try it.

Thanks a lot! Big Grin | :-D

Help with MFC forms

iboux6-Feb-04 9:52

iboux

6-Feb-04 9:52

I'm new to MFC and I created a SDI application. Now I added a new form and the based class is CFromView. Everytime I compile the project, I get a little pop-up window which is asking me to choose which form to load. How can I set one of the form as a default and I would like to add a button on the main to call the second form. Like we do in VB.
Thanks...
Cry | :((

Re: Help with MFC forms

David Crow6-Feb-04 10:52

David Crow

6-Feb-04 10:52

iboux wrote:
Everytime I compile the project, I get a little pop-up window which is asking me to choose which form to load.

The compiler is asking you this, or your application?

A rich person is not the one who has the most, but the one that needs the least.

Use CreateThread or _beginthreadex?

xatanu6-Feb-04 9:41

xatanu

6-Feb-04 9:41

Hi,

I'm creating a program that uses threads. The question is should I use the WinAPI CreateThread or the CRT _beginthreadex?
I know the MFC CWinThread, but I don't want to use MFC for this project, so I have only 2 chances.

I'll post some code and comment out why I ask you this decission.

I have a class, and I want to launch a member function as a thread, so I use this launcher function:

DWORD WINAPI ReceiveThreadProcStub(LPVOID pObj)
{
((CClass1*)pObj)->Receive(pObj);
ExitThread(0);
}

To launch the thread I use:

void CClass1::Func1()
{
.....
hReceiveThread = CreateThread(NULL,0,ReceiveThreadProcStub,this,0,&nReceiveThreadId);
....
}

So I pass the parameter "this" in order to execute the CClass1::Receive() function in a new thread. I use some CRT functions, and I have readed that using "CreateThread" may cause memleaks with CRT. But I don't know if in this case there should be memleaks, as the function I'm running in the new thread is a member of a class, so maybe this could prevent memleaks on the object destruction.

That's my question.

P.S.: Is there any method for forcing a thread to terminate (from the outside of the thread) without using "TerminateThread"?

Thanks

Re: Use CreateThread or _beginthreadex?

Andrew Walker6-Feb-04 17:48

Andrew Walker

6-Feb-04 17:48

I strongly recommend using boost::thread, which internally uses _beginthreadex. Personally while I've been learning about threading I've spent more time worring more about the higher level details rather than about specific API calls.

Boost::thread prevents many of the common problems - for instance it guarantees that the thread is running before the constructor finishes, as well as providing a variety of lock mechanisms and providing a general way to pass in any function with any signature.

It also provides a way to ensure that a thread will finish.

http://www.boost.org/[^]

If you can keep you head when all about you
Are losing theirs and blaming it on you;
If you can dream - and not make dreams your master;
If you can think - and not make thoughts you aim;
Yours is the Earth and everything that's in it.

Rudyard Kipling

Re: Use CreateThread or _beginthreadex?

Alexander ^M.,7-Feb-04 3:04

Alexander ^M.,

7-Feb-04 3:04

that depends on the question if you use CRT code in your new thread.
the only difference between _beginthreadex and CreateThread is that CRT allocated per-thread data when using _beginthreadex.
have a look at "threadex.c" for further details.

(I don't use _beginthreadex, because I don't use CRT, I've written all functions myself so I don't need CRT.)

Don't try it, just do it! Wink | ;-)

CMainFrame in DLL

sjcomp6-Feb-04 9:04

sjcomp

6-Feb-04 9:04

I am writing a plug-in, which is a DLL (not exporting MFC classes). My dll exports a function, when it is called I show the MFC dialog window. Like this (I have an application class to support mfc, created by wizard):
void my_func()
{
CMyDlg dlg;
dlg.ShowModal();
}

This works. I have a problem, when I am trying to use Frame based window. I have a SDI frame and I can show it. But when I was closing it I have an exception in CFrameWnd::OnClose(), because this function closes the document and then tries to access it. I overrided CMainFrame::OnClose(), so it solved the problem (I just hide my frame). But when the host application terminates I have an access violation at CThreadSlotData::GetThreadValue(int nSlot) function at this line:
ASSERT(m_pSlotData[nSlot].dwFlags & SLOT_USED);

Anybody knows why should this happen? Maybe my dll tries to process some message, which it shouldn't? Any suggestions? Host application calls another exproted function from my dll, before exiting, but this function is not called, so I wonder how does my dll knows about termination, before host application infroms it about it?

Thanks in advance.

Regards,
Alexander.

Image processing!

tuantt6-Feb-04 8:42

tuantt

6-Feb-04 8:42

Dear all Members,
Luckily, I found this site on the net. I knew you are the professonal VC programmers.Help me please.
I used MFC to make my program(related to image processing). There were some questions I would like to ask you:
1.How to display and modify the R,G,B value of a loaded image?
2.I have a 24bit bmp image.How to display the Rimage, Gimage and Bimage??(that's mean on the screen there are 4 images:RGBimage,Rimage,Gimage and Bimage).
3. How to display the R,G,and B histogram?
THank you in advance!!
Best regards,
Mr.Tran.

Mr.Tran

Re: Image processing!

sjcomp6-Feb-04 9:11

sjcomp

6-Feb-04 9:11

You can look at following places:
http://ece.unh.edu/svpal/Users/shyrokov/index.html
it has source code available. You can see how to load image and how to display, though it does not work with 24 bit images, it could help you. It also has routins for histogram calculation.

http://www.intel.com/research/mrl/research/opencv/

Is a special library dedicated to image processing and you can find it very useful.

Also have a look at libraries like:
http://freeimage.sourceforge.net/
http://corona.sourceforge.net/

Good-luck.

Regards,
Alexander.

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