Re: _beginthread newbie question - C / C++ / MFC Discussion Boards

Re: Howto: get a Two's Complement Checksum

DudleyDoorite31-Jul-03 3:43

31-Jul-03 3:43

Thanks Guys I think I understand alot better now.
I will reply here when I get this working.

=================================
When I was in school, all I wanted was to get out into the real world.
Now that I'm in the real world, all I want is to go back to school.

Extracting Audio from AVI

Anonymous31-Jul-03 2:22

Anonymous

31-Jul-03 2:22

Please help.How to extract audio from AVI fimes using VC++ and DirectX?

Re: Extracting Audio from AVI

Jim Crafton31-Jul-03 8:07

Jim Crafton

31-Jul-03 8:07

Use DirectShow - it comes with Direct X - try reading the docs

¡El diablo está en mis pantalones! ¡Mire, mire!

Real Mentats use only 100% pure, unfooled around with Sapho Juice(tm)!

laser pointer interaction

sleep223131-Jul-03 1:34

sleep2231

31-Jul-03 1:34

i'm supposed to write an application that detects the laser pointer on the image captured from a webcam(which has an infra-red camera in front of it). so first i'm grabbing a frame(as a bitmap file). next i should process this file(check its pixels one by one) but i don't know how to do that part. is there anyone to help me?

Re: laser pointer interaction

Alexander ^M.,31-Jul-03 10:40

Alexander ^M.,

31-Jul-03 10:40

i assume, that there is a red spot where the laser pointer is!

code kinda filter, which creates a second bitmap in memory...
it should scan the original bitmap line by line, and check the pixels for red.
if they are red, they should be white in the second bitmap, if not, then black.
then you check for a small white spot on the second bitmap and you got it!

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

_beginthread newbie question

tareqsiraj31-Jul-03 1:24

tareqsiraj

31-Jul-03 1:24

Hello ppl, i am trying to learn multi-threaded c++ programming and have tried the MSDN example. It works fine with just a simple main function and a thread function. But when i try to implement it in a win32 application, i get the following error.

error C2664: '_beginthread' : cannot convert parameter 1 from 'void (void *)' to 'void (__cdecl *)(void *)'

I am using VC++ 6 with the 2003 platform sdk installed. My project is generated by the WTL AppWizard provided with WTL 7.0. I have put my thread function as a member function to the main dialog class. I have included process.h in stdafx.h

_beginthread(ThreadFunc, 0, NULL);<br />
...<br />
void CMainDlg::ThreadFunc(void * dummy)<br />
{<br />
...<br />
}

Any help/pointer will be very helpful. Thankx in advance.

-Tareq

Re: _beginthread newbie question

Rage31-Jul-03 1:32

Rage

31-Jul-03 1:32

Have you declared the thread function as a static ?

~RaGE();

Re: _beginthread newbie question

Renjith Ramachandran31-Jul-03 1:42

Renjith Ramachandran

31-Jul-03 1:42

In the Thread function You must specify the
Calling convention of the Function

Like
unsigned __stdcall YourThreadFunction(void* pVoid)
{

return something;
}

and try to write the fucntion a a pubic, not a member

Re: _beginthread newbie question

tareqsiraj31-Jul-03 1:50

tareqsiraj

31-Jul-03 1:50

Thankx Rage for the quick reply. I didnt make the function static. That was the problem. Now it works fine but i have another problem. Can i access any objects declared in the mail dlg class? I have an edit box named _edit. if i use _edit.AppendText("blah blah"), it gives me the following error. Cry | :((

error C2228: left of '.AppendText' must have class/struct/union type

Thankx again for your response.

-Tareq

Re: _beginthread newbie question

Jim Crafton31-Jul-03 8:11

Jim Crafton

31-Jul-03 8:11

You're inside a static function of a class - therefor you can't access member functions. Typically what people do is pass in a application variable to the thread's void* argument. In your case, this would be a pointer to the instance of your Dialog class. then you could refernece it.

However with that solved your next problem will arise in making changes to UI controls from outside the main UI thread of execution. You must be very careful when doing this or risk causing lock, or various other wicked and evil things to happen. To simplify this, you might consider Posting a message back to your dialog class instance and then accessing the control there. This way you ensure that you're back in the context of the main UI thread.

¡El diablo está en mis pantalones! ¡Mire, mire!

Real Mentats use only 100% pure, unfooled around with Sapho Juice(tm)!

Re: _beginthread newbie question

User 665831-Jul-03 2:11

User 6658

31-Jul-03 2:11

1. modify your ThreadFunc like this:
void ThreadFunc(void * dummy)
2. call _beginthread like this:
_beginthread(ThreadFunc, 0, this);
3. again, modify your ThreadFunc to call a member function of your CMainDlg:

void ThreadFunc(void * dummy)
{
    CMainDlg* m_pDlg = (CMainDlg*)dummy;
    if(m_pDlg != NULL)
        m_pDlg->ThreadFunc(NULL);
}

regards

modified 12-Sep-18 21:01pm.

Re: _beginthread newbie question

Vitali Halershtein31-Jul-03 4:55

Vitali Halershtein

31-Jul-03 4:55

Hi,

Your thread ThreadFunc is CMainDlg mamber. To use
CRT _beginthread try to declare it as separate function as:

void ThreadFunc(void * dummy)
{
}

Or try to use AfxBeginThread, or CreateThread

Hope it help.

Vitali

Re: _beginthread newbie question

tareqsiraj31-Jul-03 6:53

tareqsiraj

31-Jul-03 6:53

Thank you all for your replys. Greg S. your solution worked like a charm and its so obvious ... i only forgot to cast it to the editor pointer inside the thread function. Big Grin | :-D

... again thank you all for your solutions.

-Tareq

Selecting multiple files in subdirectories

BoudewijnEctor31-Jul-03 1:20

BoudewijnEctor

31-Jul-03 1:20

Hi,

Can somebody tell me how to do this:

I need to get all .c files from a directorie, and all of its subdirs, without having the user to selected them al manually --> he only needs to select one directory!

Thanks

Re: Selecting multiple files in subdirectories

Ted Ferenc31-Jul-03 1:33

Ted Ferenc

31-Jul-03 1:33

MFC CFileFind
Win32 FindFirstFile, FindNextFile

And then recurse down the tree when you find a file that is a sub directory. There MUST be an example on CP

If I have seen further it is by standing on the shoulders of Giants. - Isaac Newton 1676

Re: Selecting multiple files in subdirectories

Jim Crafton31-Jul-03 8:19

Jim Crafton

31-Jul-03 8:19

a quick example if you don't find one:

WIN32_FIND_DATA findData = {0};

HANDLE findHandle = FindFirstFile( "c:\\my\\dir\\of\\cfiles\\*.c", &findData );
if ( INVALID_HANDLE_VALUE != findHandle ) {
  do {
    printf( "found file: %s\n", findData.cFileName );
  } while ( FindNextFile( findHandle, &findData ) ); 
}
else {
  //error handling here
}

I think that will only go into the dir you specify - to recurse down into sub dirs you'll have to add some extra code

¡El diablo está en mis pantalones! ¡Mire, mire!

Real Mentats use only 100% pure, unfooled around with Sapho Juice(tm)!

Dead windows in MFC

BoudewijnEctor31-Jul-03 0:59

BoudewijnEctor

31-Jul-03 0:59

Hi,

Suppose I'm writing a program wich uses 3 windows:

1: select a mode
2: select an input\output path
3: perform some actions (and supply the program with the actions properties)

ans suppose i call those windows win1,win2, and win3.

After havig performed the actions in win3, I'd like to show win1 again and let all the others disappear.

HOW CAN I DO THIS?

all those windows are inherited from CDialog and are showed by calling the DoModal method.

Thank you in advance,

Re: Dead windows in MFC

BoudewijnEctor31-Jul-03 1:08

BoudewijnEctor

31-Jul-03 1:08

And i forgot:

If i try to get back to the last windows (for instance from win3 to win2), both dont react anymore .

CAn you tell me how this is possible (or rather how to solve it)?

Re: Dead windows in MFC

jhwurmbach31-Jul-03 1:20

jhwurmbach

31-Jul-03 1:20

After win3.DoModal() returns with ID_OK, you call win1.DoModal() again.

Or am I missing something? If yes, please post (relevant!) code.

Good luck!

Who is 'General Failure'? And why is he reading my harddisk?!?

Re: Dead windows in MFC

BoudewijnEctor31-Jul-03 1:23

BoudewijnEctor

31-Jul-03 1:23

How to let it return ID_OK?

Re: Dead windows in MFC

jhwurmbach31-Jul-03 1:29

jhwurmbach

31-Jul-03 1:29

I am sorry, it was IDOK.
And you did read the MSDN article about CDialog::DoModal(), did you?
Sorry to be rude, but I think it is the minimum requirement to have read the relevant MSDN articles before asking questions.

Who is 'General Failure'? And why is he reading my harddisk?!?

Re: Dead windows in MFC

BoudewijnEctor31-Jul-03 1:53

BoudewijnEctor

31-Jul-03 1:53

Ok,

thanks --> I did, and it worked quite well

Re: Dead windows in MFC

BoudewijnEctor31-Jul-03 2:01

BoudewijnEctor

31-Jul-03 2:01

But,

I now need to make my own IDs, instead of IDOK i want to use (for instance IDready): can can I do this?

PS: I've already looked in the MSDN

Re: Dead windows in MFC

Ravi Bhavnani31-Jul-03 2:38

Ravi Bhavnani

31-Jul-03 2:38

CMyDialog::OnOK()
{
  // Close the dialog and have DoModal() return a custom return code
  EndDialog (IDready);
}

/ravi

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Re: Dead windows in MFC

BoudewijnEctor1-Aug-03 0:43

BoudewijnEctor

1-Aug-03 0:43

OK,

but if I try to build my solution, the compiler says IDREADY: undeclared identifier, altough I've declared it allready in my class' message map!

What's wrong with this? Confused | :confused:

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.