C / C++ / MFC

21-Aug-02 7:13

try a google search for "Polygon scanline conversion"; that's the 'technical' term for finding the edges of a polygon, given the points. additional hints: "Paul Heckbert" and "Graphics Gems" Smile | :)

-c

Though the cough, hough and hiccough so unsought would plough me through,
enough that I o'er life's dark lough my thorough course pursue.
--Stuart Kidd

Re: A Shading algorithm ?

Stephane Rodriguez.21-Aug-02 7:27

Stephane Rodriguez.

21-Aug-02 7:27

Try with the "raster" keyword as well, Big Grin | :-D

And I swallow a small raisin.

Re: A Shading algorithm ?

yarp21-Aug-02 21:54

yarp

21-Aug-02 21:54

Hard to find indeed, even with the "raster" key word. The Internet is full of 3D Gouraud shading,... luckily one day I intend to do some 3D programming and I'll probably find my algo that time Wink | ;)

It doesn't matter, I'll do it myself.
Thanks

Yarp
http://www.senosoft.com/

Chris Maudre Datagrid

Mazdak21-Aug-02 5:35

Mazdak

21-Aug-02 5:35

In Chris Maunder datagrid,does anybody know how can I overriden EndEdit() for a cell in my class?

Mazy

"If I go crazy then will you still
Call me Superman
If I’m alive and well, will you be
There holding my hand
I’ll keep you by my side with
My superhuman might
Kryptonite"Kryptonite-3 Doors Down

Re: Chris Maudre Datagrid

C^hris L^osinger21-Aug-02 5:36

21-Aug-02 5:36

why don't you post this question on the grid article?

Though the cough, hough and hiccough so unsought would plough me through,
enough that I o'er life's dark lough my thorough course pursue.
--Stuart Kidd

Re: Chris Maudre Datagrid

Mazdak21-Aug-02 7:29

Mazdak

21-Aug-02 7:29

More people see it here.I post it there too.

Mazy

"If I go crazy then will you still
Call me Superman
If I’m alive and well, will you be
There holding my hand
I’ll keep you by my side with
My superhuman might
Kryptonite"Kryptonite-3 Doors Down

terminate a worker thread

lucy21-Aug-02 5:31

21-Aug-02 5:31

I have a Dialog based MFC program, and in CMyDialogDlg::OnCreate I start my worker thread like this:

m_bThreadRun = TRUE;
HANDLE hThread = AfxBeginThread(MyWorkerThread, this);
if ( hThread == NULL )
    MessageBox("Cannot start worker thread.");

While in my worker thread, I check for the flag from parent:

UINT MyWorkerThread(LPVOID pParam)
{
    CMyDialogDlg * pDlg = (CMyDialogDlg *)pParam;
    while ( pDlg->m_bThreadRun)
    {
        // do something
    }
    TRACE("exit from the worker thread");
    return 0;
}

In order to terminate this worker thread, I did this:

CMyDialogDlg::OnClose()
{
   m_bThreadRun = FALSE;
   CDialog::OnClose();
}

But what troubles me is:
1. The trace line of my worker thread function "exit from the worker thread" was never printed.
2. When the program ended, this will appear in my Visual studio debug window:

etected memory leaks!
Dumping objects ->
thrdcore.cpp(166) : {54} client block at 0x017B4558, subtype 0, 112 bytes long.
a CWinThread object at $017B4558, 112 bytes long
Object dump complete.

what I am missing here? How can I terminate this worker thread gracefully?

Thanks a lot for your help!

Tomasz Sowinski21-Aug-02 5:38

Tomasz Sowinski

21-Aug-02 5:38

You should WaitForSingleObject after setting m_bThreadRun to FALSE. Also, add 'volatile' modifier to m_bThreadRun.

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

"Yields falsehood when preceded by its quotation" yields falsehood when preceded by its quotation.

lucy21-Aug-02 6:01

21-Aug-02 6:01

I add the following modifications:

OnCreate()
{
   m_hMyThread = AfxBeginThread(...);
}


OnClose()
{
   m_bThreadRun = FALSE;
   WaitForSingleObject(m_hMyThread, 1000);
}

but WaitForSingleObject will fail and the reason is "The handle is invalid. ". why? Confused | :confused:

FYI, I have added the volatile specifier to my worker thread checking.

RChin21-Aug-02 23:43

RChin

21-Aug-02 23:43

When the worker thread terminates, the Object (CWinThread) will clean up and deallocate any resources associated with it, including itself. So after termination, the CWinThread variable will be invalid as stated.

To avoid this you will need to tell the class not to automatically delete itself on termination.

try this:

OnClose()
{
   // do not automatically delete me
   //
   m_hMyThread.m_bAutoDelete = FALSE; 

   m_bThreadRun = FALSE;   // signal thread for termination ..
   WaitForSingleObject(m_hMyThread, 1000); // .. and wait.

   delete m_hMyThread; // remember to clean up
   m_hMyThread = NULL; // not neccessary, but just to be clean.
}

lucy22-Aug-02 2:41

22-Aug-02 2:41

I see. Thank you very much!

C^hris L^osinger21-Aug-02 5:41

21-Aug-02 5:41

when i do this, i usually have a loop in the parent thread that's checking for a flag from the worker thread.

worker:
1.do something
2.check the bCancel flag, if it's set, set the bDone flag
2.set a bDone flag when done

parent:
1.launch thread
2.if the worker thread's bDone flag is set, kill the thread, else do something else and check the bDone flag again, later.
3.if i need to kill the worker thread, set a bCancel flag, wait for it's bDone flag.

-c

Though the cough, hough and hiccough so unsought would plough me through,
enough that I o'er life's dark lough my thorough course pursue.
--Stuart Kidd

lucy21-Aug-02 6:08

21-Aug-02 6:08

one thing I am confused here:

is it possible for the worker thread to do a "return" when it finds that bCancel flag is set? It seems it is a lot more easier.

C^hris L^osinger21-Aug-02 6:16

21-Aug-02 6:16

the worker still has to set "bDone", so that the parent will know that the thread is really done. just setting bCancel isn't enough, since the worker might still be busy.

Though the cough, hough and hiccough so unsought would plough me through,
enough that I o'er life's dark lough my thorough course pursue.
--Stuart Kidd

lucy21-Aug-02 7:17

quick question about recordsets, ADO

21-Aug-02 7:17

this is elegant. Thanks!

ns21-Aug-02 4:54

21-Aug-02 4:54

I get back from a query the result that the number of records found is 0.

Immediately after I process commands with this rs. It crashes. So I want to put in an exit like

if(rs has zero records)
{

do this
return

}

However I dont know how to state 'rs has zero records'....in ADO. I dont see an isEmpty type function in the docs.

I am using ADO.

Thanks,
ns

Re: quick question about recordsets, ADO

Ravi Bhavnani21-Aug-02 5:24

Re: quick question about recordsets, ADO

21-Aug-02 5:24

GetRows() perhaps? (I don't know ADO).

/ravi

Let's put "civil" back in "civilization"
http://www.ravib.com
ravib@ravib.com

Ravi Bhavnani21-Aug-02 5:25

Re: quick question about recordsets, ADO

21-Aug-02 5:25

Or maybe you could check its EOF property? (Sorry, just guessing.)

/ravi

Let's put "civil" back in "civilization"
http://www.ravib.com
ravib@ravib.com

Blade[DMS]21-Aug-02 5:28

Blade[DMS]

21-Aug-02 5:28

When the Recordset is empty, both the BOF and EOF flags are set,
so...

if (rs.IsBOF() && rs.IsEOF())
{
   do this
   return
}

should be what you want....

Blade[DMS]

I tried this, but

ns21-Aug-02 5:36

21-Aug-02 5:36

This didnt pass the compiler: IsEOF is a dao thing, EOF is not an ADO thing either. getting close though.... Smile | :)

/*  if((m_photoDb.m_pRecordsetPhoto.BOF = TRUE) &&
                  ( m_photoDb.m_pRecordsetPhoto.EOF = TRUE))
    {
        AfxMessageBox ("empty rs");
        return;
    }*/

Thanks for the responses,
ns

OOPS! I think I need ->EOF not .EOF....I'm trying it now.
DArn! That wasnt it.

Ravi Bhavnani21-Aug-02 5:39

21-Aug-02 5:39

== not =

/ravi

Let's put "civil" back in "civilization"
http://www.ravib.com
ravib@ravib.com

ns21-Aug-02 5:46

21-Aug-02 5:46

guess what - I tried that too....I really did.

Compiling...
Train1View.cpp
C:\Train1View.cpp(2473) : error C2059: syntax error : '('
C:\Train1View.cpp(2474) : error C2143: syntax error : missing ';' before '{'
C:\Train1View.cpp(2475) : error C2039: 'AfxMessageBox' : is not a member of '_Recordset'
        c:\trainer\a_tr series\tr8b\release\msado15.tlh(1696) : see declaration of '_Recordset'
C:\Train1View.cpp(2488) : error C2039: 'm_photoDb' : is not a member of '_Recordset'
        c:\trainer\a_tr series\tr8b\release\msado15.tlh(1696) : see declaration of '_Recordset'
C:\Train1View.cpp(2488) : error C2039: 'GetPhotoBuffer' : is not a member of '_Recordset'
        c:\trainer\a_tr series\tr8b\release\msado15.tlh(1696) : see declaration of '_Recordset'
Error executing cl.exe.

Ravi Bhavnani21-Aug-02 5:51

21-Aug-02 5:51

Mail me Train1View.cpp. Looks like you got a misplaced ->.

/ravi

Let's put "civil" back in "civilization"
http://www.ravib.com
ravib@ravib.com