C / C++ / MFC

Re: Send a message from a thread to a function with parameters

5-Feb-03 0:48

I've got this working:

The Thread:

<br />
<small>UINT CheckMessages(LPVOID Param)<br />
{<br />
	CString tekst = "This is a tekst or maybe a structure";<br />
	::PostMessage((HWND)Param, WM_DATARECEIVED, (WPARAM)&tekst, 0);<br />
	return 0;<br />
}</small><br />

The header:

<br />
<small>protected:<br />
	//{{AFX_MSG(CPLCClientView)<br />
	afx_msg void OnDataReceived(WPARAM wParam, LPARAM lParam);<br />
//}}AFX_MSG<br />
	DECLARE_MESSAGE_MAP()</small><br />

The Function:

<br />
<small>BEGIN_MESSAGE_MAP(CPLCClientView, CFormView)<br />
	//{{AFX_MSG_MAP(CPLCClientView)<br />
	ON_MESSAGE(WM_DATARECEIVED, OnDataReceived)<br />
	//}}AFX_MSG_MAP<br />
END_MESSAGE_MAP()<br />
<br />
...<br />
<br />
...<br />
<br />
void CMyClass::OnDataReceived(WPARAM wParam, LPARAM lParam)<br />
{<br />
	CString tekst = (CString)wParam; // or something like that....<br />
	AfxMessageBox(tekst);<br />
}</small>

If i execute this i get a weird looking character(because i get a number with wParam), how can i send the CString towards my function?

me = Visual C++ n00b

Chris Meech5-Feb-03 1:25

Chris Meech

5-Feb-03 1:25

willempipi wrote:
void CMyClass::OnDataReceived(WPARAM wParam, LPARAM lParam)
{
CString tekst = (CString)wParam; // or something like that....
AfxMessageBox(tekst);
}

Where you cast the wParam to a CString, I think you should cast it to a CString* instead. You will find however that this too will not work as you expect though. By the time you execute the message handler, OnDataReceived, the thread proc will have already finished and the instance of a CString on the stack will no longer exist. I would suggest that you 'new' a CString in the thread proc and then 'delete' the CString in the OnDataReceived method.

Chris Meech

"what makes CP different is the people and sense of community, things people will only discover if they join up and join in." Christian Graus Nov 14, 2002.

"AAAAAAAAAHHHHHH!!!!! Those leaks are driving me crazy! How does one finds a memory leak in a garbage collected environment ??! Daniel Turini Nov. 2, 2002.

Re: Send a message from a thread to a function with parameters

willempipi5-Feb-03 1:58

Re: Send a message from a thread to a function with parameters

5-Feb-03 1:58

Chris Meech wrote:
I would suggest that you 'new' a CString in the thread proc

can't i send the CString with the Message toward the function (like OnPaint sends a point value with it's message) so that it would look a little like this:

<small>void CPLCClientView::OnDataReceived(CString tekst)<br />
{<br />
	AfxMessageBox(tekst);<br />
}</small>

The Visual C++ n00p

HENDRIK R5-Feb-03 2:11

HENDRIK R

5-Feb-03 2:11

willempipi wrote:
can't i send the CString with the Message toward the function (like OnPaint sends a point value with it's message) so that it would look a little like this:

Since you're dealing with user defined messages, no. Sending your own message and handling it with ON_MESSAGE requires you to provide a function declarated like that you did before (with WPARAM and LPARAM as parameters). Only then the message is handled correctly. It's not comparable to messages like WM_PAINT. These are special messages handled by corresponding functions which for sure can have other parameter types.
In fact, you should do it the way described before by creating your CString on the heap (calling new) and passing it as WPARAM to your function.

Re: Send a message from a thread to a function with parameters

willempipi5-Feb-03 2:42

Re: Send a message from a thread to a function with parameters

5-Feb-03 2:42

Schlaubi wrote:
creating your CString on the heap (calling new)

how do you mean this precisly? like this:

CString tekst = new CString;

and,

after i created the tekst, do i have to delete it?

HENDRIK R5-Feb-03 3:14

HENDRIK R

5-Feb-03 3:14

in your thread:

CString *tekst = new CString("blablabla");<br />
<br />
PostMessage(hWnd, WM_MYMESSAGE, (WPARAM)tekst, 0);

in MyFunc:
...

CString* pStr = (CString*)wParam;<br />
<br />
do_sth_with_string<br />
<br />
delete pStr;

Re: Send a message from a thread to a function with parameters

willempipi5-Feb-03 3:26

Re: Send a message from a thread to a function with parameters

5-Feb-03 3:26

Thnx...

Chris Meech5-Feb-03 2:19

Chris Meech

5-Feb-03 2:19

No you can not pass parameters for user defined messages in that way.

I would suggest that you thoroughly read this article[^]. It is one of the best on this site explaining multi-threading and how to deal with the many issues.

Chris Meech

"what makes CP different is the people and sense of community, things people will only discover if they join up and join in." Christian Graus Nov 14, 2002.

"AAAAAAAAAHHHHHH!!!!! Those leaks are driving me crazy! How does one finds a memory leak in a garbage collected environment ??! Daniel Turini Nov. 2, 2002.

Check Menu Items

satyavasu5-Feb-03 0:46

satyavasu

5-Feb-03 0:46

I was used ownerdraw for Menu Items.I was drawn many menu items with bmps.
But I want check only one item among the no of menuitems.How to change the state of the MenuItem from CHECKED to UNCHECKED?

Re: Check Menu Items

Abbas_Riazi5-Feb-03 1:22

How many processor inside...

5-Feb-03 1:22

Use OnCommandUpdate handler!
A. Riazi

Raphael Kindt5-Feb-03 0:46

Raphael Kindt

5-Feb-03 0:46

Hi world
I'm looking for a function who tell me how many processor (mono or bi) there is inside a computer (mother board)...

Does somebody have an idea?

Thanks in advance...

Hello World!!! Smile | :)

from Raphaël

Re: How many processor inside...

Mike Nordell5-Feb-03 0:53

Mike Nordell

5-Feb-03 0:53

Raphaël Kindt wrote:
I'm looking for a function who tell me how many processor (mono or bi) there is inside a computer (mother board)...

With the introduction of "hyper threading" CPU's, good luck...

But to find out how many CPU's the system thinks are available, you can use GetSystemInfo.

Re: How many processor inside...

Anders Molin5-Feb-03 1:16

Anders Molin

5-Feb-03 1:16

Mike Nordell wrote:
With the introduction of "hyper threading" CPU's, good luck...

Yea, for now, but on Windows Server 2003 you can use GetLogicalProcessorInformation() Wink | ;)

- Anders

Money talks, but all mine ever says is "Goodbye!"

Re: How many processor inside...

Abbas_Riazi5-Feb-03 1:26

5-Feb-03 1:26

Refer to my article: System Information[^]

A. Riazi

.exe from VC++

Anonymous5-Feb-03 0:35

Anonymous

5-Feb-03 0:35

How can I execute an exe from my VC++ 6 application?

Thanks

Abbas_Riazi5-Feb-03 0:39

5-Feb-03 0:39

Use ShellExecute.
A. Riazi

Anonymous5-Feb-03 1:01

Anonymous

5-Feb-03 1:01

Could you give me an example?
Thanks

Rage5-Feb-03 1:10

Rage

5-Feb-03 1:10

Do look at the link in my other post (point 6.4 in Michael Dunn's C++ FAQ). You have all the examples you need to achieve what you need.

~RaGE();

Abbas_Riazi5-Feb-03 1:18

5-Feb-03 1:18

for example, if you want to execute notepad.exe from your dialog, use following statement:

<br />
ShellExecute(m_hWnd, "open", "c:\\WINNT\\notepad.exe", NULL, "c:\\WINNT", SW_SHOWNORMAL);<br />

A. Riazi

Anonymous5-Feb-03 2:31

Anonymous

5-Feb-03 2:31

Thanks!
I appreciate it!

n

Abbas_Riazi5-Feb-03 4:58

5-Feb-03 4:58