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There is no problem starting a thread in OnInitDialog(), you just have to be very careful when using MFC objects (particularly objects derived from CWnd) in multiple threads.
Anyway, i suspect that here your code isn't compiling (i assume that's what you mean when you said that it doesn't work) because GetDlgItem() doesn't have enough parameters. Since the thread function is a global function, and not a member of CGrapDlg, it does not have access to the member functions of CGrapDlg (and CWnd from where it is derived). This means that when you call GetDlgItem() here, it is actually calling the SDK version, not the CWnd version. The SDK version of GetDlgItem() takes two parameters: the HWND of the dialog box, and then ID of the control. To get around this, you could cast the pParam parameter to a CGrapDlg, and then call the GetDlgItem() member function.
However, there are two issues here:
1) This uses CWnd-derived MFC objects in multiple threads, which is error prone. You could get around this by passing in the HWND instead, and calling the SDK directly.
2) By the sound of the thread function name, you are planning to do some drawing within this thread. In general, this is not recommended, as the dialog will also be painting itself (by handling WM_PAINT and WM_ERASEBACKGROUND), and so it is very likely that anything you draw in your thread will never be seen by the user.
Dave
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regarding issue 2...i need some calculations to know what to draw and i thought if these had to be performed each time WM_PAINT is sent, it'll take a long time. That's why i placed the functions under OnInitDialog().
But after thinking through what you pointed out to me, maybe i should do the calculations in OnInitDialog() and the final display in OnPaint()?
thanks alot...i didnt know a thread is a global function before.;P
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Use this code:
BOOL CGrapDlg::OnInitDialog()
{
CDialog::OnInitDialog();
AfxBeginThread(PlotAttenuationThread, this);
return TRUE;
}
UINT PlotAttenuationThread(LPVOID pParam)
{
CGraphDlg* pDlg=(CGraphDlg*) pParam;
CWnd* gFrame = (CWnd*)pDlg->GetDlgItem(IDC_GRAPH_FRAME);
CDC* pDC = gFrame->GetDC();
ReleaseDC(pDC);
return 0;
}
A. Riazi
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One problem you should be seeing is that the thread function is not a member function of CGrapDlg so you can't call GetDlgItem.
Also what Dave has posted regarding the use of MFC objects accross threads is a problem that cannot be ignored. There are Technical Notes on MSDN regarding this problem.
"No matter where you go, there your are..." - Buckaoo Banzi
<pete/>
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How change a color of the cell and color of the text in Excel table via OBDC.
CDatabase database;
...
database.OpenEx(sSql,CDatabase::noOdbcDialog)
...
sSql = "CREATE TABLE Station (Train CHAR,Times CHAR,Way NUMBER,Comment CHAR)";
database.ExecuteSQL(sSql);
...
sSql.Format("INSERT INTO Station (Train,Times,Way,Comment) VALUES ('%s','%s',%d,'%s')",sTrain,sTime,iWay,sComment);
database.ExecuteSQL(sSql);
I want that color of this record was red.
// Sorry for my Englsih
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Maybe with ADOX? otherwise, why not use the Excel COM objects?
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It is good. But can you write a simple example how to use it? Or tell me how to do it? Or where can i read this in the internet?
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Hi,
I remember seeing once an articale that showed how you can send email
from a c++ program.
Any help will be appreciated.
Tahnks
Shay
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For starters try this article, http://www.codeproject.com/internet/zsmtp.asp[^]
From the Internet section on CP, you should be able to find several others.
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.
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Thank you,
That was what I was looking for
Shay
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Hi I'm new to SDI programming so I would need some guidance from you all..
How can I make sure that my window is maximised when I run my application? I keep having to click on the maximise button after I compile and run my project.
Thx 
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In CMainFrame::PreCreateWindow(), put a ShowWindow(SW_SHOWMAXIMIZED);
~RaGE();
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Ok,
I'm creating a Tree that traverses system drives. Is there a way to automatically refresh removable drives and cdrom drives? Is there a windows message that gets sent out when a new cd or floppy is inserted??
Thanks
Dan Willis
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in your mainframe window do :
/////////////////////////////////////////////////////////////////
// OnDeviceChange
/////////////////////////////////////////////////////////////////
#include <dbt.h>
BOOL CMainFrame::OnDeviceChange (UINT nEventType, DWORD dwData)
{
if (nEventType == DBT_DEVICEARRIVAL)
{
DEV_BROADCAST_HDR * pDevBroadcastHdr = (DEV_BROADCAST_HDR*)dwData;
if (pDevBroadcastHdr->dbch_devicetype == DBT_DEVTYP_VOLUME) // Logical Volume
{
DEV_BROADCAST_VOLUME* pDevBroadcastVolume = (DEV_BROADCAST_VOLUME*)pDevBroadcastHdr;
// on cherche la lettre du nouveau disque
if (pDevBroadcastVolume->dbcv_flags & DBTF_MEDIA)
{
char cVolume;
ULONG unitmask = pDevBroadcastVolume->dbcv_unitmask;
for (int i = 0; i < 26; ++i)
{
if (unitmask & 0x1)
break;
unitmask = unitmask >> 1;
}
cVolume = (i + 'A');
}
}
}
if (nEventType == DBT_DEVICEREMOVECOMPLETE)
{
}
return TRUE;
}
=============================
in your mainfrm.h
afx_msg BOOL OnDeviceChange (UINT nEventType, DWORD dwData);
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in your message map of your MainFrame add also:
BEGIN_MESSAGE_MAP(CMainFrame, CMDIFrameWnd)
//{{AFX_MSG_MAP(CMainFrame)
ON_WM_CREATE()
....
//}}AFX_MSG_MAP
ON_WM_DEVICECHANGE()
_MESSAGE_MAP()
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That did it.
Thanks alot!
Dan Willis
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How to detect that a drive is a DVD ?
The function GetDriveType is not helpful
Thanks
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If you want to detect drive is DVD or CD, first use GetDriveType, then check capacity of disk. CD-ROM takes about 650-700 MB of data. If capacity is more than 700MB, it is a DVD!
A. Riazi
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Search for STORAGE_MEDIA_TYPE. It's an enumeration defined in winioctl.h. I believe this is what you're looking for.
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thanks, this was a good hint.
I have put the solution on the thread
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<br />
#include <Winioctl.h><br />
BOOL CMainFrame::IsItADvd (char cVolume)<br />
{<br />
BOOL bResult = FALSE;<br />
CString sTemp;<br />
GET_MEDIA_TYPES GetMediaTypes;<br />
DWORD dwBytesReturned;<br />
<br />
sTemp.Format ("\\\\.\\%c:", cVolume);<br />
sTemp.MakeUpper ();<br />
HANDLE hDevice = CreateFile(sTemp,GENERIC_READ, FILE_SHARE_READ,NULL, OPEN_EXISTING, 0, NULL);<br />
<br />
if (hDevice == INVALID_HANDLE_VALUE)<br />
return FALSE;<br />
<br />
if (DeviceIoControl(hDevice, IOCTL_STORAGE_GET_MEDIA_TYPES_EX, NULL, 0, (void*)&GetMediaTypes, sizeof (GET_MEDIA_TYPES), &dwBytesReturned, NULL))<br />
bResult = (GetMediaTypes.DeviceType == FILE_DEVICE_DVD);
<br />
CloseHandle (hDevice);<br />
return bResult;<br />
}<br />
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