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i think its not a safe practice to access the m_TerminateThread variable in main UI thread from another thread, without using any locking mechanisms. Better to use an Event object, which is initially non-signalled, set it to signaled in CDataControls::OnClose(), and wait on thread handle. And in Thread function,
while(WAIT_OBJECT_0 != WaitForSingleObject(self->m_hEvent,0))
{
self->DoDataGrab();
Sleep(100);
}
or,
while(WAIT_OBJECT_0 != WaitForSingleObjectself->m_hEvent,100))
{
self->DoDataGrab();
}
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Actually it is safe in this particular case. As the worker thread only ever reads the state of the variable, but he has to make sure it is reading the changes on each loop, i.e. it must be declared [code]mutable[/code] elase a compiler optimisation step may remove the follow on reads.
As long as multiple threads are not read/writing it should be fine.
If you vote me down, my score will only get lower
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IMO it needs to be no wider than what can be handled atomically (hence 32-bit) AND declared volatile. Then it does not matter how many readers there are, as long as there is only one writer all is fine. With several writers, it most often needs a lock of some kind.
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Cool_Dev wrote: Better to use an Event object,
Thanks, I tried this - it works ok but I still need the WaitForSingleObject() in the CDataControls::OnClose() (see below) Why is this?
void CDataControls::OnClose()
{
SetEvent(g_Event);
WaitForSingleObject(pDataGrabThread>m_hThread,1000);
CDialog::OnClose();
}
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because you need to give the thread a chance to see the event and react to it.
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Thanks! Sometimes it's good to know why, not just that it works
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Caslen wrote: ::SendMessage(m_ControlsDialog,WM_CLOSE,0,0); //send a message to close the dialog and thread
You've not shown how m_ControlsDialog was declared. I assume it's safe to send a message to. If it's a modeless dialog, why not just call DestroyWindow() ?
Caslen wrote: while(self->m_TerminateThreads!=0)
This loop is suspect if m_TerminateThreads is not declared as volatile . Otherwise, it may or may not execute, or it may fail to end. Because m_TerminateThreads is not being changed within the loop, the compiler would likely optimize it out.
A better way of having the secondary thread end is to have the primary thread signal an event.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Man who follows car will be exhausted." - Confucius
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I already figured out the 'volatile' thing - I was more concerned about why I had to 'SendMessage' from CMainFrame::OnClose() - why wasn't CDataControls::OnClose() automatically closed when the App is closed?
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Caslen wrote: ...why wasn't CDataControls::OnClose() automatically closed when the App is closed?
Because it was in the secondary thread, which was not terminating, perhaps? To test this, change your code to:
WaitForSingleObject(pDataGrabThread->m_hThread, INFINITE);
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Man who follows car will be exhausted." - Confucius
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Ok, that is probably it - but it's correct to use SendMessage() from CMainframe to close it though?
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Caslen wrote: ...but it's correct to use SendMessage() from CMainframe to close it though?
Is the dialog modeless?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Man who follows car will be exhausted." - Confucius
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Then just call DestroyWindow() .
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Man who follows car will be exhausted." - Confucius
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Note that you should declare m_TerminateThreads as mutable volatile as a compiler optimisation could break your code.
These lines
while(self->m_TerminateThreads!=0)
{
self->DoDataGrab();
could be interpreted as the compiler as:
if (self->m_TerminateThreads!=0)
{
for (;;)
{
self->DoDataGrab();
If you vote me down, my score will only get lower
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Hi
I want to draw line on OnMouseMove function of a dialog class.I want to draw
the line in one color(fixed color not inverse color ),but it is showing in
different/inverse color. If I omit SetROP2 the line will get spread.
<code>
CDC* pDC = this->GetDC();
int nR2 = pDC->SetROP2( R2_NOTXORPEN );
pDC->MoveTo(m_StartPoint);
pDC->LineTo(m_Previouspoint);
m_Previouspoint = point;
pDC->MoveTo(m_StartPoint);
pDC->LineTo(point);
</code>
How to solve it?
thanks
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Please find previous thread.
that will help you
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Exactly how would finding a thread help in drawing a line?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Man who follows car will be exhausted." - Confucius
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Benjamin Bruno wrote: I want to draw
the line in one color(fixed color not inverse color )
Did you select such a Pen object to your CDC before calling LineTo() function?
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// Add URL
void LeftView::AddUrl(void)
{
CTreeCtrl& trCtrl = GetTreeCtrl();
HTREEITEM hitem,hitem1,hitem3;
hitem = trCtrl.InsertItem(_T("URL"),TVI_ROOT,TVI_LAST);
for(inti=0; i<arrLines.GetSize();i++)
{
CString str = arrLines.GetAt(i);
trCtrl.InsertItem(str,hitem,TVI_LAST);
intk;
}
}
// REad text
arrLines.RemoveAll();
CString pszFileName(_T("D:\\URL\\TextFile.txt"));
CString strLine =_T("");
TRY
{
CStdioFile file(pszFileName, CFile::modeRead);
while( file.ReadString(strLine))
{
arrLines.Add(strLine);
}
}
CATCH_ALL(e)
{
e->ReportError(); // shows what's going wrong
}
END_CATCH_ALL
void LeftView::OnTvnSelchanged(NMHDR *pNMHDR, LRESULT *pResult)
{
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
NM_TREEVIEW *pNMTreeView = (NM_TREEVIEW *) pNMHDR;
CTreeCtrl &tTree = this->GetTreeCtrl ();
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
CString str("Test");
sFullList=" ";
sFullList += tTree.GetItemText(pNMTreeView->itemNew.hItem);
if( sFullList.CompareNoCase("URL") == 0)
{
GetDocument ()->UpdateAllViews ( this, 1L, (CObject *) &sFullList );
}
*pResult = 0;
}
BOOL LeftView::PreCreateWindow(CREATESTRUCT& cs)
{
// TODO: Add your specialized code here and/or call the base class
cs.style |= TVS_HASLINES | TVS_HASBUTTONS | TVS_LINESATROOT | TVS_EDITLABELS;
returnCTreeView::PreCreateWindow(cs);
}
CSplitterWindowDoc* LeftView::GetDocument() // non-debug version is inline
{
ASSERT(m_pDocument->IsKindOf(RUNTIME_CLASS(CSplitterWindowDoc)));
return(CSplitterWindowDoc*)m_pDocument;
}
void CSplitterWindowView::OnUpdate(CView* pSender, LPARAM lHint, CObject* pHint)
{
// TODO: Add your specialized code here and/or call the base class
if(lHint==1L)
{
CString sListToDisplay = ((CString*)pHint)->GetBuffer(0);
Navigate2(sListToDisplay,NULL,NULL);
}
CSingleDocTemplate* pDocTemplate;
pDocTemplate = newCSingleDocTemplate(
IDR_MAINFRAME,
RUNTIME_CLASS(CSplitterWindowDoc),
RUNTIME_CLASS(CMainFrame), // main SDI frame window
RUNTIME_CLASS(LeftView));
if(!pDocTemplate)
returnFALSE;
AddDocTemplate(pDocTemplate);
In OnTVNSelChanged funtion i want to check wheather i have clicked the root node. Can any one tell how to check this
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Use GetSelectedItem[^] and compare it to your root HTREEITEM using GetRootItem[^]
Also, wrapping code into <pre></pre> tags will make it more readable.
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For what domain? Some domains seem to attract coding standards like flies to jam and people can get very anal about things.
However coding standards are usually set locally by whoever thinks they know best. Usually they (and I include myself in that) don't so just use your common sense and domain knowledge to name things.
Cheers,
Ash
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Any domain ones can suggest the reference to.
Simple scenario as in the link from the post with opposite initializers, finalizers pairs.
It would be handy to have a reference to common names used and not to exert you brain too much.
That is not the post about coding standards but about naming helper, it does not matter if the helper refers to initialize_system or InitializeSystem.
Чесноков
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Buy a thesaurus?
This is actually a serious suggestion, I keep one (and a dictionary) on my desk to look for synonyms for overused words.
Cheers,
Ash
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I'd be interested in your comments on this question[^].
It's time for a new signature.
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