C / C++ / MFC Discussion Boards

masnu28-Feb-06 6:54

28-Feb-06 6:54

Is there a way of sending my class a pointer to my view's DC. I would like to draw to the DC and then "blit" it back to the screen. Until now I have only been able to get the DC for the main window.

Thanks.

Re: SDI's View DC

PJ Arends28-Feb-06 7:40

PJ Arends

28-Feb-06 7:40

CFrameWnd::GetActiveView will return a pointer to your CView derived window, you can call GetDC on that view

You may be right
I may be crazy
But it just may be a lunatic you’re looking for
-- Billy Joel --

Within you lies the power for good - Use it!

Re: SDI's View DC

masnu28-Feb-06 7:59

masnu

28-Feb-06 7:59

I tried what you suggested and I get an "illegal call of non-static member function" error.

CView* pView = CFrameWnd::GetActiveView();<br />
CDC* pDC = myview->GetDC();

I am new to the whole MFC programming scene so I am sure I am doing something really silly.

Thanks for the help.

-- modified at 14:00 Tuesday 28th February, 2006

Re: SDI's View DC

David Crow28-Feb-06 8:12

David Crow

28-Feb-06 8:12

masnu wrote:
CView* pView = CFrameWnd::GetActiveView();

GetActiveView() is not a static function (i.e., one that can be called without an actual object). You must call it in the context of a CFrameWnd object, not CFrameWnd itself.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: SDI's View DC

masnu28-Feb-06 8:52

masnu

28-Feb-06 8:52

David,

From what you said I assume I need to put the code in my CMainFrame class, which I did. I no longer get a compiler error, but I get an access violation error in the objcore.cpp file:

BOOL CObject::IsKindOf(const CRuntimeClass* pClass) const<br />
{<br />
	ENSURE(this != NULL);<br />
	// it better be in valid memory, at least for CObject size<br />
	ASSERT(AfxIsValidAddress(this, sizeof(CObject)));<br />
<br />
	// simple SI case<br />
	CRuntimeClass* pClassThis = GetRuntimeClass();   //ERROR HERE<br />
<br />
	ENSURE(pClassThis);<br />
	return pClassThis->IsDerivedFrom(pClass);<br />
}

What I have is:

void CMainFrame::Scroll()<br />
{<br />
	CDC* pDC = CFrameWnd::GetActiveView()->GetDC();<br />
<br />
	CStripChart* pStrip;<br />
	pStrip->Scroll(pDC);<br />
}

Any suggestions?

Thanks.

Re: SDI's View DC

David Crow28-Feb-06 9:05

David Crow

28-Feb-06 9:05

masnu wrote:
CStripChart* pStrip;
pStrip->Scroll(pDC);

This looks suspect. How has pStrip been initialized?

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: SDI's View DC

masnu28-Feb-06 9:37

masnu

28-Feb-06 9:37

When I debug, that code doesn't even run. The problem occurs when

CDC* pDC = CFrameWnd::GetActiveView()->GetDC();

is executed.

CStripChart is just a class I created to accept a DC and draw a grid to it and plot what ever data is sent to it. I have scroll function as a seperate thread. Could this be a problem?

Is there any way I can get a pointer to the view's DC and pass it to my class for furture use? Or would I need to pass a new DC everytime I wanted to update my window?

Re: SDI's View DC

David Crow28-Feb-06 10:01

David Crow

28-Feb-06 10:01

What does GetActiveView() return? If it is NULL, then dereferencing the pointer will cause problems.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: SDI's View DC

masnu28-Feb-06 10:34

masnu

28-Feb-06 10:34

It doesn't return anything. I get the error before it returns.

Re: SDI's View DC

David Crow28-Feb-06 10:40

David Crow

28-Feb-06 10:40

When/how is CMainFrame::Scroll() called?

masnu wrote:
I get the error before it returns.

Since GetActiveView() and GetDC() are called within the same statement, are you sure?

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: SDI's View DC

masnu28-Feb-06 10:43

masnu

28-Feb-06 10:43

As a quick test I modified the app's file open command:

ON_COMMAND(ID_FILE_OPEN, &CMainFrame::Scroll)

Re: SDI's View DC

David Crow28-Feb-06 10:45

David Crow

28-Feb-06 10:45

masnu wrote:
ON_COMMAND(ID_FILE_OPEN, &CMainFrame::Scroll)

What is the ampersand doing there?

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: SDI's View DC

masnu28-Feb-06 10:54

masnu

28-Feb-06 10:54

I just followed the same format as all the other ON_COMMAND declarations. I tried runnig the program without the ampersand and I still get the same problem.

Re: SDI's View DC

PJ Arends28-Feb-06 11:00

PJ Arends

28-Feb-06 11:00

void CMainFrame::Scroll()
{
CDC *pDC = this->GetActiveView()->GetDC();

You may be right
I may be crazy
But it just may be a lunatic you’re looking for
-- Billy Joel --

Within you lies the power for good - Use it!

How Thread Run Parallely

zahid_ash28-Feb-06 6:52

zahid_ash

28-Feb-06 6:52

I have created my own class CThread inherited from CWinThread,
I am Starting Threads using

for loop begin
AfxBeginThread(RUNTIME_CLASS(CThread));
for loop ends

I have created 15 thread in a loop, will they run parallely or with the time slice scheduling, Actualy I want that they should run parralelly , so that i can write in 15 different file simaltinoiusly.

I want to work fast on these threads.

Regards.

Re: How Thread Run Parallely

David Crow28-Feb-06 7:13

David Crow

28-Feb-06 7:13

zahid_ash wrote:
...I have created 15 thread in a loop, will they run parallely or with the time slice scheduling...

They will never run in parallel on a uniprocessor machine.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: How Thread Run Parallely

zahid_ash28-Feb-06 7:42

zahid_ash

28-Feb-06 7:42

Is there any technique to write in the in the different file parallely or read from them .

i want to shorten the read write time

Regards.

Re: How Thread Run Parallely

Maximilien28-Feb-06 7:46

Maximilien

28-Feb-06 7:46

not with a single CPU computer.

Maximilien Lincourt
Your Head A Splode - Strong Bad

Re: How Thread Run Parallely

David Crow28-Feb-06 7:50

David Crow

28-Feb-06 7:50

I think so, as long as the read and write operations are not happening at the exact spot in the file. See LockFile() for more.

zahid_ash wrote:
i want to shorten the read write time

Well, creating a bunch of threads on a uniprocessor machine is one way to not "shorten the read write time." The overhead of context-switching between all of the threads will be your demise.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: How Thread Run Parallely

zahid_ash28-Feb-06 7:58

zahid_ash

28-Feb-06 7:58

Will they run parallely on multi processor machine.

How can i demise the context switching of thread,

Regards.

Re: How Thread Run Parallely

David Crow28-Feb-06 8:10

David Crow

28-Feb-06 8:10

zahid_ash wrote:
Will they run parallely on multi processor machine.

Yes, but I've no experience with this. I think SetThreadIdealProcessor() will be required.

zahid_ash wrote:
How can i demise the context switching of thread,

I'm not sure exactly what it is that you are asking here, but I think the answer is, "When more than one thread is involved, the processosr will need to periodically switch between them so that at any given monent, only one thread is actually active." This obviously incurs overhead that cannot be avoided.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Open and write in XML-Document

hanno2528-Feb-06 5:16

hanno25

28-Feb-06 5:16

Hi!

DOes anybody know, what I have to do, if I want either to create an new .XML-File or open an existing .XML-File to write at the beginning of this file?
I thought, that I can handle this like a normal text-file but that has been a mistake.
So, if anybody knows something about this, please let me know!

Thanks, Hanno

Re: Open and write in XML-Document

David Crow28-Feb-06 5:29

David Crow

28-Feb-06 5:29

Use IXMLDocument or DOMDocument.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: Open and write in XML-Document

hanno2528-Feb-06 5:43

hanno25

28-Feb-06 5:43

Thanks for your help. Could you send a small piece of code, explaning this a little bit?
With best regards, Hanno

Re: Open and write in XML-Document

David Crow28-Feb-06 5:46

David Crow

28-Feb-06 5:46

Why not just Google for those two interfaces? Also try CodeProject articles, and MSDN.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

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