Re: how to do flicker-free drawing using memory DC - C / C++ / MFC Discussion Boards

how to do flicker-free drawing using memory DC

lucy6-Jun-02 9:04

6-Jun-02 9:04

I have an SDI MFC application, and I use OnPaint() to draw something to my view. Since my view is updated very frequently, (less than 1 second), I am thinking of using memory DC to reduce the flickering. I tried this:

{
CPaintDC dc(this);
CDC memDc;
memDc.CreateCompatibleDC(&dc);

// create CPen, CBrush, 
// select them to memDc
// and draw using memDc.Ellipse, memDc.MoveTo, memDc.LineTo
// to get the shapes I need

// transfer to display
dc.BitBlt(0,
          0,
          displayWidth,
          displayHeight,
          &memDc,
          0,
          0,
          SRCCOPY);

// restore memDc
// delete all GDI object (CPen, CBrush)
memDc.DeleteDC();
}

but there is nothing on the display. The MSDN document said that I should select a bitmap to my memDc. I did so with a dummy blank bitmap resource I created using resource editor. After I select it to the memDc, there will only be the dummy bitmap displayed on my screen. How could I get my drawing displayed? Confused | :confused:

Re: how to do flicker-free drawing using memory DC

C^hris L^osinger6-Jun-02 9:08

C^hris L^osinger

6-Jun-02 9:08

you need to create a compatible bitmap and select it into the memDc before you draw to memDc.

-c

Cheap oil. It's worth it!

ISEffects - effects for images

Re: how to do flicker-free drawing using memory DC

lucy6-Jun-02 9:19

lucy

6-Jun-02 9:19

Thank you for your fast help. Now I got my drawing dislayed on the monitor, but the background is totally black. And it flickers even worse. Frown | :-(

what could be wrong?

Re: how to do flicker-free drawing using memory DC

lucy6-Jun-02 9:28

lucy

6-Jun-02 9:28

let me try OnEraseBkGround.

Re: how to do flicker-free drawing using memory DC

lucy6-Jun-02 9:41

lucy

6-Jun-02 9:41

Got it. After overwrite the OnEraseBkgnd(), no flicker anymore. Happy.. Smile | :)

Re: how to do flicker-free drawing using memory DC

lucy6-Jun-02 10:00

lucy

6-Jun-02 10:00

I still couldn't figure out why the background color turns to be black instead of the default one. could you give me some clue?

Re: how to do flicker-free drawing using memory DC

Ernest Laurentin6-Jun-02 10:10

Ernest Laurentin

6-Jun-02 10:10

Call FillSolidRect(...) with the memory object.

One good thing about getting older, you don't lose the ages you've been!

Re: how to do flicker-free drawing using memory DC

lucy6-Jun-02 10:28

lucy

6-Jun-02 10:28

now get it. Thank you!

Re: how to do flicker-free drawing using memory DC

Chen Venkataraman6-Jun-02 9:50

Chen Venkataraman

6-Jun-02 9:50

Check this out: http://www.codeproject.com/gdi/flickerfree.asp

Chen Venkataraman

Open port + Process

orcun colak6-Jun-02 8:55

orcun colak

6-Jun-02 8:55

Hi everybody,
On windows xp netstat -o command can show the process id of an open tcp port.
Can i do the same thing on windows nt/9x using an API ?

Thank you,

Orcun Colak

Multithreading & Problem :: MFC

valikac6-Jun-02 7:36

valikac

6-Jun-02 7:36

Hi.

I have discovered a problem with multithreading processes in my program. Here is an example.

- program starts
- CMyProgramApp::InitInstance() calls RestoreState() in CMainFrame()
- RestoreState() restores the windows positions via registry
- RestoreState() restores data (int, char, binary, etc) from registry to variables in CMyProgramDoc()
- RestoreState() calls a function in CMyProgramDoc() which begins a worker thread
- worker thread does some calculation

Problem: For some reason, I have found that if the calculation is big i.e. it takes a long time, the thread never gets closed and deleted.

The worker thread PostMessage main frame a message indicating that it is done. However, sometimes main frame never received the message!

-----
UINT WorkerThreadFunc(LPVOID pParam)
{
...
pWnd->PostMessage(WM_USER_WORKERTHREAD_CLOSED, 0, 0);
return 0;
-----

There is a handler in main frame to handle the message that class a function in doc to close the worker thread; however, I found that if the worker thread takes a long time to finish a calculation, main frame never receive or ignores the PostMessage.

The only problem I can think of right now is I am starting the worker thread too early. In other words, I should start the worker thread after the program has started and all window positions have been restored.

Do you see any other flaws? Please post.

Thanks,
Kuphryn

Re: Multithreading & Problem :: MFC

valikac6-Jun-02 8:37

valikac

6-Jun-02 8:37

Okay.

Damn. The problem was not anything except bad debugging. I made a small mistake that caused a program loop inside the worker thread. The worker thread never PostMessage! It there is a loop that never exits.

The solution was to reset one of the variables I used inside the while look.

The breakpoint feature in Visual C++ is extremely useful!.

Special thanks to IndirectX of GameDev for breaking up the subject about breakpoint.

Kuphryn

The Explorer context menu

Nnamdi Onyeyiri6-Jun-02 7:39

Nnamdi Onyeyiri

6-Jun-02 7:39

OK, i need to make a dll that will add an entry to the windows explorer context menu, i had a look at this article on codeproject but found that I could not make sense of the code, that i need and know is in there. Cananyone help me out?

==================================================
Homepage: www.onyeyiri.co.uk
Email: theeclypse@hotmail.com
"I think Microsoft has invented A.I. My computer has a mind of its own!"

Re: The Explorer context menu

C^hris L^osinger6-Jun-02 9:08

C^hris L^osinger

6-Jun-02 9:08

look around a bit on this site... there are a ton of articles on shell extensions.

-c

Cheap oil. It's worth it!

ISEffects - effects for images

Re: The Explorer context menu

Michael Dunn6-Jun-02 15:39

Michael Dunn

6-Jun-02 15:39

I have tutorials [part 1 and part 2] on this subject. Maybe a tutorial format will be easier for you to digest. Smile | :)

--Mike--
Just released - RightClick-Encrypt - Adds fast & easy file encryption to Explorer
Like the Google toolbar? Then check out UltraBar, with more features & customizable search engines!
My really out-of-date homepage
Sonork-100.10414 AcidHelm

Re: The Explorer context menu

Nnamdi Onyeyiri6-Jun-02 22:48

Nnamdi Onyeyiri

6-Jun-02 22:48

I saw your tutorials soon after I made this thread. IT was just right for me, understood it ( 'cos its made for idiots Roll eyes | :rolleyes:

)

==================================================
Homepage: www.onyeyiri.co.uk
Email: theeclypse@hotmail.com
"I think Microsoft has invented A.I. My computer has a mind of its own!"

Re: The Explorer context menu

Nnamdi Onyeyiri6-Jun-02 22:55

Nnamdi Onyeyiri

6-Jun-02 22:55

Michael Dunn wrote:
Just released - RightClick-Encrypt - Adds fast & easy file encryption to Explorer

you know, i dont think you should be advertising your own software (shareware i might add) on codeproject, unless its one of those big banners, am i right?

==================================================
Homepage: www.onyeyiri.co.uk
Email: theeclypse@hotmail.com
"I think Microsoft has invented A.I. My computer has a mind of its own!"

Re: The Explorer context menu

Michael Dunn7-Jun-02 7:05

Michael Dunn

7-Jun-02 7:05

No, it's acceptable here to pimp your own stuff in your signature. Else I wouldn't be doing it.

--Mike--
Just released - RightClick-Encrypt - Adds fast & easy file encryption to Explorer
Like the Google toolbar? Then check out UltraBar, with more features & customizable search engines!
My really out-of-date homepage
Sonork-100.10414 AcidHelm

KeyDown with MFC and button

6-Jun-02 7:32

I can't find how can I use WM_ONKEYDOWN or WM_ONSYSKEYDOWN when I 've somme buttons on my
application. If I erase them, it workds perfectly, but either not...
If I have buttons, they take the input focus, and I can't find the way to keep the focus on my
window

Re: KeyDown with MFC and button

Nish Nishant6-Jun-02 7:45

Nish Nishant

6-Jun-02 7:45

I presume this is a dialog based application. Read this article where I have explained how to handle keystrokes in a dialog based MFC application. The basic issue here is that, focus will always be on a control. The dialog will never receive focus.

http://www.codeproject.com/useritems/pretransdialog01.asp

Regards
Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Buy it, read it and admire me Smile | :)

CFont GetLogFont problem

6-Jun-02 6:57

Hi people,

I'm trying to change the font used to draw in my view class, but there's something wrong. This is the code in my view's OnDraw handler:

CFont NewFont;
LOGFONT LogFont;
GetFont()->GetLogFont(&LogFont);
LogFont.lfWeight = FW_NORMAL;
NewFont.CreateFontIndirect(&LogFont);

I found this code in quite a few examples in forums, but the call to GetLogFont causes an assertion failure:

_AFXWIN_INLINE int CFont::GetLogFont(LOGFONT* pLogFont)
{ ASSERT(m_hObject != NULL);
return ::GetObject(m_hObject, sizeof(LOGFONT), pLogFont); }

I can't even figure out what the m_hObject is supposed to contain, let alone why it's NULL. Anyone have a clue?

Thanks a lot,

ren

Re: CFont GetLogFont problem

Roger Allen6-Jun-02 7:14

Roger Allen

6-Jun-02 7:14

The GetFont() call is returning NULL. This will normally only work if a call to SetFont() or WM_SETFONT message has already been done/sent to the window in question.

Roger Allen
Sonork 100.10016

If I had a quote, it would be a very good one.

E- Mail

6-Jun-02 6:35

How can I send an EMail from an MFC Project without DOC/VIEW Architecture and without MAPI messanging?

Re: E- Mail

C^hris L^osinger6-Jun-02 6:52

C^hris L^osinger

6-Jun-02 6:52

SMTP is an option. there is code here that will help.

-c

Cheap oil. It's worth it!

ISEffects - effects for images

What function is equavalent to CString::AllocSysString() ?

redeemer6-Jun-02 6:34

redeemer

6-Jun-02 6:34

If i can't use CString in my non-mfc app then how do i use the AllocSysString?

Thanks

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