need your suggestion for data expression - C / C++ / MFC Discussion Boards

Re: CStatic drawing interrupted... Worker, UI Threads????

Greg Ellis4-Jul-07 6:35

4-Jul-07 6:35

Basically I have two music files playing (video and/or audio) I am showing a scrolling waveform as the song is playing in realtime (using GDI). I need this waveform to always scroll. When loading a file into the second player while the first player is playing the scrolling waveform is being interrupted. I just need that waveform to always be scrolling.

So MFC always draws from the main thread no matter what? That's no good for me. Is my only option UI threads?

Re: CStatic drawing interrupted... Worker, UI Threads????

Matthew Faithfull4-Jul-07 6:55

Matthew Faithfull

4-Jul-07 6:55

If you're doing that sort of thing and you want it really smooth I'd consider DirectX/OpenGL or perhaps just doing everything except the drawing in lower priority background threads and relying on having enough hardware under the bonnet to keep up. Double buffering may be your friend aswell when it comes to getting smooth display updates. i.e. draw it all to an off screen Bitmap and then blit that to the screen in one go. With a bit of manipulation perhaps you could do the scrolling in the bitmap memory aswell without having to redraw the old parts of the waveform.
It's a while since I did much PC based MFC but I certainly wouldn't have recommended it for the sort of app your describing when I did. Having said that there may be other issues causing your problems. Are you using a cyclic or fixed buffer that doesn't do any heap allocation while in use to store your waveform? If not you're going to get horrible performance glitches from the memory allocator for example.
Are you maxing out your current hardware? If you check the performance monitor while your app is the only one running and it's flat out at 100% then either you've got some ineffecient code or you're trying to push your hardware beyond what it can achieve. Ultimately all such jolts and flickers are down to something being blocked either by synchronisation or a bandwidth limit somewhere. Unless something is resource stealing. In that regard watch out for the Quicktime tray icon app if you use DirectX it can steal the graphics card from you every few seconds and cause horrible jitter.

Nothing is exactly what it seems but everything with seems can be unpicked.

Re: CStatic drawing interrupted... Worker, UI Threads???? [modified]

Mark Salsbery4-Jul-07 7:08

Mark Salsbery

4-Jul-07 7:08

I don't agree that all drawing is done on one thread. Through WM_PAINT maybe, but if you're using
GDI to draw from another thread then it's drawing on that thread. I do video rendering and it's
definitely not on one UI thread Smile | :)

*edit* BTW, I've personally never used multiple UI threads - I meant multiple worker <br />
threads doing GDI drawing.

Try calling GDIFlush() when you're done drawing each time.

Also remember GDI is not thread safe - It's up to you to sync drawing from other threads with
drawing that may occur in response to WM_PAINT on the UI thread.

Mark

-- modified at 13:15 Wednesday 4th July, 2007

Mark Salsbery
Microsoft MVP - Visual C++

"Go that way, really fast. If something gets in your way, turn."

OnSize Assertion Error

sdancer754-Jul-07 5:11

sdancer75

4-Jul-07 5:11

Hi,

Using a CDialogBar:OnSize(UINT nType, int cx, int cy) I get assertion error when i am trying to access a child window ie CStatic control under OnSize method. In OnInitDialog it works fine but in the OnSize the hWnd is equal to ??? (unkown). What's wrong here ?

void CBottomPanel::OnSize(UINT nType, int cx, int cy)
{
CDialogBar::OnSize(nType, cx, cy);

// TODO: Add your message handler code here

CStatic *pStatic;
pStatic= (CStatic*) GetDlgItem(IDC_MYSTATIC);
-----> ASSERT(pStatic); ----------------------------->Assertion Error, not valid handle.

}

sdancer75

Re: OnSize Assertion Error

Arman S.4-Jul-07 5:19

Arman S.

4-Jul-07 5:19

On the first call [or so] to OnSize the child windows have not been created yet. In other words, their HWNDs are not valid. Perheps this is what causes the assertion failure. Try to have smth like so;

CStatic *pStatic;
pStatic= (CStatic*) GetDlgItem(IDC_MYSTATIC);
if (NULL != pStatic)
{
// do anything here
}

In this way you will skip the first time call to OnSize.

In general, using GetDlgItemis not a good idea. Instead, let the wizard define CStatic c_myStatic member-variable. In this case the code will turn into this one;

if (NULL != c_myStatic.GetSafeHwnd())
{
// do anything here
}

--
=====
Arman

Re: OnSize Assertion Error

sdancer754-Jul-07 22:56

sdancer75

4-Jul-07 22:56

Hi Arman,

I suppose you have right. I did not tested since i have changed my code and i placed all code to CalcDynamicLayout(int nLength, DWORD dwMode) and it works.

Thank you for your reply,

Regards,

sdancer75

Re: OnSize Assertion Error

Hamid_RT4-Jul-07 19:28

Hamid_RT

4-Jul-07 19:28

I agree with Arman maybe your error is of first call.

WhiteSky

need your suggestion for data expression

includeh104-Jul-07 4:56

includeh10

4-Jul-07 4:56

in my progarm (special to deal with data), i need good expressions for 2,4,8,16 based integers.

for example, in c++, we use 0x... to stand for 16 based data.

so, expressions i try to use are:

0b... (2 based)
0f... (4 based)
0o... (8 based)
0x... (16 based)

but i am afraid that expressions above are not good.
i hope i can use common or popular expressions.

do you know expressions which are accepted already by people for different based integers?

Re: need your suggestion for data expression

David Crow5-Jul-07 3:25

David Crow

5-Jul-07 3:25

Base-2 and base-8 numbers already have a known prefix. Why the change? What exactly are you trying to do?

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

writing to a port

lovneet4-Jul-07 4:40

lovneet

4-Jul-07 4:40

hey!
m working on a code where in i have to write to a board. the system and the board are connected via UART. m using VC++. the problem is that the moment i try to write a character the system hangs. here is a part of the code -

void CserialportthingieDlg::OnBnClickedWrite()
{
UpdateData(TRUE);
size_t size;
size = strlen(m_sshwwrite);//m_sshwwrite is he variable associated with the editbox
int i;
i=size-1;
asd->WriteByte(m_sshwwrite[i]);//asd is an instance of the class SerialCom where in i writebyte has been defined.

}

the definition of writebyte is --

BOOL CSerialCom::WriteByte(BYTE bybyte)
{
iBytesWritten=0;
if(WriteFile(hComm,&bybyte,1,&iBytesWritten,NULL)==0)
return false;
else
return true;
}

please let me know if any thing is wrong with the code or tell me a better way.
thanks a lot!

regards
lovy

Re: writing to a port

CPallini4-Jul-07 4:48

CPallini

4-Jul-07 4:48

How do you set the serial port timeouts (remember: WriteFile is a blocking call)?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Re: writing to a port

lovneet4-Jul-07 6:17

lovneet

4-Jul-07 6:17

actually i had set some arbit time out. Big Grin | :-D

now even when i restored it to the default value the system still hangs!
help me out!

thanks

regards
lovy

Re: writing to a port

CPallini4-Jul-07 9:07

CPallini

4-Jul-07 9:07

Post the relevant code (i.e. port open, DCB definition, etc..)
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Re: writing to a port

David Crow5-Jul-07 3:27

David Crow

5-Jul-07 3:27

If WriteFile() is failing, call GetLastError() to find out why.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: writing to a port

khan++5-Jul-07 3:49

khan++

5-Jul-07 3:49

May be you are setting the wrong kind of handshaking. If you are setting hardware handshake, unless the board on the other end sets the relevant lines in the port, the WriteFile will wait until the port timeout (if I remember it correctly).

There are variables in the DCB structure that need to be set for setting the handshake mode(None, Software, or Hardware).

Also you could check if the board is working by trying it with HyperTerminal first with the correct Handshaking.

this is this.

lower and higher part of a variable

Dobromir Dimitrov4-Jul-07 4:32

Dobromir Dimitrov

4-Jul-07 4:32

Hello. I am new to MFC and C++ in general. I am interested in how to get the lower and higher parts of a DWORD variable?

Re: lower and higher part of a variable

Matthew Faithfull4-Jul-07 4:40

Matthew Faithfull

4-Jul-07 4:40

I guess you're looking for the HIWORD and LOWORD macros. MSDN docs are here[^]

Nothing is exactly what it seems but everything with seems can be unpicked.

Re: lower and higher part of a variable

CPallini4-Jul-07 4:42

CPallini

4-Jul-07 4:42

Have a llot at LOWORD and similar macros on MSDN http://msdn2.microsoft.com/en-us/library/ms632659.aspx[^].
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Error sound when closing application

Twister3364-Jul-07 2:23

Twister336

4-Jul-07 2:23

After I switched from VS2003 to VS2005 the Windows error sound comes up when I close my application but there's no error message.

The only changes I made in the code are the ones required to make it VS2005 compatible.

Re: Error sound when closing application

Programm3r4-Jul-07 3:10

Programm3r

4-Jul-07 3:10

Are you sure there is no MessageBeep() in your code ?

Just guessing

Regards,

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

Programm3r
My Blog: ^_^

Re: Error sound when closing application

Mark Salsbery4-Jul-07 7:18

Mark Salsbery

4-Jul-07 7:18

That's Microsoft's way of making your application more multimedia robust!

Smile | :)

If you run in the debugger, do you see any exception/error/assert messages in the Output window
during shutdown?

Mark

Mark Salsbery
Microsoft MVP - Visual C++

"Go that way, really fast. If something gets in your way, turn."

Re: Error sound when closing application

Hamid_RT4-Jul-07 19:30

Hamid_RT

4-Jul-07 19:30

Can you more explain about your program?

WhiteSky

Re: Error sound when closing application

Twister3366-Jul-07 23:57

Twister336

6-Jul-07 23:57

I found the problem. It was a third party library which caused it.
I've got a new version of that library and now the problem is fixed.

Thanks everyone! Smile | :)

How to Reduce Desktop Size

vikrant kpr4-Jul-07 2:22

vikrant kpr

4-Jul-07 2:22

Hello Friends
I have seen few toolbars that reduce size of desktop window & locate them on the top.
Any idea how they do that?
In case i try GetDeskTopWindow & do a MoveSize it does not works?
Regards

Re: How to Reduce Desktop Size

Nibu babu thomas4-Jul-07 3:19

Nibu babu thomas

4-Jul-07 3:19

vikrant kpr wrote:
I have seen few toolbars that reduce size of desktop window & locate them on the top.
Any idea how they do that?

Look up SHAppBarMessage.

Nibu thomas
A Developer

Code must be written to be read, not by the compiler, but by another human being.

http:\\nibuthomas.wordpress.com

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