Re: CStatic drawing interrupted... Worker, UI Threads???? - C / C++ / MFC Discussion Boards

tom groezer4-Jul-07 8:54

4-Jul-07 8:54

What are the best books to start knowing about data structures from a begineer point of view with emphasis on hands on rather than the theoritical aspect? Any help would be highly appreciated.

Re: C++ data structures

Maximilien4-Jul-07 9:06

Maximilien

4-Jul-07 9:06

you will need a little bit of theoretical aspect to get you going.

I suggest this book :

Introduction to Algorithms ( by Thomas H. Cormen (Author), Charles E. Leiserson (Author), Ronald L. Rivest (Author), Clifford Stein (Author))

http://www.amazon.com/Introduction-Algorithms-Thomas-H-Cormen/dp/0262032937/ref=pd_sim_b_1_img/002-3852795-0448009[^]

Maximilien Lincourt
Your Head A Splode - Strong Bad

Re: C++ data structures

David Crow5-Jul-07 3:15

David Crow

5-Jul-07 3:15

tom groezer wrote:
What are the best books

What's good for others may not be good for you, and vice versa.

What's wrong with this?

"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

CString::Replace Problem [modified]

lparsonson4-Jul-07 5:58

lparsonson

4-Jul-07 5:58

Hi all,

I'm trying to use the Replace function of the CString class, and it seems to be mostly fine, except it's ballsing up in one particular instance. I can't see what I'm doind different, but for some reason it doesn't like this:

CString PostCode;

m_PostCode.GetLine(0, PostCode.GetBuffer(m_PostCode.LineLength(0)), m_PostCode.LineLength(0));
PostCode.Replace("'", "''");

where m_PostCode is a member of the class this code is called from, being an instance of CEdit. I can't see anything that I'm doing differently to any other times I'm using the Replace function, but in this instance it just won't replace ' with ''.

Any ideas? I can't seem to find anything that suggests this is a known issue.

Thanks!

Louis.

Addendum:

I've noticed that it occurs with other CString/CEdit pairs like this, but if I copy the contents of the CString into a new CString, then run the Replace function of the new string it works fine. Am I missing something here?

-- modified at 12:05 Wednesday 4th July, 2007

Re: CString::Replace Problem

Mark Salsbery4-Jul-07 7:02

Mark Salsbery

4-Jul-07 7:02

Maybe try calling

PostCode.ReleaseBuffer(m_PostCode.LineLength(0));

before calling Replace()

Mark

Mark Salsbery
Microsoft MVP - Visual C++

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

Re: CString::Replace Problem

lparsonson5-Jul-07 4:54

lparsonson

5-Jul-07 4:54

Yes, this worked like a charm!

Thanks a lot Mark, very speedy response!

Louis.

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

Greg Ellis4-Jul-07 5:41

Greg Ellis

4-Jul-07 5:41

Hey Guys,

I have an MFC CStatic derived class that has a public member function Draw();. Draw uses GDI to draw stuff to the CStatic window. I call this Draw method from a multimedia timer (timeSetEvent) to continually update the display.

My problems is that When my main app is doing a lot of work the drawing is sometimes interrupted when I load files. So I put the lengthy process of loading files in a worker thread, but the drawing is still "jerky" when loading a file. Is there anything else I can do to ensure that my CStatic is always drawing? Is this something I need a user interface thread for?

Thanks,
Greg

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

Matthew Faithfull4-Jul-07 6:27

Matthew Faithfull

4-Jul-07 6:27

I'm not certain what you're trying to achieve here as genuinely constant redrawing would preclude you doing anything else anyway but you may have run up against a perenial problem with the MFC architecture. Essentailly anything done to the user interface is done on the main thread even if you call it from a worker thread. I would definitely suggest doing the file loading on a worker thread before getting into the absolute minefield of multiple user interface threads.

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

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

Greg Ellis4-Jul-07 6:35

Greg Ellis

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.

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