Re: PaintDesktop - C / C++ / MFC Discussion Boards

Stuart Dootson15-Jul-09 12:24

15-Jul-09 12:24

a=0 is assignment. You probably wanted a==0 (two = signs), which is hte equality test.

One of the things that's nice (when you're experienced), yet horrible (when you're learning) about C and C++ is that assignment is an expression, not a statement, which means that you can do what you've done there.

In other languages like Ada, which class assignment as a statement, you couldn't make that mistake.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: why it prints 3?

sam_psycho15-Jul-09 15:25

sam_psycho

15-Jul-09 15:25

but if your are assigning any thing to any variable(in our case a=0), this statement suppose to a true, and a=1 does, but what is wrong with zero?

Re: why it prints 3?

«_Superman_»15-Jul-09 17:03

«_Superman_»

15-Jul-09 17:03

In C (and C++) 0 equates to false and non-zero equates to true.

The case that you mentioned is similar to

int a = 0;
if (a)
{
   b = 2;
}
else
{
   b = 3;
}

Since a is 0, this equates to if(0) or if(false).
So the else part will be executed.

But in the following snippet, the if part will be executed.

int a = -1;
if (a)
{
   b = 2;
}
else
{
   b = 3;
}

«_Superman_»
I love work. It gives me something to do between weekends.

Re: why it prints 3?

harold aptroot15-Jul-09 18:43

harold aptroot

15-Jul-09 18:43

The result of assignment is the value that was assigned to the lvalue, not some sort of status flag indicating that the assignment succeeded. The result of a=x is x, thus a=0 equals 0.

Re: why it prints 3?

David Crow16-Jul-09 2:59

David Crow

16-Jul-09 2:59

VCD_A wrote:
but if your are assigning any thing to any variable(in our case a=0), this statement suppose to a true...

So what would you propose the value of a and b to be in the following:

int a, b, c;
a = b = c = 5;

Hint: it's not 1.

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

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PaintDesktop

daavena15-Jul-09 9:45

daavena

15-Jul-09 9:45

Hello,

I want to obtain desktop background, so I would like to use PaintDesktop(hdc) function;

SDK says:
The PaintDesktop function fills the clipping region in the specified device context with the desktop pattern or wallpaper

HRGN hReg = CreateRectRgn(0,0,10,10);
HDC hdcD = GetWindowDC(GetDesktopWindow());
hdc = CreateCompatibleDC(hdcD);
SelectObject(hdc,hReg);

bResult = PaintDesktop(hdc);

But PaintDesktop function always returns false.

What am I doning wrong? Could you give me a hint.

Thank you.

Re: PaintDesktop

CPallini15-Jul-09 10:19

CPallini

15-Jul-09 10:19

Why don't you call GetLastError on PaintDesktop failure?
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.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: PaintDesktop

Sauce!21-Jul-09 6:19

Sauce!

21-Jul-09 6:19

or if you're lazy, add @err,hr to your watch window Smile | :)

Bufferring PAckets

resolvequestion15-Jul-09 9:11

resolvequestion

15-Jul-09 9:11

Can anyone help me with example code where u can use (vector, queue, dequeue , map techniques)

Thanks Stuart Dootson &; Superman !

I will be receiving certain amount of packets but I am not sure exactly how much. There will no memory problem as certainly its being taken under consideration that the received packets will be at certain limit it will not exceed.

whats the difference between using vector versus dequeue or queue technique.

I am explaining my scenario . I have reader thread that will do blocking read and once it receives the first packet which will be of 20W with 1W header with it.. I need to calculate checksum of the 20W packet received. Than I need to read certain fields and need to decide where it needs to be buffered. Before buffering these packets I need to strip off the 1W header. Once the buffering is complete say I might receieve 500 packets of size 20Word. After I stop receving the packets. I need to analyze the packets that being buffered. And these packets are of 2 types theere might be 2W packet and 260W packet or partial packet and each of these packet will have header so. first I need to read the packet header of the first received packet inthe buffer and base don that I need to dispatch those packets to its destined location or hand over to the designated handler.

So confusion is whats the best efficient technique I should use. Using simple array is not best option so thought of asking here. Also how do Istrip off the header from the packet.

Any help woul dbe appreciated. I have just started coding but have not really much coded in C++ .. I am learning by dng google or reading previos discussion here on forum

THANKS!!!!

Re: Bufferring PAckets

Randor 15-Jul-09 11:31

Randor

15-Jul-09 11:31

You should probably use deque. In my opinion it would be best suited for your application requirments. A Microsoft sample of deque:

INFO: STL Sample for deque::push_back and deque::pop_back Functions[^]

A in-depth deque analysis by a codeproject member:

An In-Depth Study of the STL Deque Container[^]

resolvequestion wrote:
whats the difference between using vector versus dequeue or queue technique

This is not really the type of information that is obtained through a forum. You should probably invest a few hours and research the difference between the STL containers. Here is a good place to start:

STL Container Comparison[^]

STL Containers[^]

resolvequestion wrote:
Also how do I strip off the header from the packet.

//I believe you state that the header is the size of 1 WORD
WORD packet_buffer[20]; //The first element of the array is indexed of 0
WORD packet_head = packet_buffer[0]; //Assign packet_header the value of WORD at index zero
WORD *piStripped = &packet_buffer[1]; //Pointer to WORD at index 1 of zero based WORD array.
BYTE *pbStripped = (BYTE *)&packet_buffer[1]; //Pointer to BYTE at index 1 of zero based WORD array.

resolvequestion wrote:
Any help woul dbe appreciated. I have just started coding but have not really much coded in C+

Excellent, in my opinion codeproject is the best programming resource on the internet.

Good luck,
-David Delaune

Re: Bufferring PAckets

«_Superman_»15-Jul-09 17:15

«_Superman_»

15-Jul-09 17:15

resolvequestion wrote:
whats the difference between using vector versus dequeue or queue technique

Each of the STL containers are optimized for certain types of operations.
Read more about it here - STL Containers[^]

For example, vector is optimized for random access to any of its elements.
A deque is optimized for insertions and removal of elements at both its ends.

As suggested by Stuart in your earlier post, a deque will be perfect for your needs.

«_Superman_»
I love work. It gives me something to do between weekends.

wavelet transform c++ program

mrby12315-Jul-09 8:34

mrby123

15-Jul-09 8:34

Dear friends,

I am looking for C++ programs of wavelet transform for seismic waves. Although, I can do wavelet transform with Matcad, I like to get an independent program.

Thanks

Yours

Re: wavelet transform c++ program

CPallini15-Jul-09 9:34

CPallini

15-Jul-09 9:34

Have you already looked at this page [^]?
Smile | :)

Re: wavelet transform c++ program

mrby12315-Jul-09 9:47

mrby123

15-Jul-09 9:47

Thank you. I will give a try. This one seems for image processing, I hope it will work for seismic waves.

Re: wavelet transform c++ program

mrby12315-Jul-09 10:17

mrby123

15-Jul-09 10:17

I wish to get the project files and link and run it.
Please advise.

Re: wavelet transform c++ program

Rick York15-Jul-09 10:26

Rick York

15-Jul-09 10:26

I guess I have a keen sense for the obvious but I would try the download link(s) on the page he linked to.

Re: wavelet transform c++ program

mrby12315-Jul-09 18:20

mrby123

15-Jul-09 18:20

The download does not include a project file. So I still do not know how to compile those library files into a project.
I need to process seismic waves from geophysics survey.

Please help

Thanks

Non-template based common data structure?

crewchill15-Jul-09 6:37

crewchill

15-Jul-09 6:37

Hi folks,

I'm looking for non-template based library that provides common data structures (queue, vector, etc). The non-template part is crucial since I'm doing embedded system and I need the code to be portable to older EC++ compilers.

Ideas? Commercial or non-commercial suggestions accepted!

Thanks in advance!

Re: Non-template based common data structure?

Stuart Dootson15-Jul-09 8:23

Stuart Dootson

15-Jul-09 8:23

A C generic container library is probably what you're looking for. This StackOverflow page[^] seems relevant?

Similarly, this page[^] describes generic containers in C.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Visual c++ 6 doesn't show variables

mariano_7615-Jul-09 6:07

mariano_76

15-Jul-09 6:07

Hi all,

i have a big annoying problem with visual studio 6:
in my projects when i go in debug mode i cannot see the value of some variables in watch window,
simply they appear uninitialized or empty, but i know they are initialized!
i.e. if i want to see the value inside variable Y i have to write the following code:

int x=Y;

only in this way i can see the x variable in watch window with its value...

i have formatted my PC but cannot solve yet this problem...

anybody knows this kind of problems?

i hope i've explained enough...

Thanks to all in advance...

Re: Visual c++ 6 doesn't show variables

Stuart Dootson15-Jul-09 6:28

Stuart Dootson

15-Jul-09 6:28

Are you actually using the Debug configuration build? Because the symptoms you describe sound just like trying to debug a Release configuration build with optimisations turned on...

But then the compiler would optimise away the assignment of Y to x as ineffective. Hmmm.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: Visual c++ 6 doesn't show variables

mariano_7615-Jul-09 21:53

mariano_76

15-Jul-09 21:53

yes i'm in debug mode...
i just cannot find any mention of this kind of problem around the web...

i'm using an AMD Athlon 64 x2 4800+ with 2GB of RAM and Win XP SP3

Re: Visual c++ 6 doesn't show variables

Stuart Dootson15-Jul-09 21:57

Stuart Dootson

15-Jul-09 21:57

You might like to try Windbg[^] for debugging, see if that gives better results?

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: Visual c++ 6 doesn't show variables

Iain Clarke, Warrior Programmer15-Jul-09 7:31

Iain Clarke, Warrior Programmer

15-Jul-09 7:31

I've also found VC6 terrible at watching global variables...

Also, deleting the ncb file helps a lot with almost everything!

Iain.

I have now moved to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), or need cotract work done, give me a job! http://cv.imcsoft.co.uk/[^]

Re: Visual c++ 6 doesn't show variables

Joe Woodbury15-Jul-09 20:09

Joe Woodbury

15-Jul-09 20:09

Verify whether you are watching "Auto", "Locals" or "this".

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