C / C++ / MFC

25-Jun-01 18:28

Hi,
What is performance this code ? What doing ?

void DoEvents()
{
MSG msg;
while(::PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE))
{
if(!AfxGetThread()->PumpMessage()) return;
}
}

My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html

Hadi Rezaie

Ben Burnett25-Jun-01 20:56

Ben Burnett

25-Jun-01 20:56

I think what it is doing is translating and dispatching all the messages that are in the current thread's message queue -- if there are any. I've seen something similar before; I think it was a trick used to update a dialog box's controls during a supper lengthy operation.

Sort of like this;

...
for ( int i = 0; i < 10000000000000000; ++i ) {
    wndListBox.AddString ( arrayOfWayToManyStrings[i] );    
    DoEvents ();
}
...

I'm not really sure if this is good practice or not... but if you find that your using it frequently, you might consider doing the UI processing in a separate thread.

Someone correct me if I'm wrong.

-Ben

---------
On the topic of code with no error handling -- It's not poor coding, it's "optimistic" Wink | ;)

Hadi Rezaee26-Jun-01 0:05

26-Jun-01 0:05

Thank you very much ... Smile | :)

I'm very very beginner in Thread programming, i mean i'm very beginner in using functions that work by Messages, if possible please write FULL for me about SendMessage and GetMessage and DispatchMessage and PostMessage and ... and explain about Thread, what mean Thread ? how can i use of it ? Dead | X|

Thanks again.

My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html

Hadi Rezaie

Ben Burnett26-Jun-01 10:20

Ben Burnett

26-Jun-01 10:20

Hey,

Hey,

I don’t think I can tell you any more than what MSDN would.

SendMessage - Sends a message to a specified window, and does not return until the window processes it.

PostMessage - places a message in the specified window's message queue, and returns immediately.

GetMessage - looks at the thread's message queue and waits till a posted message appears, all the while dispatching any incoming messages.

DispatchMessage - Dispatches a message to a window procedure, letting it take the appropriate action. All the message handlers you add to your application get called because of this function.

As for threads you’d be better of looking through MSDN or better yet a beginner book on the subject. The book that helped me out the most was ‘Beginning Windows NT Programming’ – by Julian Templeman… it has a great section on threads and processes.

-Ben

---------
On the topic of code with no error handling -- It's not poor coding, it's "optimistic" Wink | ;)

Hadi Rezaee26-Jun-01 19:55

26-Jun-01 19:55

Hi Ben,
Thanks alot for your helps, Smile | :)

I got very notices from your reply.
If i'll find any other question i ask you ... Wink | ;)

My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html

Hadi Rezaie

Hadi Rezaee27-Jun-01 19:51

27-Jun-01 19:51

Hi Mr.Ben,
Thanks alooot for your reply ... Smile | :)

You said DispatchMessage, dispatch message to a window procedure, i want to know does SendMessage and PostMessage don't dispatch message to a window precedure ?!!!
So, where does SendMessage or PostMessage, dispatch messages ?
And in last, what is different between PostMessage and PeekMessage ???

Thanks again ...
Best Regards

My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html

Hadi Rezaie

markkuk27-Jun-01 21:44

markkuk

27-Jun-01 21:44

SendMessage and PostMessage don't dispatch messages, they insert messages into a message queue. The thread that receives the message is responsible for dispatching the message.

PeekMessage checks if there are any incoming messages in the queue and always returns immediately, unlike GetMessage which blocks until a message is received.

Hadi Rezaee28-Jun-01 10:25

28-Jun-01 10:25

Thanks alooot, you really solved my problem ...

My month article: Game programming by DirectX by Lan Mader.
Please visit in: www.geocities.com/hadi_rezaie/index.html

Hadi Rezaie

Capture scrollable portion of a window

Carlos Antollini28-Jun-01 10:41

Carlos Antollini

28-Jun-01 10:41

Basically, that code permits that the system process another messages.
In other words, that permits that the system attends to other systems.
It causes that it lowers the resources of the CPU consumed by the Application. I use constantly that code, in my NT services.

Cheers!!!
Smile | :)

Carlos Antollini.

Dynamic controls

Farah Mansor25-Jun-01 16:28

Farah Mansor

25-Jun-01 16:28

How can I create dynamic controls? eg: I want to create an edit box or radio button based on what user input. If user want one edit box so I have to create one edit box. If two edit box, the application should have two edit boxes. Anyone know how to do it?

Thanks in advance. Smile | :)

FMansor

Timers accuracy

Brad Schroeder25-Jun-01 13:59

Brad Schroeder

25-Jun-01 13:59

I need to implement a system which times video spots for playout. For example, each spot will have a specified duration in a list of spots. Each spot should start after the previous one has finished.

I will worry about access time considerations, but I was wondering what the accuracy of a waitable timer or wait function is ( ie, would you trust it to do a real job for you? ).

Also, is it poor form to simply use WaitForSingleObject as follows ? :

CreateEvent( .........)
SetEvent( hEvent ) // Create a dummy event

for( i=spotListLength-1; i>=0; i-- ) {
Play( spot[i] ) // start playing spot[i] in its own thread somewhere else
WaitForSingleObject( hEvent, spot[i].duration ); // wait for timeout
}
// The loop is just for the sake of this question - Not used as is

Thank you,

Brad

Re: Timers accuracy

Carlos Antollini25-Jun-01 15:06

Carlos Antollini

25-Jun-01 15:06

Wait infinitly in the WaitForSingleObject() until WaitForSingleObject() != STILL_ACTIVE.
Put the WaitForSingleObject() into a loop, for ask about the value that it returns.
When the thread finished you will know that the sopt is finish.

Cheers!!!!
Smile | :)

Carlos Antollini.

Re: Timers accuracy

Brad Schroeder25-Jun-01 15:59

Brad Schroeder

25-Jun-01 15:59

Good point and thank you. However with past experience using events as above, the time from initiating the signal to the time the WaitFor.. acknowledges it is often indeterminant - it may or may not happen on time.

I guess I should have explained further that I am actually triggering a video server remotely and I don't want to wait for serial handshaking, etc. My question lead us to believe that I was running viz locally. Sorry Smile | :)

What I want to do timing-wise is to ever so slightly cut off the end of the previous clip and force a guaranteed start time for each - not really dependant on exactly when the previous one ends. My stipulation is that the entire block of spots takes up exactly X amount of time (+ or - some ?). This is why I need to get an accurate timing scheduler.

Thank you,

Brad

Re: Timers accuracy

markkuk25-Jun-01 20:24

markkuk

25-Jun-01 20:24

Basically, you can only trust that the timer will not be signalled before the specified time. Windows isn't a real-time OS, so don't expect it to work like one. However, the multimedia timers are supposed to give better accuracy than regular timer messages or WaitForSingleObject timeouts. See the documentaion for timeSetEvent(), TimeProc(), timeKillEvent() in the Graphics and Multimedia services of the Platform SDK docs.

BobMatura25-Jun-01 13:42

BobMatura

25-Jun-01 13:42

I'm trying to write a program which captures the scrollable portion of a window (Wordpad, Paint, IE, etc) and save it as one big bitmap. Actually making a window scroll down line by line isn't a problem but the difficulty I've been having is getting the scrollinfo from the window of concern. Applications seem to simply ignore the message SBM_GETSCROLLINFO and the API GetScrollInfo(...) plain doesn't work. So, unless I can get the scrollinfo, I never know how many times to scroll the window down and I also don't know how much of the window was scrolled down ( my plan is to scroll the window, make the image capture, append to "finished" image, and repeat to finished. If anybody can figure this one out I can pad your wallet with some cash.

Deleting files with invalid file names.

Franky Braem25-Jun-01 10:00

Franky Braem

25-Jun-01 10:00

While I was debugging a new version of SAWZip I create some files with invalid filenames. The filename was pointing to an invalid memory block. The name of the file looks like this &çàçàééjkl. Confused | :confused:

I tried to delete them with Explorer and with the command-box but they both say I'm trying to delete an invalid file. I also tried to delete the entire directory. But that doens't work either. Mad | :mad:

How can I get rid of them?

C^hris L^osinger25-Jun-01 10:15

C^hris L^osinger

25-Jun-01 10:15

did you try:

DeleteFile(pFilename);

?

------------------------------
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Franky Braem25-Jun-01 20:02

Franky Braem

25-Jun-01 20:02

The problem is that it's not possible to know what the name of the file is. Maybe I've to try findfirst, findnext, ... There are some files with only spaces in the name and I can't delete them either.

Michael Dunn25-Jun-01 10:25

Michael Dunn

25-Jun-01 10:25

Odd that the OS let you create such a file in the first place. I'd try running ScanDisk, Norton Disk Doctor, or whatever disk repair tool you have. Those should find the invalid filename and correct it.

--Mike--
http://home.inreach.com/mdunn/
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