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I am using Visual c++ PLease
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Supposing you have an MFC application, I think you have to handle the WM_ERASEBKGND notification. Add a handler for this message in your frame class. Within the handler you will have a CDC object as a parameter. Use drawing functions to fill the frame with colour you prefer.
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I don't see this handle : WM_ERASEBKGND
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you can use WM_PAINT and use CPaintDC dc(this);
whitesky
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Hi,
I m using Windows Timers in my application which has 4 threads. I need a separate timer for each thread. At most how many timers can I use in an application as in future I will update my application for 32 threads? Regards
Cyber Friend
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Cyber Friend wrote: At most how many timers can I use in an application as in future I will update my application for 32 threads?
I'm not exactly sure. In any case, they are a limited resource. Check SetTimer()'s return value.
"The largest fire starts but with the smallest spark." - David Crow
"Judge not by the eye but by the heart." - Native American Proverb
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The Following link have more about Timers which may resolve your problem for creating timers and limit for creating them.
Timers[^]
Knock out 't' from can't,
You can if you think you can
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Windows resources are very precious. I recall one of the old applications in which the developer used around 20 timers, each to refresh different portion of the display. The refresh rate is 10-20 Hz. Whenever that program is run, it used up all 100% CPU. Of ocourse, the 20 timers have been later combined to one centralized, high-resolution timer.
In general, 4 threads should be fine, but I have concerns about 32 threads. The number does matter. Not just the number of timers, but also the number of thredas. Each thread (and timer) takes a lot of overheads. I don't know of your situation, but you might want to think again about the design.
- It's easier to make than to correct a mistake.
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Hi,
Thanx for the repies from all of u.
Jun Du wrote: Whenever that program is run, it used up all 100% CPU. Of ocourse, the 20 timers have been later combined to one centralized, high-resolution timer.
Jun I m using timers first time in an application and dont know much about them. Can you plz mention the link of some article/tutorial about the usage of a "High-resolution timer", instead of so many timers.
Regards.
Cyber Friend
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Search CodeProject for "multimedia timer".
- It's easier to make than to correct a mistake.
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Hi,
Can I use one Central High-resolution Timer for all of my threads
(32 threads in future and currently 4).
Best Regards
Cyber Friend
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IN a Dialog I have two CButton when i clicked on first button a loop starts. The requirement is when i click on second button it should break the loop. How i can communicate this to the loop. I tried Sleep so that i can check the status of common variable. But this variable is updatted only when the loop terminates. What will be the possible solution of my Problem.
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Read up on threads here and here.
anilksingh wrote: I tried Sleep...
Using Sleep() with threads is usually a bad idea.
"The largest fire starts but with the smallest spark." - David Crow
"Judge not by the eye but by the heart." - Native American Proverb
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one thing that you can do is that create a static flag=false as a global variable.
now in the loop you can check that if the flag is set to true.
(You will set the flag to true when the second button is pressed.)
if the flag is set simply put return 0; in the block of code where you want the thread function to end.
Here's some code for you that is inside the thread function :
CMyDlg *test=(CMyDlg *)pVoid;
for(int i=0;i<1000;i++)
{
Sleep(10);
if(flag==true)
{
CString s;
s.Format ("%d",i);
AfxMessageBox("Thread stoping on "+ s);
return 0;
}
else
{
CString s;
s.Format ("%d",i);
test->m_number.SetWindowText (s);
}
}
return 0;
Somethings seem HARD to do, until we know how to do them.
_AnShUmAn_
-- modified at 9:34 Tuesday 13th June, 2006
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put the shared resource in crtical section (global varaible)dont use sleep
never say die
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It was just to show the user. Afterall this was not a live example.
It was just to give the user the time to perform the inputs while the thread is running
Somethings seem HARD to do, until we know how to do them.
_AnShUmAn_
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The old way (Win16) of doing this was to pump messages in the loop so that the other button will respond to user input. Today, a worker thread would be what I would suggest.
Look up how to create a background thread using the links provided in the previous answer. While you can use a shared variable to terminate the thread, I would suggest looking into how "event" objects work with threads to get a feel for them and how they should be used.
Peace!
-=- James
If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
Avoid driving a vehicle taller than you and remember that Professional Driver on Closed Course does not mean your Dumb Ass on a Public Road!
DeleteFXPFiles & CheckFavorites (Please rate this post!)
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Create an event handle (using CreateEvent). Pass that handle to the loop when you create it (its quite common to pass such objects in the LPARAM pointer used when creating a thread). When you need to terminate the thread, call SetEvent. Internally to the loop, you will use WaitForSingleObject with an appropriate timeout value (in your case, 0 would probably work since you just want to check to make sure it has already been set). If WaitForSingleObject returns WAIT_OBJECT_0, then your event was signaled and you should stop the loop.
Alternatively, you could create a boolean flag and put a critical section around every access. This works just as well, but is error prone (one access without a critical section breaks the entire system). The Event solution doesn't have that problem.
If you use Sleep in any application, you can pretty much be assured that your design is flawed. Using it in Multithreaded applications to try to manage synchronization between threads is worse than useless. Use proper thread synchronization techniques and you won't have issues.
If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week
Zac
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Zac Howland wrote: Alternatively, you could create a boolean flag and put a critical section around every access. This works just as well, but is error prone (one access without a critical section breaks the entire system). The Event solution doesn't have that problem.
You can also go the shared variable route and use things like InterlockedCompareExchange(...) (CMPXCHG) as well. One thing though - for this particular kind of situation, I am not sure that synchronized access is required. Since the value is not being used as a counter, or anything like that but just a simple flag, it should be OK to have one thread reading it waiting for its value to change while another threads writes it (once) to set that value. I do not think that the reading of the value will interfere with the writing of it, and the thread would catch the change on the next read. (Assuming automatic volatile handling and things like that.)
And yes, that was my 5.
Peace!
-=- James
If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
Avoid driving a vehicle taller than you and remember that Professional Driver on Closed Course does not mean your Dumb Ass on a Public Road!
DeleteFXPFiles & CheckFavorites (Please rate this post!)
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As your thread title says, you should go for multithreading rather than the sleeping business. But what's the nature of the loop? can it be done with a Timer? I used to create threads unnecessarily when it could be done with timers  . So see to that it cannot be done with a timer first then go for multithreading. As said by David, never get your Sleep inside your thread or any loop, it puts the entire application to sleep 
<marquee scrollamount="1" scrolldelay="1" direction="up" height="10" step="1">--[![Jig | [Dance]](https://www.codeproject.com/script/Forums/Images/jig.gif) ]--
[My Current Status]
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(Assuming you are talking about Sleep(...)...)
VuNic wrote: As said by David, never get your Sleep inside your thread or any loop, it puts the entire application to sleep
No, it just the thread it is called on... An application may consist of multiple threads. Sleep(...) only affects one particular thread.
Peace!
-=- James
If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
Avoid driving a vehicle taller than you and remember that Professional Driver on Closed Course does not mean your Dumb Ass on a Public Road!
DeleteFXPFiles & CheckFavorites (Please rate this post!)
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Thanks james, I thought Sleep is global call. hmm.. thanks for the info.. nice update for me.
<marquee scrollamount="1" scrolldelay="1" direction="up" height="10" step="1">--[ ]--
[My Current Status]
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Hi all,
i want to change the color of a button when the cursor comes into contact with it...can anyone help me out in this???
Thanks in advance..
Rajeev
-- modified at 9:09 Tuesday 13th June, 2006
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rajeev82 wrote: Hi all,
i want to change the color of a button when the cursor comes into contact with it...can anyone help me out in this???
Here[^] is the good article on Bitmap buttons
Knock out 't' from can't,
You can if you think you can
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assume that I have some project that can support hot key and this project is running.Then I open another program for doing something.
While I'm using this program the first program will can't use hots key because now the focus is on the program that I'm using it.
If I want to make it always support hot key although I use another program.
How I do for this case?
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