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CharlieG wrote: I understand WHY you don't do UI stuff in the worker threads, but I have a situation where I work that we seem to defy that logic.
Does it actually work or does it just appear to work?
CharlieG wrote: The view should be owned by the main application thread - a UI thread - accessing the object just seems like the end of the world should occur.
I believe the operative word is could.
"Take only what you need and leave the land as you found it." - Native American Proverb
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David,
In this case, yes  . It appears to and does work - basically, we update a progress bar when this happens.
Could/should - true. Your comment seems to imply we got lucky.
C. Gilley
Will program for food...
My son's PDA is an M249 SAW.
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As long as you don't rely on the one-to-one map of HWND and CWnd objects...
My blogs:
http://blog.joycode.com/jiangsheng
http://blog.csdn.net/jiangsheng
http://bloglines.com/public/jiangsheng
Command what is yours
Conquer what is not
---Kane
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Sheng,
I'm not that deep in Windows yet - can you elaborate?
C. Gilley
Will program for food...
My son's PDA is an M249 SAW.
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MFC maintains a 1-1 map between handles and objects that is local to each thread, and some functions, such as CWnd::AssertValid and CWnd::GetParentFrame, acturally rely on an assumption that it is not called from another thread, so the object can be retrived from the map by looking for the handle.
ref.
thread states in MSDN TN058
MTMDI: Demonstrates an MFC User Interface Thread (Visual C++ Samples)
http://www.mvps.org/vcfaq/mfc/11.htm[^]
My blogs:
http://blog.joycode.com/jiangsheng
http://blog.csdn.net/jiangsheng
http://bloglines.com/public/jiangsheng
Command what is yours
Conquer what is not
---Kane
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Hi,
I'm programming a library. It must be thread-safe, so I've a global critical section variable to synchronize the calls among the different calling threads. I also want to offer the possibility to link it against the client as a static library or as a dynamic library. The problem is that InitializeCriticalSection doesn't support multi-threading, in the sense that if it's called from more than one thread with the same CRITICAL_SECTION object, it's result it's undefined. There's no problem in the case that the client is linking with the dynamic library, because I know that DllMain is called just by one thread.
The problem is that, in case it's linked as a static library, I'm forced to 1) write an init() function that should be called by the client (only once) to initialize the critical section: the problem is that the client could forget to call it...or could call it from more than one thread simultaniously (and I can't protect init() since I don't have any critical sections yet) 2) create a static object that in its constructor it initializes the critical section: according to the c++ standard we don't know what will be the static object initialization order amongst different modules...so I can receive a call from the client before initializing the critical section...
If anybody has any suggestion, please let me know
Thanks,
Federico
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Federico Milano wrote: the problem is that the client could forget to call it
So could all of your functions test for this, and return a "you need to call init first" error message? I don't see that as a problem. There's loads of Windows API calls where you need to call Function1 before you can validly call Function2.
Federico Milano wrote: or could call it from more than one thread simultaniously
Are you saying that you'll get two, simultaneous calls to DllMain with a dwReason of DLL_PROCESS_ATTACH?
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Graham Bradshaw wrote: Are you saying that you'll get two, simultaneous calls to DllMain with a dwReason of DLL_PROCESS_ATTACH?
No, I'm saying that if you need a client to call init(), init() could be called from multiple threads simultaneously. You can't enforce this by soft, I think.
I know that DllMain is called only once with a dwReason of DLL_PROCESS_ATTACH for a process that loads that dll, but what if I want to link my library statically? DllMain will not be called and I can't use static objects (because of initialization order issues) and the init() method is unsafe, what should I do?
Of course I can solve this with the DllMain thing, not linking statically, but I wanted something more OS independent...
Thanks,
Federico
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Don't allow the client to call your software during image load and use a RAII static critical section. This can be a verbal contract that isn't enforced in software.
Having things happen during image load is a really bad idea and leads to the types of problems you are having to deal with. If you just have to have things happen on image load via constructors, the constructors should never refrence another C++ object and only reference POD objects.
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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This might be a dumb question, but would a static local (not member) variable in the init() function work? It would be initialzed to zero at first entry into the function, and you could check/increment the value using InterlockedCompareExchange() to see if initialization has taken place or not. You could use two variables, one to enter initialization of the Critical Section, and another to indicate that the CS was initialized. That might prevent two threads from racing on initialization of the CS and entering it - if one thread fails the first InterlockedCompareExchange() call, the second would confirm that the CS is initialized and ready for use.
I am not certain, but I think that initialization of a function-local static variable is thread-safe. But I could be wrong. Either way, the use of InterlockedCompareExchange() is thread-safe and that might work for you.
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!
Tip for new SUV drivers: 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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Hi all,
After using the navigate method to open a webpage, i want to lock the content of the webpage (user can't do anything in the view like right mouse clicking, copying text...) just can scroll the web page. I tried using the EnableWindow method but it disabled both the view and the scroll bar ( i don't want disable the scrollbar). Do you have any solution for this case ?
thanks,
Ken
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You can IThumbnailCapture to capture a snapshot...
My blogs:
http://blog.joycode.com/jiangsheng
http://blog.csdn.net/jiangsheng
http://bloglines.com/public/jiangsheng
Command what is yours
Conquer what is not
---Kane
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How to get CBitmap from CImageList?
I tried CImageList::GetImageInfo, but can't get it correctly.
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followait wrote: can't get it correctly
It should work, though.CAn you post your code ? What goes wrong ? Does the function return 0, or is the bitmap handle invalid ?
~RaGE();
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all the test code is in the button click msg handler
void CTest_CImgaeListDlg::OnButton1()
{
CClientDC dc(this);
//create a CBitmap, a simple rect, (0,0,10,10)
CBitmap bmp;
bmp.CreateCompatibleBitmap(&dc,16,16);
CDC dcMem;
dcMem.CreateCompatibleDC(&dc);
CBitmap *pOldBmp=dcMem.SelectObject(&bmp);
dcMem.Rectangle(0,0,10,10);
dcMem.SelectObject(pOldBmp);
//save it in iml, and get it immediately, but there is something worng
CImageList iml;
iml.Create(16,16,ILC_COLOR24,5,5);
int idx=iml.Add(&bmp,RGB(0,0,0));
IMAGEINFO ii;
iml.GetImageInfo(idx,&ii);
CBitmap *pBmp=CBitmap::FromHandle(ii.hbmImage);
pOldBmp=dcMem.SelectObject(pBmp);
dc.BitBlt(0,0,16,16,&dcMem,0,0,SRCCOPY);
dcMem.SelectObject(pOldBmp);
}
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This will not help you much, but this code works perfectly on my machine.
~RaGE();
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bolia its possible to call javascript from an applet. but i'm not sure with active-x 
He is like a one-legged man in a bum kicking competition. -Novjot Sidhu
--[v]--
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JIANG, Sheng[MVP] wrote: http://support.microsoft.com/support/kb/articles/Q172/7/63.ASP[^]
Hello Sir,
Above link is not working ! thanks
"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
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This link works fine on my computer.
My blogs:
http://blog.joycode.com/jiangsheng
http://blog.csdn.net/jiangsheng
http://bloglines.com/public/jiangsheng
Command what is yours
Conquer what is not
---Kane
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Does C++ have an API that gets the type of an object. I want to determine an object type during run time. Say for example, i have an object x ( which is of type CDialog), then i want to determine its type during run time. Thanks in advance!
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Hava a look on CRuntimeClass, CObject classes in the help. I think they are what you are looking for.
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typeid Operator
C++ Specific —>
typeid( type-id )
typeid( expression )
The typeid operator allows the type of an object to be determined at run-time.
The result of a typeid expression is a const type_info&. The value is a reference to a type_info object that represents either the type-id or the type of the expression, depending on which form of typeid is used. See type_info Class for more information.
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Try:
CDialog dlg;
if (dlg.IsKindOf(RUNTIME_CLASS(CDialog)))
...
"Take only what you need and leave the land as you found it." - Native American Proverb
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