Re: Threading problem.. - C / C++ / MFC Discussion Boards

David Fleming2-Sep-05 14:00

2-Sep-05 14:00

I've been looking around in the articles on CStatics as well as in stuff on Bitmaps and the GDI, but I'm not quite finding what I need, so here goes....

What I would like to create is a CStatic-derived class that will make what looks like a partially transparent CStatic. Think of it as a piece of colored glass with text written on it, hovering over the background.

I can handle making a CStatic transparent (there are a couple of nifty articles on that). In essence, taking an image of the part of the parent control behind the CStatic and painting that as the background of the CStatic.

To be more explicit, here's a code snippet for doing basic transparent CStatic:
This is in OnPaint for the CStatic-derived class (so dc is the supplied DC):

CDC* pdcT;
pdcT = new CDC;
pdcT->CreateCompatibleDC(&dc);
CBitmap bitmap;
CBitmap* pOldBitmap;
pOldBitmap = pdcT->SelectObject(&bitmap);
dc.BitBlt(0, 0, rc.Width(), rc.Height(), pdcT, 0, 0, SRCCOPY);
pdcT->SelectObject(pOldBitmap);
delete pdcT;

So what I need to be able to do is modify that "parent" image to add a wash of color, then paint that to the background of the CStatic. It seems that I need to do the modifying of the bitmap after it has been selected into the pdcT, but I don't know where to go on that. Or perhaps I'm missing something that I can do in the BitBlt function to accomplish this.

Can it be done? And if so, how?

Thanks.

Re: Creating a colored, transparent CStatic

David Fleming2-Sep-05 22:59

David Fleming

2-Sep-05 22:59

OK, it looks like I solved my own problem. Just in case anyone else is interested, here's what I found:

CPaintDC dc(this); //get a DC for the control
//The next several lines create a compatible bitmap in memory
// and draw a solid light green "bitmap" on it,
// then select that bitmap into the DC in memory
pDCMem = new CDC;
pDCMem->CreateCompatibleDC(&dc);
bmp.CreateCompatibleBitmap(&dc,rc.Width(),rc.Height());
pOldBitmap = pDCMem->SelectObject(&bmp);
CBrush brush;
brush.CreateSolidBrush(RGB(122,255,122));
pDCMem->FillRect(rc, &brush);
//After drawing on the DC in memory (text and whatever else)
// use BitBlt to merge the bitmap in memory with what's on screen
dc.BitBlt(0,0,rc.Width(),rc.Height(),pDCMem,0,0,SRCAND);
//SRCAND combines the src and dest DCs using boolean AND
//Then clean up
pDCMem->SelectObject ( pOldBitmap ) ;
delete pDCMem;

And it works. Now the CStatic is light green, with text on it (which I did not include in the code snippet) and the bitmap "behind" it can be seen greenishly colored through it.

Absent Thread

Blake Miller2-Sep-05 10:53

Blake Miller

2-Sep-05 10:53

Trying to debug a hung application.

Determined that the thread which owns the LdrpLoaderLock is no longer alive, but 4 of my 15 threads are waiting to gain this orphaned critical section.

Any suggestions how to catch this?

Possibly hijack EndThread and make sure thread does not own the critical sections? Possibly hijack TerminateThread as well?

Re: Absent Thread

Gary R. Wheeler3-Sep-05 2:36

Gary R. Wheeler

3-Sep-05 2:36

In my experience, this kind of thing happens when a thread exits due to an uncaught exception. Try putting a try { ... } catch(...) { } block around the entire thread, and then place a breakpoint in the catch block.

Software Zen: delete this;

What do employers mean by .Net experience

Brian R2-Sep-05 9:31

Brian R

2-Sep-05 9:31

I was wondering if anyone in here could explain what it means when a job description specifies .Net experience? Does that imply a specific version of compiler, language? Specific SDK experience?

Re: What do employers mean by .Net experience

C^hris L^osinger2-Sep-05 10:43

C^hris L^osinger

2-Sep-05 10:43

probably the .Net framework and its way of handling web page creation/interaction. if they don't specify a language, it's safe to assume either VB or C# (XOR or OR) - haven't seen many jobs for MC++ or J#.

Cleek | Image Toolkits | Thumbnail maker

Threading problem..

Laing,James2-Sep-05 8:42

Laing,James

2-Sep-05 8:42

I have a WIN32 application that creates and dispatches a number of threads that perform various tasks.
Now, one of the threads in particular creates and dispatches another two threads; one which reads records into a list <cstring> and one which writes the records from the list to an output.

The threads are created by a call to AfxBeginThread(), specifying the name of the function that serves as the worker thread (not a member function), and the argument to the call is the 'this' pointer of the parent object creating the thread (Both workers need access to the member functions of their parent).

When the number of lines to read and subsequentailly write, is small, ie) one or two. I get a really strange thread protection expception.

1. The parent dispatches the first thread; the reader. It starts right away.
2. The parent dispatches the second thread; the writer. It starts right away.
3. The parent thread then hits a WaitForMultipleObjects(), waiting for an event to be signalled by
both child threads indicating that they are complete.
4. The wait is broken, the parent object goes through destruction and completes.
5. Protection exception.

Thrdcore.cpp @ line 114 (in my listing).

nResult = (*pThread->m_pfnThreadProc)(pThread->m_pThreadParams);

I cannot for the life of me find out what the problem is. It is as if a thread is being dispatched
again after the parent is complete, or there is some kind of thread-clean-up that expects the function pointed to by pThread->m_pfnThreadProc and its argument pThread->m_pThreadParams (which is the address of the parent object) to be still accessible. Which of course it cannot be as the parent object has already been destroyed.

I have traced the process over and over and I cannot come up with a reason why this is happening.
If anyone has any suggestions or pointers I would would very much appreciate them.

James.

Re: Threading problem..

Gary R. Wheeler3-Sep-05 2:43

Gary R. Wheeler

3-Sep-05 2:43

In step 3, you indicate that your parent thread waits for an object signalled by both threads that indicates that they are complete. The problem is, when each thread signals the event, they are still executing. Signaling the event causes the thread to pause its execution in favor of the thread waiting. If you delete the parent object at this point, and then the reader/writer threads continue, you will see the access violation.

You need to wait for both threads to finish executing before deleting the parent object. You can do this using ::WaitForMultipleObjects, passing it an array containing the handles to the reader and writer threads.

Software Zen: delete this;

Re: Threading problem..

Laing,James3-Sep-05 7:27

Laing,James

3-Sep-05 7:27

Thanks for the update.
That is spot on...

The parent does wait with a WaitForMultipleObjects, but, I stupidly I coded the process to use CEvents instead of just using the HANDLE of each thread as the signal.

Again. Many thanks..
James.

:: operator

celllllllll2-Sep-05 7:47

celllllllll

2-Sep-05 7:47

Hi All,

Please tell me what :: operator means in C++. For example,

[code]

ShowList::ShowList( void )
{
.........
........
}

[\code]

Thanks

Preeti9

Re: :: operator

PJ Arends2-Sep-05 8:26

PJ Arends

2-Sep-05 8:26

:: is the Scope Resolution Operator[^].

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" - mYkel - 21 Jun '04

"There's not enough blatant self-congratulatory backslapping in the world today..." - HumblePie - 21 Jun '05

Within you lies the power for good - Use it!

Re: :: operator

celllllllll2-Sep-05 8:50

celllllllll

2-Sep-05 8:50

Well, I know that this is scope resolution operator but I am not able to understand what it does.

Anyways, Thanks

Preeti9

Re: :: operator

PJ Arends2-Sep-05 9:03

PJ Arends

2-Sep-05 9:03

Preeti9 wrote:
I know that this is scope resolution operator but I am not able to understand what it does

It resolves the scope of objects D'Oh! | :doh:

. For example std::string tells the compiler to use the string class that is a member of the std namespace.

In your example ShowList::ShowList( void ) you are declaring the default c'tor of the class ShowList ( a c'tor is a function that has the same name as the class). In the same file you could have a function called MyShowList::ShowList( void ) which would be the ShowList function of the MyShowList class. Without the scope resolution operator the compiler would not be able to tell the two apart.

Read some of the links I gave you earlier, and experiment with some code. The concept is not all that difficult. Smile | :)

Re: :: operator

celllllllll6-Sep-05 10:28

celllllllll

6-Sep-05 10:28

Thanks, I got it now. It is not difficult.

Thanks once again

Preeti9

CPreviewView Class

mikobi2-Sep-05 7:18

mikobi

2-Sep-05 7:18

I have Printpreview difficult.

I want from doc/view facilities, to preview all I need to print.

According to all theories I read, i must create my View class derived from CPreviewView, but in my Visual C++ Standard Edition 6.0, i don't have it. how to do now ?
Would you like to send me this library ? (lib file).

Urgent

I learn my self

Re: CPreviewView Class

PJ Arends2-Sep-05 8:21

PJ Arends

2-Sep-05 8:21

CPreviewView is declared in AfxPriv.h and it's implementation is in ViewPrev.cpp. You should have both those files.

Re: CPreviewView Class

mikobi2-Sep-05 20:29

mikobi

2-Sep-05 20:29

Where to find those files, I need them.
And to use it to create my View class from them.

Or send me only the lib of this class

I learn my self

Re: CPreviewView Class

mikobi2-Sep-05 20:43

mikobi

2-Sep-05 20:43

Please Sir, T say that I am using Visual c++ 6.0 standard edition. I thing that's my problem, if perhaps i had professionnal edtion, I would resolve my problem, so i ask if it is possible to send me this class like a librairy to incorporate it to my project.

Thanks

I learn my self

Re: CPreviewView Class

PJ Arends3-Sep-05 8:57

PJ Arends

3-Sep-05 8:57

The files are included in the edition you have. AfxPriv.h is in the VC98/MFC/Include/ folder and ViewPrev.cpp is in the VC98/MFC/SRC folder.

Re: CPreviewView Class

mikobi4-Sep-05 21:18

mikobi

4-Sep-05 21:18

A create a new project. And I create a new view derived from CPreviewView.I insert Afxpriv.h and Viewprev.cpp files in my project.

Now I have this error message :
c:\Program Files\Microsoft Visual Studio\Vc98\Mfc\Src\Viewprev.cpp(169) : error C2491: 'CPreviewView::messageMap' : definition of dllimport static data member not allowed.

What to do ?

I learn my self

Re: CPreviewView Class

PJ Arends4-Sep-05 21:32

PJ Arends

4-Sep-05 21:32

Do not add viewprev.cpp to your project. The file has already been compiled into the MFC42.dll file that contains all the MFC binaries. The file is include with VC so that you can step through it when debugging and/or so that you can read the source to see how MFC is implemented. That goes for all files in the VC98/MFC/SRC/ folder.

Re: CPreviewView Class

mikobi5-Sep-05 3:12

mikobi

5-Sep-05 3:12

Thanks,
I have now derived my view class from CPreviewView. And I add a command handler UI OnFilePreview()like this :
if (!DoPrintPreview(AFX_IDD_PREVIEW_TOOLBAR, this,

RUNTIME_CLASS(CPreviewView), pState))
{
// In derived classes, reverse special window handling
// here for Preview failure case

TRACE0("Error: DoPrintPreview failed");
AfxMessageBox(AFX_IDP_COMMAND_FAILURE);
delete pState; // preview failed to initialize,
// delete State now
}

But it not works well. Not Toolbar menu and it hang also

I learn my self

Re: CPreviewView Class

mikobi5-Sep-05 6:49

mikobi

5-Sep-05 6:49

I have seen again that DoPrintPreview() is not CPreviewView function.
What to do now to make a printpreview ?

I learn my self

RS232 problem

transoft2-Sep-05 6:19

transoft

2-Sep-05 6:19

Hi
I have a RS232 problem. I can initiate the COM1 handle. But when I try to read or write, it just hangs there - look like deadlock. How can I solve this problem?

Thank you very much,

Re: RS232 problem

Trollslayer2-Sep-05 6:21

Trollslayer

2-Sep-05 6:21

Could it be a handshaking problem? This is very common so make sure flow control is turned off since it has to be working at both ends.

The tigress is here Big Grin | :-D

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.