Re: How to replace a CDC of another CWnd - C / C++ / MFC Discussion Boards

Re: How to replace a CDC of another CWnd

Hamid_RT1-Aug-07 22:56

Hamid_RT

1-Aug-07 22:56

Do you want to draw on the window of other programs?

WhiteSky

Re: How to replace a CDC of another CWnd

FlyingBear1-Aug-07 23:17

FlyingBear

1-Aug-07 23:17

No, I want to get a snapshot of another application, for example, to make a album of all the running applications

Re: How to replace a CDC of another CWnd

FlyingBear1-Aug-07 23:22

FlyingBear

1-Aug-07 23:22

I tried to use CWnd::GetDC(), and select a CBitmap created by my own, then call CWnd::RedrawWindow(), after that, I suppose the content in CBitmap should be the window, but it failed.

Re: How to replace a CDC of another CWnd

Iain Clarke, Warrior Programmer1-Aug-07 23:52

Iain Clarke, Warrior Programmer

1-Aug-07 23:52

This isn't tested, or even compiled, just quickly typed up...

CClientDC   dcOther (GetDesktopWindow ()); // grabs the other DC
CRect rc;
::GetWindowRect (hWndToClone, &rc); // how big is it?

CBitmap bmpTemp, *bmpOld;
CDC dcClone;
dcClone.CreateCompatibleDC (&dcOther);
bmpTemp.CreateCompatibleBmp (&dcOther, rc.Width (), rc.Height ());
bmpOld = dcClone.SelectObject (&bmpTemp);

dcClone.BitBlt (0,0, rc.Width (), rc.Height (), &dcOther, 0,0, SRCCPY);

dcClone.SelectObject (bmpOld); // tidy up

and now dcClone should hold a copy of the contents of the first window - or at least what it shows on the screen.

You should look at the very useful article by PJ Arends: Image Viewer[^].

Good luck,

Iain.

Re: How to replace a CDC of another CWnd

FlyingBear2-Aug-07 0:41

FlyingBear

2-Aug-07 0:41

Really thanks, I tried this, the rect is right, but the contents is from the corresponding top level windows, do i need to bring the window to top, and then use this method, but if so, the orders of the windows will be totally ruined.

<br />
CDC dc;<br />
CDC* pDC = pWnd->GetDC();<br />
CRect rc;<br />
pWnd->GetWindowRect(rc);<br />
dc.CreateCompatibleDC(pDC);<br />
CBitmap bmp;<br />
bmp.CreateCompatibleBitmap(pDC, rc.Width(), rc.Height());<br />
HBITMAP bmpOld;<br />
bmpOld = (HBITMAP)dc.SelectObject(bmp);<br />
dc.BitBlt(0, 0, rc.Width(), rc.Height(), pDC, 0, 0, SRCCOPY);<br />
CxImage imgSnapshot;<br />
imgSnapshot.CreateFromHBITMAP(bmp);<br />

Re: How to replace a CDC of another CWnd

Iain Clarke, Warrior Programmer2-Aug-07 1:16

Iain Clarke, Warrior Programmer

2-Aug-07 1:16

Yes, this is a screen capture.

Unfortunately, unless the window is visible, window's won;t actually bother sending a WM_PAINT to it, so it won't bother to redraw (this may not be the truth under Vista).

Which is what the WM_PRINT message is for. But as you said, it does require the "victim" app to play nicely. You could try replacing the GetDesktopWindow call in my code with hWndFromOtherApp, and use GetClientRect (hWndFromOtherApp), but I'm not sure how nicely it will work.

Its worth a try though, as it won't take much effort to test!

Good luck,

Iain.

Re: How to replace a CDC of another CWnd

FlyingBear2-Aug-07 2:30

FlyingBear

2-Aug-07 2:30

I tried, the WM_PRINT approach generally fails because I cannot suppose other application to implement it. And using BringWindowToTop, it still have some problems:

(1) When a window is maximized, the rect from GetWindowRect is the one when not maximized.
(2) When something was set to be always on top, it will appear on the resulted images.

I wonder whether subclassing of a window can do it correctly.

Re: How to replace a CDC of another CWnd

Hamid_RT2-Aug-07 2:47

Hamid_RT

2-Aug-07 2:47

Im not sure its your answer or no but if its not your answer reply to me

HDC m_hdcMem,hdc;
HBITMAP m_Bitmap,m_OldBitmap,hMainBmp ;

hdc=GetDesktopWindow()->GetDC()->m_hDC;//GetDC()->m_hDC 
    m_hdcMem= CreateCompatibleDC(hdc);
	
	m_Bitmap = CreateCompatibleBitmap(hdc,800,600);
 m_OldBitmap=(HBITMAP) SelectObject(m_hdcMem, m_Bitmap);

   BitBlt(m_hdcMem, 0,0,800,600, hdc,0,0,SRCCOPY);
    hMainBmp =(HBITMAP) SelectObject(m_hdcMem, m_OldBitmap);

/////Save this snapshot to a file;)/////
CImage m_Image;
m_Image.Attach(hMainBmp);
m_Image.Save("c:\\test.bmp");
m_Image.Detach();
DeleteDC(m_hdcMem);
DeleteObject(hMainBmp );
DeleteObject(m_OldBitmap);

WhiteSky

Re: How to replace a CDC of another CWnd

FlyingBear2-Aug-07 3:57

FlyingBear

2-Aug-07 3:57

I want a snapshot for a specific application, which I only has its HWND, and I don't want the always-on-top things to appear in the resulted image, besides, the orginal orders of the windows should not be changed, this is pretty like the window mode of SnagIt, thanks Smile | :)

Re: How to replace a CDC of another CWnd

Hamid_RT2-Aug-07 5:09

Hamid_RT

2-Aug-07 5:09

Well you can use of hwnd on the GetDC that retrieves a handle to dc of current window did you try with it HDC hdc=::GetDC(hWnd);.

WhiteSky

Re: How to replace a CDC of another CWnd

Iain Clarke, Warrior Programmer1-Aug-07 23:23

Iain Clarke, Warrior Programmer

1-Aug-07 23:23

hDC = ::GetDC (hWnd);
// do your thing!
::ReleaseDC (hWnd, hDC);

Sometimes its simpler that you think!

You should also have a peek at WM_PRINT, as it asks the other window to draw itself nicely in a DC you provide.

Iain.

Re: How to replace a CDC of another CWnd

FlyingBear2-Aug-07 0:25

FlyingBear

2-Aug-07 0:25

Thanks, i tried the WM_PRINT way, code like this:

<br />
CDC dc;<br />
dc.CreateCompatibleDC(NULL);<br />
CBitmap bmp;<br />
CRect rc;<br />
pWnd->GetClientRect(rc);<br />
bmp.CreateBitmap(rc.Width(), rc.Height(), 1, 24, NULL);<br />
HBITMAP hbmp = (HBITMAP)dc.SelectObject(bmp.GetSafeHandle());<br />
pWnd->SendMessage(WM_PRINT, WPARAM(dc.GetSafeHdc()), PRF_CHILDREN);<br />
CxImage imgSnapshot;<br />
imgSnapshot.CreateFromHBITMAP(bmp);<br />

But the resulted image seems invalid, does that require the target window to write code for processing WM_PRINT message, otherwise it doesn't work?

Re: How to replace a CDC of another CWnd

Mark Salsbery2-Aug-07 9:27

Mark Salsbery

2-Aug-07 9:27

Shouldn't you use the window rect instead of the client rect?

What's wrong with the resulting bitmap?

Did you un-select the bitmap from the DC?

This works for me:

CWindowDC WindowDC(this);
CDC MemoryDC;
MemoryDC.CreateCompatibleDC(&WindowDC);
CBitmap WindowBitmap;
CRect WindowRect;
GetWindowRect(&WindowRect);
WindowBitmap.CreateCompatibleBitmap(&WindowDC, WindowRect.Width(), WindowRect.Height());
CBitmap *pOldBitmap = MemoryDC.SelectObject(&WindowBitmap);
SendMessage(WM_PRINT, (WPARAM)(HDC)MemoryDC, PRF_ERASEBKGND | PRF_CHILDREN | PRF_CLIENT | PRF_NONCLIENT);

//**test**
BitBlt(WindowDC,100,100,WindowRect.Width(), WindowRect.Height(), MemoryDC, 0, 0, SRCCOPY);
//**end test**

MemoryDC.SelectObject(pOldBitmap);

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: How to replace a CDC of another CWnd

Michael Dunn2-Aug-07 8:18

Michael Dunn

2-Aug-07 8:18

Check out PrintWindow()

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! Ericahist | PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

Hungarian notation FTW

Re: How to replace a CDC of another CWnd

FlyingBear2-Aug-07 8:53

FlyingBear

2-Aug-07 8:53

Thanks, this does not work for all the applications, I guess it uses SendMessage(WM_PRINT) internally.

Re: How to replace a CDC of another CWnd

FlyingBear2-Aug-07 19:21

FlyingBear

2-Aug-07 19:21

Problem solved, thanks for all your help Smile | :)

Enable C++ Exceptions

Tal S.1-Aug-07 22:37

Tal S.

1-Aug-07 22:37

Hello,

I have old VC6 compiled at VS2005.

I would like to keep 'Enable C++ Exceptions' = Yes (/EHsc) option at the project properties.

One of the functions: __event - is not compiled.

Do you know if I can use another function? Should I do any changes?

Thanks!

Re: Enable C++ Exceptions

Russell^'2-Aug-07 2:35

Russell^'

2-Aug-07 2:35

Are you not using the statement try-catch?
like:

try{
...
}catch(CMemoryException +pErr){
...
}

Russell

Running 10 threads at a time

neha.agarwal271-Aug-07 22:22

neha.agarwal27

1-Aug-07 22:22

Hi all,

I have made a for loop which has to execute 200 times. In that loop i have a started a worker thread. Now what i want is after 10 times that loop should wait for 1 of the thread to finish and then start next thread i.e only 10 thread can execute at a time.How to do it??

Thanks in advance

Re: Running 10 threads at a time

Iain Clarke, Warrior Programmer1-Aug-07 22:48

Iain Clarke, Warrior Programmer

1-Aug-07 22:48

I;d question your design decision as desiribed, but I'll assume your simplifying your actual problem.

Thread handles also act as signalling handles.

So:

....
    HANDLE hThread [MAX] = { NULL, NULL, ... NULL };
    DWORD dwID [MAX];

    for (nTest = 0; nTest < 10; nTest++)
    {
        hThread [nTest] = CreateThread (......., &(dwID [nTest], lParam);
        if (!hThread [nTest])
        {
            Handle error somehow
        }
    }

    for (nTest = 10; nTest < XXXXX; nTest++)
    {
        dwWait = WaitForMultipleObjects (hThread, 10, INFINITE);
        if (dwWait >= WAIT_OBJECT_0 && dwWait < WAIT_OBJECT_0+10)
        {
           nThread = dwWait - WAIT_OBJECT_0;
           hThread [dwThread] = CreateThread (......., &(dwID [nThread], lParam);
           if (!hThread [nTest])
           {
               Handle error somehow
           }
        }
    }

/pre>

Tada!

Iain.
<div class="CPhogPost"></div> 

<div class="ForumSig"></div>

Re: Running 10 threads at a time

Iain Clarke, Warrior Programmer1-Aug-07 22:52

Iain Clarke, Warrior Programmer

1-Aug-07 22:52

I would also point out that I have answered your question very literally. My answer would block your initial thread, is very fragile, etc.

Much better would be to look into thread pools (which I have no experience of), of have your thread posting a "I'm done!" message to a UI main thread, which would then fire off another thread. You could then give the user a more interactive experience, without thinking the process has hung. It would also allow you to handle failure more gracefully.

Iain.

Re: Running 10 threads at a time

Russell^'1-Aug-07 22:57

Russell^'

1-Aug-07 22:57

You can use a variable to count the threads

Global declaration:

<code>volatile </code>UINT RunningThread;   //Create the counter

The main function:

foo(){
RunningThread=0;   //Reset the counter
for(i=0;i<200;i++){
   if(RunningThread<10){
      //Create Thread
      RunningThread++;   //Incremente the counter
   }else{
      wait(100);
      i--;
      continue;
   }
}
}

The thread:

Thread(...){
//Work process
RunningThread--;  // Before it ends decrement the counter
}

Russell

Re: Running 10 threads at a time

neha.agarwal272-Aug-07 2:09

neha.agarwal27

2-Aug-07 2:09

i tried Russell's procedure but its hanging my application and not solving my problem completely....in my thread i m finding out a particular website's html code so, because of so many threads trying to do it, many times it gives page cannot be displayed....how to solve it

Re: Running 10 threads at a time

Russell^'2-Aug-07 2:27

Russell^'

2-Aug-07 2:27

Probally you have to use a semaphore to use the connection in a more efficient way, limiting the simultaneus request to the web.
You can use for example a boolean variable (like BOOL ConnectionIsBusy). If a thread find it TRUE then it waits that it becomes FALSE, then it lock itself the flag to TRUE, talk with the web, and at the end restore the flag value to FALSE.

A similar way is to limit the number of simultaneus connections using a variable like UINT ConnectionsNumber, that you could use to check that the connection opened are less of a particular value (i.e. 2 or 4).

But the problem depends also on the speed of your connection and/or the amount of traffic that you need to exchange with the web. You have to do some tests.

Russell

Re: Running 10 threads at a time

Mark Salsbery2-Aug-07 8:31

Mark Salsbery

2-Aug-07 8:31

Another way to implement Russell's suggestion is to use an I/O Completion Port[^]

This essentially combines a thread pool with a semaphore. With an I/O Completion Port you could
easily create a pool of 10 threads and queue up 200 operations to be executed by the threads as
they become available.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

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