C / C++ / MFC

23-Jan-15 4:36

Hi, I have a question, situation like:

C++

void funcA() 
{
   CDC	MemDC;
   CDC	*pDC ;
   pDC = GetDC(); 
   memDC.CreateCompatibleDC(pDC);
   
   funcB(memDC);
}

void funcB(CDC *pDC) 
{
   HDC hdc;
   HDC hdcMem;

   hdc = pDC->m_hDC;
   hdcMem = CreateCompatibleDC(hdc);
   ...
   BitBlt(hdc,0,0,100,100,hdcMem,0,0,SRCCOPY);
}

I think this BitBlt() will copy hdcMem to MemDC(in FuncA), right? just want to confirm it.

Richard MacCutchan23-Jan-15 5:35

23-Jan-15 5:35

What exactly are you trying to achieve?

econy23-Jan-15 5:52

23-Jan-15 5:52

I want funcB draw picture on it's own temporary DC, then paste on funcA's memory DC, and FuncA paste the whole funcA's DC to screen.

Like:
B -> A
c -> A
...
x -> A

and A -> screen.

And I had another question, I have a big bitmap, represent the screen, many parts of the bitmap need to update independently and frequently.

is it a good idea using one memory DC to hold
all part's temporary DC, then post the whole memory DC to screen? that is, the double buffering technique.

Richard MacCutchan23-Jan-15 6:32

23-Jan-15 6:32

1. Sounds OK. What happens when you try it?
2. Yes, keeping a MemDC with all the information and then updating that, before blitting to screen is probably the best way.

econy23-Jan-15 6:38

23-Jan-15 6:38

Thanks, have not try it.
Just thinking if the way is reasonable.

Richard MacCutchan23-Jan-15 6:45

CDC bitblt function with HDC parameter?

23-Jan-15 6:45

Trying things is the best way to learn.

econy23-Jan-15 4:17

Re: CDC bitblt function with HDC parameter?

23-Jan-15 4:17

Hi,I wonder how a bitblt function of a CDC object, which src is a HDC object?
like:

C++

MemDC.BitBlt(Icon.pos_x, Icon.pos_y, bm.w, bm.h,HdcObject,0,0,SRCCOPY);

Albert Holguin23-Jan-15 4:28

Albert Holguin

23-Jan-15 4:28

Quote:
which src is a HDC object?

What? That doesn't make sense. Try rephrasing or expand on what you're trying to ask.

Re: CDC bitblt function with HDC parameter?

econy23-Jan-15 4:38

Re: CDC bitblt function with HDC parameter?

23-Jan-15 4:38

I mean HdcObject in the code.

I just want to copy a HDC object to CDC object, use CDC object's BitBlt() function.

Albert Holguin23-Jan-15 5:15

Albert Holguin

23-Jan-15 5:15

HDC is a handle not an object....

You can use CDC::FromHandle() to get a temporary object for immediate use. Alternatively, you can CDC::Attach() to keep a more permanent CDC object around. You should make sure you release a device context (DC) when you're done using it (FromHandle sort of automatically handles this situation by going out of scope).

If you have CWnds, you can also get a pointer to an existing CDC with CWnd::GetDC().

There is a lot of info on drawing in GDI online, I suggest you read up on it.

""Object reference not set to an instance of an object" when creating new project with VS

jeff623-Jan-15 0:04

jeff6

23-Jan-15 0:04

Hello, I get this error when I try to create a new project wi h Visual Studio 2010 (XP), Win32, MFC or Forms (only VB works)

"Object reference not set to an instance of an object"

I found nothing with Google for this case (just creating a new project) and tried to uninstall/install, repair, n times, impossible to fix Frown | :-(

Thanks in advance for any idea, I'm desperate, unable to create even an empty Win32 project !

Re: ""Object reference not set to an instance of an object" when creating new project with VS

Richard MacCutchan23-Jan-15 0:57

Re: ""Object reference not set to an instance of an object" when creating new project with VS

23-Jan-15 0:57

Looks like a Visual Studio problem, but impossible to guess what.

jeff623-Jan-15 1:16

jeff6

23-Jan-15 1:16

But it appeared just recently, it had worked for years before

Re: ""Object reference not set to an instance of an object" when creating new project with VS

Richard MacCutchan23-Jan-15 1:31

Get CListCtrl scrollbar rectangle

23-Jan-15 1:31

I can only assume that something has been corrupted somewhere. But as I said before, it's impossible to guess what. Your only chance is to collect all the information that you can, and report it to Microsoft.

_Flaviu22-Jan-15 22:55

22-Jan-15 22:55

How can I get the CListCtrl scrollbar rectangle ? Whether the scrollbar is visible or not, I tested in following way:

C++

if(GetStyle() & WS_VSCROLL)
{
}

but, in order to change the scrollbar background by DrawThemeBackground[^], I need the scrollbar rectangle ... how can I retrieve the scrollbar rectangle ?

Jochen Arndt22-Jan-15 23:10

Jochen Arndt

22-Jan-15 23:10

Just call GetScrollBarInfo[^] passing OBJID_VSCROLL as idObject parameter.

_Flaviu22-Jan-15 23:45

22-Jan-15 23:45

Thank you Jochen ... the rectangle is retrieve it ... Smile | :)

I have to dig in, because it seems that something is wrong in my code, because though rectangle is correct now, the color of scrollbar is not drawn ...

C++

void CGridCtrlExt::OnDraw(CDC* pDC)
{
//	draw the grid

	HTHEME hTheme = OpenThemeData(m_hWnd, L"WINDOW");
//	HTHEME hTheme = OpenThemeData(m_hWnd, L"MFCGridCtrl");
	if(NULL != hTheme)
	{
		if(WS_VSCROLL & GetStyle())
		{
			SCROLLBARINFO si;
			si.cbSize = sizeof(SCROLLBARINFO);
			GetScrollBarInfo(OBJID_VSCROLL, &si);
			CRect rect(si.rcScrollBar);
			pDC->FillSolidRect(&rect, RGB(255, 255, 0));
			DrawThemeBackground(hTheme, pDC->GetSafeHdc(), WP_VERTSCROLL, VSS_NORMAL, &rect, NULL);
		}
		CloseThemeData(hTheme);
	}
}

Jochen Arndt22-Jan-15 23:59

Jochen Arndt

22-Jan-15 23:59

This may be because the scroll bar is redrawn by the system.

You may use a custom drawn scroll bar or handle WM_CTLCOLOR when you only need to change the background.

Searching the web may give you some solutions. The article http://www.drdobbs.com/windows/developing-a-custom-windows-scrollbar-in/184416659[^] is rather old but contains a good introduction and shows how to implement a custom drawn scroll bar.

_Flaviu23-Jan-15 1:14

23-Jan-15 1:14

"You may use a custom drawn scroll bar or handle WM_CTLCOLOR when you only need to change the background"

I already tried that ... if I override WM_CTLCOLOR I could color everything, except scrollbars ... Smile | :)

"Searching the web may give you some solutions. The article http://www.drdobbs.com/windows/developing-a-custom-windows-scrollbar-in/184416659[^] is rather old but contains a good introduction and shows how to implement a custom drawn scroll bar."

I saw that article, but is about replacing the original scrollbar with CScrollBarEx control ... well, in this case I will front with 2 issues: hiding the original scrollbar, and second, synchronize the listctrl with CScrollbarEx control ... I think that is the longest road ... and the hardest ...

I thought that trying to use DrawThemeBackground I could change the scrollbars colors ... Frown | :(

I am working on that for weeks ... I have to dig in ...

_Flaviu23-Jan-15 1:38

23-Jan-15 1:38

"This may be because the scroll bar is redrawn by the system"

I wonder if I put properly the scrollbar coloring code ... inside of CMyControl::OnDraw is ok ? I guess not ...

Jochen Arndt23-Jan-15 2:08

Jochen Arndt

23-Jan-15 2:08

OnDraw is a CView member function. You probably mean some kind of custom / owner draw. But this won't work for the scroll bars of list controls because only the list control content can be changed by this method. The scroll bar is still drawn by the system when necessary and your drawing vanishes.

If handling WM_CTLCOLOR did not work (and I believe meanwhile that it does not work with list controls), the only solution is using a complety custom drawn control or another GUI framework like Qt.

_Flaviu23-Jan-15 2:26