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GDI doublebuffer

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I am using GDI to output my FPS (no DX atm). I am trying to double buffer, but I end up with black rectangles flickering up and down my window.
long OnPaint(TWindow &wnd,HWND hwnd, long wparam, long lparam)
	HDC hdc;
	hdc = BeginPaint(kernel->GetHWND(), &ps); 

	HDC memDC = CreateCompatibleDC(hdc);
	HBITMAP hMemBmp = CreateCompatibleBitmap(hdc, kernel->GetWidth(), kernel->GetHeight());
	HBITMAP hOldBmp = (HBITMAP)SelectObject(memDC, hMemBmp);

	// Now do all your drawing in memDC instead of in hDC!
	std::string str = boost::lexical_cast<std::string>(kernel->fps.GetCurrent());
	LPCSTR ptr2 = str.c_str();

	TextOut(memDC, 0, 0,ptr2, str.length());
	EndPaint(kernel->GetHWND(), &ps);

	// As a last step copy the memdc to the hdc
	BitBlt(hdc, 0, 0, kernel->GetWidth(), kernel->GetHeight(), memDC, 0, 0, SRCCOPY);

	// Always select the old bitmap back into the device context
	SelectObject(memDC, hOldBmp);

	return 0;

In my main game loop, I am calling InvalidateRect(m_wnd->GetHWND(),NULL,TRUE); to force a redraw. Anyideas?

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Since you're painting over the entire background anyway, make the final parameter to InvalidateRect() FALSE. This will tell Windows to not bother erasing the background.

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Other than the call in the main loop to InvalidateRect(), all the painting is being done in on paint.

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Right now, you're not painting anything other than the output to TextOut(). Since the pixels of a memory DC are unset by default this is why everything but the background under the text stays black. When you paint other things you wont get a black output [smile].

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