Thread: Animation without tearing

Hi

I have an MFC dialogbox application where I draw bitmaps after each other making it look like a movie. But the image tears sometimes. Is there a way to make it look better?

This is current code:

Code:

CPaintDC dc(this);
CDC hdcmem;

hdcmem.CreateCompatibleDC(NULL);
CGdiObject *old = hdcmem.SelectObject(&m_bitmap);

dc.StretchBlt(STARTXSTATIC + m_size.cx + 10, STARTYSTATIC, 
	  m_size.cx, m_size.cy / m_nofimages, 
	  &hdcmem, 0, m_curanim * (m_size.cy / m_nofimages), m_size.cx,
	  m_size.cy / m_nofimages, SRCCOPY);

hdcmem.SelectObject(old);

Double Buffering. Draw it all to a back buffer then blast it at once to screen, that should stop tearing.

It appears as if he is already double buffering from hdcmem to the paint DC of the window. Have you turned off the windows default provided double buffering scheme for your window? Sometimes that will get in the way of a refresh and/or cause images to fail to display or display incorrectly. I forget which call in MFC does this so you will have to research it.

you mean WM_ERASEBKGND? That caused a lot of other problems
I solved it by removing the Invalidate from the OnTimer and calling the DrawFrame function directly from the timerevent. That solved it.