why not to send WM_PAINT manually

Question

I have read that I should never send WM_PAINT manually and should call InvalidateRect instead but didn\'t found anything about why not, however. So

Answer 1

You don't have any information about other program's windows uncovering your windows. Only the operating system has this information. So you don't really know all the time when or where your window needs to be repainted. WM_PAINT and BeginPaint provide this missing information.