I'm working on a custom child window in C++ that will look and act like the "NumericUpDown" in VB.NET. The window will handle WM_PAINT by itself, but I have never painted a background before since most of my experience lies with OpenGL and 3D graphics. I know how to use "BeginPaint()" and "EndPaint()", and I know how to check the "fErase" member of a painting structure to know if I have to draw the background. The window class is created without a background being specified on purpose, so how would I figure out which parts or all of the background need painting, and then what would I do to paint those parts with the correct window background color? Thanks in advance for the help, as always.