Runtime Drawing on window

I usually put my drawing in WM_PAINT to draw on screen but if you need to figure out this at runtime would you still use GDI drawing APIs?

Example-

//In WndProc

case WM_PAINT:
{
   hdc = GetWindowDC (hwnd) ;
   //draw here using hdc
   ReleaseDC (hwnd, hdc) ;
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}

Instead of putting the drawing in WM_PAINT, can you draw using function and still get the functionality of WM_PAINT to redraw?

---

WM_PAINT is asynchronous, meaning its called when the OS decides it's time to repaint the window. You can also draw synchronously by calling GetDC()/ReleaseDC() outside of a WM_PAINT message handler.

http://msdn.microsoft.com/en-us/library/dd145126(v=vs.85).aspx

Also, when handling WM_PAINT messages, you should use BeginPaint()/EndPaint() and return 0. I've seen some strange side-effects when this does not happen.