case WM_MOUSEMOVE:
int x = LOWORD(lParam);
int y = HIWORD(lParam);
if(X_and_Y_are_inside_the_rectangle)
{
if ( colorRect != colorInside)
{
colorRect = colorInside;
InvalidateRect
UpdateWindow
}
}
else
{
if ( colorRect != colorOutside)
{
colorRect = colorOutside;
InvalidateRect
UpdateWindow
}
}
return 0;
case WM_PAINT:
get_a_dc
paint the rectangle with colorRect
release_dc
return 0;
