Topic: How to make the transparent window with opaque lines?

For example, I want to deduce (sight) cross-hairs that it was there always on center of the screen. Tried to receive a window context (hDC) and to write to it: works, but not everywhere, and strongly blinks (that naturally)... I so understand that the decision is to make completely the transparent window, and in it to draw opaque lines. Source codes how to make a window (floor) transparent  it is a lot of, but there the window with all contents becomes transparent, and it is necessary to me that contents  completely. A question 1: the Subject. A question 2: What else there are candidate solutions? P.S. It is supposed that application (game) is launched in a mode "fullscreen (windowed)". To get in  D3D I yet I do not want.