Ignore HWND from WindowFromPoint()

Question

I am creating a system of dockable windows in win32 c++. In order to have real time feedback of where you are dragging the new window, I created a special debug window which only appears during dragging and shows where it will dock. In order to find out which pane will be docked to, I need to account for overlapping windows and find the topmost. To do this I am calling WindowFromPoint(x, y) which finds the HWND immediately under the mouse. This causes a problem because when the debug window is shown, it gets caught by WindowFromPoint, I would like to ignore it. I have attached a picture.

If anyone has alternative suggestions for this plan, I'm happy to hear it. I thought of keeping some list of window order and tracking everytime a new window gets focus, but that seems like a big headache too...

Answer 1

Ok, I got it! I had the right idea but I didnt' realize that a global solution of returning 0 was a bad idea in the window procedure. Here's the right return:

case WM_NCHITTEST:              
        return HTTRANSPARENT;       

Thanks to this thread: Find all windows beneath a point