Highrez

Good day.

Your program can be attached to a button WM_NCLBUTTONDBLCLK + wParam HTCAPTION ?
(WM_NCLBUTTONDOWN, WM_NCLBUTTONUP, WM_NCLBUTTONDBLCLK and WM_NCLBUTTONUP)

This is a very convenient feature

No, because the mouse hook does not expose this information I'm afraid.
Those messages apply to windows only and are not intercept-able by a mouse hook.

No no! I meant that you need not react to this event. It is necessary to emulate the sending of event data to the active window by pressing a button of the mouse. Try several times in a row for one active window - the result will please you.