win32 solution to WM_NCLBUTTONUP

this stupid thing! a “convenient API for detecting mouse button release outside of client area”, only works when the window is maximised (and thus literally pointless). reason because once outside client, mouse is captured for dragging the window so the message is *never sent*. really good.

instead of messing with button messages, use this in your process to detect the button state:
if((GetKeyState(VK_LBUTTON) & 0x100) != 0)