'What Win32 message is sent to window at the beginning of resize?

I need Win32 analog of C#'s ResizeBegin to store some data before receiving the first WM_SIZE. I believe I used it very long ago, but cannot find any reference. For some weird reason, Spy++ on my computer is not operational (both 64- and 32-bit versions, I will deal with them later). I hope, somebody can help me out, thanks in advance!

It looks like it is WM_WINDOWPOSCHANGING, at least, it is sent at the right moment. Please correct me if I am wrong!



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