WM_NCXBUTTONDBLCLK top-level constant
int
const WM_NCXBUTTONDBLCLK
Posted when the user double-clicks the first or second X button while the cursor is in the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
Implementation
const WM_NCXBUTTONDBLCLK = 0x00AD;