WM_MBUTTONDBLCLK top-level constant
int
const WM_MBUTTONDBLCLK
Posted when the user double-clicks the middle mouse button while the cursor is within 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_MBUTTONDBLCLK = 0x0209;