WinCenter.ahk

#!Space::CenterActiveWindow()    ; Win+Alt+Space

CenterActiveWindow()
{
    winHandle := WinExist("A")

    VarSetCapacity(monitorInfo, 40)
    NumPut(40, monitorInfo)

    monitorHandle := DllCall("MonitorFromWindow", "uint", winHandle, "uint", 0x2)
    DllCall("GetMonitorInfo", "uint", monitorHandle, "uint", &monitorInfo) 

    A_Left   := NumGet(monitorInfo, 20, "Int")
    A_Top    := NumGet(monitorInfo, 24, "Int")
    A_Right  := NumGet(monitorInfo, 28, "Int")
    A_Bottom := NumGet(monitorInfo, 32, "Int")

    WinGetPos,,, Width, Height, ahk_id %winHandle%
    winX := A_Left + (A_Right - A_Left - Width) / 2
    winY := A_Top + (A_Bottom - A_Top - Height) / 2

    WinMove, A,, winX, winY
}