How to convert a script using VarSetCapacity to AHK v2?

I have been using the script Advanced Window Snap, which snaps windows to various places of the monitor, which uses the function GetMonitorIndexFromWindow to determine in which monitor a window is located.

I am converting it to AHKv2.

So far, I could get this:

GetMonitorIndexFromWindow(windowHandle) {    ; Starts with 1.    monitorIndex := 1; Original;    VarSetCapacity(&monitorInfo, 40); My try    monitorInfo := Buffer(40)    NumPut("Uint", 40, monitorInfo)    if (monitorHandle := DllCall("MonitorFromWindow", "uint", windowHandle, "uint", 0x2))&& DllCall("GetMonitorInfoA", "uint", monitorHandle, "uint", &monitorInfo) {        monitorLeft   := NumGet(monitorInfo,  4, "Int")        monitorTop    := NumGet(monitorInfo,  8, "Int")        monitorRight  := NumGet(monitorInfo, 12, "Int")        monitorBottom := NumGet(monitorInfo, 16, "Int")        workLeft      := NumGet(monitorInfo, 20, "Int")        workTop       := NumGet(monitorInfo, 24, "Int")        workRight     := NumGet(monitorInfo, 28, "Int")        workBottom    := NumGet(monitorInfo, 32, "Int")        isPrimary     := NumGet(monitorInfo, 36, "Int") & 1        monitorCount := MonitorGetCount        Loop %monitorCount% {            tempMon := MonitorGet(%A_Index%, &tempMonLeft, &tempMonTop, &tempMonRight, &tempMonBottom)            ; Compare location to determine the monitor index.            if ((monitorLeft = tempMonLeft) and (monitorTop = tempMonTop)                and (monitorRight = tempMonRight) and (monitorBottom = tempMonBottom)) {                monitorIndex := A_Index                break            }        }    }    return monitorIndex}

but it doesn't work because the way I replaced VarSetCapacity(monitorInfo, 40) doesn't seem to be what the DllCall expects.

I also tried strings, or buffers, but the DllCall (the second one) complains about "Error: Expected a Number but got a VarRef.".

In fact, I'm not even sure this DllCall is still needed, maybe the functions https://www.autohotkey.com/docs/v2/lib/Monitor.htm could be used to skip it altogether.

How can I convert the function to a syntax compatible with AHK v2?