PostMessage() sending a click to another window

[Tvlao]

For some reason this code doesn't work.
There are two windows. One window overlaps another. The top window with transparency intercepts clicks and directs them to the window below.

Code: Select all

OnMessage 0x0201, WM_LBUTTONDOWN

MakeLong(LoWord, HiWord ) 
{
	return (HiWord << 16) | (LoWord & 0xffff)
}

; --------------------------------------------

win1 := Gui("AlwaysOnTop")
win1.BackColor := 0xFFFFFF

Btn := win1.AddButton("Default x0 y0 w100", "Test")
Btn.OnEvent("Click", Btn_Click)  

Btn_Click(*){
    MsgBox "Btn_Click()"
}

win1.Show("x0 y0 w900 h400")

; --------------------------------------------
win2 := Gui("AlwaysOnTop")
win2.BackColor := 0xFFFFFF
win2.Show("x0 y0 w900 h400")
WinSetTransparent 100, "ahk_id" win2.Hwnd
; --------------------------------------------

WM_LBUTTONDOWN(wParam, lParam, msg, hwnd) {

    if(hwnd != win2.Hwnd){
        return
    }

    if wParam == 0x0001{
        ; LBUTTONDOWN
        PostMessage 0x201, 0x0001, MakeLong(4, 4),, win1.Hwnd
        ;WM_LBUTTONUP
        PostMessage 0x202, 0, MakeLong(4, 4), , win1.Hwnd              

    }
}

It is expected that the button in the window below will be pressed, but this does not happen.
PostMessage() doesn't seem to send messages.