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;----------------------------------------------------------------------------------------------
; Function:     ShowModal
;               Show GUI modaly. The script continues after the GUI is closed.
;
; Parameters:
;               hGui    - GUI number of the window to be shown
;               hParent - Parents GUI number. Parent will be disabled while hGui is active
;
; Remarks: 
;               When the function returns, default gui will be set to hGui.
;
ShowModal( hGui, hParent ) {
    gui %hParent%:+Disabled
    gui %hParent%:+LastFound
    hp := WinExist()
    Gui, %hGui%:Default
    Gui, +LastFound
    hc := WinExist()
    ShowModal_OnA(hc,hp,"set",0)

    Gui %hGui%:Show
    old := OnMessage(6, "ShowModal_OnA")
    WinWaitClose, ahk_id %hc%
    gui %hParent%:-Disabled
    OnMessage(6, old)
}

ShowModal_OnA(wparam, lparam, msg, hwnd){
    static hc, hp   
   
    if msg = set
        return hc := wparam, hp := lparam
       
    if (wparam & 0xFF) and (hwnd = hp)
        WinActivate ahk_id %hc%
}

   Gui, 2:add, button, gOnbutton, open modal window
   Gui, 2:Show, autsize
return

Create(){
   Gui, 3:add, text, , some text
   Gui, 3:Show, x400 y400 Hide autsize
}

GuiClose:
   ExitApp
return

OnButton:
   hwnd := Create()
   ShowModal(3, 2)
   msgbox after
return