;; GetDPI.au3
;;
;; Get the current DPI (dots per inch) setting, and the ratio
;; between it and approximately 96 DPI.
;;
;; Author: Phillip123Adams
;; Posted: August, 17, 2005, originally developed 10/17/2004,
;; AutoIT 3.1.1.67 (but earlier v3.1.1 versions with DLLCall should work).
;;
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;~    ;; Example
;~    #include<guiconstants.au3>
;~    ;;
;~    ;; Get the current DPI.
;~    $a1 = _GetDPI()
;~    $iDPI = $a1[1]
;~    $iDPIRat = $a1[2]
;~    ;;
;~    ;; Design the GUI to show how to apply the DPI adjustment.
;~    GUICreate("Applying DPI to GUI's", 250 * $iDPIRat, 120 * $iDPIRat)
;~    $lbl = GUICtrlCreateLabel("The current DPI value is " & $iDPI &@lf& "Ratio to 96 is " & $iDPIRat &@lf&@lf& "Call function _GetDPI.  Then multiply all GUI dimensions by the returned value divided by approximately 96.0.", 10 * $iDPIRat, 5 * $iDPIRat, 220 * $iDPIRat, 80 * $iDPIRat)
;~    $btnClose = GUICtrlCreateButton("Close", 105 * $iDPIRat, 90 * $iDPIRat, 40 * $iDPIRat, 20 * $iDPIRat)
;~    GUISetState()
;~    ;;
;~    while 1
;~     $iMsg = GUIGetMsg()
;~     If $iMsg = $GUI_EVENT_CLOSE or $iMsg = $btnClose then ExitLoop
;~    WEnd
;~    Exit
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Func _GetDPI ()
   ;; Get the current DPI (dots per inch) setting, and the ratio between it and
   ;; approximately 96 DPI.
   ;;
   ;; Retrun a 1D array of dimension 3.  Indices zero is the dimension of the array
   ;; minus one.  Indices 1 = the current DPI (an integer).  Indices 2 is the ratio
   ;; should be applied to all GUI dimensions to make the GUI automatically adjust
   ;; to suit the various DPI settings.
   ;; 
   ;; Author: Phillip123Adams
   ;; Posted: August, 17, 2005, originally developed 6/04/2004,
   ;; AutoIT 3.1.1.67 (but earlier v3.1.1 versions with DLLCall should work).
   ;;
   ;; Note: The dll calls are based upon code from the AutoIt3 forum from a post
   ;; by this-is-me on Nov 23 2004, 10:29 AM under topic "@Larry, Help!"  Thanks
   ;; to this-is-me and Larry.  Prior to that, I was obtaining the current DPI
   ;; from the Registry:
   ;;    $iDPI = RegRead("HKCU\Control Panel\Desktop\WindowMetrics", "AppliedDPI")
   ;;
   Local $a1[3]
   Local $iDPI, $iDPIRat, $Logpixelsy = 90, $hWnd = 0
   Local $hDC = DllCall("user32.dll", "long", "GetDC", "long", $hWnd)
   Local $aRet = DllCall("gdi32.dll", "long", "GetDeviceCaps", "long", $hDC[0], "long", $Logpixelsy)
   Local $hDC = DllCall("user32.dll", "long", "ReleaseDC", "long", $hWnd, "long", $hDC)
   $iDPI = $aRet[0]
   ;; Set a ratio for the GUI dimensions based upon the current DPI value.
   Select
      Case $iDPI = 0
         $iDPI = 96
         $iDPIRat =  94
      Case $iDPI < 84
         $iDPIRat =  $iDPI / 105
      Case $iDPI < 121
         $iDPIRat =  $iDPI / 96
      Case $iDPI < 145
         $iDPIRat =  $iDPI / 95
      Case Else
         $iDPIRat =  $iDPI / 94
   EndSelect
   $a1[0] = 2
   $a1[1] = $iDPI
   $a1[2] = $iDPIRat
   ;; Return the array
   Return $a1
EndFunc