Zoom.ahk

OnExit handle_exit

  Gui,  +AlwaysOnTop  +Owner +Resize +ToolWindow ; window for the dock
  Gui, Show, NoActivate w400 h400 x300 y50 , PrintScreen
  Gui, Add, DDL, vzoom   , 0.5|1|2||4|8|16
  Gui, Add, Checkbox, y12 x150 vantialize, Antialize ?
  Gui, Add, Slider, vdelay x220 y0  Range15-200
  Gui, Add, Text, x340 y12 w80  vdelay2

  WinGet PrintScreenID, id  ,PrintScreen  ;
  WinSet, Transparent , 254, PrintScreen

  ;retrieve the unique ID number (HWND/handle) of that window
  WinGet, PrintSourceID, id

  hotkey , #x           , toggle_follow
  hotkey , +$LButton    , click_through

  toolbar_def:=35
  toolbar := toolbar_def
  follow :=0

  hdd_frame := DllCall( "GetDC", UInt, PrintSourceID )
  hdc_frame := DllCall( "GetDC", UInt, PrintScreenID )

  hdc_buffer := DllCall("gdi32.dll\CreateCompatibleDC", UInt,  hdc_frame)  ; buffer
  hbm_buffer := DllCall("gdi32.dll\CreateCompatibleBitmap", UInt,hdc_frame, Int,A_ScreenWidth, Int,A_ScreenHeight)
 
  Gosub, Repaint
return

toggle_follow:
    follow := 1 - follow
 
    if follow = 1
    {
        WinSet Region, 0-0  W%ww% H%wh% E  , PrintScreen
        toolbar := -32 ; height of window title
        GuiControl, Hide, zoom
    }
    else
    {
        WinSet Region,, PrintScreen
        toolbar :=toolbar_def
        GuiControl, Show, zoom
    }
Return

click_through:
    if follow = 1
    {
      Gui, Hide
      Send, {Click}
      SetTimer, Repaint , Off
      Sleep, 100
      Gui, Show
      SetTimer, Repaint, %delay%
    }
Return

Repaint:

   CoordMode, Mouse, Screen               
   MouseGetPos, start_x, start_y             ;  position of mouse
   Gui, Submit, NoHide                       ; needed to read the dropdown and slidervalue
   GuiControl,, delay2 , delay %delay% ms
   WinGetPos, wx, wy, ww, wh , PrintScreen

   wh2 := wh - toolbar

    DllCall( "gdi32.dll\SetStretchBltMode", "uint", hdc_frame, "int", 4 * antialize )  ; Halftone better quality with stretch
   
    DllCall("gdi32.dll\StretchBlt", UInt,hdc_frame, Int,0, Int,toolbar, Int,ww, Int,wh - toolbar
          , UInt,hdd_frame, Int
          , start_x-(ww / 2 / zoom)
          , Int,start_y -( wh2 / 2/zoom), Int,ww / zoom, Int,wh2 / zoom ,UInt,0xCC0020) ; SRCCOPY

   if follow = 1
     WinMove, PrintScreen, ,start_x -ww/2 , start_y-wh/2
   
  SetTimer, Repaint , %delay%
Return

GuiClose:
handle_exit:
   DllCall("gdi32.dll\DeleteObject", UInt,hbm_buffer)
   DllCall("gdi32.dll\DeleteDC", UInt,hdc_frame )
   DllCall("gdi32.dll\DeleteDC", UInt,hdd_frame )
   DllCall("gdi32.dll\DeleteDC", UInt,hdc_buffer)
ExitApp