#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>
#include <GuiScrollBars.au3>
#include <ScrollBarConstants.au3>
#include <SendMessage.au3>

Global $aSB_WindowInfo[1][8]

$hGUI = GUICreate("Test", 400, 300)

For $i = 1 To 20
    For $j = 1 To 20
        GUICtrlCreateLabel(($i - 1) * 20 + $j, 10 + 85 * ($i - 1), 10 + 30 * ($j - 1), 75, 25)
    Next
Next

; Generate scrollbars
_GUIScrollbars_Generate($hGUI, 85 * 19 + 75, 30 * 19 + 25)

GUISetState()

While 1

    Switch GUIGetMsg()
        Case $GUI_EVENT_CLOSE
            Exit
    EndSwitch
WEnd

Func _GUIScrollbars_Generate($hWnd, $iH_Scroll = 0, $iV_Scroll = 0, $iH_Tight = 0, $iV_Tight = 0, $fBefore = False)

    ; Check if valid window handle
    If Not IsHWnd($hWnd) Then Return SetError(1, 0, 0)
    If $aSB_WindowInfo[0][0] <> "" Then ReDim $aSB_WindowInfo[UBound($aSB_WindowInfo) + 1][8]

    ; If no scroll sizes set, return error
    If $iH_Scroll = 0 And $iV_Scroll = 0 Then Return SetError(2, 0, 0)

    ; Confirm Tight values
    If $iH_Tight <> 0 Then $iH_Tight = 1
    If $iV_Tight <> 0 Then $iV_Tight = 1

    ; Create structs
    Local $tTEXTMETRIC = DllStructCreate($tagTEXTMETRIC)
    Local $tSCROLLINFO = DllStructCreate($tagSCROLLINFO)
    DllStructSetData($tSCROLLINFO, "cbSize", DllStructGetSize($tSCROLLINFO))
    Local $tRect = DllStructCreate($tagRECT)

    ; Declare local variables
    Local $iIndex = UBound($aSB_WindowInfo) - 1
    Local $iError, $iExtended

    ; Save window handle
    $aSB_WindowInfo[$iIndex][0] = $hWnd

    ; Determine text size
    Local $hDC = DllCall("user32.dll", "handle", "GetDC", "hwnd", $hWnd)
    If Not @error Then
        $hDC = $hDC[0]
        DllCall("gdi32.dll", "bool", "GetTextMetricsW", "handle", $hDC, "ptr", DllStructGetPtr($tTEXTMETRIC))
        If @error Then
            $iError = @error
            $iExtended = @extended
            DllCall("user32.dll", "int", "ReleaseDC", "hwnd", $hWnd, "handle", $hDC)
            Return SetError($iError, $iExtended, -2)
        EndIf
        DllCall("user32.dll", "int", "ReleaseDC", "hwnd", $hWnd, "handle", $hDC)
    Else
        Return SetError(@error, @extended, -1)
    EndIf
    $aSB_WindowInfo[$iIndex][2] = DllStructGetData($tTEXTMETRIC, "tmAveCharWidth")
    $aSB_WindowInfo[$iIndex][3] = DllStructGetData($tTEXTMETRIC, "tmHeight") + DllStructGetData($tTEXTMETRIC, "tmExternalLeading")

    ; Size aperture window without bars
    DllCall("user32.dll", "bool", "GetClientRect", "hwnd", $hWnd, "ptr", DllStructGetPtr($tRect))
    If @error Then Return SetError(@error, @extended, -3)
    Local $iX_Client_Full = DllStructGetData($tRect, "Right") - DllStructGetData($tRect, "Left")
    Local $iY_Client_Full = DllStructGetData($tRect, "Bottom") - DllStructGetData($tRect, "Top")
    $aSB_WindowInfo[$iIndex][4] = $iX_Client_Full
    $aSB_WindowInfo[$iIndex][5] = $iY_Client_Full

    ; Register scrollbar and mousewheel messages
    GUIRegisterMsg($WM_VSCROLL, "_Scrollbars_WM_VSCROLL")
    GUIRegisterMsg($WM_HSCROLL, "_Scrollbars_WM_HSCROLL")
    GUIRegisterMsg($WM_MOUSEWHEEL, "_Scrollbars_WM_MOUSEWHEEL")
    GUIRegisterMsg($WM_MOUSEHWHEEL, '_Scrollbars_WM_MOUSEHWHEEL')

    ; Show scrollbars
    _GUIScrollBars_ShowScrollBar($hWnd, $SB_BOTH, False)
    If $iH_Scroll Then _GUIScrollBars_ShowScrollBar($hWnd, $SB_HORZ)
    If $iV_Scroll Then _GUIScrollBars_ShowScrollBar($hWnd, $SB_VERT)

    ; Size aperture window with bars
    DllCall("user32.dll", "bool", "GetClientRect", "hwnd", $hWnd, "ptr", DllStructGetPtr($tRect))
    If @error Then Return SetError(@error, @extended, -3)
    Local $iX_Client_Bar = DllStructGetData($tRect, "Right") - DllStructGetData($tRect, "Left")
    Local $iY_Client_Bar = DllStructGetData($tRect, "Bottom") - DllStructGetData($tRect, "Top")

    ; If horizontal scrollbar is required
    Local $iH_FullPage
    If $iH_Scroll Then
        If $fBefore Then
            ; Use actual aperture width
            $aSB_WindowInfo[$iIndex][4] = $iX_Client_Bar
            ; Determine page size (aperture width / text width)
            $iH_FullPage = Floor($aSB_WindowInfo[$iIndex][4] / $aSB_WindowInfo[$iIndex][2])
            ; Determine max size (scroll width / text width - tight)
            $aSB_WindowInfo[$iIndex][6] = Floor($iH_Scroll / $aSB_WindowInfo[$iIndex][2]) - $iH_Tight
        Else
            ; Use reduced aperture width only if other scrollbar exists
            If $iV_Scroll Then $aSB_WindowInfo[$iIndex][4] = $iX_Client_Bar
            ; Determine page size (aperture width / text width)
            $iH_FullPage = Floor($aSB_WindowInfo[$iIndex][4] / $aSB_WindowInfo[$iIndex][2])
            ; Determine max size (scroll width / text width * correction factor for V scrollbar if required - tight)
            $aSB_WindowInfo[$iIndex][6] = Floor($iH_Scroll / $aSB_WindowInfo[$iIndex][2] * $aSB_WindowInfo[$iIndex][4] / $iX_Client_Full) - $iH_Tight
        EndIf
    Else
        $aSB_WindowInfo[$iIndex][6] = 0
    EndIf

    ; If vertical scrollbar required
    Local $iV_FullPage
    If $iV_Scroll Then
        If $fBefore Then
            ; Use actual aperture height
            $aSB_WindowInfo[$iIndex][5] = $iY_Client_Bar
            ; Determine page size (aperture width / text width)
            $iV_FullPage = Floor($aSB_WindowInfo[$iIndex][5] / $aSB_WindowInfo[$iIndex][3])
            ; Determine max size (scroll width / text width - tight)
            $aSB_WindowInfo[$iIndex][7] = Floor($iV_Scroll / $aSB_WindowInfo[$iIndex][3]) - $iV_Tight
        Else
            ; Use reduced aperture width only if other scrollbar exists
            If $iH_Scroll Then $aSB_WindowInfo[$iIndex][5] = $iY_Client_Bar
            ; Determine page size (aperture width / text width)
            $iV_FullPage = Floor($aSB_WindowInfo[$iIndex][5] / $aSB_WindowInfo[$iIndex][3])
            ; Determine max size (scroll width / text width * correction factor for H scrollbar if required - tight)
            $aSB_WindowInfo[$iIndex][7] = Floor($iV_Scroll / $aSB_WindowInfo[$iIndex][3] * $aSB_WindowInfo[$iIndex][5] / $iY_Client_Full) - $iV_Tight
        EndIf
    Else
        $aSB_WindowInfo[$iIndex][7] = 0
    EndIf

    Local $aRet[4]
    If $iV_Scroll Then
        $aRet[0] = $iX_Client_Bar
    Else
        $aRet[0] = $iX_Client_Full
    EndIf
    If $iH_Scroll Then
        $aRet[1] = $iY_Client_Bar
    Else
        $aRet[1] = $iY_Client_Full
    EndIf
    $aRet[2] = $iX_Client_Bar / $iX_Client_Full
    $aRet[3] = $iY_Client_Bar / $iY_Client_Full

    Local $fSuccess = True
    If _GUIScrollBars_ShowScrollBar($hWnd, $SB_BOTH, False) = False Then $fSuccess = False
    If $iH_Scroll Then
        If _GUIScrollBars_SetScrollInfoMax($hWnd, $SB_HORZ, $aSB_WindowInfo[$iIndex][6]) = False Then $fSuccess = False
        _GUIScrollBars_SetScrollInfoPage($hWnd, $SB_HORZ, $iH_FullPage)
        If @error Then $fSuccess = False
        If _GUIScrollBars_ShowScrollBar($hWnd, $SB_HORZ, True) = False Then $fSuccess = False
    Else
        If _GUIScrollBars_ShowScrollBar($hWnd, $SB_HORZ, False) = False Then $fSuccess = False
    EndIf
    If $iV_Scroll Then
        If _GUIScrollBars_SetScrollInfoMax($hWnd, $SB_VERT, $aSB_WindowInfo[$iIndex][7]) = False Then $fSuccess = False
        _GUIScrollBars_SetScrollInfoPage($hWnd, $SB_VERT, $iV_FullPage)
        If @error Then $fSuccess = False
        If _GUIScrollBars_ShowScrollBar($hWnd, $SB_VERT, True) = False Then $fSuccess = False
    Else
        If _GUIScrollBars_ShowScrollBar($hWnd, $SB_VERT, False) = False Then $fSuccess = False
    EndIf

    If $fSuccess Then Return $aRet
    Return SetError(3, 0, 0)

EndFunc   ;==>_GUIScrollbars_Generate

Func _Scrollbars_WM_VSCROLL($hWnd, $Msg, $wParam, $lParam)

    #forceref $Msg, $wParam, $lParam
    Local $nScrollCode = BitAND($wParam, 0x0000FFFF)
    Local $iIndex = -1, $yChar, $yPos
    Local $Min, $Max, $Page, $Pos, $TrackPos

    For $x = 0 To UBound($aSB_WindowInfo) - 1
        If $aSB_WindowInfo[$x][0] = $hWnd Then
            $iIndex = $x
            $yChar = $aSB_WindowInfo[$iIndex][3]
            ExitLoop
        EndIf
    Next
    If $iIndex = -1 Then Return 0

    Local $tSCROLLINFO = _GUIScrollBars_GetScrollInfoEx($hWnd, $SB_VERT)
    $Min = DllStructGetData($tSCROLLINFO, "nMin")
    $Max = DllStructGetData($tSCROLLINFO, "nMax")
    $Page = DllStructGetData($tSCROLLINFO, "nPage")
    $yPos = DllStructGetData($tSCROLLINFO, "nPos")
    $Pos = $yPos
    $TrackPos = DllStructGetData($tSCROLLINFO, "nTrackPos")

    Switch $nScrollCode
        Case $SB_TOP
            DllStructSetData($tSCROLLINFO, "nPos", $Min)
        Case $SB_BOTTOM
            DllStructSetData($tSCROLLINFO, "nPos", $Max)
        Case $SB_LINEUP
            DllStructSetData($tSCROLLINFO, "nPos", $Pos - 1)
        Case $SB_LINEDOWN
            DllStructSetData($tSCROLLINFO, "nPos", $Pos + 1)
        Case $SB_PAGEUP
            DllStructSetData($tSCROLLINFO, "nPos", $Pos - $Page)
        Case $SB_PAGEDOWN
            DllStructSetData($tSCROLLINFO, "nPos", $Pos + $Page)
        Case $SB_THUMBTRACK
            DllStructSetData($tSCROLLINFO, "nPos", $TrackPos)
    EndSwitch

    DllStructSetData($tSCROLLINFO, "fMask", $SIF_POS)
    _GUIScrollBars_SetScrollInfo($hWnd, $SB_VERT, $tSCROLLINFO)
    _GUIScrollBars_GetScrollInfo($hWnd, $SB_VERT, $tSCROLLINFO)

    $Pos = DllStructGetData($tSCROLLINFO, "nPos")
    If ($Pos <> $yPos) Then
        _GUIScrollBars_ScrollWindow($hWnd, 0, $yChar * ($yPos - $Pos))
        $yPos = $Pos
    EndIf

    Return $GUI_RUNDEFMSG

EndFunc   ;==>_Scrollbars_WM_VSCROLL

Func _Scrollbars_WM_HSCROLL($hWnd, $Msg, $wParam, $lParam)

    #forceref $Msg, $lParam
    Local $nScrollCode = BitAND($wParam, 0x0000FFFF)
    Local $iIndex = -1, $xChar, $xPos
    Local $Page, $Pos, $TrackPos

    For $x = 0 To UBound($aSB_WindowInfo) - 1
        If $aSB_WindowInfo[$x][0] = $hWnd Then
            $iIndex = $x
            $xChar = $aSB_WindowInfo[$iIndex][2]
            ExitLoop
        EndIf
    Next
    If $iIndex = -1 Then Return 0

    Local $tSCROLLINFO = _GUIScrollBars_GetScrollInfoEx($hWnd, $SB_HORZ)
    $Page = DllStructGetData($tSCROLLINFO, "nPage")
    $xPos = DllStructGetData($tSCROLLINFO, "nPos")
    $Pos = $xPos
    $TrackPos = DllStructGetData($tSCROLLINFO, "nTrackPos")
    Switch $nScrollCode
        Case $SB_LINELEFT
            DllStructSetData($tSCROLLINFO, "nPos", $Pos - 1)
        Case $SB_LINERIGHT
            DllStructSetData($tSCROLLINFO, "nPos", $Pos + 1)
        Case $SB_PAGELEFT
            DllStructSetData($tSCROLLINFO, "nPos", $Pos - $Page)
        Case $SB_PAGERIGHT
            DllStructSetData($tSCROLLINFO, "nPos", $Pos + $Page)
        Case $SB_THUMBTRACK
            DllStructSetData($tSCROLLINFO, "nPos", $TrackPos)
    EndSwitch

    DllStructSetData($tSCROLLINFO, "fMask", $SIF_POS)
    _GUIScrollBars_SetScrollInfo($hWnd, $SB_HORZ, $tSCROLLINFO)
    _GUIScrollBars_GetScrollInfo($hWnd, $SB_HORZ, $tSCROLLINFO)

    $Pos = DllStructGetData($tSCROLLINFO, "nPos")
    If ($Pos <> $xPos) Then _GUIScrollBars_ScrollWindow($hWnd, $xChar * ($xPos - $Pos), 0)

    Return $GUI_RUNDEFMSG

EndFunc   ;==>_Scrollbars_WM_HSCROLL

Func _Scrollbars_WM_MOUSEWHEEL($hWnd, $iMsg, $wParam, $lParam)

    Local $iDirn, $iDelta = BitShift($wParam, 16)

    If BitAND($wParam, 0x0000FFFF) Then ; If Ctrl or Shft pressed move Horz scrollbar
        $iDirn = $SB_LINERIGHT
        If $iDelta > 0 Then $iDirn = $SB_LINELEFT
        For $i = 1 To 10
            _SendMessage($hWnd, $WM_HSCROLL, $iDirn)
        Next
    Else ; Move Vert scrollbar
        $iDirn = $SB_LINEDOWN
        If $iDelta > 0 Then $iDirn = $SB_LINEUP
        _SendMessage($hWnd, $WM_VSCROLL, $iDirn)
    EndIf

    Return $GUI_RUNDEFMSG

EndFunc   ;==>_Scrollbars_WM_MOUSEWHEEL

Func _Scrollbars_WM_MOUSEHWHEEL($hWnd, $iMsg, $wParam, $lParam)

    Local $iDirn, $iDelta = BitShift($wParam, 16)

    Local $iDirn = $SB_LINERIGHT
    If $iDelta > 0 Then $iDirn = $SB_LINELEFT
    For $i = 1 To 10
        _SendMessage($hWnd, $WM_HSCROLL, $iDirn)
    Next

    Return $GUI_RUNDEFMSG

EndFunc   ;==>_Scrollbars_WM_MOUSEHWHEEL