#7 vslider with inverse direction

[Amiga Lemming]

I propose to extend vslider (and hslider) to reverse the value direction, if minimum and maximum value are swapped.

:::Haskell
wxSL_INVERSE :: Int
wxSL_INVERSE = 0x1000

vslider :: Window a -> Bool -> Int -> Int -> [Prop (Slider ())] -> IO (Slider ())
vslider parentW showLabels top bottom props =
  let (minV, maxV, dirFlags) =
    if top < bottom
    then (top, bottom, 0)
    else (bottom, top, wxSL_INVERSE)
  in sliderEx parentW minV maxV (wxVERTICAL .+. dirFlags .+. (if showLabels then wxSL_LABELS else 0)) props

At least, wxSL_INVERSE should be defined.

[Henk-Jan van Tuyl]

Changed formatting