public override void Recalculate()
{
// TODO: clean up this mess
var upY = Parent.Bounds.Top + Parent.BorderSize;
var downY = Parent.Bounds.Top + Parent.Height - Ui.ScrollBar.DownArrow.Height - BorderSize;
var bgHeight = downY - upY - Ui.ScrollBar.UpArrow.Height;
var x = _border switch
{
Border.Left => Parent.Bounds.Left + Parent.BorderSize + _horizontalOffset,
Border.Right => Parent.Bounds.Left + Parent.Width - Ui.ScrollBar.UpArrow.Width -
Parent.BorderSize + _horizontalOffset,
_ => throw new ArgumentOutOfRangeException()
};
var scrollPartHeight = Ui.ScrollBar.UpArrow.Height;
var upArrowRect = new Rectangle(x, upY, Scroll.Width, scrollPartHeight);
_upArrow.SetRect(upArrowRect);
var downArrowRect = new Rectangle(x, downY, Scroll.Width, scrollPartHeight);
_downArrow.SetRect(downArrowRect);
var staticBgHeight = Ui.ScrollBar.VerticalBackground.Height;
_backgroundRects = Parts.CreateVertical(bgHeight, staticBgHeight, x,
upY + Ui.ScrollBar.UpArrow.Height,
Scroll.Width);
var parent = (ICanHaveVerticalScrollBar)Parent;
var midHeight = CalculateHeightOfMiddlePartOfScrollBar(parent, bgHeight);
var fullMidBarHeight = midHeight + BarEndsHeight * 2;
var oneScrollHeight =
parent.VerticalItemCount <= parent.VerticalMaxVisibleItems
? 0
: (float)(bgHeight - fullMidBarHeight) / parent.VerticalMaxScrollIndex;
_draggable.SetMinimumDragDistance((int)oneScrollHeight);
_dragMultiplier = (float)Math.Max(Math.Ceiling(1 / oneScrollHeight), 1);
var barOffset = (int)Math.Ceiling(oneScrollHeight * parent.VerticalScrollIndex);
var barStartY = barOffset + upY + Ui.ScrollBar.UpArrow.Height;
_barUpRect = new Rectangle(x, barStartY,
Scroll.Width,
Ui.ScrollBar.VerticalForegroundStart.Height);
var midPos = barStartY +
Ui.ScrollBar.VerticalForegroundStart.Height;
_barMiddleRects = Parts.CreateVertical(midHeight,
Ui.ScrollBar.VerticalForegroundMiddle.Height, x, midPos, Scroll.Width);
_barDownRect = new Rectangle(x, midPos + midHeight,
Scroll.Width,
Ui.ScrollBar.VerticalForegroundEnd.Height);
_barHitBox = new Rectangle(x, barStartY, Scroll.Width, fullMidBarHeight);
_bgHitBox = new Rectangle(x, upY + scrollPartHeight, Scroll.Width, bgHeight);
_draggable.SetRect(_barHitBox);
}