private ScrollBarElement UpdateHoveredItem(ref ControlMetrics Metrics, bool InvalidateIfChanged = true)
{
var CurrentPosition = this.LastMousePosition_ClientCoordinates == null ? ScrollBarElement.None : GetElementAtPosition(this.LastLayoutInfo.Bounds, this.LastLayoutInfo.Horizontal, ref Metrics, this.LastMousePosition_ClientCoordinates.Value);
this.SetHoveredItem(CurrentPosition, InvalidateIfChanged);
return(CurrentPosition);
}
/// <summary>
/// Calculates where the things in the scroll bar are (in pixels).
/// </summary>
private static ControlMetrics GetControlMetrics(int ScrollBarLength, int ScrollBarWidth, int ViewportSize, int TotalScrollableDistance, int ScrollValue)
{
var Metrics = new ControlMetrics();
int ButtonHeight = ScrollBarWidth;
Metrics.TrackStart = ButtonHeight;
Metrics.BottomButtonStart = ScrollBarLength - ButtonHeight;
float ThumbRatio;
if (ViewportSize == 0)
{
ThumbRatio = 0;
}
else
{
ThumbRatio = (float)ViewportSize / (TotalScrollableDistance + ViewportSize);
}
int MinimumThumbSize = ScrollBarWidth;
int TrackSize = Math.Max(0, Metrics.BottomButtonStart - Metrics.TrackStart);
Metrics.ThumbSize = Math.Min(Math.Max(MinimumThumbSize, (int)(TrackSize * ThumbRatio)), TrackSize); // Size of thumb in pixels, proportional to ViewportSize / TotalScrollableDistance
Metrics.TrackSpaceAvailableForThumbMovement = TrackSize - Metrics.ThumbSize;
int ThumbPosRelativeToTrackStart;
if (TotalScrollableDistance == 0)
{
ThumbPosRelativeToTrackStart = 0;
}
else
{
ThumbPosRelativeToTrackStart = (int)((float)ScrollValue / TotalScrollableDistance * Metrics.TrackSpaceAvailableForThumbMovement);
}
Metrics.ThumbStart = ThumbPosRelativeToTrackStart + Metrics.TrackStart;
return(Metrics);
}
/// <summary>
/// It doesn't matter whether it's in screen coordinates or control coordinates as long as both <paramref name="Bounds"/> and <paramref name="Position"/>
/// are in the same reference frame.
/// </summary>
private static ScrollBarElement GetElementAtPosition(Rectangle Bounds, bool Horizontal, ref ControlMetrics Metrics, Point Position)
{
if (!Bounds.Contains(Position))
{
return(ScrollBarElement.None);
}
int y = Horizontal ? Position.X - Bounds.Left : Position.Y - Bounds.Top;
if (y < 0)
{
return(ScrollBarElement.None);
}
if (y < Metrics.TrackStart)
{
return(ScrollBarElement.TopButton);
}
if (y < Metrics.ThumbStart)
{
return(ScrollBarElement.TrackAboveThumb);
}
if (y < Metrics.ThumbStart + Metrics.ThumbSize)
{
return(ScrollBarElement.Thumb);
}
if (y < Metrics.BottomButtonStart)
{
return(ScrollBarElement.TrackBelowThumb);
}
if (y < (Horizontal ? Bounds.Width : Bounds.Height))
{
return(ScrollBarElement.BottomButton);
}
return(ScrollBarElement.None);
}
