/// <summary>
/// Clips the given polylines to the given clipping region. Using the specified viewport extents, this
/// routine also eliminates duplicate points that would otherwise occur after the viewport transformation.
/// </summary>
/// <typeparam name="P"> Output polyline type. </typeparam>
/// <typeparam name="T"> Input point type. </typeparam>
/// <param name="sz"> Viewport extents. </param>
/// <param name="rc"> Logical clipping rectangle. </param>
/// <param name="polylines"> Input polylines. </param>
/// <param name="convPnt"> Function converting an input point of type T to System.Windows.Point. </param>
/// <param name="addPnt"> Procedure adding a System.Windows.Point to the resulting polyline of type P. </param>
/// <param name="reductionOnly">Specifies that only the reduction should be performed without clipping.</param>
/// <returns> The reduced and optionally clipped polyline. </returns>
public static ICollection <P> ClipPolylineReducePoints <P, T>(Size sz, Rect rc, ICollection <ICollection <T> > polylines, Func <T, Point> convPnt, Action <P, Point> addPnt, bool reductionOnly) where P : class, new()
{
// re-initialize rc, assuring left <= right and top <= bottom
rc = new Rect(Math.Min(rc.Left, rc.Right), Math.Min(rc.Top, rc.Bottom), Math.Abs(rc.Width), Math.Abs(rc.Height));
// create result object storing the clipped lines
var polylineBuilder = new PolylineBuilder <P>(addPnt, new Size(rc.Width / sz.Width, rc.Height / sz.Height));
if (polylines == null)
{
return(polylineBuilder.Polyline);
}
// loop through given polylines
foreach (ICollection <T> polyline in polylines)
{
// enumerator for accessing points
IEnumerator <T> e = polyline?.GetEnumerator();
// fetch first point
if (e == null || !e.MoveNext())
{
continue;
}
// initialize starting point
var p0 = convPnt(e.Current);
// number of points in current polyline
int lastPointIndex = polyline.Count - 1;
// loop through remaining points
for (int pointIndex = 1; e.MoveNext(); ++pointIndex)
{
// fetch end point. p0 and p1 now mark the start and end point of the current line.
var p1 = convPnt(e.Current);
// clip the current line. CohenSutherland.clip returns true, if any section of the current line is visible.
if (reductionOnly || CohenSutherlandClipping.Clip(rc, ref p0, ref p1))
{
// Append current line. Append also does the magic of point reduction and line splitting polylines where necessary.
polylineBuilder.Append(p0, pointIndex == 1, p1, pointIndex == lastPointIndex);
}
// current end point is the next starting point
p0 = convPnt(e.Current);
}
}
// return the polyline
return(polylineBuilder.Polyline);
}