372 lines
21 KiB
C#
372 lines
21 KiB
C#
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//
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// ScanSegmentTree.cs
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// MSAGL class for visibility scan segment tree for Rectilinear Edge Routing.
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//
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// Copyright Microsoft Corporation.
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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using Microsoft.Msagl.Core.DataStructures;
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using Microsoft.Msagl.Core.Geometry;
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namespace Microsoft.Msagl.Routing.Rectilinear {
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using DebugHelpers;
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internal class ScanSegmentTree : IComparer<ScanSegment> {
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internal ScanDirection ScanDirection { get; private set; }
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private readonly RbTree<ScanSegment> segmentTree;
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// Temporary variables for lookup.
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private readonly ScanSegment lookupSegment = new ScanSegment(new Point(0, 0), new Point(0, 1)); // dummy values avoid AF; will be overwritten
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readonly Func<ScanSegment, bool> findIntersectorPred;
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readonly Func<ScanSegment, bool> findPointPred;
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internal ScanSegmentTree(ScanDirection scanDir) {
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ScanDirection = scanDir;
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this.segmentTree = new RbTree<ScanSegment>(this);
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this.findIntersectorPred = new Func<ScanSegment, bool>(this.CompareIntersector);
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this.findPointPred = new Func<ScanSegment, bool>(this.CompareToPoint);
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}
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internal IEnumerable<ScanSegment> Segments { get { return this.segmentTree; } }
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// If the seg is already in the tree it returns that instance, else it inserts the new
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// seg and returns that.
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internal RBNode<ScanSegment> InsertUnique(ScanSegment seg) {
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// RBTree's internal operations on insert/remove etc. mean the node can't cache the
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// RBNode returned by insert(); instead we must do find() on each call. But we can
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// use the returned node to get predecessor/successor.
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AssertValidSegmentForInsertion(seg);
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var node = this.segmentTree.Find(seg);
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if (null != node) {
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Debug.Assert(seg.IsOverlapped == node.Item.IsOverlapped, "Existing node found with different isOverlapped");
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return node;
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}
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return this.segmentTree.Insert(seg);
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}
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[Conditional("DEBUG")]
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[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic")]
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void AssertValidSegmentForInsertion(ScanSegment seg) {
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Debug.Assert((seg.End.X >= seg.Start.X) && (seg.End.Y >= seg.Start.Y), "Reversed direction in ScanSegment");
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Debug.Assert(ScanDirection.IsFlat(seg.Start, seg.End), "non-flat segment cannot be inserted");
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}
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internal void Remove(ScanSegment seg) {
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Debug.Assert(seg.IsVertical == ScanDirection.IsVertical, "seg.IsVertical != ScanDirection.IsVertical");
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this.segmentTree.Remove(seg);
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}
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internal ScanSegment Find(Point start, Point end) {
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Debug.Assert(PointComparer.Equal(start, end) || !ScanDirection.IsPerpendicular(start, end)
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, "perpendicular segment passed");
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this.lookupSegment.Update(start, end);
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RBNode<ScanSegment> node = this.segmentTree.Find(this.lookupSegment);
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if ((null != node) && PointComparer.Equal(node.Item.End, end)) {
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return node.Item;
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}
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return null;
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}
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// Find the lowest perpendicular scanseg that intersects the segment endpoints.
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internal ScanSegment FindLowestIntersector(Point start, Point end) {
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var node = FindLowestIntersectorNode(start, end);
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return (null != node) ? node.Item : null;
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}
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internal RBNode<ScanSegment> FindLowestIntersectorNode(Point start, Point end) {
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Debug.Assert(ScanDirection.IsPerpendicular(start, end), "non-perpendicular segment passed");
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// Find the last segment that starts at or before 'start'.
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this.lookupSegment.Update(start, start);
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RBNode<ScanSegment> node = this.segmentTree.FindLast(this.findIntersectorPred);
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// We have a segment that intersects start/end, or one that ends before 'start' and thus we
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// must iterate to find the lowest bisector. TODOperf: see how much that iteration costs us
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// (here and Highest); consider a BSP tree or interval tree (maybe 2-d RBTree for updatability).
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if (PointComparer.Equal(start, end)) {
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if ((null != node) && (ScanDirection.Compare(node.Item.End, start) < 0)) {
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node = null;
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}
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}
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else {
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this.lookupSegment.Update(start, end);
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while ((null != node) && !node.Item.IntersectsSegment(this.lookupSegment)) {
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// If the node segment starts after 'end', no intersection was found.
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if (ScanDirection.Compare(node.Item.Start, end) > 0) {
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return null;
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}
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node = this.segmentTree.Next(node);
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}
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}
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return node;
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}
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// Find the highest perpendicular scanseg that intersects the segment endpoints.
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internal ScanSegment FindHighestIntersector(Point start, Point end) {
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Debug.Assert(ScanDirection.IsPerpendicular(start, end), "non-perpendicular segment passed");
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// Find the last segment that starts at or before 'end'.
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this.lookupSegment.Update(end, end);
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RBNode<ScanSegment> node = this.segmentTree.FindLast(this.findIntersectorPred);
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// Now we either have a segment that intersects start/end, or one that ends before
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// 'end' and need to iterate to find the highest bisector.
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if (PointComparer.Equal(start, end)) {
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if ((null != node) && (ScanDirection.Compare(node.Item.End, start) < 0)) {
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node = null;
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}
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}
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else {
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this.lookupSegment.Update(start, end);
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while ((null != node) && !node.Item.IntersectsSegment(this.lookupSegment)) {
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// If the node segment ends before 'start', no intersection was found.
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if (ScanDirection.Compare(node.Item.End, start) < 0) {
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return null;
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}
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node = this.segmentTree.Previous(node);
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}
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}
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return (null != node) ? node.Item : null;
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}
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bool CompareIntersector(ScanSegment seg) {
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// We're looking for the last segment that starts before LookupSegment.Start.
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return (ScanDirection.Compare(seg.Start, this.lookupSegment.Start) <= 0);
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}
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internal ScanSegment FindSegmentContainingPoint(Point location, bool allowUnfound) {
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return FindSegmentOverlappingPoints(location, location, allowUnfound);
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}
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internal ScanSegment FindSegmentOverlappingPoints(Point start, Point end, bool allowUnfound) {
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this.lookupSegment.Update(start, end);
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RBNode<ScanSegment> node = this.segmentTree.FindFirst(this.findPointPred);
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// If we had any segments in the tree that end after 'start', node has the first one.
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// Now we need to that it starts before 'end'. ScanSegment.CompareToPointPositionFullLength
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// asserts the point is on the segment which we don't want to require here, so
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// compare the endpoints directly.
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if (null != node) {
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ScanSegment seg = node.Item;
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if (ScanDirection.Compare(seg.Start, end) <= 0) {
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return seg;
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}
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}
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// Not found.
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if (!allowUnfound) {
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Debug.Assert(false, "Could not find expected segment");
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}
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return null;
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}
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bool CompareToPoint(ScanSegment treeSeg) {
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// Test if treeSeg overlaps the LookupSegment.Start point. We're using FindFirst,
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// so we'll just return false for everything that ends before the point and true for anything
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// that ends at or after it, then the caller will verify overlap.
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return (ScanDirection.Compare(treeSeg.End, this.lookupSegment.Start) >= 0);
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}
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RBNode<ScanSegment> MergeAndRemoveNextNode(ScanSegment currentSegment, RBNode<ScanSegment> nextSegNode) {
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// Merge at the ends only - if we're here, start will be the same or greater.
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if (-1 == ScanDirection.Compare(currentSegment.End, nextSegNode.Item.End)) {
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currentSegment.Update(currentSegment.Start, nextSegNode.Item.End);
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}
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// Removing the node can revise the tree's RBNodes internally so re-get the current segment.
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currentSegment.MergeGroupBoundaryCrossingList(nextSegNode.Item.GroupBoundaryPointAndCrossingsList);
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this.segmentTree.DeleteNodeInternal(nextSegNode);
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return this.segmentTree.Find(currentSegment);
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}
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internal void MergeSegments() {
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// As described in the doc, hintScanSegment handles all the non-overlapped non-reflection cases.
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DevTraceInfo(1, "{0} ScanSegmentTree MergeSegments, count = {1}"
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, ScanDirection.IsHorizontal ? "Horizontal" : "Vertical", this.segmentTree.Count);
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if (this.segmentTree.Count < 2) {
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return;
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}
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RBNode<ScanSegment> currentSegNode = this.segmentTree.TreeMinimum();
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RBNode<ScanSegment> nextSegNode = this.segmentTree.Next(currentSegNode);
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for ( ; null != nextSegNode; nextSegNode = this.segmentTree.Next(currentSegNode)) {
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DevTraceInfo(2, "Current {0} Next {1}", currentSegNode.Item, nextSegNode.Item);
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int cmp = ScanDirection.Compare(nextSegNode.Item.Start, currentSegNode.Item.End);
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switch (cmp) {
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case 1:
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// Next segment starts after the current one.
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currentSegNode = nextSegNode;
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break;
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case 0:
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if (nextSegNode.Item.IsOverlapped == currentSegNode.Item.IsOverlapped) {
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// Overlapping is the same, so merge. Because the ordering in the tree is that
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// same-Start nodes are ordered by longest-End first, this will retain the tree ordering.
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DevTraceInfo(2, " (merged; start-at-end with same overlap)");
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currentSegNode = MergeAndRemoveNextNode(currentSegNode.Item, nextSegNode);
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}
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else {
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// Touching start/end with differing IsOverlapped so they need a connecting vertex.
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DevTraceInfo(2, " (marked with NeedFinalOverlapVertex)");
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currentSegNode.Item.NeedEndOverlapVertex = true;
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nextSegNode.Item.NeedStartOverlapVertex = true;
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currentSegNode = nextSegNode;
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}
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break;
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default: // -1 == cmp
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// nextSegNode.Item.Start is before currentSegNode.Item.End.
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Debug.Assert((nextSegNode.Item.Start != currentSegNode.Item.Start)
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, "Identical segments are not allowed, and longer ones must come first");
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// Because longer segments are ordered before shorter ones at the same start position,
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// nextSegNode.Item must be a duplicate segment or is partially or totally overlapped.
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// In the case of reflection lookahead segments, the side-intersection calculated from
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// horizontal vs. vertical directions may be slightly different along the parallel
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// coordinate from an overlapped segment, so let non-overlapped win that disagreement.
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if (currentSegNode.Item.IsOverlapped != nextSegNode.Item.IsOverlapped) {
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Debug.Assert(ApproximateComparer.CloseIntersections(currentSegNode.Item.End, nextSegNode.Item.Start)
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, "Segments share a span with different IsOverlapped");
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if (currentSegNode.Item.IsOverlapped) {
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// If the Starts are different, then currentSegNode is the only item at its
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// start, so we don't need to re-insert. Otherwise, we need to remove it and
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// re-find nextSegNode's side.
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if (currentSegNode.Item.Start == nextSegNode.Item.Start) {
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// currentSegNode is a tiny overlapped segment between two non-overlapped segments (so
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// we'll have another merge later, when we hit the other non-overlapped segment).
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// Notice reversed params. TestNote: No longer have repro with the change to convex hulls;
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// this may no longer happen since overlapped edges will now always be inside rectangular
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// obstacles so there are no angled-side calculations.
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currentSegNode = MergeAndRemoveNextNode(nextSegNode.Item, currentSegNode);
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DevTraceInfo(2, " (identical starts so discarding isOverlapped currentSegNode)");
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}
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else {
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currentSegNode.Item.Update(currentSegNode.Item.Start, nextSegNode.Item.Start);
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DevTraceInfo(2, " (trimming isOverlapped currentSegNode to {0})", currentSegNode.Item);
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currentSegNode = nextSegNode;
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}
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}
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else {
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if (currentSegNode.Item.End == nextSegNode.Item.End) {
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// nextSegNode is a tiny non-overlapped segment between two overlapped segments (so
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// we'll have another merge later, when we hit the other non-overlapped segment).
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// TestNote: No longer have repro with the change to convex hulls;
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// this may no longer happen since overlapped edges will now always be inside rectangular
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// obstacles so there are no angled-side calculations.
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currentSegNode = MergeAndRemoveNextNode(currentSegNode.Item, nextSegNode);
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DevTraceInfo(2, " (identical ends so discarding isOverlapped currentSegNode)");
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}
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else {
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// Remove nextSegNode, increment its start to be after currentSegment, re-insert nextSegNode, and
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// re-find currentSegNode (there may be more segments between nextSegment.Start and currentSegment.End).
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ScanSegment nextSegment = nextSegNode.Item;
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ScanSegment currentSegment = currentSegNode.Item;
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this.segmentTree.DeleteNodeInternal(nextSegNode);
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nextSegment.Update(currentSegment.End, nextSegment.End);
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this.segmentTree.Insert(nextSegment);
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nextSegment.TrimGroupBoundaryCrossingList();
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DevTraceInfo(2, " (trimming isOverlapped nextSegNode to {0})", nextSegment);
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currentSegNode = this.segmentTree.Find(currentSegment);
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}
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}
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break;
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}
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// Overlaps match so do a normal merge operation.
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DevTraceInfo(2, " (merged; start-before-end)");
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currentSegNode = MergeAndRemoveNextNode(currentSegNode.Item, nextSegNode);
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break;
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} // endswitch
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} // endfor
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#if DEVTRACE
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DevTraceInfo(1, "{0} ScanSegmentTree after MergeSegments, count = {1}"
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, ScanDirection.IsHorizontal ? "Horizontal" : "Vertical", this.segmentTree.Count);
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if (this.scanSegmentVerify.IsLevel(1)) {
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DevTraceInfo(1, "{0} ScanSegmentTree Consistency Check"
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, ScanDirection.IsHorizontal ? "Horizontal" : "Vertical");
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bool retval = true;
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RBNode<ScanSegment> prevSegNode = this.segmentTree.TreeMinimum();
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currentSegNode = this.segmentTree.Next(prevSegNode);
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while (null != currentSegNode) {
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DevTraceInfo(4, currentSegNode.Item.ToString());
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// We should only have end-to-end touching, and that only if differing IsOverlapped.
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if ( (-1 != Compare(prevSegNode.Item, currentSegNode.Item))
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|| (1 != ScanDirection.Compare(currentSegNode.Item.Start, prevSegNode.Item.Start)
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|| ((0 == ScanDirection.Compare(currentSegNode.Item.Start, prevSegNode.Item.End))
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&& (currentSegNode.Item.IsOverlapped == prevSegNode.Item.IsOverlapped)))) {
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this.scanSegmentTrace.WriteError(0, "Segments are not strictly increasing:");
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this.scanSegmentTrace.WriteFollowup(0, prevSegNode.Item.ToString());
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this.scanSegmentTrace.WriteFollowup(0, currentSegNode.Item.ToString());
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retval = false;
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}
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prevSegNode = currentSegNode;
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currentSegNode = this.segmentTree.Next(currentSegNode);
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}
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Debug.Assert(retval, "ScanSegments are not strictly increasing");
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}
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#endif // DEVTRACE
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}
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#region IComparer<ScanSegment>
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/// <summary>
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/// For ordering the line segments inserted by the ScanLine. Assuming vertical sweep (sweeping up from
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/// bottom, scanning horizontally) then order ScanSegments first by lowest Y coord, then by lowest X coord.
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/// </summary>
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/// <param name="first"></param>
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/// <param name="second"></param>
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/// <returns></returns>
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public int Compare(ScanSegment first, ScanSegment second) {
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if (first == second)
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return 0;
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if (first == null)
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return -1;
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if (second == null)
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return 1;
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||
|
|
|
||
|
|
// This orders on both axes.
|
||
|
|
int cmp = ScanDirection.Compare(first.Start, second.Start);
|
||
|
|
if (0 == cmp) {
|
||
|
|
// Longer segments come first, to make overlap removal easier.
|
||
|
|
cmp = -ScanDirection.Compare(first.End, second.End);
|
||
|
|
}
|
||
|
|
return cmp;
|
||
|
|
}
|
||
|
|
#endregion // IComparer<ScanSegment>
|
||
|
|
|
||
|
|
#region DevTrace
|
||
|
|
#if DEVTRACE
|
||
|
|
readonly DevTrace scanSegmentTrace = new DevTrace("Rectilinear_ScanSegmentTrace", "ScanSegments");
|
||
|
|
readonly DevTrace scanSegmentVerify = new DevTrace("Rectilinear_ScanSegmentVerify");
|
||
|
|
#endif // DEVTRACE
|
||
|
|
|
||
|
|
[Conditional("DEVTRACE")]
|
||
|
|
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic")]
|
||
|
|
void DevTraceInfo(int verboseLevel, string format, params object[] args) {
|
||
|
|
#if DEVTRACE
|
||
|
|
this.scanSegmentTrace.WriteLineIf(DevTrace.Level.Info, verboseLevel, format, args);
|
||
|
|
#endif // DEVTRACE
|
||
|
|
}
|
||
|
|
|
||
|
|
[Conditional("DEVTRACE")]
|
||
|
|
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic")]
|
||
|
|
internal void DevTraceVerifyVisibility() {
|
||
|
|
#if DEVTRACE
|
||
|
|
if (this.scanSegmentVerify.IsLevel(1)) {
|
||
|
|
DevTraceInfo(1, "Beginning {0} ScanSegmentTree VisibilityVertex Check..."
|
||
|
|
, ScanDirection.IsHorizontal ? "Horizontal" : "Vertical");
|
||
|
|
bool retval = true;
|
||
|
|
for (RBNode<ScanSegment> segNode = this.segmentTree.TreeMinimum(); null != segNode; segNode = this.segmentTree.Next(segNode)) {
|
||
|
|
if (null == segNode.Item.LowestVisibilityVertex) {
|
||
|
|
this.scanSegmentTrace.WriteError(0, "Segment has no VisibilityVertex: {0}", segNode.Item.ToString());
|
||
|
|
retval = false;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
DevTraceInfo(1, "{0} ScanSegmentTree VisibilityVertex Check complete: status {1}"
|
||
|
|
, ScanDirection.IsHorizontal ? "Horizontal" : "Vertical", retval ? "pass" : "fail");
|
||
|
|
Debug.Assert(retval, "One or more ScanSegments do not have a VisibilityVertex");
|
||
|
|
}
|
||
|
|
#endif // DEVTRACE
|
||
|
|
}
|
||
|
|
#endregion // DevTrace
|
||
|
|
}
|
||
|
|
}
|