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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Collections; // for ArrayList
using System.Windows; // for Rect WindowsBase.dll
namespace Microsoft.Internal.AlphaFlattener
{
internal class Coordinate
{
public double value;
public int index;
public bool active;
public Coordinate top;
public Coordinate bottom;
public Coordinate(double v, int i)
{
value = v;
index = i;
}
}
internal class CoordinateSearcher : IComparer
{
int IComparer.Compare(Object x, Object y)
{
double vx = ((Coordinate)x).value;
double vy = (double)y;
return vx.CompareTo(vy);
}
}
internal class SegmentTree
{
double _min;
double _max;
SegmentTree _left;
SegmentTree _right;
List<int> _sList;
/// <summary>
/// Build a balanced Segment Tree from a sorted intersection list
/// </summary>
/// <param name="coord"></param>
/// <param name="from"></param>
/// <param name="count"></param>
public SegmentTree(Coordinate[] coord, int from, int count)
{
Debug.Assert(count >= 2);
_min = coord[from].value;
_max = coord[from + count - 1].value;
if (count > 2)
{
int half = count / 2 + 1;
_left = new SegmentTree(coord, from, half);
_right = new SegmentTree(coord, from + half - 1, count - half + 1);
}
}
public void Remove(int index, double x0, double x1)
{
if ((_min >= x0) && (_max <= x1)) // [_min.._max] is within [x0..x1]
{
if (_sList != null)
{
_sList.Remove(index);
}
}
else
{
if ((_left != null) && (x0 <= _left._max) && (x1 >= _left._min)) // overlap with left
{
_left.Remove(index, x0, x1);
}
if ((_right != null) && (x0 <= _right._max) && (x1 >= _right._min)) // overlap with right
{
_right.Remove(index, x0, x1);
}
}
}
public void Insert(int index, double x0, double x1)
{
if ((_min >= x0) && (_max <= x1)) // [_min.._max] is within [x0..x1]
{
if (_sList == null)
{
_sList = new List<int>();
}
_sList.Add(index);
}
else
{
if ((_left != null) && (x0 <= _left._max) && (x1 >= _left._min)) // overlap with left
{
_left.Insert(index, x0, x1);
}
if ((_right != null) && (x0 <= _right._max) && (x1 >= _right._min)) // overlap with right
{
_right.Insert(index, x0, x1);
}
}
}
public void ReportIntersection(DisplayList dl, int index, double x)
{
if (_sList != null)
{
foreach (int i in _sList)
{
if (index != i)
{
dl.ReportOverlapping(index, i);
}
}
}
if ((_left != null) && (x >= _left._min) && (x <= _left._max))
{
_left.ReportIntersection(dl, index, x);
}
if ((_right != null) && (x >= _right._min) && (x <= _right._max))
{
_right.ReportIntersection(dl, index, x);
}
}
}
internal class RectangleIntersection
{
protected Coordinate[] _xCoord; // = null;
protected int _xCount; // = 0;
protected Coordinate[] _yCoord; // = null;
protected int _yCount; // = 0;
static Coordinate[] RemoveDuplication(Coordinate[] values)
{
int last = 0;
int len = values.Length;
double val = values[last].value;
for (int i = 1; i < len; i++)
{
if (! Double.Equals(values[i].value, val))
{
last++;
val = values[i].value;
}
}
if (len != (last + 1))
{
Coordinate[] newvalues = new Coordinate[last + 1];
last = 0;
newvalues[0] = values[0];
for (int i = 1; i < len; i++)
{
if (! Double.Equals(values[i].value, newvalues[last].value))
{
last++;
newvalues[last] = values[i];
}
}
return newvalues;
}
else
{
return values;
}
}
private void AddPoint(int i, int index, double x, double y)
{
Coordinate cx = new Coordinate(x, index);
Coordinate cy = new Coordinate(y, index);
_xCoord[i] = cx;
_yCoord[i] = cy;
}
private void SortEndPoints(DisplayList dl, int count)
{
_xCoord = new Coordinate[2 * count + 2];
_yCoord = new Coordinate[2 * count + 2];
AddPoint(0, -1, Double.MinValue, Double.MinValue);
int p = 1;
for (int i = 0; i < count; i++)
{
Rect r = dl[i];
AddPoint(p, i, r.Left, r.Top);
AddPoint(p + 1, i, r.Right, r.Bottom);
_xCoord[p].top = _yCoord[p];
_xCoord[p].bottom = _yCoord[p + 1];
_xCoord[p + 1].top = _yCoord[p];
_xCoord[p + 1].bottom = _yCoord[p + 1];
p += 2;
}
AddPoint(p, count + 1, Double.MaxValue, Double.MaxValue);
Array.Sort(_xCoord, (x, y) => x.value.CompareTo(y.value));
_xCount = _xCoord.Length;
Array.Sort(_yCoord, (x, y) => x.value.CompareTo(y.value));
_yCount = _yCoord.Length;
}
// Input N rectangles -> 2N vertical line segment, 2N horizontal line segments
// Output all true intersections rectangles
private void OrthogonalLineSegmentIntersection(DisplayList dl)
{
// Sweep through sorted x coordiates from left to right, skipping MinValue/MaxValue
for (int i = 1; i < _xCount - 1; i++)
{
Coordinate c = _xCoord[i];
bool left = Double.Equals(c.value, dl[c.index].Left);
// Left endpoint => insertion into range tree
// Right endpoint => delection from range tree
c.top.active = left;
c.bottom.active = left;
// Vertical segment [y0..y1] => report [y0..y1] AND range tree
double y0 = c.top.value;
double y1 = c.bottom.value;
int p = Array.BinarySearch(_yCoord, y0, new CoordinateSearcher());
if (p >= 0)
{
do
{
if ((_yCoord[p].active) && (c.index != _yCoord[p].index))
{
dl.ReportOverlapping(c.index, _yCoord[p].index);
// Console.WriteLine("{0} {1} intersects ({2},{3})", c.index, _yCoord[p].index, c.value, _yCoord[p].value);
}
p++;
}
while (_yCoord[p].value <= y1);
}
}
}
// Input N rectangles and points (top-left corner of rectangle)
// Output all R(r, p) where point p is within rectangle r
private void BatchedRangeSearch(DisplayList dl)
{
// 1) Sort all points and left/right rectangle sides w.r.t. x-coordinate
// 2) Sweep left-to-right while storing y-intervals of rectangles intersecting
// the sweepline in a segment tree T
// 2.1) Left side => insert interval into T
// 2.2) Right side => delete interval from T
// 2.3) Point (x, y) stabbing query report all [y1,y2] where y is in [y1..y2]
Coordinate[] uniqueY = RemoveDuplication(_yCoord);
SegmentTree st = new SegmentTree(uniqueY, 0, uniqueY.Length);
// Sweep through sorted x coordiates from left to right, skipping MinValue/MaxValue
for (int i = 1; i < _xCount - 1; i++)
{
Coordinate c = _xCoord[i];
double y0 = c.top.value;
double y1 = c.bottom.value;
if (Double.Equals(c.value, dl[c.index].Left))
{
st.Insert(c.index, y0, y1);
st.ReportIntersection(dl, c.index, y0);
}
else
{
st.Remove(c.index, y0, y1);
}
}
}
public void CalculateIntersections(DisplayList dl, int count)
{
SortEndPoints(dl, count);
OrthogonalLineSegmentIntersection(dl);
BatchedRangeSearch(dl);
}
#if UNIT_TEST
internal static void UnitTest()
{
Console.WriteLine("RectangleIntersection unit test");
DisplayList dl = new DisplayList(8.5 * 96, 11 * 96);
dl.Add( 3, 8, 6, 36);
dl.Add(25, 34, 34, 38);
dl.Add(33, 37, 21, 36);
dl.Add(21, 38, 23, 27);
dl.Add( 6, 26, 3, 8);
dl.Add(31, 35, 15, 19);
dl.Add(23, 38, 11, 14);
dl.Add(16, 22, 3.5, 7.5);
RectangleIntersection ri = new RectangleIntersection();
ri.CalculateIntersections(dl);
}
#endif
}
}
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