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//-----------------------------------------------------------------------
// <copyright file="ErasingStroke.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------
//#define POINTS_FILTER_TRACE
using System;
using System.Windows;
using System.Windows.Ink;
using System.Windows.Media;
using System.Collections.Generic;
namespace MS.Internal.Ink
{
#region ErasingStroke
/// <summary>
/// This class represents a contour of an erasing stroke, and provides
/// internal API for static and incremental stroke_contour vs stroke_contour
/// hit-testing.
/// </summary>
internal class ErasingStroke
{
#region Constructors
/// <summary>
/// Constructor for incremental erasing
/// </summary>
/// <param name="erasingShape">The shape of the eraser's tip</param>
internal ErasingStroke(StylusShape erasingShape)
{
System.Diagnostics.Debug.Assert(erasingShape != null);
_nodeIterator = new StrokeNodeIterator(erasingShape);
}
/// <summary>
/// Constructor for static (atomic) erasing
/// </summary>
/// <param name="erasingShape">The shape of the eraser's tip</param>
/// <param name="path">the spine of the erasing stroke</param>
internal ErasingStroke(StylusShape erasingShape, IEnumerable<Point> path)
: this(erasingShape)
{
MoveTo(path);
}
#endregion
#region API
/// <summary>
/// Generates stroke nodes along a given path.
/// Drops any previously genererated nodes.
/// </summary>
/// <param name="path"></param>
internal void MoveTo(IEnumerable<Point> path)
{
System.Diagnostics.Debug.Assert((path != null) && (IEnumerablePointHelper.GetCount(path) != 0));
Point[] points = IEnumerablePointHelper.GetPointArray(path);
if (_erasingStrokeNodes == null)
{
_erasingStrokeNodes = new List<StrokeNode>(points.Length);
}
else
{
_erasingStrokeNodes.Clear();
}
_bounds = Rect.Empty;
_nodeIterator = _nodeIterator.GetIteratorForNextSegment(points.Length > 1 ? FilterPoints(points) : points);
for (int i = 0; i < _nodeIterator.Count; i++)
{
StrokeNode strokeNode = _nodeIterator[i];
_bounds.Union(strokeNode.GetBoundsConnected());
_erasingStrokeNodes.Add(strokeNode);
}
#if POINTS_FILTER_TRACE
_totalPointsAdded += path.Length;
System.Diagnostics.Debug.WriteLine(String.Format("Total Points added: {0} screened: {1} collinear screened: {2}", _totalPointsAdded, _totalPointsScreened, _collinearPointsScreened));
#endif
}
/// <summary>
/// Returns the bounds of the eraser's last move.
/// </summary>
/// <value></value>
internal Rect Bounds { get { return _bounds; } }
/// <summary>
/// Hit-testing for stroke erase scenario.
/// </summary>
/// <param name="iterator">the stroke nodes to iterate</param>
/// <returns>true if the strokes intersect, false otherwise</returns>
internal bool HitTest(StrokeNodeIterator iterator)
{
System.Diagnostics.Debug.Assert(iterator != null);
if ((_erasingStrokeNodes == null) || (_erasingStrokeNodes.Count == 0))
{
return false;
}
Rect inkSegmentBounds = Rect.Empty;
for (int i = 0; i < iterator.Count; i++)
{
StrokeNode inkStrokeNode = iterator[i];
Rect inkNodeBounds = inkStrokeNode.GetBounds();
inkSegmentBounds.Union(inkNodeBounds);
if (inkSegmentBounds.IntersectsWith(_bounds))
{
//
foreach (StrokeNode erasingStrokeNode in _erasingStrokeNodes)
{
if (inkSegmentBounds.IntersectsWith(erasingStrokeNode.GetBoundsConnected())
&& erasingStrokeNode.HitTest(inkStrokeNode))
{
return true;
}
}
}
}
return false;
}
/// <summary>
/// Hit-testing for point erase.
/// </summary>
/// <param name="iterator"></param>
/// <param name="intersections"></param>
/// <returns></returns>
internal bool EraseTest(StrokeNodeIterator iterator, List<StrokeIntersection> intersections)
{
System.Diagnostics.Debug.Assert(iterator != null);
System.Diagnostics.Debug.Assert(intersections != null);
intersections.Clear();
List<StrokeFIndices> eraseAt = new List<StrokeFIndices>();
if ((_erasingStrokeNodes == null) || (_erasingStrokeNodes.Count == 0))
{
return false;
}
Rect inkSegmentBounds = Rect.Empty;
for (int x = 0; x < iterator.Count; x++)
{
StrokeNode inkStrokeNode = iterator[x];
Rect inkNodeBounds = inkStrokeNode.GetBounds();
inkSegmentBounds.Union(inkNodeBounds);
if (inkSegmentBounds.IntersectsWith(_bounds))
{
//
int index = eraseAt.Count;
foreach (StrokeNode erasingStrokeNode in _erasingStrokeNodes)
{
if (false == inkSegmentBounds.IntersectsWith(erasingStrokeNode.GetBoundsConnected()))
{
continue;
}
StrokeFIndices fragment = inkStrokeNode.CutTest(erasingStrokeNode);
if (fragment.IsEmpty)
{
continue;
}
// Merge it with the other results for this ink segment
bool inserted = false;
for (int i = index; i < eraseAt.Count; i++)
{
StrokeFIndices lastFragment = eraseAt[i];
if (fragment.BeginFIndex < lastFragment.EndFIndex)
{
// If the fragments overlap, merge them
if (fragment.EndFIndex > lastFragment.BeginFIndex)
{
fragment = new StrokeFIndices(
Math.Min(lastFragment.BeginFIndex, fragment.BeginFIndex),
Math.Max(lastFragment.EndFIndex, fragment.EndFIndex));
// If the fragment doesn't go beyond lastFragment, break
if ((fragment.EndFIndex <= lastFragment.EndFIndex) || ((i + 1) == eraseAt.Count))
{
inserted = true;
eraseAt[i] = fragment;
break;
}
else
{
eraseAt.RemoveAt(i);
i--;
}
}
// insert otherwise
else
{
eraseAt.Insert(i, fragment);
inserted = true;
break;
}
}
}
// If not merged nor inserted, add it to the end of the list
if (false == inserted)
{
eraseAt.Add(fragment);
}
// Break out if the entire ink segment is hit - {BeforeFirst, AfterLast}
if (eraseAt[eraseAt.Count - 1].IsFull)
{
break;
}
}
// Merge inter-segment overlapping fragments
if ((index > 0) && (index < eraseAt.Count))
{
StrokeFIndices lastFragment = eraseAt[index - 1];
if (DoubleUtil.AreClose(lastFragment.EndFIndex, StrokeFIndices.AfterLast) )
{
if (DoubleUtil.AreClose(eraseAt[index].BeginFIndex, StrokeFIndices.BeforeFirst))
{
lastFragment.EndFIndex = eraseAt[index].EndFIndex;
eraseAt[index - 1] = lastFragment;
eraseAt.RemoveAt(index);
}
else
{
lastFragment.EndFIndex = inkStrokeNode.Index;
eraseAt[index - 1] = lastFragment;
}
}
}
}
// Start next ink segment
inkSegmentBounds = inkNodeBounds;
}
if (eraseAt.Count != 0)
{
foreach (StrokeFIndices segment in eraseAt)
{
intersections.Add(new StrokeIntersection(segment.BeginFIndex, StrokeFIndices.AfterLast,
StrokeFIndices.BeforeFirst, segment.EndFIndex));
}
}
return (eraseAt.Count != 0);
}
#endregion
#region private API
private Point[] FilterPoints(Point[] path)
{
System.Diagnostics.Debug.Assert(path.Length > 1);
Point back2, back1;
int i;
List<Point> newPath = new List<Point>();
if (_nodeIterator.Count == 0)
{
newPath.Add(path[0]);
newPath.Add(path[1]);
back2 = path[0];
back1 = path[1];
i = 2;
}
else
{
newPath.Add(path[0]);
back2 = _nodeIterator[_nodeIterator.Count - 1].Position;
back1 = path[0];
i = 1;
}
while (i < path.Length)
{
if (DoubleUtil.AreClose(back1, path[i]))
{
// Filter out duplicate points
i++;
continue;
}
Vector begin = back2 - back1;
Vector end = path[i] - back1;
//On a line defined by begin & end, finds the findex of the point nearest to the origin (0,0).
double findex = StrokeNodeOperations.GetProjectionFIndex(begin, end);
if (DoubleUtil.IsBetweenZeroAndOne(findex))
{
Vector v = (begin + (end - begin) * findex);
if (v.LengthSquared < CollinearTolerance)
{
// The point back1 can be considered as on the line from back2 to the toTest StrokeNode.
// Modify the previous point.
newPath[newPath.Count - 1] = path[i];
back1 = path[i];
i++;
#if POINTS_FILTER_TRACE
_collinearPointsScreened ++;
#endif
continue;
}
}
// Add the surviving point into the list.
newPath.Add(path[i]);
back2 = back1;
back1 = path[i];
i++;
}
#if POINTS_FILTER_TRACE
_totalPointsScreened += path.Length - newPath.Count;
#endif
return newPath.ToArray();
}
#endregion
#region Fields
private StrokeNodeIterator _nodeIterator;
private List<StrokeNode> _erasingStrokeNodes = null;
private Rect _bounds = Rect.Empty;
#if POINTS_FILTER_TRACE
private int _totalPointsAdded = 0;
private int _totalPointsScreened = 0;
private int _collinearPointsScreened = 0;
#endif
// The collinear tolerance used in points filtering algorithm. The valie
// should be further tuned considering trade-off of performance and accuracy.
// In general, the larger the value, more points are filtered but less accurate.
// For a value of 0.5, typically 70% - 80% percent of the points are filtered out.
private static readonly double CollinearTolerance = 0.1f;
#endregion
}
#endregion
}
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