DynamicDataDisplay/ViewportRestrictions/DataHeightRestriction.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Collections.ObjectModel;
using System.Collections.Specialized;

namespace Microsoft.Research.DynamicDataDisplay.ViewportRestrictions
{
	public class DataHeightRestriction : ViewportRestriction, ISupportAttachToViewport
	{
		private double yEnlargeCoeff = 1.1;
		public double YEnlargeCoeff
		{
			get { return yEnlargeCoeff; }
			set
			{
				if (yEnlargeCoeff != value)
				{
					yEnlargeCoeff = value;
					RaiseChanged();
				}
			}
		}

		public override DataRect Apply(DataRect oldDataRect, DataRect newDataRect, Viewport2D viewport)
		{
			DataRect overallBounds = DataRect.Empty;

			foreach (var chart in viewport.ContentBoundsHosts)
			{
                var plotterElement = chart as IPlotterElement;
				var visual = viewport.Plotter.VisualBindings[plotterElement];
				var points = (ReadOnlyCollection<Point>)PointsGraphBase.GetVisiblePoints(visual);
				if (points != null)
				{

					// searching for indices of chart's visible points which are near left and right borders of newDataRect
					double startX = newDataRect.XMin;
					double endX = newDataRect.XMax;

					if (points[0].X > endX || points[points.Count - 1].X < startX)
					{
						continue;
					}

					int startIndex = -1;

					// we assume that points are sorted by x values ascending
					if (startX <= points[0].X)
					{
						startIndex = 0;
					}
					else
					{
						for (int i = 1; i < points.Count - 1; i++)
						{
							if (points[i].X <= startX && startX < points[i + 1].X)
							{
								startIndex = i;
								break;
							}
						}
					}

					int endIndex = points.Count;

					if (points[points.Count - 1].X < endX)
					{
						endIndex = points.Count;
					}
					else
					{
						for (int i = points.Count - 1; i >= 1; i--)
						{
							if (points[i - 1].X <= endX && endX < points[i].X)
							{
								endIndex = i;
								break;
							}
						}
					}

					Rect bounds = Rect.Empty;
					for (int i = startIndex; i < endIndex; i++)
					{
						bounds.Union(points[i]);
					}
					if (startIndex > 0)
					{
						Point pt = GetInterpolatedPoint(startX, points[startIndex], points[startIndex - 1]);
						bounds.Union(pt);
					}
					if (endIndex < points.Count - 1)
					{
						Point pt = GetInterpolatedPoint(endX, points[endIndex], points[endIndex + 1]);
						bounds.Union(pt);
					}

					overallBounds.Union(bounds);
				}
			}

			if (!overallBounds.IsEmpty)
			{
				double y = overallBounds.YMin;
				double height = overallBounds.Height;

				if (height == 0)
				{
					height = newDataRect.Height;
					y -= height / 2;
				}

				newDataRect = new DataRect(newDataRect.XMin, y, newDataRect.Width, height);
				newDataRect = DataRectExtensions.ZoomY(newDataRect, newDataRect.GetCenter(), yEnlargeCoeff);
			}

			return newDataRect;
		}

		private static Point GetInterpolatedPoint(double x, Point p1, Point p2)
		{
			double xRatio = (x - p1.X) / (p2.X - p1.X);
			double y = (1 - xRatio) * p1.Y + xRatio * p2.Y;

			return new Point(x, y);
		}

		#region ISupportAttach Members

		void ISupportAttachToViewport.Attach(Viewport2D viewport)
		{
			((INotifyCollectionChanged)viewport.ContentBoundsHosts).CollectionChanged += OnContentBoundsHostsChanged;

			foreach (var item in viewport.ContentBoundsHosts)
			{
				PointsGraphBase chart = item as PointsGraphBase;
				if (chart != null)
				{
					chart.ProvideVisiblePoints = true;
				}
			}
		}

		private void OnContentBoundsHostsChanged(object sender, NotifyCollectionChangedEventArgs e)
		{
			if (e.NewItems != null)
			{
				foreach (var item in e.NewItems)
				{
					PointsGraphBase chart = item as PointsGraphBase;
					if (chart != null)
					{
						chart.ProvideVisiblePoints = true;
					}
				}
			}

			// todo probably set ProvideVisiblePoints to false on OldItems
		}

		void ISupportAttachToViewport.Detach(Viewport2D viewport)
		{
			((INotifyCollectionChanged)viewport.ContentBoundsHosts).CollectionChanged -= OnContentBoundsHostsChanged;
		}

		#endregion
	}
}