source: branches/HeuristicLab.Problems.GrammaticalOptimization/DynamicDataDisplay/ViewportConstraints/PhysicalProportionsConstraint.cs @ 13780

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Diagnostics;

namespace Microsoft.Research.DynamicDataDisplay.ViewportConstraints
{
  /// <summary>
  /// Represents a restriction in which actual visible rect's proportions depends on 
  /// actual output rect's proportions.
  /// </summary>
  public sealed class PhysicalProportionsConstraint : ViewportConstraint
  {
    /// <summary>
    /// Initializes a new instance of the <see cref="PhysicalProportionsConstraint"/> class.
    /// </summary>
    public PhysicalProportionsConstraint() { }

    /// <summary>
    /// Initializes a new instance of the <see cref="PhysicalProportionsConstraint"/> class with the given proportion ratio.
    /// </summary>
    /// <param name="proportionRatio">The proportion ratio.</param>
    public PhysicalProportionsConstraint(double proportionRatio)
    {
      ProportionRatio = proportionRatio;
    }

    private double proportionRatio = 1.0;
    /// <summary>Gets or sets the proportion ratio (width / height). Default value is 1.0.</summary>
    /// <value>The proportion ratio.</value>
    public double ProportionRatio
    {
      get { return proportionRatio; }
      set
      {
        if (proportionRatio != value)
        {
          proportionRatio = value;
          RaiseChanged();
        }
      }
    }

    /// <summary>
    /// Applies the restriction.
    /// </summary>
    /// <param name="previousDataRect">Previous data rectangle.</param>
    /// <param name="proposedDataRect">Proposed data rectangle.</param>
    /// <param name="viewport">The viewport, to which current restriction is being applied.</param>
    /// <returns>New changed visible rectangle.</returns>
    public override DataRect Apply(DataRect previousDataRect, DataRect proposedDataRect, Viewport2D viewport)
    {
      Rect output = viewport.Output;
      if (output.Height == 0 || output.Width == 0)
        return proposedDataRect;

            double newRatio = proposedDataRect.Width * output.Height / 
                (proposedDataRect.Height * output.Width);

            // Don't modify rect if new ratio differs only slightly 
            if (Math.Abs(newRatio - proportionRatio) < 1e-3)
                return proposedDataRect;

            // Try to keep visible rect's square constant
            double width = proposedDataRect.Width, height = proposedDataRect.Height;
            double square = proposedDataRect.Width * proposedDataRect.Height;
            if (square > 0)
            {
                width = Math.Sqrt(proportionRatio * output.Width * square / output.Height);
                height = Math.Sqrt(output.Height * square / (proportionRatio * output.Width));
            }

            // Finally ensure we have correct aspect ratio
            double delta = (proportionRatio * height * output.Width - width * output.Height) /
                (output.Height + proportionRatio * output.Width);
            width += delta;
            height -= delta;

            double x0 = (proposedDataRect.XMax + proposedDataRect.XMin) / 2;
            double y0 = (proposedDataRect.YMax + proposedDataRect.YMin) / 2;

            return new DataRect
            {
                XMin = x0 - width / 2,
                Width = width,
                YMin = y0 - height / 2,
                Height = height
            };
    }
  }
}