NumericToSize.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System;
using System.Globalization;
using System.Windows;
using System.Windows.Data;

using SiliconStudio.Presentation.MarkupExtensions;

namespace SiliconStudio.Presentation.ValueConverters
{
    /// <summary>
    /// This converter will convert a double value to a <see cref="Size"/> structure.
    /// A <see cref="Size"/> must be passed as a parameter of this converter. You can use the <see cref="SizeExtension"/>
    /// markup extension to easily pass one, with the following syntax: {sskk:Size (arguments)}. The resulting size will
    /// be the parameter size multiplied bu the scalar double value.
    /// </summary>
    [ValueConversion(typeof(double), typeof(Size))]
    public class NumericToSize : ValueConverterBase<NumericToSize>
    {
        /// <inheritdoc/>
        public override object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            double scalar;
            try
            {
                scalar = System.Convert.ToDouble(value);
            }
            catch (Exception exception)
            {
                throw new ArgumentException("The value of this converter must be convertible to a double.", exception);
            }

            if (!(parameter is Size))
            {
                throw new ArgumentException("The parameter of this converter must be an instance of the Size structure. Use {sskk:Size (arguments)} to construct one.");
            }

            var size = (Size)parameter;
            var result = new Size(size.Width * scalar, size.Height * scalar);
            return result;
        }

        /// <inheritdoc/>
        public override object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (!(value is Size))
            {
                throw new ArgumentException("The value of the ConvertBack method of this converter must be a an instance of the Size structure.");
            }
            if (!(parameter is Size))
            {
                throw new ArgumentException("The parameter of the ConvertBack method of this converter must be a an instance of the Size structure.");
            }
            var sizeValue = (Size)value;
            var sizeParameter = (Size)parameter;

            double scalar = 0.0;
            if (Math.Abs(sizeParameter.Width) > double.Epsilon)
            {
                scalar = sizeValue.Width / sizeParameter.Width;
            }
            else if (Math.Abs(sizeParameter.Height) > double.Epsilon)
            {
                scalar = sizeValue.Height / sizeParameter.Height;
            }

            return System.Convert.ChangeType(scalar, targetType);
        }
    }
}