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using System;
using System.Collections.Generic;
using System.Linq.Expressions;
namespace Xamarin.Forms
{
[TypeConverter(typeof(ConstraintTypeConverter))]
public sealed class Constraint
{
Func<RelativeLayout, double> _measureFunc;
Constraint()
{
}
internal IEnumerable<View> RelativeTo { get; set; }
public static Constraint Constant(double size)
{
var result = new Constraint { _measureFunc = parent => size };
return result;
}
public static Constraint FromExpression(Expression<Func<double>> expression)
{
Func<double> compiled = expression.Compile();
var result = new Constraint
{
_measureFunc = layout => compiled(),
RelativeTo = ExpressionSearch.Default.FindObjects<View>(expression).ToArray() // make sure we have our own copy
};
return result;
}
public static Constraint RelativeToParent(Func<RelativeLayout, double> measure)
{
var result = new Constraint { _measureFunc = measure };
return result;
}
public static Constraint RelativeToView(View view, Func<RelativeLayout, View, double> measure)
{
var result = new Constraint { _measureFunc = layout => measure(layout, view), RelativeTo = new[] { view } };
return result;
}
internal double Compute(RelativeLayout parent)
{
return _measureFunc(parent);
}
}
}
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