2016-03-22 23:02:25 +03:00
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using System;
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using System.Linq;
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using System.Reflection;
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using Xamarin.Forms.Internals;
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using Xamarin.Forms.Xaml;
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namespace Xamarin.Forms
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{
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2016-09-08 21:51:01 +03:00
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public class ConstraintExpression : IMarkupExtension<Constraint>
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2016-03-22 23:02:25 +03:00
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{
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public ConstraintExpression()
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{
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Factor = 1.0;
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}
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public double Constant { get; set; }
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public string ElementName { get; set; }
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public double Factor { get; set; }
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public string Property { get; set; }
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public ConstraintType Type { get; set; }
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2016-09-08 21:51:01 +03:00
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object IMarkupExtension.ProvideValue(IServiceProvider serviceProvider)
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{
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return (this as IMarkupExtension<Constraint>).ProvideValue(serviceProvider);
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}
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public Constraint ProvideValue(IServiceProvider serviceProvider)
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2016-03-22 23:02:25 +03:00
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{
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MethodInfo minfo;
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switch (Type)
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{
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default:
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case ConstraintType.RelativeToParent:
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if (string.IsNullOrEmpty(Property))
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return null;
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minfo = typeof(View).GetProperties().First(pi => pi.Name == Property && pi.CanRead && pi.GetMethod.IsPublic).GetMethod;
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return Constraint.RelativeToParent(p => (double)minfo.Invoke(p, new object[] { }) * Factor + Constant);
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case ConstraintType.Constant:
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return Constraint.Constant(Constant);
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case ConstraintType.RelativeToView:
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if (string.IsNullOrEmpty(Property))
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return null;
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if (string.IsNullOrEmpty(ElementName))
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return null;
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minfo = typeof(View).GetProperties().First(pi => pi.Name == Property && pi.CanRead && pi.GetMethod.IsPublic).GetMethod;
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var valueProvider = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;
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if (valueProvider == null || !(valueProvider.TargetObject is INameScope))
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return null;
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var view = ((INameScope)valueProvider.TargetObject).FindByName<View>(ElementName);
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return Constraint.RelativeToView(view, delegate(RelativeLayout p, View v) { return (double)minfo.Invoke(v, new object[] { }) * Factor + Constant; });
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}
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}
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}
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}
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