From 5bb10d4bd6fc48a9b5eb69b4af6c882434fdd9b4 Mon Sep 17 00:00:00 2001
From: Durgesh Khandal <durgeshlive@gmail.com>
Date: Tue, 29 Oct 2019 16:05:04 +0530
Subject: [PATCH] Fixed 5680 - Added method to force value coercion (#8097)

---
 .../Issue5680.xaml                                 | 16 ++++++
 .../Issue5680.xaml.cs                              | 59 ++++++++++++++++++++++
 Xamarin.Forms.Core/BindableObject.cs               | 30 +++++++++++
 3 files changed, 105 insertions(+)
 create mode 100644 Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5680.xaml
 create mode 100644 Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5680.xaml.cs

diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5680.xaml b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5680.xaml
new file mode 100644
index 0000000..c7e01f6
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5680.xaml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<local:TestContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:Xamarin.Forms.Controls" x:Class="Xamarin.Forms.Controls.Issues.Issue5680" x:Name="page1">
+    <StackLayout Padding="0,20,0,0" BindingContext="{x:Reference page1}">
+        <Label Text="Bindable Property CoerceValue Callback Demo" FontAttributes="Bold" HorizontalOptions="Center" />
+        <StackLayout Orientation="Horizontal" HorizontalOptions="Center">
+            <Label Text="Maximum angle:" />
+            <Entry Text="{Binding MaximumAngle}" WidthRequest="50" />
+        </StackLayout>
+        <StackLayout Orientation="Horizontal" HorizontalOptions="Center">
+            <Label Text="Rotation angle:" />
+            <Entry Text="{Binding Angle}" WidthRequest="50" />
+        </StackLayout>
+        <Label x:Name="CoerceResult" FontAttributes="Bold" HorizontalOptions="Center"/>
+        <Image Source="test.jpg" Rotation="{Binding Angle}" VerticalOptions="CenterAndExpand" WidthRequest="300" HeightRequest="300" />
+    </StackLayout>
+</local:TestContentPage>
\ No newline at end of file
diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5680.xaml.cs b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5680.xaml.cs
new file mode 100644
index 0000000..5ab1152
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5680.xaml.cs
@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using Xamarin.Forms;
+using System.Threading.Tasks;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 5680, "[Enhancement] Add method to force value coercion")]
+	public partial class Issue5680 : TestContentPage
+    {
+		
+		public Issue5680()
+        {
+            InitializeComponent();
+        }
+
+		protected override void Init()
+		{
+
+		}
+
+		public static readonly BindableProperty AngleProperty = BindableProperty.Create("Angle", typeof(double), typeof(Issue5680), 0.0, coerceValue: CoerceAngle);
+		public static readonly BindableProperty MaximumAngleProperty = BindableProperty.Create("MaximumAngle", typeof(double), typeof(Issue5680), 360.0, propertyChanged: ForceCoerceValue);
+
+		public double Angle
+		{
+			get { return (double)GetValue(AngleProperty); }
+			set { SetValue(AngleProperty, value); }
+		}
+
+		public double MaximumAngle
+		{
+			get { return (double)GetValue(MaximumAngleProperty); }
+			set { SetValue(MaximumAngleProperty, value); }
+		}
+
+		static object CoerceAngle(BindableObject bindable, object value)
+		{
+			var homePage = bindable as Issue5680;
+			double input = (double)value;
+
+			if (input > homePage.MaximumAngle)
+			{
+				input = homePage.MaximumAngle;
+			}
+			return input;
+		}
+
+		static void ForceCoerceValue(BindableObject bindable, object oldValue, object newValue)
+		{
+			bindable.CoerceValue(AngleProperty);
+		}
+	}
+}
\ No newline at end of file
diff --git a/Xamarin.Forms.Core/BindableObject.cs b/Xamarin.Forms.Core/BindableObject.cs
index 7adcfff..edb1309 100644
--- a/Xamarin.Forms.Core/BindableObject.cs
+++ b/Xamarin.Forms.Core/BindableObject.cs
@@ -530,6 +530,36 @@ namespace Xamarin.Forms
 			context.Binding = null;
 		}
 
+		public void CoerceValue(BindableProperty property) => CoerceValue(property, checkAccess: true);
+
+		public void CoerceValue(BindablePropertyKey propertyKey)
+		{
+			if (propertyKey == null)
+				throw new ArgumentNullException(nameof(propertyKey));
+
+			CoerceValue(propertyKey.BindableProperty, checkAccess: false);
+		}
+
+		void CoerceValue(BindableProperty property, bool checkAccess)
+		{
+			if (property == null)
+				throw new ArgumentNullException(nameof(property));
+
+			if (checkAccess && property.IsReadOnly)
+				throw new InvalidOperationException($"The BindableProperty \"{property.PropertyName}\" is readonly.");
+
+			BindablePropertyContext bpcontext = GetContext(property);
+			if (bpcontext == null)
+				return;
+
+			object currentValue = bpcontext.Value;
+
+			if (property.ValidateValue != null && !property.ValidateValue(this, currentValue))
+				throw new ArgumentException($"Value is an invalid value for {property.PropertyName}", nameof(currentValue));
+
+			property.CoerceValue?.Invoke(this, currentValue);
+		}
+
 		[Flags]
 		enum BindableContextAttributes
 		{
-- 
2.7.4