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jsuarezruizjsuarezruiz
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[Core] Notify changes in a GradientStop (Color, Offset) (#11783) fixes #11898
* Added repro sample * Updated sample * Fix the issue
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5 files changed

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lines changed

‎Xamarin.Forms.Controls/GalleryPages/GradientGalleries/GradientsGallery.cs

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@@ -58,6 +58,8 @@ public GradientsGallery()
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new RadialGradientExplorerGallery(), Navigation),
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GalleryBuilder.NavButton("Bindable Brush Gallery", () =>
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new BindableBrushGallery(), Navigation),
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GalleryBuilder.NavButton("Update Brush Colors Gallery", () =>
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new UpdateGradientColorGallery(), Navigation),
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GalleryBuilder.NavButton("Animate Brush Gallery", () =>
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new AnimateBrushGallery(), Navigation),
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navigationBarButton,

‎Xamarin.Forms.Controls/GalleryPages/GradientGalleries/UpdateGradientColorGallery.xaml

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<?xml version="1.0" encoding="UTF-8"?>
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<ContentPage
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xmlns="http://xamarin.com/schemas/2014/forms"
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xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
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x:Class="Xamarin.Forms.Controls.GalleryPages.GradientGalleries.UpdateGradientColorGallery"
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Title="Update Gradient Color Gallery">
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<ContentPage.Content>
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<StackLayout
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Padding="12">
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<Label
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Text="SolidColorBrush"/>
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<Frame
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BorderColor="LightGray"
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HasShadow="True"
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CornerRadius="12"
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HeightRequest="120"
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WidthRequest="120">
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<Frame.Background>
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<SolidColorBrush x:Name="SolidBrush" Color="Red" />
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</Frame.Background>
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</Frame>
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<Button
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Text="Update Color"
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Clicked="OnUpdateSolidColorClicked"/>
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<Label
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Text="LinearGradientBrush"/>
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<Frame
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BorderColor="LightGray"
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HasShadow="True"
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CornerRadius="12"
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HeightRequest="120"
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WidthRequest="120">
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<Frame.Background>
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<LinearGradientBrush x:Name="LinearBrush" StartPoint="0,1" EndPoint="0,0">
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<GradientStop Color="Blue" Offset="0.3"/>
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<GradientStop Color="Purple" Offset="0.6"/>
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<GradientStop Color="Green" Offset="0.9"/>
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</LinearGradientBrush>
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</Frame.Background>
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</Frame>
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<Button
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Text="Update Colors"
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Clicked="OnUpdateLinearColorsClicked"/>
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<Label
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Text="RadialGradientBrush"/>
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<Frame
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BorderColor="LightGray"
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HasShadow="True"
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CornerRadius="12"
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HeightRequest="120"
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WidthRequest="120">
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<Frame.Background>
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<RadialGradientBrush x:Name="RadialBrush" Center="0.5, 0.5" Radius="60">
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<GradientStop Color="Blue" Offset="0.3"/>
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<GradientStop Color="Purple" Offset="0.6"/>
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<GradientStop Color="Green" Offset="0.9"/>
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</RadialGradientBrush>
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</Frame.Background>
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</Frame>
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<Button
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Text="Update Colors"
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Clicked="OnUpdateRadialColorsClicked"/>
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</StackLayout>
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</ContentPage.Content>
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</ContentPage>

‎Xamarin.Forms.Controls/GalleryPages/GradientGalleries/UpdateGradientColorGallery.xaml.cs

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using System;
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namespace Xamarin.Forms.Controls.GalleryPages.GradientGalleries
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{
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public partial class UpdateGradientColorGallery : ContentPage
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{
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readonly Random _random;
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public UpdateGradientColorGallery()
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{
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InitializeComponent();
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_random = new Random();
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}
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void OnUpdateSolidColorClicked(object sender, EventArgs e)
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{
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SolidBrush.Color = GetRandomColor();
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}
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void OnUpdateLinearColorsClicked(object sender, EventArgs e)
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{
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GradientStop randomStop = LinearBrush.GradientStops[GetRandomGradientStop()];
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randomStop.Color = GetRandomColor();
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}
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void OnUpdateRadialColorsClicked(object sender, EventArgs e)
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{
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GradientStop firstStop = RadialBrush.GradientStops[GetRandomGradientStop()];
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firstStop.Color = GetRandomColor();
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}
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int GetRandomGradientStop()
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{
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return _random.Next(3);
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}
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Color GetRandomColor()
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{
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return Color.FromRgb(_random.Next(256), _random.Next(256), _random.Next(256));
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}
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}
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}

‎Xamarin.Forms.Core/GradientBrush.cs

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@@ -1,4 +1,7 @@
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using System.Runtime.CompilerServices;
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using System;
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using System.Collections.Specialized;
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using System.ComponentModel;
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using System.Runtime.CompilerServices;
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namespace Xamarin.Forms
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{
@@ -14,6 +17,8 @@ public GradientBrush()
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GradientStops = new GradientStopCollection();
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}
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public event EventHandler InvalidateGradientBrushRequested;
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internal static void VerifyExperimental([CallerMemberName] string memberName = "", string constructorHint = null)
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{
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if (IsExperimentalFlagSet)
@@ -24,13 +29,79 @@ internal static void VerifyExperimental([CallerMemberName] string memberName = "
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IsExperimentalFlagSet = true;
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}
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27-
public static readonly BindableProperty GradientStopsProperty = BindableProperty.Create(
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nameof(GradientStops), typeof(GradientStopCollection), typeof(GradientBrush), null);
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public static readonly BindableProperty GradientStopsProperty =
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BindableProperty.Create(nameof(GradientStops), typeof(GradientStopCollection), typeof(GradientBrush), null,
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propertyChanged: OnGradientStopsChanged);
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public GradientStopCollection GradientStops
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{
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get => (GradientStopCollection)GetValue(GradientStopsProperty);
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set => SetValue(GradientStopsProperty, value);
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}
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static void OnGradientStopsChanged(BindableObject bindable, object oldValue, object newValue)
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{
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(bindable as GradientBrush)?.UpdateGradientStops(oldValue as GradientStopCollection, newValue as GradientStopCollection);
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}
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void UpdateGradientStops(GradientStopCollection oldCollection, GradientStopCollection newCollection)
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{
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if (oldCollection != null)
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{
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oldCollection.CollectionChanged -= OnGradientStopCollectionChanged;
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foreach (var oldStop in oldCollection)
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{
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oldStop.PropertyChanged -= OnGradientStopPropertyChanged;
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}
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}
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if (newCollection == null)
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return;
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newCollection.CollectionChanged += OnGradientStopCollectionChanged;
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foreach (var newStop in newCollection)
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{
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newStop.PropertyChanged += OnGradientStopPropertyChanged;
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}
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}
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void OnGradientStopCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
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{
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if (e.OldItems != null)
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{
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foreach (var oldItem in e.OldItems)
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{
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if (!(oldItem is GradientStop oldStop))
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continue;
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oldStop.PropertyChanged -= OnGradientStopPropertyChanged;
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}
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}
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if (e.NewItems != null)
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{
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foreach (var newItem in e.NewItems)
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{
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if (!(newItem is GradientStop newStop))
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continue;
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newStop.PropertyChanged += OnGradientStopPropertyChanged;
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}
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}
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Invalidate();
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}
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void OnGradientStopPropertyChanged(object sender, PropertyChangedEventArgs e)
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{
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Invalidate();
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}
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void Invalidate()
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{
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InvalidateGradientBrushRequested?.Invoke(this, EventArgs.Empty);
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}
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}
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}

‎Xamarin.Forms.Core/VisualElement.cs

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Original file line numberDiff line numberDiff line change
@@ -168,8 +168,10 @@ void NotifyBackgroundChanges()
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{
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if (Background != null)
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{
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Background.PropertyChanging += OnBackgroundChanging;
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Background.PropertyChanged += OnBackgroundChanged;
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if (Background is GradientBrush gradientBrush)
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gradientBrush.InvalidateGradientBrushRequested += InvalidateGradientBrushRequested;
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}
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}
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@@ -178,16 +180,18 @@ void StopNotifyingBackgroundChanges()
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if (Background != null)
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{
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Background.PropertyChanged -= OnBackgroundChanged;
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Background.PropertyChanging -= OnBackgroundChanging;
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if (Background is GradientBrush gradientBrush)
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gradientBrush.InvalidateGradientBrushRequested -= InvalidateGradientBrushRequested;
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}
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}
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185-
void OnBackgroundChanging(object sender, PropertyChangingEventArgs e)
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void OnBackgroundChanged(object sender, PropertyChangedEventArgs e)
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{
187-
OnPropertyChanging(nameof(Background));
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OnPropertyChanged(nameof(Background));
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}
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190-
void OnBackgroundChanged(object sender, PropertyChangedEventArgs e)
194+
void InvalidateGradientBrushRequested(object sender, EventArgs e)
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{
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OnPropertyChanged(nameof(Background));
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}

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