feat: Add stub for virtualizing recycling scrollview

Maui/VirtualizingRecyclingScrollView/App.xaml

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+<?xml version = "1.0" encoding = "UTF-8" ?>
+<Application xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:local="clr-namespace:VirtualizingRecyclingScrollView"
+             x:Class="VirtualizingRecyclingScrollView.App">
+    <Application.Resources>
+        <ResourceDictionary>
+            <ResourceDictionary.MergedDictionaries>
+                <ResourceDictionary Source="Resources/Styles/Colors.xaml" />
+                <ResourceDictionary Source="Resources/Styles/Styles.xaml" />
+            </ResourceDictionary.MergedDictionaries>
+        </ResourceDictionary>
+    </Application.Resources>
+</Application>

Maui/VirtualizingRecyclingScrollView/App.xaml.cs

@@ -0,0 +1,14 @@
+namespace VirtualizingRecyclingScrollView;
+
+public partial class App : Application
+{
+	public App()
+	{
+		InitializeComponent();
+	}
+
+	protected override Window CreateWindow(IActivationState? activationState)
+	{
+		return new Window(new AppShell());
+	}
+}

Maui/VirtualizingRecyclingScrollView/AppShell.xaml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<Shell
+    x:Class="VirtualizingRecyclingScrollView.AppShell"
+    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:local="clr-namespace:VirtualizingRecyclingScrollView">
+
+    <ShellContent
+        ContentTemplate="{DataTemplate local:MainPage}"
+        Route="MainPage"/>
+
+</Shell>

Maui/VirtualizingRecyclingScrollView/AppShell.xaml.cs

@@ -0,0 +1,9 @@
+namespace VirtualizingRecyclingScrollView;
+
+public partial class AppShell : Shell
+{
+	public AppShell()
+	{
+		InitializeComponent();
+	}
+}

Maui/VirtualizingRecyclingScrollView/CellModel.cs

@@ -0,0 +1,44 @@
+
+using System.ComponentModel;
+
+namespace VirtualizingRecyclingScrollView;
+
+public class CellModel : INotifyPropertyChanged
+{
+    private static PropertyChangedEventArgs changedAll = new PropertyChangedEventArgs(null);
+
+    public Key key;
+
+    private string text;
+
+    private Color color;
+
+    public event PropertyChangedEventHandler? PropertyChanged;
+
+    public string Text
+    {
+        get => this.text;
+        set
+        {
+            this.text = value;
+            this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Text)));
+        }
+    }
+
+    public Color Color
+    {
+        get => this.color;
+        set
+        {
+            this.color = value;
+            this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Color)));
+        }
+    }
+
+    internal void Update(string text, Color color)
+    {
+        this.text = text;
+        this.color = color;
+        this.PropertyChanged?.Invoke(this, changedAll);
+    }
+}

Maui/VirtualizingRecyclingScrollView/Key.cs

@@ -0,0 +1,13 @@
+namespace VirtualizingRecyclingScrollView;
+
+public struct Key
+{
+    public int x;
+    public int y;
+
+    public Key(int x, int y)
+    {
+        this.x = x;
+        this.y = y;
+    }
+}

Maui/VirtualizingRecyclingScrollView/MainPage.xaml

@@ -0,0 +1,111 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="VirtualizingRecyclingScrollView.MainPage"
+             xmlns:local="clr-namespace:VirtualizingRecyclingScrollView"
+             xmlns:ios="clr-namespace:Microsoft.Maui.Controls.PlatformConfiguration.iOSSpecific;assembly=Microsoft.Maui.Controls"
+             ios:Page.UseSafeArea="False"
+             Shell.NavBarIsVisible="False"
+             Background="White">
+
+    <Grid IgnoreSafeArea="True">
+        <Grid.RowDefinitions>
+            <RowDefinition Height="60" />
+            <RowDefinition Height="50" />
+            <RowDefinition Height="*" />
+            <RowDefinition Height="50" />
+        </Grid.RowDefinitions>
+
+        <local:TrackingBorder x:Name="HeaderBackground" Grid.Row="0" Grid.RowSpan="2" Background="#DDFFFFFF" />
+        <Grid Grid.Row="1" x:Name="HeaderContent">
+            <VerticalStackLayout>
+                <local:TrackingLabel Text="Title" TextColor="Black" VerticalOptions="Center" Margin="10,0,10,0" FontSize="24" />
+                <HorizontalStackLayout Margin="9,0,0,0">
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                </HorizontalStackLayout>
+                <HorizontalStackLayout Margin="9,0,0,0">
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                </HorizontalStackLayout>
+                <HorizontalStackLayout Margin="9,0,0,0">
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                    <local:TrackingBorder Background="Red" WidthRequest="5" HeightRequest="5" />
+                </HorizontalStackLayout>
+            </VerticalStackLayout>
+            <Grid HorizontalOptions="End">
+                <Grid.RowDefinitions>
+                    <RowDefinition Height="20" />
+                    <RowDefinition Height="20" />
+                </Grid.RowDefinitions>
+                <Grid.ColumnDefinitions>
+                    <ColumnDefinition Width="120" />
+                    <ColumnDefinition Width="60" />
+                    <ColumnDefinition Width="120" />
+                    <ColumnDefinition Width="50" />
+                </Grid.ColumnDefinitions>
+
+                <Label Grid.Row="0" Grid.Column="0" Text="Shell El. Layout:" TextColor="Black" VerticalOptions="Center" HorizontalTextAlignment="End" HorizontalOptions="End" FontSize="14" />
+                <Label Grid.Row="0" Grid.Column="1" Text="{Binding LayoutNodes}" TextColor="Black" VerticalOptions="Center" HorizontalTextAlignment="Start" FontSize="14" WidthRequest="60" HeightRequest="16" />
+
+                <Label Grid.Row="1" Grid.Column="0" Text="Virtual El. Layout:" TextColor="Black" VerticalOptions="Center" HorizontalTextAlignment="End" HorizontalOptions="End" FontSize="14" />
+                <Label Grid.Row="1" Grid.Column="1" Text="{Binding LayoutVirtualNodes}" TextColor="Black" VerticalOptions="Center" HorizontalTextAlignment="Start" FontSize="14" WidthRequest="60" HeightRequest="16" />
+
+                <Label Grid.Row="0" Grid.Column="2" Text="Recycled Items:" TextColor="Black" VerticalOptions="Center" HorizontalTextAlignment="End" HorizontalOptions="End" FontSize="14" />
+                <Label Grid.Row="0" Grid.Column="3" Text="{Binding RecycledItems}" TextColor="Black" VerticalOptions="Center" HorizontalTextAlignment="Start" FontSize="14" WidthRequest="50" HeightRequest="16" />
+
+                <Label Grid.Row="1" Grid.Column="2" Text="Dropped Frames:" TextColor="Black" VerticalOptions="Center" HorizontalTextAlignment="End" HorizontalOptions="End" FontSize="14" />
+                <Label Grid.Row="1" Grid.Column="3" Text="{Binding DroppedFrames}" TextColor="Black" VerticalOptions="Center" HorizontalTextAlignment="Start" FontSize="14" WidthRequest="50" HeightRequest="16" />
+
+            </Grid>
+        </Grid>
+        <local:TrackingBorder x:Name="FooterBackground" Grid.Row="3" Background="#DDFFFFFF" />
+
+        <local:TheScrollView x:Name="SV" Grid.RowSpan="4" ZIndex="-1">
+            <local:TheScrollView.Template>
+                <DataTemplate x:DataType="local:CellModel">
+                    <!-- Slim template: we can't trim further than that -->
+                    <local:TrackingLabel Virtualized="True" Text="{Binding Text}" TextColor="Black" Background="{Binding Color}" Margin="2" FontSize="16" FontAttributes="Bold" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" />
+
+                    <!-- Medium template: no triggers or visual states -->
+                    <!-- <local:TrackingBorder Virtualized="True" Background="{Binding Color}" Margin="1" StrokeThickness="1" Stroke="DarkGray">
+                        <local:TrackingLabel Virtualized="True" Text="{Binding Text}" TextColor="Black" Margin="2" FontSize="16" FontAttributes="Bold" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" />
+                    </local:TrackingBorder> -->
+
+                    <!-- Fat template: That would include a border, a grid, icon and a label, maybe interactive with a trigger -->
+                </DataTemplate>
+            </local:TheScrollView.Template>
+        </local:TheScrollView>
+    </Grid>
+
+</ContentPage>

Maui/VirtualizingRecyclingScrollView/MainPage.xaml.cs

@@ -0,0 +1,22 @@
+namespace VirtualizingRecyclingScrollView;
+
+public partial class MainPage : ContentPage
+{
+	public MainPage()
+	{
+		this.BindingContext = TrackingModel.Instance;
+		InitializeComponent();
+
+		this.Dispatcher.DispatchDelayed(TimeSpan.FromSeconds(1), () => {
+			this.SV.ScrollToAsync(40, 0, false);
+			this.Dispatcher.DispatchDelayed(TimeSpan.FromSeconds(1), () => {
+				TrackingModel.Instance.Clear();
+				this.Dispatcher.DispatchDelayed(TimeSpan.FromSeconds(3), async () => {
+					MauiProgram.SuppressWorkarounds = true;
+					await this.SV.ScrollToAsync(40, 800, true);
+					MauiProgram.SuppressWorkarounds = false;
+				});
+			});
+		});
+	}
+}

Maui/VirtualizingRecyclingScrollView/MauiProgram.cs

@@ -0,0 +1,40 @@
+using System.Runtime.CompilerServices;
+using Microsoft.Extensions.Logging;
+using Microsoft.Maui.Handlers;
+
+namespace VirtualizingRecyclingScrollView;
+
+public static class MauiProgram
+{
+	public static int IsInVirtualizationScope = 0;
+	public static bool SuppressWorkarounds = false;
+
+	public static MauiApp CreateMauiApp()
+	{
+		var builder = MauiApp.CreateBuilder();
+		builder
+			.UseMauiApp<App>()
+			.ConfigureMauiHandlers(handlers =>
+			{
+				ViewHandler.ViewCommandMapper.ModifyMapping<IView, IViewHandler>(nameof(IView.InvalidateMeasure), (layout, handler, args, current) =>
+				{
+					if (MauiProgram.SuppressWorkarounds || MauiProgram.IsInVirtualizationScope == 0)
+					{
+						// Comment this out to stop layout invalidation...
+						current?.Invoke(layout, handler, args);
+					}
+				});
+			})
+			.ConfigureFonts(fonts =>
+			{
+				fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
+				fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
+			});
+
+#if DEBUG
+		builder.Logging.AddDebug();
+#endif
+
+		return builder.Build();
+	}
+}

Maui/VirtualizingRecyclingScrollView/Platforms/Android/AndroidManifest.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+	<application android:allowBackup="true" android:icon="@mipmap/appicon" android:roundIcon="@mipmap/appicon_round" android:supportsRtl="true"></application>
+	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+	<uses-permission android:name="android.permission.INTERNET" />
+</manifest>

Maui/VirtualizingRecyclingScrollView/Platforms/Android/MainActivity.cs

@@ -0,0 +1,10 @@
+using Android.App;
+using Android.Content.PM;
+using Android.OS;
+
+namespace VirtualizingRecyclingScrollView;
+
+[Activity(Theme = "@style/Maui.SplashTheme", MainLauncher = true, LaunchMode = LaunchMode.SingleTop, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize | ConfigChanges.Density)]
+public class MainActivity : MauiAppCompatActivity
+{
+}

Maui/VirtualizingRecyclingScrollView/Platforms/Android/MainApplication.cs

@@ -0,0 +1,15 @@
+using Android.App;
+using Android.Runtime;
+
+namespace VirtualizingRecyclingScrollView;
+
+[Application]
+public class MainApplication : MauiApplication
+{
+	public MainApplication(IntPtr handle, JniHandleOwnership ownership)
+		: base(handle, ownership)
+	{
+	}
+
+	protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
+}

Maui/VirtualizingRecyclingScrollView/Platforms/Android/Resources/values/colors.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="colorPrimary">#512BD4</color>
+    <color name="colorPrimaryDark">#2B0B98</color>
+    <color name="colorAccent">#2B0B98</color>
+</resources>

Maui/VirtualizingRecyclingScrollView/Platforms/MacCatalyst/AppDelegate.cs

@@ -0,0 +1,9 @@
+using Foundation;
+
+namespace VirtualizingRecyclingScrollView;
+
+[Register("AppDelegate")]
+public class AppDelegate : MauiUIApplicationDelegate
+{
+	protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
+}

Maui/VirtualizingRecyclingScrollView/Platforms/MacCatalyst/Entitlements.plist

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+    <!-- See https://aka.ms/maui-publish-app-store#add-entitlements for more information about adding entitlements.-->
+    <dict>
+        <!-- App Sandbox must be enabled to distribute a MacCatalyst app through the Mac App Store. -->
+        <key>com.apple.security.app-sandbox</key>
+        <true/>
+        <!-- When App Sandbox is enabled, this value is required to open outgoing network connections. -->
+        <key>com.apple.security.network.client</key>
+        <true/>
+    </dict>
+</plist>
+

Maui/VirtualizingRecyclingScrollView/Platforms/MacCatalyst/Info.plist

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <!-- The Mac App Store requires you specify if the app uses encryption. -->
+    <!-- Please consult https://developer.apple.com/documentation/bundleresources/information_property_list/itsappusesnonexemptencryption -->
+    <!-- <key>ITSAppUsesNonExemptEncryption</key> -->
+    <!-- Please indicate <true/> or <false/> here. -->
+
+    <!-- Specify the category for your app here. -->
+    <!-- Please consult https://developer.apple.com/documentation/bundleresources/information_property_list/lsapplicationcategorytype -->
+    <!-- <key>LSApplicationCategoryType</key> -->
+    <!-- <string>public.app-category.YOUR-CATEGORY-HERE</string> -->
+	<key>UIDeviceFamily</key>
+	<array>
+		<integer>2</integer>
+	</array>
+	<key>UIRequiredDeviceCapabilities</key>
+	<array>
+		<string>arm64</string>
+	</array>
+	<key>UISupportedInterfaceOrientations</key>
+	<array>
+		<string>UIInterfaceOrientationPortrait</string>
+		<string>UIInterfaceOrientationLandscapeLeft</string>
+		<string>UIInterfaceOrientationLandscapeRight</string>
+	</array>
+	<key>UISupportedInterfaceOrientations~ipad</key>
+	<array>
+		<string>UIInterfaceOrientationPortrait</string>
+		<string>UIInterfaceOrientationPortraitUpsideDown</string>
+		<string>UIInterfaceOrientationLandscapeLeft</string>
+		<string>UIInterfaceOrientationLandscapeRight</string>
+	</array>
+	<key>XSAppIconAssets</key>
+	<string>Assets.xcassets/appicon.appiconset</string>
+</dict>
+</plist>