feat: Add Barometer sample

Uno.Gallery/Uno.Gallery.Shared/Uno.Gallery.Shared.projitems

@@ -200,7 +200,9 @@
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
     </_Globbled_Page>
-    <Page Include="@(_Globbled_Page)" />
+    <Page Include="@(_Globbled_Page)">
+      <SubType>Designer</SubType>
+    </Page>
     <_Globbed_Compile Include="$(MSBuildThisFileDirectory)**/*.xaml.cs" Exclude="@(Compile)">
       <DependentUpon>%(Filename)</DependentUpon>
     </_Globbed_Compile>

Uno.Gallery/Uno.Gallery.Shared/Views/SamplePages/BarometerSamplePage.xaml

@@ -0,0 +1,64 @@
+<Page x:Class="Uno.Gallery.Views.Samples.BarometerSamplePage"
+	  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+	  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+	  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+	  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+	  xmlns:smtx="using:ShowMeTheXAML"
+	  xmlns:local="using:Uno.Gallery"
+	  mc:Ignorable="d">
+
+	<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+		<local:SamplePageLayout IsDesignAgnostic="True">
+			<local:SamplePageLayout.DesignAgnosticTemplate>
+				<DataTemplate>
+					<StackPanel>
+						<smtx:XamlDisplay UniqueKey="BarometerSamplePage_Sample"
+										  smtx:XamlDisplayExtensions.IgnorePath="XX"
+										  smtx:XamlDisplayExtensions.Header="Barometer">
+							<Grid>
+								<Grid.RowDefinitions>
+									<RowDefinition Height="auto" />
+									<RowDefinition Height="auto" />
+								</Grid.RowDefinitions>
+								<!-- C# code
+var barometer = Barometer.GetDefault();
+barometer.ReadingChanged += Barometer_ReadingChanged;
+
+private async void Barometer_ReadingChanged(Barometer sender, BarometerReadingChangedEventArgs args)
+{
+    // If you want to update the UI in some way, ensure the Dispatcher is used,
+    // as the ReadingChanged event handler does not run on the UI thread.
+    await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
+    {
+        OutputTextBlock.Text = $"Sensor reading in hPa = {args.Reading.StationPressureInHectopascals}, " +
+            $"timestamp = {args.Reading.Timestamp}";
+    });
+}
+-->
+
+								<TextBlock Visibility="{Binding Data.BarometerAvailable}"
+										   Margin="0,0,0,20">
+									<LineBreak />
+									<Span FontWeight="Bold">Pressure (hPA): </Span>
+									<Run Text="{Binding Data.Pressure}" />
+									<LineBreak />
+									<Span FontWeight="Bold">Last read timestamp: </Span>
+									<Run Text="{Binding Data.LastReadTimestamp}" />
+								</TextBlock>
+
+								<Button IsEnabled="{Binding Data.BarometerAvailable}"
+										Grid.Row="1"
+										Click="ObserveReadingChangeButton_Click">
+									<TextBlock Text="{Binding Data.ButtonContent}"
+											   VerticalAlignment="Stretch"
+											   TextAlignment="Center" />
+								</Button>
+							</Grid>
+						</smtx:XamlDisplay>
+					</StackPanel>
+				</DataTemplate>
+			</local:SamplePageLayout.DesignAgnosticTemplate>
+
+		</local:SamplePageLayout>
+	</Grid>
+</Page>

Uno.Gallery/Uno.Gallery.Shared/Views/SamplePages/BarometerSamplePage.xaml.cs

@@ -0,0 +1,85 @@
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using System;
+using Uno.Gallery.ViewModels;
+using Windows.Devices.Sensors;
+
+namespace Uno.Gallery.Views.Samples
+{
+	[SamplePage(SampleCategory.NonUIFeatures, "Barometer",
+		Description = "Represents a Barometer sensor. This sensor returns pressure in hectopascals (hPa).",
+		DocumentationLink = "https://platform.uno/docs/articles/features/barometer.html",
+		DataType = typeof(BarometerSamplePageViewModel))]
+	public sealed partial class BarometerSamplePage : Page
+	{
+		public BarometerSamplePage()
+		{
+			this.InitializeComponent();
+		}
+
+		private void ObserveReadingChangeButton_Click(object sender, RoutedEventArgs e)
+		{
+			if (!(((Sample)DataContext).Data is BarometerSamplePageViewModel viewModel))
+				return;
+
+
+			if (!viewModel.ObservingReadingChange)
+			{
+				viewModel.StartObserveReadingChange();
+			}
+			else
+			{
+				viewModel.StopObservingReadingChange();
+			}
+		}
+	}
+}
+
+public class BarometerSamplePageViewModel : ViewModelBase
+{
+	private const string _startObservingContent = "Start observing barometer reading changes";
+	private const string _stopObservingContent = "Stop observing barometer reading changes";
+	private string _notAvailable = "Barometer is not available on this device/platform";
+
+	private readonly Barometer _barometer;
+
+	public double Pressure { get => GetProperty<double>(); set => SetProperty(value); }
+	public string ButtonContent { get => GetProperty<string>(); set => SetProperty(value); }
+	public DateTimeOffset? LastReadTimestamp { get => GetProperty<DateTimeOffset?>(); set => SetProperty(value); }
+	public bool ObservingReadingChange { get => GetProperty<bool>(); set => SetProperty(value); }
+
+	public bool BarometerAvailable => _barometer != null;
+
+	public BarometerSamplePageViewModel()
+	{
+		_barometer = Barometer.GetDefault();
+
+		if (BarometerAvailable)
+		{
+			ButtonContent = _startObservingContent;
+			return;
+		}
+
+		ButtonContent = _notAvailable;
+	}
+
+	public void StartObserveReadingChange()
+	{
+		_barometer.ReadingChanged += Barometer_ReadingChanged;
+		ButtonContent = _stopObservingContent;
+		ObservingReadingChange = true;
+	}
+
+	public void StopObservingReadingChange()
+	{
+		_barometer.ReadingChanged -= Barometer_ReadingChanged;
+		ButtonContent = _startObservingContent;
+		ObservingReadingChange = false;
+	}
+
+	private void Barometer_ReadingChanged(Barometer sender, BarometerReadingChangedEventArgs args)
+	{
+		LastReadTimestamp = args.Reading.Timestamp;
+		Pressure = args.Reading.StationPressureInHectopascals;
+	}
+}