Make DrawChart public static; add _SharedPropertiesTests

Changed DrawChart method in ChangingPaintTasks to public static
for external access. Added _SharedPropertiesTests class with
Visibility and VisibilityAndPaintsTasks tests to verify chart
rendering and drawable count behavior. Imported necessary
namespaces for testing.

tests/LiveChartsCore.UnitTesting/CoreObjectsTests/ChangingPaintTasks.cs

@@ -367,7 +367,7 @@ public void SectionsInstanceChanged()
             geometries == canvas.CountGeometries());
     }
 
-    private int DrawChart(InMemorySkiaSharpChart chart, bool animated = false)
+    public static int DrawChart(InMemorySkiaSharpChart chart, bool animated = false)
     {
         var coreChart = (Chart<SkiaSharpDrawingContext>)chart.CoreChart;
 

tests/LiveChartsCore.UnitTesting/SeriesTests/_SharedPropertiesTests.cs

@@ -0,0 +1,80 @@
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using LiveChartsCore.Defaults;
+using LiveChartsCore.SkiaSharpView;
+using LiveChartsCore.SkiaSharpView.SKCharts;
+using LiveChartsCore.UnitTesting.CoreObjectsTests;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace LiveChartsCore.UnitTesting.SeriesTests;
+
+[TestClass]
+public class _SharedPropertiesTests
+{
+    [TestMethod]
+    public void Visibility()
+    {
+        var values = new ObservableCollection<ObservableValue>();
+        var lineSeries = new LineSeries<ObservableValue>(values);
+
+        var chart = new SKCartesianChart
+        {
+            Series = [lineSeries],
+            Width = 1000,
+            Height = 1000
+        };
+
+        _ = chart.GetImage();
+
+        var changes = 0;
+
+        values.CollectionChanged +=
+            (object? sender, NotifyCollectionChangedEventArgs e) =>
+                changes++;
+
+        values.Add(new(1));
+        _ = chart.GetImage();
+
+        Assert.IsTrue(changes == 1);
+
+        lineSeries.IsVisible = false;
+        _ = chart.GetImage();
+
+        lineSeries.IsVisible = true;
+        _ = chart.GetImage();
+
+        values.Add(new(1));
+        _ = chart.GetImage();
+
+        Assert.IsTrue(changes == 2);
+    }
+
+    [TestMethod]
+    public void VisbilityAndPaintsTasks()
+    {
+        var values = new ObservableCollection<DateTimePoint>() { new() };
+        var lineSeries = new ColumnSeries<DateTimePoint>(values);
+        var chart = new SKCartesianChart
+        {
+            Series = [lineSeries],
+            Width = 1000,
+            Height = 1000
+        };
+
+        _ = ChangingPaintTasks.DrawChart(chart, true);
+
+        var canvas = chart.CoreCanvas;
+        var drawables = canvas.DrawablesCount;
+        var geometries = canvas.CountGeometries();
+
+        lineSeries.IsVisible = false;
+        _ = ChangingPaintTasks.DrawChart(chart, true);
+
+        lineSeries.IsVisible = true;
+        _ = ChangingPaintTasks.DrawChart(chart, true);
+
+        Assert.IsTrue(
+           drawables == canvas.DrawablesCount &&
+           geometries == canvas.CountGeometries());
+    }
+}