WPF-61990 Update readme

README.md

@@ -1,13 +1,89 @@
-# How to add multiple trackball in Xamarin.iOS Chart
+# How to add multiple trackball in Xamarin.iOS Chart (SfChart)?
 
 This example demonstrates how to add the multiple trackball to a single chart and drag them independently to view the information of different data points at the same time in Xamarin.iOS chart.
 
-See [How to add multiple trackball in Xamarin.iOS Chart](https://www.syncfusion.com/kb/10839?utm_medium=listing&utm_source=github-examples) for more details.
+SFChart allows you add multiple trackballs to a single chart and drag them independently to view the information of different data points at the same time.
 
-## <a name="requirements-to-run-the-demo"></a>Requirements to run the demo ##
+The following steps describe how to add multiple trackballs to SFChart.
 
-* [Visual Studio 2017](https://visualstudio.microsoft.com/downloads/) or [Visual Studio for Mac](https://visualstudio.microsoft.com/vs/mac/).
-* Xamarin add-ons for Visual Studio (available via the Visual Studio installer).
+**Step 1:** Create a custom ChartTrackballBehaviorExt class, which is inherited from **SFChartTrackballBehavior**.
+```
+public class ChartTrackballBehaviorExt : SFChartTrackballBehavior
+{
+}
+```
+
+**Step 2:** Create an instance of ChartTrackballBehaviorExt and add it to the **Behaviors** collection.
+```
+ChartTrackballBehaviorExt trackballBehavior1 = new ChartTrackballBehaviorExt();
+ChartTrackballBehaviorExt trackballBehavior2 = new ChartTrackballBehaviorExt();
+chart.Behaviors.Add(trackballBehavior1);
+chart.Behaviors.Add(trackballBehavior2);
+```
+
+**Step 3:** Activate the multiple trackballs at load time using the **[Show](https://help.syncfusion.com/cr/xamarin-ios/Syncfusion.SfChart.iOS.SFChartTrackballBehavior.html#Syncfusion_SfChart_iOS_SFChartTrackballBehavior_Show_CoreGraphics_CGPoint_)** method.
+```
+public override void ViewDidAppear(bool animated)
+{
+    base.ViewDidAppear(animated);
+
+    trackballBehavior1.Show(pointX, pointY);
+    trackballBehavior2.Show(pointX, pointY);
+}
+```
+
+**Step 4:** Set [ActivationMode](https://help.syncfusion.com/cr/xamarin-ios/Syncfusion.SfChart.iOS.SFChartTrackballBehavior.html#Syncfusion_SfChart_iOS_SFChartTrackballBehavior_ActivationMode) to [None](https://help.syncfusion.com/cr/Syncfusion.SfChart.iOS.SFChartTrackballActivationMode.html) to restrict the default movement of the trackball behavior.
+```
+trackballBehavior1.ActivationMode = SFChartTrackballActivationMode.None;
+trackballBehavior2.ActivationMode = SFChartTrackballActivationMode.None;
+```
+
+**Step 5:** Interact with multiple trackballs by overriding the touch methods of SFChartTrackballBehavior class and the [HitTest](https://help.syncfusion.com/cr/xamarin-ios/Syncfusion.SfChart.iOS.SFChartTrackballBehavior.html#Syncfusion_SfChart_iOS_SFChartTrackballBehavior_HitTest_System_Single_System_Single_) method. The HitTest method is used to find the trackball that is currently activated by user.
+```
+public class ChartTrackballBehaviorExt : SFChartTrackballBehavior
+{
+    bool isActivated = false;
+
+    public override void TouchesBegan(NSSet touches, UIEvent uiEvent)
+    {
+        if (touches?.AnyObject is UITouch touch)
+        {
+            CGPoint location = touch.LocationInView(Chart);
+            if (HitTest((float)location.X, (float)location.Y))
+            {
+                isActivated = true;
+                base.TouchesBegan(touches, uiEvent);
+            }
+        }
+    }
+
+    public override void TouchesMoved(NSSet touches, UIEvent uiEvent)
+    {
+        if (isActivated)
+        {
+            if (touches?.AnyObject is UITouch touch)
+            {
+                CGPoint location = touch.LocationInView(Chart);
+                Show(location);
+                base.TouchesMoved(touches, uiEvent);
+            }
+        }
+    }
+
+    public override void TouchesEnded(NSSet touches, UIEvent uiEvent)
+    {
+        isActivated = false;
+    }
+}
+```
+
+**Step 6:** Tap and drag each trackball separately to view the data points at different positions simultaneously.
+
+## Output:
+
+![Multiple trackball in Xamarin.iOS Chart](https://user-images.githubusercontent.com/53489303/200624559-4d790a1d-35fb-4aa6-b977-028186b2b56c.gif)
+
+KB article - [How to add multiple trackball in Xamarin.iOS Chart?](https://www.syncfusion.com/kb/10839/how-to-add-multiple-trackball-in-xamarin-ios-chart)
 
 ## <a name="troubleshooting"></a>Troubleshooting ##
 ### Path too long exception