add repro for popup transparency pointer event issue.

samples/ControlCatalog/Pages/CheckBoxPage.xaml

@@ -1,28 +1,25 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             x:Class="ControlCatalog.Pages.CheckBoxPage">
-  <StackPanel Orientation="Vertical" Spacing="4">
-    <TextBlock Classes="h2">A check box control</TextBlock>
+             x:Class="ControlCatalog.Pages.CheckBoxPage" Background="White">
+  <Grid>
+    <TextBlock x:Name="myTb" />
+    <ToggleButton x:Name="TogglePopupButton" Height="30" Width="150" HorizontalAlignment="Left">
+      <StackPanel>
+        <TextBlock VerticalAlignment="Center" HorizontalAlignment="Center">
+          <Run Text="Is button toggled? " />
+          <Run Text="{Binding IsChecked, ElementName=TogglePopupButton}" />
+        </TextBlock>
 
-    <StackPanel Orientation="Horizontal"
-                Margin="0,16,0,0"
-                HorizontalAlignment="Center"
-                Spacing="16">
-      <StackPanel Orientation="Vertical"
-                  Spacing="16">
-        <CheckBox>_Unchecked</CheckBox>
-        <CheckBox IsChecked="True">_Checked</CheckBox>
-        <CheckBox IsChecked="{x:Null}">_Indeterminate</CheckBox>
-        <CheckBox IsChecked="True" IsEnabled="False">Disabled</CheckBox>
-      </StackPanel>
-      <StackPanel Orientation="Vertical"
-                  HorizontalAlignment="Center"
-                  Spacing="16">
-        <CheckBox IsChecked="False" IsThreeState="True">Three State: Unchecked</CheckBox>
-        <CheckBox IsChecked="True" IsThreeState="True">Three State: Checked</CheckBox>
-        <CheckBox IsChecked="{x:Null}" IsThreeState="True">Three State: Indeterminate</CheckBox>
-        <CheckBox IsChecked="{x:Null}" IsThreeState="True" IsEnabled="False">Three State: Disabled</CheckBox>
+        <Popup Name="myPopup" IsOpen="{Binding IsChecked, ElementName=TogglePopupButton}">
+          <Panel>
+            <Border BorderThickness="1" IsHitTestVisible="False" Margin="0" BorderBrush="Red" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" />
+
+            <TextBlock Name="myPopupText" Background="LightBlue" Foreground="Blue" Padding="30" Margin="150">
+              Popup Text
+            </TextBlock>
+          </Panel>
+        </Popup>
       </StackPanel>
-    </StackPanel>
-  </StackPanel>
+    </ToggleButton>
+  </Grid>
 </UserControl>

samples/ControlCatalog/Pages/CheckBoxPage.xaml.cs

@@ -1,18 +1,31 @@
 using Avalonia.Controls;
+using Avalonia.Input;
 using Avalonia.Markup.Xaml;
 
 namespace ControlCatalog.Pages
 {
-    public class CheckBoxPage : UserControl
+    public partial class CheckBoxPage : UserControl
     {
+        private TextBlock myTb;
+
         public CheckBoxPage()
         {
             this.InitializeComponent();
+
+            myTb = this.FindControl<TextBlock>("myTb");
+
         }
 
         private void InitializeComponent()
         {
             AvaloniaXamlLoader.Load(this);
         }
+
+        protected override void OnPointerMoved(PointerEventArgs e)
+        {
+            base.OnPointerMoved(e);
+
+            myTb.Text = e.GetPosition(this).ToString();
+        }
     }
 }