finally got SplitButton popup behavior working properly.

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/SplitButton/SplitButton.cs

@@ -3,7 +3,6 @@ using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Input;
 using System.Windows.Controls.Primitives;
-using System.Diagnostics;
 
 namespace Microsoft.Windows.Controls
 {
@@ -74,8 +73,7 @@ namespace Microsoft.Windows.Controls
 
         protected virtual void OnIsOpenChanged(bool oldValue, bool newValue)
         {
-            // TODO: Add your property changed side-effects. Descendants can override as well.
-            Debug.WriteLine("{0} : {1}", oldValue, newValue);
+            // TODO: check for cancel event args on an OnOpening event
         }
 
         #endregion //IsOpen
@@ -89,25 +87,24 @@ namespace Microsoft.Windows.Controls
             base.OnApplyTemplate();
 
             _toggleButton = (ToggleButton)GetTemplateChild("PART_ToggleButton");
-            _toggleButton.Click += new RoutedEventHandler(_toggleButton_Click);            
+            _toggleButton.Click += ToggleButton_Click;      
             
-
             _popup = (Popup)GetTemplateChild("PART_Popup");
             _popup.Opened += Popup_Opened;
         }
 
-        void _toggleButton_Click(object sender, RoutedEventArgs e)
-        {           
-            Debug.WriteLine("IsOpen : {0}  |  IsChecked : {1}", IsOpen, _toggleButton.IsChecked);
-        }
-
         #endregion //Base Class Overrides
 
         #region Event Handlers
 
+        void ToggleButton_Click(object sender, RoutedEventArgs e)
+        {
+
+        }
+
         void Popup_Opened(object sender, EventArgs e)
         {
-            Mouse.Capture(this, CaptureMode.SubTree);
+            
         }
 
         private void OnKeyDown(object sender, KeyEventArgs e)

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/Themes/Generic.xaml

@@ -1220,9 +1220,9 @@
                                         <ContentPresenter Name="Content" Margin="{TemplateBinding Padding}" Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" RecognizesAccessKey="true" />
                                     </Button>
                                     <ToggleButton x:Name="PART_ToggleButton" Grid.Column="1" IsTabStop="False"                                                  
-                                                  Style="{StaticResource SplitButtonDropDownStyle}" 
-                                                  ClickMode="Press"
-                                                  IsChecked="{Binding IsOpen, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"  >
+                                                  Style="{StaticResource SplitButtonDropDownStyle}"
+                                                  IsChecked="{Binding IsOpen, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"
+                                                  IsHitTestVisible="{Binding IsOpen, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource InverseBoolConverter}}">
                                         <Grid x:Name="arrowGlyph" IsHitTestVisible="False">
                                             <Path Width="7" Height="4" Data="M 0,1 C0,1 0,0 0,0 0,0 3,0 3,0 3,0 3,1 3,1 3,1 4,1 4,1 4,1 4,0 4,0 4,0 7,0 7,0 7,0 7,1 7,1 7,1 6,1 6,1 6,1 6,2 6,2 6,2 5,2 5,2 5,2 5,3 5,3 5,3 4,3 4,3 4,3 4,4 4,4 4,4 3,4 3,4 3,4 3,3 3,3 3,3 2,3 2,3 2,3 2,2 2,2 2,2 1,2 1,2 1,2 1,1 1,1 1,1 0,1 0,1 z" Fill="#FF000000"/>
                                         </Grid>