WPF scrollbar location - wpf

Question

I have a Stackpanel inside of a TabItem that is part of a TabControl. As things get added to the StackPanel, I have a custom vertical ScrollBar appear. Currently its appearing inside the TabItem control "on top of" the stack panel. I want to move the scroll bar's location to outside of the TabControl altogether. I've tried to do some things with margin, but as the ScrollBar gets pushed outside the edge of the TabControl, it just gets clipped, and no amount of me messing with zindex has resulted in any success. Any help would be appreciative. - Leif
<TabItem Name="tabItem1" Background="{x:Null}" BorderBrush="#FF48D6EE" IsSelected="True">
<TabItem.Template>
<ControlTemplate TargetType="{x:Type TabItem}">
<Grid>
<Border Name="Tab1" Margin="0,0,0,0" BorderBrush="#FF002648" BorderThickness="1,0,1,1" CornerRadius="0,0,3,3">
<Border.Effect>
<DropShadowEffect ShadowDepth="0" Color="#FF3Ed3F4" Opacity=".5" BlurRadius="2"/>
</Border.Effect>
</Border>
<HeaderedContentControl Name="TabHeaderText"
TextBlock.FontFamily="Aharoni"
TextBlock.FontWeight="Bold"
TextBlock.Foreground="#FF214c6d"
TextBlock.FontSize="18"
Header="Tab1"
Margin="10,1,10,0"
VerticalAlignment="Center"
HorizontalAlignment="Center"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter TargetName="Tab1" Property="Background">
<Setter.Value>
<LinearGradientBrush StartPoint=".5,0" EndPoint=".5,1">
<GradientStop Color="#FF000a13" Offset="0" />
<GradientStop Color="#FF06335c" Offset="0.5" />
<GradientStop Color="#FF33bbdb" Offset="1" />
</LinearGradientBrush>
</Setter.Value>
</Setter>
<Setter TargetName="Tab1" Property="Effect">
<Setter.Value>
<DropShadowEffect ShadowDepth="0" Color="#FF3ccbee" Opacity="1" BlurRadius="5"/>
</Setter.Value>
</Setter>
<Setter TargetName="Tab1" Property="BorderBrush" Value="#FF48d6ed"/>
<Setter TargetName="Tab1" Property="BorderThickness" Value="1,0,1,1" />
<Setter TargetName="Tab1" Property="Header">
<Setter.Value>
<custom:OutlinedText FontSize="18"
FontFamily="Aharoni"
FontWeight="ExtraBold"
Fill="Black"
Stroke="#ff3bb1db"
StrokeThickness=".75"
Text="Tab1"/>
</Setter.Value>
</Setter>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</TabItem.Template>
<ScrollViewer HorizontalScrollBarVisibility="Disabled"
VerticalScrollBarVisibility="Auto"
Template="{StaticResource ScrollViewerControlTemplate}">
<StackPanel Name="panelTab1" HorizontalAlignment="Left" VerticalAlignment="Top"/>
</ScrollViewer>
</TabItem>

Answer 1

We ran into a similar issue. What we discovered is that WPF does not draw things with negative margins, when they are clipped. Clipping comes into play when one of the elements that contains the TabItem control has a MinHeight set, and the window shrinks below the MinHeight. By default the scroll bar uses a negative margin for the PART_VerticalScrollBar.
The solution is to make sure that you do not have MinHeight set on any of the containers that may contain your TabItem. If you need to use MinHeight, set it on the top level view.
The Snoop tool is very helpful for debugging WPF layout issues.
http://snoopwpf.codeplex.com/