TabControl with single line TabPanel and Overflow Panel - wpf

Question

I want to alter the functionality of the WPF TabControl to only spawn one line, and create a Overflow Popup for each further item (Like the ToolBar / ToolBarOverflowPanel). The same way tabs are shown in VisualStudio at the moment.
This is what i got:
<Style TargetType="TabControl">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TabControl">
<Grid KeyboardNavigation.TabNavigation="Local">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<controls:OneLineTabPanel x:Name="HeaderPanel"
Grid.Row="0"
Panel.ZIndex="1"
Margin="0"
KeyboardNavigation.TabIndex="1"
Background="Transparent">
</controls:OneLineTabPanel>
......
I did now try to alter the TabPanel (which is used to display the headers), but i can't change its template (as it derives from TabPanel). So I try to derive from some other control instead, but then i can not see any items at all.
How can i get my own ItemsControl to work with the TabControl?

Answer 1

You need to override the whole template of TabControl. Fortunately, it's easy to extract the copy of template using Visual Studio (right click in Document Outline window on TabControl element -> Edit Template -> Edit Copy).In default TabControl template HeaderPanel is defined in the following way:
<TabPanel x:Name="HeaderPanel" Grid.Column="0" IsItemsHost="true" Margin="2,2,2,0" Grid.Row="0" KeyboardNavigation.TabIndex="1" Panel.ZIndex="1"/>
The main idea is to bind TabControl.Items not to the Panel control by setting IsItemsHost="true", but to completely another control type.
For example, to bind to the ToolBar, which has out of the box overflow button feature:
<ToolBar x:Name="HeaderPanel" ItemsSource="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Items}"/>
Here is a full example of TabControl template with ToolBar as a header panel:
<TabControl>
<TabControl.Template>
<ControlTemplate TargetType="{x:Type TabControl}">
<Grid ClipToBounds="true" SnapsToDevicePixels="true" KeyboardNavigation.TabNavigation="Local">
<Grid.ColumnDefinitions>
<ColumnDefinition x:Name="ColumnDefinition0"/>
<ColumnDefinition x:Name="ColumnDefinition1" Width="0"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition x:Name="RowDefinition0" Height="Auto"/>
<RowDefinition x:Name="RowDefinition1" Height="*"/>
</Grid.RowDefinitions>
<!--this will do the trick!!!-->
<ToolBar x:Name="HeaderPanel" ItemsSource="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Items}"/>
<Border x:Name="ContentPanel" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="0" KeyboardNavigation.DirectionalNavigation="Contained" Grid.Row="1" KeyboardNavigation.TabIndex="2" KeyboardNavigation.TabNavigation="Local">
<ContentPresenter x:Name="PART_SelectedContentHost" ContentSource="SelectedContent" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Border>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="TabStripPlacement" Value="Bottom">
<Setter Property="Grid.Row" TargetName="HeaderPanel" Value="1"/>
<Setter Property="Grid.Row" TargetName="ContentPanel" Value="0"/>
<Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
<Setter Property="Height" TargetName="RowDefinition1" Value="Auto"/>
<Setter Property="Margin" TargetName="HeaderPanel" Value="2,0,2,2"/>
</Trigger>
<Trigger Property="TabStripPlacement" Value="Left">
<Setter Property="Grid.Row" TargetName="HeaderPanel" Value="0"/>
<Setter Property="Grid.Row" TargetName="ContentPanel" Value="0"/>
<Setter Property="Grid.Column" TargetName="HeaderPanel" Value="0"/>
<Setter Property="Grid.Column" TargetName="ContentPanel" Value="1"/>
<Setter Property="Width" TargetName="ColumnDefinition0" Value="Auto"/>
<Setter Property="Width" TargetName="ColumnDefinition1" Value="*"/>
<Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
<Setter Property="Height" TargetName="RowDefinition1" Value="0"/>
<Setter Property="Margin" TargetName="HeaderPanel" Value="2,2,0,2"/>
</Trigger>
<Trigger Property="TabStripPlacement" Value="Right">
<Setter Property="Grid.Row" TargetName="HeaderPanel" Value="0"/>
<Setter Property="Grid.Row" TargetName="ContentPanel" Value="0"/>
<Setter Property="Grid.Column" TargetName="HeaderPanel" Value="1"/>
<Setter Property="Grid.Column" TargetName="ContentPanel" Value="0"/>
<Setter Property="Width" TargetName="ColumnDefinition0" Value="*"/>
<Setter Property="Width" TargetName="ColumnDefinition1" Value="Auto"/>
<Setter Property="Height" TargetName="RowDefinition0" Value="*"/>
<Setter Property="Height" TargetName="RowDefinition1" Value="0"/>
<Setter Property="Margin" TargetName="HeaderPanel" Value="0,2,2,2"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</TabControl.Template>
</TabControl>