TabControl with single line TabPanel and Overflow Panel

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>