WPF tabitem positioning - wpf

Question

What is the proper way of positioning for example three tabitems at the very top left corner and one at the very top right corner of a tab control using WPF?
I have tried to move the fourth tabitem to the right by changing its margin but this doesn't produce a good result; first of all it is cut short and second of all it does not display correctly when selected.

Answer 1

The problem is that the TabPanel, which is used internally by the TabControl to lay out the tabs, does not seem to support what you want. A quick workaround would be to replace the TabPanel by something else, for example, a DockPanel:
<Window x:Class="Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<TabControl>
<TabControl.Template>
<ControlTemplate TargetType="TabControl">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Border BorderThickness="0,0,1,1" BorderBrush="#D0CEBF" Grid.Row="1">
<Border BorderThickness="{TemplateBinding BorderThickness}"
BorderBrush="{TemplateBinding BorderBrush}">
<Border Background="{TemplateBinding Background}">
<ContentPresenter ContentSource="SelectedContent"/>
</Border>
</Border>
</Border>
<DockPanel IsItemsHost="True" LastChildFill="False" Margin="2,2,2,0" />
</Grid>
</ControlTemplate>
</TabControl.Template>
<TabItem Header="Item 1" />
<TabItem Header="Item 2" />
<TabItem Header="Item 3" />
<TabItem Header="Item 4" DockPanel.Dock="Right" />
</TabControl>
</Window>
(Reference: This is a modified version of an MSDN example for styling a TabControl.)
The simple DockPanel doesn't work as smooth as the TabPanel -- the tabs "jump" a bit when switching between them, but this might get you started. Maybe subclassing the TabPanel and overriding the relevant parts would give you a more accurate result; I guess it depends on how much effort you want to put into this.

Answer 2

I found that by inserting an "invisible" tab I could adjust the spacing, (i.e. move the tabs down from the top)
For example:
TabItem Height="100" Visibility="Hidden" <br>
TabItem..... <br>
TabItem.... <br>

Answer 3

You would need to swap out the TabPanel within the TabControl to something custom which provided the desired behavior. None of the default panels are going to provide your desired behavior out of the box.
This will most likely need to involve overriding MeasureOverride and ArrangeOverride to provide the custom placement within the panel that is desired based on the number of items it contains.

Answer 4

This will involve a custom ControlTemplate for the TabControl. I tried an example using a DockPanel as the items host rather than the default TabPanel.
<Style TargetType="{x:Type TabControl}">
<Setter Property="OverridesDefaultStyle"
Value="True" />
<Setter Property="SnapsToDevicePixels"
Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabControl}">
<Grid KeyboardNavigation.TabNavigation="Local">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<DockPanel Name="HeaderPanel"
LastChildFill="False"
Grid.Row="0"
Panel.ZIndex="1"
Margin="0,0,4,-1"
IsItemsHost="True"
KeyboardNavigation.TabIndex="1"
Background="Transparent" />
<Border Name="Border"
Grid.Row="1"
Background="WhiteSmoke"
BorderBrush="Black"
BorderThickness="1"
CornerRadius="2"
KeyboardNavigation.TabNavigation="Local"
KeyboardNavigation.DirectionalNavigation="Contained"
KeyboardNavigation.TabIndex="2">
<ContentPresenter Name="PART_SelectedContentHost"
Margin="4"
ContentSource="SelectedContent" />
</Border>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
The problem is that I don't know of a way of exposing the DockPanel.Dock property to the TabItems outside of the ControlTemplate E.G.
<TabControl Margin="10">
<TabItem Header="Tab One" DockPanel.Dock="Left"/>
<TabItem Header="Tab Two" DocKPanel.Dock="Left"/>
<TabItem Header="Tab Three" DocKPanel.Dock="Left"/>
<TabItem Header="Tab Four" DocKPanel.Dock="Right"/>
</TabControl>
// Note: This does not work!!
I guess you will need to write your own Panel to host the TabItems; Note that this will be quite a lot of work as you will need to handle things like overflow behaviour which is built into the TabPanel.
Even if you did try this I think you would have to write a custom TabControl if you wanted to expose this functionality outside of the ControlTemplate.
If you want to go down this road then see my answer in this post