WPF Flexible TabControl Header - wpf

Question

I want to have a TabControl with multiple TabItems. These TabItems each have a header text. These texts may vary a lot in length (like 5 chars long and 15 chars long).
I want the TabControl to align the headers in one row only.
All tab headers should use the same width, and when there is enough space available, i want them the to use all the space available, up to a MaxWidth, that is the same for all items.
So if i want to use vMaxWidth` of 100 for 7 items, the tab header should be max 700 in width. If there is more space available, it should be ignored.
If there is less space available, i want that space to be distributed equally between the items. If the text gets cut off, i want to use TextWrapping.
I have tried multiple approaches to this problem now, this is my current setup:
<Style x:Key="Style-TabControl-Main" TargetType="{x:Type TabControl}">
<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>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Border BorderThickness="0,0,0,1" Margin="13,0,0,0" BorderBrush="{StaticResource Brush-White}">
<StackPanel Panel.ZIndex="1" x:Name="HeaderPanel" IsItemsHost="True" KeyboardNavigation.TabIndex="1" Background="Transparent"
Orientation="Horizontal"/>
</Border>
<Border x:Name="Border"
Grid.Row="1" Grid.ColumnSpan="2"
KeyboardNavigation.TabNavigation="Local"
KeyboardNavigation.DirectionalNavigation="Contained"
KeyboardNavigation.TabIndex="2"
BorderThickness="{TemplateBinding BorderThickness}"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}">
<ContentPresenter x:Name="PART_SelectedContentHost" ContentSource="SelectedContent" />
</Border>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
And the TabItem Style
<Style x:Key="Style-TabItem-Main" TargetType="{x:Type TabItem}">
<Setter Property="Height" Value="31"/>
<Setter Property="Width" Value="180" />
<Setter Property="Foreground" Value="{DynamicResource Brush-BrightRegular-Foreground}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabItem}">
<Border x:Name="Border" Cursor="Hand"
Margin="2,0,0,0"
BorderThickness="1,1,1,0"
CornerRadius="4,4,0,0"
BorderBrush="{DynamicResource Brush-BrightRegular-Background}"
Background="{DynamicResource Brush-White}">
<ContentPresenter x:Name="Content" VerticalAlignment="Center" HorizontalAlignment="Stretch" ContentSource="Header" RecognizesAccessKey="True"
TextBlock.TextAlignment="Center" TextBlock.FontSize="16" />
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="Foreground" Value="{DynamicResource Brush-White}"/>
<Setter TargetName="Border" Property="Background" Value="{DynamicResource Brush-DefaultDark-Background}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I am using a StackPanel instead of a TabPanel to get rid of the "stacking", that occurs, when you resize a default TabControl. However, i cannot get the rest of my requirements to work. I tried applying a MaxWidth (instead of fixed width) to the TabItem headers, but that of course doesn't work, because the item than shrinks to its minimum required size.

Answer 1

Step 1 (first attempt): Put headers in a single row, and give each header the same width.
This can be achieved by using a UniformGrid instead of the standard TabPanel, and lock its row count to 1. Here is a stripped-down version of your TabControl style:
<Style x:Key="Style-TabControl-Main" TargetType="{x:Type TabControl}">
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabControl}">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<Border>
<UniformGrid x:Name="HeaderPanel" IsItemsHost="True"
Rows="1" />
</Border>
<Border x:Name="Border" Grid.Row="1"
BorderThickness="{TemplateBinding BorderThickness}"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}">
<ContentPresenter x:Name="PART_SelectedContentHost" ContentSource="SelectedContent" />
</Border>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Step 2: Restrict headers to a MaxWidth and apply text wrapping.
The MaxWidth can be set in the TabItem style, along with a HeaderTemplate which wraps text (you can still use your custom ControlTemplate here to style the TabItem parts):
<Style x:Key="Style-TabItem-Main" TargetType="{x:Type TabItem}">
<Setter Property="MaxWidth" Value="100" />
<!--https://social.msdn.microsoft.com/forums/vstudio/en-US/df4f7fc3-f0ec-4ed1-a022-a32650e49cb3/how-to-wrap-header-text-in-tabcontrol-->
<Setter Property="HeaderTemplate" >
<Setter.Value>
<DataTemplate>
<TextBlock Text="{Binding}" TextWrapping="Wrap" />
</DataTemplate>
</Setter.Value>
</Setter>
<Setter Property="Template">
...
</Setter>
</Style>
Troubleshooting: Now, if you apply the MaxWidth in Step 2, you'll probably want to left-align the UniformGrid when the TabControl gets too wide..
<UniformGrid x:Name="HeaderPanel" IsItemsHost="True"
Rows="1" HorizontalAlignment="Left" />
..but you don't want that when the MaxWidth hasn't been reached yet, and the items should stretch across the entire width of the TabControl (aka Step 1). So we need a way to switch that HorizontalAlignment depending on whether the items' MaxWidth (if set) has been reached.
Step 1 (revisited): Let's try to make our own UniformGrid:
public class UniformTabPanel : UniformGrid
{
public UniformTabPanel()
{
this.IsItemsHost = true;
this.Rows = 1;
//Default, so not really needed..
this.HorizontalAlignment = HorizontalAlignment.Stretch;
}
protected override Size MeasureOverride(Size constraint)
{
var totalMaxWidth = this.Children.OfType<TabItem>().Sum(tab => tab.MaxWidth);
if (!double.IsInfinity(totalMaxWidth))
{
this.HorizontalAlignment = (constraint.Width > totalMaxWidth)
? HorizontalAlignment.Left
: HorizontalAlignment.Stretch;
}
return base.MeasureOverride(constraint);
}
}
Now, we can replace the UniformGrid in our TabControl style this new panel:
...
<Border>
<mycontrols:UniformTabPanel x:Name="HeaderPanel" />
</Border>
...
...and the TabControl should function as expeced.

Answer 2

Sphinxx answer is correct, however i needed to add the following code to the UniformTabPanel, to make it work like i want (resize the headers to maxwidth when enough space is available)
I added the following code to the UniformTabPanel, and it now does what i need:
protected override Size MeasureOverride(Size constraint)
{
var children = this.Children.OfType<TabItem>();
var totalMaxWidth = children.Sum(tab => tab.MaxWidth);
if (!double.IsInfinity(totalMaxWidth))
{
this.HorizontalAlignment = (constraint.Width > totalMaxWidth)
? HorizontalAlignment.Left
: HorizontalAlignment.Stretch;
foreach (var child in children)
{
child.Width = this.HorizontalAlignment == System.Windows.HorizontalAlignment.Left
? child.MaxWidth
: Double.NaN;
}
}
return base.MeasureOverride(constraint);
}