Tab-shaped border needs clipping - wpf

Question

I have a spec for an application with three columns where the central one bows in into an inverted tab shape.
I have the basics figured out:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="371*"></ColumnDefinition>
<ColumnDefinition Width="469*"></ColumnDefinition>
<ColumnDefinition Width="371*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Grid Grid.Column="0">
<Grid.RowDefinitions>
<RowDefinition Height="83*"></RowDefinition>
<RowDefinition Height="309*"></RowDefinition>
<RowDefinition Height="223*"></RowDefinition>
<RowDefinition Height="67*"></RowDefinition>
</Grid.RowDefinitions>
<TextBox Background="Transparent" Grid.Row="0"
Text="Foo" HorizontalAlignment="Center" VerticalAlignment="Center" >
</TextBox>
<Border Grid.Row="0" BorderBrush="Red" BorderThickness="0,0,0,4"></Border>
<Grid Grid.Column="1">
<Grid.RowDefinitions>
<RowDefinition Height="221*"></RowDefinition>
<RowDefinition Height="171*"></RowDefinition>
<RowDefinition Height="290*"></RowDefinition>
</Grid.RowDefinitions>
<Grid Grid.Row="0">
</Grid>
<Border Grid.Row="0" BorderBrush="Red" BorderThickness="4,0,4,4" CornerRadius="50" >
</Border>
</Grid>
</Grid>
But the inverted tab border is in need of clipping about 60% of the way down. I can of course position an element on top of it but that seems like the wrong solution and I'd like to avoid it.
I've looked at the Border.Clip property but can't quite figure out how to work with it nor find much in the way of documentation. What do I need to do here?

Answer 1

There's a bunch of different ways you can accomplish this, some will be more appropriate for potential resizing considerations than others etc. Here's just a few potential solution examples.
<StackPanel>
<!-- added -->
<Grid Background="LightBlue" Height="100">
<Grid.RowDefinitions>
<RowDefinition Height="50"/>
<RowDefinition Height="2"/>
<RowDefinition Height="30"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Rectangle Grid.ColumnSpan="3"
Fill="DarkBlue"/>
<Rectangle Grid.Row="1" Grid.ColumnSpan="3"
Fill="Yellow"/>
<Border Grid.Row="1" Grid.RowSpan="2" Grid.Column="1"
Background="DarkBlue"
BorderBrush="Yellow" BorderThickness="2,0,2,2"
CornerRadius="0,0,20,20"/>
</Grid>
<!-//-->
<Grid Background="LightBlue" Height="100">
<Grid.RowDefinitions>
<RowDefinition Height="50"/>
<RowDefinition Height="30"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Rectangle Grid.ColumnSpan="3"
Fill="DarkBlue"/>
<Rectangle Grid.ColumnSpan="3" VerticalAlignment="Bottom" Height="2"
Fill="Yellow"/>
<Border Grid.Row="1" Grid.RowSpan="2" Grid.Column="1"
Background="DarkBlue" Margin="0,-2,0,0"
BorderBrush="Yellow" BorderThickness="2,0,2,2"
CornerRadius="0,0,20,20"/>
</Grid>
<!-- Or another, or another, or another... -->
<Grid Background="LightBlue" Height="100">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Border Grid.ColumnSpan="3" Height="50"
VerticalAlignment="Top" Background="DarkBlue"
BorderBrush="Yellow" BorderThickness="0,0,0,2"/>
<Border Grid.Column="1" Height="80" CornerRadius="20"
VerticalAlignment="Top" Background="DarkBlue" BorderThickness="2,0,2,2">
<Border.BorderBrush>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="DarkBlue" Offset="0.6"/>
<GradientStop Color="#FFFFFF00" Offset="0.6"/>
</LinearGradientBrush>
</Border.BorderBrush>
</Border>
</Grid>
<Grid Background="LightBlue" Height="100">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Border Grid.Column="1" Height="80" CornerRadius="20"
VerticalAlignment="Top" Background="DarkBlue"
BorderBrush="Yellow" BorderThickness="2,0,2,2"/>
<Border Grid.ColumnSpan="3" Height="50"
VerticalAlignment="Top" Background="DarkBlue"
BorderBrush="Yellow" BorderThickness="0,0,0,2"/>
<Rectangle Grid.Column="1" Height="51" Margin="2,0"
VerticalAlignment="Top" Fill="DarkBlue"/>
</Grid>
<Grid Background="LightBlue" Height="100">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Border Grid.ColumnSpan="3" Height="50"
VerticalAlignment="Top" Background="DarkBlue"
BorderBrush="Yellow" BorderThickness="0,0,0,2"/>
<Border Grid.Column="1" Height="80" CornerRadius="20"
VerticalAlignment="Top" Background="DarkBlue"
BorderBrush="Yellow" BorderThickness="2,0,2,2"
Clip="M0,47.7 L175,47.7 L175,80 L0,80 z"/>
</Grid>
</StackPanel>

Answer 2

CornerRadius has a constructor that can take 4 values for the radius of each corner: top-left, top-right, bottom-right, bottom-left.
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="9*" />
<RowDefinition Height="1*" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<TextBox Background="Transparent" Grid.Row="0" Grid.Column="0"
Text="Foo" HorizontalAlignment="Center" VerticalAlignment="Center" />
<Border Grid.Row="1" Grid.Column="1" BorderBrush="Red" BorderThickness="4,0,4,4" CornerRadius="0, 0, 50, 50" />
</Grid>
Another option (probably the one I would choose) is to use a TabControl, put the tab on the bottom and center it.
<TabControl TabStripPlacement="Bottom" Background="DarkBlue" BorderBrush="Yellow" Margin="3" >
<TabControl.Resources>
<Style TargetType="{x:Type TabPanel}">
<Setter Property="HorizontalAlignment" Value="Center" />
</Style>
</TabControl.Resources>
<TabItem Header="Test" Background="DarkBlue" BorderBrush="Yellow" Foreground="Yellow" >
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBox Grid.Row="1" Text="Foo" />
</Grid>
</TabItem>
</TabControl>