Toolkit2/Toolkit.UI.Controls.Avalonia/TabStrip/TabStrip.axaml

<ResourceDictionary
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:CompileBindings="True">
    <ControlTheme x:Key="{x:Type TabStrip}" TargetType="TabStrip">
        <Setter Property="MinHeight" Value="32" />
        <Setter Property="CornerRadius" Value="{DynamicResource ControlCornerRadius}" />
        <Setter Property="Background" Value="{DynamicResource ControlAltFillColorSecondaryBrush}" />
        <Setter Property="BorderBrush" Value="{DynamicResource ControlStrokeColorDefaultBrush}" />
        <Setter Property="BorderThickness" Value="1" />
        <Setter Property="HorizontalAlignment" Value="Left" />
        <Setter Property="VerticalAlignment" Value="Center" />
        <Setter Property="IsTabStop" Value="False" />
        <Setter Property="KeyboardNavigation.TabNavigation" Value="Once" />
        <Setter Property="Padding" Value="-1" />
        <Setter Property="BackgroundSizing" Value="InnerBorderEdge" />
        <Setter Property="ItemsPanel">
            <ItemsPanelTemplate>
                <WrapPanel />
            </ItemsPanelTemplate>
        </Setter>
        <Setter Property="Template">
            <ControlTemplate>
                <Border
                    Height="{TemplateBinding Height}"
                    VerticalAlignment="Stretch"
                    Background="{TemplateBinding Background}"
                    BackgroundSizing="{TemplateBinding BackgroundSizing}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}"
                    CornerRadius="{TemplateBinding CornerRadius}">
                    <ItemsPresenter
                        Margin="{TemplateBinding Padding}"
                        VerticalAlignment="Stretch"
                        ItemsPanel="{TemplateBinding ItemsPanel}" />
                </Border>
            </ControlTemplate>
        </Setter>
    </ControlTheme>
    <ControlTheme x:Key="{x:Type TabStripItem}" TargetType="TabStripItem">
        <Setter Property="CornerRadius" Value="{DynamicResource ControlCornerRadius}" />
        <Setter Property="HorizontalContentAlignment" Value="Stretch" />
        <Setter Property="FontFamily" Value="{DynamicResource ContentControlThemeFontFamily}" />
        <Setter Property="Background" Value="{DynamicResource ControlFillColorTransparentBrush}" />
        <Setter Property="BorderBrush" Value="{DynamicResource ControlFillColorTransparentBrush}" />
        <Setter Property="Foreground" Value="{DynamicResource TextFillColorPrimaryBrush}" />
        <Setter Property="FontWeight" Value="Normal" />
        <Setter Property="Height" Value="32" />
        <Setter Property="MinWidth" Value="60" />
        <Setter Property="FontSize" Value="{DynamicResource ControlContentThemeFontSize}" />
        <Setter Property="VerticalAlignment" Value="Stretch" />
        <Setter Property="BackgroundSizing" Value="InnerBorderEdge" />
        <Setter Property="Template">
            <ControlTemplate>
                <Border
                    Name="Root"
                    VerticalAlignment="{TemplateBinding VerticalAlignment}"
                    Background="{TemplateBinding Background}"
                    BackgroundSizing="{TemplateBinding BackgroundSizing}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="1"
                    CornerRadius="{TemplateBinding CornerRadius}"
                    TemplatedControl.IsTemplateFocusTarget="True">
                    <Border.Transitions>
                        <Transitions>
                            <BrushTransition Property="Background" Duration="00:00:00.083" />
                        </Transitions>
                    </Border.Transitions>

                    <Panel>
                        <Border
                            Name="Hover"
                            Margin="3"
                            Background="Transparent"
                            CornerRadius="{TemplateBinding CornerRadius}">
                            <Border.Transitions>
                                <Transitions>
                                    <BrushTransition Property="Background" Duration="00:00:00.083" />
                                    <TransformOperationsTransition
                                        Easing="0,0 0,1"
                                        Property="RenderTransform"
                                        Duration="00:00:00.167" />
                                </Transitions>
                            </Border.Transitions>
                        </Border>

                        <ContentPresenter
                            Name="PART_ContentPresenter"
                            Margin="11,5,11,6"
                            HorizontalAlignment="Center"
                            VerticalAlignment="Center"
                            HorizontalContentAlignment="Center"
                            VerticalContentAlignment="Center"
                            Content="{TemplateBinding Content}"
                            ContentTemplate="{TemplateBinding ContentTemplate}"
                            FontWeight="{TemplateBinding FontWeight}"
                            Foreground="{TemplateBinding Foreground}" />

                        <Rectangle
                            Name="Pill"
                            Width="4"
                            Height="3"
                            HorizontalAlignment="Center"
                            VerticalAlignment="Bottom"
                            Fill="{DynamicResource PivotHeaderItemSelectedPipeFill}"
                            Opacity="0"
                            RadiusX="0.5"
                            RadiusY="1"
                            RenderTransform="scaleX(4)">
                            <Rectangle.Transitions>
                                <Transitions>
                                    <TransformOperationsTransition
                                        Easing="0,0 0,1"
                                        Property="RenderTransform"
                                        Duration="00:00:00.167" />
                                </Transitions>
                            </Rectangle.Transitions>
                        </Rectangle>

                    </Panel>
                </Border>
            </ControlTemplate>
        </Setter>


        <Style Selector="^:pointerover">
            <Style Selector="^ /template/ Border#Hover">
                <Setter Property="Background" Value="{DynamicResource SubtleFillColorSecondaryBrush}" />
            </Style>
        </Style>

        <Style Selector="^:pressed">
            <Style Selector="^ /template/ Border#Hover">
                <Setter Property="Background" Value="{DynamicResource SubtleFillColorTertiaryBrush}" />
                <Setter Property="RenderTransform" Value="scale(0.96)" />
            </Style>
            <Style Selector="^ /template/ ContentPresenter#PART_ContentPresenter">
                <Setter Property="Foreground" Value="{DynamicResource TextFillColorSecondaryBrush}" />
            </Style>
        </Style>

        <Style Selector="^:selected">
            <Style Selector="^ /template/ Border#Hover">
                <Setter Property="IsVisible" Value="False" />
            </Style>
            <Style Selector="^ /template/ Border#Root">
                <Setter Property="Background" Value="{DynamicResource ControlFillColorDefaultBrush}" />
                <Setter Property="BorderBrush" Value="{DynamicResource ControlElevationBorderBrush}" />
            </Style>
            <Style Selector="^ /template/ ContentPresenter#PART_ContentPresenter">
                <Setter Property="Foreground" Value="{DynamicResource TextFillColorPrimaryBrush}" />
            </Style>
            <Style Selector="^ /template/ Rectangle#Pill">
                <Setter Property="Opacity" Value="1" />
            </Style>

            <Style Selector="^:pressed /template/ Rectangle#Pill">
                <Setter Property="RenderTransform" Value="scaleX(1)" />
            </Style>
        </Style>

        <Style Selector="^:disabled">
            <Style Selector="^ /template/ Border#Hover">
                <Setter Property="IsVisible" Value="False" />
            </Style>
            <Style Selector="^ /template/ Border#Root">
                <Setter Property="Background" Value="{DynamicResource ControlFillColorDisabledBrush}" />
                <Setter Property="BorderBrush" Value="{DynamicResource ControlAltFillColorSecondaryBrush}" />
            </Style>
            <Style Selector="^ /template/ ContentPresenter#PART_ContentPresenter">
                <Setter Property="Foreground" Value="{DynamicResource TextFillColorDisabledBrush}" />
            </Style>
        </Style>
    </ControlTheme>
</ResourceDictionary>