Shaker/Avalonia/SukiUI.Dock/DockTarget.axaml

<ResourceDictionary xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Design.PreviewWith>
        <Panel Height="300" Width="300">
            <DockTarget>
                <DockTarget.Styles>
                    <Style Selector="^/template/ Panel#PART_TopIndicator">
                        <Setter Property="Opacity" Value="0.0" />
                    </Style>
                    <Style Selector="^/template/ Panel#PART_BottomIndicator">
                        <Setter Property="Opacity" Value="0.0" />
                    </Style>
                    <Style Selector="^/template/ Panel#PART_LeftIndicator">
                        <Setter Property="Opacity" Value="0.0" />
                    </Style>
                    <Style Selector="^/template/ Panel#PART_RightIndicator">
                        <Setter Property="Opacity" Value="0.0" />
                    </Style>
                    <Style Selector="^/template/ Panel#PART_CenterIndicator">
                        <Setter Property="Opacity" Value="0.0" />
                    </Style>
                </DockTarget.Styles>
            </DockTarget>
        </Panel>
    </Design.PreviewWith>

    <ControlTheme TargetType="DockTarget" x:Key="{x:Type DockTarget}">

        <Setter Property="Template">
            <ControlTemplate>
                <Grid
                    ColumnDefinitions="*,*"
                    RowDefinitions="*,*"
                    x:CompileBindings="True"
                    x:Name="PART_IndicatorGrid">
                    <Border
                        ClipToBounds="True"
                        CornerRadius="16"
                        Grid.Column="0"
                        Grid.ColumnSpan="2"
                        Grid.Row="0">
                        <Panel x:Name="PART_TopIndicator" />
                    </Border>
                    <Border
                        ClipToBounds="True"
                        CornerRadius="16"
                        Grid.Column="0"
                        Grid.ColumnSpan="2"
                        Grid.Row="1">
                        <Panel x:Name="PART_BottomIndicator" />
                    </Border>
                    <Border
                        ClipToBounds="True"
                        CornerRadius="16"
                        Grid.Column="0"
                        Grid.Row="0"
                        Grid.RowSpan="2">
                        <Panel
                            Grid.Column="0"
                            Grid.Row="0"
                            Grid.RowSpan="2"
                            x:Name="PART_LeftIndicator" />
                    </Border>
                    <Border
                        ClipToBounds="True"
                        CornerRadius="16"
                        Grid.Column="1"
                        Grid.Row="0"
                        Grid.RowSpan="2">
                        <Panel x:Name="PART_RightIndicator" />
                    </Border>
                    <Border
                        ClipToBounds="True"
                        CornerRadius="16"
                        Grid.Column="0"
                        Grid.ColumnSpan="2"
                        Grid.Row="0"
                        Grid.RowSpan="2">
                        <Panel x:Name="PART_CenterIndicator" />
                    </Border>
                    <Border
                        ClipToBounds="True"
                        CornerRadius="16"
                        Grid.Column="0"
                        Grid.ColumnSpan="2"
                        Grid.Row="0"
                        Grid.RowSpan="2">
                        <Panel x:Name="PART_SelectorPanel">
                            <Grid
                                ColumnDefinitions="*,*,*"
                                RowDefinitions="*,*,*"
                                x:Name="PART_SelectorGrid">
                                <Image
                                    Grid.Column="1"
                                    Grid.Row="0"
                                    x:Name="PART_TopSelector" />
                                <Image
                                    Grid.Column="1"
                                    Grid.Row="2"
                                    x:Name="PART_BottomSelector" />
                                <Image
                                    Grid.Column="0"
                                    Grid.Row="1"
                                    x:Name="PART_LeftSelector" />
                                <Image
                                    Grid.Column="2"
                                    Grid.Row="1"
                                    x:Name="PART_RightSelector" />
                                <Image
                                    Grid.Column="1"
                                    Grid.Row="1"
                                    x:Name="PART_CenterSelector" />
                            </Grid>
                        </Panel>
                    </Border>
                </Grid>
            </ControlTemplate>
        </Setter>

        <Style Selector="^/template/ Grid#PART_SelectorGrid">
            <Setter Property="MaxWidth" Value="125" />
            <Setter Property="MaxHeight" Value="125" />
        </Style>

        <Style Selector="^/template/ Panel#PART_TopIndicator">
            <Setter Property="Background" Value="{DynamicResource SukiPrimaryColor25}" />
            <Setter Property="Opacity" Value="0" />
        </Style>

        <Style Selector="^/template/ Panel#PART_BottomIndicator">
            <Setter Property="Background" Value="{DynamicResource SukiPrimaryColor25}" />
            <Setter Property="Opacity" Value="0" />
        </Style>

        <Style Selector="^/template/ Panel#PART_LeftIndicator">
            <Setter Property="Background" Value="{DynamicResource SukiPrimaryColor25}" />
            <Setter Property="Opacity" Value="0" />
        </Style>

        <Style Selector="^/template/ Panel#PART_RightIndicator">
            <Setter Property="Background" Value="{DynamicResource SukiPrimaryColor25}" />
            <Setter Property="Opacity" Value="0" />
        </Style>

        <Style Selector="^/template/ Panel#PART_CenterIndicator">
            <Setter Property="Background" Value="{DynamicResource SukiPrimaryColor25}" />
            <Setter Property="Opacity" Value="0" />
        </Style>

        <Style Selector="^/template/ Image#PART_TopSelector">
            <Setter Property="Source" Value="avares://Dock.Avalonia/Assets/DockAnchorableTop.png" />
            <Setter Property="Width" Value="40" />
            <Setter Property="Height" Value="40" />
        </Style>

        <Style Selector="^/template/ Image#PART_BottomSelector">
            <Setter Property="Source" Value="avares://Dock.Avalonia/Assets/DockAnchorableBottom.png" />
            <Setter Property="Width" Value="40" />
            <Setter Property="Height" Value="40" />
        </Style>

        <Style Selector="^/template/ Image#PART_LeftSelector">
            <Setter Property="Source" Value="avares://Dock.Avalonia/Assets/DockAnchorableLeft.png" />
            <Setter Property="Width" Value="40" />
            <Setter Property="Height" Value="40" />
        </Style>

        <Style Selector="^/template/ Image#PART_RightSelector">
            <Setter Property="Source" Value="avares://Dock.Avalonia/Assets/DockAnchorableRight.png" />
            <Setter Property="Width" Value="40" />
            <Setter Property="Height" Value="40" />
        </Style>

        <Style Selector="^/template/ Image#PART_CenterSelector">
            <Setter Property="Source" Value="avares://Dock.Avalonia/Assets/DockDocumentInside.png" />
            <Setter Property="Width" Value="40" />
            <Setter Property="Height" Value="40" />
        </Style>

    </ControlTheme>

</ResourceDictionary>