Nitrox/Nitrox.Launcher/Models/Controls/CustomTitlebar.axaml

<ResourceDictionary
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:controls="clr-namespace:Nitrox.Launcher.Models.Controls"
    xmlns:converters="clr-namespace:Nitrox.Launcher.Models.Converters">
    <Design.PreviewWith>
        <StackPanel Width="200">
            <controls:CustomTitlebar
                Background="IndianRed"
                CanMaximize="False"
                CanMinimize="False" />
            <controls:CustomTitlebar
                Background="ForestGreen"
                CanMaximize="True"
                CanMinimize="False" />
            <controls:CustomTitlebar Background="CornflowerBlue" CanMaximize="False" />
            <controls:CustomTitlebar Background="Violet" />
        </StackPanel>
    </Design.PreviewWith>

    <ControlTheme x:Key="{x:Type controls:CustomTitlebar}" TargetType="controls:CustomTitlebar">
        <Setter Property="Template">
            <ControlTemplate>
                <Panel Background="Transparent">
                    <Border
                        Padding="5,2"
                        HorizontalAlignment="Left"
                        IsVisible="{TemplateBinding ShowTitle}">
                        <TextBlock
                            VerticalAlignment="Stretch"
                            Text="{Binding $parent[Window].Title}"
                            TextAlignment="Center" />
                    </Border>
                    <StackPanel>
                        <Button
                            x:Name="PART_MinimizeButton"
                            Classes.leftOff1="{x:True}"
                            Classes.leftOff2="{x:True}"
                            Command="{Binding MinimizeCommand, RelativeSource={RelativeSource TemplatedParent}}"
                            IsVisible="{TemplateBinding CanMinimize}">
                            <Svg Classes="theme" Path="/Assets/Icons/minimize.svg" />
                        </Button>
                        <Button
                            x:Name="PART_MaximizeButton"
                            Classes.leftOff1="{Binding !#PART_MinimizeButton.IsVisible}"
                            Classes.leftOff2="{x:True}"
                            Command="{Binding ToggleMaximizeCommand, RelativeSource={RelativeSource TemplatedParent}}">
                            <Button.IsVisible>
                                <MultiBinding Converter="{x:Static BoolConverters.And}">
                                    <TemplateBinding Property="CanMaximize" />
                                    <Binding Path="$parent[Window].CanResize" />
                                </MultiBinding>
                            </Button.IsVisible>
                            <Svg
                                Classes="theme"
                                Classes.maximize="{Binding $parent[Window].WindowState, Converter={converters:EqualityConverter}, ConverterParameter={x:Static WindowState.Normal}}"
                                Classes.restore="{Binding $parent[Window].WindowState, Converter={converters:EqualityConverter}, ConverterParameter={x:Static WindowState.Maximized}}" />
                        </Button>
                        <Button
                            x:Name="PART_CloseButton"
                            Classes="close"
                            Classes.leftOff1="{Binding !#PART_MinimizeButton.IsVisible}"
                            Classes.leftOff2="{Binding !#PART_MaximizeButton.IsVisible}"
                            Command="{Binding CloseCommand, RelativeSource={RelativeSource TemplatedParent}}">
                            <Svg Classes="theme" Path="/Assets/Icons/close.svg" />
                        </Button>
                    </StackPanel>
                </Panel>
            </ControlTemplate>
        </Setter>

        <!--  Default template values  -->
        <Setter Property="Background" Value="Black" />
        <Setter Property="Cursor" Value="Hand" />
        <Setter Property="ZIndex" Value="100" />
        <Setter Property="Height" Value="28" />
        <Setter Property="HorizontalAlignment" Value="Stretch" />
        <Setter Property="VerticalAlignment" Value="Top" />
        <Setter Property="ShowTitle" Value="False" />

        <Style Selector="^ /template/ StackPanel">
            <Setter Property="Orientation" Value="Horizontal" />
            <Setter Property="HorizontalAlignment" Value="Right" />

            <Style Selector="^ >  Button">
                <Setter Property="Width" Value="46" />
                <Setter Property="BorderThickness" Value="0" />
                <Setter Property="Opacity" Value="1" />

                <!--  This selector force overrides button style. TODO: fix ButtonStyle.axaml so this isn't necessary and move setters out of this selector.  -->
                <Style Selector="^:nth-child(1n)">
                    <Setter Property="CornerRadius" Value="0" />
                    <Setter Property="Background" Value="{TemplateBinding Background}" />
                </Style>

                <!--  Button[IsVisible=True]:nth-child(1) doesn't work to filter only visible buttons. Here, leftOff1 is used to check if previous button is on and leftOff2 is the next one over that.  -->
                <Style Selector="^.leftOff1.leftOff2">
                    <Setter Property="CornerRadius" Value="0 0 0 5" />
                </Style>

                <Style Selector="^ >  :is(Control)">
                    <Setter Property="Height" Value="11" />
                    <Setter Property="IsHitTestVisible" Value="False" />
                    <Setter Property="Opacity" Value="1" />
                </Style>

                <Style Selector="^.close:pointerover">
                    <Setter Property="Background" Value="Red" />
                </Style>
            </Style>

            <Style Selector="^ Svg.maximize">
                <Setter Property="Path" Value="/Assets/Icons/maximize.svg" />
            </Style>
            <Style Selector="^ Svg.restore">
                <Setter Property="Path" Value="/Assets/Icons/restore.svg" />
            </Style>
        </Style>

    </ControlTheme>
</ResourceDictionary>