Ursa.Avalonia/src/Ursa.Themes.Semi/Controls/TreeComboBox.axaml

<ResourceDictionary xmlns="https://github.com/avaloniaui"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:u="https://irihi.tech/ursa"
                    xmlns:iri="https://irihi.tech/shared"
                    xmlns:converters="clr-namespace:Avalonia.Controls.Converters;assembly=Avalonia.Controls"
                    xmlns:converters1="clr-namespace:Ursa.Themes.Semi.Converters">
    <!-- Add Resources Here -->
    
    <converters:MarginMultiplierConverter x:Key="LeftMarginConverter" Indent="20" Left="True"/>
    <converters1:SelectedItemTemplateConverter x:Key="SelectedItemTemplateConverter"/>
    
    <ControlTheme x:Key="{x:Type u:TreeComboBox}" TargetType="u:TreeComboBox">
        <Setter Property="Padding" Value="{DynamicResource ComboBoxSelectorDefaultPadding}"/>
        <Setter Property="FocusAdorner" Value="{x:Null}"/>
        <Setter Property="Background" Value="{DynamicResource ComboBoxSelectorBackground}"/>
        <Setter Property="CornerRadius" Value="{DynamicResource ComboBoxSelectorCornerRadius}"/>
        <Setter Property="VerticalContentAlignment" Value="Center"></Setter>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="Cursor" Value="Hand"/>
        <Setter Property="Template">
            <ControlTemplate TargetType="u:TreeComboBox">
                <Grid ColumnDefinitions="*, Auto, Auto">
                    <Border Grid.Column="0" 
                            Name="Background"
                            Grid.ColumnSpan="3" 
                            Background="{TemplateBinding Background}" 
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}"
                            CornerRadius="{TemplateBinding CornerRadius}"
                            MinHeight="32"
                            />
                    <TextBlock 
                        Name="PlaceholderTextBlock" 
                        Grid.Column="0"
                        Margin="{TemplateBinding Padding}"
                        HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                        VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                        TextTrimming="CharacterEllipsis"
                        Foreground="{TemplateBinding Foreground}"
                        Opacity="0.3"
                        IsVisible="{TemplateBinding SelectionBoxItem, Converter={x:Static ObjectConverters.IsNull}}"
                        Text="{TemplateBinding Watermark}"
                        ></TextBlock>
                    <ContentPresenter 
                        Grid.Column="0" 
                        Margin="{TemplateBinding Padding}"
                        VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                        VerticalAlignment="Center"
                        Content="{TemplateBinding SelectionBoxItem}">
                        <ContentPresenter.ContentTemplate>
                            <MultiBinding Converter="{x:Static converters1:SelectedItemTemplateConverter.Instance}">
                                <TemplateBinding Property="SelectedItemTemplate"/>
                                <TemplateBinding  Property="ItemTemplate"/>
                            </MultiBinding>
                        </ContentPresenter.ContentTemplate>
                    </ContentPresenter>
                    <Border
                        x:Name="DropDownOverlay"
                        Grid.Column="2"
                        Width="30"
                        Margin="0,1,1,1"
                        HorizontalAlignment="Right"
                        Background="Transparent"
                        IsVisible="False" />
                    <Panel Grid.Column="2" Width="32" IsHitTestVisible="False">
                        <PathIcon
                            x:Name="DropDownGlyph"
                            Width="12"
                            Height="12"
                            Margin="0,0,10,0"
                            HorizontalAlignment="Right"
                            VerticalAlignment="Center"
                            Data="{DynamicResource ComboBoxIcon}"
                            Foreground="{DynamicResource ComboBoxIconDefaultForeground}"
                            UseLayoutRounding="False" />
                    </Panel>
                    <Popup 
                        Name="{x:Static iri:PartNames.PART_Popup}" 
                        Grid.Column="0" 
                        MinWidth="{Binding Bounds.Width, RelativeSource={RelativeSource TemplatedParent}}"
                        MinHeight="{TemplateBinding MaxDropDownHeight}"
                        ClipToBounds="False"
                        InheritsTransform="True"
                        PlacementTarget="Background"
                        WindowManagerAddShadowHint="False"
                        IsLightDismissEnabled="True" 
                        IsOpen="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}">
                        <Border 
                            Name="PopupBorder" 
                            Margin="0 4" 
                            Background="{DynamicResource ComboBoxPopupBackground}"
                            BorderBrush="{DynamicResource ComboBoxPopupBorderBrush}"
                            BoxShadow="{DynamicResource ComboBoxPopupBoxShadow}"
                            ClipToBounds="True"
                            CornerRadius="6"
                            >
                            <ScrollViewer>
                                <ItemsPresenter ItemsPanel="{TemplateBinding ItemsPanel}"/>
                            </ScrollViewer>
                        </Border>
                    </Popup>
                </Grid>
            </ControlTemplate>
        </Setter>
    </ControlTheme>
    
    <ControlTheme x:Key="{x:Type u:TreeComboBoxItem}" TargetType="u:TreeComboBoxItem">
        <Setter Property="Background" Value="{DynamicResource TreeViewItemDefaultBackground}"/>
        <Setter Property="Foreground" Value="{DynamicResource TreeViewItemDefaultForeground}"/>
        <Setter Property="CornerRadius" Value="3"/>
        <Setter Property="VerticalAlignment" Value="Center"/>
        <Setter Property="Template">
            <ControlTemplate TargetType="u:TreeComboBoxItem">
                <StackPanel>
                    <Border 
                        Name="PART_LayoutRoot" 
                        MinHeight="{TemplateBinding MinHeight}" 
                        Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}"
                        CornerRadius="{TemplateBinding CornerRadius}"
                        TemplatedControl.IsTemplateFocusTarget="True">
                        <Grid
                            Name="{x:Static iri:PartNames.PART_Header}"
                            Margin="{TemplateBinding Level, Mode=OneWay, Converter={StaticResource LeftMarginConverter}}" 
                              ColumnDefinitions="Auto, *">
                            <ToggleButton 
                                IsChecked="{TemplateBinding IsExpanded, Mode=TwoWay}" 
                                Theme="{DynamicResource ToggleButtonTreeViewItemIconButton}" 
                                Name="PART_ExpandCollapseChevron" 
                                Grid.Column="0" 
                                Padding="{DynamicResource TreeViewItemIconMargin}"
                                Focusable="False"></ToggleButton>
                            <ContentPresenter 
                                Grid.Column="1" 
                                Name="{x:Static iri:PartNames.PART_HeaderPresenter}"
                                Margin="{TemplateBinding Padding}"
                                Padding="{DynamicResource TreeViewItemPadding}"
                                HorizontalAlignment="{TemplateBinding HorizontalAlignment}"
                                VerticalAlignment="{TemplateBinding VerticalAlignment}"
                                Foreground="{TemplateBinding Foreground}"
                                Content="{TemplateBinding Header}" 
                                ContentTemplate="{TemplateBinding HeaderTemplate}" 
                                Focusable="False"/>
                        </Grid>
                    </Border>
                    <ItemsPresenter IsVisible="{TemplateBinding IsExpanded}" Name="{x:Static iri:PartNames.PART_ItemsPresenter}" ItemsPanel="{TemplateBinding ItemsPanel}"/>
                </StackPanel>
            </ControlTemplate>
        </Setter>
        
        <!--  Pointerover state  -->
        <Style Selector="^ /template/ Border#PART_LayoutRoot:pointerover">
            <Setter Property="Background" Value="{DynamicResource TreeViewItemPointeroverBackground}" />
        </Style>

        <!--  Pressed state  -->
        <Style Selector="^:pressed /template/ Border#PART_LayoutRoot:pointerover">
            <Setter Property="Background" Value="{DynamicResource TreeViewItemPressedBackground}" />
        </Style>

        <!--  Disabled state  -->
        <Style Selector="^:disabled /template/ Border#PART_LayoutRoot">
            <Setter Property="Background" Value="{DynamicResource TreeViewItemDisabledBackground}" />
        </Style>
        <Style Selector="^:disabled /template/ ContentPresenter#PART_HeaderPresenter">
            <Setter Property="Foreground" Value="{DynamicResource TreeViewItemDisabledForeground}" />
        </Style>

        <!--  Selected state  -->
        <Style Selector="^:selected /template/ Border#PART_LayoutRoot">
            <Setter Property="Background" Value="{DynamicResource TreeViewItemSelectedBackground}" />
        </Style>

        <!--  Disabled Selected state  -->
        <Style Selector="^:disabled:selected /template/ Border#PART_LayoutRoot">
            <Setter Property="Background" Value="{DynamicResource TreeViewItemSelectedDisabledBackground}" />
        </Style>

        <Style Selector="^:empty /template/ ToggleButton#PART_ExpandCollapseChevron">
            <Setter Property="Opacity" Value="0" />
            <Setter Property="IsHitTestVisible" Value="False" />
        </Style>
    </ControlTheme>
</ResourceDictionary>