MercuryConverter/UI/App.axaml

<Application xmlns="https://github.com/avaloniaui"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            x:Class="MercuryConverter.UI.App"
            xmlns:dialogHostAvalonia="clr-namespace:DialogHostAvalonia;assembly=DialogHost.Avalonia"
            RequestedThemeVariant="Default"> <!-- Dark Default Light -->

    <Application.Styles>
        <FluentTheme>
            <FluentTheme.Palettes>
                <ColorPaletteResources x:Key="Light" Accent="#ffb459c0" AltHigh="White" AltLow="White" AltMedium="White" AltMediumHigh="White" AltMediumLow="White" BaseHigh="Black" BaseLow="#ffa1aeff" BaseMedium="#ff5a71c0" BaseMediumHigh="#ff2b4996" BaseMediumLow="#ff435dab" ChromeAltLow="#ff2b4996" ChromeBlackHigh="Black" ChromeBlackLow="#ffa1aeff" ChromeBlackMedium="#ff2b4996" ChromeBlackMediumLow="#ff5a71c0" ChromeDisabledHigh="#ffa1aeff" ChromeDisabledLow="#ff5a71c0" ChromeGray="#ff435dab" ChromeHigh="#ffa1aeff" ChromeLow="#ffd9e1ff" ChromeMedium="#ffced7ff" ChromeMediumLow="#ffd9e1ff" ChromeWhite="White" ListLow="#ffced7ff" ListMedium="#ffa1aeff" RegionColor="#ffccdbff" />
                <ColorPaletteResources x:Key="Dark" Accent="#ff9b21dd" AltHigh="Black" AltLow="Black" AltMedium="Black" AltMediumHigh="Black" AltMediumLow="Black" BaseHigh="White" BaseLow="#ff3c2d94" BaseMedium="#ff9e96d2" BaseMediumHigh="#ffb7b0e1" BaseMediumLow="#ff6d61b3" ChromeAltLow="#ffb7b0e1" ChromeBlackHigh="Black" ChromeBlackLow="#ffb7b0e1" ChromeBlackMedium="Black" ChromeBlackMediumLow="Black" ChromeDisabledHigh="#ff3c2d94" ChromeDisabledLow="#ff9e96d2" ChromeGray="#ff867cc2" ChromeHigh="#ff867cc2" ChromeLow="#ff0c0f5e" ChromeMedium="#ff18166c" ChromeMediumLow="#ff302587" ChromeWhite="White" ListLow="#ff18166c" ListMedium="#ff3c2d94" RegionColor="#ff1c1f46" />
            </FluentTheme.Palettes>
            <Style Selector="DataGrid:focus DataGridCell:current /template/ Grid#FocusVisual"> 
                <Setter Property="IsVisible" Value="False" /> 
            </Style> 
        </FluentTheme>

        <StyleInclude Source="avares://Avalonia.Controls.DataGrid/Themes/Fluent.xaml"/>
        <dialogHostAvalonia:DialogHostStyles/>
        <StyleInclude Source="avares://AvaloniaProgressRing/Styles/ProgressRing.xaml"/>
    </Application.Styles>

    <Application.Resources>
        <ResourceDictionary>
            <!-- Theming -->
            <ResourceDictionary.ThemeDictionaries>
                <ResourceDictionary x:Key="Light">
                    <SolidColorBrush x:Key="ExpanderHeaderBackgroundPointerOver">#40FFFFFF</SolidColorBrush>
                    <SolidColorBrush x:Key="DataGridContentBackground">#40FFFFFF</SolidColorBrush>
                    <Bitmap x:Key="BannerBitmap">/Assets/imgs/banner_light.png</Bitmap>
                </ResourceDictionary>
                <ResourceDictionary x:Key="Dark">
                    <SolidColorBrush x:Key="ExpanderHeaderBackgroundPointerOver">#20000000</SolidColorBrush>
                    <SolidColorBrush x:Key="DataGridContentBackground">#ff000000</SolidColorBrush>
                    <SolidColorBrush x:Key="DialogHostOverlayBackgroundMixinBrush">#222244</SolidColorBrush>
                    <Bitmap x:Key="BannerBitmap">/Assets/imgs/banner_dark.png</Bitmap>
                </ResourceDictionary>
            </ResourceDictionary.ThemeDictionaries>
            <!-- Control Property Override -->
            <Thickness x:Key="TabItemMargin">12</Thickness>
            <!-- Control Override -->
            <ResourceDictionary.MergedDictionaries>
                <ResourceInclude Source="Overrides/Expander.axaml"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>