App.xaml

<Application x:Class="CSharpWpfChatGPT.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:ui="http://schemas.modernwpf.com/2019">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ui:ThemeResources>
                    <ui:ThemeResources.ThemeDictionaries>
                        <ResourceDictionary x:Key="Light" ui:ThemeDictionary.Key="Light">
                            <SolidColorBrush x:Key="AppBackgroundBrush" Color="#FFF1F1F1" />
                            <SolidColorBrush x:Key="AppContentBackgroundBrush" Color="{StaticResource SystemAltHighColor}" />
                            <SolidColorBrush x:Key="CustomThemeBrush" Color="Red" />
                        </ResourceDictionary>
                    </ui:ThemeResources.ThemeDictionaries>
                </ui:ThemeResources>

                <ui:XamlControlsResources />
            </ResourceDictionary.MergedDictionaries>

            <Style TargetType="ui:ListView">
                <!--Avoid 'narrow' vertical scrollbar.-->
                <Setter Property="ui:ScrollViewerHelper.AutoHideScrollBars" Value="False" />
            </Style>
            <Style TargetType="TabItem" BasedOn="{StaticResource DefaultTabItemStyle}">
                <!--Note: FontFamily affect all under a tab. Got "Cascadia Mono Light" from comment section in https://www.youtube.com/watch?v=Hf9HQVPinqQ-->
                <Setter Property="FontFamily" Value="Consolas Light" />
                <Setter Property="FontSize" Value="18" />
                <Style.Triggers>
                    <Trigger Property="IsSelected" Value="True">
                        <Setter Property="FontWeight" Value="SemiBold" />
                        
                    </Trigger>
                    <Trigger Property="IsSelected" Value="False">
                        <Setter Property="FontWeight" Value="Normal" />
                        
                    </Trigger>
                </Style.Triggers>
            </Style>
        </ResourceDictionary>
    </Application.Resources>
</Application>