sourcegit/UI/DiffViewer.xaml

<UserControl x:Class="SourceGit.UI.DiffViewer"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             mc:Ignorable="d" 
             FontFamily="Consolas">
    <Border BorderThickness="1" BorderBrush="{StaticResource Brush.Border2}">
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="*"/>
            </Grid.RowDefinitions>

            <Border Grid.Row="0" BorderBrush="{StaticResource Brush.Border2}" BorderThickness="0,0,0,1">
                <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" Margin="0,4">
                    <StackPanel x:Name="orgFileNamePanel" Orientation="Horizontal">
                        <Path Width="10" Style="{StaticResource Style.Icon}" Data="{StaticResource Icon.File}"/>
                        <TextBlock x:Name="orgFileName" Margin="4,0,0,0" VerticalAlignment="Center" Foreground="{StaticResource Brush.FG}"/>
                        <TextBlock Margin="8,0" VerticalAlignment="Center" Text="→" Foreground="{StaticResource Brush.FG}"/>
                    </StackPanel>
                    <Path Width="10" Style="{StaticResource Style.Icon}" Data="{StaticResource Icon.File}"/>
                    <TextBlock x:Name="fileName" Margin="4,0" VerticalAlignment="Center" Foreground="{StaticResource Brush.FG}"/>
                </StackPanel>
            </Border>

            <Grid Grid.Row="1" ClipToBounds="True">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" MinWidth="100"/>
                    <ColumnDefinition Width="2"/>
                    <ColumnDefinition Width="*" MinWidth="100"/>
                </Grid.ColumnDefinitions>

                <Grid Grid.Column="0">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto"/>
                        <ColumnDefinition Width="1"/>
                        <ColumnDefinition Width="*"/>
                    </Grid.ColumnDefinitions>

                    <TextBox
                            x:Name="leftLineNumber"
                            Grid.Column="0"
                            AcceptsReturn="True"
                            AcceptsTab="True"
                            BorderThickness="0"
                            Background="Transparent"
                            IsReadOnly="True"
                            Margin="4,0,4,0"                   
                            FontSize="13"
                            HorizontalContentAlignment="Right"
                            VerticalAlignment="Stretch"/>

                    <Rectangle Grid.Column="1" Width="1" Fill="{StaticResource Brush.Border2}"/>

                    <RichTextBox
                            x:Name="leftText"
                            Grid.Column="2"
                            AcceptsReturn="True"
                            AcceptsTab="True"
                            IsReadOnly="True"
                            BorderThickness="0"
                            Background="Transparent"
                            Foreground="{StaticResource Brush.FG}"
                            Height="Auto"
                            FontSize="13"
                            HorizontalScrollBarVisibility="Auto"
                            VerticalScrollBarVisibility="Auto"
                            RenderOptions.ClearTypeHint="Enabled"
                            ScrollViewer.ScrollChanged="OnViewerScroll"
                            PreviewMouseWheel="OnViewerMouseWheel"
                            SizeChanged="LeftSizeChanged"
                            HorizontalAlignment="Stretch"
                            VerticalAlignment="Stretch">
                        <RichTextBox.Document>
                            <FlowDocument PageWidth="0"/>
                        </RichTextBox.Document>
                    </RichTextBox>
                </Grid>

                <GridSplitter Grid.Column="1" Width="1" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Background="{StaticResource Brush.Border2}"/>

                <Grid Grid.Column="2">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto"/>
                        <ColumnDefinition Width="1"/>
                        <ColumnDefinition Width="*"/>
                    </Grid.ColumnDefinitions>

                    <TextBox
                            x:Name="rightLineNumber"
                            Grid.Column="0"
                            AcceptsReturn="True"
                            AcceptsTab="True"
                            IsReadOnly="True"
                            BorderThickness="0"
                            Background="Transparent"
                            Margin="4,0,4,0"                   
                            FontSize="13"
                            HorizontalContentAlignment="Right"
                            VerticalAlignment="Stretch"/>

                    <Rectangle Grid.Column="1" Width="1" Fill="{StaticResource Brush.Border2}"/>

                    <RichTextBox
                            x:Name="rightText"
                            Grid.Column="2"
                            AcceptsReturn="True"
                            AcceptsTab="True"
                            IsReadOnly="True"
                            BorderThickness="0"
                            Background="Transparent"
                            Foreground="{StaticResource Brush.FG}"
                            Height="Auto"
                            FontSize="13"
                            HorizontalScrollBarVisibility="Auto"
                            VerticalScrollBarVisibility="Auto"
                            RenderOptions.ClearTypeHint="Enabled"
                            ScrollViewer.ScrollChanged="OnViewerScroll"
                            PreviewMouseWheel="OnViewerMouseWheel"
                            SizeChanged="RightSizeChanged"
                            HorizontalAlignment="Stretch"
                            VerticalAlignment="Stretch">
                        <RichTextBox.Document>
                            <FlowDocument PageWidth="0"/>
                        </RichTextBox.Document>
                    </RichTextBox>
                </Grid>
            </Grid>

            <Border x:Name="mask" Grid.RowSpan="2" Background="{StaticResource Brush.BG3}" Visibility="Collapsed">
                <StackPanel Orientation="Vertical" VerticalAlignment="Center" Opacity=".2">
                    <Path Width="64" Height="64" Style="{StaticResource Style.Icon}" Data="{StaticResource Icon.Diff}"/>
                    <Label Margin="0,8,0,0" Content="SELECT FILE TO VIEW CHANGES" FontSize="18" FontWeight="UltraBold" HorizontalAlignment="Center"/>
                </StackPanel>
            </Border>
        </Grid>
    </Border>
</UserControl>