sourcegit/src/Views/CommitMessageTextBox.axaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:c="using:SourceGit.Converters"
             xmlns:vm="using:SourceGit.ViewModels"
             xmlns:v="using:SourceGit.Views"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
             x:Class="SourceGit.Views.CommitMessageTextBox"
             x:Name="ThisControl">
  <Border Background="{DynamicResource Brush.Contents}"
          BorderThickness="1"
          BorderBrush="{DynamicResource Brush.Border2}"
          CornerRadius="4">
    <Grid RowDefinitions="Auto,1,*">
      <Grid Grid.Row="0" ColumnDefinitions="*,1,Auto">
        <v:EnhancedTextBox Grid.Column="0"
                           x:Name="SubjectEditor"
                           Classes="no_border"
                           Margin="0"
                           Padding="4"
                           CornerRadius="4,4,0,0"
                           BorderThickness="0"
                           Background="Transparent"
                           AcceptsReturn="False"
                           TextWrapping="Wrap"
                           ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                           ScrollViewer.VerticalScrollBarVisibility="Disabled"
                           Text="{Binding #ThisControl.Subject, Mode=TwoWay}"
                           Watermark="{DynamicResource Text.CommitMessageTextBox.SubjectPlaceholder}"
                           PreviewKeyDown="OnSubjectTextBoxPreviewKeyDown"/>

        <Rectangle Grid.Column="1"
                   Width="1"
                   HorizontalAlignment="Center"
                   VerticalAlignment="Stretch"
                   IsHitTestVisible="False"
                   Fill="{DynamicResource Brush.Border2}"/>
        
        <StackPanel Grid.Column="2"
                    Margin="8,0"
                    VerticalAlignment="Center"
                    Orientation="Horizontal">
          <TextBlock Classes="primary" Margin="2,0,0,0" FontSize="11" Text="{Binding #ThisControl.Subject.Length}" IsVisible="{Binding #ThisControl.Subject.Length, Converter={x:Static c:IntConverters.IsSubjectLengthGood}}"/>
          <TextBlock Classes="primary" Margin="2,0,0,0" FontSize="11" Foreground="DarkGoldenrod" Text="{Binding #ThisControl.Subject.Length}" IsVisible="{Binding #ThisControl.Subject.Length, Converter={x:Static c:IntConverters.IsSubjectLengthBad}}"/>
          <TextBlock Classes="primary" FontSize="11" Text="/"/>
          <TextBlock Classes="primary" FontSize="11" Text="{Binding Source={x:Static vm:Preference.Instance}, Path=SubjectGuideLength}"/>
          <Path Width="10" Height="10" Margin="4,0,0,0" Data="{StaticResource Icons.Error}" Fill="DarkGoldenrod" IsVisible="{Binding #ThisControl.Subject.Length, Converter={x:Static c:IntConverters.IsSubjectLengthBad}}"/>
        </StackPanel>
      </Grid>
      
      <Rectangle Grid.Row="1"
                 Height="1"
                 HorizontalAlignment="Stretch"
                 VerticalAlignment="Center"
                 IsHitTestVisible="False"
                 Fill="{DynamicResource Brush.Border2}"/>

      <v:EnhancedTextBox Grid.Row="2"
                         x:Name="DescriptionEditor"
                         Classes="no_border"
                         Margin="0"
                         Padding="4"
                         CornerRadius="0,0,4,4"
                         BorderThickness="0"
                         Background="Transparent"
                         VerticalContentAlignment="Top"
                         AcceptsReturn="True"
                         AcceptsTab="True"
                         TextWrapping="Wrap"
                         ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                         ScrollViewer.VerticalScrollBarVisibility="Auto"
                         Text="{Binding #ThisControl.Description, Mode=TwoWay}"
                         Watermark="{DynamicResource Text.CommitMessageTextBox.MessagePlaceholder}"
                         PreviewKeyDown="OnDescriptionTextBoxPreviewKeyDown"/>
    </Grid>
  </Border>
</UserControl>