sourcegit/src/Resources/Styles/TextBox.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:controls="clr-namespace:SourceGit.Views.Controls">
    <Style x:Key="Style.TextBox" TargetType="{x:Type TextBox}">
        <Setter Property="SnapsToDevicePixels" Value="True"/>
        <Setter Property="OverridesDefaultStyle" Value="True"/>
        <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
        <Setter Property="VerticalAlignment" Value="Center"/>
        <Setter Property="VerticalContentAlignment" Value="Center"/>
        <Setter Property="Foreground" Value="{DynamicResource Brush.FG1}"/>
        <Setter Property="CaretBrush" Value="{DynamicResource Brush.FG1}"/>
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="BorderBrush" Value="{DynamicResource Brush.Border1}"/>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="ContextMenu">
            <Setter.Value>
                <ContextMenu>
                    <MenuItem Command="ApplicationCommands.Copy" />
                    <MenuItem Command="ApplicationCommands.Cut" />
                    <MenuItem Command="ApplicationCommands.Paste" />
                </ContextMenu>
            </Setter.Value>
        </Setter>
        <Setter Property="Validation.ErrorTemplate">
            <Setter.Value>
                <ControlTemplate>
                    <AdornedElementPlaceholder x:Name="Target">
                        <Border x:Name="Border" BorderBrush="#FFDB000C" BorderThickness="1">
                            <Grid Background="Transparent" HorizontalAlignment="Right" VerticalAlignment="Top">
                                <Path Width="10" Height="10" Data="M 1,0 L8,0 L8,7 z" Fill="#FFDC000C"/>
                                <Popup x:Name="Tips" IsOpen="False" Placement="Right" VerticalOffset="-4" PlacementTarget="{Binding ElementName=Border}" AllowsTransparency="True">
                                    <Grid Background="Transparent" Height="32">
                                        <Border Background="#FFDB000C" Margin="4">
                                            <Border.Effect>
                                                <DropShadowEffect BlurRadius="4" ShadowDepth="0" Color="Black" Opacity=".8"/>
                                            </Border.Effect>
                                        </Border>
                                        <Border Margin="4">
                                            <TextBlock Foreground="White" Margin="12,0" VerticalAlignment="Center" Text="{Binding [0].ErrorContent}"/>
                                        </Border>
                                    </Grid>
                                </Popup>
                            </Grid>
                        </Border>
                    </AdornedElementPlaceholder>

                    <ControlTemplate.Triggers>
                        <MultiDataTrigger>
                            <MultiDataTrigger.Conditions>
                                <Condition Binding="{Binding ElementName=Target, Path=AdornedElement.IsKeyboardFocusWithin, Mode=OneWay}" Value="True" />
                                <Condition Binding="{Binding ElementName=Target, Path=AdornedElement.(Validation.HasError), Mode=OneWay}" Value="True" />
                            </MultiDataTrigger.Conditions>
                            <Setter TargetName="Tips" Property="IsOpen" Value="True"/>
                        </MultiDataTrigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TextBox}">
                    <Border 
                        x:Name="Border" 
                        Background="{TemplateBinding Background}"
                        SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
                        BorderThickness="{TemplateBinding BorderThickness}"
                        BorderBrush="{TemplateBinding BorderBrush}">
                        <ScrollViewer 
                            x:Name="PART_ContentHost"
                            Margin="{TemplateBinding Padding}"
                            VerticalAlignment="Center"
                            Background="Transparent"
                            BorderThickness="0"
                            IsTabStop="False"
                            RenderOptions.ClearTypeHint="Enabled"
                            CanContentScroll="True"
                            SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                    </Border>
                        
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="true">
                            <Setter TargetName="Border" Property="BorderBrush" Value="{DynamicResource Brush.Accent1}"/>
                        </Trigger>
                        <Trigger Property="AcceptsReturn" Value="True">
                            <Setter TargetName="PART_ContentHost" Property="VerticalAlignment" Value="Top"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource Style.TextBox}"/>
    <Style TargetType="{x:Type controls:TextEdit}" BasedOn="{StaticResource Style.TextBox}"/>
</ResourceDictionary>